KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

26 files changed, 18965 insertions, 0 deletions

diff --git a/net/mptcp/Kconfig b/net/mptcp/Kconfig
new file mode 100644
index 000000000..be71fc9b4
--- /dev/null
+++ b/net/mptcp/Kconfig
@@ -0,0 +1,39 @@
+
+config MPTCP
+	bool "MPTCP: Multipath TCP"
+	depends on INET
+	select SKB_EXTENSIONS
+	select CRYPTO_LIB_SHA256
+	select CRYPTO_LIB_UTILS
+	help
+	  Multipath TCP (MPTCP) connections send and receive data over multiple
+	  subflows in order to utilize multiple network paths. Each subflow
+	  uses the TCP protocol, and TCP options carry header information for
+	  MPTCP.
+
+if MPTCP
+
+config INET_MPTCP_DIAG
+	depends on INET_DIAG
+	def_tristate INET_DIAG
+
+config MPTCP_IPV6
+	bool "MPTCP: IPv6 support for Multipath TCP"
+	depends on IPV6=y
+	default y
+
+config MPTCP_KUNIT_TEST
+	tristate "This builds the MPTCP KUnit tests" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  Currently covers the MPTCP crypto and token helpers.
+	  Only useful for kernel devs running KUnit test harness and are not
+	  for inclusion into a production build.
+
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
+
+endif
diff --git a/net/mptcp/Makefile b/net/mptcp/Makefile
new file mode 100644
index 000000000..89bf6c47c
--- /dev/null
+++ b/net/mptcp/Makefile
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_MPTCP) += mptcp.o
+
+mptcp-y := protocol.o subflow.o options.o token.o crypto.o ctrl.o pm.o diag.o \
+	   mib.o pm_netlink.o sockopt.o pm_userspace.o fastopen.o sched.o \
+	   mptcp_pm_gen.o pm_kernel.o
+
+obj-$(CONFIG_SYN_COOKIES) += syncookies.o
+obj-$(CONFIG_INET_MPTCP_DIAG) += mptcp_diag.o
+
+mptcp_crypto_test-objs := crypto_test.o
+mptcp_token_test-objs := token_test.o
+obj-$(CONFIG_MPTCP_KUNIT_TEST) += mptcp_crypto_test.o mptcp_token_test.o
+
+obj-$(CONFIG_BPF_SYSCALL) += bpf.o
diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
new file mode 100644
index 000000000..4cc16cbeb
--- /dev/null
+++ b/net/mptcp/bpf.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2020, Tessares SA.
+ * Copyright (c) 2022, SUSE.
+ *
+ * Author: Nicolas Rybowski <nicolas.rybowski@tessares.net>
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/bpf.h>
+#include "protocol.h"
+
+struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk)
+{
+	if (sk && sk_fullsock(sk) && sk_is_tcp(sk) && sk_is_mptcp(sk))
+		return mptcp_sk(mptcp_subflow_ctx(sk)->conn);
+
+	return NULL;
+}
+
+BTF_SET8_START(bpf_mptcp_fmodret_ids)
+BTF_ID_FLAGS(func, update_socket_protocol)
+BTF_SET8_END(bpf_mptcp_fmodret_ids)
+
+static const struct btf_kfunc_id_set bpf_mptcp_fmodret_set = {
+	.owner = THIS_MODULE,
+	.set   = &bpf_mptcp_fmodret_ids,
+};
+
+static int __init bpf_mptcp_kfunc_init(void)
+{
+	return register_btf_fmodret_id_set(&bpf_mptcp_fmodret_set);
+}
+late_initcall(bpf_mptcp_kfunc_init);
diff --git a/net/mptcp/crypto.c b/net/mptcp/crypto.c
new file mode 100644
index 000000000..31948e18d
--- /dev/null
+++ b/net/mptcp/crypto.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP cryptographic functions
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ *
+ * Note: This code is based on mptcp_ctrl.c, mptcp_ipv4.c, and
+ *       mptcp_ipv6 from multipath-tcp.org, authored by:
+ *
+ *       Sébastien Barré <sebastien.barre@uclouvain.be>
+ *       Christoph Paasch <christoph.paasch@uclouvain.be>
+ *       Jaakko Korkeaniemi <jaakko.korkeaniemi@aalto.fi>
+ *       Gregory Detal <gregory.detal@uclouvain.be>
+ *       Fabien Duchêne <fabien.duchene@uclouvain.be>
+ *       Andreas Seelinger <Andreas.Seelinger@rwth-aachen.de>
+ *       Lavkesh Lahngir <lavkesh51@gmail.com>
+ *       Andreas Ripke <ripke@neclab.eu>
+ *       Vlad Dogaru <vlad.dogaru@intel.com>
+ *       Octavian Purdila <octavian.purdila@intel.com>
+ *       John Ronan <jronan@tssg.org>
+ *       Catalin Nicutar <catalin.nicutar@gmail.com>
+ *       Brandon Heller <brandonh@stanford.edu>
+ */
+
+#include <linux/kernel.h>
+#include <crypto/sha2.h>
+
+#include "protocol.h"
+
+#define SHA256_DIGEST_WORDS (SHA256_DIGEST_SIZE / 4)
+
+void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn)
+{
+	__be32 mptcp_hashed_key[SHA256_DIGEST_WORDS];
+	__be64 input = cpu_to_be64(key);
+
+	sha256((__force u8 *)&input, sizeof(input), (u8 *)mptcp_hashed_key);
+
+	if (token)
+		*token = be32_to_cpu(mptcp_hashed_key[0]);
+	if (idsn)
+		*idsn = be64_to_cpu(*((__be64 *)&mptcp_hashed_key[6]));
+}
+
+void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac)
+{
+	__be64 key[2] = { cpu_to_be64(key1), cpu_to_be64(key2) };
+
+	hmac_sha256_usingrawkey((const u8 *)key, sizeof(key), msg, len, hmac);
+}
+
+#if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
+EXPORT_SYMBOL_GPL(mptcp_crypto_hmac_sha);
+#endif
diff --git a/net/mptcp/crypto_test.c b/net/mptcp/crypto_test.c
new file mode 100644
index 000000000..220414e5c
--- /dev/null
+++ b/net/mptcp/crypto_test.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <kunit/test.h>
+
+#include "protocol.h"
+
+struct test_case {
+	char *key;
+	char *msg;
+	char *result;
+};
+
+/* we can't reuse RFC 4231 test vectors, as we have constraint on the
+ * input and key size.
+ */
+static struct test_case tests[] = {
+	{
+		.key = "0b0b0b0b0b0b0b0b",
+		.msg = "48692054",
+		.result = "8385e24fb4235ac37556b6b886db106284a1da671699f46db1f235ec622dcafa",
+	},
+	{
+		.key = "aaaaaaaaaaaaaaaa",
+		.msg = "dddddddd",
+		.result = "2c5e219164ff1dca1c4a92318d847bb6b9d44492984e1eb71aff9022f71046e9",
+	},
+	{
+		.key = "0102030405060708",
+		.msg = "cdcdcdcd",
+		.result = "e73b9ba9969969cefb04aa0d6df18ec2fcc075b6f23b4d8c4da736a5dbbc6e7d",
+	},
+};
+
+static void mptcp_crypto_test_basic(struct kunit *test)
+{
+	char hmac[32], hmac_hex[65];
+	u32 nonce1, nonce2;
+	u64 key1, key2;
+	u8 msg[8];
+	int i, j;
+
+	for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+		/* mptcp hmap will convert to be before computing the hmac */
+		key1 = be64_to_cpu(*((__be64 *)&tests[i].key[0]));
+		key2 = be64_to_cpu(*((__be64 *)&tests[i].key[8]));
+		nonce1 = be32_to_cpu(*((__be32 *)&tests[i].msg[0]));
+		nonce2 = be32_to_cpu(*((__be32 *)&tests[i].msg[4]));
+
+		put_unaligned_be32(nonce1, &msg[0]);
+		put_unaligned_be32(nonce2, &msg[4]);
+
+		mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
+		for (j = 0; j < 32; ++j)
+			sprintf(&hmac_hex[j << 1], "%02x", hmac[j] & 0xff);
+		hmac_hex[64] = 0;
+
+		KUNIT_EXPECT_STREQ(test, &hmac_hex[0], tests[i].result);
+	}
+}
+
+static struct kunit_case mptcp_crypto_test_cases[] = {
+	KUNIT_CASE(mptcp_crypto_test_basic),
+	{}
+};
+
+static struct kunit_suite mptcp_crypto_suite = {
+	.name = "mptcp-crypto",
+	.test_cases = mptcp_crypto_test_cases,
+};
+
+kunit_test_suite(mptcp_crypto_suite);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("KUnit tests for MPTCP Crypto");
diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c
new file mode 100644
index 000000000..63c5747f0
--- /dev/null
+++ b/net/mptcp/ctrl.c
@@ -0,0 +1,605 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2019, Tessares SA.
+ */
+
+#ifdef CONFIG_SYSCTL
+#include <linux/sysctl.h>
+#endif
+
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#include "protocol.h"
+#include "mib.h"
+
+#define MPTCP_SYSCTL_PATH "net/mptcp"
+
+static int mptcp_pernet_id;
+
+#ifdef CONFIG_SYSCTL
+static int mptcp_pm_type_max = __MPTCP_PM_TYPE_MAX;
+#endif
+
+struct mptcp_pernet {
+#ifdef CONFIG_SYSCTL
+	struct ctl_table_header *ctl_table_hdr;
+#endif
+
+	unsigned int add_addr_timeout;
+	unsigned int blackhole_timeout;
+	unsigned int close_timeout;
+	unsigned int stale_loss_cnt;
+	atomic_t active_disable_times;
+	unsigned long active_disable_stamp;
+	u8 syn_retrans_before_tcp_fallback;
+	u8 mptcp_enabled;
+	u8 checksum_enabled;
+	u8 allow_join_initial_addr_port;
+	u8 pm_type;
+	u8 add_addr_v6_port_drop_ts;
+	char scheduler[MPTCP_SCHED_NAME_MAX];
+	char path_manager[MPTCP_PM_NAME_MAX];
+};
+
+static struct mptcp_pernet *mptcp_get_pernet(const struct net *net)
+{
+	return net_generic(net, mptcp_pernet_id);
+}
+
+int mptcp_is_enabled(const struct net *net)
+{
+	return mptcp_get_pernet(net)->mptcp_enabled;
+}
+
+unsigned int mptcp_get_add_addr_timeout(const struct net *net)
+{
+	return mptcp_get_pernet(net)->add_addr_timeout;
+}
+
+int mptcp_is_checksum_enabled(const struct net *net)
+{
+	return mptcp_get_pernet(net)->checksum_enabled;
+}
+
+int mptcp_allow_join_id0(const struct net *net)
+{
+	return mptcp_get_pernet(net)->allow_join_initial_addr_port;
+}
+
+unsigned int mptcp_stale_loss_cnt(const struct net *net)
+{
+	return mptcp_get_pernet(net)->stale_loss_cnt;
+}
+
+unsigned int mptcp_close_timeout(const struct sock *sk)
+{
+	if (sock_flag(sk, SOCK_DEAD))
+		return TCP_TIMEWAIT_LEN;
+	return mptcp_get_pernet(sock_net(sk))->close_timeout;
+}
+
+int mptcp_get_pm_type(const struct net *net)
+{
+	return mptcp_get_pernet(net)->pm_type;
+}
+
+const char *mptcp_get_path_manager(const struct net *net)
+{
+	return mptcp_get_pernet(net)->path_manager;
+}
+
+const char *mptcp_get_scheduler(const struct net *net)
+{
+	return mptcp_get_pernet(net)->scheduler;
+}
+
+unsigned int mptcp_add_addr_v6_port_drop_ts(const struct net *net)
+{
+	return READ_ONCE(mptcp_get_pernet(net)->add_addr_v6_port_drop_ts);
+}
+
+static void mptcp_pernet_set_defaults(struct mptcp_pernet *pernet)
+{
+	pernet->mptcp_enabled = 1;
+	pernet->add_addr_timeout = TCP_RTO_MAX;
+	pernet->blackhole_timeout = 3600;
+	pernet->syn_retrans_before_tcp_fallback = 2;
+	atomic_set(&pernet->active_disable_times, 0);
+	pernet->close_timeout = TCP_TIMEWAIT_LEN;
+	pernet->checksum_enabled = 0;
+	pernet->allow_join_initial_addr_port = 1;
+	pernet->stale_loss_cnt = 4;
+	pernet->pm_type = MPTCP_PM_TYPE_KERNEL;
+	strscpy(pernet->scheduler, "default", sizeof(pernet->scheduler));
+	strscpy(pernet->path_manager, "kernel", sizeof(pernet->path_manager));
+	pernet->add_addr_v6_port_drop_ts = 1;
+}
+
+#ifdef CONFIG_SYSCTL
+static int mptcp_set_scheduler(char *scheduler, const char *name)
+{
+	struct mptcp_sched_ops *sched;
+	int ret = 0;
+
+	rcu_read_lock();
+	sched = mptcp_sched_find(name);
+	if (sched)
+		strscpy(scheduler, name, MPTCP_SCHED_NAME_MAX);
+	else
+		ret = -ENOENT;
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static int proc_scheduler(const struct ctl_table *ctl, int write,
+			  void *buffer, size_t *lenp, loff_t *ppos)
+{
+	char (*scheduler)[MPTCP_SCHED_NAME_MAX] = ctl->data;
+	char val[MPTCP_SCHED_NAME_MAX];
+	struct ctl_table tbl = {
+		.data = val,
+		.maxlen = MPTCP_SCHED_NAME_MAX,
+	};
+	int ret;
+
+	strscpy(val, *scheduler, MPTCP_SCHED_NAME_MAX);
+
+	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+	if (write && ret == 0)
+		ret = mptcp_set_scheduler(*scheduler, val);
+
+	return ret;
+}
+
+static int proc_available_schedulers(const struct ctl_table *ctl,
+				     int write, void *buffer,
+				     size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table tbl = { .maxlen = MPTCP_SCHED_BUF_MAX, };
+	int ret;
+
+	tbl.data = kmalloc(tbl.maxlen, GFP_USER);
+	if (!tbl.data)
+		return -ENOMEM;
+
+	mptcp_get_available_schedulers(tbl.data, MPTCP_SCHED_BUF_MAX);
+	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+	kfree(tbl.data);
+
+	return ret;
+}
+
+static int proc_blackhole_detect_timeout(const struct ctl_table *table,
+					 int write, void *buffer, size_t *lenp,
+					 loff_t *ppos)
+{
+	struct mptcp_pernet *pernet = container_of(table->data,
+						   struct mptcp_pernet,
+						   blackhole_timeout);
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+	if (write && ret == 0)
+		atomic_set(&pernet->active_disable_times, 0);
+
+	return ret;
+}
+
+static int mptcp_set_path_manager(char *path_manager, const char *name)
+{
+	struct mptcp_pm_ops *pm_ops;
+	int ret = 0;
+
+	rcu_read_lock();
+	pm_ops = mptcp_pm_find(name);
+	if (pm_ops)
+		strscpy(path_manager, name, MPTCP_PM_NAME_MAX);
+	else
+		ret = -ENOENT;
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static int proc_path_manager(const struct ctl_table *ctl, int write,
+			     void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct mptcp_pernet *pernet = container_of(ctl->data,
+						   struct mptcp_pernet,
+						   path_manager);
+	char (*path_manager)[MPTCP_PM_NAME_MAX] = ctl->data;
+	char pm_name[MPTCP_PM_NAME_MAX];
+	const struct ctl_table tbl = {
+		.data = pm_name,
+		.maxlen = MPTCP_PM_NAME_MAX,
+	};
+	int ret;
+
+	strscpy(pm_name, *path_manager, MPTCP_PM_NAME_MAX);
+
+	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+	if (write && ret == 0) {
+		ret = mptcp_set_path_manager(*path_manager, pm_name);
+		if (ret == 0) {
+			u8 pm_type = __MPTCP_PM_TYPE_NR;
+
+			if (strncmp(pm_name, "kernel", MPTCP_PM_NAME_MAX) == 0)
+				pm_type = MPTCP_PM_TYPE_KERNEL;
+			else if (strncmp(pm_name, "userspace", MPTCP_PM_NAME_MAX) == 0)
+				pm_type = MPTCP_PM_TYPE_USERSPACE;
+			pernet->pm_type = pm_type;
+		}
+	}
+
+	return ret;
+}
+
+static int proc_pm_type(const struct ctl_table *ctl, int write,
+			void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct mptcp_pernet *pernet = container_of(ctl->data,
+						   struct mptcp_pernet,
+						   pm_type);
+	int ret;
+
+	ret = proc_dou8vec_minmax(ctl, write, buffer, lenp, ppos);
+	if (write && ret == 0) {
+		u8 pm_type = READ_ONCE(*(u8 *)ctl->data);
+		char *pm_name = "";
+
+		if (pm_type == MPTCP_PM_TYPE_KERNEL)
+			pm_name = "kernel";
+		else if (pm_type == MPTCP_PM_TYPE_USERSPACE)
+			pm_name = "userspace";
+		mptcp_set_path_manager(pernet->path_manager, pm_name);
+	}
+
+	return ret;
+}
+
+static int proc_available_path_managers(const struct ctl_table *ctl,
+					int write, void *buffer,
+					size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table tbl = { .maxlen = MPTCP_PM_BUF_MAX, };
+	int ret;
+
+	tbl.data = kmalloc(tbl.maxlen, GFP_USER);
+	if (!tbl.data)
+		return -ENOMEM;
+
+	mptcp_pm_get_available(tbl.data, MPTCP_PM_BUF_MAX);
+	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+	kfree(tbl.data);
+
+	return ret;
+}
+
+static struct ctl_table mptcp_sysctl_table[] = {
+	{
+		.procname = "enabled",
+		.maxlen = sizeof(u8),
+		.mode = 0644,
+		/* users with CAP_NET_ADMIN or root (not and) can change this
+		 * value, same as other sysctl or the 'net' tree.
+		 */
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1       = SYSCTL_ZERO,
+		.extra2       = SYSCTL_ONE
+	},
+	{
+		.procname = "add_addr_timeout",
+		.maxlen = sizeof(unsigned int),
+		.mode = 0644,
+		.proc_handler = proc_dointvec_jiffies,
+	},
+	{
+		.procname = "checksum_enabled",
+		.maxlen = sizeof(u8),
+		.mode = 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1       = SYSCTL_ZERO,
+		.extra2       = SYSCTL_ONE
+	},
+	{
+		.procname = "allow_join_initial_addr_port",
+		.maxlen = sizeof(u8),
+		.mode = 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1       = SYSCTL_ZERO,
+		.extra2       = SYSCTL_ONE
+	},
+	{
+		.procname = "stale_loss_cnt",
+		.maxlen = sizeof(unsigned int),
+		.mode = 0644,
+		.proc_handler = proc_douintvec_minmax,
+	},
+	{
+		.procname = "pm_type",
+		.maxlen = sizeof(u8),
+		.mode = 0644,
+		.proc_handler = proc_pm_type,
+		.extra1       = SYSCTL_ZERO,
+		.extra2       = &mptcp_pm_type_max
+	},
+	{
+		.procname = "scheduler",
+		.maxlen	= MPTCP_SCHED_NAME_MAX,
+		.mode = 0644,
+		.proc_handler = proc_scheduler,
+	},
+	{
+		.procname = "available_schedulers",
+		.maxlen	= MPTCP_SCHED_BUF_MAX,
+		.mode = 0444,
+		.proc_handler = proc_available_schedulers,
+	},
+	{
+		.procname = "close_timeout",
+		.maxlen = sizeof(unsigned int),
+		.mode = 0644,
+		.proc_handler = proc_dointvec_jiffies,
+	},
+	{
+		.procname = "blackhole_timeout",
+		.maxlen = sizeof(unsigned int),
+		.mode = 0644,
+		.proc_handler = proc_blackhole_detect_timeout,
+		.extra1 = SYSCTL_ZERO,
+	},
+	{
+		.procname = "syn_retrans_before_tcp_fallback",
+		.maxlen = sizeof(u8),
+		.mode = 0644,
+		.proc_handler = proc_dou8vec_minmax,
+	},
+	{
+		.procname = "path_manager",
+		.maxlen	= MPTCP_PM_NAME_MAX,
+		.mode = 0644,
+		.proc_handler = proc_path_manager,
+	},
+	{
+		.procname = "available_path_managers",
+		.maxlen	= MPTCP_PM_BUF_MAX,
+		.mode = 0444,
+		.proc_handler = proc_available_path_managers,
+	},
+	{
+		.procname = "add_addr_v6_port_drop_ts",
+		.maxlen = sizeof(u8),
+		.mode = 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1       = SYSCTL_ZERO,
+		.extra2       = SYSCTL_ONE
+	},
+};
+
+static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
+{
+	struct ctl_table_header *hdr;
+	struct ctl_table *table;
+
+	table = mptcp_sysctl_table;
+	if (!net_eq(net, &init_net)) {
+		table = kmemdup(table, sizeof(mptcp_sysctl_table), GFP_KERNEL);
+		if (!table)
+			goto err_alloc;
+	}
+
+	table[0].data = &pernet->mptcp_enabled;
+	table[1].data = &pernet->add_addr_timeout;
+	table[2].data = &pernet->checksum_enabled;
+	table[3].data = &pernet->allow_join_initial_addr_port;
+	table[4].data = &pernet->stale_loss_cnt;
+	table[5].data = &pernet->pm_type;
+	table[6].data = &pernet->scheduler;
+	/* table[7] is for available_schedulers which is read-only info */
+	table[8].data = &pernet->close_timeout;
+	table[9].data = &pernet->blackhole_timeout;
+	table[10].data = &pernet->syn_retrans_before_tcp_fallback;
+	table[11].data = &pernet->path_manager;
+	/* table[12] is for available_path_managers which is read-only info */
+	table[13].data = &pernet->add_addr_v6_port_drop_ts;
+
+	hdr = register_net_sysctl_sz(net, MPTCP_SYSCTL_PATH, table,
+				     ARRAY_SIZE(mptcp_sysctl_table));
+	if (!hdr)
+		goto err_reg;
+
+	pernet->ctl_table_hdr = hdr;
+
+	return 0;
+
+err_reg:
+	if (!net_eq(net, &init_net))
+		kfree(table);
+err_alloc:
+	return -ENOMEM;
+}
+
+static void mptcp_pernet_del_table(struct mptcp_pernet *pernet)
+{
+	const struct ctl_table *table = pernet->ctl_table_hdr->ctl_table_arg;
+
+	unregister_net_sysctl_table(pernet->ctl_table_hdr);
+
+	kfree(table);
+}
+
+#else
+
+static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
+{
+	return 0;
+}
+
+static void mptcp_pernet_del_table(struct mptcp_pernet *pernet) {}
+
+#endif /* CONFIG_SYSCTL */
+
+/* The following code block is to deal with middle box issues with MPTCP,
+ * similar to what is done with TFO.
+ * The proposed solution is to disable active MPTCP globally when SYN+MPC are
+ * dropped, while SYN without MPC aren't. In this case, active side MPTCP is
+ * disabled globally for 1hr at first. Then if it happens again, it is disabled
+ * for 2h, then 4h, 8h, ...
+ * The timeout is reset back to 1hr when a successful active MPTCP connection is
+ * fully established.
+ */
+
+/* Disable active MPTCP and record current jiffies and active_disable_times */
+void mptcp_active_disable(struct sock *sk)
+{
+	struct net *net = sock_net(sk);
+	struct mptcp_pernet *pernet;
+
+	pernet = mptcp_get_pernet(net);
+
+	if (!READ_ONCE(pernet->blackhole_timeout))
+		return;
+
+	/* Paired with READ_ONCE() in mptcp_active_should_disable() */
+	WRITE_ONCE(pernet->active_disable_stamp, jiffies);
+
+	/* Paired with smp_rmb() in mptcp_active_should_disable().
+	 * We want pernet->active_disable_stamp to be updated first.
+	 */
+	smp_mb__before_atomic();
+	atomic_inc(&pernet->active_disable_times);
+
+	MPTCP_INC_STATS(net, MPTCP_MIB_BLACKHOLE);
+}
+
+/* Calculate timeout for MPTCP active disable
+ * Return true if we are still in the active MPTCP disable period
+ * Return false if timeout already expired and we should use active MPTCP
+ */
+bool mptcp_active_should_disable(struct sock *ssk)
+{
+	struct net *net = sock_net(ssk);
+	unsigned int blackhole_timeout;
+	struct mptcp_pernet *pernet;
+	unsigned long timeout;
+	int disable_times;
+	int multiplier;
+
+	pernet = mptcp_get_pernet(net);
+	blackhole_timeout = READ_ONCE(pernet->blackhole_timeout);
+
+	if (!blackhole_timeout)
+		return false;
+
+	disable_times = atomic_read(&pernet->active_disable_times);
+	if (!disable_times)
+		return false;
+
+	/* Paired with smp_mb__before_atomic() in mptcp_active_disable() */
+	smp_rmb();
+
+	/* Limit timeout to max: 2^6 * initial timeout */
+	multiplier = 1 << min(disable_times - 1, 6);
+
+	/* Paired with the WRITE_ONCE() in mptcp_active_disable(). */
+	timeout = READ_ONCE(pernet->active_disable_stamp) +
+		  multiplier * blackhole_timeout * HZ;
+
+	return time_before(jiffies, timeout);
+}
+
+/* Enable active MPTCP and reset active_disable_times if needed */
+void mptcp_active_enable(struct sock *sk)
+{
+	struct mptcp_pernet *pernet = mptcp_get_pernet(sock_net(sk));
+
+	if (atomic_read(&pernet->active_disable_times)) {
+		struct net_device *dev;
+		struct dst_entry *dst;
+
+		rcu_read_lock();
+		dst = __sk_dst_get(sk);
+		dev = dst ? dst_dev_rcu(dst) : NULL;
+		if (!(dev && (dev->flags & IFF_LOOPBACK)))
+			atomic_set(&pernet->active_disable_times, 0);
+		rcu_read_unlock();
+	}
+}
+
+/* Check the number of retransmissions, and fallback to TCP if needed */
+void mptcp_active_detect_blackhole(struct sock *ssk, bool expired)
+{
+	struct mptcp_subflow_context *subflow;
+	u8 timeouts, to_max;
+	struct net *net;
+
+	/* Only check MPTCP SYN ... */
+	if (likely(!sk_is_mptcp(ssk) || ssk->sk_state != TCP_SYN_SENT))
+		return;
+
+	subflow = mptcp_subflow_ctx(ssk);
+
+	/* ... + MP_CAPABLE */
+	if (!subflow->request_mptcp) {
+		/* Mark as blackhole iif the 1st non-MPTCP SYN is accepted */
+		subflow->mpc_drop = 0;
+		return;
+	}
+
+	net = sock_net(ssk);
+	timeouts = inet_csk(ssk)->icsk_retransmits;
+	to_max = mptcp_get_pernet(net)->syn_retrans_before_tcp_fallback;
+
+	if (timeouts == to_max || (timeouts < to_max && expired)) {
+		subflow->mpc_drop = 1;
+		mptcp_early_fallback(mptcp_sk(subflow->conn), subflow,
+				     MPTCP_MIB_MPCAPABLEACTIVEDROP);
+	}
+}
+
+static int __net_init mptcp_net_init(struct net *net)
+{
+	struct mptcp_pernet *pernet = mptcp_get_pernet(net);
+
+	mptcp_pernet_set_defaults(pernet);
+
+	return mptcp_pernet_new_table(net, pernet);
+}
+
+/* Note: the callback will only be called per extra netns */
+static void __net_exit mptcp_net_exit(struct net *net)
+{
+	struct mptcp_pernet *pernet = mptcp_get_pernet(net);
+
+	mptcp_pernet_del_table(pernet);
+}
+
+static struct pernet_operations mptcp_pernet_ops = {
+	.init = mptcp_net_init,
+	.exit = mptcp_net_exit,
+	.id = &mptcp_pernet_id,
+	.size = sizeof(struct mptcp_pernet),
+};
+
+void __init mptcp_init(void)
+{
+	mptcp_join_cookie_init();
+	mptcp_proto_init();
+
+	if (register_pernet_subsys(&mptcp_pernet_ops) < 0)
+		panic("Failed to register MPTCP pernet subsystem.\n");
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+int __init mptcpv6_init(void)
+{
+	int err;
+
+	err = mptcp_proto_v6_init();
+
+	return err;
+}
+#endif
diff --git a/net/mptcp/diag.c b/net/mptcp/diag.c
new file mode 100644
index 000000000..70cf9ebce
--- /dev/null
+++ b/net/mptcp/diag.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+/* MPTCP socket monitoring support
+ *
+ * Copyright (c) 2019 Red Hat
+ *
+ * Author: Davide Caratti <dcaratti@redhat.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/net.h>
+#include <linux/inet_diag.h>
+#include <net/netlink.h>
+#include "protocol.h"
+
+static int subflow_get_info(struct sock *sk, struct sk_buff *skb, bool net_admin)
+{
+	struct mptcp_subflow_context *sf;
+	struct nlattr *start;
+	u32 flags = 0;
+	bool slow;
+	int err;
+
+	if (inet_sk_state_load(sk) == TCP_LISTEN)
+		return 0;
+
+	start = nla_nest_start_noflag(skb, INET_ULP_INFO_MPTCP);
+	if (!start)
+		return -EMSGSIZE;
+
+	slow = lock_sock_fast(sk);
+	rcu_read_lock();
+	sf = rcu_dereference(inet_csk(sk)->icsk_ulp_data);
+	if (!sf) {
+		err = 0;
+		goto nla_failure;
+	}
+
+	if (sf->mp_capable)
+		flags |= MPTCP_SUBFLOW_FLAG_MCAP_REM;
+	if (sf->request_mptcp)
+		flags |= MPTCP_SUBFLOW_FLAG_MCAP_LOC;
+	if (sf->mp_join)
+		flags |= MPTCP_SUBFLOW_FLAG_JOIN_REM;
+	if (sf->request_join)
+		flags |= MPTCP_SUBFLOW_FLAG_JOIN_LOC;
+	if (sf->backup)
+		flags |= MPTCP_SUBFLOW_FLAG_BKUP_REM;
+	if (sf->request_bkup)
+		flags |= MPTCP_SUBFLOW_FLAG_BKUP_LOC;
+	if (READ_ONCE(sf->fully_established))
+		flags |= MPTCP_SUBFLOW_FLAG_FULLY_ESTABLISHED;
+	if (sf->conn_finished)
+		flags |= MPTCP_SUBFLOW_FLAG_CONNECTED;
+	if (sf->map_valid)
+		flags |= MPTCP_SUBFLOW_FLAG_MAPVALID;
+
+	if (nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_TOKEN_REM, sf->remote_token) ||
+	    nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_TOKEN_LOC, sf->token) ||
+	    nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_FLAGS, flags) ||
+	    nla_put_u8(skb, MPTCP_SUBFLOW_ATTR_ID_REM, sf->remote_id) ||
+	    nla_put_u8(skb, MPTCP_SUBFLOW_ATTR_ID_LOC, subflow_get_local_id(sf))) {
+		err = -EMSGSIZE;
+		goto nla_failure;
+	}
+
+	/* Only export seq related counters to user with CAP_NET_ADMIN */
+	if (net_admin &&
+	    (nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_RELWRITE_SEQ,
+			 sf->rel_write_seq) ||
+	     nla_put_u64_64bit(skb, MPTCP_SUBFLOW_ATTR_MAP_SEQ, sf->map_seq,
+			       MPTCP_SUBFLOW_ATTR_PAD) ||
+	     nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_MAP_SFSEQ,
+			 sf->map_subflow_seq) ||
+	     nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_SSN_OFFSET, sf->ssn_offset) ||
+	     nla_put_u16(skb, MPTCP_SUBFLOW_ATTR_MAP_DATALEN,
+			 sf->map_data_len))) {
+		err = -EMSGSIZE;
+		goto nla_failure;
+	}
+
+	rcu_read_unlock();
+	unlock_sock_fast(sk, slow);
+	nla_nest_end(skb, start);
+	return 0;
+
+nla_failure:
+	rcu_read_unlock();
+	unlock_sock_fast(sk, slow);
+	nla_nest_cancel(skb, start);
+	return err;
+}
+
+static size_t subflow_get_info_size(const struct sock *sk, bool net_admin)
+{
+	size_t size = 0;
+
+	size += nla_total_size(0) +	/* INET_ULP_INFO_MPTCP */
+		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_TOKEN_REM */
+		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_TOKEN_LOC */
+		nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_FLAGS */
+		nla_total_size(1) +	/* MPTCP_SUBFLOW_ATTR_ID_REM */
+		nla_total_size(1) +	/* MPTCP_SUBFLOW_ATTR_ID_LOC */
+		0;
+
+	if (net_admin)
+		size += nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_RELWRITE_SEQ */
+			nla_total_size_64bit(8) +	/* MPTCP_SUBFLOW_ATTR_MAP_SEQ */
+			nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_MAP_SFSEQ */
+			nla_total_size(4) +	/* MPTCP_SUBFLOW_ATTR_SSN_OFFSET */
+			nla_total_size(2) +	/* MPTCP_SUBFLOW_ATTR_MAP_DATALEN */
+			0;
+
+	return size;
+}
+
+void mptcp_diag_subflow_init(struct tcp_ulp_ops *ops)
+{
+	ops->get_info = subflow_get_info;
+	ops->get_info_size = subflow_get_info_size;
+}
diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c
new file mode 100644
index 000000000..f71775090
--- /dev/null
+++ b/net/mptcp/fastopen.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0
+/* MPTCP Fast Open Mechanism
+ *
+ * Copyright (c) 2021-2022, Dmytro SHYTYI
+ */
+
+#include "protocol.h"
+
+void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subflow,
+					      struct request_sock *req)
+{
+	struct sock *sk, *ssk;
+	struct sk_buff *skb;
+	struct tcp_sock *tp;
+	bool has_rxtstamp;
+
+	/* on early fallback the subflow context is deleted by
+	 * subflow_syn_recv_sock()
+	 */
+	if (!subflow)
+		return;
+
+	ssk = subflow->tcp_sock;
+	sk = subflow->conn;
+	tp = tcp_sk(ssk);
+
+	/* A valid TFO cookie does not guarantee SYN data. */
+	skb = skb_peek(&ssk->sk_receive_queue);
+	if (!skb)
+		return;
+
+	subflow->is_mptfo = 1;
+
+	/* dequeue the skb from sk receive queue */
+	__skb_unlink(skb, &ssk->sk_receive_queue);
+	skb_ext_reset(skb);
+
+	mptcp_subflow_lend_fwdmem(subflow, skb);
+
+	/* We copy the fastopen data, but that don't belong to the mptcp sequence
+	 * space, need to offset it in the subflow sequence, see mptcp_subflow_get_map_offset()
+	 */
+	tp->copied_seq += skb->len;
+	subflow->ssn_offset += skb->len;
+	has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp;
+
+	/* Only the sequence delta is relevant */
+	MPTCP_SKB_CB(skb)->map_seq = -skb->len;
+	MPTCP_SKB_CB(skb)->end_seq = 0;
+	MPTCP_SKB_CB(skb)->offset = 0;
+	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
+	MPTCP_SKB_CB(skb)->cant_coalesce = 1;
+
+	mptcp_data_lock(sk);
+	DEBUG_NET_WARN_ON_ONCE(sock_owned_by_user_nocheck(sk));
+
+	mptcp_borrow_fwdmem(sk, skb);
+	skb_set_owner_r(skb, sk);
+	__skb_queue_tail(&sk->sk_receive_queue, skb);
+	mptcp_sk(sk)->bytes_received += skb->len;
+
+	sk->sk_data_ready(sk);
+
+	mptcp_data_unlock(sk);
+}
diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c
new file mode 100644
index 000000000..608cb5688
--- /dev/null
+++ b/net/mptcp/mib.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/seq_file.h>
+#include <net/ip.h>
+#include <net/mptcp.h>
+#include <net/snmp.h>
+#include <net/net_namespace.h>
+
+#include "mib.h"
+
+static const struct snmp_mib mptcp_snmp_list[] = {
+	SNMP_MIB_ITEM("MPCapableSYNRX", MPTCP_MIB_MPCAPABLEPASSIVE),
+	SNMP_MIB_ITEM("MPCapableSYNTX", MPTCP_MIB_MPCAPABLEACTIVE),
+	SNMP_MIB_ITEM("MPCapableSYNACKRX", MPTCP_MIB_MPCAPABLEACTIVEACK),
+	SNMP_MIB_ITEM("MPCapableACKRX", MPTCP_MIB_MPCAPABLEPASSIVEACK),
+	SNMP_MIB_ITEM("MPCapableFallbackACK", MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK),
+	SNMP_MIB_ITEM("MPCapableFallbackSYNACK", MPTCP_MIB_MPCAPABLEACTIVEFALLBACK),
+	SNMP_MIB_ITEM("MPCapableSYNTXDrop", MPTCP_MIB_MPCAPABLEACTIVEDROP),
+	SNMP_MIB_ITEM("MPCapableSYNTXDisabled", MPTCP_MIB_MPCAPABLEACTIVEDISABLED),
+	SNMP_MIB_ITEM("MPCapableEndpAttempt", MPTCP_MIB_MPCAPABLEENDPATTEMPT),
+	SNMP_MIB_ITEM("MPFallbackTokenInit", MPTCP_MIB_TOKENFALLBACKINIT),
+	SNMP_MIB_ITEM("MPTCPRetrans", MPTCP_MIB_RETRANSSEGS),
+	SNMP_MIB_ITEM("MPJoinNoTokenFound", MPTCP_MIB_JOINNOTOKEN),
+	SNMP_MIB_ITEM("MPJoinNoIdFound", MPTCP_MIB_MPJOINNOIDFOUND),
+	SNMP_MIB_ITEM("MPJoinSynRx", MPTCP_MIB_JOINSYNRX),
+	SNMP_MIB_ITEM("MPJoinSynBackupRx", MPTCP_MIB_JOINSYNBACKUPRX),
+	SNMP_MIB_ITEM("MPJoinSynAckRx", MPTCP_MIB_JOINSYNACKRX),
+	SNMP_MIB_ITEM("MPJoinSynAckBackupRx", MPTCP_MIB_JOINSYNACKBACKUPRX),
+	SNMP_MIB_ITEM("MPJoinSynAckHMacFailure", MPTCP_MIB_JOINSYNACKMAC),
+	SNMP_MIB_ITEM("MPJoinSynAckNoMPJoin", MPTCP_MIB_MPJOINSYNACKNOMPJOIN),
+	SNMP_MIB_ITEM("MPJoinAckRx", MPTCP_MIB_JOINACKRX),
+	SNMP_MIB_ITEM("MPJoinAckHMacFailure", MPTCP_MIB_JOINACKMAC),
+	SNMP_MIB_ITEM("MPJoinAckNoMPJoin", MPTCP_MIB_MPJOINACKNOMPJOIN),
+	SNMP_MIB_ITEM("MPJoinAckNoCtx", MPTCP_MIB_MPJOINACKNOCTX),
+	SNMP_MIB_ITEM("MPJoinRejected", MPTCP_MIB_JOINREJECTED),
+	SNMP_MIB_ITEM("MPJoinNotEstablished", MPTCP_MIB_MPJOINNOTESTABLISHED),
+	SNMP_MIB_ITEM("MPJoinSynTx", MPTCP_MIB_JOINSYNTX),
+	SNMP_MIB_ITEM("MPJoinSynTxCreatSkErr", MPTCP_MIB_JOINSYNTXCREATSKERR),
+	SNMP_MIB_ITEM("MPJoinSynTxBindErr", MPTCP_MIB_JOINSYNTXBINDERR),
+	SNMP_MIB_ITEM("MPJoinSynTxConnectErr", MPTCP_MIB_JOINSYNTXCONNECTERR),
+	SNMP_MIB_ITEM("DSSNotMatching", MPTCP_MIB_DSSNOMATCH),
+	SNMP_MIB_ITEM("DSSCorruptionFallback", MPTCP_MIB_DSSCORRUPTIONFALLBACK),
+	SNMP_MIB_ITEM("DSSCorruptionReset", MPTCP_MIB_DSSCORRUPTIONRESET),
+	SNMP_MIB_ITEM("InfiniteMapTx", MPTCP_MIB_INFINITEMAPTX),
+	SNMP_MIB_ITEM("InfiniteMapRx", MPTCP_MIB_INFINITEMAPRX),
+	SNMP_MIB_ITEM("DSSNoMatchTCP", MPTCP_MIB_DSSTCPMISMATCH),
+	SNMP_MIB_ITEM("DataCsumErr", MPTCP_MIB_DATACSUMERR),
+	SNMP_MIB_ITEM("OFOQueueTail", MPTCP_MIB_OFOQUEUETAIL),
+	SNMP_MIB_ITEM("OFOQueue", MPTCP_MIB_OFOQUEUE),
+	SNMP_MIB_ITEM("OFOMerge", MPTCP_MIB_OFOMERGE),
+	SNMP_MIB_ITEM("NoDSSInWindow", MPTCP_MIB_NODSSWINDOW),
+	SNMP_MIB_ITEM("DuplicateData", MPTCP_MIB_DUPDATA),
+	SNMP_MIB_ITEM("AddAddr", MPTCP_MIB_ADDADDR),
+	SNMP_MIB_ITEM("AddAddrTx", MPTCP_MIB_ADDADDRTX),
+	SNMP_MIB_ITEM("AddAddrTxDrop", MPTCP_MIB_ADDADDRTXDROP),
+	SNMP_MIB_ITEM("EchoAdd", MPTCP_MIB_ECHOADD),
+	SNMP_MIB_ITEM("EchoAddTx", MPTCP_MIB_ECHOADDTX),
+	SNMP_MIB_ITEM("EchoAddTxDrop", MPTCP_MIB_ECHOADDTXDROP),
+	SNMP_MIB_ITEM("PortAdd", MPTCP_MIB_PORTADD),
+	SNMP_MIB_ITEM("AddAddrDrop", MPTCP_MIB_ADDADDRDROP),
+	SNMP_MIB_ITEM("MPJoinPortSynRx", MPTCP_MIB_JOINPORTSYNRX),
+	SNMP_MIB_ITEM("MPJoinPortSynAckRx", MPTCP_MIB_JOINPORTSYNACKRX),
+	SNMP_MIB_ITEM("MPJoinPortAckRx", MPTCP_MIB_JOINPORTACKRX),
+	SNMP_MIB_ITEM("MismatchPortSynRx", MPTCP_MIB_MISMATCHPORTSYNRX),
+	SNMP_MIB_ITEM("MismatchPortAckRx", MPTCP_MIB_MISMATCHPORTACKRX),
+	SNMP_MIB_ITEM("RmAddr", MPTCP_MIB_RMADDR),
+	SNMP_MIB_ITEM("RmAddrDrop", MPTCP_MIB_RMADDRDROP),
+	SNMP_MIB_ITEM("RmAddrTx", MPTCP_MIB_RMADDRTX),
+	SNMP_MIB_ITEM("RmAddrTxDrop", MPTCP_MIB_RMADDRTXDROP),
+	SNMP_MIB_ITEM("RmSubflow", MPTCP_MIB_RMSUBFLOW),
+	SNMP_MIB_ITEM("MPPrioTx", MPTCP_MIB_MPPRIOTX),
+	SNMP_MIB_ITEM("MPPrioRx", MPTCP_MIB_MPPRIORX),
+	SNMP_MIB_ITEM("MPFailTx", MPTCP_MIB_MPFAILTX),
+	SNMP_MIB_ITEM("MPFailRx", MPTCP_MIB_MPFAILRX),
+	SNMP_MIB_ITEM("MPFastcloseTx", MPTCP_MIB_MPFASTCLOSETX),
+	SNMP_MIB_ITEM("MPFastcloseRx", MPTCP_MIB_MPFASTCLOSERX),
+	SNMP_MIB_ITEM("MPRstTx", MPTCP_MIB_MPRSTTX),
+	SNMP_MIB_ITEM("MPRstRx", MPTCP_MIB_MPRSTRX),
+	SNMP_MIB_ITEM("SubflowStale", MPTCP_MIB_SUBFLOWSTALE),
+	SNMP_MIB_ITEM("SubflowRecover", MPTCP_MIB_SUBFLOWRECOVER),
+	SNMP_MIB_ITEM("SndWndShared", MPTCP_MIB_SNDWNDSHARED),
+	SNMP_MIB_ITEM("RcvWndShared", MPTCP_MIB_RCVWNDSHARED),
+	SNMP_MIB_ITEM("RcvWndConflictUpdate", MPTCP_MIB_RCVWNDCONFLICTUPDATE),
+	SNMP_MIB_ITEM("RcvWndConflict", MPTCP_MIB_RCVWNDCONFLICT),
+	SNMP_MIB_ITEM("MPCurrEstab", MPTCP_MIB_CURRESTAB),
+	SNMP_MIB_ITEM("Blackhole", MPTCP_MIB_BLACKHOLE),
+	SNMP_MIB_ITEM("MPCapableDataFallback", MPTCP_MIB_MPCAPABLEDATAFALLBACK),
+	SNMP_MIB_ITEM("MD5SigFallback", MPTCP_MIB_MD5SIGFALLBACK),
+	SNMP_MIB_ITEM("MD5SigReset", MPTCP_MIB_MD5SIGRESET),
+	SNMP_MIB_ITEM("DssFallback", MPTCP_MIB_DSSFALLBACK),
+	SNMP_MIB_ITEM("DssReset", MPTCP_MIB_DSSRESET),
+	SNMP_MIB_ITEM("SimultConnectFallback", MPTCP_MIB_SIMULTCONNFALLBACK),
+	SNMP_MIB_ITEM("FallbackFailed", MPTCP_MIB_FALLBACKFAILED),
+	SNMP_MIB_ITEM("WinProbe", MPTCP_MIB_WINPROBE),
+	SNMP_MIB_ITEM("BacklogDrop", MPTCP_MIB_BACKLOGDROP),
+	SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED),
+	SNMP_MIB_ITEM("OFOPruned", MPTCP_MIB_OFOPRUNED),
+};
+
+/* mptcp_mib_alloc - allocate percpu mib counters
+ *
+ * These are allocated when the first mptcp socket is created so
+ * we do not waste percpu memory if mptcp isn't in use.
+ */
+bool mptcp_mib_alloc(struct net *net)
+{
+	struct mptcp_mib __percpu *mib = alloc_percpu(struct mptcp_mib);
+
+	if (!mib)
+		return false;
+
+	if (cmpxchg(&net->mib.mptcp_statistics, NULL, mib))
+		free_percpu(mib);
+
+	return true;
+}
+
+void mptcp_seq_show(struct seq_file *seq)
+{
+	unsigned long sum[ARRAY_SIZE(mptcp_snmp_list)];
+	const int cnt = ARRAY_SIZE(mptcp_snmp_list);
+	struct net *net = seq->private;
+	int i;
+
+	seq_puts(seq, "MPTcpExt:");
+	for (i = 0; i < cnt; i++)
+		seq_printf(seq, " %s", mptcp_snmp_list[i].name);
+
+	seq_puts(seq, "\nMPTcpExt:");
+
+	memset(sum, 0, sizeof(sum));
+	if (net->mib.mptcp_statistics)
+		snmp_get_cpu_field_batch_cnt(sum, mptcp_snmp_list, cnt,
+					     net->mib.mptcp_statistics);
+
+	for (i = 0; i < cnt; i++)
+		seq_printf(seq, " %lu", sum[i]);
+
+	seq_putc(seq, '\n');
+}
diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
new file mode 100644
index 000000000..1ebdb55e9
--- /dev/null
+++ b/net/mptcp/mib.h
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <net/inet_common.h>
+
+enum linux_mptcp_mib_field {
+	MPTCP_MIB_NUM = 0,
+	MPTCP_MIB_MPCAPABLEPASSIVE,	/* Received SYN with MP_CAPABLE */
+	MPTCP_MIB_MPCAPABLEACTIVE,	/* Sent SYN with MP_CAPABLE */
+	MPTCP_MIB_MPCAPABLEACTIVEACK,	/* Received SYN/ACK with MP_CAPABLE */
+	MPTCP_MIB_MPCAPABLEPASSIVEACK,	/* Received third ACK with MP_CAPABLE */
+	MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK,/* Server-side fallback during 3-way handshake */
+	MPTCP_MIB_MPCAPABLEACTIVEFALLBACK, /* Client-side fallback during 3-way handshake */
+	MPTCP_MIB_MPCAPABLEACTIVEDROP,	/* Client-side fallback due to a MPC drop */
+	MPTCP_MIB_MPCAPABLEACTIVEDISABLED, /* Client-side disabled due to past issues */
+	MPTCP_MIB_MPCAPABLEENDPATTEMPT,	/* Prohibited MPC to port-based endp */
+	MPTCP_MIB_TOKENFALLBACKINIT,	/* Could not init/allocate token */
+	MPTCP_MIB_RETRANSSEGS,		/* Segments retransmitted at the MPTCP-level */
+	MPTCP_MIB_JOINNOTOKEN,		/* Received MP_JOIN but the token was not found */
+	MPTCP_MIB_MPJOINNOIDFOUND,	/* Received MP_JOIN but no local ID was found */
+	MPTCP_MIB_JOINSYNRX,		/* Received a SYN + MP_JOIN */
+	MPTCP_MIB_JOINSYNBACKUPRX,	/* Received a SYN + MP_JOIN + backup flag */
+	MPTCP_MIB_JOINSYNACKRX,		/* Received a SYN/ACK + MP_JOIN */
+	MPTCP_MIB_JOINSYNACKBACKUPRX,	/* Received a SYN/ACK + MP_JOIN + backup flag */
+	MPTCP_MIB_JOINSYNACKMAC,	/* HMAC was wrong on SYN/ACK + MP_JOIN */
+	MPTCP_MIB_MPJOINSYNACKNOMPJOIN,	/* MP_RST: missing MP_JOIN in SYN/ACK */
+	MPTCP_MIB_JOINACKRX,		/* Received an ACK + MP_JOIN */
+	MPTCP_MIB_JOINACKMAC,		/* HMAC was wrong on ACK + MP_JOIN */
+	MPTCP_MIB_MPJOINACKNOMPJOIN,	/* MP_RST: missing MP_JOIN in ACK */
+	MPTCP_MIB_MPJOINACKNOCTX,	/* MP_RST: no subflow context on ACK */
+	MPTCP_MIB_JOINREJECTED,		/* The PM rejected the JOIN request */
+	MPTCP_MIB_MPJOINNOTESTABLISHED,	/* MP_RST: JOIN on not-fully-established msk */
+	MPTCP_MIB_JOINSYNTX,		/* Sending a SYN + MP_JOIN */
+	MPTCP_MIB_JOINSYNTXCREATSKERR,	/* Not able to create a socket when sending a SYN + MP_JOIN */
+	MPTCP_MIB_JOINSYNTXBINDERR,	/* Not able to bind() the address when sending a SYN + MP_JOIN */
+	MPTCP_MIB_JOINSYNTXCONNECTERR,	/* Not able to connect() when sending a SYN + MP_JOIN */
+	MPTCP_MIB_DSSNOMATCH,		/* Received a new mapping that did not match the previous one */
+	MPTCP_MIB_DSSCORRUPTIONFALLBACK,/* DSS corruption detected, fallback */
+	MPTCP_MIB_DSSCORRUPTIONRESET,	/* DSS corruption detected, MPJ subflow reset */
+	MPTCP_MIB_INFINITEMAPTX,	/* Sent an infinite mapping */
+	MPTCP_MIB_INFINITEMAPRX,	/* Received an infinite mapping */
+	MPTCP_MIB_DSSTCPMISMATCH,	/* DSS-mapping did not map with TCP's sequence numbers */
+	MPTCP_MIB_DATACSUMERR,		/* The data checksum fail */
+	MPTCP_MIB_OFOQUEUETAIL,	/* Segments inserted into OoO queue tail */
+	MPTCP_MIB_OFOQUEUE,		/* Segments inserted into OoO queue */
+	MPTCP_MIB_OFOMERGE,		/* Segments merged in OoO queue */
+	MPTCP_MIB_NODSSWINDOW,		/* Segments not in MPTCP windows */
+	MPTCP_MIB_DUPDATA,		/* Segments discarded due to duplicate DSS */
+	MPTCP_MIB_ADDADDR,		/* Received ADD_ADDR with echo-flag=0 */
+	MPTCP_MIB_ADDADDRTX,		/* Sent ADD_ADDR with echo-flag=0 */
+	MPTCP_MIB_ADDADDRTXDROP,	/* ADD_ADDR with echo-flag=0 not send due to
+					 * resource exhaustion
+					 */
+	MPTCP_MIB_ECHOADD,		/* Received ADD_ADDR with echo-flag=1 */
+	MPTCP_MIB_ECHOADDTX,		/* Send ADD_ADDR with echo-flag=1 */
+	MPTCP_MIB_ECHOADDTXDROP,	/* ADD_ADDR with echo-flag=1 not send due
+					 * to resource exhaustion
+					 */
+	MPTCP_MIB_PORTADD,		/* Received ADD_ADDR with a port-number */
+	MPTCP_MIB_ADDADDRDROP,		/* Dropped incoming ADD_ADDR */
+	MPTCP_MIB_JOINPORTSYNRX,	/* Received a SYN MP_JOIN with a different port-number */
+	MPTCP_MIB_JOINPORTSYNACKRX,	/* Received a SYNACK MP_JOIN with a different port-number */
+	MPTCP_MIB_JOINPORTACKRX,	/* Received an ACK MP_JOIN with a different port-number */
+	MPTCP_MIB_MISMATCHPORTSYNRX,	/* Received a SYN MP_JOIN with a mismatched port-number */
+	MPTCP_MIB_MISMATCHPORTACKRX,	/* Received an ACK MP_JOIN with a mismatched port-number */
+	MPTCP_MIB_RMADDR,		/* Received RM_ADDR */
+	MPTCP_MIB_RMADDRDROP,		/* Dropped incoming RM_ADDR */
+	MPTCP_MIB_RMADDRTX,		/* Sent RM_ADDR */
+	MPTCP_MIB_RMADDRTXDROP,		/* RM_ADDR not sent due to resource exhaustion */
+	MPTCP_MIB_RMSUBFLOW,		/* Remove a subflow */
+	MPTCP_MIB_MPPRIOTX,		/* Transmit a MP_PRIO */
+	MPTCP_MIB_MPPRIORX,		/* Received a MP_PRIO */
+	MPTCP_MIB_MPFAILTX,		/* Transmit a MP_FAIL */
+	MPTCP_MIB_MPFAILRX,		/* Received a MP_FAIL */
+	MPTCP_MIB_MPFASTCLOSETX,	/* Transmit a MP_FASTCLOSE */
+	MPTCP_MIB_MPFASTCLOSERX,	/* Received a MP_FASTCLOSE */
+	MPTCP_MIB_MPRSTTX,		/* Transmit a MP_RST */
+	MPTCP_MIB_MPRSTRX,		/* Received a MP_RST */
+	MPTCP_MIB_SUBFLOWSTALE,		/* Subflows entered 'stale' status */
+	MPTCP_MIB_SUBFLOWRECOVER,	/* Subflows returned to active status after being stale */
+	MPTCP_MIB_SNDWNDSHARED,		/* Subflow snd wnd is overridden by msk's one */
+	MPTCP_MIB_RCVWNDSHARED,		/* Subflow rcv wnd is overridden by msk's one */
+	MPTCP_MIB_RCVWNDCONFLICTUPDATE,	/* subflow rcv wnd is overridden by msk's one due to
+					 * conflict with another subflow while updating msk rcv wnd
+					 */
+	MPTCP_MIB_RCVWNDCONFLICT,	/* Conflict with while updating msk rcv wnd */
+	MPTCP_MIB_CURRESTAB,		/* Current established MPTCP connections */
+	MPTCP_MIB_BLACKHOLE,		/* A blackhole has been detected */
+	MPTCP_MIB_MPCAPABLEDATAFALLBACK,	/* Missing DSS/MPC+data on first
+					 * established packet
+					 */
+	MPTCP_MIB_MD5SIGFALLBACK,	/* Conflicting TCP option enabled */
+	MPTCP_MIB_MD5SIGRESET,		/* MP_RST: MD5SIG enabled on listener */
+	MPTCP_MIB_DSSFALLBACK,		/* Bad or missing DSS */
+	MPTCP_MIB_DSSRESET,		/* MP_RST: bad data mapping */
+	MPTCP_MIB_SIMULTCONNFALLBACK,	/* Simultaneous connect */
+	MPTCP_MIB_FALLBACKFAILED,	/* Can't fallback due to msk status */
+	MPTCP_MIB_WINPROBE,		/* MPTCP-level zero window probe */
+	MPTCP_MIB_BACKLOGDROP,		/* Backlog over memory limit */
+	MPTCP_MIB_RCVPRUNED,		/* Dropped due to memory constraints */
+	MPTCP_MIB_OFOPRUNED,		/* MPTCP-level OoO queue pruned */
+	__MPTCP_MIB_MAX
+};
+
+#define LINUX_MIB_MPTCP_MAX	__MPTCP_MIB_MAX
+struct mptcp_mib {
+	unsigned long mibs[LINUX_MIB_MPTCP_MAX];
+};
+
+static inline void MPTCP_ADD_STATS(struct net *net,
+				   enum linux_mptcp_mib_field field,
+				   int val)
+{
+	if (likely(net->mib.mptcp_statistics))
+		SNMP_ADD_STATS(net->mib.mptcp_statistics, field, val);
+}
+
+static inline void MPTCP_INC_STATS(struct net *net,
+				   enum linux_mptcp_mib_field field)
+{
+	if (likely(net->mib.mptcp_statistics))
+		SNMP_INC_STATS(net->mib.mptcp_statistics, field);
+}
+
+static inline void __MPTCP_INC_STATS(struct net *net,
+				     enum linux_mptcp_mib_field field)
+{
+	if (likely(net->mib.mptcp_statistics))
+		__SNMP_INC_STATS(net->mib.mptcp_statistics, field);
+}
+
+static inline void MPTCP_DEC_STATS(struct net *net,
+				   enum linux_mptcp_mib_field field)
+{
+	if (likely(net->mib.mptcp_statistics))
+		SNMP_DEC_STATS(net->mib.mptcp_statistics, field);
+}
+
+bool mptcp_mib_alloc(struct net *net);
diff --git a/net/mptcp/mptcp_diag.c b/net/mptcp/mptcp_diag.c
new file mode 100644
index 000000000..136c2d05c
--- /dev/null
+++ b/net/mptcp/mptcp_diag.c
@@ -0,0 +1,243 @@
+// SPDX-License-Identifier: GPL-2.0
+/* MPTCP socket monitoring support
+ *
+ * Copyright (c) 2020 Red Hat
+ *
+ * Author: Paolo Abeni <pabeni@redhat.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/net.h>
+#include <linux/inet_diag.h>
+#include <net/netlink.h>
+#include "protocol.h"
+
+static int sk_diag_dump(struct sock *sk, struct sk_buff *skb,
+			struct netlink_callback *cb,
+			const struct inet_diag_req_v2 *req,
+			bool net_admin)
+{
+	if (!inet_diag_bc_sk(cb->data, sk))
+		return 0;
+
+	return inet_sk_diag_fill(sk, inet_csk(sk), skb, cb, req, NLM_F_MULTI,
+				 net_admin);
+}
+
+static int mptcp_diag_dump_one(struct netlink_callback *cb,
+			       const struct inet_diag_req_v2 *req)
+{
+	struct sk_buff *in_skb = cb->skb;
+	struct mptcp_sock *msk = NULL;
+	struct sk_buff *rep;
+	int err = -ENOENT;
+	struct net *net;
+	struct sock *sk;
+
+	net = sock_net(in_skb->sk);
+	msk = mptcp_token_get_sock(net, req->id.idiag_cookie[0]);
+	if (!msk)
+		goto out_nosk;
+
+	err = -ENOMEM;
+	sk = (struct sock *)msk;
+	rep = nlmsg_new(nla_total_size(sizeof(struct inet_diag_msg)) +
+			inet_diag_msg_attrs_size() +
+			nla_total_size(sizeof(struct mptcp_info)) +
+			nla_total_size(sizeof(struct inet_diag_meminfo)) + 64,
+			GFP_KERNEL);
+	if (!rep)
+		goto out;
+
+	err = inet_sk_diag_fill(sk, inet_csk(sk), rep, cb, req, 0,
+				netlink_net_capable(in_skb, CAP_NET_ADMIN));
+	if (err < 0) {
+		WARN_ON(err == -EMSGSIZE);
+		kfree_skb(rep);
+		goto out;
+	}
+	err = nlmsg_unicast(net->diag_nlsk, rep, NETLINK_CB(in_skb).portid);
+
+out:
+	sock_put(sk);
+
+out_nosk:
+	return err;
+}
+
+struct mptcp_diag_ctx {
+	long s_slot;
+	long s_num;
+	unsigned int l_slot;
+	unsigned int l_num;
+};
+
+static void mptcp_diag_dump_listeners(struct sk_buff *skb, struct netlink_callback *cb,
+				      const struct inet_diag_req_v2 *r,
+				      bool net_admin)
+{
+	struct mptcp_diag_ctx *diag_ctx = (void *)cb->ctx;
+	struct net *net = sock_net(skb->sk);
+	struct inet_hashinfo *hinfo;
+	int i;
+
+	hinfo = net->ipv4.tcp_death_row.hashinfo;
+
+	for (i = diag_ctx->l_slot; i <= hinfo->lhash2_mask; i++) {
+		struct inet_listen_hashbucket *ilb;
+		struct hlist_nulls_node *node;
+		struct sock *sk;
+		int num = 0;
+
+		ilb = &hinfo->lhash2[i];
+
+		rcu_read_lock();
+		spin_lock(&ilb->lock);
+		sk_nulls_for_each(sk, node, &ilb->nulls_head) {
+			const struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(sk);
+			struct inet_sock *inet = inet_sk(sk);
+			int ret;
+
+			if (num < diag_ctx->l_num)
+				goto next_listen;
+
+			if (!ctx || strcmp(inet_csk(sk)->icsk_ulp_ops->name, "mptcp"))
+				goto next_listen;
+
+			sk = ctx->conn;
+			if (!sk || !net_eq(sock_net(sk), net))
+				goto next_listen;
+
+			if (r->sdiag_family != AF_UNSPEC &&
+			    sk->sk_family != r->sdiag_family)
+				goto next_listen;
+
+			if (r->id.idiag_sport != inet->inet_sport &&
+			    r->id.idiag_sport)
+				goto next_listen;
+
+			if (!refcount_inc_not_zero(&sk->sk_refcnt))
+				goto next_listen;
+
+			ret = sk_diag_dump(sk, skb, cb, r, net_admin);
+
+			sock_put(sk);
+
+			if (ret < 0) {
+				spin_unlock(&ilb->lock);
+				rcu_read_unlock();
+				diag_ctx->l_slot = i;
+				diag_ctx->l_num = num;
+				return;
+			}
+			diag_ctx->l_num = num + 1;
+			num = 0;
+next_listen:
+			++num;
+		}
+		spin_unlock(&ilb->lock);
+		rcu_read_unlock();
+
+		cond_resched();
+		diag_ctx->l_num = 0;
+	}
+
+	diag_ctx->l_num = 0;
+	diag_ctx->l_slot = i;
+}
+
+static void mptcp_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
+			    const struct inet_diag_req_v2 *r)
+{
+	bool net_admin = netlink_net_capable(cb->skb, CAP_NET_ADMIN);
+	struct mptcp_diag_ctx *diag_ctx = (void *)cb->ctx;
+	struct net *net = sock_net(skb->sk);
+	struct mptcp_sock *msk;
+
+	BUILD_BUG_ON(sizeof(cb->ctx) < sizeof(*diag_ctx));
+
+	while ((msk = mptcp_token_iter_next(net, &diag_ctx->s_slot,
+					    &diag_ctx->s_num)) != NULL) {
+		struct inet_sock *inet = (struct inet_sock *)msk;
+		struct sock *sk = (struct sock *)msk;
+		int ret = 0;
+
+		if (!(r->idiag_states & (1 << sk->sk_state)))
+			goto next;
+		if (r->sdiag_family != AF_UNSPEC &&
+		    sk->sk_family != r->sdiag_family)
+			goto next;
+		if (r->id.idiag_sport != inet->inet_sport &&
+		    r->id.idiag_sport)
+			goto next;
+		if (r->id.idiag_dport != inet->inet_dport &&
+		    r->id.idiag_dport)
+			goto next;
+
+		ret = sk_diag_dump(sk, skb, cb, r, net_admin);
+next:
+		sock_put(sk);
+		if (ret < 0) {
+			/* will retry on the same position */
+			diag_ctx->s_num--;
+			break;
+		}
+		cond_resched();
+	}
+
+	if ((r->idiag_states & TCPF_LISTEN) && r->id.idiag_dport == 0)
+		mptcp_diag_dump_listeners(skb, cb, r, net_admin);
+}
+
+static void mptcp_diag_get_info(struct sock *sk, struct inet_diag_msg *r,
+				void *_info)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_info *info = _info;
+
+	r->idiag_rqueue = sk_rmem_alloc_get(sk) +
+			  READ_ONCE(mptcp_sk(sk)->backlog_len);
+	r->idiag_wqueue = sk_wmem_alloc_get(sk);
+
+	if (inet_sk_state_load(sk) == TCP_LISTEN) {
+		struct sock *lsk = READ_ONCE(msk->first);
+
+		if (lsk) {
+			/* override with settings from tcp listener,
+			 * so Send-Q will show accept queue.
+			 */
+			r->idiag_rqueue = READ_ONCE(lsk->sk_ack_backlog);
+			r->idiag_wqueue = READ_ONCE(lsk->sk_max_ack_backlog);
+		}
+	}
+
+	if (!info)
+		return;
+
+	mptcp_diag_fill_info(msk, info);
+}
+
+static const struct inet_diag_handler mptcp_diag_handler = {
+	.owner		 = THIS_MODULE,
+	.dump		 = mptcp_diag_dump,
+	.dump_one	 = mptcp_diag_dump_one,
+	.idiag_get_info  = mptcp_diag_get_info,
+	.idiag_type	 = IPPROTO_MPTCP,
+	.idiag_info_size = sizeof(struct mptcp_info),
+};
+
+static int __init mptcp_diag_init(void)
+{
+	return inet_diag_register(&mptcp_diag_handler);
+}
+
+static void __exit mptcp_diag_exit(void)
+{
+	inet_diag_unregister(&mptcp_diag_handler);
+}
+
+module_init(mptcp_diag_init);
+module_exit(mptcp_diag_exit);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MPTCP socket monitoring via SOCK_DIAG");
+MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_NETLINK, NETLINK_SOCK_DIAG, 2-262 /* AF_INET - IPPROTO_MPTCP */);
diff --git a/net/mptcp/mptcp_pm_gen.c b/net/mptcp/mptcp_pm_gen.c
new file mode 100644
index 000000000..c180930a8
--- /dev/null
+++ b/net/mptcp/mptcp_pm_gen.c
@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/mptcp_pm.yaml */
+/* YNL-GEN kernel source */
+/* To regenerate run: tools/net/ynl/ynl-regen.sh */
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "mptcp_pm_gen.h"
+
+#include <uapi/linux/mptcp_pm.h>
+
+/* Common nested types */
+const struct nla_policy mptcp_pm_address_nl_policy[MPTCP_PM_ADDR_ATTR_IF_IDX + 1] = {
+	[MPTCP_PM_ADDR_ATTR_FAMILY] = { .type = NLA_U16, },
+	[MPTCP_PM_ADDR_ATTR_ID] = { .type = NLA_U8, },
+	[MPTCP_PM_ADDR_ATTR_ADDR4] = { .type = NLA_BE32, },
+	[MPTCP_PM_ADDR_ATTR_ADDR6] = NLA_POLICY_EXACT_LEN(16),
+	[MPTCP_PM_ADDR_ATTR_PORT] = { .type = NLA_U16, },
+	[MPTCP_PM_ADDR_ATTR_FLAGS] = { .type = NLA_U32, },
+	[MPTCP_PM_ADDR_ATTR_IF_IDX] = { .type = NLA_S32, },
+};
+
+/* MPTCP_PM_CMD_ADD_ADDR - do */
+const struct nla_policy mptcp_pm_add_addr_nl_policy[MPTCP_PM_ENDPOINT_ADDR + 1] = {
+	[MPTCP_PM_ENDPOINT_ADDR] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+};
+
+/* MPTCP_PM_CMD_DEL_ADDR - do */
+const struct nla_policy mptcp_pm_del_addr_nl_policy[MPTCP_PM_ENDPOINT_ADDR + 1] = {
+	[MPTCP_PM_ENDPOINT_ADDR] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+};
+
+/* MPTCP_PM_CMD_GET_ADDR - do */
+const struct nla_policy mptcp_pm_get_addr_nl_policy[MPTCP_PM_ATTR_TOKEN + 1] = {
+	[MPTCP_PM_ATTR_ADDR] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+	[MPTCP_PM_ATTR_TOKEN] = { .type = NLA_U32, },
+};
+
+/* MPTCP_PM_CMD_FLUSH_ADDRS - do */
+const struct nla_policy mptcp_pm_flush_addrs_nl_policy[MPTCP_PM_ENDPOINT_ADDR + 1] = {
+	[MPTCP_PM_ENDPOINT_ADDR] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+};
+
+/* MPTCP_PM_CMD_SET_LIMITS - do */
+const struct nla_policy mptcp_pm_set_limits_nl_policy[MPTCP_PM_ATTR_SUBFLOWS + 1] = {
+	[MPTCP_PM_ATTR_RCV_ADD_ADDRS] = { .type = NLA_U32, },
+	[MPTCP_PM_ATTR_SUBFLOWS] = { .type = NLA_U32, },
+};
+
+/* MPTCP_PM_CMD_GET_LIMITS - do */
+const struct nla_policy mptcp_pm_get_limits_nl_policy[MPTCP_PM_ATTR_SUBFLOWS + 1] = {
+	[MPTCP_PM_ATTR_RCV_ADD_ADDRS] = { .type = NLA_U32, },
+	[MPTCP_PM_ATTR_SUBFLOWS] = { .type = NLA_U32, },
+};
+
+/* MPTCP_PM_CMD_SET_FLAGS - do */
+const struct nla_policy mptcp_pm_set_flags_nl_policy[MPTCP_PM_ATTR_ADDR_REMOTE + 1] = {
+	[MPTCP_PM_ATTR_ADDR] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+	[MPTCP_PM_ATTR_TOKEN] = { .type = NLA_U32, },
+	[MPTCP_PM_ATTR_ADDR_REMOTE] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+};
+
+/* MPTCP_PM_CMD_ANNOUNCE - do */
+const struct nla_policy mptcp_pm_announce_nl_policy[MPTCP_PM_ATTR_TOKEN + 1] = {
+	[MPTCP_PM_ATTR_ADDR] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+	[MPTCP_PM_ATTR_TOKEN] = { .type = NLA_U32, },
+};
+
+/* MPTCP_PM_CMD_REMOVE - do */
+const struct nla_policy mptcp_pm_remove_nl_policy[MPTCP_PM_ATTR_LOC_ID + 1] = {
+	[MPTCP_PM_ATTR_TOKEN] = { .type = NLA_U32, },
+	[MPTCP_PM_ATTR_LOC_ID] = { .type = NLA_U8, },
+};
+
+/* MPTCP_PM_CMD_SUBFLOW_CREATE - do */
+const struct nla_policy mptcp_pm_subflow_create_nl_policy[MPTCP_PM_ATTR_ADDR_REMOTE + 1] = {
+	[MPTCP_PM_ATTR_ADDR] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+	[MPTCP_PM_ATTR_TOKEN] = { .type = NLA_U32, },
+	[MPTCP_PM_ATTR_ADDR_REMOTE] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+};
+
+/* MPTCP_PM_CMD_SUBFLOW_DESTROY - do */
+const struct nla_policy mptcp_pm_subflow_destroy_nl_policy[MPTCP_PM_ATTR_ADDR_REMOTE + 1] = {
+	[MPTCP_PM_ATTR_ADDR] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+	[MPTCP_PM_ATTR_TOKEN] = { .type = NLA_U32, },
+	[MPTCP_PM_ATTR_ADDR_REMOTE] = NLA_POLICY_NESTED(mptcp_pm_address_nl_policy),
+};
+
+/* Ops table for mptcp_pm */
+const struct genl_ops mptcp_pm_nl_ops[11] = {
+	{
+		.cmd		= MPTCP_PM_CMD_ADD_ADDR,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_add_addr_doit,
+		.policy		= mptcp_pm_add_addr_nl_policy,
+		.maxattr	= MPTCP_PM_ENDPOINT_ADDR,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_DEL_ADDR,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_del_addr_doit,
+		.policy		= mptcp_pm_del_addr_nl_policy,
+		.maxattr	= MPTCP_PM_ENDPOINT_ADDR,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_GET_ADDR,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_get_addr_doit,
+		.dumpit		= mptcp_pm_nl_get_addr_dumpit,
+		.policy		= mptcp_pm_get_addr_nl_policy,
+		.maxattr	= MPTCP_PM_ATTR_TOKEN,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_FLUSH_ADDRS,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_flush_addrs_doit,
+		.policy		= mptcp_pm_flush_addrs_nl_policy,
+		.maxattr	= MPTCP_PM_ENDPOINT_ADDR,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_SET_LIMITS,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_set_limits_doit,
+		.policy		= mptcp_pm_set_limits_nl_policy,
+		.maxattr	= MPTCP_PM_ATTR_SUBFLOWS,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_GET_LIMITS,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_get_limits_doit,
+		.policy		= mptcp_pm_get_limits_nl_policy,
+		.maxattr	= MPTCP_PM_ATTR_SUBFLOWS,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_SET_FLAGS,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_set_flags_doit,
+		.policy		= mptcp_pm_set_flags_nl_policy,
+		.maxattr	= MPTCP_PM_ATTR_ADDR_REMOTE,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_ANNOUNCE,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_announce_doit,
+		.policy		= mptcp_pm_announce_nl_policy,
+		.maxattr	= MPTCP_PM_ATTR_TOKEN,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_REMOVE,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_remove_doit,
+		.policy		= mptcp_pm_remove_nl_policy,
+		.maxattr	= MPTCP_PM_ATTR_LOC_ID,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_SUBFLOW_CREATE,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_subflow_create_doit,
+		.policy		= mptcp_pm_subflow_create_nl_policy,
+		.maxattr	= MPTCP_PM_ATTR_ADDR_REMOTE,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd		= MPTCP_PM_CMD_SUBFLOW_DESTROY,
+		.validate	= GENL_DONT_VALIDATE_STRICT,
+		.doit		= mptcp_pm_nl_subflow_destroy_doit,
+		.policy		= mptcp_pm_subflow_destroy_nl_policy,
+		.maxattr	= MPTCP_PM_ATTR_ADDR_REMOTE,
+		.flags		= GENL_UNS_ADMIN_PERM,
+	},
+};
diff --git a/net/mptcp/mptcp_pm_gen.h b/net/mptcp/mptcp_pm_gen.h
new file mode 100644
index 000000000..b9280bcb4
--- /dev/null
+++ b/net/mptcp/mptcp_pm_gen.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/mptcp_pm.yaml */
+/* YNL-GEN kernel header */
+/* To regenerate run: tools/net/ynl/ynl-regen.sh */
+
+#ifndef _LINUX_MPTCP_PM_GEN_H
+#define _LINUX_MPTCP_PM_GEN_H
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include <uapi/linux/mptcp_pm.h>
+
+/* Common nested types */
+extern const struct nla_policy mptcp_pm_address_nl_policy[MPTCP_PM_ADDR_ATTR_IF_IDX + 1];
+
+extern const struct nla_policy mptcp_pm_add_addr_nl_policy[MPTCP_PM_ENDPOINT_ADDR + 1];
+
+extern const struct nla_policy mptcp_pm_del_addr_nl_policy[MPTCP_PM_ENDPOINT_ADDR + 1];
+
+extern const struct nla_policy mptcp_pm_get_addr_nl_policy[MPTCP_PM_ATTR_TOKEN + 1];
+
+extern const struct nla_policy mptcp_pm_flush_addrs_nl_policy[MPTCP_PM_ENDPOINT_ADDR + 1];
+
+extern const struct nla_policy mptcp_pm_set_limits_nl_policy[MPTCP_PM_ATTR_SUBFLOWS + 1];
+
+extern const struct nla_policy mptcp_pm_get_limits_nl_policy[MPTCP_PM_ATTR_SUBFLOWS + 1];
+
+extern const struct nla_policy mptcp_pm_set_flags_nl_policy[MPTCP_PM_ATTR_ADDR_REMOTE + 1];
+
+extern const struct nla_policy mptcp_pm_announce_nl_policy[MPTCP_PM_ATTR_TOKEN + 1];
+
+extern const struct nla_policy mptcp_pm_remove_nl_policy[MPTCP_PM_ATTR_LOC_ID + 1];
+
+extern const struct nla_policy mptcp_pm_subflow_create_nl_policy[MPTCP_PM_ATTR_ADDR_REMOTE + 1];
+
+extern const struct nla_policy mptcp_pm_subflow_destroy_nl_policy[MPTCP_PM_ATTR_ADDR_REMOTE + 1];
+
+/* Ops table for mptcp_pm */
+extern const struct genl_ops mptcp_pm_nl_ops[11];
+
+int mptcp_pm_nl_add_addr_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_del_addr_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_get_addr_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_get_addr_dumpit(struct sk_buff *skb,
+				struct netlink_callback *cb);
+int mptcp_pm_nl_flush_addrs_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_set_limits_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_get_limits_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_set_flags_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_announce_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_remove_doit(struct sk_buff *skb, struct genl_info *info);
+int mptcp_pm_nl_subflow_create_doit(struct sk_buff *skb,
+				    struct genl_info *info);
+int mptcp_pm_nl_subflow_destroy_doit(struct sk_buff *skb,
+				     struct genl_info *info);
+
+#endif /* _LINUX_MPTCP_PM_GEN_H */
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
new file mode 100644
index 000000000..ce0de02f5
--- /dev/null
+++ b/net/mptcp/options.c
@@ -0,0 +1,1795 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/kernel.h>
+#include <crypto/sha2.h>
+#include <net/tcp.h>
+#include <net/mptcp.h>
+#include "protocol.h"
+#include "mib.h"
+
+#include <trace/events/mptcp.h>
+
+static bool mptcp_cap_flag_sha256(u8 flags)
+{
+	return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
+}
+
+static void mptcp_parse_option(const struct sk_buff *skb,
+			       const unsigned char *ptr, int opsize,
+			       struct mptcp_options_received *mp_opt)
+{
+	u8 subtype = *ptr >> 4;
+	int expected_opsize;
+	u16 subopt;
+	u8 version;
+	u8 flags;
+	u8 i;
+
+	switch (subtype) {
+	case MPTCPOPT_MP_CAPABLE:
+		/* strict size checking */
+		if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
+			if (skb->len > tcp_hdr(skb)->doff << 2)
+				expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
+			else
+				expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
+			subopt = OPTION_MPTCP_MPC_ACK;
+		} else {
+			if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) {
+				expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
+				subopt = OPTION_MPTCP_MPC_SYNACK;
+			} else {
+				expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
+				subopt = OPTION_MPTCP_MPC_SYN;
+			}
+		}
+
+		/* Only the MPC + ACK can be used with a RM_ADDR */
+		if (subopt == OPTION_MPTCP_MPC_ACK) {
+			if ((mp_opt->suboptions & ~OPTION_MPTCP_RM_ADDR) != 0)
+				break;
+		} else if (mp_opt->suboptions != 0) {
+			break;
+		}
+
+		/* Cfr RFC 8684 Section 3.3.0:
+		 * If a checksum is present but its use had
+		 * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
+		 * close the subflow with a RST, as it is not behaving as negotiated.
+		 * If a checksum is not present when its use has been negotiated, the
+		 * receiver MUST close the subflow with a RST, as it is considered
+		 * broken
+		 * We parse even option with mismatching csum presence, so that
+		 * later in subflow_data_ready we can trigger the reset.
+		 */
+		if (opsize != expected_opsize &&
+		    (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
+		     opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
+			break;
+
+		/* try to be gentle vs future versions on the initial syn */
+		version = *ptr++ & MPTCP_VERSION_MASK;
+		if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
+			if (version != MPTCP_SUPPORTED_VERSION)
+				break;
+		} else if (version < MPTCP_SUPPORTED_VERSION) {
+			break;
+		}
+
+		flags = *ptr++;
+		if (!mptcp_cap_flag_sha256(flags) ||
+		    (flags & MPTCP_CAP_EXTENSIBILITY))
+			break;
+
+		/* RFC 6824, Section 3.1:
+		 * "For the Checksum Required bit (labeled "A"), if either
+		 * host requires the use of checksums, checksums MUST be used.
+		 * In other words, the only way for checksums not to be used
+		 * is if both hosts in their SYNs set A=0."
+		 */
+		if ((flags & MPTCP_CAP_CHECKSUM_REQD) &&
+		    opsize < TCPOLEN_MPTCP_MPC_ACK_DATA)
+			mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
+
+		mp_opt->deny_join_id0 = !!(flags & MPTCP_CAP_DENY_JOIN_ID0);
+
+		mp_opt->suboptions |= subopt;
+		if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
+			mp_opt->sndr_key = get_unaligned_be64(ptr);
+			ptr += 8;
+		}
+		if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
+			mp_opt->rcvr_key = get_unaligned_be64(ptr);
+			ptr += 8;
+		}
+		if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
+			/* Section 3.1.:
+			 * "the data parameters in a MP_CAPABLE are semantically
+			 * equivalent to those in a DSS option and can be used
+			 * interchangeably."
+			 */
+			mp_opt->suboptions |= OPTION_MPTCP_DSS;
+			mp_opt->use_map = 1;
+			mp_opt->mpc_map = 1;
+			mp_opt->data_len = get_unaligned_be16(ptr);
+			ptr += 2;
+		}
+		if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
+			mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
+			mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
+			ptr += 2;
+		}
+		pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u\n",
+			 version, flags, opsize, mp_opt->sndr_key,
+			 mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
+		break;
+
+	case MPTCPOPT_MP_JOIN:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTION_MPTCP_RM_ADDR |
+					    OPTION_MPTCP_PRIO)) != 0)
+			break;
+
+		if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
+			mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYN;
+			mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
+			mp_opt->join_id = *ptr++;
+			mp_opt->token = get_unaligned_be32(ptr);
+			ptr += 4;
+			mp_opt->nonce = get_unaligned_be32(ptr);
+			ptr += 4;
+			pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u\n",
+				 mp_opt->backup, mp_opt->join_id,
+				 mp_opt->token, mp_opt->nonce);
+		} else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
+			mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYNACK;
+			mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
+			mp_opt->join_id = *ptr++;
+			mp_opt->thmac = get_unaligned_be64(ptr);
+			ptr += 8;
+			mp_opt->nonce = get_unaligned_be32(ptr);
+			ptr += 4;
+			pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u\n",
+				 mp_opt->backup, mp_opt->join_id,
+				 mp_opt->thmac, mp_opt->nonce);
+		} else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
+			mp_opt->suboptions |= OPTION_MPTCP_MPJ_ACK;
+			ptr += 2;
+			memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
+			pr_debug("MP_JOIN hmac\n");
+		}
+		break;
+
+	case MPTCPOPT_DSS:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTION_MPTCP_ADD_ADDR |
+					    OPTION_MPTCP_RM_ADDR |
+					    OPTION_MPTCP_PRIO |
+					    OPTION_MPTCP_FASTCLOSE |
+					    OPTION_MPTCP_FAIL)) != 0)
+			break;
+
+		pr_debug("DSS\n");
+		ptr++;
+
+		flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
+		mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
+		mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
+		mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
+		mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
+
+		expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
+
+		if (mp_opt->use_ack) {
+			if (mp_opt->ack64)
+				expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
+			else
+				expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
+		}
+
+		if (mp_opt->use_map) {
+			mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
+			if (mp_opt->dsn64)
+				expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
+			else
+				expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
+		}
+
+		pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d\n",
+			 mp_opt->data_fin, mp_opt->dsn64,
+			 mp_opt->use_map, mp_opt->ack64,
+			 mp_opt->use_ack);
+
+		/* Always parse any csum presence combination, we will enforce
+		 * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
+		 */
+		if (opsize != expected_opsize &&
+		    opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
+			mp_opt->dsn64 = 0;
+			mp_opt->use_map = 0;
+			mp_opt->ack64 = 0;
+			mp_opt->use_ack = 0;
+			mp_opt->data_fin = 0;
+			break;
+		}
+
+		mp_opt->suboptions |= OPTION_MPTCP_DSS;
+		if (mp_opt->use_ack) {
+			if (mp_opt->ack64) {
+				mp_opt->data_ack = get_unaligned_be64(ptr);
+				ptr += 8;
+			} else {
+				mp_opt->data_ack = get_unaligned_be32(ptr);
+				ptr += 4;
+			}
+
+			pr_debug("data_ack=%llu\n", mp_opt->data_ack);
+		}
+
+		if (mp_opt->use_map) {
+			if (mp_opt->dsn64) {
+				mp_opt->data_seq = get_unaligned_be64(ptr);
+				ptr += 8;
+			} else {
+				mp_opt->data_seq = get_unaligned_be32(ptr);
+				ptr += 4;
+			}
+
+			mp_opt->subflow_seq = get_unaligned_be32(ptr);
+			ptr += 4;
+
+			mp_opt->data_len = get_unaligned_be16(ptr);
+			ptr += 2;
+
+			if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
+				mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
+				mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
+				ptr += 2;
+			}
+
+			pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n",
+				 mp_opt->data_seq, mp_opt->subflow_seq,
+				 mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
+				 mp_opt->csum);
+		}
+
+		break;
+
+	case MPTCPOPT_ADD_ADDR:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_RM_ADDR |
+					    OPTION_MPTCP_PRIO)) != 0)
+			break;
+
+		mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
+		if (!mp_opt->echo) {
+			if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
+			    opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
+				mp_opt->addr.family = AF_INET;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+			else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
+				 opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
+				mp_opt->addr.family = AF_INET6;
+#endif
+			else
+				break;
+		} else {
+			if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
+			    opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
+				mp_opt->addr.family = AF_INET;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+			else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
+				 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
+				mp_opt->addr.family = AF_INET6;
+#endif
+			else
+				break;
+		}
+
+		mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
+		mp_opt->addr.id = *ptr++;
+		mp_opt->addr.port = 0;
+		mp_opt->ahmac = 0;
+		if (mp_opt->addr.family == AF_INET) {
+			memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
+			ptr += 4;
+			if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
+			    opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
+				mp_opt->addr.port = htons(get_unaligned_be16(ptr));
+				ptr += 2;
+			}
+		}
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+		else {
+			memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
+			ptr += 16;
+			if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
+			    opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
+				mp_opt->addr.port = htons(get_unaligned_be16(ptr));
+				ptr += 2;
+			}
+		}
+#endif
+		if (!mp_opt->echo) {
+			mp_opt->ahmac = get_unaligned_be64(ptr);
+			ptr += 8;
+		}
+		pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d\n",
+			 (mp_opt->addr.family == AF_INET6) ? "6" : "",
+			 mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
+		break;
+
+	case MPTCPOPT_RM_ADDR:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTION_MPTCP_MPC_ACK |
+					    OPTIONS_MPTCP_MPJ |
+					    OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_ADD_ADDR |
+					    OPTION_MPTCP_PRIO)) != 0)
+			break;
+
+		if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
+		    opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
+			break;
+
+		ptr++;
+
+		mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
+		mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
+		for (i = 0; i < mp_opt->rm_list.nr; i++)
+			mp_opt->rm_list.ids[i] = *ptr++;
+		pr_debug("RM_ADDR: rm_list_nr=%d\n", mp_opt->rm_list.nr);
+		break;
+
+	case MPTCPOPT_MP_PRIO:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTIONS_MPTCP_MPJ |
+					    OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_ADD_ADDR |
+					    OPTION_MPTCP_RM_ADDR)) != 0)
+			break;
+
+		if (opsize != TCPOLEN_MPTCP_PRIO)
+			break;
+
+		mp_opt->suboptions |= OPTION_MPTCP_PRIO;
+		mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
+		pr_debug("MP_PRIO: prio=%d\n", mp_opt->backup);
+		break;
+
+	case MPTCPOPT_MP_FASTCLOSE:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_RST)) != 0)
+			break;
+
+		if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
+			break;
+
+		ptr += 2;
+		mp_opt->rcvr_key = get_unaligned_be64(ptr);
+		ptr += 8;
+		mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
+		pr_debug("MP_FASTCLOSE: recv_key=%llu\n", mp_opt->rcvr_key);
+		break;
+
+	case MPTCPOPT_RST:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTION_MPTCP_FAIL |
+					    OPTION_MPTCP_FASTCLOSE)) != 0)
+			break;
+
+		if (opsize != TCPOLEN_MPTCP_RST)
+			break;
+
+		if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
+			break;
+
+		mp_opt->suboptions |= OPTION_MPTCP_RST;
+		flags = *ptr++;
+		mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
+		mp_opt->reset_reason = *ptr;
+		pr_debug("MP_RST: transient=%u reason=%u\n",
+			 mp_opt->reset_transient, mp_opt->reset_reason);
+		break;
+
+	case MPTCPOPT_MP_FAIL:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_RST)) != 0)
+			break;
+
+		if (opsize != TCPOLEN_MPTCP_FAIL)
+			break;
+
+		ptr += 2;
+		mp_opt->suboptions |= OPTION_MPTCP_FAIL;
+		mp_opt->fail_seq = get_unaligned_be64(ptr);
+		pr_debug("MP_FAIL: data_seq=%llu\n", mp_opt->fail_seq);
+		break;
+
+	default:
+		break;
+	}
+}
+
+void mptcp_get_options(const struct sk_buff *skb,
+		       struct mptcp_options_received *mp_opt)
+{
+	const struct tcphdr *th = tcp_hdr(skb);
+	const unsigned char *ptr;
+	int length;
+
+	/* Ensure that casting the whole status to u32 is efficient and safe */
+	BUILD_BUG_ON(sizeof_field(struct mptcp_options_received, status) != sizeof(u32));
+	BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct mptcp_options_received, status),
+				 sizeof(u32)));
+	*(u32 *)&mp_opt->status = 0;
+
+	length = (th->doff * 4) - sizeof(struct tcphdr);
+	ptr = (const unsigned char *)(th + 1);
+
+	while (length > 0) {
+		int opcode = *ptr++;
+		int opsize;
+
+		switch (opcode) {
+		case TCPOPT_EOL:
+			return;
+		case TCPOPT_NOP:	/* Ref: RFC 793 section 3.1 */
+			length--;
+			continue;
+		default:
+			if (length < 2)
+				return;
+			opsize = *ptr++;
+			if (opsize < 2) /* "silly options" */
+				return;
+			if (opsize > length)
+				return;	/* don't parse partial options */
+			if (opcode == TCPOPT_MPTCP)
+				mptcp_parse_option(skb, ptr, opsize, mp_opt);
+			ptr += opsize - 2;
+			length -= opsize;
+		}
+	}
+}
+
+bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
+		       unsigned int *size, struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	/* we will use snd_isn to detect first pkt [re]transmission
+	 * in mptcp_established_options_mp()
+	 */
+	subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
+	if (subflow->request_mptcp) {
+		if (unlikely(subflow_simultaneous_connect(sk))) {
+			WARN_ON_ONCE(!mptcp_try_fallback(sk, MPTCP_MIB_SIMULTCONNFALLBACK));
+
+			/* Ensure mptcp_finish_connect() will not process the
+			 * MPC handshake.
+			 */
+			subflow->request_mptcp = 0;
+			return false;
+		}
+
+		opts->suboptions = OPTION_MPTCP_MPC_SYN;
+		opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
+		opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
+		*size = TCPOLEN_MPTCP_MPC_SYN;
+		return true;
+	} else if (subflow->request_join) {
+		pr_debug("remote_token=%u, nonce=%u\n", subflow->remote_token,
+			 subflow->local_nonce);
+		opts->suboptions = OPTION_MPTCP_MPJ_SYN;
+		opts->join_id = subflow->local_id;
+		opts->token = subflow->remote_token;
+		opts->nonce = subflow->local_nonce;
+		opts->backup = subflow->request_bkup;
+		*size = TCPOLEN_MPTCP_MPJ_SYN;
+		return true;
+	}
+	return false;
+}
+
+static void clear_3rdack_retransmission(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	sk_stop_timer(sk, &icsk->icsk_delack_timer);
+	icsk->icsk_ack.ato = 0;
+	icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
+}
+
+static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
+					 bool snd_data_fin_enable, int *size,
+					 struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct mptcp_ext *mpext;
+	unsigned int data_len;
+	u8 len;
+
+	/* When skb is not available, we better over-estimate the emitted
+	 * options len. A full DSS option (28 bytes) is longer than
+	 * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
+	 * tell the caller to defer the estimate to
+	 * mptcp_established_options_dss(), which will reserve enough space.
+	 */
+	if (!skb)
+		return false;
+
+	/* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
+	if (subflow->fully_established || snd_data_fin_enable ||
+	    subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
+	    sk->sk_state != TCP_ESTABLISHED)
+		return false;
+
+	if (subflow->mp_capable) {
+		mpext = mptcp_get_ext(skb);
+		data_len = mpext ? mpext->data_len : 0;
+
+		/* we will check ops->data_len in mptcp_write_options() to
+		 * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
+		 * TCPOLEN_MPTCP_MPC_ACK
+		 */
+		opts->data_len = data_len;
+		opts->suboptions = OPTION_MPTCP_MPC_ACK;
+		opts->sndr_key = subflow->local_key;
+		opts->rcvr_key = subflow->remote_key;
+		opts->csum_reqd = READ_ONCE(msk->csum_enabled);
+		opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
+
+		/* Section 3.1.
+		 * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
+		 * packets that start the first subflow of an MPTCP connection,
+		 * as well as the first packet that carries data
+		 */
+		if (data_len > 0) {
+			len = TCPOLEN_MPTCP_MPC_ACK_DATA;
+			if (opts->csum_reqd) {
+				/* we need to propagate more info to csum the pseudo hdr */
+				opts->data_seq = mpext->data_seq;
+				opts->subflow_seq = mpext->subflow_seq;
+				opts->csum = mpext->csum;
+				len += TCPOLEN_MPTCP_DSS_CHECKSUM;
+			}
+			*size = ALIGN(len, 4);
+		} else {
+			*size = TCPOLEN_MPTCP_MPC_ACK;
+		}
+
+		pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d\n",
+			 subflow, subflow->local_key, subflow->remote_key,
+			 data_len);
+
+		return true;
+	} else if (subflow->mp_join) {
+		opts->suboptions = OPTION_MPTCP_MPJ_ACK;
+		memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
+		*size = TCPOLEN_MPTCP_MPJ_ACK;
+		pr_debug("subflow=%p\n", subflow);
+
+		/* we can use the full delegate action helper only from BH context
+		 * If we are in process context - sk is flushing the backlog at
+		 * socket lock release time - just set the appropriate flag, will
+		 * be handled by the release callback
+		 */
+		if (sock_owned_by_user(sk))
+			set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
+		else
+			mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
+		return true;
+	}
+	return false;
+}
+
+static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
+				 struct sk_buff *skb, struct mptcp_ext *ext)
+{
+	/* The write_seq value has already been incremented, so the actual
+	 * sequence number for the DATA_FIN is one less.
+	 */
+	u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
+
+	if (!ext->use_map || !skb->len) {
+		/* RFC6824 requires a DSS mapping with specific values
+		 * if DATA_FIN is set but no data payload is mapped
+		 */
+		ext->data_fin = 1;
+		ext->use_map = 1;
+		ext->dsn64 = 1;
+		ext->data_seq = data_fin_tx_seq;
+		ext->subflow_seq = 0;
+		ext->data_len = 1;
+		ext->csum = 0;
+	} else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
+		/* If there's an existing DSS mapping and it is the
+		 * final mapping, DATA_FIN consumes 1 additional byte of
+		 * mapping space.
+		 */
+		ext->data_fin = 1;
+		ext->data_len++;
+	}
+}
+
+static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
+					  bool snd_data_fin_enable, int *size,
+					  struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct tcp_sock *tp = tcp_sk(sk);
+	unsigned int dss_size = 0;
+	struct mptcp_ext *mpext;
+	unsigned int ack_size;
+	bool ret = false;
+
+	/* Zero `use_ack` and `use_map` flags with one shot. */
+	memset(&opts->ext_copy.flags, 0, sizeof(opts->ext_copy.flags));
+	opts->csum_reqd = READ_ONCE(msk->csum_enabled);
+	mpext = skb ? mptcp_get_ext(skb) : NULL;
+
+	if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
+		unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
+
+		if (mpext) {
+			if (opts->csum_reqd)
+				map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
+
+			opts->ext_copy = *mpext;
+		}
+
+		dss_size = map_size;
+		if (skb && snd_data_fin_enable)
+			mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
+		opts->suboptions = OPTION_MPTCP_DSS;
+		ret = true;
+	}
+
+	/* passive sockets msk will set the 'can_ack' after accept(), even
+	 * if the first subflow may have the already the remote key handy
+	 */
+	if (!READ_ONCE(msk->can_ack)) {
+		*size = ALIGN(dss_size, 4);
+		return ret;
+	}
+
+	if (READ_ONCE(msk->use_64bit_ack)) {
+		ack_size = TCPOLEN_MPTCP_DSS_ACK64;
+		opts->ext_copy.ack64 = 1;
+	} else {
+		ack_size = TCPOLEN_MPTCP_DSS_ACK32;
+		opts->ext_copy.ack64 = 0;
+	}
+	opts->ext_copy.use_ack = 1;
+	opts->suboptions = OPTION_MPTCP_DSS;
+
+	/* Add kind/length/subtype/flag overhead if mapping is not populated */
+	if (dss_size == 0)
+		ack_size += TCPOLEN_MPTCP_DSS_BASE;
+
+	/* The caller is __tcp_transmit_skb(), and will compute the new rcv
+	 * wnd soon: ensure that the window can shrink.
+	 */
+	if (skb)
+		tp->rcv_wnd = tp->rcv_nxt - tp->rcv_wup;
+
+	dss_size += ack_size;
+
+	*size = ALIGN(dss_size, 4);
+	return true;
+}
+
+static u64 add_addr_generate_hmac(u64 key1, u64 key2,
+				  struct mptcp_addr_info *addr)
+{
+	u16 port = ntohs(addr->port);
+	u8 hmac[SHA256_DIGEST_SIZE];
+	u8 msg[19];
+	int i = 0;
+
+	msg[i++] = addr->id;
+	if (addr->family == AF_INET) {
+		memcpy(&msg[i], &addr->addr.s_addr, 4);
+		i += 4;
+	}
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (addr->family == AF_INET6) {
+		memcpy(&msg[i], &addr->addr6.s6_addr, 16);
+		i += 16;
+	}
+#endif
+	msg[i++] = port >> 8;
+	msg[i++] = port & 0xFF;
+
+	mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
+
+	return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
+}
+
+static bool mptcp_established_options_add_addr(struct sock *sk,
+					       struct sk_buff *skb, int *size,
+					       unsigned int remaining,
+					       bool has_ts,
+					       struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct mptcp_addr_info addr;
+	bool drop_ts = has_ts;
+	bool echo;
+
+	/* add addr will strip the existing options, be sure to avoid breaking
+	 * MPC/MPJ handshakes
+	 */
+	if (!mptcp_pm_should_add_signal(msk) ||
+	    (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
+	    !skb || !skb_is_tcp_pure_ack(skb) ||
+	    !mptcp_pm_add_addr_signal(msk, size, remaining, &addr, &echo,
+				      &drop_ts))
+		return false;
+
+	pr_debug("drop other suboptions\n");
+	opts->suboptions = OPTION_MPTCP_ADD_ADDR;
+	opts->drop_ts = drop_ts;
+	opts->addr = addr;
+	if (!echo) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
+		opts->ahmac = add_addr_generate_hmac(READ_ONCE(msk->local_key),
+						     READ_ONCE(msk->remote_key),
+						     &opts->addr);
+	} else {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX);
+		opts->ahmac = 0;
+	}
+	pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d\n",
+		 opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
+
+	return true;
+}
+
+static bool mptcp_established_options_rm_addr(struct sock *sk, int *size,
+					      unsigned int remaining,
+					      struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct mptcp_rm_list rm_list;
+	int i;
+
+	if (!mptcp_pm_should_rm_signal(msk) ||
+	    !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list, size)))
+		return false;
+
+	opts->suboptions |= OPTION_MPTCP_RM_ADDR;
+	opts->rm_list = rm_list;
+
+	for (i = 0; i < opts->rm_list.nr; i++)
+		pr_debug("rm_list_ids[%d]=%d\n", i, opts->rm_list.ids[i]);
+	MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RMADDRTX, opts->rm_list.nr);
+	return true;
+}
+
+static bool mptcp_established_options_mp_prio(struct sock *sk, int *size,
+					      unsigned int remaining,
+					      struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	/* can't send MP_PRIO with MPC, as they share the same option space:
+	 * 'backup'. Also it makes no sense at all
+	 */
+	if (!subflow->send_mp_prio || (opts->suboptions & OPTIONS_MPTCP_MPC))
+		return false;
+
+	/* account for the trailing 'nop' option */
+	if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
+		return false;
+
+	*size = TCPOLEN_MPTCP_PRIO_ALIGN;
+	opts->suboptions |= OPTION_MPTCP_PRIO;
+	opts->backup = subflow->request_bkup;
+
+	pr_debug("prio=%d\n", opts->backup);
+
+	return true;
+}
+
+static noinline bool mptcp_established_options_rst(struct sock *sk,
+						   int *size,
+						   unsigned int remaining,
+						   struct mptcp_out_options *opts)
+{
+	const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	if (remaining < TCPOLEN_MPTCP_RST)
+		return false;
+
+	*size = TCPOLEN_MPTCP_RST;
+	opts->suboptions |= OPTION_MPTCP_RST;
+	opts->reset_transient = subflow->reset_transient;
+	opts->reset_reason = subflow->reset_reason;
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTTX);
+
+	return true;
+}
+
+static bool mptcp_established_options_fastclose(struct sock *sk, int *size,
+						unsigned int remaining,
+						struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+
+	if (likely(!subflow->send_fastclose))
+		return false;
+
+	if (remaining < TCPOLEN_MPTCP_FASTCLOSE)
+		return false;
+
+	*size = TCPOLEN_MPTCP_FASTCLOSE;
+	opts->suboptions |= OPTION_MPTCP_FASTCLOSE;
+	opts->rcvr_key = READ_ONCE(msk->remote_key);
+
+	pr_debug("FASTCLOSE key=%llu\n", opts->rcvr_key);
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX);
+	return true;
+}
+
+static bool mptcp_established_options_mp_fail(struct sock *sk, int *size,
+					      unsigned int remaining,
+					      struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	if (likely(!subflow->send_mp_fail))
+		return false;
+
+	if (remaining < TCPOLEN_MPTCP_FAIL)
+		return false;
+
+	*size = TCPOLEN_MPTCP_FAIL;
+	opts->suboptions |= OPTION_MPTCP_FAIL;
+	opts->fail_seq = subflow->map_seq;
+
+	pr_debug("MP_FAIL fail_seq=%llu\n", opts->fail_seq);
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
+
+	return true;
+}
+
+int mptcp_established_options(struct sock *sk, struct sk_buff *skb,
+			      unsigned int remaining, bool has_ts,
+			      struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	int total_size = 0;
+	bool snd_data_fin;
+	bool ret = false;
+	int opt_size = 0;
+
+	opts->suboptions = 0;
+
+	/* Force later mptcp_write_options(), but do not use any actual
+	 * option space.
+	 */
+	if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
+		return 0;
+
+	if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
+		if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
+		    mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
+			total_size += opt_size;
+			remaining -= opt_size;
+		}
+		/* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
+		if (mptcp_established_options_rst(sk, &opt_size, remaining, opts)) {
+			total_size += opt_size;
+			remaining -= opt_size;
+		}
+		return total_size;
+	}
+
+	snd_data_fin = mptcp_data_fin_enabled(msk);
+	if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, opts))
+		ret = true;
+	else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, opts)) {
+		int mp_fail_size;
+
+		ret = true;
+		if (mptcp_established_options_mp_fail(sk, &mp_fail_size,
+						      remaining - opt_size, opts)) {
+			total_size += opt_size + mp_fail_size;
+			remaining -= opt_size - mp_fail_size;
+			return total_size;
+		}
+	}
+
+	/* we reserved enough space for the above options, and exceeding the
+	 * TCP option space would be fatal
+	 */
+	if (WARN_ON_ONCE(opt_size > remaining))
+		return -1;
+
+	total_size += opt_size;
+	remaining -= opt_size;
+	if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining,
+					       has_ts, opts)) {
+		total_size += opt_size;
+		remaining -= opt_size;
+		ret = true;
+	} else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
+		total_size += opt_size;
+		remaining -= opt_size;
+		ret = true;
+	}
+
+	if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
+		total_size += opt_size;
+		remaining -= opt_size;
+		ret = true;
+	}
+
+	return ret ? total_size : -1;
+}
+
+bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
+			  struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+
+	if (subflow_req->mp_capable) {
+		opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
+		opts->sndr_key = subflow_req->local_key;
+		opts->csum_reqd = subflow_req->csum_reqd;
+		opts->allow_join_id0 = subflow_req->allow_join_id0;
+		*size = TCPOLEN_MPTCP_MPC_SYNACK;
+		pr_debug("subflow_req=%p, local_key=%llu\n",
+			 subflow_req, subflow_req->local_key);
+		return true;
+	} else if (subflow_req->mp_join) {
+		opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
+		opts->backup = subflow_req->request_bkup;
+		opts->join_id = subflow_req->local_id;
+		opts->thmac = subflow_req->thmac;
+		opts->nonce = subflow_req->local_nonce;
+		pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u\n",
+			 subflow_req, opts->backup, opts->join_id,
+			 opts->thmac, opts->nonce);
+		*size = TCPOLEN_MPTCP_MPJ_SYNACK;
+		return true;
+	}
+	return false;
+}
+
+static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
+				    struct mptcp_subflow_context *subflow,
+				    struct sk_buff *skb,
+				    struct mptcp_options_received *mp_opt)
+{
+	/* here we can process OoO, in-window pkts, only in-sequence 4th ack
+	 * will make the subflow fully established
+	 */
+	if (likely(subflow->fully_established)) {
+		/* on passive sockets, check for 3rd ack retransmission
+		 * note that msk is always set by subflow_syn_recv_sock()
+		 * for mp_join subflows
+		 */
+		if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
+		    TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
+		    subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
+		    !subflow->request_join)
+			tcp_send_ack(ssk);
+		goto check_notify;
+	}
+
+	/* we must process OoO packets before the first subflow is fully
+	 * established. OoO packets are instead a protocol violation
+	 * for MP_JOIN subflows as the peer must not send any data
+	 * before receiving the forth ack - cfr. RFC 8684 section 3.2.
+	 */
+	if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
+		if (subflow->mp_join)
+			goto reset;
+		if (subflow->is_mptfo && mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
+			goto set_fully_established;
+		return subflow->mp_capable;
+	}
+
+	if (subflow->remote_key_valid &&
+	    (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
+	     ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) &&
+	      (!mp_opt->echo || subflow->mp_join)))) {
+		/* subflows are fully established as soon as we get any
+		 * additional ack, including ADD_ADDR.
+		 */
+		goto set_fully_established;
+	}
+
+	/* If the first established packet does not contain MP_CAPABLE + data
+	 * then fallback to TCP. Fallback scenarios requires a reset for
+	 * MP_JOIN subflows.
+	 */
+	if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
+		if (subflow->mp_join)
+			goto reset;
+		subflow->mp_capable = 0;
+		if (!mptcp_try_fallback(ssk, MPTCP_MIB_MPCAPABLEDATAFALLBACK)) {
+			MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_FALLBACKFAILED);
+			goto reset;
+		}
+		return false;
+	}
+
+	if (unlikely(!READ_ONCE(msk->pm.server_side)))
+		pr_warn_once("bogus mpc option on established client sk");
+
+set_fully_established:
+	if (mp_opt->deny_join_id0)
+		WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
+
+	mptcp_data_lock((struct sock *)msk);
+	__mptcp_subflow_fully_established(msk, subflow, mp_opt);
+	mptcp_data_unlock((struct sock *)msk);
+
+check_notify:
+	/* if the subflow is not already linked into the conn_list, we can't
+	 * notify the PM: this subflow is still on the listener queue
+	 * and the PM possibly acquiring the subflow lock could race with
+	 * the listener close
+	 */
+	if (likely(subflow->pm_notified) || list_empty(&subflow->node))
+		return true;
+
+	subflow->pm_notified = 1;
+	if (subflow->mp_join) {
+		clear_3rdack_retransmission(ssk);
+		mptcp_pm_subflow_established(msk);
+	} else {
+		mptcp_pm_fully_established(msk, ssk);
+	}
+	return true;
+
+reset:
+	mptcp_subflow_reset(ssk);
+	return false;
+}
+
+u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
+{
+	u32 old_seq32, cur_seq32;
+
+	old_seq32 = (u32)old_seq;
+	cur_seq32 = (u32)cur_seq;
+	cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
+	if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
+		return cur_seq + (1LL << 32);
+
+	/* reverse wrap could happen, too */
+	if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
+		return cur_seq - (1LL << 32);
+	return cur_seq;
+}
+
+static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
+{
+	msk->bytes_acked += new_snd_una - msk->snd_una;
+	WRITE_ONCE(msk->snd_una, new_snd_una);
+}
+
+static void rwin_update(struct mptcp_sock *msk, struct sock *ssk,
+			struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct tcp_sock *tp = tcp_sk(ssk);
+	u64 mptcp_rcv_wnd;
+
+	/* Avoid touching extra cachelines if TCP is going to accept this
+	 * skb without filling the TCP-level window even with a possibly
+	 * outdated mptcp-level rwin.
+	 */
+	if (!skb->len || skb->len < tcp_receive_window(tp))
+		return;
+
+	mptcp_rcv_wnd = atomic64_read(&msk->rcv_wnd_sent);
+	if (!after64(mptcp_rcv_wnd, subflow->rcv_wnd_sent))
+		return;
+
+	/* Some other subflow grew the mptcp-level rwin since rcv_wup,
+	 * resync.
+	 */
+	tp->rcv_wnd += mptcp_rcv_wnd - subflow->rcv_wnd_sent;
+	tcp_update_max_rcv_wnd_seq(tp);
+	subflow->rcv_wnd_sent = mptcp_rcv_wnd;
+}
+
+static void ack_update_msk(struct mptcp_sock *msk,
+			   struct sock *ssk,
+			   struct mptcp_options_received *mp_opt)
+{
+	u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
+	struct sock *sk = (struct sock *)msk;
+	u64 old_snd_una;
+
+	mptcp_data_lock(sk);
+
+	/* avoid ack expansion on update conflict, to reduce the risk of
+	 * wrongly expanding to a future ack sequence number, which is way
+	 * more dangerous than missing an ack
+	 */
+	old_snd_una = msk->snd_una;
+	new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
+
+	/* ACK for data not even sent yet? Ignore.*/
+	if (unlikely(after64(new_snd_una, snd_nxt)))
+		new_snd_una = old_snd_una;
+
+	new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
+
+	if (after64(new_wnd_end, msk->wnd_end))
+		WRITE_ONCE(msk->wnd_end, new_wnd_end);
+
+	/* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
+	if (after64(msk->wnd_end, snd_nxt))
+		__mptcp_check_push(sk, ssk);
+
+	if (after64(new_snd_una, old_snd_una)) {
+		__mptcp_snd_una_update(msk, new_snd_una);
+		__mptcp_data_acked(sk);
+	}
+	msk->last_ack_recv = tcp_jiffies32;
+	mptcp_data_unlock(sk);
+
+	trace_ack_update_msk(mp_opt->data_ack,
+			     old_snd_una, new_snd_una,
+			     new_wnd_end, READ_ONCE(msk->wnd_end));
+}
+
+bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
+{
+	/* Skip if DATA_FIN was already received.
+	 * If updating simultaneously with the recvmsg loop, values
+	 * should match. If they mismatch, the peer is misbehaving and
+	 * we will prefer the most recent information.
+	 */
+	if (READ_ONCE(msk->rcv_data_fin))
+		return false;
+
+	WRITE_ONCE(msk->rcv_data_fin_seq,
+		   mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
+	WRITE_ONCE(msk->rcv_data_fin, 1);
+
+	return true;
+}
+
+static bool add_addr_hmac_valid(struct mptcp_sock *msk,
+				struct mptcp_options_received *mp_opt)
+{
+	u64 hmac = 0;
+
+	if (mp_opt->echo)
+		return true;
+
+	hmac = add_addr_generate_hmac(READ_ONCE(msk->remote_key),
+				      READ_ONCE(msk->local_key),
+				      &mp_opt->addr);
+
+	pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
+		 msk, hmac, mp_opt->ahmac);
+
+	return hmac == mp_opt->ahmac;
+}
+
+static bool mptcp_over_limit(struct sock *sk, struct sock *ssk,
+			     const struct sk_buff *skb)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	u32 rcvbuf = READ_ONCE(sk->sk_rcvbuf);
+
+	if (likely((u32)sk_rmem_alloc_get(sk) <= rcvbuf &&
+		   READ_ONCE(msk->backlog_len) <= rcvbuf))
+		return false;
+
+	/* Avoid silently dropping pure acks, fin, rst or already-acked segm. */
+	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq ||
+	    TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_FIN | TCPHDR_RST) ||
+	    !after(TCP_SKB_CB(skb)->end_seq, tcp_sk(ssk)->rcv_nxt))
+		return false;
+
+	/* Dropped due to memory constraints, schedule an ack. */
+	inet_csk(ssk)->icsk_ack.pending |= ICSK_ACK_NOMEM | ICSK_ACK_NOW;
+	inet_csk_schedule_ack(ssk);
+
+	/* Plain TCP (fallback) and skb is dropped before the TCP recv queue. */
+	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP);
+
+	return true;
+}
+
+/* Return false when the caller must drop the packet, i.e. in case of error,
+ * subflow has been reset, or over memory limits.
+ */
+bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct mptcp_options_received mp_opt;
+	struct mptcp_ext *mpext;
+
+	if (__mptcp_check_fallback(msk)) {
+		/* Keep it simple and unconditionally trigger send data cleanup and
+		 * pending queue spooling. We will need to acquire the data lock
+		 * for more accurate checks, and once the lock is acquired, such
+		 * helpers are cheap.
+		 */
+		mptcp_data_lock(subflow->conn);
+		if (sk_stream_memory_free(sk))
+			__mptcp_check_push(subflow->conn, sk);
+
+		/* on fallback we just need to ignore the msk-level snd_una, as
+		 * this is really plain TCP
+		 */
+		__mptcp_snd_una_update(msk, READ_ONCE(msk->snd_nxt));
+
+		__mptcp_data_acked(subflow->conn);
+		mptcp_data_unlock(subflow->conn);
+		return !mptcp_over_limit(subflow->conn, sk, skb);
+	}
+
+	mptcp_get_options(skb, &mp_opt);
+
+	/* The subflow can be in close state only if check_fully_established()
+	 * just sent a reset. If so, tell the caller to ignore the current packet.
+	 */
+	if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
+		return sk->sk_state != TCP_CLOSE;
+
+	if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
+		if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
+		    READ_ONCE(msk->local_key) == mp_opt.rcvr_key) {
+			WRITE_ONCE(msk->rcv_fastclose, true);
+			mptcp_schedule_work((struct sock *)msk);
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);
+		}
+
+		if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
+		    add_addr_hmac_valid(msk, &mp_opt)) {
+			if (!mp_opt.echo) {
+				mptcp_pm_add_addr_received(sk, &mp_opt.addr);
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
+			} else {
+				mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
+			}
+
+			if (mp_opt.addr.port)
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
+		}
+
+		if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
+			mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
+
+		if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
+			mptcp_pm_mp_prio_received(sk, mp_opt.backup);
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
+		}
+
+		if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
+			mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
+		}
+
+		if (mp_opt.suboptions & OPTION_MPTCP_RST) {
+			subflow->reset_seen = 1;
+			subflow->reset_reason = mp_opt.reset_reason;
+			subflow->reset_transient = mp_opt.reset_transient;
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX);
+		}
+
+		if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
+			return true;
+	}
+
+	/* we can't wait for recvmsg() to update the ack_seq, otherwise
+	 * monodirectional flows will stuck
+	 */
+	if (mp_opt.use_ack)
+		ack_update_msk(msk, sk, &mp_opt);
+	rwin_update(msk, sk, skb);
+
+	/* Zero-data-length packets are dropped by the caller and not
+	 * propagated to the MPTCP layer, so the skb extension does not
+	 * need to be allocated or populated. DATA_FIN information, if
+	 * present, needs to be updated here before the skb is freed.
+	 */
+	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
+		if (mp_opt.data_fin && mp_opt.data_len == 1 &&
+		    mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64))
+			mptcp_schedule_work((struct sock *)msk);
+
+		return true;
+	}
+
+	mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
+	if (!mpext)
+		return false;
+
+	memset(mpext, 0, sizeof(*mpext));
+
+	if (likely(mp_opt.use_map)) {
+		if (mp_opt.mpc_map) {
+			/* this is an MP_CAPABLE carrying MPTCP data
+			 * we know this map the first chunk of data
+			 */
+			mptcp_crypto_key_sha(subflow->remote_key, NULL,
+					     &mpext->data_seq);
+			mpext->data_seq++;
+			mpext->subflow_seq = 1;
+			mpext->dsn64 = 1;
+			mpext->mpc_map = 1;
+			mpext->data_fin = 0;
+		} else {
+			mpext->data_seq = mp_opt.data_seq;
+			mpext->subflow_seq = mp_opt.subflow_seq;
+			mpext->dsn64 = mp_opt.dsn64;
+			mpext->data_fin = mp_opt.data_fin;
+		}
+		mpext->data_len = mp_opt.data_len;
+		mpext->use_map = 1;
+		mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
+
+		if (mpext->csum_reqd)
+			mpext->csum = mp_opt.csum;
+	}
+
+	return true;
+}
+
+static u64 mptcp_set_rwin(struct mptcp_sock *msk, struct tcp_sock *tp,
+			  struct tcphdr *th, u64 ack_seq)
+{
+	const struct sock *ssk = (const struct sock *)tp;
+	u64 rcv_wnd_old, rcv_wnd_new;
+	u32 new_win;
+	u64 win;
+
+	rcv_wnd_new = ack_seq + tp->rcv_wnd;
+
+	rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent);
+	if (after64(rcv_wnd_new, rcv_wnd_old)) {
+		u64 rcv_wnd;
+
+		for (;;) {
+			rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new);
+
+			if (rcv_wnd == rcv_wnd_old)
+				break;
+
+			rcv_wnd_old = rcv_wnd;
+			if (before64(rcv_wnd_new, rcv_wnd_old)) {
+				MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
+				goto raise_win;
+			}
+			MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
+		}
+		goto update_wspace;
+	}
+
+	if (rcv_wnd_new != rcv_wnd_old) {
+raise_win:
+		/* The msk-level rcv wnd is after the tcp level one,
+		 * sync the latter.
+		 */
+		rcv_wnd_new = rcv_wnd_old;
+		win = rcv_wnd_old - ack_seq;
+		new_win = min_t(u64, win, U32_MAX);
+		tp->rcv_wnd = new_win;
+		tcp_update_max_rcv_wnd_seq(tp);
+
+		/* Make sure we do not exceed the maximum possible
+		 * scaled window.
+		 */
+		if (unlikely(th->syn))
+			new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale;
+		if (!tp->rx_opt.rcv_wscale &&
+		    READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows))
+			new_win = min(new_win, MAX_TCP_WINDOW);
+		else
+			new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
+
+		/* RFC1323 scaling applied */
+		new_win >>= tp->rx_opt.rcv_wscale;
+		th->window = htons(new_win);
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED);
+	}
+
+update_wspace:
+	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
+	return rcv_wnd_new;
+}
+
+static void mptcp_track_rwin(struct tcp_sock *tp)
+{
+	const struct sock *ssk = (const struct sock *)tp;
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk;
+
+	if (!ssk)
+		return;
+
+	subflow = mptcp_subflow_ctx(ssk);
+	msk = mptcp_sk(subflow->conn);
+	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
+}
+
+__sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
+{
+	struct csum_pseudo_header header;
+	__wsum csum;
+
+	/* cfr RFC 8684 3.3.1.:
+	 * the data sequence number used in the pseudo-header is
+	 * always the 64-bit value, irrespective of what length is used in the
+	 * DSS option itself.
+	 */
+	header.data_seq = cpu_to_be64(data_seq);
+	header.subflow_seq = htonl(subflow_seq);
+	header.data_len = htons(data_len);
+	header.csum = 0;
+
+	csum = csum_partial(&header, sizeof(header), sum);
+	return csum_fold(csum);
+}
+
+static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
+{
+	return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
+				 ~csum_unfold(mpext->csum));
+}
+
+static void put_len_csum(u16 len, __sum16 csum, void *data)
+{
+	__sum16 *sumptr = data + 2;
+	__be16 *ptr = data;
+
+	put_unaligned_be16(len, ptr);
+
+	put_unaligned(csum, sumptr);
+}
+
+void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
+			 struct mptcp_out_options *opts)
+{
+	const struct sock *ssk = (const struct sock *)tp;
+	struct mptcp_subflow_context *subflow;
+
+	/* Which options can be used together?
+	 *
+	 * X: mutually exclusive
+	 * O: often used together
+	 * C: can be used together in some cases
+	 * P: could be used together but we prefer not to (optimisations)
+	 *
+	 *  Opt: | MPC  | MPJ  | DSS  | ADD  |  RM  | PRIO | FAIL |  FC  |
+	 * ------|------|------|------|------|------|------|------|------|
+	 *  MPC  |------|------|------|------|------|------|------|------|
+	 *  MPJ  |  X   |------|------|------|------|------|------|------|
+	 *  DSS  |  X   |  X   |------|------|------|------|------|------|
+	 *  ADD  |  X   |  X   |  P   |------|------|------|------|------|
+	 *  RM   |  C   |  C   |  C   |  P   |------|------|------|------|
+	 *  PRIO |  X   |  C   |  C   |  C   |  C   |------|------|------|
+	 *  FAIL |  X   |  X   |  C   |  X   |  X   |  X   |------|------|
+	 *  FC   |  X   |  X   |  P   |  X   |  X   |  X   |  X   |------|
+	 *  RST  |  X   |  X   |  X   |  X   |  X   |  X   |  O   |  O   |
+	 * ------|------|------|------|------|------|------|------|------|
+	 *
+	 * The same applies in mptcp_established_options() function.
+	 */
+	if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
+		struct mptcp_ext *mpext = &opts->ext_copy;
+		u8 len = TCPOLEN_MPTCP_DSS_BASE;
+		u8 flags = 0;
+
+		if (mpext->use_ack) {
+			flags = MPTCP_DSS_HAS_ACK;
+			if (mpext->ack64) {
+				len += TCPOLEN_MPTCP_DSS_ACK64;
+				flags |= MPTCP_DSS_ACK64;
+			} else {
+				len += TCPOLEN_MPTCP_DSS_ACK32;
+			}
+		}
+
+		if (mpext->use_map) {
+			len += TCPOLEN_MPTCP_DSS_MAP64;
+
+			/* Use only 64-bit mapping flags for now, add
+			 * support for optional 32-bit mappings later.
+			 */
+			flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
+			if (mpext->data_fin)
+				flags |= MPTCP_DSS_DATA_FIN;
+
+			if (opts->csum_reqd)
+				len += TCPOLEN_MPTCP_DSS_CHECKSUM;
+		}
+
+		*ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
+
+		if (mpext->use_ack) {
+			struct mptcp_sock *msk;
+			u64 ack_seq;
+
+			/* DSS option is set only by mptcp_established_options,
+			 * the caller is __tcp_transmit_skb() and ssk is always
+			 * not NULL.
+			 */
+			subflow = mptcp_subflow_ctx(ssk);
+			msk = mptcp_sk(subflow->conn);
+			ack_seq = READ_ONCE(msk->ack_seq);
+			if (mpext->ack64) {
+				put_unaligned_be64(ack_seq, ptr);
+				ptr += 2;
+			} else {
+				put_unaligned_be32(ack_seq, ptr);
+				ptr += 1;
+			}
+			subflow->rcv_wnd_sent = mptcp_set_rwin(msk, tp, th,
+							       ack_seq);
+		}
+
+		if (mpext->use_map) {
+			put_unaligned_be64(mpext->data_seq, ptr);
+			ptr += 2;
+			put_unaligned_be32(mpext->subflow_seq, ptr);
+			ptr += 1;
+			if (opts->csum_reqd) {
+				/* data_len == 0 is reserved for the infinite mapping,
+				 * the checksum will also be set to 0.
+				 */
+				put_len_csum(mpext->data_len,
+					     (mpext->data_len ? mptcp_make_csum(mpext) : 0),
+					     ptr);
+			} else {
+				put_unaligned_be32(mpext->data_len << 16 |
+						   TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
+			}
+			ptr += 1;
+		}
+
+		/* We might need to add MP_FAIL options in rare cases */
+		if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions))
+			goto mp_fail;
+	} else if (OPTIONS_MPTCP_MPC & opts->suboptions) {
+		u8 len, flag = MPTCP_CAP_HMAC_SHA256;
+
+		if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
+			len = TCPOLEN_MPTCP_MPC_SYN;
+		} else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
+			len = TCPOLEN_MPTCP_MPC_SYNACK;
+		} else if (opts->data_len) {
+			len = TCPOLEN_MPTCP_MPC_ACK_DATA;
+			if (opts->csum_reqd)
+				len += TCPOLEN_MPTCP_DSS_CHECKSUM;
+		} else {
+			len = TCPOLEN_MPTCP_MPC_ACK;
+		}
+
+		if (opts->csum_reqd)
+			flag |= MPTCP_CAP_CHECKSUM_REQD;
+
+		if (!opts->allow_join_id0)
+			flag |= MPTCP_CAP_DENY_JOIN_ID0;
+
+		*ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
+				      MPTCP_SUPPORTED_VERSION,
+				      flag);
+
+		if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
+		    opts->suboptions))
+			goto mp_capable_done;
+
+		put_unaligned_be64(opts->sndr_key, ptr);
+		ptr += 2;
+		if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
+			goto mp_capable_done;
+
+		put_unaligned_be64(opts->rcvr_key, ptr);
+		ptr += 2;
+		if (!opts->data_len)
+			goto mp_capable_done;
+
+		if (opts->csum_reqd) {
+			put_len_csum(opts->data_len,
+				     __mptcp_make_csum(opts->data_seq,
+						       opts->subflow_seq,
+						       opts->data_len,
+						       ~csum_unfold(opts->csum)),
+				     ptr);
+		} else {
+			put_unaligned_be32(opts->data_len << 16 |
+					   TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
+		}
+		ptr += 1;
+
+		/* MPC is additionally mutually exclusive with MP_PRIO */
+		goto mp_capable_done;
+	} else if (OPTIONS_MPTCP_MPJ & opts->suboptions) {
+		if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
+			*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
+					      TCPOLEN_MPTCP_MPJ_SYN,
+					      opts->backup, opts->join_id);
+			put_unaligned_be32(opts->token, ptr);
+			ptr += 1;
+			put_unaligned_be32(opts->nonce, ptr);
+			ptr += 1;
+		} else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
+			*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
+					      TCPOLEN_MPTCP_MPJ_SYNACK,
+					      opts->backup, opts->join_id);
+			put_unaligned_be64(opts->thmac, ptr);
+			ptr += 2;
+			put_unaligned_be32(opts->nonce, ptr);
+			ptr += 1;
+		} else {
+			*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
+					      TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
+			memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
+			ptr += 5;
+		}
+	} else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
+		u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
+		u8 echo = MPTCP_ADDR_ECHO;
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+		if (opts->addr.family == AF_INET6)
+			len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
+#endif
+
+		if (opts->addr.port)
+			len += TCPOLEN_MPTCP_PORT_LEN;
+
+		if (opts->ahmac) {
+			len += sizeof(opts->ahmac);
+			echo = 0;
+		}
+
+		*ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
+				      len, echo, opts->addr.id);
+		if (opts->addr.family == AF_INET) {
+			memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
+			ptr += 1;
+		}
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+		else if (opts->addr.family == AF_INET6) {
+			memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
+			ptr += 4;
+		}
+#endif
+
+		if (!opts->addr.port) {
+			if (opts->ahmac) {
+				put_unaligned_be64(opts->ahmac, ptr);
+				ptr += 2;
+			}
+		} else {
+			u16 port = ntohs(opts->addr.port);
+
+			if (opts->ahmac) {
+				u8 *bptr = (u8 *)ptr;
+
+				put_unaligned_be16(port, bptr);
+				bptr += 2;
+				put_unaligned_be64(opts->ahmac, bptr);
+				bptr += 8;
+				put_unaligned_be16(TCPOPT_NOP << 8 |
+						   TCPOPT_NOP, bptr);
+
+				ptr += 3;
+			} else {
+				put_unaligned_be32(port << 16 |
+						   TCPOPT_NOP << 8 |
+						   TCPOPT_NOP, ptr);
+				ptr += 1;
+			}
+		}
+	} else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
+		/* FASTCLOSE is mutually exclusive with others except RST */
+		*ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
+				      TCPOLEN_MPTCP_FASTCLOSE,
+				      0, 0);
+		put_unaligned_be64(opts->rcvr_key, ptr);
+		ptr += 2;
+
+		if (OPTION_MPTCP_RST & opts->suboptions)
+			goto mp_rst;
+		return;
+	} else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
+mp_fail:
+		/* MP_FAIL is mutually exclusive with others except RST */
+		subflow = mptcp_subflow_ctx(ssk);
+		subflow->send_mp_fail = 0;
+
+		*ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
+				      TCPOLEN_MPTCP_FAIL,
+				      0, 0);
+		put_unaligned_be64(opts->fail_seq, ptr);
+		ptr += 2;
+
+		if (OPTION_MPTCP_RST & opts->suboptions)
+			goto mp_rst;
+		return;
+	} else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
+mp_rst:
+		*ptr++ = mptcp_option(MPTCPOPT_RST,
+				      TCPOLEN_MPTCP_RST,
+				      opts->reset_transient,
+				      opts->reset_reason);
+		return;
+	} else if (unlikely(!opts->suboptions)) {
+		/* Fallback to TCP */
+		mptcp_track_rwin(tp);
+		return;
+	}
+
+	if (OPTION_MPTCP_PRIO & opts->suboptions) {
+		subflow = mptcp_subflow_ctx(ssk);
+		subflow->send_mp_prio = 0;
+
+		*ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
+				      TCPOLEN_MPTCP_PRIO,
+				      opts->backup, TCPOPT_NOP);
+
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPPRIOTX);
+	}
+
+mp_capable_done:
+	if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
+		u8 i = 1;
+
+		*ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
+				      TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
+				      0, opts->rm_list.ids[0]);
+
+		while (i < opts->rm_list.nr) {
+			u8 id1, id2, id3, id4;
+
+			id1 = opts->rm_list.ids[i];
+			id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
+			id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
+			id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
+			put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
+			ptr += 1;
+			i += 4;
+		}
+	}
+}
+
+__be32 mptcp_get_reset_option(const struct sk_buff *skb)
+{
+	const struct mptcp_ext *ext = mptcp_get_ext(skb);
+	u8 flags, reason;
+
+	if (ext) {
+		flags = ext->reset_transient;
+		reason = ext->reset_reason;
+
+		return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
+				    flags, reason);
+	}
+
+	return htonl(0u);
+}
+EXPORT_SYMBOL_GPL(mptcp_get_reset_option);
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
new file mode 100644
index 000000000..b0b71adef
--- /dev/null
+++ b/net/mptcp/pm.c
@@ -0,0 +1,1287 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2019, Intel Corporation.
+ */
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/rculist.h>
+#include <linux/spinlock.h>
+#include "protocol.h"
+#include "mib.h"
+
+#define ADD_ADDR_RETRANS_MAX	3
+
+struct mptcp_pm_add_addr {
+	struct list_head	list;
+	struct mptcp_addr_info	addr;
+	u8			retrans_times;
+	bool			timer_done;
+	struct timer_list	timer;
+	struct mptcp_sock	*sock;
+	struct rcu_head		rcu;
+};
+
+static DEFINE_SPINLOCK(mptcp_pm_list_lock);
+static LIST_HEAD(mptcp_pm_list);
+
+/* path manager helpers */
+
+/* if sk is ipv4 or ipv6_only allows only same-family local and remote addresses,
+ * otherwise allow any matching local/remote pair
+ */
+bool mptcp_pm_addr_families_match(const struct sock *sk,
+				  const struct mptcp_addr_info *loc,
+				  const struct mptcp_addr_info *rem)
+{
+	bool mptcp_is_v4 = sk->sk_family == AF_INET;
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	bool loc_is_v4 = loc->family == AF_INET || ipv6_addr_v4mapped(&loc->addr6);
+	bool rem_is_v4 = rem->family == AF_INET || ipv6_addr_v4mapped(&rem->addr6);
+
+	if (mptcp_is_v4)
+		return loc_is_v4 && rem_is_v4;
+
+	if (ipv6_only_sock(sk))
+		return !loc_is_v4 && !rem_is_v4;
+
+	return loc_is_v4 == rem_is_v4;
+#else
+	return mptcp_is_v4 && loc->family == AF_INET && rem->family == AF_INET;
+#endif
+}
+
+bool mptcp_addresses_equal(const struct mptcp_addr_info *a,
+			   const struct mptcp_addr_info *b, bool use_port)
+{
+	bool addr_equals = false;
+
+	if (a->family == b->family) {
+		if (a->family == AF_INET)
+			addr_equals = a->addr.s_addr == b->addr.s_addr;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+		else
+			addr_equals = ipv6_addr_equal(&a->addr6, &b->addr6);
+	} else if (a->family == AF_INET) {
+		if (ipv6_addr_v4mapped(&b->addr6))
+			addr_equals = a->addr.s_addr == b->addr6.s6_addr32[3];
+	} else if (b->family == AF_INET) {
+		if (ipv6_addr_v4mapped(&a->addr6))
+			addr_equals = a->addr6.s6_addr32[3] == b->addr.s_addr;
+#endif
+	}
+
+	if (!addr_equals)
+		return false;
+	if (!use_port)
+		return true;
+
+	return a->port == b->port;
+}
+
+void mptcp_local_address(const struct sock_common *skc,
+			 struct mptcp_addr_info *addr)
+{
+	addr->family = skc->skc_family;
+	addr->port = htons(skc->skc_num);
+	if (addr->family == AF_INET)
+		addr->addr.s_addr = skc->skc_rcv_saddr;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (addr->family == AF_INET6)
+		addr->addr6 = skc->skc_v6_rcv_saddr;
+#endif
+}
+
+void mptcp_remote_address(const struct sock_common *skc,
+			  struct mptcp_addr_info *addr)
+{
+	addr->family = skc->skc_family;
+	addr->port = skc->skc_dport;
+	if (addr->family == AF_INET)
+		addr->addr.s_addr = skc->skc_daddr;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (addr->family == AF_INET6)
+		addr->addr6 = skc->skc_v6_daddr;
+#endif
+}
+
+static bool mptcp_pm_is_init_remote_addr(struct mptcp_sock *msk,
+					 const struct mptcp_addr_info *remote)
+{
+	struct mptcp_addr_info mpc_remote;
+
+	mptcp_remote_address((struct sock_common *)msk, &mpc_remote);
+	return mptcp_addresses_equal(&mpc_remote, remote, remote->port);
+}
+
+bool mptcp_pm_has_subflow_saddr(const struct mptcp_sock *msk,
+				const struct mptcp_addr_info *saddr)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_addr_info cur;
+	struct sock_common *skc;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		skc = (struct sock_common *)mptcp_subflow_tcp_sock(subflow);
+
+		mptcp_local_address(skc, &cur);
+		if (mptcp_addresses_equal(&cur, saddr, saddr->port))
+			return true;
+	}
+
+	return false;
+}
+
+static struct mptcp_pm_add_addr *
+mptcp_pm_announced_lookup(const struct mptcp_sock *msk,
+			  const struct mptcp_addr_info *addr)
+{
+	struct mptcp_pm_add_addr *entry;
+
+	lockdep_assert_held(&msk->pm.lock);
+
+	list_for_each_entry(entry, &msk->pm.anno_list, list) {
+		if (mptcp_addresses_equal(&entry->addr, addr, true))
+			return entry;
+	}
+
+	return NULL;
+}
+
+static struct mptcp_pm_add_addr *
+mptcp_pm_announced_del_timer(struct mptcp_sock *msk,
+			     const struct mptcp_addr_info *addr, bool check_id)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_add_addr *entry;
+	bool stop_timer = false;
+
+	rcu_read_lock();
+
+	spin_lock_bh(&msk->pm.lock);
+	entry = mptcp_pm_announced_lookup(msk, addr);
+	if (entry && (!check_id || entry->addr.id == addr->id)) {
+		entry->retrans_times = ADD_ADDR_RETRANS_MAX;
+		stop_timer = true;
+	}
+	if (!check_id && entry)
+		list_del(&entry->list);
+	spin_unlock_bh(&msk->pm.lock);
+
+	/* Note: entry might have been removed by another thread.
+	 * We hold rcu_read_lock() to ensure it is not freed under us.
+	 */
+	if (stop_timer) {
+		if (check_id)
+			sk_stop_timer(sk, &entry->timer);
+		else
+			sk_stop_timer_sync(sk, &entry->timer);
+	}
+
+	rcu_read_unlock();
+	return entry;
+}
+
+bool mptcp_pm_announced_remove(struct mptcp_sock *msk,
+			       const struct mptcp_addr_info *addr)
+{
+	struct mptcp_pm_add_addr *entry;
+	bool ret;
+
+	entry = mptcp_pm_announced_del_timer(msk, addr, false);
+	ret = entry;
+	kfree_rcu(entry, rcu);
+
+	return ret;
+}
+
+bool mptcp_pm_announced_has_ssk(struct mptcp_sock *msk, const struct sock *ssk)
+{
+	struct mptcp_pm_add_addr *entry;
+	struct mptcp_addr_info saddr;
+	bool ret = false;
+
+	mptcp_local_address((struct sock_common *)ssk, &saddr);
+
+	spin_lock_bh(&msk->pm.lock);
+	list_for_each_entry(entry, &msk->pm.anno_list, list) {
+		if (mptcp_addresses_equal(&entry->addr, &saddr, true)) {
+			ret = true;
+			goto out;
+		}
+	}
+
+out:
+	spin_unlock_bh(&msk->pm.lock);
+	return ret;
+}
+
+static void __mptcp_pm_send_ack(struct mptcp_sock *msk,
+				struct mptcp_subflow_context *subflow,
+				bool prio, bool backup)
+{
+	struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+	bool slow;
+
+	pr_debug("send ack for %s\n",
+		 prio ? "mp_prio" :
+		 (mptcp_pm_should_add_signal(msk) ? "add_addr" : "rm_addr"));
+
+	slow = lock_sock_fast(ssk);
+	if (prio) {
+		subflow->send_mp_prio = 1;
+		subflow->request_bkup = backup;
+	}
+
+	__mptcp_subflow_send_ack(ssk);
+	unlock_sock_fast(ssk, slow);
+}
+
+void mptcp_pm_send_ack(struct mptcp_sock *msk,
+		       struct mptcp_subflow_context *subflow,
+		       bool prio, bool backup)
+{
+	spin_unlock_bh(&msk->pm.lock);
+	__mptcp_pm_send_ack(msk, subflow, prio, backup);
+	spin_lock_bh(&msk->pm.lock);
+}
+
+static bool subflow_in_rm_list(const struct mptcp_subflow_context *subflow,
+			       const struct mptcp_rm_list *rm_list)
+{
+	u8 i, id = subflow_get_local_id(subflow);
+
+	for (i = 0; i < rm_list->nr; i++) {
+		if (rm_list->ids[i] == id)
+			return true;
+	}
+
+	return false;
+}
+
+static void mptcp_pm_add_addr_send_ack(struct mptcp_sock *msk);
+static void
+mptcp_pm_addr_send_ack_avoid_list(struct mptcp_sock *msk,
+				  const struct mptcp_rm_list *rm_list)
+{
+	struct mptcp_subflow_context *subflow, *stale = NULL, *same_id = NULL;
+
+	msk_owned_by_me(msk);
+	lockdep_assert_held(&msk->pm.lock);
+
+	if (!mptcp_pm_should_add_signal(msk) &&
+	    !mptcp_pm_should_rm_signal(msk))
+		return;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (!__mptcp_subflow_active(subflow))
+			continue;
+
+		if (unlikely(subflow->stale)) {
+			if (!stale)
+				stale = subflow;
+		} else if (unlikely(rm_list &&
+				    subflow_in_rm_list(subflow, rm_list))) {
+			if (!same_id)
+				same_id = subflow;
+		} else {
+			goto send_ack;
+		}
+	}
+
+	if (same_id)
+		subflow = same_id;
+	else if (stale)
+		subflow = stale;
+	else
+		return;
+
+send_ack:
+	mptcp_pm_send_ack(msk, subflow, false, false);
+}
+
+void mptcp_pm_addr_send_ack(struct mptcp_sock *msk)
+{
+	mptcp_pm_addr_send_ack_avoid_list(msk, NULL);
+}
+
+int mptcp_pm_mp_prio_send_ack(struct mptcp_sock *msk,
+			      struct mptcp_addr_info *addr,
+			      struct mptcp_addr_info *rem,
+			      u8 bkup)
+{
+	struct mptcp_subflow_context *subflow;
+
+	pr_debug("bkup=%d\n", bkup);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		struct mptcp_addr_info local, remote;
+
+		if (!__mptcp_subflow_active(subflow))
+			continue;
+
+		mptcp_local_address((struct sock_common *)ssk, &local);
+		if (!mptcp_addresses_equal(&local, addr, addr->port))
+			continue;
+
+		if (rem && rem->family != AF_UNSPEC) {
+			mptcp_remote_address((struct sock_common *)ssk, &remote);
+			if (!mptcp_addresses_equal(&remote, rem, rem->port))
+				continue;
+		}
+
+		__mptcp_pm_send_ack(msk, subflow, true, bkup);
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static unsigned int mptcp_adjust_add_addr_timeout(struct mptcp_sock *msk)
+{
+	const struct net *net = sock_net((struct sock *)msk);
+	unsigned int rto = mptcp_get_add_addr_timeout(net);
+	struct mptcp_subflow_context *subflow;
+	unsigned int max = 0, max_stale = 0;
+
+	if (!rto)
+		return 0;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		struct inet_connection_sock *icsk = inet_csk(ssk);
+
+		if (!__mptcp_subflow_active(subflow))
+			continue;
+
+		if (unlikely(subflow->stale)) {
+			if (icsk->icsk_rto > max_stale)
+				max_stale = icsk->icsk_rto;
+		} else if (icsk->icsk_rto > max) {
+			max = icsk->icsk_rto;
+		}
+	}
+
+	if (max)
+		return min(max, rto);
+
+	if (max_stale)
+		return min(max_stale, rto);
+
+	return rto;
+}
+
+static void mptcp_pm_add_addr_timer(struct timer_list *timer)
+{
+	struct mptcp_pm_add_addr *entry = timer_container_of(entry, timer,
+							     timer);
+	struct mptcp_sock *msk = entry->sock;
+	struct sock *sk = (struct sock *)msk;
+	unsigned int timeout = 0;
+	bool retransmit;
+
+	pr_debug("msk=%p\n", msk);
+
+	bh_lock_sock(sk);
+	if (unlikely(inet_sk_state_load(sk) == TCP_CLOSE))
+		goto out;
+
+	if (sock_owned_by_user(sk)) {
+		/* Try again later. */
+		timeout = HZ / 20;
+		goto out;
+	}
+
+	timeout = mptcp_adjust_add_addr_timeout(msk);
+	if (!timeout || mptcp_pm_should_add_signal_addr(msk))
+		goto out;
+
+	spin_lock_bh(&msk->pm.lock);
+
+	/* The cancel path (mptcp_pm_announced_del_timer()) can race with this
+	 * callback. Once cancel updates retrans_times to MAX, suppress further
+	 * retransmissions here. If this callback acquires pm.lock first, one
+	 * final transmit attempt is still possible.
+	 */
+	if (entry->retrans_times < ADD_ADDR_RETRANS_MAX &&
+	    !mptcp_pm_should_add_signal_addr(msk)) {
+		pr_debug("retransmit ADD_ADDR id=%d\n", entry->addr.id);
+		mptcp_pm_announce_addr(msk, &entry->addr, false);
+		mptcp_pm_add_addr_send_ack(msk);
+		entry->retrans_times++;
+	}
+
+	retransmit = entry->retrans_times < ADD_ADDR_RETRANS_MAX;
+	if (retransmit)
+		timeout <<= entry->retrans_times;
+	else
+		timeout = 0;
+
+	spin_unlock_bh(&msk->pm.lock);
+
+	if (!retransmit)
+		mptcp_pm_subflow_established(msk);
+
+out:
+	if (timeout)
+		sk_reset_timer(sk, timer, jiffies + timeout);
+	else
+		/* if sock_put calls sk_free: avoid waiting for this timer */
+		entry->timer_done = true;
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+bool mptcp_pm_announced_alloc(struct mptcp_sock *msk,
+			      const struct mptcp_addr_info *addr)
+{
+	struct mptcp_pm_add_addr *add_entry = NULL;
+	struct sock *sk = (struct sock *)msk;
+	unsigned int timeout;
+
+	lockdep_assert_held(&msk->pm.lock);
+
+	if (msk->pm.status & BIT(MPTCP_PM_DESTROYING))
+		return false;
+
+	add_entry = mptcp_pm_announced_lookup(msk, addr);
+	if (add_entry) {
+		if (WARN_ON_ONCE(mptcp_pm_is_kernel(msk)))
+			return false;
+
+		goto reset_timer;
+	}
+
+	add_entry = kmalloc_obj(*add_entry, GFP_ATOMIC);
+	if (!add_entry)
+		return false;
+
+	list_add(&add_entry->list, &msk->pm.anno_list);
+
+	add_entry->addr = *addr;
+	add_entry->sock = msk;
+
+	timer_setup(&add_entry->timer, mptcp_pm_add_addr_timer, 0);
+reset_timer:
+	add_entry->retrans_times = 0;
+	add_entry->timer_done = false;
+	timeout = mptcp_adjust_add_addr_timeout(msk);
+	if (timeout)
+		sk_reset_timer(sk, &add_entry->timer, jiffies + timeout);
+
+	return true;
+}
+
+static void mptcp_pm_free_announced_list(struct mptcp_sock *msk)
+{
+	struct mptcp_pm_add_addr *entry, *tmp;
+	struct sock *sk = (struct sock *)msk;
+	LIST_HEAD(free_list);
+
+	pr_debug("msk=%p\n", msk);
+
+	spin_lock_bh(&msk->pm.lock);
+	list_splice_init(&msk->pm.anno_list, &free_list);
+	spin_unlock_bh(&msk->pm.lock);
+
+	list_for_each_entry_safe(entry, tmp, &free_list, list) {
+		if (!entry->timer_done)
+			sk_stop_timer_sync(sk, &entry->timer);
+		kfree_rcu(entry, rcu);
+	}
+}
+
+/* path manager command handlers */
+
+int mptcp_pm_announce_addr(struct mptcp_sock *msk,
+			   const struct mptcp_addr_info *addr,
+			   bool echo)
+{
+	u8 add_addr = READ_ONCE(msk->pm.addr_signal);
+
+	pr_debug("msk=%p, local_id=%d, echo=%d\n", msk, addr->id, echo);
+
+	lockdep_assert_held(&msk->pm.lock);
+
+	if (add_addr &
+	    (echo ? BIT(MPTCP_ADD_ADDR_ECHO) : BIT(MPTCP_ADD_ADDR_SIGNAL))) {
+		MPTCP_INC_STATS(sock_net((struct sock *)msk),
+				echo ? MPTCP_MIB_ECHOADDTXDROP : MPTCP_MIB_ADDADDRTXDROP);
+		return -EINVAL;
+	}
+
+	if (echo) {
+		msk->pm.remote = *addr;
+		add_addr |= BIT(MPTCP_ADD_ADDR_ECHO);
+	} else {
+		msk->pm.local = *addr;
+		add_addr |= BIT(MPTCP_ADD_ADDR_SIGNAL);
+	}
+	WRITE_ONCE(msk->pm.addr_signal, add_addr);
+	return 0;
+}
+
+int mptcp_pm_remove_addr(struct mptcp_sock *msk, const struct mptcp_rm_list *rm_list)
+{
+	u8 rm_addr = READ_ONCE(msk->pm.addr_signal);
+
+	pr_debug("msk=%p, rm_list_nr=%d\n", msk, rm_list->nr);
+
+	if (rm_addr) {
+		MPTCP_ADD_STATS(sock_net((struct sock *)msk),
+				MPTCP_MIB_RMADDRTXDROP, rm_list->nr);
+		return -EINVAL;
+	}
+
+	msk->pm.rm_list_tx = *rm_list;
+	rm_addr |= BIT(MPTCP_RM_ADDR_SIGNAL);
+	WRITE_ONCE(msk->pm.addr_signal, rm_addr);
+	mptcp_pm_addr_send_ack_avoid_list(msk, rm_list);
+	return 0;
+}
+
+/* path manager event handlers */
+
+void mptcp_pm_new_connection(struct mptcp_sock *msk, const struct sock *ssk, int server_side)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+
+	pr_debug("msk=%p, token=%u side=%d\n", msk, READ_ONCE(msk->token), server_side);
+
+	WRITE_ONCE(pm->server_side, server_side);
+	mptcp_event(MPTCP_EVENT_CREATED, msk, ssk, GFP_ATOMIC);
+}
+
+bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+	unsigned int limit_extra_subflows;
+	int ret = 0;
+
+	if (mptcp_pm_is_userspace(msk)) {
+		if (mptcp_userspace_pm_active(msk)) {
+			spin_lock_bh(&pm->lock);
+			pm->extra_subflows++;
+			spin_unlock_bh(&pm->lock);
+			return true;
+		}
+		return false;
+	}
+
+	limit_extra_subflows = mptcp_pm_get_limit_extra_subflows(msk);
+
+	pr_debug("msk=%p subflows=%d max=%d allow=%d\n", msk,
+		 pm->extra_subflows, limit_extra_subflows,
+		 READ_ONCE(pm->accept_subflow));
+
+	/* try to avoid acquiring the lock below */
+	if (!READ_ONCE(pm->accept_subflow))
+		return false;
+
+	spin_lock_bh(&pm->lock);
+	if (READ_ONCE(pm->accept_subflow)) {
+		ret = pm->extra_subflows < limit_extra_subflows;
+		if (ret && ++pm->extra_subflows == limit_extra_subflows)
+			WRITE_ONCE(pm->accept_subflow, false);
+	}
+	spin_unlock_bh(&pm->lock);
+
+	return ret;
+}
+
+/* return true if the new status bit is currently cleared, that is, this event
+ * can be server, eventually by an already scheduled work
+ */
+static bool mptcp_pm_schedule_work(struct mptcp_sock *msk,
+				   enum mptcp_pm_status new_status)
+{
+	pr_debug("msk=%p status=%x new=%lx\n", msk, msk->pm.status,
+		 BIT(new_status));
+	if (msk->pm.status & BIT(new_status))
+		return false;
+
+	msk->pm.status |= BIT(new_status);
+	mptcp_schedule_work((struct sock *)msk);
+	return true;
+}
+
+void mptcp_pm_fully_established(struct mptcp_sock *msk, const struct sock *ssk)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+	bool announce = false;
+
+	pr_debug("msk=%p\n", msk);
+
+	spin_lock_bh(&pm->lock);
+
+	/* mptcp_pm_fully_established() can be invoked by multiple
+	 * racing paths - accept() and check_fully_established()
+	 * be sure to serve this event only once.
+	 */
+	if (READ_ONCE(pm->work_pending) &&
+	    !(pm->status & BIT(MPTCP_PM_ALREADY_ESTABLISHED)))
+		mptcp_pm_schedule_work(msk, MPTCP_PM_ESTABLISHED);
+
+	if ((pm->status & BIT(MPTCP_PM_ALREADY_ESTABLISHED)) == 0)
+		announce = true;
+
+	pm->status |= BIT(MPTCP_PM_ALREADY_ESTABLISHED);
+	spin_unlock_bh(&pm->lock);
+
+	if (announce)
+		mptcp_event(MPTCP_EVENT_ESTABLISHED, msk, ssk, GFP_ATOMIC);
+}
+
+void mptcp_pm_connection_closed(struct mptcp_sock *msk)
+{
+	pr_debug("msk=%p\n", msk);
+
+	if (msk->token)
+		mptcp_event(MPTCP_EVENT_CLOSED, msk, NULL, GFP_KERNEL);
+}
+
+void mptcp_pm_subflow_established(struct mptcp_sock *msk)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+
+	pr_debug("msk=%p\n", msk);
+
+	if (!READ_ONCE(pm->work_pending))
+		return;
+
+	spin_lock_bh(&pm->lock);
+
+	if (READ_ONCE(pm->work_pending))
+		mptcp_pm_schedule_work(msk, MPTCP_PM_SUBFLOW_ESTABLISHED);
+
+	spin_unlock_bh(&pm->lock);
+}
+
+void mptcp_pm_subflow_check_next(struct mptcp_sock *msk,
+				 const struct mptcp_subflow_context *subflow)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_data *pm = &msk->pm;
+	bool update_subflows;
+
+	update_subflows = subflow->request_join || subflow->mp_join;
+	if (mptcp_pm_is_userspace(msk)) {
+		if (update_subflows) {
+			spin_lock_bh(&pm->lock);
+			if (!WARN_ON_ONCE(pm->extra_subflows == 0))
+				pm->extra_subflows--;
+			spin_unlock_bh(&pm->lock);
+		}
+		return;
+	}
+
+	if (!READ_ONCE(pm->work_pending) && !update_subflows)
+		return;
+
+	spin_lock_bh(&pm->lock);
+	if (update_subflows)
+		__mptcp_pm_close_subflow(msk);
+
+	/* Even if this subflow is not really established, tell the PM to try
+	 * to pick the next ones, if possible.
+	 */
+	if (mptcp_is_fully_established(sk) &&
+	    mptcp_pm_nl_check_work_pending(msk))
+		mptcp_pm_schedule_work(msk, MPTCP_PM_SUBFLOW_ESTABLISHED);
+
+	spin_unlock_bh(&pm->lock);
+}
+
+void mptcp_pm_add_addr_received(const struct sock *ssk,
+				const struct mptcp_addr_info *addr)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct mptcp_pm_data *pm = &msk->pm;
+
+	pr_debug("msk=%p remote_id=%d accept=%d\n", msk, addr->id,
+		 READ_ONCE(pm->accept_addr));
+
+	mptcp_event_addr_announced(ssk, addr);
+
+	spin_lock_bh(&pm->lock);
+
+	if (mptcp_pm_is_userspace(msk)) {
+		if (mptcp_userspace_pm_active(msk)) {
+			mptcp_pm_announce_addr(msk, addr, true);
+			mptcp_pm_add_addr_send_ack(msk);
+		} else {
+			__MPTCP_INC_STATS(sock_net((struct sock *)msk), MPTCP_MIB_ADDADDRDROP);
+		}
+	/* - id0 should not have a different address
+	 * - special case for C-flag: linked to fill_local_addresses_vec()
+	 */
+	} else if ((addr->id == 0 && !mptcp_pm_is_init_remote_addr(msk, addr)) ||
+		   (addr->id > 0 && !READ_ONCE(pm->accept_addr) &&
+		    !mptcp_pm_add_addr_c_flag_case(msk))) {
+		mptcp_pm_announce_addr(msk, addr, true);
+		mptcp_pm_add_addr_send_ack(msk);
+	} else if (mptcp_pm_schedule_work(msk, MPTCP_PM_ADD_ADDR_RECEIVED)) {
+		pm->remote = *addr;
+	} else {
+		__MPTCP_INC_STATS(sock_net((struct sock *)msk), MPTCP_MIB_ADDADDRDROP);
+	}
+
+	spin_unlock_bh(&pm->lock);
+}
+
+void mptcp_pm_add_addr_echoed(struct mptcp_sock *msk,
+			      const struct mptcp_addr_info *addr)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+	struct mptcp_pm_add_addr *entry;
+
+	pr_debug("msk=%p\n", msk);
+
+	entry = mptcp_pm_announced_del_timer(msk, addr, true);
+
+	if (!entry || !READ_ONCE(pm->work_pending))
+		return;
+
+	spin_lock_bh(&pm->lock);
+
+	if (READ_ONCE(pm->work_pending))
+		mptcp_pm_schedule_work(msk, MPTCP_PM_SUBFLOW_ESTABLISHED);
+
+	spin_unlock_bh(&pm->lock);
+}
+
+/* To be called while pm->lock is held */
+static void mptcp_pm_add_addr_send_ack(struct mptcp_sock *msk)
+{
+	if (!mptcp_pm_should_add_signal(msk))
+		return;
+
+	mptcp_pm_schedule_work(msk, MPTCP_PM_ADD_ADDR_SEND_ACK);
+}
+
+static void mptcp_pm_rm_addr_or_subflow(struct mptcp_sock *msk,
+					const struct mptcp_rm_list *rm_list,
+					enum linux_mptcp_mib_field rm_type)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct sock *sk = (struct sock *)msk;
+	u8 i;
+
+	pr_debug("%s rm_list_nr %d\n",
+		 rm_type == MPTCP_MIB_RMADDR ? "address" : "subflow", rm_list->nr);
+
+	msk_owned_by_me(msk);
+
+	if (sk->sk_state == TCP_LISTEN)
+		return;
+
+	if (!rm_list->nr)
+		return;
+
+	if (list_empty(&msk->conn_list))
+		return;
+
+	for (i = 0; i < rm_list->nr; i++) {
+		u8 rm_id = rm_list->ids[i];
+		bool removed = false;
+
+		mptcp_for_each_subflow_safe(msk, subflow, tmp) {
+			struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+			u8 remote_id = READ_ONCE(subflow->remote_id);
+			int how = RCV_SHUTDOWN | SEND_SHUTDOWN;
+			u8 id = subflow_get_local_id(subflow);
+
+			if ((1 << inet_sk_state_load(ssk)) &
+			    (TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | TCPF_CLOSING | TCPF_CLOSE))
+				continue;
+			if (rm_type == MPTCP_MIB_RMADDR && remote_id != rm_id)
+				continue;
+			if (rm_type == MPTCP_MIB_RMSUBFLOW && id != rm_id)
+				continue;
+
+			pr_debug(" -> %s rm_list_ids[%d]=%u local_id=%u remote_id=%u mpc_id=%u\n",
+				 rm_type == MPTCP_MIB_RMADDR ? "address" : "subflow",
+				 i, rm_id, id, remote_id, msk->mpc_endpoint_id);
+			spin_unlock_bh(&msk->pm.lock);
+			mptcp_subflow_shutdown(sk, ssk, how);
+			removed |= subflow->request_join;
+
+			/* the following takes care of updating the subflows counter */
+			mptcp_close_ssk(sk, ssk, subflow);
+			spin_lock_bh(&msk->pm.lock);
+
+			if (rm_type == MPTCP_MIB_RMSUBFLOW)
+				__MPTCP_INC_STATS(sock_net(sk), rm_type);
+		}
+
+		if (rm_type == MPTCP_MIB_RMADDR) {
+			__MPTCP_INC_STATS(sock_net(sk), rm_type);
+			if (removed && mptcp_pm_is_kernel(msk))
+				mptcp_pm_nl_rm_addr(msk, rm_id);
+		}
+	}
+}
+
+static void mptcp_pm_rm_addr_recv(struct mptcp_sock *msk)
+{
+	mptcp_pm_rm_addr_or_subflow(msk, &msk->pm.rm_list_rx, MPTCP_MIB_RMADDR);
+}
+
+void mptcp_pm_rm_subflow(struct mptcp_sock *msk,
+			 const struct mptcp_rm_list *rm_list)
+{
+	mptcp_pm_rm_addr_or_subflow(msk, rm_list, MPTCP_MIB_RMSUBFLOW);
+}
+
+void mptcp_pm_rm_addr_received(struct mptcp_sock *msk,
+			       const struct mptcp_rm_list *rm_list)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+	u8 i;
+
+	pr_debug("msk=%p remote_ids_nr=%d\n", msk, rm_list->nr);
+
+	for (i = 0; i < rm_list->nr; i++)
+		mptcp_event_addr_removed(msk, rm_list->ids[i]);
+
+	spin_lock_bh(&pm->lock);
+	if (mptcp_pm_schedule_work(msk, MPTCP_PM_RM_ADDR_RECEIVED))
+		pm->rm_list_rx = *rm_list;
+	else
+		__MPTCP_INC_STATS(sock_net((struct sock *)msk), MPTCP_MIB_RMADDRDROP);
+	spin_unlock_bh(&pm->lock);
+}
+
+void mptcp_pm_mp_prio_received(struct sock *ssk, u8 bkup)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = subflow->conn;
+	struct mptcp_sock *msk;
+
+	pr_debug("subflow->backup=%d, bkup=%d\n", subflow->backup, bkup);
+	msk = mptcp_sk(sk);
+	if (subflow->backup != bkup)
+		subflow->backup = bkup;
+
+	mptcp_event(MPTCP_EVENT_SUB_PRIORITY, msk, ssk, GFP_ATOMIC);
+}
+
+void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+
+	pr_debug("fail_seq=%llu\n", fail_seq);
+
+	/* After accepting the fail, we can't create any other subflows */
+	spin_lock_bh(&msk->fallback_lock);
+	if (!msk->allow_infinite_fallback) {
+		spin_unlock_bh(&msk->fallback_lock);
+		return;
+	}
+	msk->allow_subflows = false;
+	spin_unlock_bh(&msk->fallback_lock);
+
+	if (!subflow->fail_tout) {
+		pr_debug("send MP_FAIL response and infinite map\n");
+
+		subflow->send_mp_fail = 1;
+		subflow->send_infinite_map = 1;
+		tcp_send_ack(sk);
+	} else {
+		pr_debug("MP_FAIL response received\n");
+		WRITE_ONCE(subflow->fail_tout, 0);
+	}
+}
+
+static int mptcp_add_addr_len(int family, bool echo, bool port)
+{
+	int len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
+
+	if (family == AF_INET6)
+		len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
+	if (!echo)
+		len += MPTCPOPT_THMAC_LEN;
+	/* account for 2 trailing 'nop' options */
+	if (port)
+		len += TCPOLEN_MPTCP_PORT_LEN + TCPOLEN_MPTCP_PORT_ALIGN;
+
+	return len;
+}
+
+bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, int *size, int remaining,
+			      struct mptcp_addr_info *addr, bool *echo,
+			      bool *drop_ts)
+{
+	bool skip_add_addr = false;
+	bool ret = false;
+	u8 add_addr;
+	int len = 0;
+	u8 family;
+	bool port;
+
+	spin_lock_bh(&msk->pm.lock);
+
+	/* double check after the lock is acquired */
+	if (!mptcp_pm_should_add_signal(msk))
+		goto out_unlock;
+
+	/* always drop every other options for pure ack ADD_ADDR; this is a
+	 * plain dup-ack from TCP perspective. The other MPTCP-relevant info,
+	 * if any, will be carried by the 'original' TCP ack
+	 */
+	len -= *size;
+
+	*echo = mptcp_pm_should_add_signal_echo(msk);
+	if (*echo) {
+		*addr = msk->pm.remote;
+		add_addr = msk->pm.addr_signal & ~BIT(MPTCP_ADD_ADDR_ECHO);
+		port = !!msk->pm.remote.port;
+		family = msk->pm.remote.family;
+	} else {
+		*addr = msk->pm.local;
+		add_addr = msk->pm.addr_signal & ~BIT(MPTCP_ADD_ADDR_SIGNAL);
+		port = !!msk->pm.local.port;
+		family = msk->pm.local.family;
+	}
+
+	len += mptcp_add_addr_len(family, *echo, port);
+	if (len > remaining) {
+		struct net *net = sock_net((struct sock *)msk);
+
+		if (*drop_ts && mptcp_add_addr_v6_port_drop_ts(net)) {
+			/* OK without TCP Timestamps? */
+			len -= TCPOLEN_TSTAMP_ALIGNED;
+			if (len <= remaining)
+				goto enough_space;
+		}
+
+		if (*echo) {
+			MPTCP_INC_STATS(net, MPTCP_MIB_ECHOADDTXDROP);
+		} else {
+			skip_add_addr = true;
+			MPTCP_INC_STATS(net, MPTCP_MIB_ADDADDRTXDROP);
+		}
+		goto drop_signal_mark;
+	}
+
+	*drop_ts = false;
+
+enough_space:
+	ret = true;
+	*size = len;
+
+drop_signal_mark:
+	WRITE_ONCE(msk->pm.addr_signal, add_addr);
+
+out_unlock:
+	spin_unlock_bh(&msk->pm.lock);
+
+	/* On pure-ACK option-space exhaustion, stop retrying this ADD_ADDR:
+	 * clear the signal bit, cancel the matching retransmission timer, and
+	 * let the PM state machine progress.
+	 */
+	if (skip_add_addr) {
+		mptcp_pm_announced_del_timer(msk, addr, true);
+		mptcp_pm_subflow_established(msk);
+	}
+	return ret;
+}
+
+static int mptcp_rm_addr_len(const struct mptcp_rm_list *rm_list)
+{
+	if (rm_list->nr == 0 || rm_list->nr > MPTCP_RM_IDS_MAX)
+		return -EINVAL;
+
+	return TCPOLEN_MPTCP_RM_ADDR_BASE + roundup(rm_list->nr - 1, 4) + 1;
+}
+
+bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
+			     struct mptcp_rm_list *rm_list, int *size)
+{
+	int ret = false, len;
+	u8 rm_addr;
+
+	spin_lock_bh(&msk->pm.lock);
+
+	/* double check after the lock is acquired */
+	if (!mptcp_pm_should_rm_signal(msk))
+		goto out_unlock;
+
+	rm_addr = msk->pm.addr_signal & ~BIT(MPTCP_RM_ADDR_SIGNAL);
+	len = mptcp_rm_addr_len(&msk->pm.rm_list_tx);
+	if (len < 0) {
+		WRITE_ONCE(msk->pm.addr_signal, rm_addr);
+		goto out_unlock;
+	}
+	if (remaining < len)
+		goto out_unlock;
+
+	*size = len;
+	*rm_list = msk->pm.rm_list_tx;
+	WRITE_ONCE(msk->pm.addr_signal, rm_addr);
+	ret = true;
+
+out_unlock:
+	spin_unlock_bh(&msk->pm.lock);
+	return ret;
+}
+
+int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc)
+{
+	struct mptcp_pm_addr_entry skc_local = { 0 };
+	struct mptcp_addr_info msk_local;
+
+	if (WARN_ON_ONCE(!msk))
+		return -1;
+
+	/* The 0 ID mapping is defined by the first subflow, copied into the msk
+	 * addr
+	 */
+	mptcp_local_address((struct sock_common *)msk, &msk_local);
+	mptcp_local_address((struct sock_common *)skc, &skc_local.addr);
+	if (mptcp_addresses_equal(&msk_local, &skc_local.addr, false))
+		return 0;
+
+	skc_local.addr.id = 0;
+	skc_local.flags = MPTCP_PM_ADDR_FLAG_IMPLICIT;
+
+	if (mptcp_pm_is_userspace(msk))
+		return mptcp_userspace_pm_get_local_id(msk, &skc_local);
+	return mptcp_pm_nl_get_local_id(msk, &skc_local);
+}
+
+bool mptcp_pm_is_backup(struct mptcp_sock *msk, struct sock_common *skc)
+{
+	struct mptcp_addr_info skc_local;
+
+	mptcp_local_address((struct sock_common *)skc, &skc_local);
+
+	if (mptcp_pm_is_userspace(msk))
+		return mptcp_userspace_pm_is_backup(msk, &skc_local);
+
+	return mptcp_pm_nl_is_backup(msk, &skc_local);
+}
+
+static void
+mptcp_pm_subflow_chk_stale(const struct mptcp_sock *msk, struct sock *ssk)
+{
+	struct mptcp_subflow_context *iter, *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = (struct sock *)msk;
+	unsigned int active_max_loss_cnt;
+	struct net *net = sock_net(sk);
+	unsigned int stale_loss_cnt;
+	bool slow;
+
+	stale_loss_cnt = mptcp_stale_loss_cnt(net);
+	if (subflow->stale || !stale_loss_cnt || subflow->stale_count <= stale_loss_cnt)
+		return;
+
+	/* look for another available subflow not in loss state */
+	active_max_loss_cnt = max_t(int, stale_loss_cnt - 1, 1);
+	mptcp_for_each_subflow(msk, iter) {
+		if (iter != subflow && mptcp_subflow_active(iter) &&
+		    iter->stale_count < active_max_loss_cnt) {
+			/* we have some alternatives, try to mark this subflow as idle ...*/
+			slow = lock_sock_fast(ssk);
+			if (!tcp_rtx_and_write_queues_empty(ssk)) {
+				subflow->stale = 1;
+				__mptcp_retransmit_pending_data(sk);
+				MPTCP_INC_STATS(net, MPTCP_MIB_SUBFLOWSTALE);
+			}
+			unlock_sock_fast(ssk, slow);
+
+			/* always try to push the pending data regardless of re-injections:
+			 * we can possibly use backup subflows now, and subflow selection
+			 * is cheap under the msk socket lock
+			 */
+			__mptcp_push_pending(sk, 0);
+			return;
+		}
+	}
+}
+
+void mptcp_pm_chk_stale(const struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		u32 rcv_tstamp;
+
+		if (!__mptcp_subflow_active(subflow))
+			continue;
+
+		/* No data outstanding at TCP level? not stale */
+		if (tcp_rtx_and_write_queues_empty(ssk))
+			continue;
+
+		/* keep track of rtx periods with no progress */
+		rcv_tstamp = READ_ONCE(tcp_sk(ssk)->rcv_tstamp);
+		if (!subflow->stale_count) {
+			subflow->stale_rcv_tstamp = rcv_tstamp;
+			subflow->stale_count++;
+		} else if (subflow->stale_rcv_tstamp == rcv_tstamp) {
+			if (subflow->stale_count < U8_MAX)
+				subflow->stale_count++;
+			mptcp_pm_subflow_chk_stale(msk, ssk);
+		} else {
+			subflow->stale_count = 0;
+			mptcp_subflow_set_active(subflow);
+		}
+	}
+}
+
+void mptcp_pm_worker(struct mptcp_sock *msk)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+
+	msk_owned_by_me(msk);
+
+	if (!(pm->status & MPTCP_PM_WORK_MASK))
+		return;
+
+	spin_lock_bh(&msk->pm.lock);
+
+	pr_debug("msk=%p status=%x\n", msk, pm->status);
+	if (pm->status & BIT(MPTCP_PM_ADD_ADDR_SEND_ACK)) {
+		pm->status &= ~BIT(MPTCP_PM_ADD_ADDR_SEND_ACK);
+		mptcp_pm_addr_send_ack(msk);
+	}
+	if (pm->status & BIT(MPTCP_PM_RM_ADDR_RECEIVED)) {
+		pm->status &= ~BIT(MPTCP_PM_RM_ADDR_RECEIVED);
+		mptcp_pm_rm_addr_recv(msk);
+	}
+	__mptcp_pm_kernel_worker(msk);
+
+	spin_unlock_bh(&msk->pm.lock);
+}
+
+void mptcp_pm_destroy(struct mptcp_sock *msk)
+{
+	spin_lock_bh(&msk->pm.lock);
+	msk->pm.status |= BIT(MPTCP_PM_DESTROYING);
+	spin_unlock_bh(&msk->pm.lock);
+
+	mptcp_pm_free_announced_list(msk);
+
+	/* Free the userspace local address list unconditionally: the socket
+	 * can be reused (mptcp_disconnect()) and re-selected to a different PM
+	 */
+	mptcp_userspace_pm_free_local_addr_list(msk);
+}
+
+void mptcp_pm_data_reset(struct mptcp_sock *msk)
+{
+	u8 pm_type = mptcp_get_pm_type(sock_net((struct sock *)msk));
+	struct mptcp_pm_data *pm = &msk->pm;
+
+	memset(&pm->reset, 0, sizeof(pm->reset));
+	pm->rm_list_tx.nr = 0;
+	pm->rm_list_rx.nr = 0;
+	WRITE_ONCE(pm->pm_type, pm_type);
+
+	if (pm_type == MPTCP_PM_TYPE_KERNEL) {
+		bool subflows_allowed = !!mptcp_pm_get_limit_extra_subflows(msk);
+
+		/* pm->work_pending must be only be set to 'true' when
+		 * pm->pm_type is set to MPTCP_PM_TYPE_KERNEL
+		 */
+		WRITE_ONCE(pm->work_pending,
+			   (!!mptcp_pm_get_endp_subflow_max(msk) &&
+			    subflows_allowed) ||
+			   !!mptcp_pm_get_endp_signal_max(msk));
+		WRITE_ONCE(pm->accept_addr,
+			   !!mptcp_pm_get_limit_add_addr_accepted(msk) &&
+			   subflows_allowed);
+		WRITE_ONCE(pm->accept_subflow, subflows_allowed);
+
+		bitmap_fill(pm->id_avail_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
+	}
+}
+
+void mptcp_pm_data_init(struct mptcp_sock *msk)
+{
+	spin_lock_init(&msk->pm.lock);
+	INIT_LIST_HEAD(&msk->pm.anno_list);
+	INIT_LIST_HEAD(&msk->pm.userspace_pm_local_addr_list);
+	mptcp_pm_data_reset(msk);
+}
+
+void __init mptcp_pm_init(void)
+{
+	mptcp_pm_kernel_register();
+	mptcp_pm_userspace_register();
+	mptcp_pm_nl_init();
+}
+
+/* Must be called with rcu read lock held */
+struct mptcp_pm_ops *mptcp_pm_find(const char *name)
+{
+	struct mptcp_pm_ops *pm_ops;
+
+	list_for_each_entry_rcu(pm_ops, &mptcp_pm_list, list) {
+		if (!strcmp(pm_ops->name, name))
+			return pm_ops;
+	}
+
+	return NULL;
+}
+
+int mptcp_pm_validate(struct mptcp_pm_ops *pm_ops)
+{
+	return 0;
+}
+
+int mptcp_pm_register(struct mptcp_pm_ops *pm_ops)
+{
+	int ret;
+
+	ret = mptcp_pm_validate(pm_ops);
+	if (ret)
+		return ret;
+
+	spin_lock(&mptcp_pm_list_lock);
+	if (mptcp_pm_find(pm_ops->name)) {
+		spin_unlock(&mptcp_pm_list_lock);
+		return -EEXIST;
+	}
+	list_add_tail_rcu(&pm_ops->list, &mptcp_pm_list);
+	spin_unlock(&mptcp_pm_list_lock);
+
+	pr_debug("%s registered\n", pm_ops->name);
+	return 0;
+}
+
+void mptcp_pm_unregister(struct mptcp_pm_ops *pm_ops)
+{
+	/* skip unregistering the default path manager */
+	if (WARN_ON_ONCE(pm_ops == &mptcp_pm_kernel))
+		return;
+
+	spin_lock(&mptcp_pm_list_lock);
+	list_del_rcu(&pm_ops->list);
+	spin_unlock(&mptcp_pm_list_lock);
+}
+
+/* Build string with list of available path manager values.
+ * Similar to tcp_get_available_congestion_control()
+ */
+void mptcp_pm_get_available(char *buf, size_t maxlen)
+{
+	struct mptcp_pm_ops *pm_ops;
+	size_t offs = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(pm_ops, &mptcp_pm_list, list) {
+		offs += snprintf(buf + offs, maxlen - offs, "%s%s",
+				 offs == 0 ? "" : " ", pm_ops->name);
+
+		if (WARN_ON_ONCE(offs >= maxlen))
+			break;
+	}
+	rcu_read_unlock();
+}
diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
new file mode 100644
index 000000000..1a7750813
--- /dev/null
+++ b/net/mptcp/pm_kernel.c
@@ -0,0 +1,1663 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2025, Matthieu Baerts.
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <net/netns/generic.h>
+
+#include "protocol.h"
+#include "mib.h"
+#include "mptcp_pm_gen.h"
+
+static int pm_nl_pernet_id;
+
+struct pm_nl_pernet {
+	/* protects pernet updates */
+	spinlock_t		lock;
+	struct list_head	endp_list;
+	u8			endpoints;
+	u8			endp_signal_max;
+	u8			endp_subflow_max;
+	u8			endp_laminar_max;
+	u8			endp_fullmesh_max;
+	u8			limit_add_addr_accepted;
+	u8			limit_extra_subflows;
+	u8			next_id;
+	DECLARE_BITMAP(id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
+};
+
+#define MPTCP_PM_ADDR_MAX	8
+#define MPTCP_PM_SUBFLOWS_MAX	64
+
+static struct pm_nl_pernet *pm_nl_get_pernet(const struct net *net)
+{
+	return net_generic(net, pm_nl_pernet_id);
+}
+
+static struct pm_nl_pernet *
+pm_nl_get_pernet_from_msk(const struct mptcp_sock *msk)
+{
+	return pm_nl_get_pernet(sock_net((struct sock *)msk));
+}
+
+static struct pm_nl_pernet *genl_info_pm_nl(struct genl_info *info)
+{
+	return pm_nl_get_pernet(genl_info_net(info));
+}
+
+u8 mptcp_pm_get_endp_signal_max(const struct mptcp_sock *msk)
+{
+	const struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+
+	return READ_ONCE(pernet->endp_signal_max);
+}
+EXPORT_SYMBOL_GPL(mptcp_pm_get_endp_signal_max);
+
+u8 mptcp_pm_get_endp_subflow_max(const struct mptcp_sock *msk)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+
+	return READ_ONCE(pernet->endp_subflow_max);
+}
+EXPORT_SYMBOL_GPL(mptcp_pm_get_endp_subflow_max);
+
+u8 mptcp_pm_get_endp_laminar_max(const struct mptcp_sock *msk)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+
+	return READ_ONCE(pernet->endp_laminar_max);
+}
+EXPORT_SYMBOL_GPL(mptcp_pm_get_endp_laminar_max);
+
+u8 mptcp_pm_get_endp_fullmesh_max(const struct mptcp_sock *msk)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+
+	return READ_ONCE(pernet->endp_fullmesh_max);
+}
+EXPORT_SYMBOL_GPL(mptcp_pm_get_endp_fullmesh_max);
+
+u8 mptcp_pm_get_limit_add_addr_accepted(const struct mptcp_sock *msk)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+
+	return READ_ONCE(pernet->limit_add_addr_accepted);
+}
+EXPORT_SYMBOL_GPL(mptcp_pm_get_limit_add_addr_accepted);
+
+u8 mptcp_pm_get_limit_extra_subflows(const struct mptcp_sock *msk)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+
+	return READ_ONCE(pernet->limit_extra_subflows);
+}
+EXPORT_SYMBOL_GPL(mptcp_pm_get_limit_extra_subflows);
+
+static bool has_subflow_daddr(const struct mptcp_sock *msk,
+			      const struct mptcp_addr_info *daddr)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_addr_info cur;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (!((1 << inet_sk_state_load(ssk)) &
+		      (TCPF_ESTABLISHED | TCPF_SYN_SENT | TCPF_SYN_RECV)))
+			continue;
+
+		mptcp_remote_address((struct sock_common *)ssk, &cur);
+		if (mptcp_addresses_equal(&cur, daddr, daddr->port))
+			return true;
+	}
+
+	return false;
+}
+
+static bool
+select_local_address(const struct pm_nl_pernet *pernet,
+		     const struct mptcp_sock *msk,
+		     struct mptcp_pm_local *new_local)
+{
+	struct mptcp_pm_addr_entry *entry;
+	bool found = false;
+
+	msk_owned_by_me(msk);
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(entry, &pernet->endp_list, list) {
+		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW))
+			continue;
+
+		if (!test_bit(entry->addr.id, msk->pm.id_avail_bitmap))
+			continue;
+
+		new_local->addr = entry->addr;
+		new_local->flags = entry->flags;
+		new_local->ifindex = entry->ifindex;
+		found = true;
+		break;
+	}
+	rcu_read_unlock();
+
+	return found;
+}
+
+static bool
+select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk,
+		      struct mptcp_pm_local *new_local)
+{
+	struct mptcp_pm_addr_entry *entry;
+	bool found = false;
+
+	rcu_read_lock();
+	/* do not keep any additional per socket state, just signal
+	 * the address list in order.
+	 * Note: removal from the local address list during the msk life-cycle
+	 * can lead to additional addresses not being announced.
+	 */
+	list_for_each_entry_rcu(entry, &pernet->endp_list, list) {
+		if (!test_bit(entry->addr.id, msk->pm.id_avail_bitmap))
+			continue;
+
+		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL))
+			continue;
+
+		new_local->addr = entry->addr;
+		new_local->flags = entry->flags;
+		new_local->ifindex = entry->ifindex;
+		found = true;
+		break;
+	}
+	rcu_read_unlock();
+
+	return found;
+}
+
+static unsigned int
+fill_remote_addr(struct mptcp_sock *msk, struct mptcp_addr_info *local,
+		 struct mptcp_addr_info *addrs)
+{
+	bool deny_id0 = READ_ONCE(msk->pm.remote_deny_join_id0);
+	struct mptcp_addr_info remote = { 0 };
+	struct sock *sk = (struct sock *)msk;
+
+	if (deny_id0)
+		return 0;
+
+	mptcp_remote_address((struct sock_common *)sk, &remote);
+
+	if (!mptcp_pm_addr_families_match(sk, local, &remote))
+		return 0;
+
+	msk->pm.extra_subflows++;
+	*addrs = remote;
+
+	return 1;
+}
+
+static unsigned int
+fill_remote_addresses_fullmesh(struct mptcp_sock *msk,
+			       struct mptcp_addr_info *local,
+			       struct mptcp_addr_info *addrs,
+			       int addrs_size)
+{
+	u8 limit_extra_subflows = mptcp_pm_get_limit_extra_subflows(msk);
+	bool deny_id0 = READ_ONCE(msk->pm.remote_deny_join_id0);
+	DECLARE_BITMAP(unavail_id, MPTCP_PM_MAX_ADDR_ID + 1);
+	struct sock *sk = (struct sock *)msk, *ssk;
+	struct mptcp_subflow_context *subflow;
+	int i = 0;
+
+	/* Forbid creation of new subflows matching existing ones, possibly
+	 * already created by incoming ADD_ADDR
+	 */
+	bitmap_zero(unavail_id, MPTCP_PM_MAX_ADDR_ID + 1);
+	mptcp_for_each_subflow(msk, subflow)
+		if (READ_ONCE(subflow->local_id) == local->id)
+			__set_bit(subflow->remote_id, unavail_id);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		ssk = mptcp_subflow_tcp_sock(subflow);
+		mptcp_remote_address((struct sock_common *)ssk, &addrs[i]);
+		addrs[i].id = READ_ONCE(subflow->remote_id);
+		if (deny_id0 && !addrs[i].id)
+			continue;
+
+		if (test_bit(addrs[i].id, unavail_id))
+			continue;
+
+		if (!mptcp_pm_addr_families_match(sk, local, &addrs[i]))
+			continue;
+
+		/* forbid creating multiple address towards this id */
+		__set_bit(addrs[i].id, unavail_id);
+		msk->pm.extra_subflows++;
+		i++;
+
+		if (msk->pm.extra_subflows >= limit_extra_subflows ||
+		    i == addrs_size)
+			break;
+	}
+
+	return i;
+}
+
+/* Fill all the remote addresses into the array addrs[],
+ * and return the array size.
+ */
+static unsigned int
+fill_remote_addresses_vec(struct mptcp_sock *msk, struct mptcp_addr_info *local,
+			  bool fullmesh, struct mptcp_addr_info *addrs,
+			  int addrs_size)
+{
+	/* Non-fullmesh: fill in the single entry corresponding to the primary
+	 * MPC subflow remote address, and return 1, corresponding to 1 entry.
+	 */
+	if (!fullmesh)
+		return fill_remote_addr(msk, local, addrs);
+
+	/* Fullmesh endpoint: fill all possible remote addresses */
+	return fill_remote_addresses_fullmesh(msk, local, addrs, addrs_size);
+}
+
+static struct mptcp_pm_addr_entry *
+__lookup_addr_by_id(struct pm_nl_pernet *pernet, unsigned int id)
+{
+	struct mptcp_pm_addr_entry *entry;
+
+	list_for_each_entry_rcu(entry, &pernet->endp_list, list,
+				lockdep_is_held(&pernet->lock)) {
+		if (entry->addr.id == id)
+			return entry;
+	}
+	return NULL;
+}
+
+static struct mptcp_pm_addr_entry *
+__lookup_addr(struct pm_nl_pernet *pernet, const struct mptcp_addr_info *info)
+{
+	struct mptcp_pm_addr_entry *entry;
+
+	list_for_each_entry_rcu(entry, &pernet->endp_list, list,
+				lockdep_is_held(&pernet->lock)) {
+		if (mptcp_addresses_equal(&entry->addr, info, entry->addr.port))
+			return entry;
+	}
+	return NULL;
+}
+
+static u8 mptcp_endp_get_local_id(struct mptcp_sock *msk,
+				  const struct mptcp_addr_info *addr)
+{
+	return msk->mpc_endpoint_id == addr->id ? 0 : addr->id;
+}
+
+/* Set mpc_endpoint_id, and send MP_PRIO for ID0 if needed */
+static void mptcp_mpc_endpoint_setup(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_pm_addr_entry *entry;
+	struct mptcp_addr_info mpc_addr;
+	struct pm_nl_pernet *pernet;
+	bool backup = false;
+
+	/* do lazy endpoint usage accounting for the MPC subflows */
+	if (likely(msk->pm.status & BIT(MPTCP_PM_MPC_ENDPOINT_ACCOUNTED)) ||
+	    !msk->first)
+		return;
+
+	subflow = mptcp_subflow_ctx(msk->first);
+	pernet = pm_nl_get_pernet_from_msk(msk);
+
+	mptcp_local_address((struct sock_common *)msk->first, &mpc_addr);
+	rcu_read_lock();
+	entry = __lookup_addr(pernet, &mpc_addr);
+	if (entry) {
+		__clear_bit(entry->addr.id, msk->pm.id_avail_bitmap);
+		msk->mpc_endpoint_id = entry->addr.id;
+		backup = !!(entry->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
+	}
+	rcu_read_unlock();
+
+	/* Send MP_PRIO */
+	if (backup)
+		mptcp_pm_send_ack(msk, subflow, true, backup);
+
+	msk->pm.status |= BIT(MPTCP_PM_MPC_ENDPOINT_ACCOUNTED);
+}
+
+static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
+{
+	u8 limit_extra_subflows = mptcp_pm_get_limit_extra_subflows(msk);
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+	u8 endp_subflow_max = mptcp_pm_get_endp_subflow_max(msk);
+	u8 endp_signal_max = mptcp_pm_get_endp_signal_max(msk);
+	struct sock *sk = (struct sock *)msk;
+	bool signal_and_subflow = false;
+	struct mptcp_pm_local local;
+
+	mptcp_mpc_endpoint_setup(msk);
+	if (!mptcp_is_fully_established(sk))
+		return;
+
+	pr_debug("local %d:%d signal %d:%d subflows %d:%d\n",
+		 msk->pm.local_addr_used, endp_subflow_max,
+		 msk->pm.add_addr_signaled, endp_signal_max,
+		 msk->pm.extra_subflows, limit_extra_subflows);
+
+	/* check first for announce */
+	if (msk->pm.add_addr_signaled < endp_signal_max) {
+		u8 endp_id;
+
+		/* due to racing events on both ends we can reach here while
+		 * previous add address is still running: if we invoke now
+		 * mptcp_pm_announce_addr(), that will fail and the
+		 * corresponding id will be marked as used.
+		 * Instead let the PM machinery reschedule us when the
+		 * current address announce will be completed.
+		 */
+		if (msk->pm.addr_signal & BIT(MPTCP_ADD_ADDR_SIGNAL))
+			return;
+
+		if (!select_signal_address(pernet, msk, &local))
+			goto subflow;
+
+		/* Special case for ID0: set the correct ID */
+		endp_id = local.addr.id;
+		if (endp_id == msk->mpc_endpoint_id)
+			local.addr.id = 0;
+
+		/* If the alloc fails, we are on memory pressure, not worth
+		 * continuing, and trying to create subflows.
+		 */
+		if (!mptcp_pm_announced_alloc(msk, &local.addr))
+			return;
+
+		__clear_bit(endp_id, msk->pm.id_avail_bitmap);
+		msk->pm.add_addr_signaled++;
+
+		mptcp_pm_announce_addr(msk, &local.addr, false);
+		mptcp_pm_addr_send_ack(msk);
+
+		if (local.flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
+			signal_and_subflow = true;
+	}
+
+subflow:
+	/* No need to try establishing subflows to remote id0 if not allowed */
+	if (mptcp_pm_add_addr_c_flag_case(msk))
+		goto exit;
+
+	/* check if should create a new subflow */
+	while (msk->pm.local_addr_used < endp_subflow_max &&
+	       msk->pm.extra_subflows < limit_extra_subflows) {
+		struct mptcp_addr_info addrs[MPTCP_PM_ADDR_MAX];
+		bool fullmesh;
+		int i, nr;
+
+		if (signal_and_subflow)
+			signal_and_subflow = false;
+		else if (!select_local_address(pernet, msk, &local))
+			break;
+
+		fullmesh = !!(local.flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
+
+		__clear_bit(local.addr.id, msk->pm.id_avail_bitmap);
+
+		/* Special case for ID0: set the correct ID */
+		if (local.addr.id == msk->mpc_endpoint_id)
+			local.addr.id = 0;
+		else /* local_addr_used is not decr for ID 0 */
+			msk->pm.local_addr_used++;
+
+		nr = fill_remote_addresses_vec(msk, &local.addr, fullmesh,
+					       addrs, ARRAY_SIZE(addrs));
+		if (nr == 0)
+			continue;
+
+		spin_unlock_bh(&msk->pm.lock);
+		for (i = 0; i < nr; i++)
+			__mptcp_subflow_connect(sk, &local, &addrs[i]);
+		spin_lock_bh(&msk->pm.lock);
+	}
+
+exit:
+	/* If an endpoint has both the signal and subflow flags, but it is not
+	 * possible to create subflows -- the 'while' loop body above never
+	 * executed --  then still mark the endp as used, which is somehow the
+	 * case. This avoids issues later when removing the endpoint and calling
+	 * __mark_subflow_endp_available(), which expects the increment here.
+	 */
+	if (signal_and_subflow && local.addr.id != msk->mpc_endpoint_id)
+		msk->pm.local_addr_used++;
+
+	mptcp_pm_nl_check_work_pending(msk);
+}
+
+static void mptcp_pm_nl_fully_established(struct mptcp_sock *msk)
+{
+	mptcp_pm_create_subflow_or_signal_addr(msk);
+}
+
+static void mptcp_pm_nl_subflow_established(struct mptcp_sock *msk)
+{
+	mptcp_pm_create_subflow_or_signal_addr(msk);
+}
+
+static unsigned int
+fill_local_addresses_vec_fullmesh(struct mptcp_sock *msk,
+				  struct mptcp_addr_info *remote,
+				  struct mptcp_pm_local *locals,
+				  int locals_size,
+				  bool c_flag_case)
+{
+	u8 limit_extra_subflows = mptcp_pm_get_limit_extra_subflows(msk);
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_addr_entry *entry;
+	struct mptcp_pm_local *local;
+	int i = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(entry, &pernet->endp_list, list) {
+		bool is_id0;
+
+		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_FULLMESH))
+			continue;
+
+		if (!mptcp_pm_addr_families_match(sk, &entry->addr, remote))
+			continue;
+
+		local = &locals[i];
+		local->addr = entry->addr;
+		local->flags = entry->flags;
+		local->ifindex = entry->ifindex;
+
+		is_id0 = local->addr.id == msk->mpc_endpoint_id;
+
+		if (c_flag_case &&
+		    (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)) {
+			__clear_bit(local->addr.id, msk->pm.id_avail_bitmap);
+
+			if (!is_id0)
+				msk->pm.local_addr_used++;
+		}
+
+		/* Special case for ID0: set the correct ID */
+		if (is_id0)
+			local->addr.id = 0;
+
+		msk->pm.extra_subflows++;
+		i++;
+
+		if (msk->pm.extra_subflows >= limit_extra_subflows ||
+		    i == locals_size)
+			break;
+	}
+	rcu_read_unlock();
+
+	return i;
+}
+
+static unsigned int
+fill_local_laminar_endp(struct mptcp_sock *msk, struct mptcp_addr_info *remote,
+			struct mptcp_pm_local *locals)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+	DECLARE_BITMAP(unavail_id, MPTCP_PM_MAX_ADDR_ID + 1);
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_addr_entry *entry;
+	struct mptcp_pm_local *local;
+	int found = 0;
+
+	/* Forbid creation of new subflows matching existing ones, possibly
+	 * already created by 'subflow' endpoints
+	 */
+	bitmap_zero(unavail_id, MPTCP_PM_MAX_ADDR_ID + 1);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if ((1 << inet_sk_state_load(ssk)) &
+		    (TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | TCPF_CLOSING |
+		     TCPF_CLOSE))
+			continue;
+
+		__set_bit(subflow_get_local_id(subflow), unavail_id);
+	}
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(entry, &pernet->endp_list, list) {
+		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_LAMINAR))
+			continue;
+
+		if (!mptcp_pm_addr_families_match(sk, &entry->addr, remote))
+			continue;
+
+		if (test_bit(mptcp_endp_get_local_id(msk, &entry->addr),
+			     unavail_id))
+			continue;
+
+		local = &locals[0];
+		local->addr = entry->addr;
+		local->flags = entry->flags;
+		local->ifindex = entry->ifindex;
+
+		if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
+			__clear_bit(local->addr.id, msk->pm.id_avail_bitmap);
+
+			if (local->addr.id != msk->mpc_endpoint_id)
+				msk->pm.local_addr_used++;
+		}
+
+		msk->pm.extra_subflows++;
+		found = 1;
+		break;
+	}
+	rcu_read_unlock();
+
+	return found;
+}
+
+static unsigned int
+fill_local_addresses_vec_c_flag(struct mptcp_sock *msk,
+				struct mptcp_addr_info *remote,
+				struct mptcp_pm_local *locals,
+				int locals_size)
+{
+	u8 limit_extra_subflows = mptcp_pm_get_limit_extra_subflows(msk);
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+	u8 endp_subflow_max = mptcp_pm_get_endp_subflow_max(msk);
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_local *local;
+	int i = 0;
+
+	while (msk->pm.local_addr_used < endp_subflow_max) {
+		local = &locals[i];
+
+		if (!select_local_address(pernet, msk, local))
+			break;
+
+		__clear_bit(local->addr.id, msk->pm.id_avail_bitmap);
+
+		if (!mptcp_pm_addr_families_match(sk, &local->addr, remote))
+			continue;
+
+		if (local->addr.id == msk->mpc_endpoint_id)
+			continue;
+
+		msk->pm.local_addr_used++;
+		msk->pm.extra_subflows++;
+		i++;
+
+		if (msk->pm.extra_subflows >= limit_extra_subflows ||
+		    i == locals_size)
+			break;
+	}
+
+	return i;
+}
+
+static unsigned int
+fill_local_address_any(struct mptcp_sock *msk, struct mptcp_addr_info *remote,
+		       struct mptcp_pm_local *local)
+{
+	struct sock *sk = (struct sock *)msk;
+
+	memset(local, 0, sizeof(*local));
+	local->addr.family =
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+			remote->family == AF_INET6 &&
+			ipv6_addr_v4mapped(&remote->addr6) ? AF_INET :
+#endif
+			remote->family;
+
+	if (!mptcp_pm_addr_families_match(sk, &local->addr, remote))
+		return 0;
+
+	msk->pm.extra_subflows++;
+
+	return 1;
+}
+
+/* Fill all the local addresses into the array addrs[],
+ * and return the array size.
+ */
+static unsigned int
+fill_local_addresses_vec(struct mptcp_sock *msk, struct mptcp_addr_info *remote,
+			 struct mptcp_pm_local *locals, int locals_size)
+{
+	bool c_flag_case = remote->id && mptcp_pm_add_addr_c_flag_case(msk);
+
+	/* If there is at least one MPTCP endpoint with a fullmesh flag */
+	if (mptcp_pm_get_endp_fullmesh_max(msk))
+		return fill_local_addresses_vec_fullmesh(msk, remote, locals,
+							 locals_size,
+							 c_flag_case);
+
+	/* If there is at least one MPTCP endpoint with a laminar flag */
+	if (mptcp_pm_get_endp_laminar_max(msk))
+		return fill_local_laminar_endp(msk, remote, locals);
+
+	/* Special case: peer sets the C flag, accept one ADD_ADDR if default
+	 * limits are used -- accepting no ADD_ADDR -- and use subflow endpoints
+	 */
+	if (c_flag_case)
+		return fill_local_addresses_vec_c_flag(msk, remote, locals,
+						       locals_size);
+
+	/* No special case: fill in the single 'IPADDRANY' local address */
+	return fill_local_address_any(msk, remote, &locals[0]);
+}
+
+static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
+{
+	u8 limit_add_addr_accepted = mptcp_pm_get_limit_add_addr_accepted(msk);
+	u8 limit_extra_subflows = mptcp_pm_get_limit_extra_subflows(msk);
+	struct mptcp_pm_local locals[MPTCP_PM_ADDR_MAX];
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_addr_info remote;
+	bool sf_created = false;
+	int i, nr;
+
+	pr_debug("accepted %d:%d remote family %d\n",
+		 msk->pm.add_addr_accepted, limit_add_addr_accepted,
+		 msk->pm.remote.family);
+
+	remote = msk->pm.remote;
+	mptcp_pm_announce_addr(msk, &remote, true);
+	mptcp_pm_addr_send_ack(msk);
+	mptcp_mpc_endpoint_setup(msk);
+
+	if (has_subflow_daddr(msk, &remote))
+		return;
+
+	/* pick id 0 port, if none is provided the remote address */
+	if (!remote.port)
+		remote.port = sk->sk_dport;
+
+	/* connect to the specified remote address, using whatever
+	 * local address the routing configuration will pick.
+	 */
+	nr = fill_local_addresses_vec(msk, &remote, locals, ARRAY_SIZE(locals));
+	if (nr == 0)
+		return;
+
+	spin_unlock_bh(&msk->pm.lock);
+	for (i = 0; i < nr; i++)
+		if (__mptcp_subflow_connect(sk, &locals[i], &remote) == 0)
+			sf_created = true;
+	spin_lock_bh(&msk->pm.lock);
+
+	if (sf_created) {
+		/* add_addr_accepted is not decr for ID 0 */
+		if (remote.id)
+			msk->pm.add_addr_accepted++;
+		if (msk->pm.add_addr_accepted >= limit_add_addr_accepted ||
+		    msk->pm.extra_subflows >= limit_extra_subflows)
+			WRITE_ONCE(msk->pm.accept_addr, false);
+	}
+}
+
+void mptcp_pm_nl_rm_addr(struct mptcp_sock *msk, u8 rm_id)
+{
+	if (rm_id && !WARN_ON_ONCE(msk->pm.add_addr_accepted == 0)) {
+		u8 limit_add_addr_accepted =
+			mptcp_pm_get_limit_add_addr_accepted(msk);
+
+		/* Note: if the subflow has been closed before, this
+		 * add_addr_accepted counter will not be decremented.
+		 */
+		if (--msk->pm.add_addr_accepted < limit_add_addr_accepted)
+			WRITE_ONCE(msk->pm.accept_addr, true);
+	}
+}
+
+static bool address_use_port(struct mptcp_pm_addr_entry *entry)
+{
+	return (entry->flags &
+		(MPTCP_PM_ADDR_FLAG_SIGNAL | MPTCP_PM_ADDR_FLAG_SUBFLOW)) ==
+		MPTCP_PM_ADDR_FLAG_SIGNAL;
+}
+
+/* caller must ensure the RCU grace period is already elapsed */
+static void __mptcp_pm_release_addr_entry(struct mptcp_pm_addr_entry *entry)
+{
+	if (entry->lsk)
+		sock_release(entry->lsk);
+	kfree(entry);
+}
+
+static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
+					     struct mptcp_pm_addr_entry *entry,
+					     bool replace)
+{
+	struct mptcp_pm_addr_entry *cur, *del_entry = NULL;
+	int ret = -EINVAL;
+	u8 addr_max;
+
+	spin_lock_bh(&pernet->lock);
+	/* to keep the code simple, don't do IDR-like allocation for address ID,
+	 * just bail when we exceed limits
+	 */
+	if (pernet->next_id == MPTCP_PM_MAX_ADDR_ID)
+		pernet->next_id = 1;
+	if (pernet->endpoints == MPTCP_PM_MAX_ADDR_ID) {
+		ret = -ERANGE;
+		goto out;
+	}
+	if (test_bit(entry->addr.id, pernet->id_bitmap)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	/* do not insert duplicate address, differentiate on port only
+	 * singled addresses
+	 */
+	if (!address_use_port(entry))
+		entry->addr.port = 0;
+	list_for_each_entry(cur, &pernet->endp_list, list) {
+		if (mptcp_addresses_equal(&cur->addr, &entry->addr,
+					  cur->addr.port || entry->addr.port)) {
+			/* allow replacing the exiting endpoint only if such
+			 * endpoint is an implicit one and the user-space
+			 * did not provide an endpoint id
+			 */
+			if (!(cur->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT)) {
+				ret = -EEXIST;
+				goto out;
+			}
+			if (entry->addr.id)
+				goto out;
+
+			/* allow callers that only need to look up the local
+			 * addr's id to skip replacement. This allows them to
+			 * avoid calling synchronize_rcu in the packet recv
+			 * path.
+			 */
+			if (!replace) {
+				kfree(entry);
+				ret = cur->addr.id;
+				goto out;
+			}
+
+			pernet->endpoints--;
+			entry->addr.id = cur->addr.id;
+			list_del_rcu(&cur->list);
+			del_entry = cur;
+			break;
+		}
+	}
+
+	if (!entry->addr.id) {
+find_next:
+		entry->addr.id = find_next_zero_bit(pernet->id_bitmap,
+						    MPTCP_PM_MAX_ADDR_ID + 1,
+						    pernet->next_id);
+		if (!entry->addr.id && pernet->next_id != 1) {
+			pernet->next_id = 1;
+			goto find_next;
+		}
+	}
+
+	if (!entry->addr.id)
+		goto out;
+
+	__set_bit(entry->addr.id, pernet->id_bitmap);
+	if (entry->addr.id > pernet->next_id)
+		pernet->next_id = entry->addr.id;
+
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL) {
+		addr_max = pernet->endp_signal_max;
+		WRITE_ONCE(pernet->endp_signal_max, addr_max + 1);
+	}
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
+		addr_max = pernet->endp_subflow_max;
+		WRITE_ONCE(pernet->endp_subflow_max, addr_max + 1);
+	}
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_LAMINAR) {
+		addr_max = pernet->endp_laminar_max;
+		WRITE_ONCE(pernet->endp_laminar_max, addr_max + 1);
+	}
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_FULLMESH) {
+		addr_max = pernet->endp_fullmesh_max;
+		WRITE_ONCE(pernet->endp_fullmesh_max, addr_max + 1);
+	}
+
+	pernet->endpoints++;
+	if (!entry->addr.port)
+		list_add_tail_rcu(&entry->list, &pernet->endp_list);
+	else
+		list_add_rcu(&entry->list, &pernet->endp_list);
+	ret = entry->addr.id;
+
+out:
+	spin_unlock_bh(&pernet->lock);
+
+	/* just replaced an existing entry, free it */
+	if (del_entry) {
+		synchronize_rcu();
+		__mptcp_pm_release_addr_entry(del_entry);
+	}
+	return ret;
+}
+
+static struct lock_class_key mptcp_slock_keys[2];
+static struct lock_class_key mptcp_keys[2];
+
+static int mptcp_pm_nl_create_listen_socket(struct sock *sk,
+					    struct mptcp_pm_addr_entry *entry)
+{
+	bool is_ipv6 = entry->addr.family == AF_INET6;
+	int addrlen = sizeof(struct sockaddr_in);
+	struct sockaddr_storage addr;
+	struct sock *newsk, *ssk;
+	int backlog = 1024;
+	int err;
+
+	err = sock_create_kern(sock_net(sk), entry->addr.family,
+			       SOCK_STREAM, IPPROTO_MPTCP, &entry->lsk);
+	if (err)
+		return err;
+
+	newsk = entry->lsk->sk;
+	if (!newsk)
+		return -EINVAL;
+
+	/* The subflow socket lock is acquired in a nested to the msk one
+	 * in several places, even by the TCP stack, and this msk is a kernel
+	 * socket: lockdep complains. Instead of propagating the _nested
+	 * modifiers in several places, re-init the lock class for the msk
+	 * socket to an mptcp specific one.
+	 */
+	sock_lock_init_class_and_name(newsk,
+				      is_ipv6 ? "mlock-AF_INET6" : "mlock-AF_INET",
+				      &mptcp_slock_keys[is_ipv6],
+				      is_ipv6 ? "msk_lock-AF_INET6" : "msk_lock-AF_INET",
+				      &mptcp_keys[is_ipv6]);
+
+	lock_sock(newsk);
+	ssk = __mptcp_nmpc_sk(mptcp_sk(newsk));
+	release_sock(newsk);
+	if (IS_ERR(ssk))
+		return PTR_ERR(ssk);
+
+	mptcp_info2sockaddr(&entry->addr, &addr, entry->addr.family);
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (entry->addr.family == AF_INET6)
+		addrlen = sizeof(struct sockaddr_in6);
+#endif
+	if (ssk->sk_family == AF_INET)
+		err = inet_bind_sk(ssk, (struct sockaddr_unsized *)&addr, addrlen);
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (ssk->sk_family == AF_INET6)
+		err = inet6_bind_sk(ssk, (struct sockaddr_unsized *)&addr, addrlen);
+#endif
+	if (err)
+		return err;
+
+	/* We don't use mptcp_set_state() here because it needs to be called
+	 * under the msk socket lock. For the moment, that will not bring
+	 * anything more than only calling inet_sk_state_store(), because the
+	 * old status is known (TCP_CLOSE).
+	 */
+	inet_sk_state_store(newsk, TCP_LISTEN);
+	lock_sock(ssk);
+	WRITE_ONCE(mptcp_subflow_ctx(ssk)->pm_listener, true);
+	err = __inet_listen_sk(ssk, backlog);
+	if (!err)
+		mptcp_event_pm_listener(ssk, MPTCP_EVENT_LISTENER_CREATED);
+	release_sock(ssk);
+	return err;
+}
+
+int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk,
+			     struct mptcp_pm_addr_entry *skc)
+{
+	struct mptcp_pm_addr_entry *entry;
+	struct pm_nl_pernet *pernet;
+	int ret;
+
+	pernet = pm_nl_get_pernet_from_msk(msk);
+
+	rcu_read_lock();
+	entry = __lookup_addr(pernet, &skc->addr);
+	ret = entry ? entry->addr.id : -1;
+	rcu_read_unlock();
+	if (ret >= 0)
+		return ret;
+
+	/* address not found, add to local list */
+	entry = kmemdup(skc, sizeof(*skc), GFP_ATOMIC);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->addr.port = 0;
+	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, false);
+	if (ret < 0)
+		kfree(entry);
+
+	return ret;
+}
+
+bool mptcp_pm_nl_is_backup(struct mptcp_sock *msk, struct mptcp_addr_info *skc)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+	struct mptcp_pm_addr_entry *entry;
+	bool backup;
+
+	rcu_read_lock();
+	entry = __lookup_addr(pernet, skc);
+	backup = entry && !!(entry->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
+	rcu_read_unlock();
+
+	return backup;
+}
+
+static int mptcp_nl_add_subflow_or_signal_addr(struct net *net,
+					       struct mptcp_addr_info *addr)
+{
+	struct mptcp_sock *msk;
+	long s_slot = 0, s_num = 0;
+
+	while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+		struct sock *sk = (struct sock *)msk;
+		struct mptcp_addr_info mpc_addr;
+
+		if (!READ_ONCE(msk->fully_established) ||
+		    mptcp_pm_is_userspace(msk))
+			goto next;
+
+		/* if the endp linked to the init sf is re-added with a != ID */
+		mptcp_local_address((struct sock_common *)msk, &mpc_addr);
+
+		lock_sock(sk);
+		spin_lock_bh(&msk->pm.lock);
+		if (mptcp_addresses_equal(addr, &mpc_addr, addr->port))
+			msk->mpc_endpoint_id = addr->id;
+		mptcp_pm_create_subflow_or_signal_addr(msk);
+		spin_unlock_bh(&msk->pm.lock);
+		release_sock(sk);
+
+next:
+		sock_put(sk);
+		cond_resched();
+	}
+
+	return 0;
+}
+
+/* Add an MPTCP endpoint */
+int mptcp_pm_nl_add_addr_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct mptcp_pm_addr_entry addr, *entry;
+	struct nlattr *attr;
+	int ret;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ENDPOINT_ADDR))
+		return -EINVAL;
+
+	attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
+	ret = mptcp_pm_parse_entry(attr, info, true, &addr);
+	if (ret < 0)
+		return ret;
+
+	if (addr.addr.port && !address_use_port(&addr)) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "flags must have signal and not subflow when using port");
+		return -EINVAL;
+	}
+
+	if (addr.flags & MPTCP_PM_ADDR_FLAG_SIGNAL &&
+	    addr.flags & MPTCP_PM_ADDR_FLAG_FULLMESH) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "flags mustn't have both signal and fullmesh");
+		return -EINVAL;
+	}
+
+	if (addr.flags & MPTCP_PM_ADDR_FLAG_IMPLICIT) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "can't create IMPLICIT endpoint");
+		return -EINVAL;
+	}
+
+	entry = kmemdup(&addr, sizeof(addr), GFP_KERNEL_ACCOUNT);
+	if (!entry) {
+		GENL_SET_ERR_MSG(info, "can't allocate addr");
+		return -ENOMEM;
+	}
+
+	if (entry->addr.port) {
+		ret = mptcp_pm_nl_create_listen_socket(skb->sk, entry);
+		if (ret) {
+			GENL_SET_ERR_MSG_FMT(info, "create listen socket error: %d", ret);
+			goto out_free;
+		}
+	}
+	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, true);
+	if (ret < 0) {
+		GENL_SET_ERR_MSG_FMT(info, "too many addresses or duplicate one: %d", ret);
+		goto out_free;
+	}
+
+	mptcp_nl_add_subflow_or_signal_addr(sock_net(skb->sk), &entry->addr);
+	return 0;
+
+out_free:
+	__mptcp_pm_release_addr_entry(entry);
+	return ret;
+}
+
+static void mptcp_pm_remove_announced(struct mptcp_sock *msk,
+				      const struct mptcp_addr_info *addr,
+				      bool force)
+{
+	struct mptcp_rm_list list = { .nr = 0 };
+	bool announced;
+
+	list.ids[list.nr++] = mptcp_endp_get_local_id(msk, addr);
+
+	announced = mptcp_pm_announced_remove(msk, addr);
+	if (announced || force) {
+		spin_lock_bh(&msk->pm.lock);
+		if (announced)
+			msk->pm.add_addr_signaled--;
+		mptcp_pm_remove_addr(msk, &list);
+		spin_unlock_bh(&msk->pm.lock);
+	}
+}
+
+static void __mark_subflow_endp_available(struct mptcp_sock *msk, u8 id)
+{
+	/* If it was marked as used, and not ID 0, decrement local_addr_used */
+	if (!__test_and_set_bit(id ? : msk->mpc_endpoint_id, msk->pm.id_avail_bitmap) &&
+	    id && !WARN_ON_ONCE(msk->pm.local_addr_used == 0))
+		msk->pm.local_addr_used--;
+}
+
+static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
+						   const struct mptcp_pm_addr_entry *entry)
+{
+	const struct mptcp_addr_info *addr = &entry->addr;
+	struct mptcp_rm_list list = { .nr = 1 };
+	long s_slot = 0, s_num = 0;
+	struct mptcp_sock *msk;
+
+	pr_debug("remove_id=%d\n", addr->id);
+
+	while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+		struct sock *sk = (struct sock *)msk;
+		bool remove_subflow;
+
+		if (mptcp_pm_is_userspace(msk))
+			goto next;
+
+		lock_sock(sk);
+		remove_subflow = mptcp_pm_has_subflow_saddr(msk, addr);
+		mptcp_pm_remove_announced(msk, addr, remove_subflow &&
+					  !(entry->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT));
+
+		list.ids[0] = mptcp_endp_get_local_id(msk, addr);
+
+		spin_lock_bh(&msk->pm.lock);
+		if (remove_subflow)
+			mptcp_pm_rm_subflow(msk, &list);
+		if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
+			__mark_subflow_endp_available(msk, list.ids[0]);
+		else /* mark endp ID as available, e.g. Signal or MPC endp */
+			__set_bit(addr->id, msk->pm.id_avail_bitmap);
+		spin_unlock_bh(&msk->pm.lock);
+
+		if (msk->mpc_endpoint_id == entry->addr.id)
+			msk->mpc_endpoint_id = 0;
+		release_sock(sk);
+
+next:
+		sock_put(sk);
+		cond_resched();
+	}
+
+	return 0;
+}
+
+static int mptcp_nl_remove_id_zero_address(struct net *net,
+					   struct mptcp_addr_info *addr)
+{
+	struct mptcp_rm_list list = { .nr = 0 };
+	long s_slot = 0, s_num = 0;
+	struct mptcp_sock *msk;
+
+	list.ids[list.nr++] = 0;
+
+	while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+		struct sock *sk = (struct sock *)msk;
+		struct mptcp_addr_info msk_local;
+		struct mptcp_addr_info anno_addr;
+		bool announced;
+
+		if (list_empty(&msk->conn_list) || mptcp_pm_is_userspace(msk))
+			goto next;
+
+		mptcp_local_address((struct sock_common *)msk, &msk_local);
+		if (!mptcp_addresses_equal(&msk_local, addr, addr->port))
+			goto next;
+
+		lock_sock(sk);
+		/* Drop a possibly pending ADD_ADDR for this address. */
+		anno_addr = msk_local;
+		anno_addr.port = 0;
+		announced = mptcp_pm_announced_remove(msk, &anno_addr);
+		spin_lock_bh(&msk->pm.lock);
+		if (announced)
+			msk->pm.add_addr_signaled--;
+		mptcp_pm_remove_addr(msk, &list);
+		mptcp_pm_rm_subflow(msk, &list);
+		__mark_subflow_endp_available(msk, 0);
+		spin_unlock_bh(&msk->pm.lock);
+		release_sock(sk);
+
+next:
+		sock_put(sk);
+		cond_resched();
+	}
+
+	return 0;
+}
+
+/* Remove an MPTCP endpoint */
+int mptcp_pm_nl_del_addr_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct mptcp_pm_addr_entry addr, *entry;
+	struct nlattr *attr;
+	u8 addr_max;
+	int ret;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ENDPOINT_ADDR))
+		return -EINVAL;
+
+	attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
+	ret = mptcp_pm_parse_entry(attr, info, false, &addr);
+	if (ret < 0)
+		return ret;
+
+	/* the zero id address is special: the first address used by the msk
+	 * always gets such an id, so different subflows can have different zero
+	 * id addresses. Additionally zero id is not accounted for in id_bitmap.
+	 * Let's use an 'mptcp_rm_list' instead of the common remove code.
+	 */
+	if (addr.addr.id == 0)
+		return mptcp_nl_remove_id_zero_address(sock_net(skb->sk), &addr.addr);
+
+	spin_lock_bh(&pernet->lock);
+	entry = __lookup_addr_by_id(pernet, addr.addr.id);
+	if (!entry) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr, "address not found");
+		spin_unlock_bh(&pernet->lock);
+		return -EINVAL;
+	}
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL) {
+		addr_max = pernet->endp_signal_max;
+		WRITE_ONCE(pernet->endp_signal_max, addr_max - 1);
+	}
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
+		addr_max = pernet->endp_subflow_max;
+		WRITE_ONCE(pernet->endp_subflow_max, addr_max - 1);
+	}
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_LAMINAR) {
+		addr_max = pernet->endp_laminar_max;
+		WRITE_ONCE(pernet->endp_laminar_max, addr_max - 1);
+	}
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_FULLMESH) {
+		addr_max = pernet->endp_fullmesh_max;
+		WRITE_ONCE(pernet->endp_fullmesh_max, addr_max - 1);
+	}
+
+	pernet->endpoints--;
+	list_del_rcu(&entry->list);
+	__clear_bit(entry->addr.id, pernet->id_bitmap);
+	spin_unlock_bh(&pernet->lock);
+
+	mptcp_nl_remove_subflow_and_signal_addr(sock_net(skb->sk), entry);
+	synchronize_rcu();
+	__mptcp_pm_release_addr_entry(entry);
+
+	return ret;
+}
+
+static void mptcp_pm_flush_addrs_and_subflows(struct mptcp_sock *msk,
+					      struct list_head *rm_list,
+					      struct mptcp_pm_addr_entry *entry)
+{
+	struct mptcp_rm_list alist, slist;
+	bool more;
+
+again:
+	alist.nr = 0;
+	slist.nr = 0;
+	more = false;
+
+	entry = list_prepare_entry(entry, rm_list, list);
+	list_for_each_entry_continue(entry, rm_list, list) {
+		if (mptcp_pm_has_subflow_saddr(msk, &entry->addr))
+			slist.ids[slist.nr++] = mptcp_endp_get_local_id(msk, &entry->addr);
+
+		if (mptcp_pm_announced_remove(msk, &entry->addr))
+			alist.ids[alist.nr++] = mptcp_endp_get_local_id(msk, &entry->addr);
+
+		if (slist.nr == MPTCP_RM_IDS_MAX ||
+		    alist.nr == MPTCP_RM_IDS_MAX) {
+			more = !list_is_last(&entry->list, rm_list);
+			break;
+		}
+	}
+
+	spin_lock_bh(&msk->pm.lock);
+	if (alist.nr) {
+		msk->pm.add_addr_signaled -= alist.nr;
+		mptcp_pm_remove_addr(msk, &alist);
+	}
+	if (slist.nr)
+		mptcp_pm_rm_subflow(msk, &slist);
+	/* Reset counters: maybe some subflows have been removed before */
+	if (!more) {
+		bitmap_fill(msk->pm.id_avail_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
+		msk->pm.local_addr_used = 0;
+	}
+	spin_unlock_bh(&msk->pm.lock);
+
+	if (more)
+		goto again;
+}
+
+static void mptcp_nl_flush_addrs_list(struct net *net,
+				      struct list_head *rm_list)
+{
+	long s_slot = 0, s_num = 0;
+	struct mptcp_sock *msk;
+
+	if (list_empty(rm_list))
+		return;
+
+	while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+		struct sock *sk = (struct sock *)msk;
+
+		if (!mptcp_pm_is_userspace(msk)) {
+			lock_sock(sk);
+			mptcp_pm_flush_addrs_and_subflows(msk, rm_list, NULL);
+			release_sock(sk);
+		}
+
+		sock_put(sk);
+		cond_resched();
+	}
+}
+
+/* caller must ensure the RCU grace period is already elapsed */
+static void __flush_addrs(struct list_head *list)
+{
+	while (!list_empty(list)) {
+		struct mptcp_pm_addr_entry *cur;
+
+		cur = list_entry(list->next,
+				 struct mptcp_pm_addr_entry, list);
+		list_del_rcu(&cur->list);
+		__mptcp_pm_release_addr_entry(cur);
+	}
+}
+
+static void __reset_counters(struct pm_nl_pernet *pernet)
+{
+	WRITE_ONCE(pernet->endp_signal_max, 0);
+	WRITE_ONCE(pernet->endp_subflow_max, 0);
+	WRITE_ONCE(pernet->endp_laminar_max, 0);
+	WRITE_ONCE(pernet->endp_fullmesh_max, 0);
+	pernet->endpoints = 0;
+}
+
+int mptcp_pm_nl_flush_addrs_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct list_head free_list;
+
+	spin_lock_bh(&pernet->lock);
+	free_list = pernet->endp_list;
+	INIT_LIST_HEAD_RCU(&pernet->endp_list);
+	__reset_counters(pernet);
+	pernet->next_id = 1;
+	bitmap_zero(pernet->id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
+	spin_unlock_bh(&pernet->lock);
+
+	if (free_list.next == &pernet->endp_list)
+		return 0;
+
+	synchronize_rcu();
+
+	/* Adjust the pointers to free_list instead of pernet->endp_list */
+	free_list.prev->next = &free_list;
+	free_list.next->prev = &free_list;
+
+	mptcp_nl_flush_addrs_list(sock_net(skb->sk), &free_list);
+	__flush_addrs(&free_list);
+	return 0;
+}
+
+int mptcp_pm_nl_get_addr(u8 id, struct mptcp_pm_addr_entry *addr,
+			 struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct mptcp_pm_addr_entry *entry;
+	int ret = -EINVAL;
+
+	rcu_read_lock();
+	entry = __lookup_addr_by_id(pernet, id);
+	if (entry) {
+		*addr = *entry;
+		ret = 0;
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
+int mptcp_pm_nl_dump_addr(struct sk_buff *msg,
+			  struct netlink_callback *cb)
+{
+	struct net *net = sock_net(msg->sk);
+	struct mptcp_pm_addr_entry *entry;
+	struct pm_nl_pernet *pernet;
+	int id = cb->args[0];
+	int i;
+
+	pernet = pm_nl_get_pernet(net);
+
+	rcu_read_lock();
+	for (i = id; i < MPTCP_PM_MAX_ADDR_ID + 1; i++) {
+		if (test_bit(i, pernet->id_bitmap)) {
+			entry = __lookup_addr_by_id(pernet, i);
+			if (!entry)
+				break;
+
+			if (entry->addr.id <= id)
+				continue;
+
+			if (mptcp_pm_genl_fill_addr(msg, cb, entry) < 0)
+				break;
+
+			id = entry->addr.id;
+		}
+	}
+	rcu_read_unlock();
+
+	cb->args[0] = id;
+	return msg->len;
+}
+
+static int parse_limit(struct genl_info *info, int id, unsigned int *limit)
+{
+	struct nlattr *attr = info->attrs[id];
+
+	if (!attr)
+		return 0;
+
+	*limit = nla_get_u32(attr);
+	if (*limit > MPTCP_PM_SUBFLOWS_MAX) {
+		NL_SET_ERR_MSG_ATTR_FMT(info->extack, attr,
+					"limit greater than maximum (%u)",
+					MPTCP_PM_SUBFLOWS_MAX);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int mptcp_pm_nl_set_limits_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	unsigned int rcv_addrs, subflows;
+	int ret;
+
+	spin_lock_bh(&pernet->lock);
+	rcv_addrs = pernet->limit_add_addr_accepted;
+	ret = parse_limit(info, MPTCP_PM_ATTR_RCV_ADD_ADDRS, &rcv_addrs);
+	if (ret)
+		goto unlock;
+
+	subflows = pernet->limit_extra_subflows;
+	ret = parse_limit(info, MPTCP_PM_ATTR_SUBFLOWS, &subflows);
+	if (ret)
+		goto unlock;
+
+	WRITE_ONCE(pernet->limit_add_addr_accepted, rcv_addrs);
+	WRITE_ONCE(pernet->limit_extra_subflows, subflows);
+
+unlock:
+	spin_unlock_bh(&pernet->lock);
+	return ret;
+}
+
+int mptcp_pm_nl_get_limits_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct sk_buff *msg;
+	void *reply;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	reply = genlmsg_put_reply(msg, info, &mptcp_genl_family, 0,
+				  MPTCP_PM_CMD_GET_LIMITS);
+	if (!reply)
+		goto fail;
+
+	if (nla_put_u32(msg, MPTCP_PM_ATTR_RCV_ADD_ADDRS,
+			READ_ONCE(pernet->limit_add_addr_accepted)))
+		goto fail;
+
+	if (nla_put_u32(msg, MPTCP_PM_ATTR_SUBFLOWS,
+			READ_ONCE(pernet->limit_extra_subflows)))
+		goto fail;
+
+	genlmsg_end(msg, reply);
+	return genlmsg_reply(msg, info);
+
+fail:
+	GENL_SET_ERR_MSG(info, "not enough space in Netlink message");
+	nlmsg_free(msg);
+	return -EMSGSIZE;
+}
+
+static void mptcp_pm_nl_fullmesh(struct mptcp_sock *msk,
+				 struct mptcp_addr_info *addr)
+{
+	struct mptcp_rm_list list = { .nr = 0 };
+
+	list.ids[list.nr++] = mptcp_endp_get_local_id(msk, addr);
+
+	spin_lock_bh(&msk->pm.lock);
+	mptcp_pm_rm_subflow(msk, &list);
+	__mark_subflow_endp_available(msk, list.ids[0]);
+	mptcp_pm_create_subflow_or_signal_addr(msk);
+	spin_unlock_bh(&msk->pm.lock);
+}
+
+static void mptcp_pm_nl_set_flags_all(struct net *net,
+				      struct mptcp_pm_addr_entry *local,
+				      u8 changed)
+{
+	u8 is_subflow = !!(local->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW);
+	u8 bkup = !!(local->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
+	long s_slot = 0, s_num = 0;
+	struct mptcp_sock *msk;
+
+	if (changed == MPTCP_PM_ADDR_FLAG_FULLMESH && !is_subflow)
+		return;
+
+	while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+		struct sock *sk = (struct sock *)msk;
+
+		if (list_empty(&msk->conn_list) || mptcp_pm_is_userspace(msk))
+			goto next;
+
+		lock_sock(sk);
+		if (changed & MPTCP_PM_ADDR_FLAG_BACKUP)
+			mptcp_pm_mp_prio_send_ack(msk, &local->addr, NULL, bkup);
+		/* Subflows will only be recreated if the SUBFLOW flag is set */
+		if (is_subflow && (changed & MPTCP_PM_ADDR_FLAG_FULLMESH))
+			mptcp_pm_nl_fullmesh(msk, &local->addr);
+		release_sock(sk);
+
+next:
+		sock_put(sk);
+		cond_resched();
+	}
+}
+
+int mptcp_pm_nl_set_flags(struct mptcp_pm_addr_entry *local,
+			  struct genl_info *info)
+{
+	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	u8 changed, mask = MPTCP_PM_ADDR_FLAG_BACKUP |
+			   MPTCP_PM_ADDR_FLAG_FULLMESH;
+	struct net *net = genl_info_net(info);
+	struct mptcp_pm_addr_entry *entry;
+	struct pm_nl_pernet *pernet;
+	u8 lookup_by_id = 0;
+
+	pernet = pm_nl_get_pernet(net);
+
+	if (local->addr.family == AF_UNSPEC) {
+		lookup_by_id = 1;
+		if (!local->addr.id) {
+			NL_SET_ERR_MSG_ATTR(info->extack, attr,
+					    "missing address ID");
+			return -EOPNOTSUPP;
+		}
+	}
+
+	spin_lock_bh(&pernet->lock);
+	entry = lookup_by_id ? __lookup_addr_by_id(pernet, local->addr.id) :
+			       __lookup_addr(pernet, &local->addr);
+	if (!entry) {
+		spin_unlock_bh(&pernet->lock);
+		NL_SET_ERR_MSG_ATTR(info->extack, attr, "address not found");
+		return -EINVAL;
+	}
+	if ((local->flags & MPTCP_PM_ADDR_FLAG_FULLMESH) &&
+	    (entry->flags & (MPTCP_PM_ADDR_FLAG_SIGNAL |
+			     MPTCP_PM_ADDR_FLAG_IMPLICIT))) {
+		spin_unlock_bh(&pernet->lock);
+		NL_SET_ERR_MSG_ATTR(info->extack, attr, "invalid addr flags");
+		return -EINVAL;
+	}
+
+	changed = (local->flags ^ entry->flags) & mask;
+	entry->flags = (entry->flags & ~mask) | (local->flags & mask);
+	*local = *entry;
+
+	if (changed & MPTCP_PM_ADDR_FLAG_FULLMESH) {
+		u8 addr_max = pernet->endp_fullmesh_max;
+
+		if (entry->flags & MPTCP_PM_ADDR_FLAG_FULLMESH)
+			addr_max++;
+		else
+			addr_max--;
+
+		WRITE_ONCE(pernet->endp_fullmesh_max, addr_max);
+	}
+
+	spin_unlock_bh(&pernet->lock);
+
+	mptcp_pm_nl_set_flags_all(net, local, changed);
+	return 0;
+}
+
+bool mptcp_pm_nl_check_work_pending(struct mptcp_sock *msk)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet_from_msk(msk);
+
+	if (msk->pm.extra_subflows == mptcp_pm_get_limit_extra_subflows(msk) ||
+	    (find_next_and_bit(pernet->id_bitmap, msk->pm.id_avail_bitmap,
+			       MPTCP_PM_MAX_ADDR_ID + 1, 0) == MPTCP_PM_MAX_ADDR_ID + 1)) {
+		WRITE_ONCE(msk->pm.work_pending, false);
+		return false;
+	}
+	return true;
+}
+
+/* Called under PM lock */
+void __mptcp_pm_kernel_worker(struct mptcp_sock *msk)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+
+	if (pm->status & BIT(MPTCP_PM_ADD_ADDR_RECEIVED)) {
+		pm->status &= ~BIT(MPTCP_PM_ADD_ADDR_RECEIVED);
+		mptcp_pm_nl_add_addr_received(msk);
+	}
+	if (pm->status & BIT(MPTCP_PM_ESTABLISHED)) {
+		pm->status &= ~BIT(MPTCP_PM_ESTABLISHED);
+		mptcp_pm_nl_fully_established(msk);
+	}
+	if (pm->status & BIT(MPTCP_PM_SUBFLOW_ESTABLISHED)) {
+		pm->status &= ~BIT(MPTCP_PM_SUBFLOW_ESTABLISHED);
+		mptcp_pm_nl_subflow_established(msk);
+	}
+}
+
+static int __net_init pm_nl_init_net(struct net *net)
+{
+	struct pm_nl_pernet *pernet = pm_nl_get_pernet(net);
+
+	INIT_LIST_HEAD_RCU(&pernet->endp_list);
+
+	/* Cit. 2 subflows ought to be enough for anybody. */
+	pernet->limit_extra_subflows = 2;
+	pernet->next_id = 1;
+	spin_lock_init(&pernet->lock);
+
+	/* No need to initialize other pernet fields, the struct is zeroed at
+	 * allocation time.
+	 */
+
+	return 0;
+}
+
+static void __net_exit pm_nl_exit_net(struct list_head *net_list)
+{
+	struct net *net;
+
+	list_for_each_entry(net, net_list, exit_list) {
+		struct pm_nl_pernet *pernet = pm_nl_get_pernet(net);
+
+		/* net is removed from namespace list, can't race with
+		 * other modifiers, also netns core already waited for a
+		 * RCU grace period.
+		 */
+		__flush_addrs(&pernet->endp_list);
+	}
+}
+
+static struct pernet_operations mptcp_pm_pernet_ops = {
+	.init = pm_nl_init_net,
+	.exit_batch = pm_nl_exit_net,
+	.id = &pm_nl_pernet_id,
+	.size = sizeof(struct pm_nl_pernet),
+};
+
+struct mptcp_pm_ops mptcp_pm_kernel = {
+	.name			= "kernel",
+	.owner			= THIS_MODULE,
+};
+
+void __init mptcp_pm_kernel_register(void)
+{
+	if (register_pernet_subsys(&mptcp_pm_pernet_ops) < 0)
+		panic("Failed to register MPTCP PM pernet subsystem.\n");
+
+	mptcp_pm_register(&mptcp_pm_kernel);
+}
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
new file mode 100644
index 000000000..7aa42de9c
--- /dev/null
+++ b/net/mptcp/pm_netlink.c
@@ -0,0 +1,646 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2020, Red Hat, Inc.
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include "protocol.h"
+#include "mptcp_pm_gen.h"
+
+#define MPTCP_PM_CMD_GRP_OFFSET       0
+#define MPTCP_PM_EV_GRP_OFFSET        1
+
+static const struct genl_multicast_group mptcp_pm_mcgrps[] = {
+	[MPTCP_PM_CMD_GRP_OFFSET]	= { .name = MPTCP_PM_CMD_GRP_NAME, },
+	[MPTCP_PM_EV_GRP_OFFSET]        = { .name = MPTCP_PM_EV_GRP_NAME,
+					    .flags = GENL_MCAST_CAP_NET_ADMIN,
+					  },
+};
+
+static int mptcp_pm_family_to_addr(int family)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (family == AF_INET6)
+		return MPTCP_PM_ADDR_ATTR_ADDR6;
+#endif
+	return MPTCP_PM_ADDR_ATTR_ADDR4;
+}
+
+static int mptcp_pm_parse_pm_addr_attr(struct nlattr *tb[],
+				       const struct nlattr *attr,
+				       struct genl_info *info,
+				       struct mptcp_addr_info *addr,
+				       bool require_family)
+{
+	int err, addr_addr;
+
+	if (!attr) {
+		GENL_SET_ERR_MSG(info, "missing address info");
+		return -EINVAL;
+	}
+
+	/* no validation needed - was already done via nested policy */
+	err = nla_parse_nested_deprecated(tb, MPTCP_PM_ADDR_ATTR_MAX, attr,
+					  mptcp_pm_address_nl_policy, info->extack);
+	if (err)
+		return err;
+
+	if (tb[MPTCP_PM_ADDR_ATTR_ID])
+		addr->id = nla_get_u8(tb[MPTCP_PM_ADDR_ATTR_ID]);
+
+	if (!tb[MPTCP_PM_ADDR_ATTR_FAMILY]) {
+		if (!require_family)
+			return 0;
+
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "missing family");
+		return -EINVAL;
+	}
+
+	addr->family = nla_get_u16(tb[MPTCP_PM_ADDR_ATTR_FAMILY]);
+	if (addr->family != AF_INET
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	    && addr->family != AF_INET6
+#endif
+	    ) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "unknown address family");
+		return -EINVAL;
+	}
+	addr_addr = mptcp_pm_family_to_addr(addr->family);
+	if (!tb[addr_addr]) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "missing address data");
+		return -EINVAL;
+	}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (addr->family == AF_INET6)
+		addr->addr6 = nla_get_in6_addr(tb[addr_addr]);
+	else
+#endif
+		addr->addr.s_addr = nla_get_in_addr(tb[addr_addr]);
+
+	if (tb[MPTCP_PM_ADDR_ATTR_PORT])
+		addr->port = htons(nla_get_u16(tb[MPTCP_PM_ADDR_ATTR_PORT]));
+
+	return 0;
+}
+
+int mptcp_pm_parse_addr(struct nlattr *attr, struct genl_info *info,
+			struct mptcp_addr_info *addr)
+{
+	struct nlattr *tb[MPTCP_PM_ADDR_ATTR_MAX + 1];
+
+	memset(addr, 0, sizeof(*addr));
+
+	return mptcp_pm_parse_pm_addr_attr(tb, attr, info, addr, true);
+}
+
+int mptcp_pm_parse_entry(struct nlattr *attr, struct genl_info *info,
+			 bool require_family,
+			 struct mptcp_pm_addr_entry *entry)
+{
+	struct nlattr *tb[MPTCP_PM_ADDR_ATTR_MAX + 1];
+	int err;
+
+	memset(entry, 0, sizeof(*entry));
+
+	err = mptcp_pm_parse_pm_addr_attr(tb, attr, info, &entry->addr, require_family);
+	if (err)
+		return err;
+
+	if (tb[MPTCP_PM_ADDR_ATTR_IF_IDX]) {
+		s32 val = nla_get_s32(tb[MPTCP_PM_ADDR_ATTR_IF_IDX]);
+
+		entry->ifindex = val;
+	}
+
+	if (tb[MPTCP_PM_ADDR_ATTR_FLAGS])
+		entry->flags = nla_get_u32(tb[MPTCP_PM_ADDR_ATTR_FLAGS]) &
+			       MPTCP_PM_ADDR_FLAGS_MASK;
+
+	if (tb[MPTCP_PM_ADDR_ATTR_PORT])
+		entry->addr.port = htons(nla_get_u16(tb[MPTCP_PM_ADDR_ATTR_PORT]));
+
+	return 0;
+}
+
+static int mptcp_nl_fill_addr(struct sk_buff *skb,
+			      struct mptcp_pm_addr_entry *entry)
+{
+	struct mptcp_addr_info *addr = &entry->addr;
+	struct nlattr *attr;
+
+	attr = nla_nest_start(skb, MPTCP_PM_ATTR_ADDR);
+	if (!attr)
+		return -EMSGSIZE;
+
+	if (nla_put_u16(skb, MPTCP_PM_ADDR_ATTR_FAMILY, addr->family))
+		goto nla_put_failure;
+	if (nla_put_u16(skb, MPTCP_PM_ADDR_ATTR_PORT, ntohs(addr->port)))
+		goto nla_put_failure;
+	if (nla_put_u8(skb, MPTCP_PM_ADDR_ATTR_ID, addr->id))
+		goto nla_put_failure;
+	if (nla_put_u32(skb, MPTCP_PM_ADDR_ATTR_FLAGS, entry->flags))
+		goto nla_put_failure;
+	if (entry->ifindex &&
+	    nla_put_s32(skb, MPTCP_PM_ADDR_ATTR_IF_IDX, entry->ifindex))
+		goto nla_put_failure;
+
+	if (addr->family == AF_INET &&
+	    nla_put_in_addr(skb, MPTCP_PM_ADDR_ATTR_ADDR4,
+			    addr->addr.s_addr))
+		goto nla_put_failure;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (addr->family == AF_INET6 &&
+		 nla_put_in6_addr(skb, MPTCP_PM_ADDR_ATTR_ADDR6, &addr->addr6))
+		goto nla_put_failure;
+#endif
+	nla_nest_end(skb, attr);
+	return 0;
+
+nla_put_failure:
+	nla_nest_cancel(skb, attr);
+	return -EMSGSIZE;
+}
+
+static int mptcp_pm_get_addr(u8 id, struct mptcp_pm_addr_entry *addr,
+			     struct genl_info *info)
+{
+	if (info->attrs[MPTCP_PM_ATTR_TOKEN])
+		return mptcp_userspace_pm_get_addr(id, addr, info);
+	return mptcp_pm_nl_get_addr(id, addr, info);
+}
+
+int mptcp_pm_nl_get_addr_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct mptcp_pm_addr_entry addr;
+	struct nlattr *attr;
+	struct sk_buff *msg;
+	void *reply;
+	int ret;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ENDPOINT_ADDR))
+		return -EINVAL;
+
+	attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
+	ret = mptcp_pm_parse_entry(attr, info, false, &addr);
+	if (ret < 0)
+		return ret;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	reply = genlmsg_put_reply(msg, info, &mptcp_genl_family, 0,
+				  info->genlhdr->cmd);
+	if (!reply) {
+		GENL_SET_ERR_MSG(info, "not enough space in Netlink message");
+		ret = -EMSGSIZE;
+		goto fail;
+	}
+
+	ret = mptcp_pm_get_addr(addr.addr.id, &addr, info);
+	if (ret) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr, "address not found");
+		goto fail;
+	}
+
+	ret = mptcp_nl_fill_addr(msg, &addr);
+	if (ret)
+		goto fail;
+
+	genlmsg_end(msg, reply);
+	ret = genlmsg_reply(msg, info);
+	return ret;
+
+fail:
+	nlmsg_free(msg);
+	return ret;
+}
+
+int mptcp_pm_genl_fill_addr(struct sk_buff *msg,
+			    struct netlink_callback *cb,
+			    struct mptcp_pm_addr_entry *entry)
+{
+	void *hdr;
+
+	hdr = genlmsg_put(msg, NETLINK_CB(cb->skb).portid,
+			  cb->nlh->nlmsg_seq, &mptcp_genl_family,
+			  NLM_F_MULTI, MPTCP_PM_CMD_GET_ADDR);
+	if (!hdr)
+		return -EINVAL;
+
+	if (mptcp_nl_fill_addr(msg, entry) < 0) {
+		genlmsg_cancel(msg, hdr);
+		return -EINVAL;
+	}
+
+	genlmsg_end(msg, hdr);
+	return 0;
+}
+
+static int mptcp_pm_dump_addr(struct sk_buff *msg, struct netlink_callback *cb)
+{
+	const struct genl_info *info = genl_info_dump(cb);
+
+	if (info->attrs[MPTCP_PM_ATTR_TOKEN])
+		return mptcp_userspace_pm_dump_addr(msg, cb);
+	return mptcp_pm_nl_dump_addr(msg, cb);
+}
+
+int mptcp_pm_nl_get_addr_dumpit(struct sk_buff *msg,
+				struct netlink_callback *cb)
+{
+	return mptcp_pm_dump_addr(msg, cb);
+}
+
+static int mptcp_pm_set_flags(struct genl_info *info)
+{
+	struct mptcp_pm_addr_entry loc = { .addr = { .family = AF_UNSPEC }, };
+	struct nlattr *attr_loc;
+	int ret = -EINVAL;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_ADDR))
+		return ret;
+
+	attr_loc = info->attrs[MPTCP_PM_ATTR_ADDR];
+	ret = mptcp_pm_parse_entry(attr_loc, info, false, &loc);
+	if (ret < 0)
+		return ret;
+
+	if (info->attrs[MPTCP_PM_ATTR_TOKEN])
+		return mptcp_userspace_pm_set_flags(&loc, info);
+	return mptcp_pm_nl_set_flags(&loc, info);
+}
+
+int mptcp_pm_nl_set_flags_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	return mptcp_pm_set_flags(info);
+}
+
+static void mptcp_nl_mcast_send(struct net *net, struct sk_buff *nlskb, gfp_t gfp)
+{
+	genlmsg_multicast_netns(&mptcp_genl_family, net,
+				nlskb, 0, MPTCP_PM_EV_GRP_OFFSET, gfp);
+}
+
+bool mptcp_userspace_pm_active(const struct mptcp_sock *msk)
+{
+	return genl_has_listeners(&mptcp_genl_family,
+				  sock_net((const struct sock *)msk),
+				  MPTCP_PM_EV_GRP_OFFSET);
+}
+
+static int mptcp_event_add_subflow(struct sk_buff *skb, const struct sock *ssk)
+{
+	const struct inet_sock *issk = inet_sk(ssk);
+	const struct mptcp_subflow_context *sf;
+
+	if (nla_put_u16(skb, MPTCP_ATTR_FAMILY, ssk->sk_family))
+		return -EMSGSIZE;
+
+	switch (ssk->sk_family) {
+	case AF_INET:
+		if (nla_put_in_addr(skb, MPTCP_ATTR_SADDR4, issk->inet_saddr))
+			return -EMSGSIZE;
+		if (nla_put_in_addr(skb, MPTCP_ATTR_DADDR4, issk->inet_daddr))
+			return -EMSGSIZE;
+		break;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	case AF_INET6: {
+		if (nla_put_in6_addr(skb, MPTCP_ATTR_SADDR6, &issk->pinet6->saddr))
+			return -EMSGSIZE;
+		if (nla_put_in6_addr(skb, MPTCP_ATTR_DADDR6, &ssk->sk_v6_daddr))
+			return -EMSGSIZE;
+		break;
+	}
+#endif
+	default:
+		WARN_ON_ONCE(1);
+		return -EMSGSIZE;
+	}
+
+	if (nla_put_be16(skb, MPTCP_ATTR_SPORT, issk->inet_sport))
+		return -EMSGSIZE;
+	if (nla_put_be16(skb, MPTCP_ATTR_DPORT, issk->inet_dport))
+		return -EMSGSIZE;
+
+	sf = mptcp_subflow_ctx(ssk);
+	if (WARN_ON_ONCE(!sf))
+		return -EINVAL;
+
+	if (nla_put_u8(skb, MPTCP_ATTR_LOC_ID, subflow_get_local_id(sf)))
+		return -EMSGSIZE;
+
+	if (nla_put_u8(skb, MPTCP_ATTR_REM_ID, sf->remote_id))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+static int mptcp_event_put_token_and_ssk(struct sk_buff *skb,
+					 const struct mptcp_sock *msk,
+					 const struct sock *ssk)
+{
+	const struct sock *sk = (const struct sock *)msk;
+	const struct mptcp_subflow_context *sf;
+	u8 sk_err;
+
+	if (nla_put_u32(skb, MPTCP_ATTR_TOKEN, READ_ONCE(msk->token)))
+		return -EMSGSIZE;
+
+	if (mptcp_event_add_subflow(skb, ssk))
+		return -EMSGSIZE;
+
+	sf = mptcp_subflow_ctx(ssk);
+	if (WARN_ON_ONCE(!sf))
+		return -EINVAL;
+
+	if (nla_put_u8(skb, MPTCP_ATTR_BACKUP, sf->backup))
+		return -EMSGSIZE;
+
+	if (ssk->sk_bound_dev_if &&
+	    nla_put_s32(skb, MPTCP_ATTR_IF_IDX, ssk->sk_bound_dev_if))
+		return -EMSGSIZE;
+
+	sk_err = READ_ONCE(ssk->sk_err);
+	if (sk_err && sk->sk_state == TCP_ESTABLISHED &&
+	    nla_put_u8(skb, MPTCP_ATTR_ERROR, sk_err))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+static int mptcp_event_sub_established(struct sk_buff *skb,
+				       const struct mptcp_sock *msk,
+				       const struct sock *ssk)
+{
+	return mptcp_event_put_token_and_ssk(skb, msk, ssk);
+}
+
+static int mptcp_event_sub_closed(struct sk_buff *skb,
+				  const struct mptcp_sock *msk,
+				  const struct sock *ssk)
+{
+	const struct mptcp_subflow_context *sf;
+
+	if (mptcp_event_put_token_and_ssk(skb, msk, ssk))
+		return -EMSGSIZE;
+
+	sf = mptcp_subflow_ctx(ssk);
+	if (!sf->reset_seen)
+		return 0;
+
+	if (nla_put_u32(skb, MPTCP_ATTR_RESET_REASON, sf->reset_reason))
+		return -EMSGSIZE;
+
+	if (nla_put_u32(skb, MPTCP_ATTR_RESET_FLAGS, sf->reset_transient))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+static int mptcp_event_created(struct sk_buff *skb,
+			       const struct mptcp_sock *msk,
+			       const struct sock *ssk)
+{
+	int err = nla_put_u32(skb, MPTCP_ATTR_TOKEN, READ_ONCE(msk->token));
+	u16 flags = 0;
+
+	if (err)
+		return err;
+
+	if (READ_ONCE(msk->pm.server_side)) {
+		flags |= MPTCP_PM_EV_FLAG_SERVER_SIDE;
+
+		/* Deprecated, and only set when it is the server side */
+		if (nla_put_u8(skb, MPTCP_ATTR_SERVER_SIDE, 1))
+			return -EMSGSIZE;
+	}
+
+	if (READ_ONCE(msk->pm.remote_deny_join_id0))
+		flags |= MPTCP_PM_EV_FLAG_DENY_JOIN_ID0;
+
+	if (flags && nla_put_u16(skb, MPTCP_ATTR_FLAGS, flags))
+		return -EMSGSIZE;
+
+	return mptcp_event_add_subflow(skb, ssk);
+}
+
+void mptcp_event_addr_removed(const struct mptcp_sock *msk, uint8_t id)
+{
+	struct net *net = sock_net((const struct sock *)msk);
+	struct nlmsghdr *nlh;
+	struct sk_buff *skb;
+
+	if (!genl_has_listeners(&mptcp_genl_family, net, MPTCP_PM_EV_GRP_OFFSET))
+		return;
+
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
+	if (!skb)
+		return;
+
+	nlh = genlmsg_put(skb, 0, 0, &mptcp_genl_family, 0, MPTCP_EVENT_REMOVED);
+	if (!nlh)
+		goto nla_put_failure;
+
+	if (nla_put_u32(skb, MPTCP_ATTR_TOKEN, READ_ONCE(msk->token)))
+		goto nla_put_failure;
+
+	if (nla_put_u8(skb, MPTCP_ATTR_REM_ID, id))
+		goto nla_put_failure;
+
+	genlmsg_end(skb, nlh);
+	mptcp_nl_mcast_send(net, skb, GFP_ATOMIC);
+	return;
+
+nla_put_failure:
+	nlmsg_free(skb);
+}
+
+void mptcp_event_addr_announced(const struct sock *ssk,
+				const struct mptcp_addr_info *info)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct net *net = sock_net(ssk);
+	struct nlmsghdr *nlh;
+	struct sk_buff *skb;
+
+	if (!genl_has_listeners(&mptcp_genl_family, net, MPTCP_PM_EV_GRP_OFFSET))
+		return;
+
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
+	if (!skb)
+		return;
+
+	nlh = genlmsg_put(skb, 0, 0, &mptcp_genl_family, 0,
+			  MPTCP_EVENT_ANNOUNCED);
+	if (!nlh)
+		goto nla_put_failure;
+
+	if (nla_put_u32(skb, MPTCP_ATTR_TOKEN, READ_ONCE(msk->token)))
+		goto nla_put_failure;
+
+	if (nla_put_u8(skb, MPTCP_ATTR_REM_ID, info->id))
+		goto nla_put_failure;
+
+	if (nla_put_be16(skb, MPTCP_ATTR_DPORT,
+			 info->port == 0 ?
+			 inet_sk(ssk)->inet_dport :
+			 info->port))
+		goto nla_put_failure;
+
+	switch (info->family) {
+	case AF_INET:
+		if (nla_put_in_addr(skb, MPTCP_ATTR_DADDR4, info->addr.s_addr))
+			goto nla_put_failure;
+		break;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	case AF_INET6:
+		if (nla_put_in6_addr(skb, MPTCP_ATTR_DADDR6, &info->addr6))
+			goto nla_put_failure;
+		break;
+#endif
+	default:
+		WARN_ON_ONCE(1);
+		goto nla_put_failure;
+	}
+
+	genlmsg_end(skb, nlh);
+	mptcp_nl_mcast_send(net, skb, GFP_ATOMIC);
+	return;
+
+nla_put_failure:
+	nlmsg_free(skb);
+}
+
+void mptcp_event_pm_listener(const struct sock *ssk,
+			     enum mptcp_event_type event)
+{
+	const struct inet_sock *issk = inet_sk(ssk);
+	struct net *net = sock_net(ssk);
+	struct nlmsghdr *nlh;
+	struct sk_buff *skb;
+
+	if (!genl_has_listeners(&mptcp_genl_family, net, MPTCP_PM_EV_GRP_OFFSET))
+		return;
+
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!skb)
+		return;
+
+	nlh = genlmsg_put(skb, 0, 0, &mptcp_genl_family, 0, event);
+	if (!nlh)
+		goto nla_put_failure;
+
+	if (nla_put_u16(skb, MPTCP_ATTR_FAMILY, ssk->sk_family))
+		goto nla_put_failure;
+
+	if (nla_put_be16(skb, MPTCP_ATTR_SPORT, issk->inet_sport))
+		goto nla_put_failure;
+
+	switch (ssk->sk_family) {
+	case AF_INET:
+		if (nla_put_in_addr(skb, MPTCP_ATTR_SADDR4, issk->inet_saddr))
+			goto nla_put_failure;
+		break;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	case AF_INET6: {
+		if (nla_put_in6_addr(skb, MPTCP_ATTR_SADDR6, &issk->pinet6->saddr))
+			goto nla_put_failure;
+		break;
+	}
+#endif
+	default:
+		WARN_ON_ONCE(1);
+		goto nla_put_failure;
+	}
+
+	genlmsg_end(skb, nlh);
+	mptcp_nl_mcast_send(net, skb, GFP_KERNEL);
+	return;
+
+nla_put_failure:
+	nlmsg_free(skb);
+}
+
+void mptcp_event(enum mptcp_event_type type, const struct mptcp_sock *msk,
+		 const struct sock *ssk, gfp_t gfp)
+{
+	struct net *net = sock_net((const struct sock *)msk);
+	struct nlmsghdr *nlh;
+	struct sk_buff *skb;
+
+	if (!genl_has_listeners(&mptcp_genl_family, net, MPTCP_PM_EV_GRP_OFFSET))
+		return;
+
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, gfp);
+	if (!skb)
+		return;
+
+	nlh = genlmsg_put(skb, 0, 0, &mptcp_genl_family, 0, type);
+	if (!nlh)
+		goto nla_put_failure;
+
+	switch (type) {
+	case MPTCP_EVENT_UNSPEC:
+		WARN_ON_ONCE(1);
+		break;
+	case MPTCP_EVENT_CREATED:
+	case MPTCP_EVENT_ESTABLISHED:
+		if (mptcp_event_created(skb, msk, ssk) < 0)
+			goto nla_put_failure;
+		break;
+	case MPTCP_EVENT_CLOSED:
+		if (nla_put_u32(skb, MPTCP_ATTR_TOKEN, READ_ONCE(msk->token)) < 0)
+			goto nla_put_failure;
+		break;
+	case MPTCP_EVENT_ANNOUNCED:
+	case MPTCP_EVENT_REMOVED:
+		/* call mptcp_event_addr_announced()/removed instead */
+		WARN_ON_ONCE(1);
+		break;
+	case MPTCP_EVENT_SUB_ESTABLISHED:
+	case MPTCP_EVENT_SUB_PRIORITY:
+		if (mptcp_event_sub_established(skb, msk, ssk) < 0)
+			goto nla_put_failure;
+		break;
+	case MPTCP_EVENT_SUB_CLOSED:
+		if (mptcp_event_sub_closed(skb, msk, ssk) < 0)
+			goto nla_put_failure;
+		break;
+	case MPTCP_EVENT_LISTENER_CREATED:
+	case MPTCP_EVENT_LISTENER_CLOSED:
+		break;
+	}
+
+	genlmsg_end(skb, nlh);
+	mptcp_nl_mcast_send(net, skb, gfp);
+	return;
+
+nla_put_failure:
+	nlmsg_free(skb);
+}
+
+struct genl_family mptcp_genl_family __ro_after_init = {
+	.name		= MPTCP_PM_NAME,
+	.version	= MPTCP_PM_VER,
+	.netnsok	= true,
+	.module		= THIS_MODULE,
+	.ops		= mptcp_pm_nl_ops,
+	.n_ops		= ARRAY_SIZE(mptcp_pm_nl_ops),
+	.resv_start_op	= MPTCP_PM_CMD_SUBFLOW_DESTROY + 1,
+	.mcgrps		= mptcp_pm_mcgrps,
+	.n_mcgrps	= ARRAY_SIZE(mptcp_pm_mcgrps),
+};
+
+void __init mptcp_pm_nl_init(void)
+{
+	if (genl_register_family(&mptcp_genl_family))
+		panic("Failed to register MPTCP PM netlink family\n");
+}
diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
new file mode 100644
index 000000000..fab16d953
--- /dev/null
+++ b/net/mptcp/pm_userspace.c
@@ -0,0 +1,718 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2022, Intel Corporation.
+ */
+
+#include "protocol.h"
+#include "mib.h"
+#include "mptcp_pm_gen.h"
+
+#define mptcp_for_each_userspace_pm_addr(__msk, __entry)			\
+	list_for_each_entry(__entry,						\
+			    &((__msk)->pm.userspace_pm_local_addr_list), list)
+
+void mptcp_userspace_pm_free_local_addr_list(struct mptcp_sock *msk)
+{
+	struct mptcp_pm_addr_entry *entry, *tmp;
+	struct sock *sk = (struct sock *)msk;
+	LIST_HEAD(free_list);
+
+	spin_lock_bh(&msk->pm.lock);
+	list_splice_init(&msk->pm.userspace_pm_local_addr_list, &free_list);
+	spin_unlock_bh(&msk->pm.lock);
+
+	list_for_each_entry_safe(entry, tmp, &free_list, list) {
+		sock_kfree_s(sk, entry, sizeof(*entry));
+	}
+}
+
+static struct mptcp_pm_addr_entry *
+mptcp_userspace_pm_lookup_addr(struct mptcp_sock *msk,
+			       const struct mptcp_addr_info *addr)
+{
+	struct mptcp_pm_addr_entry *entry;
+
+	mptcp_for_each_userspace_pm_addr(msk, entry) {
+		if (mptcp_addresses_equal(&entry->addr, addr, false))
+			return entry;
+	}
+	return NULL;
+}
+
+static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
+						    struct mptcp_pm_addr_entry *entry,
+						    bool needs_id)
+{
+	DECLARE_BITMAP(id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_addr_entry *e;
+	bool addr_match = false;
+	bool id_match = false;
+	int ret = -EINVAL;
+
+	bitmap_zero(id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
+
+	spin_lock_bh(&msk->pm.lock);
+	if (msk->pm.status & BIT(MPTCP_PM_DESTROYING)) {
+		ret = -EINVAL;
+		goto append_err;
+	}
+	mptcp_for_each_userspace_pm_addr(msk, e) {
+		addr_match = mptcp_addresses_equal(&e->addr, &entry->addr, true);
+		if (addr_match && entry->addr.id == 0 && needs_id)
+			entry->addr.id = e->addr.id;
+		id_match = (e->addr.id == entry->addr.id);
+		if (addr_match || id_match)
+			break;
+		__set_bit(e->addr.id, id_bitmap);
+	}
+
+	if (!addr_match && !id_match) {
+		unsigned int id;
+
+		if (!entry->addr.id && needs_id) {
+			id = find_next_zero_bit(id_bitmap,
+						MPTCP_PM_MAX_ADDR_ID + 1, 1);
+			if (id > MPTCP_PM_MAX_ADDR_ID) {
+				ret = -ENOSPC;
+				goto append_err;
+			}
+		} else {
+			id = entry->addr.id;
+		}
+
+		/* Memory for the entry is allocated from the
+		 * sock option buffer.
+		 */
+		e = sock_kmemdup(sk, entry, sizeof(*entry), GFP_ATOMIC);
+		if (!e) {
+			ret = -ENOMEM;
+			goto append_err;
+		}
+
+		e->addr.id = id;
+		list_add_tail_rcu(&e->list, &msk->pm.userspace_pm_local_addr_list);
+		msk->pm.local_addr_used++;
+		ret = e->addr.id;
+	} else if (addr_match && id_match) {
+		ret = entry->addr.id;
+	}
+
+append_err:
+	spin_unlock_bh(&msk->pm.lock);
+	return ret;
+}
+
+/* If the subflow is closed from the other peer (not via a
+ * subflow destroy command then), we want to keep the entry
+ * not to assign the same ID to another address and to be
+ * able to send RM_ADDR after the removal of the subflow.
+ */
+static int mptcp_userspace_pm_delete_local_addr(struct mptcp_sock *msk,
+						struct mptcp_pm_addr_entry *addr)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_addr_entry *entry;
+
+	entry = mptcp_userspace_pm_lookup_addr(msk, &addr->addr);
+	if (!entry)
+		return -EINVAL;
+
+	/* TODO: a refcount is needed because the entry can
+	 * be used multiple times (e.g. fullmesh mode).
+	 */
+	list_del_rcu(&entry->list);
+	sock_kfree_s(sk, entry, sizeof(*entry));
+	msk->pm.local_addr_used--;
+	return 0;
+}
+
+static struct mptcp_pm_addr_entry *
+mptcp_userspace_pm_lookup_addr_by_id(struct mptcp_sock *msk, unsigned int id)
+{
+	struct mptcp_pm_addr_entry *entry;
+
+	mptcp_for_each_userspace_pm_addr(msk, entry) {
+		if (entry->addr.id == id)
+			return entry;
+	}
+	return NULL;
+}
+
+int mptcp_userspace_pm_get_local_id(struct mptcp_sock *msk,
+				    struct mptcp_pm_addr_entry *skc)
+{
+	__be16 msk_sport =  ((struct inet_sock *)
+			     inet_sk((struct sock *)msk))->inet_sport;
+	struct mptcp_pm_addr_entry *entry;
+	int id;
+
+	spin_lock_bh(&msk->pm.lock);
+	entry = mptcp_userspace_pm_lookup_addr(msk, &skc->addr);
+	id = entry ? entry->addr.id : -1;
+	spin_unlock_bh(&msk->pm.lock);
+
+	if (id != -1)
+		return id;
+
+	if (skc->addr.port == msk_sport)
+		skc->addr.port = 0;
+
+	return mptcp_userspace_pm_append_new_local_addr(msk, skc, true);
+}
+
+bool mptcp_userspace_pm_is_backup(struct mptcp_sock *msk,
+				  struct mptcp_addr_info *skc)
+{
+	struct mptcp_pm_addr_entry *entry;
+	bool backup;
+
+	spin_lock_bh(&msk->pm.lock);
+	entry = mptcp_userspace_pm_lookup_addr(msk, skc);
+	backup = entry && !!(entry->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
+	spin_unlock_bh(&msk->pm.lock);
+
+	return backup;
+}
+
+static struct mptcp_sock *mptcp_userspace_pm_get_sock(const struct genl_info *info)
+{
+	struct mptcp_sock *msk;
+	struct nlattr *token;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_TOKEN))
+		return NULL;
+
+	token = info->attrs[MPTCP_PM_ATTR_TOKEN];
+	msk = mptcp_token_get_sock(genl_info_net(info), nla_get_u32(token));
+	if (!msk) {
+		NL_SET_ERR_MSG_ATTR(info->extack, token, "invalid token");
+		return NULL;
+	}
+
+	if (!mptcp_pm_is_userspace(msk)) {
+		NL_SET_ERR_MSG_ATTR(info->extack, token,
+				    "userspace PM not selected");
+		sock_put((struct sock *)msk);
+		return NULL;
+	}
+
+	return msk;
+}
+
+int mptcp_pm_nl_announce_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct mptcp_pm_addr_entry addr_val;
+	struct mptcp_sock *msk;
+	struct nlattr *addr;
+	int err = -EINVAL;
+	struct sock *sk;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_ADDR))
+		return err;
+
+	msk = mptcp_userspace_pm_get_sock(info);
+	if (!msk)
+		return err;
+
+	sk = (struct sock *)msk;
+
+	addr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	err = mptcp_pm_parse_entry(addr, info, true, &addr_val);
+	if (err < 0)
+		goto announce_err;
+
+	if (addr_val.addr.id == 0) {
+		NL_SET_ERR_MSG_ATTR(info->extack, addr, "invalid addr id");
+		err = -EINVAL;
+		goto announce_err;
+	}
+
+	if (!(addr_val.flags & MPTCP_PM_ADDR_FLAG_SIGNAL)) {
+		NL_SET_ERR_MSG_ATTR(info->extack, addr, "invalid addr flags");
+		err = -EINVAL;
+		goto announce_err;
+	}
+
+	err = mptcp_userspace_pm_append_new_local_addr(msk, &addr_val, false);
+	if (err < 0) {
+		NL_SET_ERR_MSG_ATTR(info->extack, addr,
+				    "did not match address and id");
+		goto announce_err;
+	}
+
+	lock_sock(sk);
+	spin_lock_bh(&msk->pm.lock);
+
+	if (mptcp_pm_announced_alloc(msk, &addr_val.addr)) {
+		msk->pm.add_addr_signaled++;
+		mptcp_pm_announce_addr(msk, &addr_val.addr, false);
+		mptcp_pm_addr_send_ack(msk);
+	}
+
+	spin_unlock_bh(&msk->pm.lock);
+	release_sock(sk);
+
+	err = 0;
+ announce_err:
+	sock_put(sk);
+	return err;
+}
+
+static int mptcp_userspace_pm_remove_id_zero_address(struct mptcp_sock *msk)
+{
+	struct mptcp_rm_list list = { .nr = 0 };
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	bool has_id_0 = false;
+	int err = -EINVAL;
+
+	lock_sock(sk);
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->local_id) == 0) {
+			has_id_0 = true;
+			break;
+		}
+	}
+	if (!has_id_0)
+		goto remove_err;
+
+	list.ids[list.nr++] = 0;
+
+	spin_lock_bh(&msk->pm.lock);
+	mptcp_pm_remove_addr(msk, &list);
+	spin_unlock_bh(&msk->pm.lock);
+
+	err = 0;
+
+remove_err:
+	release_sock(sk);
+	return err;
+}
+
+static void
+mptcp_userspace_pm_remove_addr_entry(struct mptcp_sock *msk,
+				     struct mptcp_pm_addr_entry *entry)
+{
+	struct mptcp_rm_list alist = { .nr = 0 };
+	int anno_nr = 0;
+
+	/* only delete if either announced or matching a subflow */
+	if (mptcp_pm_announced_remove(msk, &entry->addr))
+		anno_nr++;
+	else if (!mptcp_pm_has_subflow_saddr(msk, &entry->addr))
+		return;
+
+	alist.ids[alist.nr++] = entry->addr.id;
+
+	spin_lock_bh(&msk->pm.lock);
+	msk->pm.add_addr_signaled -= anno_nr;
+	mptcp_pm_remove_addr(msk, &alist);
+	spin_unlock_bh(&msk->pm.lock);
+}
+
+int mptcp_pm_nl_remove_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct mptcp_pm_addr_entry *match;
+	struct mptcp_sock *msk;
+	struct nlattr *id;
+	int err = -EINVAL;
+	struct sock *sk;
+	u8 id_val;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_LOC_ID))
+		return err;
+
+	id = info->attrs[MPTCP_PM_ATTR_LOC_ID];
+	id_val = nla_get_u8(id);
+
+	msk = mptcp_userspace_pm_get_sock(info);
+	if (!msk)
+		return err;
+
+	sk = (struct sock *)msk;
+
+	if (id_val == 0) {
+		err = mptcp_userspace_pm_remove_id_zero_address(msk);
+		goto out;
+	}
+
+	lock_sock(sk);
+
+	spin_lock_bh(&msk->pm.lock);
+	match = mptcp_userspace_pm_lookup_addr_by_id(msk, id_val);
+	if (!match) {
+		spin_unlock_bh(&msk->pm.lock);
+		release_sock(sk);
+		goto out;
+	}
+
+	list_del_rcu(&match->list);
+	spin_unlock_bh(&msk->pm.lock);
+
+	mptcp_userspace_pm_remove_addr_entry(msk, match);
+
+	release_sock(sk);
+
+	kfree_rcu_mightsleep(match);
+	/* Adjust sk_omem_alloc like sock_kfree_s() does, to match
+	 * with allocation of this memory by sock_kmemdup()
+	 */
+	atomic_sub(sizeof(*match), &sk->sk_omem_alloc);
+
+	err = 0;
+out:
+	if (err)
+		NL_SET_ERR_MSG_ATTR_FMT(info->extack, id,
+					"address with id %u not found",
+					id_val);
+
+	sock_put(sk);
+	return err;
+}
+
+int mptcp_pm_nl_subflow_create_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct mptcp_pm_addr_entry entry = { 0 };
+	struct mptcp_addr_info addr_r;
+	struct nlattr *raddr, *laddr;
+	struct mptcp_pm_local local;
+	struct mptcp_sock *msk;
+	int err = -EINVAL;
+	struct sock *sk;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_ADDR) ||
+	    GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_ADDR_REMOTE))
+		return err;
+
+	msk = mptcp_userspace_pm_get_sock(info);
+	if (!msk)
+		return err;
+
+	sk = (struct sock *)msk;
+
+	laddr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	err = mptcp_pm_parse_entry(laddr, info, true, &entry);
+	if (err < 0)
+		goto create_err;
+
+	if (entry.flags & MPTCP_PM_ADDR_FLAG_SIGNAL) {
+		NL_SET_ERR_MSG_ATTR(info->extack, laddr, "invalid addr flags");
+		err = -EINVAL;
+		goto create_err;
+	}
+	entry.flags |= MPTCP_PM_ADDR_FLAG_SUBFLOW;
+
+	raddr = info->attrs[MPTCP_PM_ATTR_ADDR_REMOTE];
+	err = mptcp_pm_parse_addr(raddr, info, &addr_r);
+	if (err < 0)
+		goto create_err;
+
+	if (!mptcp_pm_addr_families_match(sk, &entry.addr, &addr_r)) {
+		GENL_SET_ERR_MSG(info, "families mismatch");
+		err = -EINVAL;
+		goto create_err;
+	}
+
+	err = mptcp_userspace_pm_append_new_local_addr(msk, &entry, false);
+	if (err < 0) {
+		NL_SET_ERR_MSG_ATTR(info->extack, laddr,
+				    "did not match address and id");
+		goto create_err;
+	}
+
+	local.addr = entry.addr;
+	local.flags = entry.flags;
+	local.ifindex = entry.ifindex;
+
+	spin_lock_bh(&msk->pm.lock);
+	msk->pm.extra_subflows++;
+	spin_unlock_bh(&msk->pm.lock);
+
+	lock_sock(sk);
+	err = __mptcp_subflow_connect(sk, &local, &addr_r);
+	release_sock(sk);
+
+	if (err) {
+		GENL_SET_ERR_MSG_FMT(info, "connect error: %d", err);
+
+		spin_lock_bh(&msk->pm.lock);
+		mptcp_userspace_pm_delete_local_addr(msk, &entry);
+		spin_unlock_bh(&msk->pm.lock);
+	}
+
+ create_err:
+	sock_put(sk);
+	return err;
+}
+
+static struct sock *mptcp_nl_find_ssk(struct mptcp_sock *msk,
+				      const struct mptcp_addr_info *local,
+				      const struct mptcp_addr_info *remote)
+{
+	struct mptcp_subflow_context *subflow;
+
+	if (local->family != remote->family)
+		return NULL;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		const struct inet_sock *issk;
+		struct sock *ssk;
+
+		ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (local->family != ssk->sk_family)
+			continue;
+
+		issk = inet_sk(ssk);
+
+		switch (ssk->sk_family) {
+		case AF_INET:
+			if (issk->inet_saddr != local->addr.s_addr ||
+			    issk->inet_daddr != remote->addr.s_addr)
+				continue;
+			break;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+		case AF_INET6: {
+			if (!ipv6_addr_equal(&local->addr6, &issk->pinet6->saddr) ||
+			    !ipv6_addr_equal(&remote->addr6, &ssk->sk_v6_daddr))
+				continue;
+			break;
+		}
+#endif
+		default:
+			continue;
+		}
+
+		if (issk->inet_sport == local->port &&
+		    issk->inet_dport == remote->port)
+			return ssk;
+	}
+
+	return NULL;
+}
+
+int mptcp_pm_nl_subflow_destroy_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct mptcp_pm_addr_entry addr_l;
+	struct mptcp_addr_info addr_r;
+	struct nlattr *raddr, *laddr;
+	struct mptcp_sock *msk;
+	struct sock *sk, *ssk;
+	int err = -EINVAL;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_ADDR) ||
+	    GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_ADDR_REMOTE))
+		return err;
+
+	msk = mptcp_userspace_pm_get_sock(info);
+	if (!msk)
+		return err;
+
+	sk = (struct sock *)msk;
+
+	laddr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	err = mptcp_pm_parse_entry(laddr, info, true, &addr_l);
+	if (err < 0)
+		goto destroy_err;
+
+	raddr = info->attrs[MPTCP_PM_ATTR_ADDR_REMOTE];
+	err = mptcp_pm_parse_addr(raddr, info, &addr_r);
+	if (err < 0)
+		goto destroy_err;
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (addr_l.addr.family == AF_INET && ipv6_addr_v4mapped(&addr_r.addr6)) {
+		ipv6_addr_set_v4mapped(addr_l.addr.addr.s_addr, &addr_l.addr.addr6);
+		addr_l.addr.family = AF_INET6;
+	}
+	if (addr_r.family == AF_INET && ipv6_addr_v4mapped(&addr_l.addr.addr6)) {
+		ipv6_addr_set_v4mapped(addr_r.addr.s_addr, &addr_r.addr6);
+		addr_r.family = AF_INET6;
+	}
+#endif
+	if (addr_l.addr.family != addr_r.family) {
+		GENL_SET_ERR_MSG(info, "address families do not match");
+		err = -EINVAL;
+		goto destroy_err;
+	}
+
+	if (!addr_l.addr.port) {
+		NL_SET_ERR_MSG_ATTR(info->extack, laddr, "missing local port");
+		err = -EINVAL;
+		goto destroy_err;
+	}
+
+	if (!addr_r.port) {
+		NL_SET_ERR_MSG_ATTR(info->extack, raddr, "missing remote port");
+		err = -EINVAL;
+		goto destroy_err;
+	}
+
+	lock_sock(sk);
+	ssk = mptcp_nl_find_ssk(msk, &addr_l.addr, &addr_r);
+	if (!ssk) {
+		GENL_SET_ERR_MSG(info, "subflow not found");
+		err = -ESRCH;
+		goto release_sock;
+	}
+
+	spin_lock_bh(&msk->pm.lock);
+	mptcp_userspace_pm_delete_local_addr(msk, &addr_l);
+	spin_unlock_bh(&msk->pm.lock);
+	mptcp_subflow_shutdown(sk, ssk, RCV_SHUTDOWN | SEND_SHUTDOWN);
+	mptcp_close_ssk(sk, ssk, mptcp_subflow_ctx(ssk));
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RMSUBFLOW);
+release_sock:
+	release_sock(sk);
+
+destroy_err:
+	sock_put(sk);
+	return err;
+}
+
+int mptcp_userspace_pm_set_flags(struct mptcp_pm_addr_entry *local,
+				 struct genl_info *info)
+{
+	struct mptcp_addr_info rem = { .family = AF_UNSPEC, };
+	struct mptcp_pm_addr_entry *entry;
+	struct nlattr *attr, *attr_rem;
+	struct mptcp_sock *msk;
+	int ret = -EINVAL;
+	struct sock *sk;
+	u8 bkup = 0;
+
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ATTR_ADDR_REMOTE))
+		return ret;
+
+	msk = mptcp_userspace_pm_get_sock(info);
+	if (!msk)
+		return ret;
+
+	sk = (struct sock *)msk;
+
+	attr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	if (local->addr.family == AF_UNSPEC) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "invalid local address family");
+		ret = -EINVAL;
+		goto set_flags_err;
+	}
+
+	attr_rem = info->attrs[MPTCP_PM_ATTR_ADDR_REMOTE];
+	ret = mptcp_pm_parse_addr(attr_rem, info, &rem);
+	if (ret < 0)
+		goto set_flags_err;
+
+	if (rem.family == AF_UNSPEC) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr_rem,
+				    "invalid remote address family");
+		ret = -EINVAL;
+		goto set_flags_err;
+	}
+
+	if (local->flags & MPTCP_PM_ADDR_FLAG_BACKUP)
+		bkup = 1;
+
+	spin_lock_bh(&msk->pm.lock);
+	entry = mptcp_userspace_pm_lookup_addr(msk, &local->addr);
+	if (entry) {
+		if (bkup)
+			entry->flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
+		else
+			entry->flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
+	}
+	spin_unlock_bh(&msk->pm.lock);
+
+	lock_sock(sk);
+	ret = mptcp_pm_mp_prio_send_ack(msk, &local->addr, &rem, bkup);
+	release_sock(sk);
+
+	/* mptcp_pm_mp_prio_send_ack() only fails in one case */
+	if (ret < 0)
+		GENL_SET_ERR_MSG(info, "subflow not found");
+
+set_flags_err:
+	sock_put(sk);
+	return ret;
+}
+
+int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
+				 struct netlink_callback *cb)
+{
+	struct id_bitmap {
+		DECLARE_BITMAP(map, MPTCP_PM_MAX_ADDR_ID + 1);
+	} *bitmap;
+	const struct genl_info *info = genl_info_dump(cb);
+	struct mptcp_pm_addr_entry *entry;
+	struct mptcp_sock *msk;
+	int ret = -EINVAL;
+	struct sock *sk;
+
+	BUILD_BUG_ON(sizeof(struct id_bitmap) > sizeof(cb->ctx));
+
+	bitmap = (struct id_bitmap *)cb->ctx;
+
+	msk = mptcp_userspace_pm_get_sock(info);
+	if (!msk)
+		return ret;
+
+	sk = (struct sock *)msk;
+
+	lock_sock(sk);
+	spin_lock_bh(&msk->pm.lock);
+	mptcp_for_each_userspace_pm_addr(msk, entry) {
+		if (test_bit(entry->addr.id, bitmap->map))
+			continue;
+
+		if (mptcp_pm_genl_fill_addr(msg, cb, entry) < 0)
+			break;
+
+		__set_bit(entry->addr.id, bitmap->map);
+	}
+	spin_unlock_bh(&msk->pm.lock);
+	release_sock(sk);
+	ret = msg->len;
+
+	sock_put(sk);
+	return ret;
+}
+
+int mptcp_userspace_pm_get_addr(u8 id, struct mptcp_pm_addr_entry *addr,
+				struct genl_info *info)
+{
+	struct mptcp_pm_addr_entry *entry;
+	struct mptcp_sock *msk;
+	int ret = -EINVAL;
+	struct sock *sk;
+
+	msk = mptcp_userspace_pm_get_sock(info);
+	if (!msk)
+		return ret;
+
+	sk = (struct sock *)msk;
+
+	lock_sock(sk);
+	spin_lock_bh(&msk->pm.lock);
+	entry = mptcp_userspace_pm_lookup_addr_by_id(msk, id);
+	if (entry) {
+		*addr = *entry;
+		ret = 0;
+	}
+	spin_unlock_bh(&msk->pm.lock);
+	release_sock(sk);
+
+	sock_put(sk);
+	return ret;
+}
+
+static struct mptcp_pm_ops mptcp_pm_userspace = {
+	.name			= "userspace",
+	.owner			= THIS_MODULE,
+};
+
+void __init mptcp_pm_userspace_register(void)
+{
+	mptcp_pm_register(&mptcp_pm_userspace);
+}
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
new file mode 100644
index 000000000..0098e2830
--- /dev/null
+++ b/net/mptcp/protocol.c
@@ -0,0 +1,4892 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/sched/signal.h>
+#include <linux/atomic.h>
+#include <net/aligned_data.h>
+#include <net/rps.h>
+#include <net/sock.h>
+#include <net/inet_common.h>
+#include <net/inet_hashtables.h>
+#include <net/protocol.h>
+#include <net/tcp_states.h>
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+#include <net/transp_v6.h>
+#endif
+#include <net/mptcp.h>
+#include <net/hotdata.h>
+#include <net/xfrm.h>
+#include <asm/ioctls.h>
+#include "protocol.h"
+#include "mib.h"
+
+static unsigned int mptcp_inq_hint(const struct sock *sk);
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/mptcp.h>
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+struct mptcp6_sock {
+	struct mptcp_sock msk;
+	struct ipv6_pinfo np;
+};
+#endif
+
+enum {
+	MPTCP_CMSG_TS = BIT(0),
+	MPTCP_CMSG_INQ = BIT(1),
+};
+
+static struct percpu_counter mptcp_sockets_allocated ____cacheline_aligned_in_smp;
+
+static void __mptcp_destroy_sock(struct sock *sk);
+static void mptcp_check_send_data_fin(struct sock *sk);
+
+DEFINE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions) = {
+	.bh_lock = INIT_LOCAL_LOCK(bh_lock),
+};
+static struct net_device *mptcp_napi_dev;
+
+/* Returns end sequence number of the receiver's advertised window */
+static u64 mptcp_wnd_end(const struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->wnd_end);
+}
+
+static const struct proto_ops *mptcp_fallback_tcp_ops(const struct sock *sk)
+{
+	unsigned short family = READ_ONCE(sk->sk_family);
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (family == AF_INET6)
+		return &inet6_stream_ops;
+#endif
+	WARN_ON_ONCE(family != AF_INET);
+	return &inet_stream_ops;
+}
+
+bool __mptcp_try_fallback(struct mptcp_sock *msk, int fb_mib)
+{
+	struct net *net = sock_net((struct sock *)msk);
+
+	if (__mptcp_check_fallback(msk))
+		return true;
+
+	/* The caller possibly is not holding the msk socket lock, but
+	 * in the fallback case only the current subflow is touching
+	 * the OoO queue.
+	 */
+	if (!RB_EMPTY_ROOT(&msk->out_of_order_queue))
+		return false;
+
+	spin_lock_bh(&msk->fallback_lock);
+	if (!msk->allow_infinite_fallback) {
+		spin_unlock_bh(&msk->fallback_lock);
+		return false;
+	}
+
+	msk->allow_subflows = false;
+	set_bit(MPTCP_FALLBACK_DONE, &msk->flags);
+	clear_bit(MPTCP_RTX_ENABLED, &msk->flags);
+	__MPTCP_INC_STATS(net, fb_mib);
+	spin_unlock_bh(&msk->fallback_lock);
+	return true;
+}
+
+static int __mptcp_socket_create(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	struct socket *ssock;
+	int err;
+
+	err = mptcp_subflow_create_socket(sk, sk->sk_family, &ssock);
+	if (err)
+		return err;
+
+	msk->scaling_ratio = tcp_sk(ssock->sk)->scaling_ratio;
+	WRITE_ONCE(msk->first, ssock->sk);
+	subflow = mptcp_subflow_ctx(ssock->sk);
+	list_add(&subflow->node, &msk->conn_list);
+	sock_hold(ssock->sk);
+	subflow->request_mptcp = 1;
+	subflow->subflow_id = msk->subflow_id++;
+
+	/* This is the first subflow, always with id 0 */
+	WRITE_ONCE(subflow->local_id, 0);
+	mptcp_sock_graft(msk->first, sk->sk_socket);
+	iput(SOCK_INODE(ssock));
+
+	return 0;
+}
+
+/* If the MPC handshake is not started, returns the first subflow,
+ * eventually allocating it.
+ */
+struct sock *__mptcp_nmpc_sk(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+	int ret;
+
+	if (!((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
+		return ERR_PTR(-EINVAL);
+
+	if (!msk->first) {
+		ret = __mptcp_socket_create(msk);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
+	return msk->first;
+}
+
+static void mptcp_drop(struct sock *sk, struct sk_buff *skb)
+{
+	/* The skb forward memory was already transferred to sk by
+	 * mptcp_borrow_fwdmem(), even before setting the destructor.
+	 */
+	if (!skb->destructor)
+		sk_mem_reclaim(sk);
+
+	sk_drops_skbadd(sk, skb);
+	__kfree_skb(skb);
+}
+
+static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to,
+				 struct sk_buff *from, bool *fragstolen,
+				 int *delta)
+{
+	int limit = READ_ONCE(sk->sk_rcvbuf);
+
+	if (unlikely(MPTCP_SKB_CB(to)->cant_coalesce) ||
+	    MPTCP_SKB_CB(from)->offset ||
+	    ((to->len + from->len) > (limit >> 3)) ||
+	    !skb_try_coalesce(to, from, fragstolen, delta))
+		return false;
+
+	pr_debug("colesced seq %llx into %llx new len %d new end seq %llx\n",
+		 MPTCP_SKB_CB(from)->map_seq, MPTCP_SKB_CB(to)->map_seq,
+		 to->len, MPTCP_SKB_CB(from)->end_seq);
+	MPTCP_SKB_CB(to)->end_seq = MPTCP_SKB_CB(from)->end_seq;
+	return true;
+}
+
+static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to,
+			       struct sk_buff *from)
+{
+	bool fragstolen;
+	int delta;
+
+	if (!__mptcp_try_coalesce(sk, to, from, &fragstolen, &delta))
+		return false;
+
+	/* note the fwd memory can reach a negative value after accounting
+	 * for the delta, but the later skb free will restore a non
+	 * negative one
+	 */
+	atomic_add(delta, &sk->sk_rmem_alloc);
+	sk_mem_charge(sk, delta);
+	kfree_skb_partial(from, fragstolen);
+
+	return true;
+}
+
+static bool mptcp_ooo_try_coalesce(struct mptcp_sock *msk, struct sk_buff *to,
+				   struct sk_buff *from)
+{
+	if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq)
+		return false;
+
+	return mptcp_try_coalesce((struct sock *)msk, to, from);
+}
+
+/* "inspired" by tcp_rcvbuf_grow(), main difference:
+ * - mptcp does not maintain a msk-level window clamp
+ * - returns true when  the receive buffer is actually updated
+ */
+static bool mptcp_rcvbuf_grow(struct sock *sk, u32 newval)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	const struct net *net = sock_net(sk);
+	u32 rcvwin, rcvbuf, cap, oldval;
+	u64 grow;
+
+	oldval = msk->rcvq_space.space;
+	msk->rcvq_space.space = newval;
+	if (!READ_ONCE(net->ipv4.sysctl_tcp_moderate_rcvbuf) ||
+	    (sk->sk_userlocks & SOCK_RCVBUF_LOCK))
+		return false;
+
+	/* DRS is always one RTT late. */
+	rcvwin = newval << 1;
+
+	/* slow start: allow the sender to double its rate. */
+	grow = (u64)rcvwin * (newval - oldval);
+	do_div(grow, oldval);
+	rcvwin += grow << 1;
+
+	cap = READ_ONCE(net->ipv4.sysctl_tcp_rmem[2]);
+
+	rcvbuf = min_t(u32, mptcp_space_from_win(sk, rcvwin), cap);
+	if (rcvbuf > sk->sk_rcvbuf) {
+		WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);
+		return true;
+	}
+	return false;
+}
+
+/* "Inspired" from the TCP version; main difference: stop as soon as the MPTCP
+ * socket is under memory limit.
+ */
+static void mptcp_prune_ofo_queue(struct sock *sk,
+				  const struct sk_buff *in_skb)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct rb_node *node, *prev;
+	bool pruned = false;
+	u64 mem;
+
+	if (RB_EMPTY_ROOT(&msk->out_of_order_queue))
+		return;
+
+	node = &msk->ooo_last_skb->rbnode;
+
+	do {
+		struct sk_buff *skb = rb_to_skb(node);
+
+		/* Stop pruning if the incoming skb would land in OoO tail. */
+		if (after64(MPTCP_SKB_CB(in_skb)->map_seq,
+			    MPTCP_SKB_CB(skb)->map_seq))
+			break;
+
+		pruned = true;
+		prev = rb_prev(node);
+		rb_erase(node, &msk->out_of_order_queue);
+		mptcp_drop(sk, skb);
+		msk->ooo_last_skb = rb_to_skb(prev);
+
+		mem = (unsigned int)sk_rmem_alloc_get(sk);
+		if (mem <= sk->sk_rcvbuf)
+			break;
+
+		node = prev;
+	} while (node);
+
+	if (pruned)
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOPRUNED);
+}
+
+/* The stack can't drop packets for fallback socket at the msk level, or the
+ * stream will break.
+ */
+static bool mptcp_can_ingest(const struct sock *sk)
+{
+	return likely(sk_rmem_alloc_get(sk) <= READ_ONCE(sk->sk_rcvbuf)) ||
+	       __mptcp_check_fallback(mptcp_sk(sk));
+}
+
+static bool mptcp_try_rmem_schedule(struct sock *sk, const struct sk_buff *skb)
+{
+	if (!mptcp_can_ingest(sk)) {
+		mptcp_prune_ofo_queue(sk, skb);
+		return mptcp_can_ingest(sk);
+	}
+	return true;
+}
+
+/* "inspired" by tcp_data_queue_ofo(), main differences:
+ * - use mptcp seqs
+ * - don't cope with sacks
+ */
+static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct rb_node **p, *parent;
+	u64 seq, end_seq, max_seq;
+	struct sk_buff *skb1;
+
+	seq = MPTCP_SKB_CB(skb)->map_seq;
+	end_seq = MPTCP_SKB_CB(skb)->end_seq;
+	max_seq = atomic64_read(&msk->rcv_wnd_sent);
+
+	pr_debug("msk=%p seq=%llx limit=%llx empty=%d\n", msk, seq, max_seq,
+		 RB_EMPTY_ROOT(&msk->out_of_order_queue));
+	if (after64(end_seq, max_seq)) {
+		/* out of window */
+		mptcp_drop(sk, skb);
+		pr_debug("oow by %lld, rcv_wnd_sent %llu\n",
+			 (unsigned long long)end_seq - (unsigned long)max_seq,
+			 (unsigned long long)atomic64_read(&msk->rcv_wnd_sent));
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_NODSSWINDOW);
+		return;
+	}
+
+	if (!mptcp_try_rmem_schedule(sk, skb)) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED);
+		mptcp_drop(sk, skb);
+		return;
+	}
+
+	p = &msk->out_of_order_queue.rb_node;
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUE);
+	if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) {
+		rb_link_node(&skb->rbnode, NULL, p);
+		rb_insert_color(&skb->rbnode, &msk->out_of_order_queue);
+		msk->ooo_last_skb = skb;
+		goto end;
+	}
+
+	/* with 2 subflows, adding at end of ooo queue is quite likely
+	 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
+	 */
+	if (mptcp_ooo_try_coalesce(msk, msk->ooo_last_skb, skb)) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE);
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL);
+		return;
+	}
+
+	/* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
+	if (!before64(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL);
+		parent = &msk->ooo_last_skb->rbnode;
+		p = &parent->rb_right;
+		goto insert;
+	}
+
+	/* Find place to insert this segment. Handle overlaps on the way. */
+	parent = NULL;
+	while (*p) {
+		parent = *p;
+		skb1 = rb_to_skb(parent);
+		if (before64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
+			p = &parent->rb_left;
+			continue;
+		}
+		if (before64(seq, MPTCP_SKB_CB(skb1)->end_seq)) {
+			if (!after64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) {
+				/* All the bits are present. Drop. */
+				mptcp_drop(sk, skb);
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+				return;
+			}
+			if (after64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
+				/* partial overlap:
+				 *     |     skb      |
+				 *  |     skb1    |
+				 * continue traversing
+				 */
+			} else {
+				/* skb's seq == skb1's seq and skb covers skb1.
+				 * Replace skb1 with skb.
+				 */
+				rb_replace_node(&skb1->rbnode, &skb->rbnode,
+						&msk->out_of_order_queue);
+				mptcp_drop(sk, skb1);
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+				goto merge_right;
+			}
+		} else if (mptcp_ooo_try_coalesce(msk, skb1, skb)) {
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE);
+			return;
+		}
+		p = &parent->rb_right;
+	}
+
+insert:
+	/* Insert segment into RB tree. */
+	rb_link_node(&skb->rbnode, parent, p);
+	rb_insert_color(&skb->rbnode, &msk->out_of_order_queue);
+
+merge_right:
+	/* Remove other segments covered by skb. */
+	while ((skb1 = skb_rb_next(skb)) != NULL) {
+		if (before64(end_seq, MPTCP_SKB_CB(skb1)->end_seq))
+			break;
+		rb_erase(&skb1->rbnode, &msk->out_of_order_queue);
+		mptcp_drop(sk, skb1);
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+	}
+	/* If there is no skb after us, we are the last_skb ! */
+	if (!skb1)
+		msk->ooo_last_skb = skb;
+
+end:
+	skb_condense(skb);
+	skb_set_owner_r(skb, sk);
+}
+
+static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset,
+			   int copy_len)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	bool has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp;
+
+	/* the skb map_seq accounts for the skb offset:
+	 * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq
+	 * value
+	 */
+	MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow);
+	MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len;
+	MPTCP_SKB_CB(skb)->offset = offset;
+	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
+	MPTCP_SKB_CB(skb)->cant_coalesce = 0;
+
+	__skb_unlink(skb, &ssk->sk_receive_queue);
+
+	skb_ext_reset(skb);
+	skb_dst_drop(skb);
+}
+
+static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb)
+{
+	u64 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *tail;
+
+	mptcp_borrow_fwdmem(sk, skb);
+
+	if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) {
+		/* in sequence */
+insert:
+		if (!mptcp_try_rmem_schedule(sk, skb)) {
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED);
+			mptcp_drop(sk, skb);
+			return false;
+		}
+
+		msk->bytes_received += copy_len;
+		WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len);
+		tail = skb_peek_tail(&sk->sk_receive_queue);
+		if (tail && mptcp_try_coalesce(sk, tail, skb))
+			return true;
+
+		skb_set_owner_r(skb, sk);
+		__skb_queue_tail(&sk->sk_receive_queue, skb);
+		return true;
+	} else if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) {
+		mptcp_data_queue_ofo(msk, skb);
+		return false;
+	}
+
+	/* Partial packet */
+	if (after64(MPTCP_SKB_CB(skb)->end_seq, msk->ack_seq)) {
+		copy_len = MPTCP_SKB_CB(skb)->end_seq - msk->ack_seq;
+		MPTCP_SKB_CB(skb)->offset += msk->ack_seq -
+					     MPTCP_SKB_CB(skb)->map_seq;
+		MPTCP_SKB_CB(skb)->map_seq += msk->ack_seq -
+					      MPTCP_SKB_CB(skb)->map_seq;
+		goto insert;
+	}
+
+	/* Completely old data */
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+	mptcp_drop(sk, skb);
+	return false;
+}
+
+static void mptcp_stop_rtx_timer(struct sock *sk)
+{
+	sk_stop_timer(sk, &sk->mptcp_retransmit_timer);
+	mptcp_sk(sk)->timer_ival = 0;
+}
+
+static void mptcp_close_wake_up(struct sock *sk)
+{
+	if (sock_flag(sk, SOCK_DEAD))
+		return;
+
+	sk->sk_state_change(sk);
+	if (sk->sk_shutdown == SHUTDOWN_MASK ||
+	    sk->sk_state == TCP_CLOSE)
+		sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
+	else
+		sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
+}
+
+static void mptcp_shutdown_subflows(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow;
+
+		slow = lock_sock_fast(ssk);
+		tcp_shutdown(ssk, SEND_SHUTDOWN);
+		unlock_sock_fast(ssk, slow);
+	}
+}
+
+/* called under the msk socket lock */
+static bool mptcp_pending_data_fin_ack(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	return ((1 << sk->sk_state) &
+		(TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK)) &&
+	       msk->write_seq == READ_ONCE(msk->snd_una);
+}
+
+static void mptcp_check_data_fin_ack(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	/* Look for an acknowledged DATA_FIN */
+	if (mptcp_pending_data_fin_ack(sk)) {
+		WRITE_ONCE(msk->snd_data_fin_enable, 0);
+
+		switch (sk->sk_state) {
+		case TCP_FIN_WAIT1:
+			mptcp_set_state(sk, TCP_FIN_WAIT2);
+			break;
+		case TCP_CLOSING:
+		case TCP_LAST_ACK:
+			mptcp_shutdown_subflows(msk);
+			mptcp_set_state(sk, TCP_CLOSE);
+			break;
+		}
+
+		mptcp_close_wake_up(sk);
+	}
+}
+
+/* can be called with no lock acquired */
+static bool mptcp_pending_data_fin(struct sock *sk, u64 *seq)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (READ_ONCE(msk->rcv_data_fin) &&
+	    ((1 << inet_sk_state_load(sk)) &
+	     (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2))) {
+		u64 rcv_data_fin_seq = READ_ONCE(msk->rcv_data_fin_seq);
+
+		if (READ_ONCE(msk->ack_seq) == rcv_data_fin_seq) {
+			if (seq)
+				*seq = rcv_data_fin_seq;
+
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static void mptcp_set_datafin_timeout(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	u32 rto_min = READ_ONCE(icsk->icsk_rto_min);
+	u32 rto_max = READ_ONCE(icsk->icsk_rto_max);
+	u32 retransmits;
+
+	/* The sysctls are validated independently: rto_min > rto_max is
+	 * possible, guard against ilog2(0).
+	 */
+	retransmits = min_t(u32, icsk->icsk_retransmits,
+			    ilog2(max_t(u32, rto_max / rto_min, 1)));
+
+	mptcp_sk(sk)->timer_ival = rto_min << retransmits;
+}
+
+static void __mptcp_set_timeout(struct sock *sk, long tout)
+{
+	mptcp_sk(sk)->timer_ival = tout > 0 ? tout :
+				   READ_ONCE(inet_csk(sk)->icsk_rto_min);
+}
+
+static long mptcp_timeout_from_subflow(const struct mptcp_subflow_context *subflow)
+{
+	const struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+	return inet_csk(ssk)->icsk_pending && !subflow->stale_count ?
+	       tcp_timeout_expires(ssk) - jiffies : 0;
+}
+
+static void mptcp_set_timeout(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	long tout = 0;
+
+	mptcp_for_each_subflow(mptcp_sk(sk), subflow)
+		tout = max(tout, mptcp_timeout_from_subflow(subflow));
+	__mptcp_set_timeout(sk, tout);
+}
+
+static inline bool tcp_can_send_ack(const struct sock *ssk)
+{
+	return !((1 << inet_sk_state_load(ssk)) &
+	       (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_TIME_WAIT | TCPF_CLOSE | TCPF_LISTEN));
+}
+
+void __mptcp_subflow_send_ack(struct sock *ssk)
+{
+	if (tcp_can_send_ack(ssk))
+		tcp_send_ack(ssk);
+}
+
+static void mptcp_subflow_send_ack(struct sock *ssk)
+{
+	bool slow;
+
+	slow = lock_sock_fast(ssk);
+	__mptcp_subflow_send_ack(ssk);
+	unlock_sock_fast(ssk, slow);
+}
+
+static void mptcp_send_ack(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+
+	mptcp_for_each_subflow(msk, subflow)
+		mptcp_subflow_send_ack(mptcp_subflow_tcp_sock(subflow));
+}
+
+static void mptcp_subflow_cleanup_rbuf(struct sock *ssk, int copied)
+{
+	bool slow;
+
+	slow = lock_sock_fast(ssk);
+	if (tcp_can_send_ack(ssk))
+		tcp_cleanup_rbuf(ssk, copied);
+	unlock_sock_fast(ssk, slow);
+}
+
+static bool mptcp_subflow_could_cleanup(const struct sock *ssk, bool rx_empty)
+{
+	const struct inet_connection_sock *icsk = inet_csk(ssk);
+	u8 ack_pending = READ_ONCE(icsk->icsk_ack.pending);
+	const struct tcp_sock *tp = tcp_sk(ssk);
+
+	return (ack_pending & ICSK_ACK_SCHED) &&
+		((READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->rcv_wup) >
+		  READ_ONCE(icsk->icsk_ack.rcv_mss)) ||
+		 (rx_empty && ack_pending &
+			      (ICSK_ACK_PUSHED2 | ICSK_ACK_PUSHED)));
+}
+
+static void mptcp_cleanup_rbuf(struct mptcp_sock *msk, int copied)
+{
+	int old_space = READ_ONCE(msk->old_wspace);
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	int space =  __mptcp_space(sk);
+	bool cleanup, rx_empty;
+
+	cleanup = (space > 0) && (space >= (old_space << 1)) && copied;
+	rx_empty = !sk_rmem_alloc_get(sk) && copied;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (cleanup || mptcp_subflow_could_cleanup(ssk, rx_empty))
+			mptcp_subflow_cleanup_rbuf(ssk, copied);
+	}
+}
+
+static void mptcp_check_data_fin(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	u64 rcv_data_fin_seq;
+
+	/* Need to ack a DATA_FIN received from a peer while this side
+	 * of the connection is in ESTABLISHED, FIN_WAIT1, or FIN_WAIT2.
+	 * msk->rcv_data_fin was set when parsing the incoming options
+	 * at the subflow level and the msk lock was not held, so this
+	 * is the first opportunity to act on the DATA_FIN and change
+	 * the msk state.
+	 *
+	 * If we are caught up to the sequence number of the incoming
+	 * DATA_FIN, send the DATA_ACK now and do state transition.  If
+	 * not caught up, do nothing and let the recv code send DATA_ACK
+	 * when catching up.
+	 */
+
+	if (mptcp_pending_data_fin(sk, &rcv_data_fin_seq)) {
+		WRITE_ONCE(msk->ack_seq, msk->ack_seq + 1);
+		WRITE_ONCE(msk->rcv_data_fin, 0);
+
+		WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | RCV_SHUTDOWN);
+		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
+
+		switch (sk->sk_state) {
+		case TCP_ESTABLISHED:
+			mptcp_set_state(sk, TCP_CLOSE_WAIT);
+			break;
+		case TCP_FIN_WAIT1:
+			mptcp_set_state(sk, TCP_CLOSING);
+			break;
+		case TCP_FIN_WAIT2:
+			mptcp_shutdown_subflows(msk);
+			mptcp_set_state(sk, TCP_CLOSE);
+			break;
+		default:
+			/* Other states not expected */
+			WARN_ON_ONCE(1);
+			break;
+		}
+
+		if (!__mptcp_check_fallback(msk))
+			mptcp_send_ack(msk);
+		mptcp_close_wake_up(sk);
+	}
+}
+
+static void mptcp_dss_corruption(struct mptcp_sock *msk, struct sock *ssk)
+{
+	if (!mptcp_try_fallback(ssk, MPTCP_MIB_DSSCORRUPTIONFALLBACK)) {
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSCORRUPTIONRESET);
+		mptcp_subflow_reset(ssk);
+	}
+}
+
+static void __mptcp_add_backlog(struct sock *sk,
+				struct mptcp_subflow_context *subflow,
+				struct sk_buff *skb)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *tail = NULL;
+	struct sock *ssk = skb->sk;
+	bool fragstolen;
+	u64 limit;
+	int delta;
+
+	if (unlikely(sk->sk_state == TCP_CLOSE)) {
+		kfree_skb_reason(skb, SKB_DROP_REASON_SOCKET_CLOSE);
+		return;
+	}
+
+	/* Similar additional allowance as plain TCP. */
+	limit = READ_ONCE(sk->sk_rcvbuf);
+	limit += (limit >> 1) + 64 * 1024;
+	limit = min_t(u64, limit, UINT_MAX);
+	if (msk->backlog_len > limit && !__mptcp_check_fallback(msk)) {
+		__MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_BACKLOGDROP);
+		kfree_skb_reason(skb, SKB_DROP_REASON_SOCKET_BACKLOG);
+		return;
+	}
+
+	/* Try to coalesce with the last skb in our backlog */
+	if (!list_empty(&msk->backlog_list))
+		tail = list_last_entry(&msk->backlog_list, struct sk_buff, list);
+
+	if (tail && MPTCP_SKB_CB(skb)->map_seq == MPTCP_SKB_CB(tail)->end_seq &&
+	    ssk == tail->sk &&
+	    __mptcp_try_coalesce(sk, tail, skb, &fragstolen, &delta)) {
+		skb->truesize -= delta;
+		kfree_skb_partial(skb, fragstolen);
+		__mptcp_subflow_lend_fwdmem(subflow, delta);
+		goto account;
+	}
+
+	list_add_tail(&skb->list, &msk->backlog_list);
+	mptcp_subflow_lend_fwdmem(subflow, skb);
+	delta = skb->truesize;
+
+account:
+	WRITE_ONCE(msk->backlog_len, msk->backlog_len + delta);
+
+	/* Possibly not accept()ed yet, keep track of memory not CG
+	 * accounted, mptcp_graft_subflows() will handle it.
+	 */
+	if (!mem_cgroup_from_sk(ssk))
+		msk->backlog_unaccounted += delta;
+}
+
+static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
+					   struct sock *ssk, bool own_msk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = (struct sock *)msk;
+	bool more_data_avail;
+	struct tcp_sock *tp;
+	bool ret = false;
+
+	pr_debug("msk=%p ssk=%p\n", msk, ssk);
+	tp = tcp_sk(ssk);
+	do {
+		u32 map_remaining, offset;
+		u32 seq = tp->copied_seq;
+		struct sk_buff *skb;
+		bool fin;
+
+		/* try to move as much data as available */
+		map_remaining = subflow->map_data_len -
+				mptcp_subflow_get_map_offset(subflow);
+
+		skb = skb_peek(&ssk->sk_receive_queue);
+		if (unlikely(!skb))
+			break;
+
+		if (__mptcp_check_fallback(msk)) {
+			/* Under fallback skbs have no MPTCP extension and TCP could
+			 * collapse them between the dummy map creation and the
+			 * current dequeue. Be sure to adjust the map size.
+			 */
+			map_remaining = skb->len;
+			subflow->map_data_len = skb->len;
+		}
+
+		offset = seq - TCP_SKB_CB(skb)->seq;
+		fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
+		if (fin)
+			seq++;
+
+		if (offset < skb->len) {
+			size_t len = skb->len - offset;
+
+			mptcp_init_skb(ssk, skb, offset, len);
+
+			if (own_msk) {
+				mptcp_subflow_lend_fwdmem(subflow, skb);
+				ret |= __mptcp_move_skb(sk, skb);
+			} else {
+				__mptcp_add_backlog(sk, subflow, skb);
+			}
+			seq += len;
+
+			if (unlikely(map_remaining < len)) {
+				DEBUG_NET_WARN_ON_ONCE(1);
+				mptcp_dss_corruption(msk, ssk);
+			}
+		} else {
+			if (unlikely(!fin)) {
+				DEBUG_NET_WARN_ON_ONCE(1);
+				mptcp_dss_corruption(msk, ssk);
+			}
+
+			sk_eat_skb(ssk, skb);
+		}
+
+		WRITE_ONCE(tp->copied_seq, seq);
+		more_data_avail = mptcp_subflow_data_available(ssk);
+
+	} while (more_data_avail);
+
+	if (ret)
+		msk->last_data_recv = tcp_jiffies32;
+	return ret;
+}
+
+static bool __mptcp_ofo_queue(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct sk_buff *skb, *tail;
+	bool moved = false;
+	struct rb_node *p;
+	u64 end_seq;
+
+	p = rb_first(&msk->out_of_order_queue);
+	pr_debug("msk=%p empty=%d\n", msk, RB_EMPTY_ROOT(&msk->out_of_order_queue));
+	while (p) {
+		skb = rb_to_skb(p);
+		if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq))
+			break;
+
+		p = rb_next(p);
+		rb_erase(&skb->rbnode, &msk->out_of_order_queue);
+
+		if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq,
+				      msk->ack_seq))) {
+			mptcp_drop(sk, skb);
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
+			continue;
+		}
+
+		end_seq = MPTCP_SKB_CB(skb)->end_seq;
+		tail = skb_peek_tail(&sk->sk_receive_queue);
+		if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) {
+			int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq;
+
+			/* skip overlapping data, if any */
+			pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d\n",
+				 MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq,
+				 delta);
+			MPTCP_SKB_CB(skb)->offset += delta;
+			MPTCP_SKB_CB(skb)->map_seq += delta;
+			__skb_queue_tail(&sk->sk_receive_queue, skb);
+		}
+		msk->bytes_received += end_seq - msk->ack_seq;
+		WRITE_ONCE(msk->ack_seq, end_seq);
+		moved = true;
+	}
+	return moved;
+}
+
+static bool __mptcp_subflow_error_report(struct sock *sk, struct sock *ssk)
+{
+	int ssk_state;
+	int err;
+
+	/* only propagate errors on fallen-back sockets or
+	 * on MPC connect
+	 */
+	if (sk->sk_state != TCP_SYN_SENT && !__mptcp_check_fallback(mptcp_sk(sk)))
+		return false;
+
+	err = sock_error(ssk);
+	if (!err)
+		return false;
+
+	/* We need to propagate only transition to CLOSE state.
+	 * Orphaned socket will see such state change via
+	 * subflow_sched_work_if_closed() and that path will properly
+	 * destroy the msk as needed.
+	 */
+	ssk_state = inet_sk_state_load(ssk);
+	if (ssk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DEAD))
+		mptcp_set_state(sk, ssk_state);
+	WRITE_ONCE(sk->sk_err, -err);
+
+	/* This barrier is coupled with smp_rmb() in mptcp_poll() */
+	smp_wmb();
+	sk_error_report(sk);
+	return true;
+}
+
+void __mptcp_error_report(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	mptcp_for_each_subflow(msk, subflow)
+		if (__mptcp_subflow_error_report(sk, mptcp_subflow_tcp_sock(subflow)))
+			break;
+}
+
+/* In most cases we will be able to lock the mptcp socket.  If its already
+ * owned, we need to defer to the work queue to avoid ABBA deadlock.
+ */
+static bool move_skbs_to_msk(struct mptcp_sock *msk, struct sock *ssk)
+{
+	struct sock *sk = (struct sock *)msk;
+	bool moved;
+
+	moved = __mptcp_move_skbs_from_subflow(msk, ssk, true);
+	__mptcp_ofo_queue(msk);
+	if (unlikely(ssk->sk_err))
+		__mptcp_subflow_error_report(sk, ssk);
+
+	/* If the moves have caught up with the DATA_FIN sequence number
+	 * it's time to ack the DATA_FIN and change socket state, but
+	 * this is not a good place to change state. Let the workqueue
+	 * do it.
+	 */
+	if (mptcp_pending_data_fin(sk, NULL))
+		mptcp_schedule_work(sk);
+	return moved;
+}
+
+static void mptcp_rcv_rtt_update(struct mptcp_sock *msk,
+				 struct mptcp_subflow_context *subflow)
+{
+	const struct tcp_sock *tp = tcp_sk(subflow->tcp_sock);
+	u32 rtt_us = tp->rcv_rtt_est.rtt_us;
+	int id;
+
+	/* Update once per subflow per rcvwnd to avoid touching the msk
+	 * too often.
+	 */
+	if (!rtt_us || tp->rcv_rtt_est.seq == subflow->prev_rtt_seq)
+		return;
+
+	subflow->prev_rtt_seq = tp->rcv_rtt_est.seq;
+
+	/* Pairs with READ_ONCE() in mptcp_rtt_us_est(). */
+	id = msk->rcv_rtt_est.next_sample;
+	WRITE_ONCE(msk->rcv_rtt_est.samples[id], rtt_us);
+	if (++msk->rcv_rtt_est.next_sample == MPTCP_RTT_SAMPLES)
+		msk->rcv_rtt_est.next_sample = 0;
+
+	/* EWMA among the incoming subflows */
+	msk->scaling_ratio = ((msk->scaling_ratio << 3) - msk->scaling_ratio +
+			     tp->scaling_ratio) >> 3;
+}
+
+void mptcp_data_ready(struct sock *sk, struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	/* The peer can send data while we are shutting down this
+	 * subflow at subflow destruction time, but we must avoid enqueuing
+	 * more data to the msk receive queue
+	 */
+	if (unlikely(subflow->closing))
+		return;
+
+	mptcp_data_lock(sk);
+	mptcp_rcv_rtt_update(msk, subflow);
+	if (!sock_owned_by_user(sk)) {
+		/* Wake-up the reader only for in-sequence data */
+		if (move_skbs_to_msk(msk, ssk) && mptcp_epollin_ready(sk))
+			sk->sk_data_ready(sk);
+	} else {
+		__mptcp_move_skbs_from_subflow(msk, ssk, false);
+	}
+	mptcp_data_unlock(sk);
+}
+
+static void mptcp_subflow_joined(struct mptcp_sock *msk, struct sock *ssk)
+{
+	mptcp_subflow_ctx(ssk)->map_seq = READ_ONCE(msk->ack_seq);
+	msk->allow_infinite_fallback = false;
+	mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC);
+}
+
+static bool __mptcp_finish_join(struct mptcp_sock *msk, struct sock *ssk)
+{
+	struct sock *sk = (struct sock *)msk;
+
+	if (sk->sk_state != TCP_ESTABLISHED)
+		return false;
+
+	spin_lock_bh(&msk->fallback_lock);
+	if (!msk->allow_subflows) {
+		spin_unlock_bh(&msk->fallback_lock);
+		return false;
+	}
+	mptcp_subflow_joined(msk, ssk);
+	spin_unlock_bh(&msk->fallback_lock);
+
+	mptcp_subflow_ctx(ssk)->subflow_id = msk->subflow_id++;
+	mptcp_sockopt_sync_locked(msk, ssk);
+	mptcp_stop_tout_timer(sk);
+	__mptcp_propagate_sndbuf(sk, ssk);
+	return true;
+}
+
+static void __mptcp_flush_join_list(struct sock *sk, struct list_head *join_list)
+{
+	struct mptcp_subflow_context *tmp, *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	list_for_each_entry_safe(subflow, tmp, join_list, node) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow = lock_sock_fast(ssk);
+
+		list_move_tail(&subflow->node, &msk->conn_list);
+		if (!__mptcp_finish_join(msk, ssk))
+			mptcp_subflow_reset(ssk);
+		unlock_sock_fast(ssk, slow);
+	}
+}
+
+static bool mptcp_rtx_timer_pending(struct sock *sk)
+{
+	return timer_pending(&sk->mptcp_retransmit_timer);
+}
+
+static void mptcp_reset_rtx_timer(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	unsigned long tout;
+
+	/* Prevent rescheduling on close and in case of fallback. */
+	if (!test_bit(MPTCP_RTX_ENABLED, &msk->flags))
+		return;
+
+	tout = msk->timer_ival;
+	sk_reset_timer(sk, &sk->mptcp_retransmit_timer, jiffies + tout);
+}
+
+bool mptcp_schedule_work(struct sock *sk)
+{
+	if (inet_sk_state_load(sk) == TCP_CLOSE)
+		return false;
+
+	/* Get a reference on this socket, mptcp_worker() will release it.
+	 * As mptcp_worker() might complete before us, we can not avoid
+	 * a sock_hold()/sock_put() if schedule_work() returns false.
+	 */
+	sock_hold(sk);
+
+	if (schedule_work(&mptcp_sk(sk)->work))
+		return true;
+
+	sock_put(sk);
+	return false;
+}
+
+static bool mptcp_skb_can_collapse_to(u64 write_seq,
+				      const struct sk_buff *skb,
+				      const struct mptcp_ext *mpext)
+{
+	if (!tcp_skb_can_collapse_to(skb))
+		return false;
+
+	/* can collapse only if MPTCP level sequence is in order and this
+	 * mapping has not been xmitted yet
+	 */
+	return mpext && mpext->data_seq + mpext->data_len == write_seq &&
+	       !mpext->frozen;
+}
+
+/* we can append data to the given data frag if:
+ * - there is space available in the backing page_frag
+ * - the data frag tail matches the current page_frag free offset
+ * - the data frag end sequence number matches the current write seq
+ */
+static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
+				       const struct page_frag *pfrag,
+				       const struct mptcp_data_frag *df)
+{
+	return df && !df->eor &&
+		pfrag->page == df->page &&
+		pfrag->size - pfrag->offset > 0 &&
+		pfrag->offset == (df->offset + df->data_len) &&
+		df->data_seq + df->data_len == msk->write_seq;
+}
+
+static void dfrag_uncharge(struct sock *sk, int len)
+{
+	sk_mem_uncharge(sk, len);
+	sk_wmem_queued_add(sk, -len);
+}
+
+static void dfrag_clear(struct sock *sk, struct mptcp_data_frag *dfrag)
+{
+	int len = dfrag->data_len + dfrag->overhead;
+
+	list_del(&dfrag->list);
+	dfrag_uncharge(sk, len);
+	put_page(dfrag->page);
+}
+
+/* called under both the msk socket lock and the data lock */
+static void __mptcp_clean_una(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_data_frag *dtmp, *dfrag;
+	u64 snd_una;
+
+	snd_una = msk->snd_una;
+	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) {
+		if (after64(dfrag->data_seq + dfrag->data_len, snd_una))
+			break;
+
+		if (unlikely(dfrag == msk->first_pending)) {
+			/* in recovery mode can see ack after the current snd head */
+			if (WARN_ON_ONCE(!msk->recovery))
+				break;
+
+			msk->first_pending = mptcp_send_next(sk);
+		}
+
+		dfrag_clear(sk, dfrag);
+	}
+
+	dfrag = mptcp_rtx_head(sk);
+	if (dfrag && after64(snd_una, dfrag->data_seq)) {
+		u64 delta = snd_una - dfrag->data_seq;
+
+		/* prevent wrap around in recovery mode */
+		if (unlikely(delta > dfrag->already_sent)) {
+			if (WARN_ON_ONCE(!msk->recovery))
+				goto out;
+			if (WARN_ON_ONCE(delta > dfrag->data_len))
+				goto out;
+			dfrag->already_sent += delta - dfrag->already_sent;
+		}
+
+		dfrag->data_seq += delta;
+		dfrag->offset += delta;
+		dfrag->data_len -= delta;
+		dfrag->already_sent -= delta;
+
+		dfrag_uncharge(sk, delta);
+	}
+
+	/* all retransmitted data acked, recovery completed */
+	if (unlikely(msk->recovery) && after64(msk->snd_una, msk->recovery_snd_nxt))
+		msk->recovery = false;
+
+out:
+	if (snd_una == msk->snd_nxt && snd_una == msk->write_seq) {
+		if (mptcp_rtx_timer_pending(sk) && !mptcp_data_fin_enabled(msk))
+			mptcp_stop_rtx_timer(sk);
+	} else {
+		mptcp_reset_rtx_timer(sk);
+	}
+
+	if (mptcp_pending_data_fin_ack(sk))
+		mptcp_schedule_work(sk);
+}
+
+static void __mptcp_clean_una_wakeup(struct sock *sk)
+{
+	lockdep_assert_held_once(&sk->sk_lock.slock);
+
+	__mptcp_clean_una(sk);
+	mptcp_write_space(sk);
+}
+
+static void mptcp_enter_memory_pressure(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool first = true;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (first && !ssk->sk_bypass_prot_mem) {
+			tcp_enter_memory_pressure(ssk);
+			first = false;
+		}
+
+		sk_stream_moderate_sndbuf(ssk);
+	}
+	__mptcp_sync_sndbuf(sk);
+}
+
+/* ensure we get enough memory for the frag hdr, beyond some minimal amount of
+ * data
+ */
+static bool mptcp_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
+{
+	if (likely(skb_page_frag_refill(32U + sizeof(struct mptcp_data_frag),
+					pfrag, sk->sk_allocation)))
+		return true;
+
+	mptcp_enter_memory_pressure(sk);
+	return false;
+}
+
+static struct mptcp_data_frag *
+mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
+		      int orig_offset)
+{
+	int offset = ALIGN(orig_offset, sizeof(long));
+	struct mptcp_data_frag *dfrag;
+
+	dfrag = (struct mptcp_data_frag *)(page_to_virt(pfrag->page) + offset);
+	dfrag->data_len = 0;
+	dfrag->data_seq = msk->write_seq;
+	dfrag->overhead = offset - orig_offset + sizeof(struct mptcp_data_frag);
+	dfrag->offset = offset + sizeof(struct mptcp_data_frag);
+	dfrag->already_sent = 0;
+	dfrag->page = pfrag->page;
+	dfrag->eor = 0;
+
+	return dfrag;
+}
+
+struct mptcp_sendmsg_info {
+	int mss_now;
+	int size_goal;
+	u16 limit;
+	u16 sent;
+	unsigned int flags;
+	bool data_lock_held;
+};
+
+static size_t mptcp_check_allowed_size(const struct mptcp_sock *msk,
+				       struct sock *ssk, u64 data_seq,
+				       size_t avail_size)
+{
+	u64 window_end = mptcp_wnd_end(msk);
+	u64 mptcp_snd_wnd;
+
+	if (__mptcp_check_fallback(msk))
+		return avail_size;
+
+	mptcp_snd_wnd = window_end - data_seq;
+	avail_size = min(mptcp_snd_wnd, avail_size);
+
+	if (unlikely(tcp_sk(ssk)->snd_wnd < mptcp_snd_wnd)) {
+		tcp_sk(ssk)->snd_wnd = min_t(u64, U32_MAX, mptcp_snd_wnd);
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_SNDWNDSHARED);
+	}
+
+	return avail_size;
+}
+
+static bool __mptcp_add_ext(struct sk_buff *skb, gfp_t gfp)
+{
+	struct skb_ext *mpext = __skb_ext_alloc(gfp);
+
+	if (!mpext)
+		return false;
+	__skb_ext_set(skb, SKB_EXT_MPTCP, mpext);
+	return true;
+}
+
+static struct sk_buff *__mptcp_do_alloc_tx_skb(struct sock *sk, gfp_t gfp)
+{
+	struct sk_buff *skb;
+
+	skb = alloc_skb_fclone(MAX_TCP_HEADER, gfp);
+	if (likely(skb)) {
+		if (likely(__mptcp_add_ext(skb, gfp))) {
+			skb_reserve(skb, MAX_TCP_HEADER);
+			skb->ip_summed = CHECKSUM_PARTIAL;
+			INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
+			return skb;
+		}
+		__kfree_skb(skb);
+	} else {
+		mptcp_enter_memory_pressure(sk);
+	}
+	return NULL;
+}
+
+static struct sk_buff *__mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk, gfp_t gfp)
+{
+	struct sk_buff *skb;
+
+	skb = __mptcp_do_alloc_tx_skb(sk, gfp);
+	if (!skb)
+		return NULL;
+
+	if (likely(sk_wmem_schedule(ssk, skb->truesize))) {
+		tcp_skb_entail(ssk, skb);
+		return skb;
+	}
+	tcp_skb_tsorted_anchor_cleanup(skb);
+	kfree_skb(skb);
+	return NULL;
+}
+
+static struct sk_buff *mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk, bool data_lock_held)
+{
+	gfp_t gfp = data_lock_held ? GFP_ATOMIC : sk->sk_allocation;
+
+	return __mptcp_alloc_tx_skb(sk, ssk, gfp);
+}
+
+/* note: this always recompute the csum on the whole skb, even
+ * if we just appended a single frag. More status info needed
+ */
+static void mptcp_update_data_checksum(struct sk_buff *skb, int added)
+{
+	struct mptcp_ext *mpext = mptcp_get_ext(skb);
+	__wsum csum = ~csum_unfold(mpext->csum);
+	int offset = skb->len - added;
+
+	mpext->csum = csum_fold(csum_block_add(csum, skb_checksum(skb, offset, added, 0), offset));
+}
+
+static void mptcp_update_infinite_map(struct mptcp_sock *msk,
+				      struct sock *ssk,
+				      struct mptcp_ext *mpext)
+{
+	if (!mpext)
+		return;
+
+	mpext->infinite_map = 1;
+	mpext->data_len = 0;
+
+	if (!mptcp_try_fallback(ssk, MPTCP_MIB_INFINITEMAPTX)) {
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_FALLBACKFAILED);
+		mptcp_subflow_reset(ssk);
+		return;
+	}
+
+	mptcp_subflow_ctx(ssk)->send_infinite_map = 0;
+}
+
+#define MPTCP_MAX_GSO_SIZE (GSO_LEGACY_MAX_SIZE - (MAX_TCP_HEADER + 1))
+
+static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
+			      struct mptcp_data_frag *dfrag,
+			      struct mptcp_sendmsg_info *info)
+{
+	u64 data_seq = dfrag->data_seq + info->sent;
+	int offset = dfrag->offset + info->sent;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool zero_window_probe = false;
+	struct mptcp_ext *mpext = NULL;
+	bool can_coalesce = false;
+	bool reuse_skb = true;
+	struct sk_buff *skb;
+	size_t copy;
+	int i;
+
+	pr_debug("msk=%p ssk=%p sending dfrag at seq=%llu len=%u already sent=%u\n",
+		 msk, ssk, dfrag->data_seq, dfrag->data_len, info->sent);
+
+	if (WARN_ON_ONCE(info->sent > info->limit ||
+			 info->limit > dfrag->data_len))
+		return 0;
+
+	if (unlikely(!__tcp_can_send(ssk)))
+		return -EAGAIN;
+
+	/* compute send limit */
+	if (unlikely(ssk->sk_gso_max_size > MPTCP_MAX_GSO_SIZE))
+		ssk->sk_gso_max_size = MPTCP_MAX_GSO_SIZE;
+	info->mss_now = tcp_send_mss(ssk, &info->size_goal, info->flags);
+	copy = info->size_goal;
+
+	skb = tcp_write_queue_tail(ssk);
+	if (skb && copy > skb->len) {
+		/* Limit the write to the size available in the
+		 * current skb, if any, so that we create at most a new skb.
+		 * Explicitly tells TCP internals to avoid collapsing on later
+		 * queue management operation, to avoid breaking the ext <->
+		 * SSN association set here
+		 */
+		mpext = mptcp_get_ext(skb);
+		if (!mptcp_skb_can_collapse_to(data_seq, skb, mpext)) {
+			TCP_SKB_CB(skb)->eor = 1;
+			tcp_mark_push(tcp_sk(ssk), skb);
+			goto alloc_skb;
+		}
+
+		i = skb_shinfo(skb)->nr_frags;
+		can_coalesce = skb_can_coalesce(skb, i, dfrag->page, offset);
+		if (!can_coalesce && i >= READ_ONCE(net_hotdata.sysctl_max_skb_frags)) {
+			tcp_mark_push(tcp_sk(ssk), skb);
+			goto alloc_skb;
+		}
+
+		copy -= skb->len;
+	} else {
+alloc_skb:
+		skb = mptcp_alloc_tx_skb(sk, ssk, info->data_lock_held);
+		if (!skb)
+			return -ENOMEM;
+
+		i = skb_shinfo(skb)->nr_frags;
+		reuse_skb = false;
+		mpext = mptcp_get_ext(skb);
+	}
+
+	/* Zero window and all data acked? Probe. */
+	copy = mptcp_check_allowed_size(msk, ssk, data_seq, copy);
+	if (copy == 0) {
+		u64 snd_una = READ_ONCE(msk->snd_una);
+
+		/* No need for zero probe if there are any data pending
+		 * either at the msk or ssk level; skb is the current write
+		 * queue tail and can be empty at this point.
+		 */
+		if (snd_una != msk->snd_nxt || skb->len ||
+		    skb != tcp_send_head(ssk)) {
+			tcp_remove_empty_skb(ssk);
+			return 0;
+		}
+
+		zero_window_probe = true;
+		data_seq = snd_una - 1;
+		copy = 1;
+	}
+
+	copy = min_t(size_t, copy, info->limit - info->sent);
+	if (!sk_wmem_schedule(ssk, copy)) {
+		tcp_remove_empty_skb(ssk);
+		return -ENOMEM;
+	}
+
+	if (can_coalesce) {
+		skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
+	} else {
+		get_page(dfrag->page);
+		skb_fill_page_desc(skb, i, dfrag->page, offset, copy);
+	}
+
+	skb->len += copy;
+	skb->data_len += copy;
+	skb->truesize += copy;
+	sk_wmem_queued_add(ssk, copy);
+	sk_mem_charge(ssk, copy);
+	WRITE_ONCE(tcp_sk(ssk)->write_seq, tcp_sk(ssk)->write_seq + copy);
+	TCP_SKB_CB(skb)->end_seq += copy;
+	tcp_skb_pcount_set(skb, 0);
+
+	/* on skb reuse we just need to update the DSS len */
+	if (reuse_skb) {
+		TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
+		mpext->data_len += copy;
+		goto out;
+	}
+
+	memset(mpext, 0, sizeof(*mpext));
+	mpext->data_seq = data_seq;
+	mpext->subflow_seq = mptcp_subflow_ctx(ssk)->rel_write_seq;
+	mpext->data_len = copy;
+	mpext->use_map = 1;
+	mpext->dsn64 = 1;
+
+	pr_debug("data_seq=%llu subflow_seq=%u data_len=%u dsn64=%d\n",
+		 mpext->data_seq, mpext->subflow_seq, mpext->data_len,
+		 mpext->dsn64);
+
+	if (zero_window_probe) {
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_WINPROBE);
+		mptcp_subflow_ctx(ssk)->rel_write_seq += copy;
+		mpext->frozen = 1;
+		if (READ_ONCE(msk->csum_enabled))
+			mptcp_update_data_checksum(skb, copy);
+		tcp_push_pending_frames(ssk);
+		return 0;
+	}
+out:
+	if (READ_ONCE(msk->csum_enabled))
+		mptcp_update_data_checksum(skb, copy);
+	if (mptcp_subflow_ctx(ssk)->send_infinite_map)
+		mptcp_update_infinite_map(msk, ssk, mpext);
+	trace_mptcp_sendmsg_frag(mpext);
+	mptcp_subflow_ctx(ssk)->rel_write_seq += copy;
+
+	/* if this is the last chunk of a dfrag with MSG_EOR set,
+	 * mark the skb to prevent coalescing with subsequent data.
+	 */
+	if (dfrag->eor && info->sent + copy >= dfrag->data_len)
+		TCP_SKB_CB(skb)->eor = 1;
+
+	return copy;
+}
+
+#define MPTCP_SEND_BURST_SIZE		((1 << 16) - \
+					 sizeof(struct tcphdr) - \
+					 MAX_TCP_OPTION_SPACE - \
+					 sizeof(struct ipv6hdr) - \
+					 sizeof(struct frag_hdr))
+
+struct subflow_send_info {
+	struct sock *ssk;
+	u64 linger_time;
+};
+
+void mptcp_subflow_set_active(struct mptcp_subflow_context *subflow)
+{
+	if (!subflow->stale)
+		return;
+
+	subflow->stale = 0;
+	MPTCP_INC_STATS(sock_net(mptcp_subflow_tcp_sock(subflow)), MPTCP_MIB_SUBFLOWRECOVER);
+}
+
+bool mptcp_subflow_active(struct mptcp_subflow_context *subflow)
+{
+	if (unlikely(subflow->stale)) {
+		u32 rcv_tstamp = READ_ONCE(tcp_sk(mptcp_subflow_tcp_sock(subflow))->rcv_tstamp);
+
+		if (subflow->stale_rcv_tstamp == rcv_tstamp)
+			return false;
+
+		mptcp_subflow_set_active(subflow);
+	}
+	return __mptcp_subflow_active(subflow);
+}
+
+#define SSK_MODE_ACTIVE	0
+#define SSK_MODE_BACKUP	1
+#define SSK_MODE_MAX	2
+
+/* implement the mptcp packet scheduler;
+ * returns the subflow that will transmit the next DSS
+ * additionally updates the rtx timeout
+ */
+struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
+{
+	struct subflow_send_info send_info[SSK_MODE_MAX];
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	u32 pace, burst, wmem;
+	int i, nr_active = 0;
+	struct sock *ssk;
+	u64 linger_time;
+	long tout = 0;
+
+	/* pick the subflow with the lower wmem/wspace ratio */
+	for (i = 0; i < SSK_MODE_MAX; ++i) {
+		send_info[i].ssk = NULL;
+		send_info[i].linger_time = -1;
+	}
+
+	mptcp_for_each_subflow(msk, subflow) {
+		bool backup = subflow->backup || subflow->request_bkup;
+
+		trace_mptcp_subflow_get_send(subflow);
+		ssk =  mptcp_subflow_tcp_sock(subflow);
+		if (!mptcp_subflow_active(subflow))
+			continue;
+
+		tout = max(tout, mptcp_timeout_from_subflow(subflow));
+		nr_active += !backup;
+		pace = subflow->avg_pacing_rate;
+		if (unlikely(!pace)) {
+			/* init pacing rate from socket */
+			subflow->avg_pacing_rate = READ_ONCE(ssk->sk_pacing_rate);
+			pace = subflow->avg_pacing_rate;
+			if (!pace)
+				continue;
+		}
+
+		linger_time = div_u64((u64)READ_ONCE(ssk->sk_wmem_queued) << 32, pace);
+		if (linger_time < send_info[backup].linger_time) {
+			send_info[backup].ssk = ssk;
+			send_info[backup].linger_time = linger_time;
+		}
+	}
+	__mptcp_set_timeout(sk, tout);
+
+	/* pick the best backup if no other subflow is active */
+	if (!nr_active)
+		send_info[SSK_MODE_ACTIVE].ssk = send_info[SSK_MODE_BACKUP].ssk;
+
+	/* According to the blest algorithm, to avoid HoL blocking for the
+	 * faster flow, we need to:
+	 * - estimate the faster flow linger time
+	 * - use the above to estimate the amount of byte transferred
+	 *   by the faster flow
+	 * - check that the amount of queued data is greater than the above,
+	 *   otherwise do not use the picked, slower, subflow
+	 * We select the subflow with the shorter estimated time to flush
+	 * the queued mem, which basically ensure the above. We just need
+	 * to check that subflow has a non empty cwin.
+	 */
+	ssk = send_info[SSK_MODE_ACTIVE].ssk;
+	if (!ssk || !sk_stream_memory_free(ssk))
+		return NULL;
+
+	burst = min(MPTCP_SEND_BURST_SIZE, mptcp_wnd_end(msk) - msk->snd_nxt);
+	wmem = READ_ONCE(ssk->sk_wmem_queued);
+	if (!burst)
+		return ssk;
+
+	subflow = mptcp_subflow_ctx(ssk);
+	subflow->avg_pacing_rate = div_u64((u64)subflow->avg_pacing_rate * wmem +
+					   READ_ONCE(ssk->sk_pacing_rate) * burst,
+					   burst + wmem);
+	msk->snd_burst = burst;
+	return ssk;
+}
+
+static void mptcp_push_release(struct sock *ssk, struct mptcp_sendmsg_info *info)
+{
+	tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle, info->size_goal);
+	release_sock(ssk);
+}
+
+static void mptcp_update_post_push(struct mptcp_sock *msk,
+				   struct mptcp_data_frag *dfrag,
+				   u32 sent)
+{
+	u64 snd_nxt_new = dfrag->data_seq;
+
+	dfrag->already_sent += sent;
+
+	msk->snd_burst -= sent;
+
+	snd_nxt_new += dfrag->already_sent;
+
+	/* snd_nxt_new can be smaller than snd_nxt in case mptcp
+	 * is recovering after a failover. In that event, this re-sends
+	 * old segments.
+	 *
+	 * Thus compute snd_nxt_new candidate based on
+	 * the dfrag->data_seq that was sent and the data
+	 * that has been handed to the subflow for transmission
+	 * and skip update in case it was old dfrag.
+	 */
+	if (likely(after64(snd_nxt_new, msk->snd_nxt))) {
+		msk->bytes_sent += snd_nxt_new - msk->snd_nxt;
+		WRITE_ONCE(msk->snd_nxt, snd_nxt_new);
+	}
+}
+
+void mptcp_check_and_set_pending(struct sock *sk)
+{
+	if (mptcp_send_head(sk)) {
+		mptcp_data_lock(sk);
+		mptcp_sk(sk)->cb_flags |= BIT(MPTCP_PUSH_PENDING);
+		mptcp_data_unlock(sk);
+	}
+}
+
+static int __subflow_push_pending(struct sock *sk, struct sock *ssk,
+				  struct mptcp_sendmsg_info *info)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_data_frag *dfrag;
+	int len, copied = 0, err = 0;
+
+	while ((dfrag = mptcp_send_head(sk))) {
+		info->sent = dfrag->already_sent;
+		info->limit = dfrag->data_len;
+		len = dfrag->data_len - dfrag->already_sent;
+		while (len > 0) {
+			int ret = 0;
+
+			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, info);
+			if (ret <= 0) {
+				err = copied ? : ret;
+				goto out;
+			}
+
+			info->sent += ret;
+			copied += ret;
+			len -= ret;
+
+			mptcp_update_post_push(msk, dfrag, ret);
+		}
+		msk->first_pending = mptcp_send_next(sk);
+
+		if (msk->snd_burst <= 0 ||
+		    !sk_stream_memory_free(ssk) ||
+		    !mptcp_subflow_active(mptcp_subflow_ctx(ssk))) {
+			err = copied;
+			goto out;
+		}
+		mptcp_set_timeout(sk);
+	}
+	err = copied;
+
+out:
+	if (err > 0)
+		msk->last_data_sent = tcp_jiffies32;
+	return err;
+}
+
+void __mptcp_push_pending(struct sock *sk, unsigned int flags)
+{
+	struct sock *prev_ssk = NULL, *ssk = NULL;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_sendmsg_info info = {
+				.flags = flags,
+	};
+	bool copied = false;
+	int push_count = 1;
+
+	while (mptcp_send_head(sk) && (push_count > 0)) {
+		struct mptcp_subflow_context *subflow;
+		int ret = 0;
+
+		if (mptcp_sched_get_send(msk))
+			break;
+
+		push_count = 0;
+
+		mptcp_for_each_subflow(msk, subflow) {
+			if (READ_ONCE(subflow->scheduled)) {
+				mptcp_subflow_set_scheduled(subflow, false);
+
+				prev_ssk = ssk;
+				ssk = mptcp_subflow_tcp_sock(subflow);
+				if (ssk != prev_ssk) {
+					/* First check. If the ssk has changed since
+					 * the last round, release prev_ssk
+					 */
+					if (prev_ssk)
+						mptcp_push_release(prev_ssk, &info);
+
+					/* Need to lock the new subflow only if different
+					 * from the previous one, otherwise we are still
+					 * helding the relevant lock
+					 */
+					lock_sock(ssk);
+				}
+
+				push_count++;
+
+				ret = __subflow_push_pending(sk, ssk, &info);
+				if (ret <= 0) {
+					if (ret != -EAGAIN ||
+					    (1 << ssk->sk_state) &
+					     (TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | TCPF_CLOSE))
+						push_count--;
+					continue;
+				}
+				copied = true;
+			}
+		}
+	}
+
+	/* at this point we held the socket lock for the last subflow we used */
+	if (ssk)
+		mptcp_push_release(ssk, &info);
+
+	/* Avoid scheduling the rtx timer if no data has been pushed; the timer
+	 * will be updated on positive acks by __mptcp_cleanup_una().
+	 */
+	if (copied) {
+		if (!mptcp_rtx_timer_pending(sk))
+			mptcp_reset_rtx_timer(sk);
+		mptcp_check_send_data_fin(sk);
+	}
+}
+
+static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool first)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_sendmsg_info info = {
+		.data_lock_held = true,
+	};
+	bool keep_pushing = true;
+	struct sock *xmit_ssk;
+	int copied = 0;
+
+	info.flags = 0;
+	while (mptcp_send_head(sk) && keep_pushing) {
+		struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+		int ret = 0;
+
+		/* check for a different subflow usage only after
+		 * spooling the first chunk of data
+		 */
+		if (first) {
+			mptcp_subflow_set_scheduled(subflow, false);
+			ret = __subflow_push_pending(sk, ssk, &info);
+			first = false;
+			if (ret <= 0)
+				break;
+			copied += ret;
+			continue;
+		}
+
+		if (mptcp_sched_get_send(msk))
+			goto out;
+
+		if (READ_ONCE(subflow->scheduled)) {
+			mptcp_subflow_set_scheduled(subflow, false);
+			ret = __subflow_push_pending(sk, ssk, &info);
+			if (ret <= 0)
+				keep_pushing = false;
+			copied += ret;
+		}
+
+		mptcp_for_each_subflow(msk, subflow) {
+			if (READ_ONCE(subflow->scheduled)) {
+				xmit_ssk = mptcp_subflow_tcp_sock(subflow);
+				if (xmit_ssk != ssk) {
+					mptcp_subflow_delegate(subflow,
+							       MPTCP_DELEGATE_SEND);
+					keep_pushing = false;
+				}
+			}
+		}
+	}
+
+out:
+	/* __mptcp_alloc_tx_skb could have released some wmem and we are
+	 * not going to flush it via release_sock()
+	 */
+	if (copied) {
+		tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
+			 info.size_goal);
+		if (!mptcp_rtx_timer_pending(sk))
+			mptcp_reset_rtx_timer(sk);
+
+		if (msk->snd_data_fin_enable &&
+		    msk->snd_nxt + 1 == msk->write_seq)
+			mptcp_schedule_work(sk);
+	}
+}
+
+static int mptcp_disconnect(struct sock *sk, int flags);
+
+static int mptcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
+				  size_t len, int *copied_syn)
+{
+	unsigned int saved_flags = msg->msg_flags;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sock *ssk;
+	int ret;
+
+	/* on flags based fastopen the mptcp is supposed to create the
+	 * first subflow right now. Otherwise we are in the defer_connect
+	 * path, and the first subflow must be already present.
+	 * Since the defer_connect flag is cleared after the first succsful
+	 * fastopen attempt, no need to check for additional subflow status.
+	 */
+	if (msg->msg_flags & MSG_FASTOPEN) {
+		ssk = __mptcp_nmpc_sk(msk);
+		if (IS_ERR(ssk))
+			return PTR_ERR(ssk);
+	}
+	if (!msk->first)
+		return -EINVAL;
+
+	ssk = msk->first;
+
+	lock_sock(ssk);
+	msg->msg_flags |= MSG_DONTWAIT;
+	msk->fastopening = 1;
+	ret = tcp_sendmsg_fastopen(ssk, msg, copied_syn, len, NULL);
+	msk->fastopening = 0;
+	msg->msg_flags = saved_flags;
+	release_sock(ssk);
+
+	/* do the blocking bits of inet_stream_connect outside the ssk socket lock */
+	if (ret == -EINPROGRESS && !(msg->msg_flags & MSG_DONTWAIT)) {
+		ret = __inet_stream_connect(sk->sk_socket, msg->msg_name,
+					    msg->msg_namelen, msg->msg_flags, 1);
+
+		/* Keep the same behaviour of plain TCP: zero the copied bytes in
+		 * case of any error, except timeout or signal
+		 */
+		if (ret && ret != -EINPROGRESS && ret != -ERESTARTSYS && ret != -EINTR)
+			*copied_syn = 0;
+	} else if (ret && ret != -EINPROGRESS) {
+		/* The disconnect() op called by tcp_sendmsg_fastopen()/
+		 * __inet_stream_connect() can fail, due to looking check,
+		 * see mptcp_disconnect().
+		 * Attempt it again outside the problematic scope.
+		 */
+		if (!mptcp_disconnect(sk, 0)) {
+			sk->sk_disconnects++;
+			sk->sk_socket->state = SS_UNCONNECTED;
+		}
+	}
+	inet_clear_bit(DEFER_CONNECT, sk);
+
+	return ret;
+}
+
+static int do_copy_data_nocache(struct sock *sk, int copy,
+				struct iov_iter *from, char *to)
+{
+	if (sk->sk_route_caps & NETIF_F_NOCACHE_COPY) {
+		if (!copy_from_iter_full_nocache(to, copy, from))
+			return -EFAULT;
+	} else if (!copy_from_iter_full(to, copy, from)) {
+		return -EFAULT;
+	}
+	return 0;
+}
+
+/* open-code sk_stream_memory_free() plus sent limit computation to
+ * avoid indirect calls in fast-path.
+ * Called under the msk socket lock, so we can avoid a bunch of ONCE
+ * annotations.
+ */
+static u32 mptcp_send_limit(const struct sock *sk)
+{
+	const struct mptcp_sock *msk = mptcp_sk(sk);
+	u32 limit, not_sent;
+
+	if (sk->sk_wmem_queued >= READ_ONCE(sk->sk_sndbuf))
+		return 0;
+
+	limit = mptcp_notsent_lowat(sk);
+	if (limit == UINT_MAX)
+		return UINT_MAX;
+
+	not_sent = msk->write_seq - msk->snd_nxt;
+	if (not_sent >= limit)
+		return 0;
+
+	return limit - not_sent;
+}
+
+static void mptcp_rps_record_subflows(const struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+
+	if (!rfs_is_needed())
+		return;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		sock_rps_record_flow(ssk);
+	}
+}
+
+static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct page_frag *pfrag;
+	size_t copied = 0;
+	int ret = 0;
+	long timeo;
+
+	/* silently ignore everything else */
+	msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL |
+			  MSG_FASTOPEN | MSG_EOR;
+
+	lock_sock(sk);
+
+	mptcp_rps_record_subflows(msk);
+
+	if (unlikely(inet_test_bit(DEFER_CONNECT, sk) ||
+		     msg->msg_flags & MSG_FASTOPEN)) {
+		int copied_syn = 0;
+
+		ret = mptcp_sendmsg_fastopen(sk, msg, len, &copied_syn);
+		copied += copied_syn;
+		if (ret == -EINPROGRESS && copied_syn > 0)
+			goto out;
+		else if (ret)
+			goto do_error;
+	}
+
+	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
+
+	if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
+		ret = sk_stream_wait_connect(sk, &timeo);
+		if (ret)
+			goto do_error;
+	}
+
+	ret = -EPIPE;
+	if (unlikely(sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)))
+		goto do_error;
+
+	pfrag = sk_page_frag(sk);
+
+	while (msg_data_left(msg)) {
+		int total_ts, frag_truesize = 0;
+		struct mptcp_data_frag *dfrag;
+		bool dfrag_collapsed;
+		size_t psize, offset;
+		u32 copy_limit;
+
+		/* ensure fitting the notsent_lowat() constraint */
+		copy_limit = mptcp_send_limit(sk);
+		if (!copy_limit)
+			goto wait_for_memory;
+
+		/* reuse tail pfrag, if possible, or carve a new one from the
+		 * page allocator
+		 */
+		dfrag = mptcp_pending_tail(sk);
+		dfrag_collapsed = mptcp_frag_can_collapse_to(msk, pfrag, dfrag);
+		if (!dfrag_collapsed) {
+			if (!mptcp_page_frag_refill(sk, pfrag))
+				goto wait_for_memory;
+
+			dfrag = mptcp_carve_data_frag(msk, pfrag, pfrag->offset);
+			frag_truesize = dfrag->overhead;
+		}
+
+		/* we do not bound vs wspace, to allow a single packet.
+		 * memory accounting will prevent execessive memory usage
+		 * anyway
+		 */
+		offset = dfrag->offset + dfrag->data_len;
+		psize = pfrag->size - offset;
+		psize = min_t(size_t, psize, msg_data_left(msg));
+		psize = min_t(size_t, psize, copy_limit);
+		total_ts = psize + frag_truesize;
+
+		if (!sk_wmem_schedule(sk, total_ts))
+			goto wait_for_memory;
+
+		ret = do_copy_data_nocache(sk, psize, &msg->msg_iter,
+					   page_address(dfrag->page) + offset);
+		if (ret)
+			goto do_error;
+
+		/* data successfully copied into the write queue */
+		sk_forward_alloc_add(sk, -total_ts);
+		copied += psize;
+		dfrag->data_len += psize;
+		frag_truesize += psize;
+		pfrag->offset += frag_truesize;
+		WRITE_ONCE(msk->write_seq, msk->write_seq + psize);
+
+		/* charge data on mptcp pending queue to the msk socket
+		 * Note: we charge such data both to sk and ssk
+		 */
+		sk_wmem_queued_add(sk, frag_truesize);
+		if (!dfrag_collapsed) {
+			get_page(dfrag->page);
+			list_add_tail(&dfrag->list, &msk->rtx_queue);
+			if (!msk->first_pending)
+				msk->first_pending = dfrag;
+		}
+		pr_debug("msk=%p dfrag at seq=%llu len=%u sent=%u new=%d\n", msk,
+			 dfrag->data_seq, dfrag->data_len, dfrag->already_sent,
+			 !dfrag_collapsed);
+
+		continue;
+
+wait_for_memory:
+		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+		__mptcp_push_pending(sk, msg->msg_flags);
+		ret = sk_stream_wait_memory(sk, &timeo);
+		if (ret)
+			goto do_error;
+	}
+
+	if (copied) {
+		/* mark the last dfrag with EOR if MSG_EOR was set */
+		if (msg->msg_flags & MSG_EOR) {
+			struct mptcp_data_frag *dfrag = mptcp_pending_tail(sk);
+
+			if (dfrag)
+				dfrag->eor = 1;
+		}
+		__mptcp_push_pending(sk, msg->msg_flags);
+	}
+
+out:
+	release_sock(sk);
+	return copied;
+
+do_error:
+	if (copied)
+		goto out;
+
+	copied = sk_stream_error(sk, msg->msg_flags, ret);
+	goto out;
+}
+
+static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied);
+
+static void mptcp_eat_recv_skb(struct sock *sk, struct sk_buff *skb)
+{
+	/* avoid the indirect call, we know the destructor is sock_rfree */
+	skb->destructor = NULL;
+	skb->sk = NULL;
+	atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
+	sk_mem_uncharge(sk, skb->truesize);
+	__skb_unlink(skb, &sk->sk_receive_queue);
+	skb_attempt_defer_free(skb);
+}
+
+static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg,
+				size_t len, int flags, int copied_total,
+				struct scm_timestamping_internal *tss,
+				int *cmsg_flags, struct sk_buff **last)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *skb, *tmp;
+	int total_data_len = 0;
+	int copied = 0;
+
+	skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp) {
+		u32 delta, offset = MPTCP_SKB_CB(skb)->offset;
+		u32 data_len = skb->len - offset;
+		u32 count;
+		int err;
+
+		if (flags & MSG_PEEK) {
+			/* skip already peeked skbs */
+			if (total_data_len + data_len <= copied_total) {
+				total_data_len += data_len;
+				*last = skb;
+				continue;
+			}
+
+			/* skip the already peeked data in the current skb */
+			delta = copied_total - total_data_len;
+			offset += delta;
+			data_len -= delta;
+		}
+
+		count = min_t(size_t, len - copied, data_len);
+		if (!(flags & MSG_TRUNC)) {
+			err = skb_copy_datagram_msg(skb, offset, msg, count);
+			if (unlikely(err < 0)) {
+				if (!copied)
+					return err;
+				break;
+			}
+		}
+
+		if (MPTCP_SKB_CB(skb)->has_rxtstamp) {
+			tcp_update_recv_tstamps(skb, tss);
+			*cmsg_flags |= MPTCP_CMSG_TS;
+		}
+
+		copied += count;
+
+		if (!(flags & MSG_PEEK)) {
+			msk->bytes_consumed += count;
+			if (count < data_len) {
+				MPTCP_SKB_CB(skb)->offset += count;
+				MPTCP_SKB_CB(skb)->map_seq += count;
+				break;
+			}
+
+			mptcp_eat_recv_skb(sk, skb);
+		} else {
+			*last = skb;
+		}
+
+		if (copied >= len)
+			break;
+	}
+
+	mptcp_rcv_space_adjust(msk, copied);
+	return copied;
+}
+
+static void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
+{
+	const struct tcp_sock *tp = tcp_sk(ssk);
+
+	msk->rcvspace_init = 1;
+	msk->rcvq_space.copied = 0;
+
+	/* initial rcv_space offering made to peer */
+	msk->rcvq_space.space = min_t(u32, tp->rcv_wnd,
+				      TCP_INIT_CWND * tp->advmss);
+	if (msk->rcvq_space.space == 0)
+		msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT;
+}
+
+/* receive buffer autotuning.  See tcp_rcv_space_adjust for more information.
+ *
+ * Only difference: Use lowest rtt estimate of the subflows in use, see
+ * mptcp_rcv_rtt_update() and mptcp_rtt_us_est().
+ */
+static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	u32 time, rtt_us;
+	u64 mstamp;
+
+	msk_owned_by_me(msk);
+
+	if (copied <= 0)
+		return;
+
+	if (!msk->rcvspace_init)
+		mptcp_rcv_space_init(msk, msk->first);
+
+	msk->rcvq_space.copied += copied;
+
+	mstamp = mptcp_stamp();
+	time = tcp_stamp_us_delta(mstamp, READ_ONCE(msk->rcvq_space.time));
+
+	rtt_us = mptcp_rtt_us_est(msk);
+	if (rtt_us == U32_MAX || time < (rtt_us >> 3))
+		return;
+
+	copied = msk->rcvq_space.copied;
+	copied -= mptcp_inq_hint(sk);
+	if (copied <= msk->rcvq_space.space)
+		goto new_measure;
+
+	trace_mptcp_rcvbuf_grow(sk, time);
+	if (mptcp_rcvbuf_grow(sk, copied)) {
+		/* Make subflows follow along.  If we do not do this, we
+		 * get drops at subflow level if skbs can't be moved to
+		 * the mptcp rx queue fast enough (announced rcv_win can
+		 * exceed ssk->sk_rcvbuf).
+		 */
+		mptcp_for_each_subflow(msk, subflow) {
+			struct sock *ssk;
+			bool slow;
+
+			ssk = mptcp_subflow_tcp_sock(subflow);
+			slow = lock_sock_fast(ssk);
+			/* subflows can be added before tcp_init_transfer() */
+			if (tcp_sk(ssk)->rcvq_space.space)
+				tcp_rcvbuf_grow(ssk, copied);
+			unlock_sock_fast(ssk, slow);
+		}
+	}
+
+new_measure:
+	msk->rcvq_space.copied = 0;
+	msk->rcvq_space.time = mstamp;
+}
+
+static bool __mptcp_move_skbs(struct sock *sk, struct list_head *skbs, u32 *delta)
+{
+	struct sk_buff *skb = list_first_entry(skbs, struct sk_buff, list);
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool moved = false;
+
+	while (1) {
+		prefetch(skb->next);
+		list_del(&skb->list);
+		*delta += skb->truesize;
+
+		moved |= __mptcp_move_skb(sk, skb);
+		if (list_empty(skbs))
+			break;
+
+		skb = list_first_entry(skbs, struct sk_buff, list);
+	}
+
+	__mptcp_ofo_queue(msk);
+	if (moved)
+		mptcp_check_data_fin((struct sock *)msk);
+	return moved;
+}
+
+static bool mptcp_can_spool_backlog(struct sock *sk, struct list_head *skbs)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	/* After CG initialization, subflows should never add skb before
+	 * gaining the CG themself.
+	 */
+	DEBUG_NET_WARN_ON_ONCE(msk->backlog_unaccounted && sk->sk_socket &&
+			       mem_cgroup_from_sk(sk));
+
+	if (list_empty(&msk->backlog_list))
+		return false;
+
+	INIT_LIST_HEAD(skbs);
+	list_splice_init(&msk->backlog_list, skbs);
+	return true;
+}
+
+static bool mptcp_move_skbs(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct list_head skbs;
+	bool enqueued = false;
+	u32 moved = 0;
+
+	mptcp_data_lock(sk);
+	while (mptcp_can_spool_backlog(sk, &skbs)) {
+		mptcp_data_unlock(sk);
+		enqueued |= __mptcp_move_skbs(sk, &skbs, &moved);
+
+		mptcp_data_lock(sk);
+	}
+	WRITE_ONCE(msk->backlog_len, msk->backlog_len - moved);
+	mptcp_data_unlock(sk);
+
+	if (enqueued && mptcp_epollin_ready(sk))
+		sk->sk_data_ready(sk);
+
+	return enqueued;
+}
+
+static unsigned int mptcp_inq_hint(const struct sock *sk)
+{
+	const struct mptcp_sock *msk = mptcp_sk(sk);
+	const struct sk_buff *skb;
+
+	skb = skb_peek(&sk->sk_receive_queue);
+	if (skb) {
+		u64 hint_val = READ_ONCE(msk->ack_seq) - MPTCP_SKB_CB(skb)->map_seq;
+
+		if (hint_val >= INT_MAX)
+			return INT_MAX;
+
+		return (unsigned int)hint_val;
+	}
+
+	if (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN))
+		return 1;
+
+	return 0;
+}
+
+static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
+			 int flags)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct scm_timestamping_internal tss;
+	int copied = 0, cmsg_flags = 0;
+	int target;
+	long timeo;
+
+	/* MSG_ERRQUEUE is really a no-op till we support IP_RECVERR */
+	if (unlikely(flags & MSG_ERRQUEUE))
+		return inet_recv_error(sk, msg, len);
+
+	lock_sock(sk);
+	if (unlikely(sk->sk_state == TCP_LISTEN)) {
+		copied = -ENOTCONN;
+		goto out_err;
+	}
+
+	mptcp_rps_record_subflows(msk);
+
+	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
+
+	len = min_t(size_t, len, INT_MAX);
+	target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
+
+	if (unlikely(msk->recvmsg_inq))
+		cmsg_flags = MPTCP_CMSG_INQ;
+
+	while (copied < len) {
+		struct sk_buff *last = NULL;
+		int err, bytes_read;
+
+		bytes_read = __mptcp_recvmsg_mskq(sk, msg, len - copied, flags,
+						  copied, &tss, &cmsg_flags,
+						  &last);
+		if (unlikely(bytes_read < 0)) {
+			if (!copied)
+				copied = bytes_read;
+			goto out_err;
+		}
+
+		copied += bytes_read;
+
+		if (!list_empty(&msk->backlog_list) && mptcp_move_skbs(sk))
+			continue;
+
+		/* only the MPTCP socket status is relevant here. The exit
+		 * conditions mirror closely tcp_recvmsg()
+		 */
+		if (copied >= target)
+			break;
+
+		if (copied) {
+			if (tcp_recv_should_stop(sk) ||
+			    !timeo)
+				break;
+		} else {
+			if (sk->sk_err) {
+				copied = sock_error(sk);
+				break;
+			}
+
+			if (sk->sk_shutdown & RCV_SHUTDOWN)
+				break;
+
+			if (sk->sk_state == TCP_CLOSE) {
+				copied = -ENOTCONN;
+				break;
+			}
+
+			if (!timeo) {
+				copied = -EAGAIN;
+				break;
+			}
+
+			if (signal_pending(current)) {
+				copied = sock_intr_errno(timeo);
+				break;
+			}
+		}
+
+		pr_debug("block timeout %ld\n", timeo);
+		mptcp_cleanup_rbuf(msk, copied);
+		err = sk_wait_data(sk, &timeo, last);
+		if (err < 0) {
+			err = copied ? : err;
+			goto out_err;
+		}
+	}
+
+	mptcp_cleanup_rbuf(msk, copied);
+
+out_err:
+	if (cmsg_flags && copied >= 0) {
+		if (cmsg_flags & MPTCP_CMSG_TS)
+			tcp_recv_timestamp(msg, sk, &tss);
+
+		if (cmsg_flags & MPTCP_CMSG_INQ) {
+			unsigned int inq = mptcp_inq_hint(sk);
+
+			put_cmsg(msg, SOL_TCP, TCP_CM_INQ, sizeof(inq), &inq);
+		}
+	}
+
+	pr_debug("msk=%p rx queue empty=%d copied=%d\n",
+		 msk, skb_queue_empty(&sk->sk_receive_queue), copied);
+
+	release_sock(sk);
+	return copied;
+}
+
+static void mptcp_retransmit_timer(struct timer_list *t)
+{
+	struct sock *sk = timer_container_of(sk, t, mptcp_retransmit_timer);
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	bh_lock_sock(sk);
+	if (!sock_owned_by_user(sk)) {
+		/* we need a process context to retransmit */
+		if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
+			mptcp_schedule_work(sk);
+	} else {
+		/* delegate our work to tcp_release_cb() */
+		__set_bit(MPTCP_RETRANSMIT, &msk->cb_flags);
+	}
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+static void mptcp_tout_timer(struct timer_list *t)
+{
+	struct inet_connection_sock *icsk =
+		timer_container_of(icsk, t, mptcp_tout_timer);
+	struct sock *sk = &icsk->icsk_inet.sk;
+
+	mptcp_schedule_work(sk);
+	sock_put(sk);
+}
+
+/* Find an idle subflow.  Return NULL if there is unacked data at tcp
+ * level.
+ *
+ * A backup subflow is returned only if that is the only kind available.
+ */
+struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
+{
+	struct sock *backup = NULL, *pick = NULL;
+	struct mptcp_subflow_context *subflow;
+	int min_stale_count = INT_MAX;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (!__mptcp_subflow_active(subflow))
+			continue;
+
+		/* still data outstanding at TCP level? skip this */
+		if (!tcp_rtx_and_write_queues_empty(ssk)) {
+			min_stale_count = min_t(int, min_stale_count, subflow->stale_count);
+			continue;
+		}
+
+		if (subflow->backup || subflow->request_bkup) {
+			if (!backup)
+				backup = ssk;
+			continue;
+		}
+
+		if (!pick)
+			pick = ssk;
+	}
+
+	if (pick)
+		return pick;
+
+	/* use backup only if there are no progresses anywhere */
+	return min_stale_count > 1 ? backup : NULL;
+}
+
+bool __mptcp_retransmit_pending_data(struct sock *sk)
+{
+	struct mptcp_data_frag *cur, *rtx_head;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (__mptcp_check_fallback(msk))
+		return false;
+
+	/* the closing socket has some data untransmitted and/or unacked:
+	 * some data in the mptcp rtx queue has not really xmitted yet.
+	 * keep it simple and re-inject the whole mptcp level rtx queue
+	 */
+	mptcp_data_lock(sk);
+	__mptcp_clean_una_wakeup(sk);
+	rtx_head = mptcp_rtx_head(sk);
+	if (!rtx_head) {
+		mptcp_data_unlock(sk);
+		return false;
+	}
+
+	msk->recovery_snd_nxt = msk->snd_nxt;
+	msk->recovery = true;
+	mptcp_data_unlock(sk);
+
+	msk->first_pending = rtx_head;
+	msk->snd_burst = 0;
+
+	/* be sure to clear the "sent status" on all re-injected fragments */
+	list_for_each_entry(cur, &msk->rtx_queue, list) {
+		if (!cur->already_sent)
+			break;
+		cur->already_sent = 0;
+	}
+
+	return true;
+}
+
+/* flags for __mptcp_close_ssk() */
+#define MPTCP_CF_PUSH		BIT(1)
+
+/* be sure to send a reset only if the caller asked for it, also
+ * clean completely the subflow status when the subflow reaches
+ * TCP_CLOSE state
+ */
+static void __mptcp_subflow_disconnect(struct sock *ssk,
+				       struct mptcp_subflow_context *subflow,
+				       bool fastclosing)
+{
+	if (((1 << ssk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
+	    fastclosing) {
+		/* The MPTCP code never wait on the subflow sockets, TCP-level
+		 * disconnect should never fail
+		 */
+		WARN_ON_ONCE(tcp_disconnect(ssk, 0));
+		mptcp_subflow_ctx_reset(subflow);
+	} else {
+		tcp_shutdown(ssk, SEND_SHUTDOWN);
+	}
+}
+
+static void mptcp_cleanup_ssk_backlog(struct sock *sk, struct sock *ssk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *skb;
+
+	mptcp_data_lock(sk);
+	list_for_each_entry(skb, &msk->backlog_list, list) {
+		if (skb->sk != ssk)
+			continue;
+
+		atomic_sub(skb->truesize, &skb->sk->sk_rmem_alloc);
+		skb->sk = NULL;
+	}
+	mptcp_data_unlock(sk);
+}
+
+/* subflow sockets can be either outgoing (connect) or incoming
+ * (accept).
+ *
+ * Outgoing subflows use in-kernel sockets.
+ * Incoming subflows do not have their own 'struct socket' allocated,
+ * so we need to use tcp_close() after detaching them from the mptcp
+ * parent socket.
+ */
+static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
+			      struct mptcp_subflow_context *subflow,
+			      unsigned int flags)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool dispose_it, need_push = false;
+	int fwd_remaining;
+
+	/* Do not pass RX data to the msk, even if the subflow socket is not
+	 * going to be freed (i.e. even for the first subflow on graceful
+	 * subflow close.
+	 */
+	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
+	subflow->closing = 1;
+
+	if (flags & MPTCP_CF_PUSH)
+		mptcp_cleanup_ssk_backlog(sk, ssk);
+
+	/* Borrow the fwd allocated page left-over; fwd memory for the subflow
+	 * could be negative at this point, but will be reach zero soon - when
+	 * the data allocated using such fragment will be freed.
+	 */
+	if (subflow->lent_mem_frag) {
+		fwd_remaining = PAGE_SIZE - subflow->lent_mem_frag;
+		sk_forward_alloc_add(sk, fwd_remaining);
+		sk_forward_alloc_add(ssk, -fwd_remaining);
+		subflow->lent_mem_frag = 0;
+	}
+
+	/* If the first subflow moved to a close state before accept, e.g. due
+	 * to an incoming reset or listener shutdown, the subflow socket is
+	 * already deleted by inet_child_forget() and the mptcp socket can't
+	 * survive too.
+	 */
+	if (msk->in_accept_queue && msk->first == ssk &&
+	    (sock_flag(sk, SOCK_DEAD) || sock_flag(ssk, SOCK_DEAD))) {
+		/* ensure later check in mptcp_worker() will dispose the msk */
+		sock_set_flag(sk, SOCK_DEAD);
+		mptcp_set_close_tout(sk, tcp_jiffies32 - (mptcp_close_timeout(sk) + 1));
+		mptcp_subflow_drop_ctx(ssk);
+		goto out_release;
+	}
+
+	dispose_it = msk->free_first || ssk != msk->first;
+	if (dispose_it)
+		list_del(&subflow->node);
+
+	if (subflow->send_fastclose && ssk->sk_state != TCP_CLOSE)
+		tcp_set_state(ssk, TCP_CLOSE);
+
+	need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
+	if (!dispose_it) {
+		__mptcp_subflow_disconnect(ssk, subflow, msk->fastclosing);
+		release_sock(ssk);
+
+		goto out;
+	}
+
+	subflow->disposable = 1;
+
+	/* if ssk hit tcp_done(), tcp_cleanup_ulp() cleared the related ops
+	 * the ssk has been already destroyed, we just need to release the
+	 * reference owned by msk;
+	 */
+	if (!inet_csk(ssk)->icsk_ulp_ops) {
+		WARN_ON_ONCE(!sock_flag(ssk, SOCK_DEAD));
+		kfree_rcu(subflow, rcu);
+	} else {
+		/* otherwise tcp will dispose of the ssk and subflow ctx */
+		__tcp_close(ssk, 0);
+
+		/* close acquired an extra ref */
+		__sock_put(ssk);
+	}
+
+out_release:
+	__mptcp_subflow_error_report(sk, ssk);
+	release_sock(ssk);
+
+	sock_put(ssk);
+
+	if (ssk == msk->first)
+		WRITE_ONCE(msk->first, NULL);
+
+out:
+	__mptcp_sync_sndbuf(sk);
+	if (need_push)
+		__mptcp_push_pending(sk, 0);
+
+	/* Catch every 'all subflows closed' scenario, including peers silently
+	 * closing them, e.g. due to timeout.
+	 * For established sockets, allow an additional timeout before closing,
+	 * as the protocol can still create more subflows.
+	 */
+	if (list_is_singular(&msk->conn_list) && msk->first &&
+	    inet_sk_state_load(msk->first) == TCP_CLOSE) {
+		if (sk->sk_state != TCP_ESTABLISHED ||
+		    msk->in_accept_queue || sock_flag(sk, SOCK_DEAD)) {
+			mptcp_set_state(sk, TCP_CLOSE);
+			mptcp_close_wake_up(sk);
+		} else {
+			mptcp_start_tout_timer(sk);
+		}
+	}
+}
+
+void mptcp_close_ssk(struct sock *sk, struct sock *ssk,
+		     struct mptcp_subflow_context *subflow)
+{
+	/* The first subflow can already be closed or disconnected */
+	if (subflow->close_event_done || READ_ONCE(subflow->local_id) < 0)
+		return;
+
+	subflow->close_event_done = true;
+
+	if (sk->sk_state == TCP_ESTABLISHED)
+		mptcp_event(MPTCP_EVENT_SUB_CLOSED, mptcp_sk(sk), ssk, GFP_KERNEL);
+
+	/* subflow aborted before reaching the fully_established status
+	 * attempt the creation of the next subflow
+	 */
+	mptcp_pm_subflow_check_next(mptcp_sk(sk), subflow);
+
+	__mptcp_close_ssk(sk, ssk, subflow, MPTCP_CF_PUSH);
+}
+
+static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu)
+{
+	return 0;
+}
+
+static void __mptcp_close_subflow(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	might_sleep();
+
+	mptcp_for_each_subflow_safe(msk, subflow, tmp) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		int ssk_state = inet_sk_state_load(ssk);
+
+		if (ssk_state != TCP_CLOSE &&
+		    (ssk_state != TCP_CLOSE_WAIT ||
+		     inet_sk_state_load(sk) != TCP_ESTABLISHED ||
+		     __mptcp_check_fallback(msk)))
+			continue;
+
+		/* 'subflow_data_ready' will re-sched once rx queue is empty */
+		if (!skb_queue_empty_lockless(&ssk->sk_receive_queue))
+			continue;
+
+		mptcp_close_ssk(sk, ssk, subflow);
+	}
+
+}
+
+static bool mptcp_close_tout_expired(const struct sock *sk)
+{
+	if (!inet_csk(sk)->icsk_mtup.probe_timestamp ||
+	    sk->sk_state == TCP_CLOSE)
+		return false;
+
+	return time_after32(tcp_jiffies32,
+		  inet_csk(sk)->icsk_mtup.probe_timestamp + mptcp_close_timeout(sk));
+}
+
+static void mptcp_check_fastclose(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct sock *sk = (struct sock *)msk;
+
+	if (likely(!READ_ONCE(msk->rcv_fastclose)))
+		return;
+
+	mptcp_token_destroy(msk);
+
+	mptcp_for_each_subflow_safe(msk, subflow, tmp) {
+		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
+		bool slow;
+
+		slow = lock_sock_fast(tcp_sk);
+		if (tcp_sk->sk_state != TCP_CLOSE) {
+			mptcp_send_active_reset_reason(tcp_sk);
+			tcp_set_state(tcp_sk, TCP_CLOSE);
+		}
+		unlock_sock_fast(tcp_sk, slow);
+	}
+
+	/* Mirror the tcp_reset() error propagation */
+	switch (sk->sk_state) {
+	case TCP_SYN_SENT:
+		WRITE_ONCE(sk->sk_err, ECONNREFUSED);
+		break;
+	case TCP_CLOSE_WAIT:
+		WRITE_ONCE(sk->sk_err, EPIPE);
+		break;
+	case TCP_CLOSE:
+		return;
+	default:
+		WRITE_ONCE(sk->sk_err, ECONNRESET);
+	}
+
+	mptcp_set_state(sk, TCP_CLOSE);
+	WRITE_ONCE(sk->sk_shutdown, SHUTDOWN_MASK);
+	smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
+	set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags);
+
+	/* the calling mptcp_worker will properly destroy the socket */
+	if (sock_flag(sk, SOCK_DEAD))
+		return;
+
+	sk->sk_state_change(sk);
+	sk_error_report(sk);
+}
+
+/*
+ * Retransmit the specified data fragment on all the selected subflows,
+ * starting from the specified sequence
+ */
+static int __mptcp_push_retrans(struct sock *sk, struct mptcp_data_frag *dfrag,
+				u64 sent_seq)
+{
+	struct mptcp_sendmsg_info info = { .data_lock_held = true, };
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_subflow_context *subflow;
+	struct sock *ssk;
+	int ret, len = 0;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->scheduled)) {
+			u16 offset = sent_seq - dfrag->data_seq;
+			u16 copied = 0;
+
+			mptcp_subflow_set_scheduled(subflow, false);
+
+			ssk = mptcp_subflow_tcp_sock(subflow);
+
+			lock_sock(ssk);
+
+			/* limit retransmission to the bytes already sent on some subflows */
+			info.sent = offset;
+			info.limit = READ_ONCE(msk->csum_enabled) ? dfrag->data_len :
+								    dfrag->already_sent;
+
+			/*
+			 * make the whole retrans decision, xmit, disallow
+			 * fallback atomic, note that we can't retrans even
+			 * when an infinite fallback is in progress, i.e. new
+			 * subflows are disallowed.
+			 */
+			spin_lock_bh(&msk->fallback_lock);
+			if (__mptcp_check_fallback(msk) ||
+			    !msk->allow_subflows) {
+				spin_unlock_bh(&msk->fallback_lock);
+				release_sock(ssk);
+				return -1;
+			}
+
+			while (info.sent < info.limit) {
+				ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+				if (ret <= 0)
+					break;
+
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
+				copied += ret;
+				info.sent += ret;
+			}
+			if (copied) {
+				len = max(copied, len);
+				tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
+					 info.size_goal);
+				msk->allow_infinite_fallback = false;
+			}
+			spin_unlock_bh(&msk->fallback_lock);
+
+			release_sock(ssk);
+		}
+	}
+	return len;
+}
+
+static void __mptcp_retrans(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_data_frag *dfrag;
+	u64 retrans_seq, sent_seq;
+	bool need_retrans;
+	int err, len;
+
+	mptcp_pm_chk_stale(msk);
+
+	/* Get an updated and consistent rtx queue status. */
+	mptcp_data_lock(sk);
+	__mptcp_clean_una_wakeup(sk);
+	retrans_seq = msk->snd_una;
+	dfrag = mptcp_rtx_head(sk);
+	need_retrans = !!dfrag;
+	mptcp_data_unlock(sk);
+
+	for (;;) {
+		bool already_acked;
+
+		err = mptcp_sched_get_retrans(msk);
+		if (err)
+			break;
+
+		/* `already_sent` can be 0 for `dfrag` belonging to the RTX
+		 *  queue due to __mptcp_retransmit_pending_data().
+		 */
+		if (!dfrag || !dfrag->already_sent)
+			break;
+
+		/* Can fail only in case of fallback. */
+		len = __mptcp_push_retrans(sk, dfrag, retrans_seq);
+		if (len < 0)
+			goto clear_scheduled;
+
+		retrans_seq += len;
+		msk->bytes_retrans += len;
+		dfrag->already_sent = max_t(u16, dfrag->already_sent,
+					    retrans_seq - dfrag->data_seq);
+
+		/* With csum enabled, retransmission can send new data. */
+		sent_seq = dfrag->already_sent + dfrag->data_seq;
+		if (after64(sent_seq, msk->snd_nxt))
+			WRITE_ONCE(msk->snd_nxt, sent_seq);
+
+		/* Attempt the next fragment only if the current one is
+		 * completely retransmitted.
+		 */
+		if (before64(retrans_seq, dfrag->data_seq + dfrag->data_len))
+			break;
+
+		dfrag = list_is_last(&dfrag->list, &msk->rtx_queue) ?
+				NULL : list_next_entry(dfrag, list);
+		if (!dfrag)
+			break;
+
+		/* Incoming acks can move snd_una after the current dfrag
+		 * across loop iterations, if so start again from RTX head.
+		 */
+		mptcp_data_lock(sk);
+		already_acked = !before64(msk->snd_una, dfrag->data_seq +
+					  dfrag->already_sent);
+		if (already_acked) {
+			__mptcp_clean_una_wakeup(sk);
+			retrans_seq = msk->snd_una;
+			dfrag = mptcp_rtx_head(sk);
+			need_retrans = !!dfrag;
+		} else if (after64(msk->snd_una, retrans_seq)) {
+			retrans_seq = msk->snd_una;
+		}
+		mptcp_data_unlock(sk);
+	}
+
+	/* Attempt data-fin retransmission only when the RTX queue is empty. */
+	if (!need_retrans) {
+		if (mptcp_data_fin_enabled(msk)) {
+			struct inet_connection_sock *icsk = inet_csk(sk);
+
+			WRITE_ONCE(icsk->icsk_retransmits,
+				   icsk->icsk_retransmits + 1);
+			mptcp_set_datafin_timeout(sk);
+			mptcp_send_ack(msk);
+			goto reset_timer;
+		}
+
+		if (!mptcp_send_head(sk))
+			goto clear_scheduled;
+	}
+
+reset_timer:
+	mptcp_check_and_set_pending(sk);
+
+	if (!mptcp_rtx_timer_pending(sk))
+		mptcp_reset_rtx_timer(sk);
+
+clear_scheduled:
+	/* If no rtx data was available or in case of fallback, there
+	 * could be left-over scheduled subflows; clear them all
+	 * or later xmit could use bad ones
+	 */
+	mptcp_for_each_subflow(msk, subflow)
+		if (READ_ONCE(subflow->scheduled))
+			mptcp_subflow_set_scheduled(subflow, false);
+}
+
+/* schedule the timeout timer for the relevant event: either close timeout
+ * or mp_fail timeout. The close timeout takes precedence on the mp_fail one
+ */
+void mptcp_reset_tout_timer(struct mptcp_sock *msk, unsigned long fail_tout)
+{
+	struct sock *sk = (struct sock *)msk;
+	unsigned long timeout, close_timeout;
+
+	if (!fail_tout && !inet_csk(sk)->icsk_mtup.probe_timestamp)
+		return;
+
+	close_timeout = (unsigned long)inet_csk(sk)->icsk_mtup.probe_timestamp -
+			tcp_jiffies32 + jiffies + mptcp_close_timeout(sk);
+
+	/* the close timeout takes precedence on the fail one, and here at least one of
+	 * them is active
+	 */
+	timeout = inet_csk(sk)->icsk_mtup.probe_timestamp ? close_timeout : fail_tout;
+
+	sk_reset_timer(sk, &inet_csk(sk)->mptcp_tout_timer, timeout);
+}
+
+static void mptcp_mp_fail_no_response(struct mptcp_sock *msk)
+{
+	struct sock *ssk = msk->first;
+	bool slow;
+
+	if (!ssk)
+		return;
+
+	pr_debug("MP_FAIL doesn't respond, reset the subflow\n");
+
+	slow = lock_sock_fast(ssk);
+	mptcp_subflow_reset(ssk);
+	WRITE_ONCE(mptcp_subflow_ctx(ssk)->fail_tout, 0);
+	unlock_sock_fast(ssk, slow);
+}
+
+static void mptcp_backlog_purge(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *tmp, *skb;
+	LIST_HEAD(backlog);
+
+	mptcp_data_lock(sk);
+	list_splice_init(&msk->backlog_list, &backlog);
+	msk->backlog_len = 0;
+	mptcp_data_unlock(sk);
+
+	list_for_each_entry_safe(skb, tmp, &backlog, list) {
+		mptcp_borrow_fwdmem(sk, skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_SOCKET_CLOSE);
+	}
+	sk_mem_reclaim(sk);
+}
+
+static void mptcp_do_fastclose(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	mptcp_set_state(sk, TCP_CLOSE);
+	mptcp_backlog_purge(sk);
+	msk->fastclosing = 1;
+
+	/* Explicitly send the fastclose reset as need */
+	if (__mptcp_check_fallback(msk))
+		return;
+
+	mptcp_for_each_subflow_safe(msk, subflow, tmp) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		lock_sock(ssk);
+
+		/* Some subflow socket states don't allow/need a reset.*/
+		if ((1 << ssk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))
+			goto unlock;
+
+		subflow->send_fastclose = 1;
+
+		/* Initialize rcv_mss to TCP_MIN_MSS to avoid division by 0
+		 * issue in __tcp_select_window(), see tcp_disconnect().
+		 */
+		inet_csk(ssk)->icsk_ack.rcv_mss = TCP_MIN_MSS;
+
+		tcp_send_active_reset(ssk, SK_RST_REASON_TCP_ABORT_ON_CLOSE);
+unlock:
+		release_sock(ssk);
+	}
+}
+
+static void mptcp_worker(struct work_struct *work)
+{
+	struct mptcp_sock *msk = container_of(work, struct mptcp_sock, work);
+	struct sock *sk = (struct sock *)msk;
+	unsigned long fail_tout;
+	int state;
+
+	lock_sock(sk);
+	state = sk->sk_state;
+	if (unlikely((1 << state) & (TCPF_CLOSE | TCPF_LISTEN)))
+		goto unlock;
+
+	mptcp_check_fastclose(msk);
+
+	mptcp_pm_worker(msk);
+
+	mptcp_check_send_data_fin(sk);
+	mptcp_check_data_fin_ack(sk);
+	mptcp_check_data_fin(sk);
+
+	if (test_and_clear_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
+		__mptcp_close_subflow(sk);
+
+	if (mptcp_close_tout_expired(sk)) {
+		struct mptcp_subflow_context *subflow, *tmp;
+
+		mptcp_do_fastclose(sk);
+		mptcp_for_each_subflow_safe(msk, subflow, tmp)
+			__mptcp_close_ssk(sk, subflow->tcp_sock, subflow, 0);
+		mptcp_close_wake_up(sk);
+	}
+
+	if (sock_flag(sk, SOCK_DEAD) && sk->sk_state == TCP_CLOSE) {
+		__mptcp_destroy_sock(sk);
+		goto unlock;
+	}
+
+	if (test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
+		__mptcp_retrans(sk);
+
+	fail_tout = msk->first ? READ_ONCE(mptcp_subflow_ctx(msk->first)->fail_tout) : 0;
+	if (fail_tout && time_after(jiffies, fail_tout))
+		mptcp_mp_fail_no_response(msk);
+
+unlock:
+	release_sock(sk);
+	sock_put(sk);
+}
+
+static void __mptcp_init_sock(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct net *net = sock_net(sk);
+
+	INIT_LIST_HEAD(&msk->conn_list);
+	INIT_LIST_HEAD(&msk->join_list);
+	INIT_LIST_HEAD(&msk->rtx_queue);
+	INIT_LIST_HEAD(&msk->backlog_list);
+	INIT_WORK(&msk->work, mptcp_worker);
+	msk->out_of_order_queue = RB_ROOT;
+	msk->first_pending = NULL;
+
+	/* msk does not go through tcp_init_sock(); seed RTO bounds. */
+	icsk->icsk_rto_min =
+		usecs_to_jiffies(READ_ONCE(net->ipv4.sysctl_tcp_rto_min_us));
+	icsk->icsk_rto_max =
+		msecs_to_jiffies(READ_ONCE(net->ipv4.sysctl_tcp_rto_max_ms));
+	msk->timer_ival = icsk->icsk_rto_min;
+	msk->scaling_ratio = TCP_DEFAULT_SCALING_RATIO;
+	msk->backlog_len = 0;
+	mptcp_init_rtt_est(msk);
+
+	WRITE_ONCE(msk->first, NULL);
+	inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;
+	WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));
+	msk->allow_infinite_fallback = true;
+	msk->allow_subflows = true;
+	msk->recovery = false;
+	msk->subflow_id = 1;
+	msk->last_data_sent = tcp_jiffies32;
+	msk->last_data_recv = tcp_jiffies32;
+	msk->last_ack_recv = tcp_jiffies32;
+
+	mptcp_pm_data_init(msk);
+	spin_lock_init(&msk->fallback_lock);
+
+	/* re-use the csk retrans timer for MPTCP-level retrans */
+	timer_setup(&sk->mptcp_retransmit_timer, mptcp_retransmit_timer, 0);
+	timer_setup(&msk->sk.mptcp_tout_timer, mptcp_tout_timer, 0);
+}
+
+static void mptcp_ca_reset(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	tcp_assign_congestion_control(sk);
+	strscpy(mptcp_sk(sk)->ca_name, icsk->icsk_ca_ops->name,
+		sizeof(mptcp_sk(sk)->ca_name));
+
+	/* no need to keep a reference to the ops, the name will suffice */
+	tcp_cleanup_congestion_control(sk);
+	icsk->icsk_ca_ops = NULL;
+}
+
+static int mptcp_init_sock(struct sock *sk)
+{
+	struct net *net = sock_net(sk);
+	int ret;
+
+	__mptcp_init_sock(sk);
+
+	if (!mptcp_is_enabled(net))
+		return -ENOPROTOOPT;
+
+	if (unlikely(!net->mib.mptcp_statistics) && !mptcp_mib_alloc(net))
+		return -ENOMEM;
+
+	rcu_read_lock();
+	ret = mptcp_init_sched(mptcp_sk(sk),
+			       mptcp_sched_find(mptcp_get_scheduler(net)));
+	rcu_read_unlock();
+	if (ret)
+		return ret;
+
+	set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
+
+	/* fetch the ca name; do it outside __mptcp_init_sock(), so that clone will
+	 * propagate the correct value
+	 */
+	mptcp_ca_reset(sk);
+
+	sk_sockets_allocated_inc(sk);
+	sk->sk_rcvbuf = READ_ONCE(net->ipv4.sysctl_tcp_rmem[1]);
+	sk->sk_sndbuf = READ_ONCE(net->ipv4.sysctl_tcp_wmem[1]);
+	sk->sk_write_space = sk_stream_write_space;
+
+	return 0;
+}
+
+static void __mptcp_clear_xmit(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_data_frag *dtmp, *dfrag;
+
+	msk->first_pending = NULL;
+	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list)
+		dfrag_clear(sk, dfrag);
+}
+
+void mptcp_cancel_work(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (cancel_work_sync(&msk->work))
+		__sock_put(sk);
+}
+
+void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how)
+{
+	lock_sock(ssk);
+
+	switch (ssk->sk_state) {
+	case TCP_LISTEN:
+		if (!(how & RCV_SHUTDOWN))
+			break;
+		fallthrough;
+	case TCP_SYN_SENT:
+		WARN_ON_ONCE(tcp_disconnect(ssk, O_NONBLOCK));
+		break;
+	default:
+		if (__mptcp_check_fallback(mptcp_sk(sk))) {
+			pr_debug("Fallback\n");
+			ssk->sk_shutdown |= how;
+			tcp_shutdown(ssk, how);
+
+			/* simulate the data_fin ack reception to let the state
+			 * machine move forward
+			 */
+			WRITE_ONCE(mptcp_sk(sk)->snd_una, mptcp_sk(sk)->snd_nxt);
+			mptcp_schedule_work(sk);
+		} else {
+			pr_debug("Sending DATA_FIN on subflow %p\n", ssk);
+			tcp_send_ack(ssk);
+			if (!mptcp_rtx_timer_pending(sk))
+				mptcp_reset_rtx_timer(sk);
+		}
+		break;
+	}
+
+	release_sock(ssk);
+}
+
+void mptcp_set_state(struct sock *sk, int state)
+{
+	int oldstate = sk->sk_state;
+
+	switch (state) {
+	case TCP_ESTABLISHED:
+		if (oldstate != TCP_ESTABLISHED)
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_CURRESTAB);
+		break;
+	case TCP_CLOSE_WAIT:
+		/* Unlike TCP, MPTCP sk would not have the TCP_SYN_RECV state:
+		 * MPTCP "accepted" sockets will be created later on. So no
+		 * transition from TCP_SYN_RECV to TCP_CLOSE_WAIT.
+		 */
+		break;
+	case TCP_CLOSE:
+		clear_bit(MPTCP_RTX_ENABLED, &mptcp_sk(sk)->flags);
+		fallthrough;
+	default:
+		if (oldstate == TCP_ESTABLISHED || oldstate == TCP_CLOSE_WAIT)
+			MPTCP_DEC_STATS(sock_net(sk), MPTCP_MIB_CURRESTAB);
+	}
+
+	inet_sk_state_store(sk, state);
+}
+
+static const unsigned char new_state[16] = {
+	/* current state:     new state:      action:	*/
+	[0 /* (Invalid) */] = TCP_CLOSE,
+	[TCP_ESTABLISHED]   = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
+	[TCP_SYN_SENT]      = TCP_CLOSE,
+	[TCP_SYN_RECV]      = TCP_FIN_WAIT1 | TCP_ACTION_FIN,
+	[TCP_FIN_WAIT1]     = TCP_FIN_WAIT1,
+	[TCP_FIN_WAIT2]     = TCP_FIN_WAIT2,
+	[TCP_TIME_WAIT]     = TCP_CLOSE,	/* should not happen ! */
+	[TCP_CLOSE]         = TCP_CLOSE,
+	[TCP_CLOSE_WAIT]    = TCP_LAST_ACK  | TCP_ACTION_FIN,
+	[TCP_LAST_ACK]      = TCP_LAST_ACK,
+	[TCP_LISTEN]        = TCP_CLOSE,
+	[TCP_CLOSING]       = TCP_CLOSING,
+	[TCP_NEW_SYN_RECV]  = TCP_CLOSE,	/* should not happen ! */
+};
+
+static int mptcp_close_state(struct sock *sk)
+{
+	int next = (int)new_state[sk->sk_state];
+	int ns = next & TCP_STATE_MASK;
+
+	mptcp_set_state(sk, ns);
+
+	return next & TCP_ACTION_FIN;
+}
+
+static void mptcp_check_send_data_fin(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p snd_data_fin_enable=%d pending=%d snd_nxt=%llu write_seq=%llu\n",
+		 msk, msk->snd_data_fin_enable, !!mptcp_send_head(sk),
+		 msk->snd_nxt, msk->write_seq);
+
+	/* we still need to enqueue subflows or not really shutting down,
+	 * skip this
+	 */
+	if (!msk->snd_data_fin_enable || msk->snd_nxt + 1 != msk->write_seq ||
+	    mptcp_send_head(sk))
+		return;
+
+	WRITE_ONCE(msk->snd_nxt, msk->write_seq);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
+
+		mptcp_subflow_shutdown(sk, tcp_sk, SEND_SHUTDOWN);
+	}
+}
+
+static void __mptcp_wr_shutdown(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p snd_data_fin_enable=%d shutdown=%x state=%d pending=%d\n",
+		 msk, msk->snd_data_fin_enable, sk->sk_shutdown, sk->sk_state,
+		 !!mptcp_send_head(sk));
+
+	/* will be ignored by fallback sockets */
+	WRITE_ONCE(msk->write_seq, msk->write_seq + 1);
+	WRITE_ONCE(msk->snd_data_fin_enable, 1);
+
+	mptcp_check_send_data_fin(sk);
+}
+
+static void __mptcp_destroy_sock(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p\n", msk);
+
+	might_sleep();
+
+	mptcp_stop_rtx_timer(sk);
+	sk_stop_timer(sk, &inet_csk(sk)->mptcp_tout_timer);
+	msk->pm.status = 0;
+	mptcp_release_sched(msk);
+
+	sk->sk_prot->destroy(sk);
+
+	sk_stream_kill_queues(sk);
+	xfrm_sk_free_policy(sk);
+
+	sock_put(sk);
+}
+
+void __mptcp_unaccepted_force_close(struct sock *sk)
+{
+	sock_set_flag(sk, SOCK_DEAD);
+	mptcp_do_fastclose(sk);
+	__mptcp_destroy_sock(sk);
+}
+
+static __poll_t mptcp_check_readable(struct sock *sk)
+{
+	return mptcp_epollin_ready(sk) ? EPOLLIN | EPOLLRDNORM : 0;
+}
+
+static void mptcp_check_listen_stop(struct sock *sk)
+{
+	struct sock *ssk;
+
+	if (inet_sk_state_load(sk) != TCP_LISTEN)
+		return;
+
+	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
+	ssk = mptcp_sk(sk)->first;
+	if (WARN_ON_ONCE(!ssk || inet_sk_state_load(ssk) != TCP_LISTEN))
+		return;
+
+	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
+	tcp_set_state(ssk, TCP_CLOSE);
+	mptcp_subflow_queue_clean(sk, ssk);
+	inet_csk_listen_stop(ssk);
+	mptcp_event_pm_listener(ssk, MPTCP_EVENT_LISTENER_CLOSED);
+	release_sock(ssk);
+}
+
+bool __mptcp_close(struct sock *sk, long timeout)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool do_cancel_work = false;
+	int subflows_alive = 0;
+
+	WRITE_ONCE(sk->sk_shutdown, SHUTDOWN_MASK);
+
+	if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) {
+		mptcp_check_listen_stop(sk);
+		mptcp_set_state(sk, TCP_CLOSE);
+		goto cleanup;
+	}
+
+	if (mptcp_data_avail(msk) || timeout < 0 ||
+	    (sock_flag(sk, SOCK_LINGER) && !sk->sk_lingertime)) {
+		/* If the msk has read data, or the caller explicitly ask it,
+		 * do the MPTCP equivalent of TCP reset, aka MPTCP fastclose
+		 */
+		mptcp_do_fastclose(sk);
+		timeout = 0;
+	} else if (mptcp_close_state(sk)) {
+		__mptcp_wr_shutdown(sk);
+	}
+
+	sk_stream_wait_close(sk, timeout);
+
+cleanup:
+	/* orphan all the subflows */
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow = lock_sock_fast_nested(ssk);
+
+		subflows_alive += ssk->sk_state != TCP_CLOSE;
+
+		/* since the close timeout takes precedence on the fail one,
+		 * cancel the latter
+		 */
+		if (ssk == msk->first)
+			subflow->fail_tout = 0;
+
+		/* detach from the parent socket, but allow data_ready to
+		 * push incoming data into the mptcp stack, to properly ack it
+		 */
+		ssk->sk_socket = NULL;
+		ssk->sk_wq = NULL;
+		unlock_sock_fast(ssk, slow);
+	}
+	sock_orphan(sk);
+
+	/* all the subflows are closed, only timeout can change the msk
+	 * state, let's not keep resources busy for no reasons
+	 */
+	if (subflows_alive == 0)
+		mptcp_set_state(sk, TCP_CLOSE);
+
+	sock_hold(sk);
+	pr_debug("msk=%p state=%d\n", sk, sk->sk_state);
+	mptcp_pm_connection_closed(msk);
+
+	if (sk->sk_state == TCP_CLOSE) {
+		__mptcp_destroy_sock(sk);
+		do_cancel_work = true;
+	} else {
+		mptcp_start_tout_timer(sk);
+	}
+
+	return do_cancel_work;
+}
+
+static void mptcp_close(struct sock *sk, long timeout)
+{
+	bool do_cancel_work;
+
+	lock_sock(sk);
+
+	do_cancel_work = __mptcp_close(sk, timeout);
+	release_sock(sk);
+	if (do_cancel_work)
+		mptcp_cancel_work(sk);
+
+	sock_put(sk);
+}
+
+static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	const struct ipv6_pinfo *ssk6 = inet6_sk(ssk);
+	struct ipv6_pinfo *msk6 = inet6_sk(msk);
+
+	msk->sk_v6_daddr = ssk->sk_v6_daddr;
+	msk->sk_v6_rcv_saddr = ssk->sk_v6_rcv_saddr;
+
+	if (msk6 && ssk6) {
+		msk6->saddr = ssk6->saddr;
+		msk6->flow_label = ssk6->flow_label;
+	}
+#endif
+
+	inet_sk(msk)->inet_num = inet_sk(ssk)->inet_num;
+	inet_sk(msk)->inet_dport = inet_sk(ssk)->inet_dport;
+	inet_sk(msk)->inet_sport = inet_sk(ssk)->inet_sport;
+	inet_sk(msk)->inet_daddr = inet_sk(ssk)->inet_daddr;
+	inet_sk(msk)->inet_saddr = inet_sk(ssk)->inet_saddr;
+	inet_sk(msk)->inet_rcv_saddr = inet_sk(ssk)->inet_rcv_saddr;
+}
+
+static void mptcp_destroy_common(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow, *tmp;
+	struct sock *sk = (struct sock *)msk;
+
+	__mptcp_clear_xmit(sk);
+	mptcp_backlog_purge(sk);
+
+	/* join list will be eventually flushed (with rst) at sock lock release time */
+	mptcp_for_each_subflow_safe(msk, subflow, tmp)
+		__mptcp_close_ssk(sk, mptcp_subflow_tcp_sock(subflow), subflow, 0);
+
+	__skb_queue_purge(&sk->sk_receive_queue);
+	skb_rbtree_purge(&msk->out_of_order_queue);
+
+	/* move all the rx fwd alloc into the sk_mem_reclaim_final in
+	 * inet_sock_destruct() will dispose it
+	 */
+	mptcp_token_destroy(msk);
+	mptcp_pm_destroy(msk);
+}
+
+static int mptcp_disconnect(struct sock *sk, int flags)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	/* We are on the fastopen error path. We can't call straight into the
+	 * subflows cleanup code due to lock nesting (we are already under
+	 * msk->firstsocket lock).
+	 */
+	if (msk->fastopening)
+		return -EBUSY;
+
+	mptcp_check_listen_stop(sk);
+	mptcp_set_state(sk, TCP_CLOSE);
+
+	/* The later subflow close can not kick again the tout timer,
+	 * as the msk is already in closed status.
+	 */
+	msk->timer_ival = icsk->icsk_rto_min;
+	sk_stop_timer_sync(sk, &sk->mptcp_retransmit_timer);
+	icsk->icsk_mtup.probe_timestamp = 0;
+	sk_stop_timer_sync(sk, &icsk->mptcp_tout_timer);
+
+	mptcp_pm_connection_closed(msk);
+
+	/* msk->subflow is still intact, the following will not free the first
+	 * subflow
+	 */
+	mptcp_do_fastclose(sk);
+	mptcp_destroy_common(msk);
+
+	/* The first subflow is already in TCP_CLOSE status, the following
+	 * can't overlap with a fallback anymore
+	 */
+	spin_lock_bh(&msk->fallback_lock);
+	msk->allow_subflows = true;
+	msk->allow_infinite_fallback = true;
+	WRITE_ONCE(msk->flags, 0);
+	spin_unlock_bh(&msk->fallback_lock);
+
+	msk->cb_flags = 0;
+	msk->recovery = false;
+	WRITE_ONCE(msk->can_ack, false);
+	WRITE_ONCE(msk->fully_established, false);
+	WRITE_ONCE(msk->rcv_data_fin, false);
+	WRITE_ONCE(msk->snd_data_fin_enable, false);
+	WRITE_ONCE(msk->rcv_fastclose, false);
+	WRITE_ONCE(msk->use_64bit_ack, false);
+	WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));
+	mptcp_pm_data_reset(msk);
+	mptcp_ca_reset(sk);
+	msk->bytes_consumed = 0;
+	msk->bytes_acked = 0;
+	msk->bytes_received = 0;
+	msk->bytes_sent = 0;
+	msk->bytes_retrans = 0;
+	msk->rcvspace_init = 0;
+	msk->fastclosing = 0;
+	mptcp_init_rtt_est(msk);
+
+	/* for fallback's sake */
+	WRITE_ONCE(msk->ack_seq, 0);
+	atomic64_set(&msk->rcv_wnd_sent, 0);
+
+	WRITE_ONCE(sk->sk_shutdown, 0);
+	sk_error_report(sk);
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static struct ipv6_pinfo *mptcp_inet6_sk(const struct sock *sk)
+{
+	struct mptcp6_sock *msk6 = container_of(mptcp_sk(sk), struct mptcp6_sock, msk);
+
+	return &msk6->np;
+}
+
+static void mptcp_copy_ip6_options(struct sock *newsk, const struct sock *sk)
+{
+	const struct ipv6_pinfo *np = inet6_sk(sk);
+	struct ipv6_txoptions *opt;
+	struct ipv6_pinfo *newnp;
+
+	newnp = inet6_sk(newsk);
+
+	rcu_read_lock();
+	opt = rcu_dereference(np->opt);
+	if (opt) {
+		opt = ipv6_dup_options(newsk, opt);
+		if (!opt)
+			net_warn_ratelimited("%s: Failed to copy ip6 options\n", __func__);
+	}
+	RCU_INIT_POINTER(newnp->opt, opt);
+	rcu_read_unlock();
+}
+#endif
+
+static void mptcp_copy_ip_options(struct sock *newsk, const struct sock *sk)
+{
+	struct ip_options_rcu *inet_opt, *newopt = NULL;
+	const struct inet_sock *inet = inet_sk(sk);
+	struct inet_sock *newinet;
+
+	newinet = inet_sk(newsk);
+
+	rcu_read_lock();
+	inet_opt = rcu_dereference(inet->inet_opt);
+	if (inet_opt) {
+		newopt = sock_kmemdup(newsk, inet_opt, sizeof(*inet_opt) +
+				      inet_opt->opt.optlen, GFP_ATOMIC);
+		if (!newopt)
+			net_warn_ratelimited("%s: Failed to copy ip options\n", __func__);
+	}
+	RCU_INIT_POINTER(newinet->inet_opt, newopt);
+	rcu_read_unlock();
+}
+
+struct sock *mptcp_sk_clone_init(const struct sock *sk,
+				 const struct mptcp_options_received *mp_opt,
+				 struct sock *ssk,
+				 struct request_sock *req)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct sock *nsk = sk_clone_lock(sk, GFP_ATOMIC);
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk;
+
+	if (!nsk)
+		return NULL;
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (nsk->sk_family == AF_INET6)
+		inet_sk(nsk)->pinet6 = mptcp_inet6_sk(nsk);
+#endif
+
+	__mptcp_init_sock(nsk);
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (nsk->sk_family == AF_INET6)
+		mptcp_copy_ip6_options(nsk, sk);
+	else
+#endif
+		mptcp_copy_ip_options(nsk, sk);
+
+	msk = mptcp_sk(nsk);
+	WRITE_ONCE(msk->local_key, subflow_req->local_key);
+	WRITE_ONCE(msk->token, subflow_req->token);
+	msk->in_accept_queue = 1;
+	WRITE_ONCE(msk->fully_established, false);
+	if (mp_opt->suboptions & OPTION_MPTCP_CSUMREQD)
+		WRITE_ONCE(msk->csum_enabled, true);
+
+	WRITE_ONCE(msk->write_seq, subflow_req->idsn + 1);
+	WRITE_ONCE(msk->snd_nxt, msk->write_seq);
+	WRITE_ONCE(msk->snd_una, msk->write_seq);
+	WRITE_ONCE(msk->wnd_end, msk->snd_nxt + tcp_sk(ssk)->snd_wnd);
+	msk->setsockopt_seq = mptcp_sk(sk)->setsockopt_seq;
+	mptcp_init_sched(msk, mptcp_sk(sk)->sched);
+
+	/* passive msk is created after the first/MPC subflow */
+	msk->subflow_id = 2;
+
+	sock_reset_flag(nsk, SOCK_RCU_FREE);
+	security_inet_csk_clone(nsk, req);
+
+	/* this can't race with mptcp_close(), as the msk is
+	 * not yet exposted to user-space
+	 */
+	mptcp_set_state(nsk, TCP_ESTABLISHED);
+
+	/* The msk maintain a ref to each subflow in the connections list */
+	WRITE_ONCE(msk->first, ssk);
+	subflow = mptcp_subflow_ctx(ssk);
+	list_add(&subflow->node, &msk->conn_list);
+	sock_hold(ssk);
+
+	/* new mpc subflow takes ownership of the newly
+	 * created mptcp socket
+	 */
+	mptcp_token_accept(subflow_req, msk);
+
+	/* set msk addresses early to ensure mptcp_pm_get_local_id()
+	 * uses the correct data
+	 */
+	mptcp_copy_inaddrs(nsk, ssk);
+
+	mptcp_rcv_space_init(msk, ssk);
+	msk->rcvq_space.time = mptcp_stamp();
+
+	if (mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
+		__mptcp_subflow_fully_established(msk, subflow, mp_opt);
+	bh_unlock_sock(nsk);
+
+	/* note: the newly allocated socket refcount is 2 now */
+	return nsk;
+}
+
+static void mptcp_destroy(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	/* allow the following to close even the initial subflow */
+	msk->free_first = 1;
+	mptcp_destroy_common(msk);
+	sk_sockets_allocated_dec(sk);
+}
+
+void __mptcp_data_acked(struct sock *sk)
+{
+	if (!sock_owned_by_user(sk))
+		__mptcp_clean_una(sk);
+	else
+		__set_bit(MPTCP_CLEAN_UNA, &mptcp_sk(sk)->cb_flags);
+}
+
+void __mptcp_check_push(struct sock *sk, struct sock *ssk)
+{
+	if (!sock_owned_by_user(sk))
+		__mptcp_subflow_push_pending(sk, ssk, false);
+	else
+		__set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->cb_flags);
+}
+
+#define MPTCP_FLAGS_PROCESS_CTX_NEED (BIT(MPTCP_PUSH_PENDING) | \
+				      BIT(MPTCP_RETRANSMIT) | \
+				      BIT(MPTCP_FLUSH_JOIN_LIST))
+
+/* processes deferred events and flush wmem */
+static void mptcp_release_cb(struct sock *sk)
+	__must_hold(&sk->sk_lock.slock)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	u32 moved = 0;
+
+	for (;;) {
+		unsigned long flags = (msk->cb_flags & MPTCP_FLAGS_PROCESS_CTX_NEED);
+		struct list_head join_list, skbs;
+		bool spool_bl;
+
+		spool_bl = mptcp_can_spool_backlog(sk, &skbs);
+		if (!flags && !spool_bl)
+			break;
+
+		INIT_LIST_HEAD(&join_list);
+		list_splice_init(&msk->join_list, &join_list);
+
+		/* the following actions acquire the subflow socket lock
+		 *
+		 * 1) can't be invoked in atomic scope
+		 * 2) must avoid ABBA deadlock with msk socket spinlock: the RX
+		 *    datapath acquires the msk socket spinlock while helding
+		 *    the subflow socket lock
+		 */
+		msk->cb_flags &= ~flags;
+		spin_unlock_bh(&sk->sk_lock.slock);
+
+		if (flags & BIT(MPTCP_FLUSH_JOIN_LIST))
+			__mptcp_flush_join_list(sk, &join_list);
+		if (flags & BIT(MPTCP_PUSH_PENDING))
+			__mptcp_push_pending(sk, 0);
+		if (flags & BIT(MPTCP_RETRANSMIT))
+			__mptcp_retrans(sk);
+		if (spool_bl && __mptcp_move_skbs(sk, &skbs, &moved)) {
+			/* notify ack seq update */
+			mptcp_cleanup_rbuf(msk, 0);
+			sk->sk_data_ready(sk);
+		}
+
+		cond_resched();
+		spin_lock_bh(&sk->sk_lock.slock);
+	}
+	if (moved)
+		WRITE_ONCE(msk->backlog_len, msk->backlog_len - moved);
+
+	if (__test_and_clear_bit(MPTCP_CLEAN_UNA, &msk->cb_flags))
+		__mptcp_clean_una_wakeup(sk);
+	if (unlikely(msk->cb_flags)) {
+		/* be sure to sync the msk state before taking actions
+		 * depending on sk_state (MPTCP_ERROR_REPORT)
+		 * On sk release avoid actions depending on the first subflow
+		 */
+		if (__test_and_clear_bit(MPTCP_SYNC_STATE, &msk->cb_flags) && msk->first)
+			__mptcp_sync_state(sk, msk->pending_state);
+		if (__test_and_clear_bit(MPTCP_ERROR_REPORT, &msk->cb_flags))
+			__mptcp_error_report(sk);
+		if (__test_and_clear_bit(MPTCP_SYNC_SNDBUF, &msk->cb_flags))
+			__mptcp_sync_sndbuf(sk);
+	}
+}
+
+/* MP_JOIN client subflow must wait for 4th ack before sending any data:
+ * TCP can't schedule delack timer before the subflow is fully established.
+ * MPTCP uses the delack timer to do 3rd ack retransmissions
+ */
+static void schedule_3rdack_retransmission(struct sock *ssk)
+{
+	struct inet_connection_sock *icsk = inet_csk(ssk);
+	struct tcp_sock *tp = tcp_sk(ssk);
+	unsigned long timeout;
+
+	if (mptcp_subflow_ctx(ssk)->fully_established)
+		return;
+
+	/* reschedule with a timeout above RTT, as we must look only for drop */
+	if (tp->srtt_us)
+		timeout = usecs_to_jiffies(tp->srtt_us >> (3 - 1));
+	else
+		timeout = TCP_TIMEOUT_INIT;
+	timeout += jiffies;
+
+	WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
+	smp_store_release(&icsk->icsk_ack.pending,
+			  icsk->icsk_ack.pending | ICSK_ACK_SCHED | ICSK_ACK_TIMER);
+	sk_reset_timer(ssk, &icsk->icsk_delack_timer, timeout);
+}
+
+void mptcp_subflow_process_delegated(struct sock *ssk, long status)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = subflow->conn;
+
+	if (status & BIT(MPTCP_DELEGATE_SEND)) {
+		mptcp_data_lock(sk);
+		if (!sock_owned_by_user(sk))
+			__mptcp_subflow_push_pending(sk, ssk, true);
+		else
+			__set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->cb_flags);
+		mptcp_data_unlock(sk);
+	}
+	if (status & BIT(MPTCP_DELEGATE_SNDBUF)) {
+		mptcp_data_lock(sk);
+		if (!sock_owned_by_user(sk))
+			__mptcp_sync_sndbuf(sk);
+		else
+			__set_bit(MPTCP_SYNC_SNDBUF, &mptcp_sk(sk)->cb_flags);
+		mptcp_data_unlock(sk);
+	}
+	if (status & BIT(MPTCP_DELEGATE_ACK))
+		schedule_3rdack_retransmission(ssk);
+}
+
+static int mptcp_hash(struct sock *sk)
+{
+	/* should never be called,
+	 * we hash the TCP subflows not the MPTCP socket
+	 */
+	WARN_ON_ONCE(1);
+	return 0;
+}
+
+static void mptcp_unhash(struct sock *sk)
+{
+	/* called from sk_common_release(), but nothing to do here */
+}
+
+static int mptcp_get_port(struct sock *sk, unsigned short snum)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p, ssk=%p\n", msk, msk->first);
+	if (WARN_ON_ONCE(!msk->first))
+		return -EINVAL;
+
+	return inet_csk_get_port(msk->first, snum);
+}
+
+void mptcp_finish_connect(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk;
+	struct sock *sk;
+
+	subflow = mptcp_subflow_ctx(ssk);
+	sk = subflow->conn;
+	msk = mptcp_sk(sk);
+
+	pr_debug("msk=%p, token=%u\n", sk, subflow->token);
+
+	subflow->map_seq = subflow->iasn;
+	subflow->map_subflow_seq = 1;
+
+	/* the socket is not connected yet, no msk/subflow ops can access/race
+	 * accessing the field below
+	 */
+	WRITE_ONCE(msk->local_key, subflow->local_key);
+	WRITE_ONCE(msk->rcvq_space.time, mptcp_stamp());
+
+	mptcp_pm_new_connection(msk, ssk, 0);
+}
+
+void mptcp_sock_graft(struct sock *sk, struct socket *parent)
+{
+	write_lock_bh(&sk->sk_callback_lock);
+	rcu_assign_pointer(sk->sk_wq, &parent->wq);
+	sk_set_socket(sk, parent);
+	write_unlock_bh(&sk->sk_callback_lock);
+}
+
+/* Can be called without holding the msk socket lock; use the callback lock
+ * to avoid {READ_,WRITE_}ONCE annotations on sk_socket.
+ */
+static void mptcp_sock_check_graft(struct sock *sk, struct sock *ssk)
+{
+	struct socket *sock;
+
+	write_lock_bh(&sk->sk_callback_lock);
+	sock = sk->sk_socket;
+	write_unlock_bh(&sk->sk_callback_lock);
+	if (sock) {
+		mptcp_sock_graft(ssk, sock);
+		__mptcp_inherit_cgrp_data(sk, ssk);
+		__mptcp_inherit_memcg(sk, ssk, GFP_ATOMIC);
+	}
+}
+
+bool mptcp_finish_join(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct sock *parent = (void *)msk;
+	bool ret = true;
+
+	pr_debug("msk=%p, subflow=%p\n", msk, subflow);
+
+	/* mptcp socket already closing? */
+	if (!mptcp_is_fully_established(parent)) {
+		MPTCP_INC_STATS(sock_net(parent), MPTCP_MIB_MPJOINNOTESTABLISHED);
+		subflow->reset_reason = MPTCP_RST_EMPTCP;
+		return false;
+	}
+
+	/* Active subflow, already present inside the conn_list; is grafted
+	 * either by __mptcp_subflow_connect() or accept.
+	 */
+	if (!list_empty(&subflow->node)) {
+		spin_lock_bh(&msk->fallback_lock);
+		if (!msk->allow_subflows) {
+			spin_unlock_bh(&msk->fallback_lock);
+			return false;
+		}
+		mptcp_subflow_joined(msk, ssk);
+		spin_unlock_bh(&msk->fallback_lock);
+		mptcp_propagate_sndbuf(parent, ssk);
+		return true;
+	}
+
+	if (!mptcp_pm_allow_new_subflow(msk)) {
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_JOINREJECTED);
+		goto err_prohibited;
+	}
+
+	/* If we can't acquire msk socket lock here, let the release callback
+	 * handle it
+	 */
+	mptcp_data_lock(parent);
+	if (!sock_owned_by_user(parent)) {
+		ret = __mptcp_finish_join(msk, ssk);
+		if (ret) {
+			sock_hold(ssk);
+			list_add_tail(&subflow->node, &msk->conn_list);
+			mptcp_sock_check_graft(parent, ssk);
+		}
+	} else {
+		sock_hold(ssk);
+		list_add_tail(&subflow->node, &msk->join_list);
+		__set_bit(MPTCP_FLUSH_JOIN_LIST, &msk->cb_flags);
+
+		/* In case of later failures, __mptcp_flush_join_list() will
+		 * properly orphan the ssk via mptcp_close_ssk().
+		 */
+		mptcp_sock_check_graft(parent, ssk);
+	}
+	mptcp_data_unlock(parent);
+
+	if (!ret) {
+		mptcp_pm_close_subflow(msk);
+err_prohibited:
+		subflow->reset_reason = MPTCP_RST_EPROHIBIT;
+		return false;
+	}
+
+	return true;
+}
+
+static void mptcp_shutdown(struct sock *sk, int how)
+{
+	pr_debug("sk=%p, how=%d\n", sk, how);
+
+	if ((how & SEND_SHUTDOWN) && mptcp_close_state(sk))
+		__mptcp_wr_shutdown(sk);
+}
+
+static int mptcp_ioctl_outq(const struct mptcp_sock *msk, u64 v)
+{
+	const struct sock *sk = (void *)msk;
+	u64 delta;
+
+	if (sk->sk_state == TCP_LISTEN)
+		return -EINVAL;
+
+	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
+		return 0;
+
+	delta = msk->write_seq - v;
+	if (__mptcp_check_fallback(msk) && msk->first) {
+		struct tcp_sock *tp = tcp_sk(msk->first);
+
+		/* the first subflow is disconnected after close - see
+		 * __mptcp_close_ssk(). tcp_disconnect() moves the write_seq
+		 * so ignore that status, too.
+		 */
+		if (!((1 << msk->first->sk_state) &
+		      (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_CLOSE)))
+			delta += READ_ONCE(tp->write_seq) - tp->snd_una;
+	}
+	if (delta > INT_MAX)
+		delta = INT_MAX;
+
+	return (int)delta;
+}
+
+static int mptcp_ioctl(struct sock *sk, int cmd, int *karg)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	bool slow;
+
+	switch (cmd) {
+	case SIOCINQ:
+		if (sk->sk_state == TCP_LISTEN)
+			return -EINVAL;
+
+		lock_sock(sk);
+		if (mptcp_move_skbs(sk))
+			mptcp_cleanup_rbuf(msk, 0);
+		*karg = mptcp_inq_hint(sk);
+		release_sock(sk);
+		break;
+	case SIOCOUTQ:
+		slow = lock_sock_fast(sk);
+		*karg = mptcp_ioctl_outq(msk, READ_ONCE(msk->snd_una));
+		unlock_sock_fast(sk, slow);
+		break;
+	case SIOCOUTQNSD:
+		slow = lock_sock_fast(sk);
+		*karg = mptcp_ioctl_outq(msk, msk->snd_nxt);
+		unlock_sock_fast(sk, slow);
+		break;
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return 0;
+}
+
+static int mptcp_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
+			 int addr_len)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	int err = -EINVAL;
+	struct sock *ssk;
+
+	ssk = __mptcp_nmpc_sk(msk);
+	if (IS_ERR(ssk))
+		return PTR_ERR(ssk);
+
+	set_bit(MPTCP_RTX_ENABLED, &msk->flags);
+	mptcp_set_state(sk, TCP_SYN_SENT);
+	subflow = mptcp_subflow_ctx(ssk);
+#ifdef CONFIG_TCP_MD5SIG
+	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
+	 * TCP option space.
+	 */
+	if (rcu_access_pointer(tcp_sk(ssk)->md5sig_info))
+		mptcp_early_fallback(msk, subflow, MPTCP_MIB_MD5SIGFALLBACK);
+#endif
+	if (subflow->request_mptcp) {
+		if (mptcp_active_should_disable(sk))
+			mptcp_early_fallback(msk, subflow,
+					     MPTCP_MIB_MPCAPABLEACTIVEDISABLED);
+		else if (mptcp_token_new_connect(ssk) < 0)
+			mptcp_early_fallback(msk, subflow,
+					     MPTCP_MIB_TOKENFALLBACKINIT);
+	}
+
+	WRITE_ONCE(msk->write_seq, subflow->idsn);
+	WRITE_ONCE(msk->snd_nxt, subflow->idsn);
+	WRITE_ONCE(msk->snd_una, subflow->idsn);
+	if (likely(!__mptcp_check_fallback(msk)))
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVE);
+
+	/* if reaching here via the fastopen/sendmsg path, the caller already
+	 * acquired the subflow socket lock, too.
+	 */
+	if (!msk->fastopening)
+		lock_sock(ssk);
+
+	/* the following mirrors closely a very small chunk of code from
+	 * __inet_stream_connect()
+	 */
+	if (ssk->sk_state != TCP_CLOSE)
+		goto out;
+
+	if (BPF_CGROUP_PRE_CONNECT_ENABLED(ssk)) {
+		err = ssk->sk_prot->pre_connect(ssk, uaddr, addr_len);
+		if (err)
+			goto out;
+	}
+
+	err = ssk->sk_prot->connect(ssk, uaddr, addr_len);
+	if (err < 0)
+		goto out;
+
+	inet_assign_bit(DEFER_CONNECT, sk, inet_test_bit(DEFER_CONNECT, ssk));
+
+out:
+	if (!msk->fastopening)
+		release_sock(ssk);
+
+	/* on successful connect, the msk state will be moved to established by
+	 * subflow_finish_connect()
+	 */
+	if (unlikely(err)) {
+		/* avoid leaving a dangling token in an unconnected socket */
+		mptcp_token_destroy(msk);
+		mptcp_set_state(sk, TCP_CLOSE);
+		return err;
+	}
+
+	mptcp_copy_inaddrs(sk, ssk);
+	return 0;
+}
+
+static struct proto mptcp_prot = {
+	.name		= "MPTCP",
+	.owner		= THIS_MODULE,
+	.init		= mptcp_init_sock,
+	.connect	= mptcp_connect,
+	.disconnect	= mptcp_disconnect,
+	.close		= mptcp_close,
+	.setsockopt	= mptcp_setsockopt,
+	.getsockopt	= mptcp_getsockopt,
+	.shutdown	= mptcp_shutdown,
+	.destroy	= mptcp_destroy,
+	.sendmsg	= mptcp_sendmsg,
+	.ioctl		= mptcp_ioctl,
+	.recvmsg	= mptcp_recvmsg,
+	.release_cb	= mptcp_release_cb,
+	.hash		= mptcp_hash,
+	.unhash		= mptcp_unhash,
+	.get_port	= mptcp_get_port,
+	.stream_memory_free	= mptcp_stream_memory_free,
+	.sockets_allocated	= &mptcp_sockets_allocated,
+
+	.memory_allocated	= &net_aligned_data.tcp_memory_allocated,
+	.per_cpu_fw_alloc	= &tcp_memory_per_cpu_fw_alloc,
+
+	.memory_pressure	= &tcp_memory_pressure,
+	.sysctl_wmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_wmem),
+	.sysctl_rmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_rmem),
+	.sysctl_mem	= sysctl_tcp_mem,
+	.obj_size	= sizeof(struct mptcp_sock),
+	.slab_flags	= SLAB_TYPESAFE_BY_RCU,
+	.no_autobind	= true,
+};
+
+static int mptcp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int addr_len)
+{
+	struct mptcp_sock *msk = mptcp_sk(sock->sk);
+	struct sock *ssk, *sk = sock->sk;
+	int err = -EINVAL;
+
+	lock_sock(sk);
+	ssk = __mptcp_nmpc_sk(msk);
+	if (IS_ERR(ssk)) {
+		err = PTR_ERR(ssk);
+		goto unlock;
+	}
+
+	if (sk->sk_family == AF_INET)
+		err = inet_bind_sk(ssk, uaddr, addr_len);
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (sk->sk_family == AF_INET6)
+		err = inet6_bind_sk(ssk, uaddr, addr_len);
+#endif
+	if (!err)
+		mptcp_copy_inaddrs(sk, ssk);
+
+unlock:
+	release_sock(sk);
+	return err;
+}
+
+static int mptcp_listen(struct socket *sock, int backlog)
+{
+	struct mptcp_sock *msk = mptcp_sk(sock->sk);
+	struct sock *sk = sock->sk;
+	struct sock *ssk;
+	int err;
+
+	pr_debug("msk=%p\n", msk);
+
+	lock_sock(sk);
+
+	err = -EINVAL;
+	if (sock->state != SS_UNCONNECTED || sock->type != SOCK_STREAM)
+		goto unlock;
+
+	ssk = __mptcp_nmpc_sk(msk);
+	if (IS_ERR(ssk)) {
+		err = PTR_ERR(ssk);
+		goto unlock;
+	}
+
+	set_bit(MPTCP_RTX_ENABLED, &msk->flags);
+	mptcp_set_state(sk, TCP_LISTEN);
+	sock_set_flag(sk, SOCK_RCU_FREE);
+
+	lock_sock(ssk);
+	err = __inet_listen_sk(ssk, backlog);
+	release_sock(ssk);
+	mptcp_set_state(sk, inet_sk_state_load(ssk));
+
+	if (!err) {
+		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
+		mptcp_copy_inaddrs(sk, ssk);
+		mptcp_event_pm_listener(ssk, MPTCP_EVENT_LISTENER_CREATED);
+	}
+
+unlock:
+	release_sock(sk);
+	return err;
+}
+
+static void mptcp_graft_subflows(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (mem_cgroup_sockets_enabled) {
+		LIST_HEAD(join_list);
+
+		/* Subflows joining after __inet_accept() will get the
+		 * mem CG properly initialized at mptcp_finish_join() time,
+		 * but subflows pending in join_list need explicit
+		 * initialization before flushing `backlog_unaccounted`
+		 * or MPTCP can later unexpectedly observe unaccounted memory.
+		 */
+		mptcp_data_lock(sk);
+		list_splice_init(&msk->join_list, &join_list);
+		mptcp_data_unlock(sk);
+
+		__mptcp_flush_join_list(sk, &join_list);
+	}
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		lock_sock(ssk);
+
+		/* Set ssk->sk_socket of accept()ed flows to mptcp socket.
+		 * This is needed so NOSPACE flag can be set from tcp stack.
+		 */
+		if (!ssk->sk_socket)
+			mptcp_sock_graft(ssk, sk->sk_socket);
+
+		if (!mem_cgroup_sk_enabled(sk))
+			goto unlock;
+
+		__mptcp_inherit_cgrp_data(sk, ssk);
+		__mptcp_inherit_memcg(sk, ssk, GFP_KERNEL);
+
+unlock:
+		release_sock(ssk);
+	}
+
+	if (mem_cgroup_sk_enabled(sk)) {
+		gfp_t gfp = GFP_KERNEL | __GFP_NOFAIL;
+		int amt;
+
+		/* Account the backlog memory; prior accept() is aware of
+		 * fwd and rmem only.
+		 */
+		mptcp_data_lock(sk);
+		amt = sk_mem_pages(sk->sk_forward_alloc +
+				   msk->backlog_unaccounted +
+				   atomic_read(&sk->sk_rmem_alloc)) -
+		      sk_mem_pages(sk->sk_forward_alloc +
+				   atomic_read(&sk->sk_rmem_alloc));
+		msk->backlog_unaccounted = 0;
+		mptcp_data_unlock(sk);
+
+		if (amt)
+			mem_cgroup_sk_charge(sk, amt, gfp);
+	}
+}
+
+static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
+			       struct proto_accept_arg *arg)
+{
+	struct mptcp_sock *msk = mptcp_sk(sock->sk);
+	struct sock *ssk, *newsk;
+
+	pr_debug("msk=%p\n", msk);
+
+	/* Buggy applications can call accept on socket states other then LISTEN
+	 * but no need to allocate the first subflow just to error out.
+	 */
+	ssk = READ_ONCE(msk->first);
+	if (!ssk)
+		return -EINVAL;
+
+	pr_debug("ssk=%p, listener=%p\n", ssk, mptcp_subflow_ctx(ssk));
+	newsk = inet_csk_accept(ssk, arg);
+	if (!newsk)
+		return arg->err;
+
+	pr_debug("newsk=%p, subflow is mptcp=%d\n", newsk, sk_is_mptcp(newsk));
+	if (sk_is_mptcp(newsk)) {
+		struct mptcp_subflow_context *subflow;
+		struct sock *new_mptcp_sock;
+
+		subflow = mptcp_subflow_ctx(newsk);
+		new_mptcp_sock = subflow->conn;
+
+		/* is_mptcp should be false if subflow->conn is missing, see
+		 * subflow_syn_recv_sock()
+		 */
+		if (WARN_ON_ONCE(!new_mptcp_sock)) {
+			tcp_sk(newsk)->is_mptcp = 0;
+			goto tcpfallback;
+		}
+
+		newsk = new_mptcp_sock;
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
+
+		newsk->sk_kern_sock = arg->kern;
+		lock_sock(newsk);
+		__inet_accept(sock, newsock, newsk);
+
+		set_bit(SOCK_CUSTOM_SOCKOPT, &newsock->flags);
+		msk = mptcp_sk(newsk);
+		msk->in_accept_queue = 0;
+
+		mptcp_graft_subflows(newsk);
+		mptcp_rps_record_subflows(msk);
+		__mptcp_propagate_sndbuf(newsk, mptcp_subflow_tcp_sock(subflow));
+
+		/* Do late cleanup for the first subflow as necessary. Also
+		 * deal with bad peers not doing a complete shutdown.
+		 */
+		if (unlikely(inet_sk_state_load(msk->first) == TCP_CLOSE)) {
+			if (unlikely(list_is_singular(&msk->conn_list)))
+				mptcp_set_state(newsk, TCP_CLOSE);
+			mptcp_close_ssk(newsk, msk->first,
+					mptcp_subflow_ctx(msk->first));
+		}
+	} else {
+tcpfallback:
+		newsk->sk_kern_sock = arg->kern;
+		lock_sock(newsk);
+		__inet_accept(sock, newsock, newsk);
+		/* we are being invoked after accepting a non-mp-capable
+		 * flow: sk is a tcp_sk, not an mptcp one.
+		 *
+		 * Hand the socket over to tcp so all further socket ops
+		 * bypass mptcp.
+		 */
+		WRITE_ONCE(newsock->sk->sk_socket->ops,
+			   mptcp_fallback_tcp_ops(newsock->sk));
+	}
+	release_sock(newsk);
+
+	return 0;
+}
+
+static __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+
+	if (__mptcp_stream_is_writeable(sk, 1))
+		return EPOLLOUT | EPOLLWRNORM;
+
+	set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+	smp_mb__after_atomic(); /* NOSPACE is changed by mptcp_write_space() */
+	if (__mptcp_stream_is_writeable(sk, 1))
+		return EPOLLOUT | EPOLLWRNORM;
+
+	return 0;
+}
+
+static __poll_t mptcp_poll(struct file *file, struct socket *sock,
+			   struct poll_table_struct *wait)
+{
+	struct sock *sk = sock->sk;
+	struct mptcp_sock *msk;
+	__poll_t mask = 0;
+	u8 shutdown;
+	int state;
+
+	msk = mptcp_sk(sk);
+	sock_poll_wait(file, sock, wait);
+
+	state = inet_sk_state_load(sk);
+	pr_debug("msk=%p state=%d flags=%lx\n", msk, state, msk->flags);
+	if (state == TCP_LISTEN) {
+		struct sock *ssk = READ_ONCE(msk->first);
+
+		if (WARN_ON_ONCE(!ssk))
+			return 0;
+
+		return inet_csk_listen_poll(ssk);
+	}
+
+	shutdown = READ_ONCE(sk->sk_shutdown);
+	if (shutdown == SHUTDOWN_MASK || state == TCP_CLOSE)
+		mask |= EPOLLHUP;
+	if (shutdown & RCV_SHUTDOWN)
+		mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
+
+	if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
+		mask |= mptcp_check_readable(sk);
+		if (shutdown & SEND_SHUTDOWN)
+			mask |= EPOLLOUT | EPOLLWRNORM;
+		else
+			mask |= mptcp_check_writeable(msk);
+	} else if (state == TCP_SYN_SENT &&
+		   inet_test_bit(DEFER_CONNECT, sk)) {
+		/* cf tcp_poll() note about TFO */
+		mask |= EPOLLOUT | EPOLLWRNORM;
+	}
+
+	/* This barrier is coupled with smp_wmb() in __mptcp_error_report() */
+	smp_rmb();
+	if (READ_ONCE(sk->sk_err))
+		mask |= EPOLLERR;
+
+	return mask;
+}
+
+static struct sk_buff *mptcp_recv_skb(struct sock *sk, u32 *off)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *skb;
+	u32 offset;
+
+	if (!list_empty(&msk->backlog_list))
+		mptcp_move_skbs(sk);
+
+	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
+		offset = MPTCP_SKB_CB(skb)->offset;
+		if (offset < skb->len) {
+			*off = offset;
+			return skb;
+		}
+		mptcp_eat_recv_skb(sk, skb);
+	}
+	return NULL;
+}
+
+/*
+ * Note:
+ *	- It is assumed that the socket was locked by the caller.
+ */
+static int __mptcp_read_sock(struct sock *sk, read_descriptor_t *desc,
+			     sk_read_actor_t recv_actor, bool noack)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sk_buff *skb;
+	int copied = 0;
+	u32 offset;
+
+	msk_owned_by_me(msk);
+
+	if (sk->sk_state == TCP_LISTEN)
+		return -ENOTCONN;
+	while ((skb = mptcp_recv_skb(sk, &offset)) != NULL) {
+		u32 data_len = skb->len - offset;
+		int count;
+		u32 size;
+
+		size = min_t(size_t, data_len, INT_MAX);
+		count = recv_actor(desc, skb, offset, size);
+		if (count <= 0) {
+			if (!copied)
+				copied = count;
+			break;
+		}
+
+		copied += count;
+
+		msk->bytes_consumed += count;
+		if (count < data_len) {
+			MPTCP_SKB_CB(skb)->offset += count;
+			MPTCP_SKB_CB(skb)->map_seq += count;
+			break;
+		}
+
+		mptcp_eat_recv_skb(sk, skb);
+		if (!desc->count)
+			break;
+	}
+
+	if (noack)
+		goto out;
+
+	mptcp_rcv_space_adjust(msk, copied);
+
+	if (copied > 0) {
+		mptcp_recv_skb(sk, &offset);
+		mptcp_cleanup_rbuf(msk, copied);
+	}
+out:
+	return copied;
+}
+
+static int mptcp_read_sock(struct sock *sk, read_descriptor_t *desc,
+			   sk_read_actor_t recv_actor)
+{
+	return __mptcp_read_sock(sk, desc, recv_actor, false);
+}
+
+static int __mptcp_splice_read(struct sock *sk, struct tcp_splice_state *tss)
+{
+	/* Store TCP splice context information in read_descriptor_t. */
+	read_descriptor_t rd_desc = {
+		.arg.data = tss,
+		.count	  = tss->len,
+	};
+
+	return mptcp_read_sock(sk, &rd_desc, tcp_splice_data_recv);
+}
+
+/**
+ *  mptcp_splice_read - splice data from MPTCP socket to a pipe
+ * @sock:	socket to splice from
+ * @ppos:	position (not valid)
+ * @pipe:	pipe to splice to
+ * @len:	number of bytes to splice
+ * @flags:	splice modifier flags
+ *
+ * Description:
+ *    Will read pages from given socket and fill them into a pipe.
+ *
+ * Return:
+ *    Amount of bytes that have been spliced.
+ *
+ **/
+static ssize_t mptcp_splice_read(struct socket *sock, loff_t *ppos,
+				 struct pipe_inode_info *pipe, size_t len,
+				 unsigned int flags)
+{
+	struct tcp_splice_state tss = {
+		.pipe	= pipe,
+		.len	= len,
+		.flags	= flags,
+	};
+	struct sock *sk = sock->sk;
+	ssize_t spliced = 0;
+	int ret = 0;
+	long timeo;
+
+	/*
+	 * We can't seek on a socket input
+	 */
+	if (unlikely(*ppos))
+		return -ESPIPE;
+
+	lock_sock(sk);
+
+	mptcp_rps_record_subflows(mptcp_sk(sk));
+
+	timeo = sock_rcvtimeo(sk, sock->file->f_flags & O_NONBLOCK);
+	while (tss.len) {
+		ret = __mptcp_splice_read(sk, &tss);
+		if (ret < 0) {
+			break;
+		} else if (!ret) {
+			if (spliced)
+				break;
+			if (sock_flag(sk, SOCK_DONE))
+				break;
+			if (sk->sk_err) {
+				ret = sock_error(sk);
+				break;
+			}
+			if (sk->sk_shutdown & RCV_SHUTDOWN)
+				break;
+			if (sk->sk_state == TCP_CLOSE) {
+				/*
+				 * This occurs when user tries to read
+				 * from never connected socket.
+				 */
+				ret = -ENOTCONN;
+				break;
+			}
+			if (!timeo) {
+				ret = -EAGAIN;
+				break;
+			}
+			/* if __mptcp_splice_read() got nothing while we have
+			 * an skb in receive queue, we do not want to loop.
+			 * This might happen with URG data.
+			 */
+			if (!skb_queue_empty(&sk->sk_receive_queue))
+				break;
+			ret = sk_wait_data(sk, &timeo, NULL);
+			if (ret < 0)
+				break;
+			if (signal_pending(current)) {
+				ret = sock_intr_errno(timeo);
+				break;
+			}
+			continue;
+		}
+		tss.len -= ret;
+		spliced += ret;
+
+		if (!tss.len || !timeo)
+			break;
+		release_sock(sk);
+		lock_sock(sk);
+
+		if (tcp_recv_should_stop(sk))
+			break;
+	}
+
+	release_sock(sk);
+
+	if (spliced)
+		return spliced;
+
+	return ret;
+}
+
+static const struct proto_ops mptcp_stream_ops = {
+	.family		   = PF_INET,
+	.owner		   = THIS_MODULE,
+	.release	   = inet_release,
+	.bind		   = mptcp_bind,
+	.connect	   = inet_stream_connect,
+	.socketpair	   = sock_no_socketpair,
+	.accept		   = mptcp_stream_accept,
+	.getname	   = inet_getname,
+	.poll		   = mptcp_poll,
+	.ioctl		   = inet_ioctl,
+	.gettstamp	   = sock_gettstamp,
+	.listen		   = mptcp_listen,
+	.shutdown	   = inet_shutdown,
+	.setsockopt	   = sock_common_setsockopt,
+	.getsockopt	   = sock_common_getsockopt,
+	.sendmsg	   = inet_sendmsg,
+	.recvmsg	   = inet_recvmsg,
+	.mmap		   = sock_no_mmap,
+	.set_rcvlowat	   = mptcp_set_rcvlowat,
+	.read_sock	   = mptcp_read_sock,
+	.splice_read	   = mptcp_splice_read,
+};
+
+static struct inet_protosw mptcp_protosw = {
+	.type		= SOCK_STREAM,
+	.protocol	= IPPROTO_MPTCP,
+	.prot		= &mptcp_prot,
+	.ops		= &mptcp_stream_ops,
+	.flags		= INET_PROTOSW_ICSK,
+};
+
+static int mptcp_napi_poll(struct napi_struct *napi, int budget)
+{
+	struct mptcp_delegated_action *delegated;
+	struct mptcp_subflow_context *subflow;
+	int work_done = 0;
+
+	delegated = container_of(napi, struct mptcp_delegated_action, napi);
+	while ((subflow = mptcp_subflow_delegated_next(delegated)) != NULL) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		bh_lock_sock_nested(ssk);
+		if (!sock_owned_by_user(ssk)) {
+			mptcp_subflow_process_delegated(ssk, xchg(&subflow->delegated_status, 0));
+		} else {
+			/* tcp_release_cb_override already processed
+			 * the action or will do at next release_sock().
+			 * In both case must dequeue the subflow here - on the same
+			 * CPU that scheduled it.
+			 */
+			smp_wmb();
+			clear_bit(MPTCP_DELEGATE_SCHEDULED, &subflow->delegated_status);
+		}
+		bh_unlock_sock(ssk);
+		sock_put(ssk);
+
+		if (++work_done == budget)
+			return budget;
+	}
+
+	/* always provide a 0 'work_done' argument, so that napi_complete_done
+	 * will not try accessing the NULL napi->dev ptr
+	 */
+	napi_complete_done(napi, 0);
+	return work_done;
+}
+
+void __init mptcp_proto_init(void)
+{
+	struct mptcp_delegated_action *delegated;
+	int cpu;
+
+	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;
+
+	if (percpu_counter_init(&mptcp_sockets_allocated, 0, GFP_KERNEL))
+		panic("Failed to allocate MPTCP pcpu counter\n");
+
+	mptcp_napi_dev = alloc_netdev_dummy(0);
+	if (!mptcp_napi_dev)
+		panic("Failed to allocate MPTCP dummy netdev\n");
+	for_each_possible_cpu(cpu) {
+		delegated = per_cpu_ptr(&mptcp_delegated_actions, cpu);
+		INIT_LIST_HEAD(&delegated->head);
+		netif_napi_add_tx(mptcp_napi_dev, &delegated->napi,
+				  mptcp_napi_poll);
+		napi_enable(&delegated->napi);
+	}
+
+	mptcp_subflow_init();
+	mptcp_pm_init();
+	mptcp_sched_init();
+	mptcp_token_init();
+
+	if (proto_register(&mptcp_prot, 1) != 0)
+		panic("Failed to register MPTCP proto.\n");
+
+	inet_register_protosw(&mptcp_protosw);
+
+	BUILD_BUG_ON(sizeof(struct mptcp_skb_cb) > sizeof_field(struct sk_buff, cb));
+
+	/* struct mptcp_data_frag: 'overhead' corresponds to the alignment
+	 * (ALIGN(1, sizeof(long)) - 1, so 8-1) + the struct's size
+	 */
+	BUILD_BUG_ON(ALIGN(1, sizeof(long)) - 1 + sizeof(struct mptcp_data_frag)
+		     > U8_MAX);
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static const struct proto_ops mptcp_v6_stream_ops = {
+	.family		   = PF_INET6,
+	.owner		   = THIS_MODULE,
+	.release	   = inet6_release,
+	.bind		   = mptcp_bind,
+	.connect	   = inet_stream_connect,
+	.socketpair	   = sock_no_socketpair,
+	.accept		   = mptcp_stream_accept,
+	.getname	   = inet6_getname,
+	.poll		   = mptcp_poll,
+	.ioctl		   = inet6_ioctl,
+	.gettstamp	   = sock_gettstamp,
+	.listen		   = mptcp_listen,
+	.shutdown	   = inet_shutdown,
+	.setsockopt	   = sock_common_setsockopt,
+	.getsockopt	   = sock_common_getsockopt,
+	.sendmsg	   = inet6_sendmsg,
+	.recvmsg	   = inet6_recvmsg,
+	.mmap		   = sock_no_mmap,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	   = inet6_compat_ioctl,
+#endif
+	.set_rcvlowat	   = mptcp_set_rcvlowat,
+	.read_sock	   = mptcp_read_sock,
+	.splice_read	   = mptcp_splice_read,
+};
+
+static struct proto mptcp_v6_prot;
+
+static struct inet_protosw mptcp_v6_protosw = {
+	.type		= SOCK_STREAM,
+	.protocol	= IPPROTO_MPTCP,
+	.prot		= &mptcp_v6_prot,
+	.ops		= &mptcp_v6_stream_ops,
+	.flags		= INET_PROTOSW_ICSK,
+};
+
+int __init mptcp_proto_v6_init(void)
+{
+	int err;
+
+	mptcp_subflow_v6_init();
+
+	mptcp_v6_prot = mptcp_prot;
+	strscpy(mptcp_v6_prot.name, "MPTCPv6", sizeof(mptcp_v6_prot.name));
+	mptcp_v6_prot.slab = NULL;
+	mptcp_v6_prot.obj_size = sizeof(struct mptcp6_sock);
+	mptcp_v6_prot.ipv6_pinfo_offset = offsetof(struct mptcp6_sock, np);
+
+	err = proto_register(&mptcp_v6_prot, 1);
+	if (err)
+		return err;
+
+	err = inet6_register_protosw(&mptcp_v6_protosw);
+	if (err)
+		proto_unregister(&mptcp_v6_prot);
+
+	return err;
+}
+#endif
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
new file mode 100644
index 000000000..2b4c27426
--- /dev/null
+++ b/net/mptcp/protocol.h
@@ -0,0 +1,1384 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Multipath TCP
+ *
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ */
+
+#ifndef __MPTCP_PROTOCOL_H
+#define __MPTCP_PROTOCOL_H
+
+#include <linux/random.h>
+#include <net/tcp.h>
+#include <net/inet_connection_sock.h>
+#include <uapi/linux/mptcp.h>
+#include <net/genetlink.h>
+#include <net/rstreason.h>
+
+#define MPTCP_SUPPORTED_VERSION	1
+
+/* MPTCP option bits */
+#define OPTION_MPTCP_MPC_SYN	BIT(0)
+#define OPTION_MPTCP_MPC_SYNACK	BIT(1)
+#define OPTION_MPTCP_MPC_ACK	BIT(2)
+#define OPTION_MPTCP_MPJ_SYN	BIT(3)
+#define OPTION_MPTCP_MPJ_SYNACK	BIT(4)
+#define OPTION_MPTCP_MPJ_ACK	BIT(5)
+#define OPTION_MPTCP_ADD_ADDR	BIT(6)
+#define OPTION_MPTCP_RM_ADDR	BIT(7)
+#define OPTION_MPTCP_FASTCLOSE	BIT(8)
+#define OPTION_MPTCP_PRIO	BIT(9)
+#define OPTION_MPTCP_RST	BIT(10)
+#define OPTION_MPTCP_DSS	BIT(11)
+#define OPTION_MPTCP_FAIL	BIT(12)
+
+#define OPTION_MPTCP_CSUMREQD	BIT(13)
+
+#define OPTIONS_MPTCP_MPC	(OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK | \
+				 OPTION_MPTCP_MPC_ACK)
+#define OPTIONS_MPTCP_MPJ	(OPTION_MPTCP_MPJ_SYN | OPTION_MPTCP_MPJ_SYNACK | \
+				 OPTION_MPTCP_MPJ_ACK)
+#define OPTIONS_MPTCP_DSS	(OPTION_MPTCP_DSS | OPTION_MPTCP_CSUMREQD)
+
+/* MPTCP option subtypes */
+#define MPTCPOPT_MP_CAPABLE	0
+#define MPTCPOPT_MP_JOIN	1
+#define MPTCPOPT_DSS		2
+#define MPTCPOPT_ADD_ADDR	3
+#define MPTCPOPT_RM_ADDR	4
+#define MPTCPOPT_MP_PRIO	5
+#define MPTCPOPT_MP_FAIL	6
+#define MPTCPOPT_MP_FASTCLOSE	7
+#define MPTCPOPT_RST		8
+
+/* MPTCP suboption lengths */
+#define TCPOLEN_MPTCP_MPC_SYN		4
+#define TCPOLEN_MPTCP_MPC_SYNACK	12
+#define TCPOLEN_MPTCP_MPC_ACK		20
+#define TCPOLEN_MPTCP_MPC_ACK_DATA	22
+#define TCPOLEN_MPTCP_MPJ_SYN		12
+#define TCPOLEN_MPTCP_MPJ_SYNACK	16
+#define TCPOLEN_MPTCP_MPJ_ACK		24
+#define TCPOLEN_MPTCP_DSS_BASE		4
+#define TCPOLEN_MPTCP_DSS_ACK32		4
+#define TCPOLEN_MPTCP_DSS_ACK64		8
+#define TCPOLEN_MPTCP_DSS_MAP32		10
+#define TCPOLEN_MPTCP_DSS_MAP64		14
+#define TCPOLEN_MPTCP_DSS_CHECKSUM	2
+#define TCPOLEN_MPTCP_ADD_ADDR		16
+#define TCPOLEN_MPTCP_ADD_ADDR_PORT	18
+#define TCPOLEN_MPTCP_ADD_ADDR_BASE	8
+#define TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT	10
+#define TCPOLEN_MPTCP_ADD_ADDR6		28
+#define TCPOLEN_MPTCP_ADD_ADDR6_PORT	30
+#define TCPOLEN_MPTCP_ADD_ADDR6_BASE	20
+#define TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT	22
+#define TCPOLEN_MPTCP_PORT_LEN		2
+#define TCPOLEN_MPTCP_PORT_ALIGN	2
+#define TCPOLEN_MPTCP_RM_ADDR_BASE	3
+#define TCPOLEN_MPTCP_PRIO		3
+#define TCPOLEN_MPTCP_PRIO_ALIGN	4
+#define TCPOLEN_MPTCP_FASTCLOSE		12
+#define TCPOLEN_MPTCP_RST		4
+#define TCPOLEN_MPTCP_FAIL		12
+
+#define TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM	(TCPOLEN_MPTCP_DSS_CHECKSUM + TCPOLEN_MPTCP_MPC_ACK_DATA)
+
+/* MPTCP MP_JOIN flags */
+#define MPTCPOPT_BACKUP		BIT(0)
+#define MPTCPOPT_THMAC_LEN	8
+
+/* MPTCP MP_CAPABLE flags */
+#define MPTCP_VERSION_MASK	(0x0F)
+#define MPTCP_CAP_CHECKSUM_REQD	BIT(7)
+#define MPTCP_CAP_EXTENSIBILITY	BIT(6)
+#define MPTCP_CAP_DENY_JOIN_ID0	BIT(5)
+#define MPTCP_CAP_HMAC_SHA256	BIT(0)
+#define MPTCP_CAP_FLAG_MASK	(0x1F)
+
+/* MPTCP DSS flags */
+#define MPTCP_DSS_DATA_FIN	BIT(4)
+#define MPTCP_DSS_DSN64		BIT(3)
+#define MPTCP_DSS_HAS_MAP	BIT(2)
+#define MPTCP_DSS_ACK64		BIT(1)
+#define MPTCP_DSS_HAS_ACK	BIT(0)
+#define MPTCP_DSS_FLAG_MASK	(0x1F)
+
+/* MPTCP ADD_ADDR flags */
+#define MPTCP_ADDR_ECHO		BIT(0)
+
+/* MPTCP MP_PRIO flags */
+#define MPTCP_PRIO_BKUP		BIT(0)
+
+/* MPTCP TCPRST flags */
+#define MPTCP_RST_TRANSIENT	BIT(0)
+
+/* MPTCP socket atomic flags */
+#define MPTCP_WORK_RTX		1
+#define MPTCP_FALLBACK_DONE	2
+#define MPTCP_WORK_CLOSE_SUBFLOW 3
+#define MPTCP_RTX_ENABLED	4
+
+/* MPTCP socket release cb flags */
+#define MPTCP_PUSH_PENDING	1
+#define MPTCP_CLEAN_UNA		2
+#define MPTCP_ERROR_REPORT	3
+#define MPTCP_RETRANSMIT	4
+#define MPTCP_FLUSH_JOIN_LIST	5
+#define MPTCP_SYNC_STATE	6
+#define MPTCP_SYNC_SNDBUF	7
+
+struct mptcp_skb_cb {
+	u64 map_seq;
+	u64 end_seq;
+	u32 offset;
+	u8  has_rxtstamp;
+	u8  cant_coalesce;
+};
+
+#define MPTCP_SKB_CB(__skb)	((struct mptcp_skb_cb *)&((__skb)->cb[0]))
+
+static inline bool before64(__u64 seq1, __u64 seq2)
+{
+	return (__s64)(seq1 - seq2) < 0;
+}
+
+#define after64(seq2, seq1)	before64(seq1, seq2)
+
+struct mptcp_options_received {
+	u64	sndr_key;
+	u64	rcvr_key;
+	u64	data_ack;
+	u64	data_seq;
+	u32	subflow_seq;
+	u16	data_len;
+	__sum16	csum;
+	struct_group(status,
+		u16 suboptions;
+		u16 use_map:1,
+		    dsn64:1,
+		    data_fin:1,
+		    use_ack:1,
+		    ack64:1,
+		    mpc_map:1,
+		    reset_reason:4,
+		    reset_transient:1,
+		    echo:1,
+		    backup:1,
+		    deny_join_id0:1,
+		    __unused:2;
+	);
+	u8	join_id;
+	u32	token;
+	u32	nonce;
+	u64	thmac;
+	u8	hmac[MPTCPOPT_HMAC_LEN];
+	struct mptcp_addr_info addr;
+	struct mptcp_rm_list rm_list;
+	u64	ahmac;
+	u64	fail_seq;
+};
+
+static inline __be32 mptcp_option(u8 subopt, u8 len, u8 nib, u8 field)
+{
+	return htonl((TCPOPT_MPTCP << 24) | (len << 16) | (subopt << 12) |
+		     ((nib & 0xF) << 8) | field);
+}
+
+enum mptcp_pm_status {
+	MPTCP_PM_ADD_ADDR_RECEIVED,
+	MPTCP_PM_ADD_ADDR_SEND_ACK,
+	MPTCP_PM_RM_ADDR_RECEIVED,
+	MPTCP_PM_ESTABLISHED,
+	MPTCP_PM_SUBFLOW_ESTABLISHED,
+	MPTCP_PM_ALREADY_ESTABLISHED,	/* persistent status, set after ESTABLISHED event */
+	MPTCP_PM_MPC_ENDPOINT_ACCOUNTED, /* persistent status, set after MPC local address is
+					  * accounted int id_avail_bitmap
+					  */
+	MPTCP_PM_DESTROYING,		/* To fence out PM list allocs */
+};
+
+enum mptcp_pm_type {
+	MPTCP_PM_TYPE_KERNEL = 0,
+	MPTCP_PM_TYPE_USERSPACE,
+
+	__MPTCP_PM_TYPE_NR,
+	__MPTCP_PM_TYPE_MAX = __MPTCP_PM_TYPE_NR - 1,
+};
+
+/* Status bits below MPTCP_PM_ALREADY_ESTABLISHED need pm worker actions */
+#define MPTCP_PM_WORK_MASK ((1 << MPTCP_PM_ALREADY_ESTABLISHED) - 1)
+
+enum mptcp_addr_signal_status {
+	MPTCP_ADD_ADDR_SIGNAL,
+	MPTCP_ADD_ADDR_ECHO,
+	MPTCP_RM_ADDR_SIGNAL,
+};
+
+/* max value of mptcp_addr_info.id */
+#define MPTCP_PM_MAX_ADDR_ID		U8_MAX
+
+struct mptcp_pm_data {
+	struct mptcp_addr_info local;
+	struct mptcp_addr_info remote;
+	struct list_head anno_list;
+	struct list_head userspace_pm_local_addr_list;
+
+	spinlock_t	lock;		/*protects the whole PM data */
+
+	struct_group(reset,
+
+	u8		addr_signal;
+	bool		server_side;
+	bool		work_pending;
+	bool		accept_addr;
+	bool		accept_subflow;
+	bool		remote_deny_join_id0;
+	u8		add_addr_signaled;
+	u8		add_addr_accepted;
+	u8		local_addr_used;
+	u8		pm_type;
+	u8		extra_subflows;
+	u8		status;
+
+	);
+
+	DECLARE_BITMAP(id_avail_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
+	struct mptcp_rm_list rm_list_tx;
+	struct mptcp_rm_list rm_list_rx;
+};
+
+struct mptcp_pm_local {
+	struct mptcp_addr_info	addr;
+	u32			flags;
+	int			ifindex;
+};
+
+struct mptcp_pm_addr_entry {
+	struct list_head	list;
+	struct mptcp_addr_info	addr;
+	u32			flags;
+	int			ifindex;
+	struct socket		*lsk;
+};
+
+struct mptcp_data_frag {
+	struct list_head list;
+	u64 data_seq;
+	u16 data_len;
+	u16 offset;
+	u8 overhead;
+	u8 eor;			/* currently using 1 bit */
+	u16 already_sent;
+	struct page *page;
+};
+
+/* Arbitrary compromise between as low as possible to react timely to subflow
+ * close event and as big as possible to avoid being fouled by biased large
+ * samples due to peer sending data on a different subflow WRT to the incoming
+ * ack.
+ */
+#define MPTCP_RTT_SAMPLES	5
+
+/* MPTCP connection sock */
+struct mptcp_sock {
+	/* inet_connection_sock must be the first member */
+	struct inet_connection_sock sk;
+	u64		local_key;		/* protected by the first subflow socket lock
+						 * lockless access read
+						 */
+	u64		remote_key;		/* same as above */
+	u64		write_seq;
+	u64		bytes_sent;
+	u64		snd_nxt;
+	u64		bytes_received;
+	u64		ack_seq;
+	atomic64_t	rcv_wnd_sent;
+	u64		rcv_data_fin_seq;
+	u64		bytes_retrans;
+	u64		bytes_consumed;
+	int		snd_burst;
+	int		old_wspace;
+	u64		recovery_snd_nxt;	/* in recovery mode accept up to this seq;
+						 * recovery related fields are under data_lock
+						 * protection
+						 */
+	u64		bytes_acked;
+	u64		snd_una;
+	u64		wnd_end;
+	u32		last_data_sent;
+	u32		last_data_recv;
+	u32		last_ack_recv;
+	unsigned long	timer_ival;
+	u32		token;
+	unsigned long	flags;
+	unsigned long	cb_flags;
+	bool		recovery;		/* closing subflow write queue reinjected */
+	bool		can_ack;
+	bool		fully_established;
+	bool		rcv_data_fin;
+	bool		snd_data_fin_enable;
+	bool		rcv_fastclose;
+	bool		use_64bit_ack; /* Set when we received a 64-bit DSN */
+	bool		csum_enabled;
+	bool		allow_infinite_fallback;
+	u8		pending_state; /* A subflow asked to set this sk_state,
+					* protected by the msk data lock
+					*/
+	u8		mpc_endpoint_id;
+	u8		recvmsg_inq:1,
+			cork:1,
+			nodelay:1,
+			fastopening:1,
+			in_accept_queue:1,
+			free_first:1,
+			rcvspace_init:1,
+			fastclosing:1;
+	u32		notsent_lowat;
+	int		keepalive_cnt;
+	int		keepalive_idle;
+	int		keepalive_intvl;
+	int		maxseg;
+	struct work_struct work;
+	struct sk_buff  *ooo_last_skb;
+	struct rb_root  out_of_order_queue;
+	struct list_head conn_list;
+	struct list_head rtx_queue;
+	struct mptcp_data_frag *first_pending;
+	struct list_head join_list;
+	struct sock	*first; /* The mptcp ops can safely dereference, using suitable
+				 * ONCE annotation, the subflow outside the socket
+				 * lock as such sock is freed after close().
+				 */
+	struct mptcp_pm_data	pm;
+	struct mptcp_sched_ops	*sched;
+
+	/* Most recent rtt_us observed by in use incoming subflows. */
+	struct {
+		u32	samples[MPTCP_RTT_SAMPLES];
+		u32	next_sample;
+	} rcv_rtt_est;
+
+	struct {
+		int	space;	/* bytes copied in last measurement window */
+		int	copied; /* bytes copied in this measurement window */
+		u64	time;	/* start time of measurement window */
+	} rcvq_space;
+	u8		scaling_ratio;
+	bool		allow_subflows;
+
+	u32		subflow_id;
+	u32		setsockopt_seq;
+	char		ca_name[TCP_CA_NAME_MAX];
+
+	spinlock_t	fallback_lock;	/* protects fallback,
+					 * allow_infinite_fallback and
+					 * allow_join
+					 */
+
+	struct list_head backlog_list;	/* protected by the data lock */
+	u32		backlog_len;
+	u32		backlog_unaccounted;
+};
+
+#define mptcp_data_lock(sk) spin_lock_bh(&(sk)->sk_lock.slock)
+#define mptcp_data_unlock(sk) spin_unlock_bh(&(sk)->sk_lock.slock)
+
+#define mptcp_for_each_subflow(__msk, __subflow)			\
+	list_for_each_entry(__subflow, &((__msk)->conn_list), node)
+#define mptcp_for_each_subflow_safe(__msk, __subflow, __tmp)			\
+	list_for_each_entry_safe(__subflow, __tmp, &((__msk)->conn_list), node)
+#define mptcp_next_subflow(__msk, __subflow)				\
+	list_next_entry_circular(__subflow, &((__msk)->conn_list), node)
+
+extern struct genl_family mptcp_genl_family;
+
+static inline void msk_owned_by_me(const struct mptcp_sock *msk)
+{
+	sock_owned_by_me((const struct sock *)msk);
+}
+
+#ifdef CONFIG_DEBUG_NET
+/* MPTCP-specific: we might (indirectly) call this helper with the wrong sk */
+#undef tcp_sk
+#define tcp_sk(ptr) ({								\
+	typeof(ptr) _ptr = (ptr);						\
+	WARN_ON(_ptr->sk_protocol != IPPROTO_TCP);				\
+	container_of_const(_ptr, struct tcp_sock, inet_conn.icsk_inet.sk);	\
+})
+#define mptcp_sk(ptr) ({						\
+	typeof(ptr) _ptr = (ptr);					\
+	WARN_ON(_ptr->sk_protocol != IPPROTO_MPTCP);			\
+	container_of_const(_ptr, struct mptcp_sock, sk.icsk_inet.sk);	\
+})
+
+#else /* !CONFIG_DEBUG_NET */
+#define mptcp_sk(ptr) container_of_const(ptr, struct mptcp_sock, sk.icsk_inet.sk)
+#endif
+
+static inline int mptcp_win_from_space(const struct sock *sk, int space)
+{
+	return __tcp_win_from_space(mptcp_sk(sk)->scaling_ratio, space);
+}
+
+static inline int mptcp_space_from_win(const struct sock *sk, int win)
+{
+	return __tcp_space_from_win(mptcp_sk(sk)->scaling_ratio, win);
+}
+
+static inline int __mptcp_space(const struct sock *sk)
+{
+	return mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) -
+				    READ_ONCE(mptcp_sk(sk)->backlog_len) -
+				    sk_rmem_alloc_get(sk));
+}
+
+static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *sk)
+{
+	const struct mptcp_sock *msk = mptcp_sk(sk);
+
+	return msk->first_pending;
+}
+
+static inline void mptcp_init_rtt_est(struct mptcp_sock *msk)
+{
+	int i;
+
+	for (i = 0; i < MPTCP_RTT_SAMPLES; ++i)
+		msk->rcv_rtt_est.samples[i] = U32_MAX;
+	msk->rcv_rtt_est.next_sample = 0;
+	msk->scaling_ratio = TCP_DEFAULT_SCALING_RATIO;
+}
+
+static inline u32 mptcp_rtt_us_est(const struct mptcp_sock *msk)
+{
+	u32 rtt_us = READ_ONCE(msk->rcv_rtt_est.samples[0]);
+	int i;
+
+	/* Lockless access of collected samples. */
+	for (i = 1; i < MPTCP_RTT_SAMPLES; ++i)
+		rtt_us = min(rtt_us, READ_ONCE(msk->rcv_rtt_est.samples[i]));
+	return rtt_us;
+}
+
+static inline struct mptcp_data_frag *mptcp_send_next(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_data_frag *cur;
+
+	cur = msk->first_pending;
+	return list_is_last(&cur->list, &msk->rtx_queue) ? NULL :
+						     list_next_entry(cur, list);
+}
+
+static inline struct mptcp_data_frag *mptcp_pending_tail(const struct sock *sk)
+{
+	const struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (!msk->first_pending)
+		return NULL;
+
+	if (WARN_ON_ONCE(list_empty(&msk->rtx_queue)))
+		return NULL;
+
+	return list_last_entry(&msk->rtx_queue, struct mptcp_data_frag, list);
+}
+
+static inline struct mptcp_data_frag *mptcp_rtx_head(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (msk->snd_una == msk->snd_nxt)
+		return NULL;
+
+	return list_first_entry_or_null(&msk->rtx_queue, struct mptcp_data_frag, list);
+}
+
+struct csum_pseudo_header {
+	__be64 data_seq;
+	__be32 subflow_seq;
+	__be16 data_len;
+	__sum16 csum;
+};
+
+struct mptcp_subflow_request_sock {
+	struct	tcp_request_sock sk;
+	u16	mp_capable : 1,
+		mp_join : 1,
+		backup : 1,
+		request_bkup : 1,
+		csum_reqd : 1,
+		allow_join_id0 : 1;
+	u8	local_id;
+	u8	remote_id;
+	u64	local_key;
+	u64	idsn;
+	u32	token;
+	u32	ssn_offset;
+	u64	thmac;
+	u32	local_nonce;
+	u32	remote_nonce;
+	struct mptcp_sock	*msk;
+	struct hlist_nulls_node token_node;
+};
+
+static inline struct mptcp_subflow_request_sock *
+mptcp_subflow_rsk(const struct request_sock *rsk)
+{
+	return (struct mptcp_subflow_request_sock *)rsk;
+}
+
+struct mptcp_delegated_action {
+	struct napi_struct napi;
+	local_lock_t bh_lock;
+	struct list_head head;
+};
+
+DECLARE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions);
+
+#define MPTCP_DELEGATE_SCHEDULED	0
+#define MPTCP_DELEGATE_SEND		1
+#define MPTCP_DELEGATE_ACK		2
+#define MPTCP_DELEGATE_SNDBUF		3
+
+#define MPTCP_DELEGATE_ACTIONS_MASK	(~BIT(MPTCP_DELEGATE_SCHEDULED))
+/* MPTCP subflow context */
+struct mptcp_subflow_context {
+	struct	list_head node;/* conn_list of subflows */
+
+	struct_group(reset,
+
+	unsigned long avg_pacing_rate; /* protected by msk socket lock */
+	u64	local_key;
+	u64	remote_key;
+	u64	idsn;
+	u64	map_seq;
+	u64	rcv_wnd_sent;
+	u32	snd_isn;
+	u32	token;
+	u32	rel_write_seq;
+	u32	map_subflow_seq;
+	u32	ssn_offset;
+	u32	map_data_len;
+	__wsum	map_data_csum;
+	u32	map_csum_len;
+	u32	prev_rtt_seq;
+	u32	request_mptcp : 1,  /* send MP_CAPABLE */
+		request_join : 1,   /* send MP_JOIN */
+		request_bkup : 1,
+		mp_capable : 1,	    /* remote is MPTCP capable */
+		mp_join : 1,	    /* remote is JOINing */
+		pm_notified : 1,    /* PM hook called for established status */
+		conn_finished : 1,
+		map_valid : 1,
+		map_csum_reqd : 1,
+		map_data_fin : 1,
+		mpc_map : 1,
+		backup : 1,
+		send_mp_prio : 1,
+		send_mp_fail : 1,
+		send_fastclose : 1,
+		send_infinite_map : 1,
+		remote_key_valid : 1,        /* received the peer key from */
+		disposable : 1,	    /* ctx can be free at ulp release time */
+		closing : 1,	    /* must not pass rx data to msk anymore */
+		valid_csum_seen : 1,        /* at least one csum validated */
+		is_mptfo : 1,	    /* subflow is doing TFO */
+		close_event_done : 1,       /* has done the post-closed part */
+		mpc_drop : 1,	    /* the MPC option has been dropped in a rtx */
+		__unused : 9;
+	bool	data_avail;
+	bool	scheduled;
+	bool	pm_listener;	    /* a listener managed by the kernel PM? */
+	bool	fully_established;  /* path validated */
+	u32	lent_mem_frag;
+	u32	remote_nonce;
+	u64	thmac;
+	u32	local_nonce;
+	u32	remote_token;
+	union {
+		u8	hmac[MPTCPOPT_HMAC_LEN]; /* MPJ subflow only */
+		u64	iasn;	    /* initial ack sequence number, MPC subflows only */
+	};
+	s16	local_id;	    /* if negative not initialized yet */
+	u8	remote_id;
+	u8	reset_seen:1;
+	u8	reset_transient:1;
+	u8	reset_reason:4;
+	u8	stale_count;	    /* Protected by the msk socket lock */
+	u8	stale;		    /* Protected by the msk socket lock,
+				     * if set the subflow is unable to snd/rcv
+				     * data, the schedule should skip it
+				     */
+
+	u32	subflow_id;
+
+	long	delegated_status;
+	unsigned long	fail_tout;
+
+	);
+
+	struct	list_head delegated_node;   /* link into delegated_action, protected by local BH */
+
+	u32	setsockopt_seq;
+	u32	stale_rcv_tstamp;
+	int     cached_sndbuf;	    /* sndbuf size when last synced with the msk sndbuf,
+				     * protected by the msk socket lock
+				     */
+
+	struct	sock *tcp_sock;	    /* tcp sk backpointer */
+	struct	sock *conn;	    /* parent mptcp_sock */
+	const	struct inet_connection_sock_af_ops *icsk_af_ops;
+	void	(*tcp_state_change)(struct sock *sk);
+	void	(*tcp_error_report)(struct sock *sk);
+
+	struct	rcu_head rcu;
+};
+
+static inline struct mptcp_subflow_context *
+mptcp_subflow_ctx(const struct sock *sk)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+
+	/* Use RCU on icsk_ulp_data only for sock diag code */
+	return (__force struct mptcp_subflow_context *)icsk->icsk_ulp_data;
+}
+
+static inline struct sock *
+mptcp_subflow_tcp_sock(const struct mptcp_subflow_context *subflow)
+{
+	return subflow->tcp_sock;
+}
+
+static inline void
+mptcp_subflow_ctx_reset(struct mptcp_subflow_context *subflow)
+{
+	memset(&subflow->reset, 0, sizeof(subflow->reset));
+	subflow->request_mptcp = 1;
+	WRITE_ONCE(subflow->local_id, -1);
+}
+
+/* Convert reset reasons in MPTCP to enum sk_rst_reason type */
+static inline enum sk_rst_reason
+sk_rst_convert_mptcp_reason(u32 reason)
+{
+	switch (reason) {
+	case MPTCP_RST_EUNSPEC:
+		return SK_RST_REASON_MPTCP_RST_EUNSPEC;
+	case MPTCP_RST_EMPTCP:
+		return SK_RST_REASON_MPTCP_RST_EMPTCP;
+	case MPTCP_RST_ERESOURCE:
+		return SK_RST_REASON_MPTCP_RST_ERESOURCE;
+	case MPTCP_RST_EPROHIBIT:
+		return SK_RST_REASON_MPTCP_RST_EPROHIBIT;
+	case MPTCP_RST_EWQ2BIG:
+		return SK_RST_REASON_MPTCP_RST_EWQ2BIG;
+	case MPTCP_RST_EBADPERF:
+		return SK_RST_REASON_MPTCP_RST_EBADPERF;
+	case MPTCP_RST_EMIDDLEBOX:
+		return SK_RST_REASON_MPTCP_RST_EMIDDLEBOX;
+	default:
+		/* It should not happen, or else errors may occur
+		 * in MPTCP layer
+		 */
+		return SK_RST_REASON_ERROR;
+	}
+}
+
+static inline void
+mptcp_send_active_reset_reason(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	enum sk_rst_reason reason;
+
+	reason = sk_rst_convert_mptcp_reason(subflow->reset_reason);
+	tcp_send_active_reset(sk, reason);
+}
+
+/* Made the fwd mem carried by the given skb available to the msk,
+ * To be paired with a previous mptcp_subflow_lend_fwdmem() before freeing
+ * the skb or setting the skb ownership.
+ */
+static inline void mptcp_borrow_fwdmem(struct sock *sk, struct sk_buff *skb)
+{
+	struct sock *ssk = skb->sk;
+
+	/* The subflow just lend the skb fwd memory; if the subflow meanwhile
+	 * closed, mptcp_close_ssk() already released the ssk rcv memory.
+	 */
+	DEBUG_NET_WARN_ON_ONCE(skb->destructor);
+	sk_forward_alloc_add(sk, skb->truesize);
+	if (!ssk)
+		return;
+
+	atomic_sub(skb->truesize, &ssk->sk_rmem_alloc);
+	skb->sk = NULL;
+}
+
+static inline void
+__mptcp_subflow_lend_fwdmem(struct mptcp_subflow_context *subflow, int size)
+{
+	int frag = (subflow->lent_mem_frag + size) & (PAGE_SIZE - 1);
+
+	subflow->lent_mem_frag = frag;
+}
+
+static inline void
+mptcp_subflow_lend_fwdmem(struct mptcp_subflow_context *subflow,
+			  struct sk_buff *skb)
+{
+	__mptcp_subflow_lend_fwdmem(subflow, skb->truesize);
+	skb->destructor = NULL;
+}
+
+static inline u64
+mptcp_subflow_get_map_offset(const struct mptcp_subflow_context *subflow)
+{
+	return tcp_sk(mptcp_subflow_tcp_sock(subflow))->copied_seq -
+		      subflow->ssn_offset -
+		      subflow->map_subflow_seq;
+}
+
+static inline u64
+mptcp_subflow_get_mapped_dsn(const struct mptcp_subflow_context *subflow)
+{
+	return subflow->map_seq + mptcp_subflow_get_map_offset(subflow);
+}
+
+void mptcp_subflow_process_delegated(struct sock *ssk, long actions);
+
+static inline void mptcp_subflow_delegate(struct mptcp_subflow_context *subflow, int action)
+{
+	long old, set_bits = BIT(MPTCP_DELEGATE_SCHEDULED) | BIT(action);
+	struct mptcp_delegated_action *delegated;
+	bool schedule;
+
+	/* the caller held the subflow bh socket lock */
+	lockdep_assert_in_softirq();
+
+	/* The implied barrier pairs with tcp_release_cb_override()
+	 * mptcp_napi_poll(), and ensures the below list check sees list
+	 * updates done prior to delegated status bits changes
+	 */
+	old = set_mask_bits(&subflow->delegated_status, 0, set_bits);
+	if (!(old & BIT(MPTCP_DELEGATE_SCHEDULED))) {
+		if (WARN_ON_ONCE(!list_empty(&subflow->delegated_node)))
+			return;
+
+		local_lock_nested_bh(&mptcp_delegated_actions.bh_lock);
+		delegated = this_cpu_ptr(&mptcp_delegated_actions);
+		schedule = list_empty(&delegated->head);
+		list_add_tail(&subflow->delegated_node, &delegated->head);
+		local_unlock_nested_bh(&mptcp_delegated_actions.bh_lock);
+		sock_hold(mptcp_subflow_tcp_sock(subflow));
+		if (schedule)
+			napi_schedule(&delegated->napi);
+	}
+}
+
+static inline struct mptcp_subflow_context *
+mptcp_subflow_delegated_next(struct mptcp_delegated_action *delegated)
+{
+	struct mptcp_subflow_context *ret;
+
+	local_lock_nested_bh(&mptcp_delegated_actions.bh_lock);
+	if (list_empty(&delegated->head)) {
+		local_unlock_nested_bh(&mptcp_delegated_actions.bh_lock);
+		return NULL;
+	}
+
+	ret = list_first_entry(&delegated->head, struct mptcp_subflow_context, delegated_node);
+	list_del_init(&ret->delegated_node);
+	local_unlock_nested_bh(&mptcp_delegated_actions.bh_lock);
+	return ret;
+}
+
+void __mptcp_inherit_memcg(struct sock *sk, struct sock *ssk, gfp_t gfp);
+void __mptcp_inherit_cgrp_data(struct sock *sk, struct sock *ssk);
+
+int mptcp_is_enabled(const struct net *net);
+unsigned int mptcp_get_add_addr_timeout(const struct net *net);
+int mptcp_is_checksum_enabled(const struct net *net);
+int mptcp_allow_join_id0(const struct net *net);
+unsigned int mptcp_stale_loss_cnt(const struct net *net);
+unsigned int mptcp_close_timeout(const struct sock *sk);
+int mptcp_get_pm_type(const struct net *net);
+const char *mptcp_get_path_manager(const struct net *net);
+const char *mptcp_get_scheduler(const struct net *net);
+unsigned int mptcp_add_addr_v6_port_drop_ts(const struct net *net);
+
+void mptcp_active_disable(struct sock *sk);
+bool mptcp_active_should_disable(struct sock *ssk);
+void mptcp_active_enable(struct sock *sk);
+
+void mptcp_get_available_schedulers(char *buf, size_t maxlen);
+void __mptcp_subflow_fully_established(struct mptcp_sock *msk,
+				       struct mptcp_subflow_context *subflow,
+				       const struct mptcp_options_received *mp_opt);
+bool __mptcp_retransmit_pending_data(struct sock *sk);
+void mptcp_check_and_set_pending(struct sock *sk);
+void __mptcp_push_pending(struct sock *sk, unsigned int flags);
+bool mptcp_subflow_data_available(struct sock *sk);
+void __init mptcp_subflow_init(void);
+void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how);
+void mptcp_close_ssk(struct sock *sk, struct sock *ssk,
+		     struct mptcp_subflow_context *subflow);
+void __mptcp_subflow_send_ack(struct sock *ssk);
+void mptcp_subflow_reset(struct sock *ssk);
+void mptcp_subflow_queue_clean(struct sock *sk, struct sock *ssk);
+void mptcp_sock_graft(struct sock *sk, struct socket *parent);
+struct sock *__mptcp_nmpc_sk(struct mptcp_sock *msk);
+bool __mptcp_close(struct sock *sk, long timeout);
+void mptcp_cancel_work(struct sock *sk);
+void __mptcp_unaccepted_force_close(struct sock *sk);
+void mptcp_set_state(struct sock *sk, int state);
+
+bool mptcp_addresses_equal(const struct mptcp_addr_info *a,
+			   const struct mptcp_addr_info *b, bool use_port);
+void mptcp_local_address(const struct sock_common *skc,
+			 struct mptcp_addr_info *addr);
+void mptcp_remote_address(const struct sock_common *skc,
+			  struct mptcp_addr_info *addr);
+
+/* called with sk socket lock held */
+int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_pm_local *local,
+			    const struct mptcp_addr_info *remote);
+int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
+				struct socket **new_sock);
+void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
+			 struct sockaddr_storage *addr,
+			 unsigned short family);
+struct mptcp_sched_ops *mptcp_sched_find(const char *name);
+int mptcp_validate_scheduler(struct mptcp_sched_ops *sched);
+int mptcp_register_scheduler(struct mptcp_sched_ops *sched);
+void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched);
+void mptcp_sched_init(void);
+int mptcp_init_sched(struct mptcp_sock *msk,
+		     struct mptcp_sched_ops *sched);
+void mptcp_release_sched(struct mptcp_sock *msk);
+void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
+				 bool scheduled);
+struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk);
+struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk);
+int mptcp_sched_get_send(struct mptcp_sock *msk);
+int mptcp_sched_get_retrans(struct mptcp_sock *msk);
+
+static inline u64 mptcp_data_avail(const struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->bytes_received) - READ_ONCE(msk->bytes_consumed);
+}
+
+static inline bool mptcp_epollin_ready(const struct sock *sk)
+{
+	u64 data_avail = mptcp_data_avail(mptcp_sk(sk));
+
+	if (!data_avail)
+		return false;
+
+	/* mptcp doesn't have to deal with small skbs in the receive queue,
+	 * as it can always coalesce them
+	 */
+	return (data_avail >= sk->sk_rcvlowat) ||
+		tcp_under_memory_pressure(sk);
+}
+
+int mptcp_set_rcvlowat(struct sock *sk, int val);
+
+static inline bool __tcp_can_send(const struct sock *ssk)
+{
+	/* only send if our side has not closed yet */
+	return ((1 << inet_sk_state_load(ssk)) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT));
+}
+
+static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow)
+{
+	/* can't send if JOIN hasn't completed yet (i.e. is usable for mptcp) */
+	if (subflow->request_join && !READ_ONCE(subflow->fully_established))
+		return false;
+
+	return __tcp_can_send(mptcp_subflow_tcp_sock(subflow));
+}
+
+void mptcp_subflow_set_active(struct mptcp_subflow_context *subflow);
+
+bool mptcp_subflow_active(struct mptcp_subflow_context *subflow);
+
+void mptcp_subflow_drop_ctx(struct sock *ssk);
+
+static inline void mptcp_subflow_tcp_fallback(struct sock *sk,
+					      struct mptcp_subflow_context *ctx)
+{
+	sk->sk_data_ready = sock_def_readable;
+	sk->sk_state_change = ctx->tcp_state_change;
+	sk->sk_write_space = sk_stream_write_space;
+	sk->sk_error_report = ctx->tcp_error_report;
+
+	inet_csk(sk)->icsk_af_ops = ctx->icsk_af_ops;
+}
+
+void __init mptcp_proto_init(void);
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+int __init mptcp_proto_v6_init(void);
+void __init mptcp_subflow_v6_init(void);
+#endif
+
+struct sock *mptcp_sk_clone_init(const struct sock *sk,
+				 const struct mptcp_options_received *mp_opt,
+				 struct sock *ssk,
+				 struct request_sock *req);
+void mptcp_get_options(const struct sk_buff *skb,
+		       struct mptcp_options_received *mp_opt);
+
+void mptcp_finish_connect(struct sock *sk);
+void __mptcp_sync_state(struct sock *sk, int state);
+void mptcp_reset_tout_timer(struct mptcp_sock *msk, unsigned long fail_tout);
+
+static inline void mptcp_stop_tout_timer(struct sock *sk)
+{
+	if (!inet_csk(sk)->icsk_mtup.probe_timestamp)
+		return;
+
+	sk_stop_timer(sk, &inet_csk(sk)->mptcp_tout_timer);
+	inet_csk(sk)->icsk_mtup.probe_timestamp = 0;
+}
+
+static inline void mptcp_set_close_tout(struct sock *sk, unsigned long tout)
+{
+	/* avoid 0 timestamp, as that means no close timeout */
+	inet_csk(sk)->icsk_mtup.probe_timestamp = tout ? : 1;
+}
+
+static inline void mptcp_start_tout_timer(struct sock *sk)
+{
+	mptcp_set_close_tout(sk, tcp_jiffies32);
+	mptcp_reset_tout_timer(mptcp_sk(sk), 0);
+}
+
+static inline bool mptcp_is_fully_established(struct sock *sk)
+{
+	return inet_sk_state_load(sk) == TCP_ESTABLISHED &&
+	       READ_ONCE(mptcp_sk(sk)->fully_established);
+}
+
+static inline u64 mptcp_stamp(void)
+{
+	return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
+}
+
+void mptcp_data_ready(struct sock *sk, struct sock *ssk);
+bool mptcp_finish_join(struct sock *sk);
+bool mptcp_schedule_work(struct sock *sk);
+int mptcp_setsockopt(struct sock *sk, int level, int optname,
+		     sockptr_t optval, unsigned int optlen);
+int mptcp_getsockopt(struct sock *sk, int level, int optname,
+		     char __user *optval, int __user *option);
+
+u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq);
+static inline u64 mptcp_expand_seq(u64 old_seq, u64 cur_seq, bool use_64bit)
+{
+	if (use_64bit)
+		return cur_seq;
+
+	return __mptcp_expand_seq(old_seq, cur_seq);
+}
+void __mptcp_check_push(struct sock *sk, struct sock *ssk);
+void __mptcp_data_acked(struct sock *sk);
+void __mptcp_error_report(struct sock *sk);
+bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit);
+static inline bool mptcp_data_fin_enabled(const struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->snd_data_fin_enable) &&
+	       READ_ONCE(msk->write_seq) == READ_ONCE(msk->snd_nxt);
+}
+
+static inline u32 mptcp_notsent_lowat(const struct sock *sk)
+{
+	struct net *net = sock_net(sk);
+	u32 val;
+
+	val = READ_ONCE(mptcp_sk(sk)->notsent_lowat);
+	return val ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
+}
+
+static inline bool mptcp_stream_memory_free(const struct sock *sk, int wake)
+{
+	const struct mptcp_sock *msk = mptcp_sk(sk);
+	u32 notsent_bytes;
+
+	notsent_bytes = READ_ONCE(msk->write_seq) - READ_ONCE(msk->snd_nxt);
+	return (notsent_bytes << wake) < mptcp_notsent_lowat(sk);
+}
+
+static inline bool __mptcp_stream_is_writeable(const struct sock *sk, int wake)
+{
+	return mptcp_stream_memory_free(sk, wake) &&
+	       __sk_stream_is_writeable(sk, wake);
+}
+
+static inline void mptcp_write_space(struct sock *sk)
+{
+	/* pairs with memory barrier in mptcp_poll */
+	smp_mb();
+	if (mptcp_stream_memory_free(sk, 1))
+		INDIRECT_CALL_1(sk->sk_write_space, sk_stream_write_space, sk);
+}
+
+static inline void __mptcp_sync_sndbuf(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow;
+	int ssk_sndbuf, new_sndbuf;
+
+	if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
+		return;
+
+	new_sndbuf = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[0]);
+	mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
+		ssk_sndbuf =  READ_ONCE(mptcp_subflow_tcp_sock(subflow)->sk_sndbuf);
+
+		subflow->cached_sndbuf = ssk_sndbuf;
+		new_sndbuf += ssk_sndbuf;
+	}
+
+	/* the msk max wmem limit is <nr_subflows> * tcp wmem[2] */
+	WRITE_ONCE(sk->sk_sndbuf, new_sndbuf);
+	mptcp_write_space(sk);
+}
+
+/* The called held both the msk socket and the subflow socket locks,
+ * possibly under BH
+ */
+static inline void __mptcp_propagate_sndbuf(struct sock *sk, struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+
+	if (READ_ONCE(ssk->sk_sndbuf) != subflow->cached_sndbuf)
+		__mptcp_sync_sndbuf(sk);
+}
+
+/* the caller held only the subflow socket lock, either in process or
+ * BH context. Additionally this can be called under the msk data lock,
+ * so we can't acquire such lock here: let the delegate action acquires
+ * the needed locks in suitable order.
+ */
+static inline void mptcp_propagate_sndbuf(struct sock *sk, struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+
+	if (likely(READ_ONCE(ssk->sk_sndbuf) == subflow->cached_sndbuf))
+		return;
+
+	local_bh_disable();
+	mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_SNDBUF);
+	local_bh_enable();
+}
+
+#define MPTCP_TOKEN_MAX_RETRIES	4
+
+void __init mptcp_token_init(void);
+static inline void mptcp_token_init_request(struct request_sock *req)
+{
+	mptcp_subflow_rsk(req)->token_node.pprev = NULL;
+}
+
+int mptcp_token_new_request(struct request_sock *req);
+void mptcp_token_destroy_request(struct request_sock *req);
+int mptcp_token_new_connect(struct sock *ssk);
+void mptcp_token_accept(struct mptcp_subflow_request_sock *r,
+			struct mptcp_sock *msk);
+bool mptcp_token_exists(u32 token);
+struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token);
+struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
+					 long *s_num);
+void mptcp_token_destroy(struct mptcp_sock *msk);
+
+void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn);
+
+void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac);
+__sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum);
+
+void __init mptcp_pm_init(void);
+void mptcp_pm_data_init(struct mptcp_sock *msk);
+void mptcp_pm_data_reset(struct mptcp_sock *msk);
+void mptcp_pm_destroy(struct mptcp_sock *msk);
+int mptcp_pm_parse_addr(struct nlattr *attr, struct genl_info *info,
+			struct mptcp_addr_info *addr);
+int mptcp_pm_parse_entry(struct nlattr *attr, struct genl_info *info,
+			 bool require_family,
+			 struct mptcp_pm_addr_entry *entry);
+bool mptcp_pm_addr_families_match(const struct sock *sk,
+				  const struct mptcp_addr_info *loc,
+				  const struct mptcp_addr_info *rem);
+void mptcp_pm_chk_stale(const struct mptcp_sock *msk);
+void mptcp_pm_new_connection(struct mptcp_sock *msk, const struct sock *ssk, int server_side);
+void mptcp_pm_fully_established(struct mptcp_sock *msk, const struct sock *ssk);
+bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk);
+void mptcp_pm_connection_closed(struct mptcp_sock *msk);
+void mptcp_pm_subflow_established(struct mptcp_sock *msk);
+bool mptcp_pm_nl_check_work_pending(struct mptcp_sock *msk);
+void mptcp_pm_subflow_check_next(struct mptcp_sock *msk,
+				 const struct mptcp_subflow_context *subflow);
+void mptcp_pm_add_addr_received(const struct sock *ssk,
+				const struct mptcp_addr_info *addr);
+void mptcp_pm_add_addr_echoed(struct mptcp_sock *msk,
+			      const struct mptcp_addr_info *addr);
+void mptcp_pm_send_ack(struct mptcp_sock *msk,
+		       struct mptcp_subflow_context *subflow,
+		       bool prio, bool backup);
+void mptcp_pm_addr_send_ack(struct mptcp_sock *msk);
+void mptcp_pm_nl_rm_addr(struct mptcp_sock *msk, u8 rm_id);
+void mptcp_pm_rm_subflow(struct mptcp_sock *msk,
+			 const struct mptcp_rm_list *rm_list);
+void mptcp_pm_rm_addr_received(struct mptcp_sock *msk,
+			       const struct mptcp_rm_list *rm_list);
+void mptcp_pm_mp_prio_received(struct sock *sk, u8 bkup);
+void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq);
+int mptcp_pm_mp_prio_send_ack(struct mptcp_sock *msk,
+			      struct mptcp_addr_info *addr,
+			      struct mptcp_addr_info *rem,
+			      u8 bkup);
+bool mptcp_pm_announced_alloc(struct mptcp_sock *msk,
+			      const struct mptcp_addr_info *addr);
+bool mptcp_pm_announced_remove(struct mptcp_sock *msk,
+			       const struct mptcp_addr_info *addr);
+bool mptcp_pm_announced_has_ssk(struct mptcp_sock *msk, const struct sock *ssk);
+bool mptcp_pm_has_subflow_saddr(const struct mptcp_sock *msk,
+				const struct mptcp_addr_info *saddr);
+int mptcp_pm_nl_set_flags(struct mptcp_pm_addr_entry *local,
+			  struct genl_info *info);
+int mptcp_userspace_pm_set_flags(struct mptcp_pm_addr_entry *local,
+				 struct genl_info *info);
+int mptcp_pm_announce_addr(struct mptcp_sock *msk,
+			   const struct mptcp_addr_info *addr,
+			   bool echo);
+int mptcp_pm_remove_addr(struct mptcp_sock *msk, const struct mptcp_rm_list *rm_list);
+
+/* the default path manager, used in mptcp_pm_unregister */
+extern struct mptcp_pm_ops mptcp_pm_kernel;
+
+struct mptcp_pm_ops *mptcp_pm_find(const char *name);
+int mptcp_pm_register(struct mptcp_pm_ops *pm_ops);
+void mptcp_pm_unregister(struct mptcp_pm_ops *pm_ops);
+int mptcp_pm_validate(struct mptcp_pm_ops *pm_ops);
+void mptcp_pm_get_available(char *buf, size_t maxlen);
+
+void mptcp_userspace_pm_free_local_addr_list(struct mptcp_sock *msk);
+
+void mptcp_event(enum mptcp_event_type type, const struct mptcp_sock *msk,
+		 const struct sock *ssk, gfp_t gfp);
+void mptcp_event_addr_announced(const struct sock *ssk, const struct mptcp_addr_info *info);
+void mptcp_event_addr_removed(const struct mptcp_sock *msk, u8 id);
+void mptcp_event_pm_listener(const struct sock *ssk,
+			     enum mptcp_event_type event);
+bool mptcp_userspace_pm_active(const struct mptcp_sock *msk);
+
+void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subflow,
+					      struct request_sock *req);
+int mptcp_pm_genl_fill_addr(struct sk_buff *msg,
+			    struct netlink_callback *cb,
+			    struct mptcp_pm_addr_entry *entry);
+
+static inline bool mptcp_pm_should_add_signal(struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->pm.addr_signal) &
+		(BIT(MPTCP_ADD_ADDR_SIGNAL) | BIT(MPTCP_ADD_ADDR_ECHO));
+}
+
+static inline bool mptcp_pm_should_add_signal_addr(struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->pm.addr_signal) & BIT(MPTCP_ADD_ADDR_SIGNAL);
+}
+
+static inline bool mptcp_pm_should_add_signal_echo(struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->pm.addr_signal) & BIT(MPTCP_ADD_ADDR_ECHO);
+}
+
+static inline bool mptcp_pm_should_rm_signal(struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->pm.addr_signal) & BIT(MPTCP_RM_ADDR_SIGNAL);
+}
+
+static inline bool mptcp_pm_is_userspace(const struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->pm.pm_type) == MPTCP_PM_TYPE_USERSPACE;
+}
+
+static inline bool mptcp_pm_is_kernel(const struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->pm.pm_type) == MPTCP_PM_TYPE_KERNEL;
+}
+
+bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, int *size, int remaining,
+			      struct mptcp_addr_info *addr, bool *echo,
+			      bool *drop_ts);
+bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
+			     struct mptcp_rm_list *rm_list, int *len);
+int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
+int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk,
+			     struct mptcp_pm_addr_entry *skc);
+int mptcp_userspace_pm_get_local_id(struct mptcp_sock *msk,
+				    struct mptcp_pm_addr_entry *skc);
+bool mptcp_pm_is_backup(struct mptcp_sock *msk, struct sock_common *skc);
+bool mptcp_pm_nl_is_backup(struct mptcp_sock *msk, struct mptcp_addr_info *skc);
+bool mptcp_userspace_pm_is_backup(struct mptcp_sock *msk, struct mptcp_addr_info *skc);
+int mptcp_pm_nl_dump_addr(struct sk_buff *msg,
+			  struct netlink_callback *cb);
+int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
+				 struct netlink_callback *cb);
+int mptcp_pm_nl_get_addr(u8 id, struct mptcp_pm_addr_entry *addr,
+			 struct genl_info *info);
+int mptcp_userspace_pm_get_addr(u8 id, struct mptcp_pm_addr_entry *addr,
+				struct genl_info *info);
+
+static inline u8 subflow_get_local_id(const struct mptcp_subflow_context *subflow)
+{
+	int local_id = READ_ONCE(subflow->local_id);
+
+	if (local_id < 0)
+		return 0;
+	return local_id;
+}
+
+void __init mptcp_pm_kernel_register(void);
+void __init mptcp_pm_userspace_register(void);
+void __init mptcp_pm_nl_init(void);
+void mptcp_pm_worker(struct mptcp_sock *msk);
+void __mptcp_pm_kernel_worker(struct mptcp_sock *msk);
+u8 mptcp_pm_get_endp_signal_max(const struct mptcp_sock *msk);
+u8 mptcp_pm_get_endp_subflow_max(const struct mptcp_sock *msk);
+u8 mptcp_pm_get_endp_laminar_max(const struct mptcp_sock *msk);
+u8 mptcp_pm_get_endp_fullmesh_max(const struct mptcp_sock *msk);
+u8 mptcp_pm_get_limit_add_addr_accepted(const struct mptcp_sock *msk);
+u8 mptcp_pm_get_limit_extra_subflows(const struct mptcp_sock *msk);
+
+/* called under PM lock */
+static inline void __mptcp_pm_close_subflow(struct mptcp_sock *msk)
+{
+	if (!WARN_ON_ONCE(msk->pm.extra_subflows == 0) &&
+	    --msk->pm.extra_subflows < mptcp_pm_get_limit_extra_subflows(msk))
+		WRITE_ONCE(msk->pm.accept_subflow, true);
+}
+
+static inline void mptcp_pm_close_subflow(struct mptcp_sock *msk)
+{
+	spin_lock_bh(&msk->pm.lock);
+	__mptcp_pm_close_subflow(msk);
+	spin_unlock_bh(&msk->pm.lock);
+}
+
+static inline bool mptcp_pm_add_addr_c_flag_case(struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->pm.remote_deny_join_id0) &&
+	       msk->pm.local_addr_used == 0 &&
+	       mptcp_pm_get_limit_add_addr_accepted(msk) == 0 &&
+	       msk->pm.extra_subflows < mptcp_pm_get_limit_extra_subflows(msk);
+}
+
+void mptcp_sockopt_sync_locked(struct mptcp_sock *msk, struct sock *ssk);
+
+static inline struct mptcp_ext *mptcp_get_ext(const struct sk_buff *skb)
+{
+	return (struct mptcp_ext *)skb_ext_find(skb, SKB_EXT_MPTCP);
+}
+
+void mptcp_diag_subflow_init(struct tcp_ulp_ops *ops);
+
+static inline bool __mptcp_check_fallback(const struct mptcp_sock *msk)
+{
+	return test_bit(MPTCP_FALLBACK_DONE, &msk->flags);
+}
+
+static inline bool mptcp_check_fallback(const struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+
+	return __mptcp_check_fallback(msk);
+}
+
+static inline bool __mptcp_has_initial_subflow(const struct mptcp_sock *msk)
+{
+	struct sock *ssk = READ_ONCE(msk->first);
+
+	return ssk && ((1 << inet_sk_state_load(ssk)) &
+		       (TCPF_ESTABLISHED | TCPF_SYN_SENT |
+			TCPF_SYN_RECV | TCPF_LISTEN));
+}
+
+bool __mptcp_try_fallback(struct mptcp_sock *msk, int fb_mib);
+
+static inline bool mptcp_try_fallback(struct sock *ssk, int fb_mib)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = subflow->conn;
+	struct mptcp_sock *msk;
+
+	msk = mptcp_sk(sk);
+	if (!__mptcp_try_fallback(msk, fb_mib))
+		return false;
+	if (READ_ONCE(msk->snd_data_fin_enable) && !(ssk->sk_shutdown & SEND_SHUTDOWN)) {
+		gfp_t saved_allocation = ssk->sk_allocation;
+
+		/* we are in a atomic (BH) scope, override ssk default for data
+		 * fin allocation
+		 */
+		ssk->sk_allocation = GFP_ATOMIC;
+		ssk->sk_shutdown |= SEND_SHUTDOWN;
+		tcp_shutdown(ssk, SEND_SHUTDOWN);
+		ssk->sk_allocation = saved_allocation;
+	}
+	return true;
+}
+
+static inline void mptcp_early_fallback(struct mptcp_sock *msk,
+					struct mptcp_subflow_context *subflow,
+					int fb_mib)
+{
+	subflow->request_mptcp = 0;
+	WARN_ON_ONCE(!__mptcp_try_fallback(msk, fb_mib));
+}
+
+static inline bool mptcp_check_infinite_map(struct sk_buff *skb)
+{
+	struct mptcp_ext *mpext;
+
+	mpext = skb ? mptcp_get_ext(skb) : NULL;
+	if (mpext && mpext->infinite_map)
+		return true;
+
+	return false;
+}
+
+static inline bool is_active_ssk(struct mptcp_subflow_context *subflow)
+{
+	return (subflow->request_mptcp || subflow->request_join);
+}
+
+static inline bool subflow_simultaneous_connect(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	/* Note that the sk state implies !subflow->conn_finished. */
+	return sk->sk_state == TCP_SYN_RECV && is_active_ssk(subflow);
+}
+
+#ifdef CONFIG_SYN_COOKIES
+void subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,
+				       struct sk_buff *skb);
+bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,
+					struct sk_buff *skb);
+void __init mptcp_join_cookie_init(void);
+#else
+static inline void
+subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,
+				  struct sk_buff *skb) {}
+static inline bool
+mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,
+				   struct sk_buff *skb)
+{
+	return false;
+}
+
+static inline void mptcp_join_cookie_init(void) {}
+#endif
+
+#endif /* __MPTCP_PROTOCOL_H */
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
new file mode 100644
index 000000000..1e59072d4
--- /dev/null
+++ b/net/mptcp/sched.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2022, SUSE.
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/rculist.h>
+#include <linux/spinlock.h>
+#include "protocol.h"
+
+static DEFINE_SPINLOCK(mptcp_sched_list_lock);
+static LIST_HEAD(mptcp_sched_list);
+
+static int mptcp_sched_default_get_send(struct mptcp_sock *msk)
+{
+	struct sock *ssk;
+
+	ssk = mptcp_subflow_get_send(msk);
+	if (!ssk)
+		return -EINVAL;
+
+	mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
+	return 0;
+}
+
+static int mptcp_sched_default_get_retrans(struct mptcp_sock *msk)
+{
+	struct sock *ssk;
+
+	ssk = mptcp_subflow_get_retrans(msk);
+	if (!ssk)
+		return -EINVAL;
+
+	mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
+	return 0;
+}
+
+static struct mptcp_sched_ops mptcp_sched_default = {
+	.get_send	= mptcp_sched_default_get_send,
+	.get_retrans	= mptcp_sched_default_get_retrans,
+	.name		= "default",
+	.owner		= THIS_MODULE,
+};
+
+/* Must be called with rcu read lock held */
+struct mptcp_sched_ops *mptcp_sched_find(const char *name)
+{
+	struct mptcp_sched_ops *sched, *ret = NULL;
+
+	list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
+		if (!strcmp(sched->name, name)) {
+			ret = sched;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+/* Build string with list of available scheduler values.
+ * Similar to tcp_get_available_congestion_control()
+ */
+void mptcp_get_available_schedulers(char *buf, size_t maxlen)
+{
+	struct mptcp_sched_ops *sched;
+	size_t offs = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
+		offs += snprintf(buf + offs, maxlen - offs,
+				 "%s%s",
+				 offs == 0 ? "" : " ", sched->name);
+
+		if (WARN_ON_ONCE(offs >= maxlen))
+			break;
+	}
+	rcu_read_unlock();
+}
+
+int mptcp_validate_scheduler(struct mptcp_sched_ops *sched)
+{
+	if (!sched->get_send) {
+		pr_err("%s does not implement required ops\n", sched->name);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int mptcp_register_scheduler(struct mptcp_sched_ops *sched)
+{
+	int ret;
+
+	ret = mptcp_validate_scheduler(sched);
+	if (ret)
+		return ret;
+
+	spin_lock(&mptcp_sched_list_lock);
+	if (mptcp_sched_find(sched->name)) {
+		spin_unlock(&mptcp_sched_list_lock);
+		return -EEXIST;
+	}
+	list_add_tail_rcu(&sched->list, &mptcp_sched_list);
+	spin_unlock(&mptcp_sched_list_lock);
+
+	pr_debug("%s registered\n", sched->name);
+	return 0;
+}
+
+void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched)
+{
+	if (sched == &mptcp_sched_default)
+		return;
+
+	spin_lock(&mptcp_sched_list_lock);
+	list_del_rcu(&sched->list);
+	spin_unlock(&mptcp_sched_list_lock);
+}
+
+void mptcp_sched_init(void)
+{
+	mptcp_register_scheduler(&mptcp_sched_default);
+}
+
+int mptcp_init_sched(struct mptcp_sock *msk,
+		     struct mptcp_sched_ops *sched)
+{
+	if (!sched)
+		sched = &mptcp_sched_default;
+
+	if (!bpf_try_module_get(sched, sched->owner))
+		return -EBUSY;
+
+	msk->sched = sched;
+	if (msk->sched->init)
+		msk->sched->init(msk);
+
+	pr_debug("sched=%s\n", msk->sched->name);
+
+	return 0;
+}
+
+void mptcp_release_sched(struct mptcp_sock *msk)
+{
+	struct mptcp_sched_ops *sched = msk->sched;
+
+	if (!sched)
+		return;
+
+	msk->sched = NULL;
+	if (sched->release)
+		sched->release(msk);
+
+	bpf_module_put(sched, sched->owner);
+}
+
+void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
+				 bool scheduled)
+{
+	WRITE_ONCE(subflow->scheduled, scheduled);
+}
+
+int mptcp_sched_get_send(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+
+	msk_owned_by_me(msk);
+
+	/* the following check is moved out of mptcp_subflow_get_send */
+	if (__mptcp_check_fallback(msk)) {
+		if (msk->first &&
+		    __tcp_can_send(msk->first) &&
+		    sk_stream_memory_free(msk->first)) {
+			mptcp_subflow_set_scheduled(mptcp_subflow_ctx(msk->first), true);
+			return 0;
+		}
+		return -EINVAL;
+	}
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->scheduled))
+			return 0;
+	}
+
+	if (msk->sched == &mptcp_sched_default || !msk->sched)
+		return mptcp_sched_default_get_send(msk);
+	return msk->sched->get_send(msk);
+}
+
+int mptcp_sched_get_retrans(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+
+	msk_owned_by_me(msk);
+
+	/* the following check is moved out of mptcp_subflow_get_retrans */
+	if (__mptcp_check_fallback(msk))
+		return -EINVAL;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->scheduled))
+			return 0;
+	}
+
+	if (msk->sched == &mptcp_sched_default || !msk->sched)
+		return mptcp_sched_default_get_retrans(msk);
+	if (msk->sched->get_retrans)
+		return msk->sched->get_retrans(msk);
+	return msk->sched->get_send(msk);
+}
diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
new file mode 100644
index 000000000..fcf6feb2a
--- /dev/null
+++ b/net/mptcp/sockopt.c
@@ -0,0 +1,1669 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2021, Red Hat.
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <net/sock.h>
+#include <net/protocol.h>
+#include <net/tcp.h>
+#include <net/mptcp.h>
+#include "protocol.h"
+
+#define MIN_INFO_OPTLEN_SIZE		16
+#define MIN_FULL_INFO_OPTLEN_SIZE	40
+
+static struct sock *__mptcp_tcp_fallback(struct mptcp_sock *msk)
+{
+	msk_owned_by_me(msk);
+
+	if (likely(!__mptcp_check_fallback(msk)))
+		return NULL;
+
+	return msk->first;
+}
+
+static u32 sockopt_seq_reset(const struct sock *sk)
+{
+	sock_owned_by_me(sk);
+
+	/* Highbits contain state.  Allows to distinguish sockopt_seq
+	 * of listener and established:
+	 * s0 = new_listener()
+	 * sockopt(s0) - seq is 1
+	 * s1 = accept(s0) - s1 inherits seq 1 if listener sk (s0)
+	 * sockopt(s0) - seq increments to 2 on s0
+	 * sockopt(s1) // seq increments to 2 on s1 (different option)
+	 * new ssk completes join, inherits options from s0 // seq 2
+	 * Needs sync from mptcp join logic, but ssk->seq == msk->seq
+	 *
+	 * Set High order bits to sk_state so ssk->seq == msk->seq test
+	 * will fail.
+	 */
+
+	return (u32)sk->sk_state << 24u;
+}
+
+static void sockopt_seq_inc(struct mptcp_sock *msk)
+{
+	u32 seq = (msk->setsockopt_seq + 1) & 0x00ffffff;
+
+	msk->setsockopt_seq = sockopt_seq_reset((struct sock *)msk) + seq;
+}
+
+static int mptcp_get_int_option(struct mptcp_sock *msk, sockptr_t optval,
+				unsigned int optlen, int *val)
+{
+	if (optlen < sizeof(int))
+		return -EINVAL;
+
+	if (copy_from_sockptr(val, optval, sizeof(*val)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static void __mptcp_subflow_set_rcvbuf(struct sock *ssk, int val)
+{
+	WRITE_ONCE(ssk->sk_rcvbuf, val);
+	tcp_set_rcvbuf(ssk, val);
+}
+
+static void mptcp_sol_socket_sync_intval(struct mptcp_sock *msk, int optname, int val)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+
+	lock_sock(sk);
+	sockopt_seq_inc(msk);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow = lock_sock_fast(ssk);
+
+		switch (optname) {
+		case SO_DEBUG:
+			sock_valbool_flag(ssk, SOCK_DBG, !!val);
+			break;
+		case SO_KEEPALIVE:
+			if (ssk->sk_prot->keepalive)
+				ssk->sk_prot->keepalive(ssk, !!val);
+			sock_valbool_flag(ssk, SOCK_KEEPOPEN, !!val);
+			break;
+		case SO_PRIORITY:
+			WRITE_ONCE(ssk->sk_priority, val);
+			break;
+		case SO_SNDBUF:
+		case SO_SNDBUFFORCE:
+			ssk->sk_userlocks |= SOCK_SNDBUF_LOCK;
+			WRITE_ONCE(ssk->sk_sndbuf, sk->sk_sndbuf);
+			mptcp_subflow_ctx(ssk)->cached_sndbuf = sk->sk_sndbuf;
+			break;
+		case SO_RCVBUF:
+		case SO_RCVBUFFORCE:
+			ssk->sk_userlocks |= SOCK_RCVBUF_LOCK;
+			__mptcp_subflow_set_rcvbuf(ssk, sk->sk_rcvbuf);
+			break;
+		case SO_MARK:
+			if (READ_ONCE(ssk->sk_mark) != sk->sk_mark) {
+				WRITE_ONCE(ssk->sk_mark, sk->sk_mark);
+				sk_dst_reset(ssk);
+			}
+			break;
+		case SO_INCOMING_CPU:
+			WRITE_ONCE(ssk->sk_incoming_cpu, val);
+			break;
+		}
+
+		subflow->setsockopt_seq = msk->setsockopt_seq;
+		unlock_sock_fast(ssk, slow);
+	}
+
+	release_sock(sk);
+}
+
+static int mptcp_sol_socket_intval(struct mptcp_sock *msk, int optname, int val)
+{
+	sockptr_t optval = KERNEL_SOCKPTR(&val);
+	struct sock *sk = (struct sock *)msk;
+	int ret;
+
+	ret = sock_setsockopt(sk->sk_socket, SOL_SOCKET, optname,
+			      optval, sizeof(val));
+	if (ret)
+		return ret;
+
+	mptcp_sol_socket_sync_intval(msk, optname, val);
+	return 0;
+}
+
+static void mptcp_so_incoming_cpu(struct mptcp_sock *msk, int val)
+{
+	struct sock *sk = (struct sock *)msk;
+
+	WRITE_ONCE(sk->sk_incoming_cpu, val);
+
+	mptcp_sol_socket_sync_intval(msk, SO_INCOMING_CPU, val);
+}
+
+static int mptcp_setsockopt_sol_socket_tstamp(struct mptcp_sock *msk, int optname, int val)
+{
+	sockptr_t optval = KERNEL_SOCKPTR(&val);
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	int ret;
+
+	ret = sock_setsockopt(sk->sk_socket, SOL_SOCKET, optname,
+			      optval, sizeof(val));
+	if (ret)
+		return ret;
+
+	lock_sock(sk);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		lock_sock(ssk);
+		sock_set_timestamp(ssk, optname, !!val);
+		release_sock(ssk);
+	}
+
+	release_sock(sk);
+	return 0;
+}
+
+static int mptcp_setsockopt_sol_socket_int(struct mptcp_sock *msk, int optname,
+					   sockptr_t optval,
+					   unsigned int optlen)
+{
+	int val, ret;
+
+	ret = mptcp_get_int_option(msk, optval, optlen, &val);
+	if (ret)
+		return ret;
+
+	switch (optname) {
+	case SO_KEEPALIVE:
+	case SO_DEBUG:
+	case SO_MARK:
+	case SO_PRIORITY:
+	case SO_SNDBUF:
+	case SO_SNDBUFFORCE:
+	case SO_RCVBUF:
+	case SO_RCVBUFFORCE:
+		return mptcp_sol_socket_intval(msk, optname, val);
+	case SO_INCOMING_CPU:
+		mptcp_so_incoming_cpu(msk, val);
+		return 0;
+	case SO_TIMESTAMP_OLD:
+	case SO_TIMESTAMP_NEW:
+	case SO_TIMESTAMPNS_OLD:
+	case SO_TIMESTAMPNS_NEW:
+		return mptcp_setsockopt_sol_socket_tstamp(msk, optname, val);
+	}
+
+	return -ENOPROTOOPT;
+}
+
+static int mptcp_setsockopt_sol_socket_timestamping(struct mptcp_sock *msk,
+						    int optname,
+						    sockptr_t optval,
+						    unsigned int optlen)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	struct so_timestamping timestamping;
+	int ret;
+
+	if (optlen == sizeof(timestamping)) {
+		if (copy_from_sockptr(&timestamping, optval,
+				      sizeof(timestamping)))
+			return -EFAULT;
+	} else if (optlen == sizeof(int)) {
+		memset(&timestamping, 0, sizeof(timestamping));
+
+		if (copy_from_sockptr(&timestamping.flags, optval, sizeof(int)))
+			return -EFAULT;
+	} else {
+		return -EINVAL;
+	}
+
+	ret = sock_setsockopt(sk->sk_socket, SOL_SOCKET, optname,
+			      KERNEL_SOCKPTR(&timestamping),
+			      sizeof(timestamping));
+	if (ret)
+		return ret;
+
+	lock_sock(sk);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		int err;
+
+		lock_sock(ssk);
+		err = sock_set_timestamping(ssk, optname, timestamping);
+		release_sock(ssk);
+
+		if (err < 0 && ret == 0)
+			ret = err;
+	}
+
+	release_sock(sk);
+
+	return ret;
+}
+
+static int mptcp_setsockopt_sol_socket_linger(struct mptcp_sock *msk, sockptr_t optval,
+					      unsigned int optlen)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	struct linger ling;
+	sockptr_t kopt;
+	int ret;
+
+	if (optlen < sizeof(ling))
+		return -EINVAL;
+
+	if (copy_from_sockptr(&ling, optval, sizeof(ling)))
+		return -EFAULT;
+
+	kopt = KERNEL_SOCKPTR(&ling);
+	ret = sock_setsockopt(sk->sk_socket, SOL_SOCKET, SO_LINGER, kopt, sizeof(ling));
+	if (ret)
+		return ret;
+
+	lock_sock(sk);
+	sockopt_seq_inc(msk);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow = lock_sock_fast(ssk);
+
+		if (!ling.l_onoff) {
+			sock_reset_flag(ssk, SOCK_LINGER);
+		} else {
+			ssk->sk_lingertime = sk->sk_lingertime;
+			sock_set_flag(ssk, SOCK_LINGER);
+		}
+
+		subflow->setsockopt_seq = msk->setsockopt_seq;
+		unlock_sock_fast(ssk, slow);
+	}
+
+	release_sock(sk);
+	return 0;
+}
+
+static int mptcp_setsockopt_sol_socket(struct mptcp_sock *msk, int optname,
+				       sockptr_t optval, unsigned int optlen)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct sock *ssk;
+	int ret;
+
+	switch (optname) {
+	case SO_REUSEPORT:
+	case SO_REUSEADDR:
+	case SO_BINDTODEVICE:
+	case SO_BINDTOIFINDEX:
+		lock_sock(sk);
+		ssk = __mptcp_nmpc_sk(msk);
+		if (IS_ERR(ssk)) {
+			release_sock(sk);
+			return PTR_ERR(ssk);
+		}
+
+		ret = sk_setsockopt(ssk, SOL_SOCKET, optname, optval, optlen);
+		if (ret == 0) {
+			if (optname == SO_REUSEPORT)
+				sk->sk_reuseport = ssk->sk_reuseport;
+			else if (optname == SO_REUSEADDR)
+				sk->sk_reuse = ssk->sk_reuse;
+			else if (optname == SO_BINDTODEVICE)
+				sk->sk_bound_dev_if = ssk->sk_bound_dev_if;
+			else if (optname == SO_BINDTOIFINDEX)
+				sk->sk_bound_dev_if = ssk->sk_bound_dev_if;
+		}
+		release_sock(sk);
+		return ret;
+	case SO_KEEPALIVE:
+	case SO_PRIORITY:
+	case SO_SNDBUF:
+	case SO_SNDBUFFORCE:
+	case SO_RCVBUF:
+	case SO_RCVBUFFORCE:
+	case SO_MARK:
+	case SO_INCOMING_CPU:
+	case SO_DEBUG:
+	case SO_TIMESTAMP_OLD:
+	case SO_TIMESTAMP_NEW:
+	case SO_TIMESTAMPNS_OLD:
+	case SO_TIMESTAMPNS_NEW:
+		return mptcp_setsockopt_sol_socket_int(msk, optname, optval,
+						       optlen);
+	case SO_TIMESTAMPING_OLD:
+	case SO_TIMESTAMPING_NEW:
+		return mptcp_setsockopt_sol_socket_timestamping(msk, optname,
+								optval, optlen);
+	case SO_LINGER:
+		return mptcp_setsockopt_sol_socket_linger(msk, optval, optlen);
+	case SO_RCVLOWAT:
+	case SO_RCVTIMEO_OLD:
+	case SO_RCVTIMEO_NEW:
+	case SO_SNDTIMEO_OLD:
+	case SO_SNDTIMEO_NEW:
+	case SO_BUSY_POLL:
+	case SO_PREFER_BUSY_POLL:
+	case SO_BUSY_POLL_BUDGET:
+		/* No need to copy: only relevant for msk */
+		return sock_setsockopt(sk->sk_socket, SOL_SOCKET, optname, optval, optlen);
+	case SO_NO_CHECK:
+	case SO_DONTROUTE:
+	case SO_BROADCAST:
+	case SO_BSDCOMPAT:
+	case SO_PASSCRED:
+	case SO_PASSPIDFD:
+	case SO_PASSSEC:
+	case SO_RXQ_OVFL:
+	case SO_WIFI_STATUS:
+	case SO_NOFCS:
+	case SO_SELECT_ERR_QUEUE:
+		return 0;
+	}
+
+	/* SO_OOBINLINE is not supported, let's avoid the related mess
+	 * SO_ATTACH_FILTER, SO_ATTACH_BPF, SO_ATTACH_REUSEPORT_CBPF,
+	 * SO_DETACH_REUSEPORT_BPF, SO_DETACH_FILTER, SO_LOCK_FILTER,
+	 * we must be careful with subflows
+	 *
+	 * SO_ATTACH_REUSEPORT_EBPF is not supported, at it checks
+	 * explicitly the sk_protocol field
+	 *
+	 * SO_PEEK_OFF is unsupported, as it is for plain TCP
+	 * SO_MAX_PACING_RATE is unsupported, we must be careful with subflows
+	 * SO_CNX_ADVICE is currently unsupported, could possibly be relevant,
+	 * but likely needs careful design
+	 *
+	 * SO_ZEROCOPY is currently unsupported, TODO in sndmsg
+	 * SO_TXTIME is currently unsupported
+	 */
+
+	return -EOPNOTSUPP;
+}
+
+static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname,
+			       sockptr_t optval, unsigned int optlen)
+{
+	struct sock *sk = (struct sock *)msk;
+	int ret = -EOPNOTSUPP;
+	struct sock *ssk;
+
+	switch (optname) {
+	case IPV6_V6ONLY:
+	case IPV6_TRANSPARENT:
+	case IPV6_FREEBIND:
+		lock_sock(sk);
+		ssk = __mptcp_nmpc_sk(msk);
+		if (IS_ERR(ssk)) {
+			release_sock(sk);
+			return PTR_ERR(ssk);
+		}
+
+		ret = tcp_setsockopt(ssk, SOL_IPV6, optname, optval, optlen);
+		if (ret != 0) {
+			release_sock(sk);
+			return ret;
+		}
+
+		sockopt_seq_inc(msk);
+
+		switch (optname) {
+		case IPV6_V6ONLY:
+			sk->sk_ipv6only = ssk->sk_ipv6only;
+			break;
+		case IPV6_TRANSPARENT:
+			inet_assign_bit(TRANSPARENT, sk,
+					inet_test_bit(TRANSPARENT, ssk));
+			break;
+		case IPV6_FREEBIND:
+			inet_assign_bit(FREEBIND, sk,
+					inet_test_bit(FREEBIND, ssk));
+			break;
+		}
+
+		release_sock(sk);
+		break;
+	}
+
+	return ret;
+}
+
+static bool mptcp_supported_sockopt(int level, int optname)
+{
+	if (level == SOL_IP) {
+		switch (optname) {
+		/* should work fine */
+		case IP_FREEBIND:
+		case IP_TRANSPARENT:
+		case IP_BIND_ADDRESS_NO_PORT:
+		case IP_LOCAL_PORT_RANGE:
+
+		/* the following are control cmsg related */
+		case IP_PKTINFO:
+		case IP_RECVTTL:
+		case IP_RECVTOS:
+		case IP_RECVOPTS:
+		case IP_RETOPTS:
+		case IP_PASSSEC:
+		case IP_RECVORIGDSTADDR:
+		case IP_CHECKSUM:
+		case IP_RECVFRAGSIZE:
+
+		/* common stuff that need some love */
+		case IP_TOS:
+		case IP_TTL:
+		case IP_MTU_DISCOVER:
+		case IP_RECVERR:
+
+		/* possibly less common may deserve some love */
+		case IP_MINTTL:
+
+		/* the following is apparently a no-op for plain TCP */
+		case IP_RECVERR_RFC4884:
+			return true;
+		}
+
+		/* IP_OPTIONS is not supported, needs subflow care */
+		/* IP_HDRINCL, IP_NODEFRAG are not supported, RAW specific */
+		/* IP_MULTICAST_TTL, IP_MULTICAST_LOOP, IP_UNICAST_IF,
+		 * IP_ADD_MEMBERSHIP, IP_ADD_SOURCE_MEMBERSHIP, IP_DROP_MEMBERSHIP,
+		 * IP_DROP_SOURCE_MEMBERSHIP, IP_BLOCK_SOURCE, IP_UNBLOCK_SOURCE,
+		 * MCAST_JOIN_GROUP, MCAST_LEAVE_GROUP MCAST_JOIN_SOURCE_GROUP,
+		 * MCAST_LEAVE_SOURCE_GROUP, MCAST_BLOCK_SOURCE, MCAST_UNBLOCK_SOURCE,
+		 * MCAST_MSFILTER, IP_MULTICAST_ALL are not supported, better not deal
+		 * with mcast stuff
+		 */
+		/* IP_IPSEC_POLICY, IP_XFRM_POLICY are nut supported, unrelated here */
+		return false;
+	}
+	if (level == SOL_IPV6) {
+		switch (optname) {
+		case IPV6_V6ONLY:
+
+		/* the following are control cmsg related */
+		case IPV6_RECVPKTINFO:
+		case IPV6_2292PKTINFO:
+		case IPV6_RECVHOPLIMIT:
+		case IPV6_2292HOPLIMIT:
+		case IPV6_RECVRTHDR:
+		case IPV6_2292RTHDR:
+		case IPV6_RECVHOPOPTS:
+		case IPV6_2292HOPOPTS:
+		case IPV6_RECVDSTOPTS:
+		case IPV6_2292DSTOPTS:
+		case IPV6_RECVTCLASS:
+		case IPV6_FLOWINFO:
+		case IPV6_RECVPATHMTU:
+		case IPV6_RECVORIGDSTADDR:
+		case IPV6_RECVFRAGSIZE:
+
+		/* the following ones need some love but are quite common */
+		case IPV6_TCLASS:
+		case IPV6_TRANSPARENT:
+		case IPV6_FREEBIND:
+		case IPV6_PKTINFO:
+		case IPV6_2292PKTOPTIONS:
+		case IPV6_UNICAST_HOPS:
+		case IPV6_MTU_DISCOVER:
+		case IPV6_MTU:
+		case IPV6_RECVERR:
+		case IPV6_FLOWINFO_SEND:
+		case IPV6_FLOWLABEL_MGR:
+		case IPV6_MINHOPCOUNT:
+		case IPV6_DONTFRAG:
+		case IPV6_AUTOFLOWLABEL:
+
+		/* the following one is a no-op for plain TCP */
+		case IPV6_RECVERR_RFC4884:
+			return true;
+		}
+
+		/* IPV6_HOPOPTS, IPV6_RTHDRDSTOPTS, IPV6_RTHDR, IPV6_DSTOPTS are
+		 * not supported
+		 */
+		/* IPV6_MULTICAST_HOPS, IPV6_MULTICAST_LOOP, IPV6_UNICAST_IF,
+		 * IPV6_MULTICAST_IF, IPV6_ADDRFORM,
+		 * IPV6_ADD_MEMBERSHIP, IPV6_DROP_MEMBERSHIP, IPV6_JOIN_ANYCAST,
+		 * IPV6_LEAVE_ANYCAST, IPV6_MULTICAST_ALL, MCAST_JOIN_GROUP, MCAST_LEAVE_GROUP,
+		 * MCAST_JOIN_SOURCE_GROUP, MCAST_LEAVE_SOURCE_GROUP,
+		 * MCAST_BLOCK_SOURCE, MCAST_UNBLOCK_SOURCE, MCAST_MSFILTER
+		 * are not supported better not deal with mcast
+		 */
+		/* IPV6_ROUTER_ALERT, IPV6_ROUTER_ALERT_ISOLATE are not supported, since are evil */
+
+		/* IPV6_IPSEC_POLICY, IPV6_XFRM_POLICY are not supported */
+		/* IPV6_ADDR_PREFERENCES is not supported, we must be careful with subflows */
+		return false;
+	}
+	if (level == SOL_TCP) {
+		switch (optname) {
+		/* the following are no-op or should work just fine */
+		case TCP_THIN_DUPACK:
+		case TCP_DEFER_ACCEPT:
+
+		/* the following need some love */
+		case TCP_MAXSEG:
+		case TCP_NODELAY:
+		case TCP_THIN_LINEAR_TIMEOUTS:
+		case TCP_CONGESTION:
+		case TCP_CORK:
+		case TCP_KEEPIDLE:
+		case TCP_KEEPINTVL:
+		case TCP_KEEPCNT:
+		case TCP_SYNCNT:
+		case TCP_SAVE_SYN:
+		case TCP_LINGER2:
+		case TCP_WINDOW_CLAMP:
+		case TCP_QUICKACK:
+		case TCP_USER_TIMEOUT:
+		case TCP_TIMESTAMP:
+		case TCP_NOTSENT_LOWAT:
+		case TCP_TX_DELAY:
+		case TCP_INQ:
+		case TCP_FASTOPEN:
+		case TCP_FASTOPEN_CONNECT:
+		case TCP_FASTOPEN_KEY:
+		case TCP_FASTOPEN_NO_COOKIE:
+			return true;
+		}
+
+		/* TCP_MD5SIG, TCP_MD5SIG_EXT are not supported, MD5 is not compatible with MPTCP */
+
+		/* TCP_REPAIR, TCP_REPAIR_QUEUE, TCP_QUEUE_SEQ, TCP_REPAIR_OPTIONS,
+		 * TCP_REPAIR_WINDOW are not supported, better avoid this mess
+		 */
+	}
+	return false;
+}
+
+static int mptcp_setsockopt_sol_tcp_congestion(struct mptcp_sock *msk, sockptr_t optval,
+					       unsigned int optlen)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	char name[TCP_CA_NAME_MAX];
+	bool cap_net_admin;
+	int ret;
+
+	if (optlen < 1)
+		return -EINVAL;
+
+	ret = strncpy_from_sockptr(name, optval,
+				   min_t(long, TCP_CA_NAME_MAX - 1, optlen));
+	if (ret < 0)
+		return -EFAULT;
+
+	name[ret] = 0;
+
+	cap_net_admin = ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN);
+
+	ret = 0;
+	lock_sock(sk);
+	sockopt_seq_inc(msk);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		int err;
+
+		lock_sock(ssk);
+		err = tcp_set_congestion_control(ssk, name, true, cap_net_admin);
+		if (err < 0 && ret == 0)
+			ret = err;
+		subflow->setsockopt_seq = msk->setsockopt_seq;
+		release_sock(ssk);
+	}
+
+	if (ret == 0)
+		strscpy(msk->ca_name, name, sizeof(msk->ca_name));
+
+	release_sock(sk);
+	return ret;
+}
+
+static int __mptcp_setsockopt_set_val(struct mptcp_sock *msk, int max,
+				      int (*set_val)(struct sock *, int),
+				      int *msk_val, int val)
+{
+	struct mptcp_subflow_context *subflow;
+	int err = 0;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		int ret;
+
+		lock_sock(ssk);
+		ret = set_val(ssk, val);
+		err = err ? : ret;
+		release_sock(ssk);
+	}
+
+	if (!err) {
+		*msk_val = val;
+		sockopt_seq_inc(msk);
+	}
+
+	return err;
+}
+
+static int __mptcp_setsockopt_sol_tcp_cork(struct mptcp_sock *msk, int val)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+
+	sockopt_seq_inc(msk);
+	msk->cork = !!val;
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		lock_sock(ssk);
+		__tcp_sock_set_cork(ssk, !!val);
+		release_sock(ssk);
+	}
+	if (!val)
+		mptcp_check_and_set_pending(sk);
+
+	return 0;
+}
+
+static int __mptcp_setsockopt_sol_tcp_nodelay(struct mptcp_sock *msk, int val)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+
+	sockopt_seq_inc(msk);
+	msk->nodelay = !!val;
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		lock_sock(ssk);
+		__tcp_sock_set_nodelay(ssk, !!val);
+		release_sock(ssk);
+	}
+	if (val)
+		mptcp_check_and_set_pending(sk);
+	return 0;
+}
+
+static int mptcp_setsockopt_sol_ip_set(struct mptcp_sock *msk, int optname,
+				       sockptr_t optval, unsigned int optlen)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct sock *ssk;
+	int err;
+
+	err = ip_setsockopt(sk, SOL_IP, optname, optval, optlen);
+	if (err != 0)
+		return err;
+
+	lock_sock(sk);
+
+	ssk = __mptcp_nmpc_sk(msk);
+	if (IS_ERR(ssk)) {
+		release_sock(sk);
+		return PTR_ERR(ssk);
+	}
+
+	switch (optname) {
+	case IP_FREEBIND:
+		inet_assign_bit(FREEBIND, ssk, inet_test_bit(FREEBIND, sk));
+		break;
+	case IP_TRANSPARENT:
+		inet_assign_bit(TRANSPARENT, ssk,
+				inet_test_bit(TRANSPARENT, sk));
+		break;
+	case IP_BIND_ADDRESS_NO_PORT:
+		inet_assign_bit(BIND_ADDRESS_NO_PORT, ssk,
+				inet_test_bit(BIND_ADDRESS_NO_PORT, sk));
+		break;
+	case IP_LOCAL_PORT_RANGE:
+		WRITE_ONCE(inet_sk(ssk)->local_port_range,
+			   READ_ONCE(inet_sk(sk)->local_port_range));
+		break;
+	default:
+		release_sock(sk);
+		WARN_ON_ONCE(1);
+		return -EOPNOTSUPP;
+	}
+
+	sockopt_seq_inc(msk);
+	release_sock(sk);
+	return 0;
+}
+
+static int mptcp_setsockopt_v4_set_tos(struct mptcp_sock *msk, int optname,
+				       sockptr_t optval, unsigned int optlen)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	int err, val;
+
+	err = ip_setsockopt(sk, SOL_IP, optname, optval, optlen);
+
+	if (err != 0)
+		return err;
+
+	lock_sock(sk);
+	sockopt_seq_inc(msk);
+	val = READ_ONCE(inet_sk(sk)->tos);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow;
+
+		slow = lock_sock_fast(ssk);
+		__ip_sock_set_tos(ssk, val);
+		unlock_sock_fast(ssk, slow);
+	}
+	release_sock(sk);
+
+	return 0;
+}
+
+static int mptcp_setsockopt_v4(struct mptcp_sock *msk, int optname,
+			       sockptr_t optval, unsigned int optlen)
+{
+	switch (optname) {
+	case IP_FREEBIND:
+	case IP_TRANSPARENT:
+	case IP_BIND_ADDRESS_NO_PORT:
+	case IP_LOCAL_PORT_RANGE:
+		return mptcp_setsockopt_sol_ip_set(msk, optname, optval, optlen);
+	case IP_TOS:
+		return mptcp_setsockopt_v4_set_tos(msk, optname, optval, optlen);
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int mptcp_setsockopt_first_sf_only(struct mptcp_sock *msk, int level, int optname,
+					  sockptr_t optval, unsigned int optlen)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct sock *ssk;
+	int ret;
+
+	/* Limit to first subflow, before the connection establishment */
+	lock_sock(sk);
+	ssk = __mptcp_nmpc_sk(msk);
+	if (IS_ERR(ssk)) {
+		ret = PTR_ERR(ssk);
+		goto unlock;
+	}
+
+	ret = tcp_setsockopt(ssk, level, optname, optval, optlen);
+
+unlock:
+	release_sock(sk);
+	return ret;
+}
+
+static int mptcp_setsockopt_all_sf(struct mptcp_sock *msk, int level,
+				   int optname, sockptr_t optval,
+				   unsigned int optlen)
+{
+	struct mptcp_subflow_context *subflow;
+	int ret = 0;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		int err;
+
+		err = tcp_setsockopt(ssk, level, optname, optval, optlen);
+		if (err < 0 && ret == 0)
+			ret = err;
+	}
+
+	if (!ret)
+		sockopt_seq_inc(msk);
+
+	return ret;
+}
+
+static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
+				    sockptr_t optval, unsigned int optlen)
+{
+	struct sock *sk = (void *)msk;
+	int ret, val;
+
+	switch (optname) {
+	case TCP_ULP:
+		return -EOPNOTSUPP;
+	case TCP_CONGESTION:
+		return mptcp_setsockopt_sol_tcp_congestion(msk, optval, optlen);
+	case TCP_DEFER_ACCEPT:
+		/* See tcp.c: TCP_DEFER_ACCEPT does not fail */
+		mptcp_setsockopt_first_sf_only(msk, SOL_TCP, optname, optval, optlen);
+		return 0;
+	case TCP_FASTOPEN:
+	case TCP_FASTOPEN_CONNECT:
+	case TCP_FASTOPEN_KEY:
+	case TCP_FASTOPEN_NO_COOKIE:
+		return mptcp_setsockopt_first_sf_only(msk, SOL_TCP, optname,
+						      optval, optlen);
+	}
+
+	ret = mptcp_get_int_option(msk, optval, optlen, &val);
+	if (ret)
+		return ret;
+
+	lock_sock(sk);
+	switch (optname) {
+	case TCP_INQ:
+		if (val < 0 || val > 1)
+			ret = -EINVAL;
+		else
+			msk->recvmsg_inq = !!val;
+		break;
+	case TCP_NOTSENT_LOWAT:
+		WRITE_ONCE(msk->notsent_lowat, val);
+		mptcp_write_space(sk);
+		break;
+	case TCP_CORK:
+		ret = __mptcp_setsockopt_sol_tcp_cork(msk, val);
+		break;
+	case TCP_NODELAY:
+		ret = __mptcp_setsockopt_sol_tcp_nodelay(msk, val);
+		break;
+	case TCP_KEEPIDLE:
+		ret = __mptcp_setsockopt_set_val(msk, MAX_TCP_KEEPIDLE,
+						 &tcp_sock_set_keepidle_locked,
+						 &msk->keepalive_idle, val);
+		break;
+	case TCP_KEEPINTVL:
+		ret = __mptcp_setsockopt_set_val(msk, MAX_TCP_KEEPINTVL,
+						 &tcp_sock_set_keepintvl,
+						 &msk->keepalive_intvl, val);
+		break;
+	case TCP_KEEPCNT:
+		ret = __mptcp_setsockopt_set_val(msk, MAX_TCP_KEEPCNT,
+						 &tcp_sock_set_keepcnt,
+						 &msk->keepalive_cnt,
+						 val);
+		break;
+	case TCP_MAXSEG:
+		msk->maxseg = val;
+		ret = mptcp_setsockopt_all_sf(msk, SOL_TCP, optname, optval,
+					      optlen);
+		break;
+	default:
+		ret = -ENOPROTOOPT;
+	}
+
+	release_sock(sk);
+	return ret;
+}
+
+int mptcp_setsockopt(struct sock *sk, int level, int optname,
+		     sockptr_t optval, unsigned int optlen)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sock *ssk;
+
+	pr_debug("msk=%p\n", msk);
+
+	if (level == SOL_SOCKET)
+		return mptcp_setsockopt_sol_socket(msk, optname, optval, optlen);
+
+	if (!mptcp_supported_sockopt(level, optname))
+		return -ENOPROTOOPT;
+
+	/* @@ the meaning of setsockopt() when the socket is connected and
+	 * there are multiple subflows is not yet defined. It is up to the
+	 * MPTCP-level socket to configure the subflows until the subflow
+	 * is in TCP fallback, when TCP socket options are passed through
+	 * to the one remaining subflow.
+	 */
+	lock_sock(sk);
+	ssk = __mptcp_tcp_fallback(msk);
+	release_sock(sk);
+	if (ssk)
+		return tcp_setsockopt(ssk, level, optname, optval, optlen);
+
+	if (level == SOL_IP)
+		return mptcp_setsockopt_v4(msk, optname, optval, optlen);
+
+	if (level == SOL_IPV6)
+		return mptcp_setsockopt_v6(msk, optname, optval, optlen);
+
+	if (level == SOL_TCP)
+		return mptcp_setsockopt_sol_tcp(msk, optname, optval, optlen);
+
+	return -EOPNOTSUPP;
+}
+
+static int mptcp_getsockopt_first_sf_only(struct mptcp_sock *msk, int level, int optname,
+					  char __user *optval, int __user *optlen)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct sock *ssk;
+	int ret;
+
+	lock_sock(sk);
+	ssk = msk->first;
+	if (ssk)
+		goto get;
+
+	ssk = __mptcp_nmpc_sk(msk);
+	if (IS_ERR(ssk)) {
+		ret = PTR_ERR(ssk);
+		goto out;
+	}
+
+get:
+	ret = tcp_getsockopt(ssk, level, optname, optval, optlen);
+
+out:
+	release_sock(sk);
+	return ret;
+}
+
+void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
+{
+	struct sock *sk = (struct sock *)msk;
+	u32 flags = 0;
+	bool slow;
+	u32 now;
+
+	memset(info, 0, sizeof(*info));
+
+	info->mptcpi_extra_subflows = READ_ONCE(msk->pm.extra_subflows);
+	info->mptcpi_add_addr_signal = READ_ONCE(msk->pm.add_addr_signaled);
+	info->mptcpi_add_addr_accepted = READ_ONCE(msk->pm.add_addr_accepted);
+	info->mptcpi_local_addr_used = READ_ONCE(msk->pm.local_addr_used);
+
+	if (inet_sk_state_load(sk) == TCP_LISTEN)
+		return;
+
+	/* The following limits only make sense for the in-kernel PM */
+	if (mptcp_pm_is_kernel(msk)) {
+		info->mptcpi_limit_extra_subflows =
+			mptcp_pm_get_limit_extra_subflows(msk);
+		info->mptcpi_endp_signal_max =
+			mptcp_pm_get_endp_signal_max(msk);
+		info->mptcpi_limit_add_addr_accepted =
+			mptcp_pm_get_limit_add_addr_accepted(msk);
+		info->mptcpi_endp_subflow_max =
+			mptcp_pm_get_endp_subflow_max(msk);
+		info->mptcpi_endp_laminar_max =
+			mptcp_pm_get_endp_laminar_max(msk);
+		info->mptcpi_endp_fullmesh_max =
+			mptcp_pm_get_endp_fullmesh_max(msk);
+	}
+
+	if (__mptcp_check_fallback(msk))
+		flags |= MPTCP_INFO_FLAG_FALLBACK;
+	if (READ_ONCE(msk->can_ack))
+		flags |= MPTCP_INFO_FLAG_REMOTE_KEY_RECEIVED;
+	info->mptcpi_flags = flags;
+
+	slow = lock_sock_fast(sk);
+	info->mptcpi_csum_enabled = READ_ONCE(msk->csum_enabled);
+	info->mptcpi_token = msk->token;
+	info->mptcpi_write_seq = msk->write_seq;
+	info->mptcpi_retransmits = inet_csk(sk)->icsk_retransmits;
+	info->mptcpi_bytes_sent = msk->bytes_sent;
+	info->mptcpi_bytes_received = msk->bytes_received;
+	info->mptcpi_bytes_retrans = msk->bytes_retrans;
+	info->mptcpi_subflows_total = info->mptcpi_extra_subflows +
+		__mptcp_has_initial_subflow(msk);
+	now = tcp_jiffies32;
+	info->mptcpi_last_data_sent = jiffies_to_msecs(now - msk->last_data_sent);
+	info->mptcpi_last_data_recv = jiffies_to_msecs(now - msk->last_data_recv);
+	unlock_sock_fast(sk, slow);
+
+	mptcp_data_lock(sk);
+	info->mptcpi_last_ack_recv = jiffies_to_msecs(now - msk->last_ack_recv);
+	info->mptcpi_snd_una = msk->snd_una;
+	info->mptcpi_rcv_nxt = msk->ack_seq;
+	info->mptcpi_bytes_acked = msk->bytes_acked;
+	mptcp_data_unlock(sk);
+}
+EXPORT_SYMBOL_GPL(mptcp_diag_fill_info);
+
+static int mptcp_getsockopt_info(struct mptcp_sock *msk, char __user *optval, int __user *optlen)
+{
+	struct mptcp_info m_info;
+	int len;
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+
+	/* When used only to check if a fallback to TCP happened. */
+	if (len == 0)
+		return 0;
+
+	len = min_t(unsigned int, len, sizeof(struct mptcp_info));
+
+	mptcp_diag_fill_info(msk, &m_info);
+
+	if (put_user(len, optlen))
+		return -EFAULT;
+
+	if (copy_to_user(optval, &m_info, len))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int mptcp_put_subflow_data(struct mptcp_subflow_data *sfd,
+				  char __user *optval,
+				  u32 copied,
+				  int __user *optlen)
+{
+	u32 copylen = min_t(u32, sfd->size_subflow_data, sizeof(*sfd));
+
+	if (copied)
+		copied += sfd->size_subflow_data;
+	else
+		copied = copylen;
+
+	if (put_user(copied, optlen))
+		return -EFAULT;
+
+	if (copy_to_user(optval, sfd, copylen))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int mptcp_get_subflow_data(struct mptcp_subflow_data *sfd,
+				  char __user *optval,
+				  int __user *optlen)
+{
+	int len, copylen;
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+
+	/* if mptcp_subflow_data size is changed, need to adjust
+	 * this function to deal with programs using old version.
+	 */
+	BUILD_BUG_ON(sizeof(*sfd) != MIN_INFO_OPTLEN_SIZE);
+
+	if (len < MIN_INFO_OPTLEN_SIZE)
+		return -EINVAL;
+
+	memset(sfd, 0, sizeof(*sfd));
+
+	copylen = min_t(unsigned int, len, sizeof(*sfd));
+	if (copy_from_user(sfd, optval, copylen))
+		return -EFAULT;
+
+	/* size_subflow_data is u32, but len is signed */
+	if (sfd->size_subflow_data > INT_MAX ||
+	    sfd->size_user > INT_MAX)
+		return -EINVAL;
+
+	if (sfd->size_subflow_data < MIN_INFO_OPTLEN_SIZE ||
+	    sfd->size_subflow_data > len)
+		return -EINVAL;
+
+	if (sfd->num_subflows || sfd->size_kernel)
+		return -EINVAL;
+
+	return len - sfd->size_subflow_data;
+}
+
+static int mptcp_getsockopt_tcpinfo(struct mptcp_sock *msk, char __user *optval,
+				    int __user *optlen)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	unsigned int sfcount = 0, copied = 0;
+	struct mptcp_subflow_data sfd;
+	char __user *infoptr;
+	int len;
+
+	len = mptcp_get_subflow_data(&sfd, optval, optlen);
+	if (len < 0)
+		return len;
+
+	sfd.size_kernel = sizeof(struct tcp_info);
+	sfd.size_user = min_t(unsigned int, sfd.size_user,
+			      sizeof(struct tcp_info));
+
+	infoptr = optval + sfd.size_subflow_data;
+
+	lock_sock(sk);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		++sfcount;
+
+		if (len && len >= sfd.size_user) {
+			struct tcp_info info;
+
+			tcp_get_info(ssk, &info);
+
+			if (copy_to_user(infoptr, &info, sfd.size_user)) {
+				release_sock(sk);
+				return -EFAULT;
+			}
+
+			infoptr += sfd.size_user;
+			copied += sfd.size_user;
+			len -= sfd.size_user;
+		}
+	}
+
+	release_sock(sk);
+
+	sfd.num_subflows = sfcount;
+
+	if (mptcp_put_subflow_data(&sfd, optval, copied, optlen))
+		return -EFAULT;
+
+	return 0;
+}
+
+static void mptcp_get_sub_addrs(const struct sock *sk, struct mptcp_subflow_addrs *a)
+{
+	const struct inet_sock *inet = inet_sk(sk);
+
+	memset(a, 0, sizeof(*a));
+
+	if (sk->sk_family == AF_INET) {
+		a->sin_local.sin_family = AF_INET;
+		a->sin_local.sin_port = inet->inet_sport;
+		a->sin_local.sin_addr.s_addr = inet->inet_rcv_saddr;
+
+		if (!a->sin_local.sin_addr.s_addr)
+			a->sin_local.sin_addr.s_addr = inet->inet_saddr;
+
+		a->sin_remote.sin_family = AF_INET;
+		a->sin_remote.sin_port = inet->inet_dport;
+		a->sin_remote.sin_addr.s_addr = inet->inet_daddr;
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (sk->sk_family == AF_INET6) {
+		const struct ipv6_pinfo *np = inet6_sk(sk);
+
+		if (WARN_ON_ONCE(!np))
+			return;
+
+		a->sin6_local.sin6_family = AF_INET6;
+		a->sin6_local.sin6_port = inet->inet_sport;
+
+		if (ipv6_addr_any(&sk->sk_v6_rcv_saddr))
+			a->sin6_local.sin6_addr = np->saddr;
+		else
+			a->sin6_local.sin6_addr = sk->sk_v6_rcv_saddr;
+
+		a->sin6_remote.sin6_family = AF_INET6;
+		a->sin6_remote.sin6_port = inet->inet_dport;
+		a->sin6_remote.sin6_addr = sk->sk_v6_daddr;
+#endif
+	}
+}
+
+static int mptcp_getsockopt_subflow_addrs(struct mptcp_sock *msk, char __user *optval,
+					  int __user *optlen)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	unsigned int sfcount = 0, copied = 0;
+	struct mptcp_subflow_data sfd;
+	char __user *addrptr;
+	int len;
+
+	len = mptcp_get_subflow_data(&sfd, optval, optlen);
+	if (len < 0)
+		return len;
+
+	sfd.size_kernel = sizeof(struct mptcp_subflow_addrs);
+	sfd.size_user = min_t(unsigned int, sfd.size_user,
+			      sizeof(struct mptcp_subflow_addrs));
+
+	addrptr = optval + sfd.size_subflow_data;
+
+	lock_sock(sk);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		++sfcount;
+
+		if (len && len >= sfd.size_user) {
+			struct mptcp_subflow_addrs a;
+
+			mptcp_get_sub_addrs(ssk, &a);
+
+			if (copy_to_user(addrptr, &a, sfd.size_user)) {
+				release_sock(sk);
+				return -EFAULT;
+			}
+
+			addrptr += sfd.size_user;
+			copied += sfd.size_user;
+			len -= sfd.size_user;
+		}
+	}
+
+	release_sock(sk);
+
+	sfd.num_subflows = sfcount;
+
+	if (mptcp_put_subflow_data(&sfd, optval, copied, optlen))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int mptcp_get_full_info(struct mptcp_full_info *mfi,
+			       char __user *optval,
+			       int __user *optlen)
+{
+	int len;
+
+	BUILD_BUG_ON(offsetof(struct mptcp_full_info, mptcp_info) !=
+		     MIN_FULL_INFO_OPTLEN_SIZE);
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+
+	if (len < MIN_FULL_INFO_OPTLEN_SIZE)
+		return -EINVAL;
+
+	memset(mfi, 0, sizeof(*mfi));
+	if (copy_from_user(mfi, optval, MIN_FULL_INFO_OPTLEN_SIZE))
+		return -EFAULT;
+
+	if (mfi->size_tcpinfo_kernel ||
+	    mfi->size_sfinfo_kernel ||
+	    mfi->num_subflows)
+		return -EINVAL;
+
+	if (mfi->size_sfinfo_user > INT_MAX ||
+	    mfi->size_tcpinfo_user > INT_MAX)
+		return -EINVAL;
+
+	return len - MIN_FULL_INFO_OPTLEN_SIZE;
+}
+
+static int mptcp_put_full_info(struct mptcp_full_info *mfi,
+			       char __user *optval,
+			       u32 copylen,
+			       int __user *optlen)
+{
+	copylen += MIN_FULL_INFO_OPTLEN_SIZE;
+	if (put_user(copylen, optlen))
+		return -EFAULT;
+
+	if (copy_to_user(optval, mfi, copylen))
+		return -EFAULT;
+	return 0;
+}
+
+static int mptcp_getsockopt_full_info(struct mptcp_sock *msk, char __user *optval,
+				      int __user *optlen)
+{
+	unsigned int sfcount = 0, copylen = 0;
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	void __user *tcpinfoptr, *sfinfoptr;
+	struct mptcp_full_info mfi;
+	int len;
+
+	len = mptcp_get_full_info(&mfi, optval, optlen);
+	if (len < 0)
+		return len;
+
+	/* don't bother filling the mptcp info if there is not enough
+	 * user-space-provided storage
+	 */
+	if (len > 0) {
+		mptcp_diag_fill_info(msk, &mfi.mptcp_info);
+		copylen += min_t(unsigned int, len, sizeof(struct mptcp_info));
+	}
+
+	mfi.size_tcpinfo_kernel = sizeof(struct tcp_info);
+	mfi.size_tcpinfo_user = min_t(unsigned int, mfi.size_tcpinfo_user,
+				      sizeof(struct tcp_info));
+	sfinfoptr = u64_to_user_ptr(mfi.subflow_info);
+	mfi.size_sfinfo_kernel = sizeof(struct mptcp_subflow_info);
+	mfi.size_sfinfo_user = min_t(unsigned int, mfi.size_sfinfo_user,
+				     sizeof(struct mptcp_subflow_info));
+	tcpinfoptr = u64_to_user_ptr(mfi.tcp_info);
+
+	lock_sock(sk);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		struct mptcp_subflow_info sfinfo;
+		struct tcp_info tcp_info;
+
+		if (sfcount++ >= mfi.size_arrays_user)
+			continue;
+
+		/* fetch addr/tcp_info only if the user space buffers
+		 * are wide enough
+		 */
+		memset(&sfinfo, 0, sizeof(sfinfo));
+		sfinfo.id = subflow->subflow_id;
+		if (mfi.size_sfinfo_user >
+		    offsetof(struct mptcp_subflow_info, addrs))
+			mptcp_get_sub_addrs(ssk, &sfinfo.addrs);
+		if (copy_to_user(sfinfoptr, &sfinfo, mfi.size_sfinfo_user))
+			goto fail_release;
+
+		if (mfi.size_tcpinfo_user) {
+			tcp_get_info(ssk, &tcp_info);
+			if (copy_to_user(tcpinfoptr, &tcp_info,
+					 mfi.size_tcpinfo_user))
+				goto fail_release;
+		}
+
+		tcpinfoptr += mfi.size_tcpinfo_user;
+		sfinfoptr += mfi.size_sfinfo_user;
+	}
+	release_sock(sk);
+
+	mfi.num_subflows = sfcount;
+	if (mptcp_put_full_info(&mfi, optval, copylen, optlen))
+		return -EFAULT;
+
+	return 0;
+
+fail_release:
+	release_sock(sk);
+	return -EFAULT;
+}
+
+static int mptcp_put_int_option(struct mptcp_sock *msk, char __user *optval,
+				int __user *optlen, int val)
+{
+	int len;
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+	if (len < 0)
+		return -EINVAL;
+
+	if (len < sizeof(int) && len > 0 && val >= 0 && val <= 255) {
+		unsigned char ucval = (unsigned char)val;
+
+		len = 1;
+		if (put_user(len, optlen))
+			return -EFAULT;
+		if (copy_to_user(optval, &ucval, 1))
+			return -EFAULT;
+	} else {
+		len = min_t(unsigned int, len, sizeof(int));
+		if (put_user(len, optlen))
+			return -EFAULT;
+		if (copy_to_user(optval, &val, len))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+static int mptcp_getsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
+				    char __user *optval, int __user *optlen)
+{
+	struct sock *sk = (void *)msk;
+
+	switch (optname) {
+	case TCP_ULP:
+	case TCP_CONGESTION:
+	case TCP_INFO:
+	case TCP_CC_INFO:
+	case TCP_DEFER_ACCEPT:
+	case TCP_FASTOPEN:
+	case TCP_FASTOPEN_CONNECT:
+	case TCP_FASTOPEN_KEY:
+	case TCP_FASTOPEN_NO_COOKIE:
+		return mptcp_getsockopt_first_sf_only(msk, SOL_TCP, optname,
+						      optval, optlen);
+	case TCP_INQ:
+		return mptcp_put_int_option(msk, optval, optlen, msk->recvmsg_inq);
+	case TCP_CORK:
+		return mptcp_put_int_option(msk, optval, optlen, msk->cork);
+	case TCP_NODELAY:
+		return mptcp_put_int_option(msk, optval, optlen, msk->nodelay);
+	case TCP_KEEPIDLE:
+		return mptcp_put_int_option(msk, optval, optlen,
+					    msk->keepalive_idle ? :
+					    READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_keepalive_time) / HZ);
+	case TCP_KEEPINTVL:
+		return mptcp_put_int_option(msk, optval, optlen,
+					    msk->keepalive_intvl ? :
+					    READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_keepalive_intvl) / HZ);
+	case TCP_KEEPCNT:
+		return mptcp_put_int_option(msk, optval, optlen,
+					    msk->keepalive_cnt ? :
+					    READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_keepalive_probes));
+	case TCP_NOTSENT_LOWAT:
+		return mptcp_put_int_option(msk, optval, optlen, msk->notsent_lowat);
+	case TCP_IS_MPTCP:
+		return mptcp_put_int_option(msk, optval, optlen, 1);
+	case TCP_MAXSEG:
+		return mptcp_getsockopt_first_sf_only(msk, SOL_TCP, optname,
+						      optval, optlen);
+	}
+	return -EOPNOTSUPP;
+}
+
+static int mptcp_getsockopt_v4(struct mptcp_sock *msk, int optname,
+			       char __user *optval, int __user *optlen)
+{
+	struct sock *sk = (void *)msk;
+
+	switch (optname) {
+	case IP_TOS:
+		return mptcp_put_int_option(msk, optval, optlen, READ_ONCE(inet_sk(sk)->tos));
+	case IP_FREEBIND:
+		return mptcp_put_int_option(msk, optval, optlen,
+				inet_test_bit(FREEBIND, sk));
+	case IP_TRANSPARENT:
+		return mptcp_put_int_option(msk, optval, optlen,
+				inet_test_bit(TRANSPARENT, sk));
+	case IP_BIND_ADDRESS_NO_PORT:
+		return mptcp_put_int_option(msk, optval, optlen,
+				inet_test_bit(BIND_ADDRESS_NO_PORT, sk));
+	case IP_LOCAL_PORT_RANGE:
+		return mptcp_put_int_option(msk, optval, optlen,
+				READ_ONCE(inet_sk(sk)->local_port_range));
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int mptcp_getsockopt_v6(struct mptcp_sock *msk, int optname,
+			       char __user *optval, int __user *optlen)
+{
+	struct sock *sk = (void *)msk;
+
+	switch (optname) {
+	case IPV6_V6ONLY:
+		return mptcp_put_int_option(msk, optval, optlen,
+					    sk->sk_ipv6only);
+	case IPV6_TRANSPARENT:
+		return mptcp_put_int_option(msk, optval, optlen,
+					    inet_test_bit(TRANSPARENT, sk));
+	case IPV6_FREEBIND:
+		return mptcp_put_int_option(msk, optval, optlen,
+					    inet_test_bit(FREEBIND, sk));
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int mptcp_getsockopt_sol_mptcp(struct mptcp_sock *msk, int optname,
+				      char __user *optval, int __user *optlen)
+{
+	switch (optname) {
+	case MPTCP_INFO:
+		return mptcp_getsockopt_info(msk, optval, optlen);
+	case MPTCP_FULL_INFO:
+		return mptcp_getsockopt_full_info(msk, optval, optlen);
+	case MPTCP_TCPINFO:
+		return mptcp_getsockopt_tcpinfo(msk, optval, optlen);
+	case MPTCP_SUBFLOW_ADDRS:
+		return mptcp_getsockopt_subflow_addrs(msk, optval, optlen);
+	}
+
+	return -EOPNOTSUPP;
+}
+
+int mptcp_getsockopt(struct sock *sk, int level, int optname,
+		     char __user *optval, int __user *option)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sock *ssk;
+
+	pr_debug("msk=%p\n", msk);
+
+	/* @@ the meaning of setsockopt() when the socket is connected and
+	 * there are multiple subflows is not yet defined. It is up to the
+	 * MPTCP-level socket to configure the subflows until the subflow
+	 * is in TCP fallback, when socket options are passed through
+	 * to the one remaining subflow.
+	 */
+	lock_sock(sk);
+	ssk = __mptcp_tcp_fallback(msk);
+	release_sock(sk);
+	if (ssk)
+		return tcp_getsockopt(ssk, level, optname, optval, option);
+
+	if (level == SOL_IP)
+		return mptcp_getsockopt_v4(msk, optname, optval, option);
+	if (level == SOL_IPV6)
+		return mptcp_getsockopt_v6(msk, optname, optval, option);
+	if (level == SOL_TCP)
+		return mptcp_getsockopt_sol_tcp(msk, optname, optval, option);
+	if (level == SOL_MPTCP)
+		return mptcp_getsockopt_sol_mptcp(msk, optname, optval, option);
+	return -EOPNOTSUPP;
+}
+
+static void sync_socket_options(struct mptcp_sock *msk, struct sock *ssk)
+{
+	static const unsigned int tx_rx_locks = SOCK_RCVBUF_LOCK | SOCK_SNDBUF_LOCK;
+	struct sock *sk = (struct sock *)msk;
+	bool keep_open;
+
+	keep_open = sock_flag(sk, SOCK_KEEPOPEN);
+	if (ssk->sk_prot->keepalive)
+		ssk->sk_prot->keepalive(ssk, keep_open);
+	sock_valbool_flag(ssk, SOCK_KEEPOPEN, keep_open);
+
+	ssk->sk_priority = sk->sk_priority;
+	ssk->sk_bound_dev_if = sk->sk_bound_dev_if;
+	ssk->sk_incoming_cpu = sk->sk_incoming_cpu;
+	ssk->sk_ipv6only = sk->sk_ipv6only;
+	__ip_sock_set_tos(ssk, inet_sk(sk)->tos);
+
+	if (sk->sk_userlocks & tx_rx_locks) {
+		ssk->sk_userlocks |= sk->sk_userlocks & tx_rx_locks;
+		if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) {
+			WRITE_ONCE(ssk->sk_sndbuf, sk->sk_sndbuf);
+			mptcp_subflow_ctx(ssk)->cached_sndbuf = sk->sk_sndbuf;
+		}
+		if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
+			__mptcp_subflow_set_rcvbuf(ssk, sk->sk_rcvbuf);
+	}
+
+	if (sock_flag(sk, SOCK_LINGER)) {
+		ssk->sk_lingertime = sk->sk_lingertime;
+		sock_set_flag(ssk, SOCK_LINGER);
+	} else {
+		sock_reset_flag(ssk, SOCK_LINGER);
+	}
+
+	if (sk->sk_mark != ssk->sk_mark) {
+		ssk->sk_mark = sk->sk_mark;
+		sk_dst_reset(ssk);
+	}
+
+	sock_valbool_flag(ssk, SOCK_DBG, sock_flag(sk, SOCK_DBG));
+
+	if (inet_csk(sk)->icsk_ca_ops != inet_csk(ssk)->icsk_ca_ops)
+		tcp_set_congestion_control(ssk, msk->ca_name, false, true);
+	__tcp_sock_set_cork(ssk, !!msk->cork);
+	__tcp_sock_set_nodelay(ssk, !!msk->nodelay);
+	tcp_sock_set_keepidle_locked(ssk, msk->keepalive_idle);
+	tcp_sock_set_keepintvl(ssk, msk->keepalive_intvl);
+	tcp_sock_set_keepcnt(ssk, msk->keepalive_cnt);
+	tcp_sock_set_maxseg(ssk, msk->maxseg);
+
+	inet_assign_bit(TRANSPARENT, ssk, inet_test_bit(TRANSPARENT, sk));
+	inet_assign_bit(FREEBIND, ssk, inet_test_bit(FREEBIND, sk));
+	inet_assign_bit(BIND_ADDRESS_NO_PORT, ssk, inet_test_bit(BIND_ADDRESS_NO_PORT, sk));
+	WRITE_ONCE(inet_sk(ssk)->local_port_range, READ_ONCE(inet_sk(sk)->local_port_range));
+}
+
+void mptcp_sockopt_sync_locked(struct mptcp_sock *msk, struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+
+	msk_owned_by_me(msk);
+
+	ssk->sk_rcvlowat = 0;
+
+	/* subflows must ignore any latency-related settings: will not affect
+	 * the user-space - only the msk is relevant - but will foul the
+	 * mptcp scheduler
+	 */
+	tcp_sk(ssk)->notsent_lowat = UINT_MAX;
+
+	if (READ_ONCE(subflow->setsockopt_seq) != msk->setsockopt_seq) {
+		sync_socket_options(msk, ssk);
+
+		subflow->setsockopt_seq = msk->setsockopt_seq;
+	}
+}
+
+/* unfortunately this is different enough from the tcp version so
+ * that we can't factor it out
+ */
+int mptcp_set_rcvlowat(struct sock *sk, int val)
+{
+	struct mptcp_subflow_context *subflow;
+	int space, cap;
+
+	/* bpf can land here with a wrong sk type */
+	if (sk->sk_protocol == IPPROTO_TCP)
+		return -EINVAL;
+
+	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
+		cap = sk->sk_rcvbuf >> 1;
+	else
+		cap = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]) >> 1;
+	val = min(val, cap);
+	WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);
+
+	/* Check if we need to signal EPOLLIN right now */
+	if (mptcp_epollin_ready(sk))
+		sk->sk_data_ready(sk);
+
+	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
+		return 0;
+
+	space = mptcp_space_from_win(sk, val);
+	if (space <= sk->sk_rcvbuf)
+		return 0;
+
+	/* propagate the rcvbuf changes to all the subflows */
+	WRITE_ONCE(sk->sk_rcvbuf, space);
+	mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow;
+
+		slow = lock_sock_fast(ssk);
+		WRITE_ONCE(ssk->sk_rcvbuf, space);
+		WRITE_ONCE(tcp_sk(ssk)->window_clamp, val);
+		unlock_sock_fast(ssk, slow);
+	}
+	return 0;
+}
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
new file mode 100644
index 000000000..01db7edce
--- /dev/null
+++ b/net/mptcp/subflow.c
@@ -0,0 +1,2219 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <crypto/sha2.h>
+#include <crypto/utils.h>
+#include <net/sock.h>
+#include <net/inet_common.h>
+#include <net/inet_hashtables.h>
+#include <net/protocol.h>
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+#include <net/ip6_route.h>
+#include <net/transp_v6.h>
+#endif
+#include <net/mptcp.h>
+
+#include "protocol.h"
+#include "mib.h"
+
+#include <trace/events/mptcp.h>
+#include <trace/events/sock.h>
+
+static void mptcp_subflow_ops_undo_override(struct sock *ssk);
+
+static void SUBFLOW_REQ_INC_STATS(struct request_sock *req,
+				  enum linux_mptcp_mib_field field)
+{
+	MPTCP_INC_STATS(sock_net(req_to_sk(req)), field);
+}
+
+static void subflow_req_destructor(struct request_sock *req)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+
+	pr_debug("subflow_req=%p\n", subflow_req);
+
+	if (subflow_req->msk)
+		sock_put((struct sock *)subflow_req->msk);
+
+	mptcp_token_destroy_request(req);
+}
+
+static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2,
+				  void *hmac)
+{
+	u8 msg[8];
+
+	put_unaligned_be32(nonce1, &msg[0]);
+	put_unaligned_be32(nonce2, &msg[4]);
+
+	mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
+}
+
+static bool mptcp_can_accept_new_subflow(const struct mptcp_sock *msk)
+{
+	return mptcp_is_fully_established((void *)msk) &&
+		((mptcp_pm_is_userspace(msk) &&
+		  mptcp_userspace_pm_active(msk)) ||
+		 READ_ONCE(msk->pm.accept_subflow));
+}
+
+/* validate received token and create truncated hmac and nonce for SYN-ACK */
+static void subflow_req_create_thmac(struct mptcp_subflow_request_sock *subflow_req)
+{
+	struct mptcp_sock *msk = subflow_req->msk;
+	u8 hmac[SHA256_DIGEST_SIZE];
+
+	subflow_req->local_nonce = get_random_u32();
+
+	subflow_generate_hmac(READ_ONCE(msk->local_key),
+			      READ_ONCE(msk->remote_key),
+			      subflow_req->local_nonce,
+			      subflow_req->remote_nonce, hmac);
+
+	subflow_req->thmac = get_unaligned_be64(hmac);
+}
+
+static struct mptcp_sock *subflow_token_join_request(struct request_sock *req)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct mptcp_sock *msk;
+	int local_id;
+
+	msk = mptcp_token_get_sock(sock_net(req_to_sk(req)), subflow_req->token);
+	if (!msk) {
+		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINNOTOKEN);
+		return NULL;
+	}
+
+	local_id = mptcp_pm_get_local_id(msk, (struct sock_common *)req);
+	if (local_id < 0) {
+		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPJOINNOIDFOUND);
+		sock_put((struct sock *)msk);
+		return NULL;
+	}
+	subflow_req->local_id = local_id;
+	subflow_req->request_bkup = mptcp_pm_is_backup(msk, (struct sock_common *)req);
+
+	return msk;
+}
+
+static void subflow_init_req(struct request_sock *req, const struct sock *sk_listener)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+
+	subflow_req->mp_capable = 0;
+	subflow_req->mp_join = 0;
+	subflow_req->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk_listener));
+	subflow_req->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk_listener));
+	subflow_req->msk = NULL;
+	mptcp_token_init_request(req);
+}
+
+static bool subflow_use_different_sport(struct mptcp_sock *msk, const struct sock *sk)
+{
+	return inet_sk(sk)->inet_sport != inet_sk((struct sock *)msk)->inet_sport;
+}
+
+static void subflow_add_reset_reason(struct sk_buff *skb, u8 reason)
+{
+	struct mptcp_ext *mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
+
+	if (mpext) {
+		memset(mpext, 0, sizeof(*mpext));
+		mpext->reset_reason = reason;
+	}
+}
+
+static int subflow_reset_req_endp(struct request_sock *req, struct sk_buff *skb)
+{
+	SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEENDPATTEMPT);
+	subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
+	return -EPERM;
+}
+
+/* Init mptcp request socket.
+ *
+ * Returns an error code if a JOIN has failed and a TCP reset
+ * should be sent.
+ */
+static int subflow_check_req(struct request_sock *req,
+			     const struct sock *sk_listener,
+			     struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct mptcp_options_received mp_opt;
+	bool opt_mp_capable, opt_mp_join;
+
+	pr_debug("subflow_req=%p, listener=%p\n", subflow_req, listener);
+
+#ifdef CONFIG_TCP_MD5SIG
+	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
+	 * TCP option space.
+	 */
+	if (rcu_access_pointer(tcp_sk(sk_listener)->md5sig_info)) {
+		MPTCP_INC_STATS(sock_net(sk_listener), MPTCP_MIB_MD5SIGRESET);
+		subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
+		return -EINVAL;
+	}
+#endif
+
+	mptcp_get_options(skb, &mp_opt);
+
+	opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYN);
+	opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_SYN);
+	if (opt_mp_capable) {
+		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVE);
+
+		if (unlikely(listener->pm_listener))
+			return subflow_reset_req_endp(req, skb);
+	} else if (opt_mp_join) {
+		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNRX);
+
+		if (mp_opt.backup)
+			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNBACKUPRX);
+	} else if (unlikely(listener->pm_listener)) {
+		return subflow_reset_req_endp(req, skb);
+	}
+
+	if (opt_mp_capable && listener->request_mptcp) {
+		int err, retries = MPTCP_TOKEN_MAX_RETRIES;
+
+		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
+again:
+		do {
+			get_random_bytes(&subflow_req->local_key, sizeof(subflow_req->local_key));
+		} while (subflow_req->local_key == 0);
+
+		if (unlikely(req->syncookie)) {
+			mptcp_crypto_key_sha(subflow_req->local_key,
+					     &subflow_req->token,
+					     &subflow_req->idsn);
+			if (mptcp_token_exists(subflow_req->token)) {
+				if (retries-- > 0)
+					goto again;
+				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
+			} else {
+				subflow_req->mp_capable = 1;
+			}
+			return 0;
+		}
+
+		err = mptcp_token_new_request(req);
+		if (err == 0)
+			subflow_req->mp_capable = 1;
+		else if (retries-- > 0)
+			goto again;
+		else
+			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
+
+	} else if (opt_mp_join && listener->request_mptcp) {
+		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
+		subflow_req->mp_join = 1;
+		subflow_req->backup = mp_opt.backup;
+		subflow_req->remote_id = mp_opt.join_id;
+		subflow_req->token = mp_opt.token;
+		subflow_req->remote_nonce = mp_opt.nonce;
+		subflow_req->msk = subflow_token_join_request(req);
+
+		/* Can't fall back to TCP in this case. */
+		if (!subflow_req->msk) {
+			subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
+			return -EPERM;
+		}
+
+		if (subflow_use_different_sport(subflow_req->msk, sk_listener)) {
+			pr_debug("syn inet_sport=%d %d\n",
+				 ntohs(inet_sk(sk_listener)->inet_sport),
+				 ntohs(inet_sk((struct sock *)subflow_req->msk)->inet_sport));
+			if (!mptcp_pm_announced_has_ssk(subflow_req->msk, sk_listener)) {
+				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTSYNRX);
+				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
+				return -EPERM;
+			}
+			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTSYNRX);
+		}
+
+		subflow_req_create_thmac(subflow_req);
+
+		if (unlikely(req->syncookie)) {
+			if (!mptcp_can_accept_new_subflow(subflow_req->msk)) {
+				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINREJECTED);
+				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
+				return -EPERM;
+			}
+
+			subflow_init_req_cookie_join_save(subflow_req, skb);
+		}
+
+		pr_debug("token=%u, remote_nonce=%u msk=%p\n", subflow_req->token,
+			 subflow_req->remote_nonce, subflow_req->msk);
+	}
+
+	return 0;
+}
+
+int mptcp_subflow_init_cookie_req(struct request_sock *req,
+				  const struct sock *sk_listener,
+				  struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct mptcp_options_received mp_opt;
+	bool opt_mp_capable, opt_mp_join;
+	int err;
+
+	subflow_init_req(req, sk_listener);
+	mptcp_get_options(skb, &mp_opt);
+
+	opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_ACK);
+	opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK);
+	if (opt_mp_capable && listener->request_mptcp) {
+		if (mp_opt.sndr_key == 0)
+			return -EINVAL;
+
+		subflow_req->local_key = mp_opt.rcvr_key;
+		err = mptcp_token_new_request(req);
+		if (err)
+			return err;
+
+		subflow_req->mp_capable = 1;
+		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
+	} else if (opt_mp_join && listener->request_mptcp) {
+		if (!mptcp_token_join_cookie_init_state(subflow_req, skb))
+			return -EINVAL;
+
+		subflow_req->mp_join = 1;
+		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
+
+static enum sk_rst_reason mptcp_get_rst_reason(const struct sk_buff *skb)
+{
+	const struct mptcp_ext *mpext = mptcp_get_ext(skb);
+
+	if (!mpext)
+		return SK_RST_REASON_NOT_SPECIFIED;
+
+	return sk_rst_convert_mptcp_reason(mpext->reset_reason);
+}
+
+static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
+					      struct sk_buff *skb,
+					      struct flowi *fl,
+					      struct request_sock *req,
+					      u32 tw_isn)
+{
+	struct dst_entry *dst;
+	int err;
+
+	tcp_rsk(req)->is_mptcp = 1;
+	subflow_init_req(req, sk);
+
+	dst = tcp_request_sock_ipv4_ops.route_req(sk, skb, fl, req, tw_isn);
+	if (!dst)
+		return NULL;
+
+	err = subflow_check_req(req, sk, skb);
+	if (err == 0)
+		return dst;
+
+	dst_release(dst);
+	if (!req->syncookie)
+		tcp_request_sock_ops.send_reset(sk, skb,
+						mptcp_get_rst_reason(skb));
+	return NULL;
+}
+
+static void subflow_prep_synack(const struct sock *sk, struct request_sock *req,
+				struct tcp_fastopen_cookie *foc,
+				enum tcp_synack_type synack_type)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct inet_request_sock *ireq = inet_rsk(req);
+
+	/* clear tstamp_ok, as needed depending on cookie */
+	if (foc && foc->len > -1)
+		ireq->tstamp_ok = 0;
+
+	if (synack_type == TCP_SYNACK_FASTOPEN)
+		mptcp_fastopen_subflow_synack_set_params(subflow, req);
+}
+
+static int subflow_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
+				  struct flowi *fl,
+				  struct request_sock *req,
+				  struct tcp_fastopen_cookie *foc,
+				  enum tcp_synack_type synack_type,
+				  struct sk_buff *syn_skb)
+{
+	subflow_prep_synack(sk, req, foc, synack_type);
+
+	return tcp_request_sock_ipv4_ops.send_synack(sk, dst, fl, req, foc,
+						     synack_type, syn_skb);
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static int subflow_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
+				  struct flowi *fl,
+				  struct request_sock *req,
+				  struct tcp_fastopen_cookie *foc,
+				  enum tcp_synack_type synack_type,
+				  struct sk_buff *syn_skb)
+{
+	subflow_prep_synack(sk, req, foc, synack_type);
+
+	return tcp_request_sock_ipv6_ops.send_synack(sk, dst, fl, req, foc,
+						     synack_type, syn_skb);
+}
+
+static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
+					      struct sk_buff *skb,
+					      struct flowi *fl,
+					      struct request_sock *req,
+					      u32 tw_isn)
+{
+	struct dst_entry *dst;
+	int err;
+
+	tcp_rsk(req)->is_mptcp = 1;
+	subflow_init_req(req, sk);
+
+	dst = tcp_request_sock_ipv6_ops.route_req(sk, skb, fl, req, tw_isn);
+	if (!dst)
+		return NULL;
+
+	err = subflow_check_req(req, sk, skb);
+	if (err == 0)
+		return dst;
+
+	dst_release(dst);
+	if (!req->syncookie)
+		tcp6_request_sock_ops.send_reset(sk, skb,
+						 mptcp_get_rst_reason(skb));
+	return NULL;
+}
+#endif
+
+/* validate received truncated hmac and create hmac for third ACK */
+static bool subflow_thmac_valid(struct mptcp_subflow_context *subflow)
+{
+	u8 hmac[SHA256_DIGEST_SIZE];
+	u64 thmac;
+
+	subflow_generate_hmac(subflow->remote_key, subflow->local_key,
+			      subflow->remote_nonce, subflow->local_nonce,
+			      hmac);
+
+	thmac = get_unaligned_be64(hmac);
+	pr_debug("subflow=%p, token=%u, thmac=%llu, subflow->thmac=%llu\n",
+		 subflow, subflow->token, thmac, subflow->thmac);
+
+	return thmac == subflow->thmac;
+}
+
+void mptcp_subflow_reset(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = subflow->conn;
+
+	/* mptcp_mp_fail_no_response() can reach here on an already closed
+	 * socket
+	 */
+	if (ssk->sk_state == TCP_CLOSE)
+		return;
+
+	/* must hold: tcp_done() could drop last reference on parent */
+	sock_hold(sk);
+
+	mptcp_send_active_reset_reason(ssk);
+	tcp_done(ssk);
+	if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags))
+		mptcp_schedule_work(sk);
+
+	sock_put(sk);
+}
+
+static bool subflow_use_different_dport(struct mptcp_sock *msk, const struct sock *sk)
+{
+	return inet_sk(sk)->inet_dport != inet_sk((struct sock *)msk)->inet_dport;
+}
+
+void __mptcp_sync_state(struct sock *sk, int state)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sock *ssk = msk->first;
+
+	subflow = mptcp_subflow_ctx(ssk);
+	__mptcp_propagate_sndbuf(sk, ssk);
+
+	if (sk->sk_state == TCP_SYN_SENT) {
+		/* subflow->idsn is always available is TCP_SYN_SENT state,
+		 * even for the FASTOPEN scenarios
+		 */
+		WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
+		WRITE_ONCE(msk->snd_nxt, msk->write_seq);
+		mptcp_set_state(sk, state);
+		sk->sk_state_change(sk);
+	}
+}
+
+static void subflow_set_remote_key(struct mptcp_sock *msk,
+				   struct mptcp_subflow_context *subflow,
+				   const struct mptcp_options_received *mp_opt)
+{
+	/* active MPC subflow will reach here multiple times:
+	 * at subflow_finish_connect() time and at 4th ack time
+	 */
+	if (subflow->remote_key_valid)
+		return;
+
+	subflow->remote_key_valid = 1;
+	subflow->remote_key = mp_opt->sndr_key;
+	mptcp_crypto_key_sha(subflow->remote_key, NULL, &subflow->iasn);
+	subflow->iasn++;
+
+	/* for fallback's sake */
+	subflow->map_seq = subflow->iasn;
+
+	WRITE_ONCE(msk->remote_key, subflow->remote_key);
+	WRITE_ONCE(msk->ack_seq, subflow->iasn);
+	WRITE_ONCE(msk->can_ack, true);
+	atomic64_set(&msk->rcv_wnd_sent, subflow->iasn);
+}
+
+static void mptcp_propagate_state(struct sock *sk, struct sock *ssk,
+				  struct mptcp_subflow_context *subflow,
+				  const struct mptcp_options_received *mp_opt)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	mptcp_data_lock(sk);
+	if (mp_opt) {
+		/* Options are available only in the non fallback cases
+		 * avoid updating rx path fields otherwise
+		 */
+		WRITE_ONCE(msk->snd_una, subflow->idsn + 1);
+		WRITE_ONCE(msk->wnd_end, subflow->idsn + 1 + tcp_sk(ssk)->snd_wnd);
+		subflow_set_remote_key(msk, subflow, mp_opt);
+	}
+
+	if (!sock_owned_by_user(sk)) {
+		__mptcp_sync_state(sk, ssk->sk_state);
+	} else {
+		msk->pending_state = ssk->sk_state;
+		__set_bit(MPTCP_SYNC_STATE, &msk->cb_flags);
+	}
+	mptcp_data_unlock(sk);
+}
+
+static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_options_received mp_opt;
+	struct sock *parent = subflow->conn;
+	struct mptcp_sock *msk;
+
+	subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
+
+	/* be sure no special action on any packet other than syn-ack */
+	if (subflow->conn_finished)
+		return;
+
+	msk = mptcp_sk(parent);
+	subflow->rel_write_seq = 1;
+	subflow->conn_finished = 1;
+	subflow->ssn_offset = TCP_SKB_CB(skb)->seq;
+	pr_debug("subflow=%p synack seq=%x\n", subflow, subflow->ssn_offset);
+
+	mptcp_get_options(skb, &mp_opt);
+	if (subflow->request_mptcp) {
+		if (!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYNACK)) {
+			if (!mptcp_try_fallback(sk,
+						MPTCP_MIB_MPCAPABLEACTIVEFALLBACK)) {
+				MPTCP_INC_STATS(sock_net(sk),
+						MPTCP_MIB_FALLBACKFAILED);
+				goto do_reset;
+			}
+
+			goto fallback;
+		}
+
+		if (mp_opt.suboptions & OPTION_MPTCP_CSUMREQD)
+			WRITE_ONCE(msk->csum_enabled, true);
+		if (mp_opt.deny_join_id0)
+			WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
+		subflow->mp_capable = 1;
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVEACK);
+		mptcp_finish_connect(sk);
+		mptcp_active_enable(parent);
+		mptcp_propagate_state(parent, sk, subflow, &mp_opt);
+	} else if (subflow->request_join) {
+		u8 hmac[SHA256_DIGEST_SIZE];
+
+		if (!(mp_opt.suboptions & OPTION_MPTCP_MPJ_SYNACK)) {
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPJOINSYNACKNOMPJOIN);
+			subflow->reset_reason = MPTCP_RST_EMPTCP;
+			goto do_reset;
+		}
+
+		subflow->backup = mp_opt.backup;
+		subflow->thmac = mp_opt.thmac;
+		subflow->remote_nonce = mp_opt.nonce;
+		WRITE_ONCE(subflow->remote_id, mp_opt.join_id);
+		pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u backup=%d\n",
+			 subflow, subflow->thmac, subflow->remote_nonce,
+			 subflow->backup);
+
+		if (!subflow_thmac_valid(subflow)) {
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKMAC);
+			subflow->reset_reason = MPTCP_RST_EMPTCP;
+			goto do_reset;
+		}
+
+		if (!mptcp_finish_join(sk))
+			goto do_reset;
+
+		subflow_generate_hmac(subflow->local_key, subflow->remote_key,
+				      subflow->local_nonce,
+				      subflow->remote_nonce,
+				      hmac);
+		memcpy(subflow->hmac, hmac, MPTCPOPT_HMAC_LEN);
+
+		subflow->mp_join = 1;
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
+
+		if (subflow->backup)
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKBACKUPRX);
+
+		if (subflow_use_different_dport(msk, sk)) {
+			pr_debug("synack inet_dport=%d %d\n",
+				 ntohs(inet_sk(sk)->inet_dport),
+				 ntohs(inet_sk(parent)->inet_dport));
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINPORTSYNACKRX);
+		}
+	} else if (mptcp_check_fallback(sk)) {
+		/* It looks like MPTCP is blocked, while TCP is not */
+		if (subflow->mpc_drop)
+			mptcp_active_disable(parent);
+fallback:
+		mptcp_propagate_state(parent, sk, subflow, NULL);
+	}
+	return;
+
+do_reset:
+	subflow->reset_transient = 0;
+	mptcp_subflow_reset(sk);
+}
+
+static void subflow_set_local_id(struct mptcp_subflow_context *subflow, int local_id)
+{
+	WARN_ON_ONCE(local_id < 0 || local_id > 255);
+	WRITE_ONCE(subflow->local_id, local_id);
+}
+
+static int subflow_chk_local_id(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	int err;
+
+	if (likely(subflow->local_id >= 0))
+		return 0;
+
+	err = mptcp_pm_get_local_id(msk, (struct sock_common *)sk);
+	if (err < 0)
+		return err;
+
+	subflow_set_local_id(subflow, err);
+	subflow->request_bkup = mptcp_pm_is_backup(msk, (struct sock_common *)sk);
+
+	return 0;
+}
+
+static int subflow_rebuild_header(struct sock *sk)
+{
+	int err = subflow_chk_local_id(sk);
+
+	if (unlikely(err < 0))
+		return err;
+
+	return inet_sk_rebuild_header(sk);
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static int subflow_v6_rebuild_header(struct sock *sk)
+{
+	int err = subflow_chk_local_id(sk);
+
+	if (unlikely(err < 0))
+		return err;
+
+	return inet6_sk_rebuild_header(sk);
+}
+#endif
+
+static struct request_sock_ops mptcp_subflow_v4_request_sock_ops __ro_after_init;
+static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;
+
+static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	pr_debug("subflow=%p\n", subflow);
+
+	/* Never answer to SYNs sent to broadcast or multicast */
+	if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
+		goto drop;
+
+	return tcp_conn_request(&mptcp_subflow_v4_request_sock_ops,
+				&subflow_request_sock_ipv4_ops,
+				sk, skb);
+drop:
+	tcp_listendrop(sk);
+	return 0;
+}
+
+static void subflow_v4_req_destructor(struct request_sock *req)
+{
+	subflow_req_destructor(req);
+	tcp_request_sock_ops.destructor(req);
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static struct request_sock_ops mptcp_subflow_v6_request_sock_ops __ro_after_init;
+static struct tcp_request_sock_ops subflow_request_sock_ipv6_ops __ro_after_init;
+static struct inet_connection_sock_af_ops subflow_v6_specific __ro_after_init;
+static struct inet_connection_sock_af_ops subflow_v6m_specific __ro_after_init;
+static struct proto tcpv6_prot_override __ro_after_init;
+
+static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	pr_debug("subflow=%p\n", subflow);
+
+	if (skb->protocol == htons(ETH_P_IP))
+		return subflow_v4_conn_request(sk, skb);
+
+	if (!ipv6_unicast_destination(skb))
+		goto drop;
+
+	if (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
+		__IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
+		return 0;
+	}
+
+	return tcp_conn_request(&mptcp_subflow_v6_request_sock_ops,
+				&subflow_request_sock_ipv6_ops, sk, skb);
+
+drop:
+	tcp_listendrop(sk);
+	return 0; /* don't send reset */
+}
+
+static void subflow_v6_req_destructor(struct request_sock *req)
+{
+	subflow_req_destructor(req);
+	tcp6_request_sock_ops.destructor(req);
+}
+#endif
+
+struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
+					       struct sock *sk_listener,
+					       bool attach_listener)
+{
+	if (ops->family == AF_INET)
+		ops = &mptcp_subflow_v4_request_sock_ops;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (ops->family == AF_INET6)
+		ops = &mptcp_subflow_v6_request_sock_ops;
+#endif
+
+	return inet_reqsk_alloc(ops, sk_listener, attach_listener);
+}
+EXPORT_SYMBOL(mptcp_subflow_reqsk_alloc);
+
+/* validate hmac received in third ACK */
+static bool subflow_hmac_valid(const struct mptcp_subflow_request_sock *subflow_req,
+			       const struct mptcp_options_received *mp_opt)
+{
+	struct mptcp_sock *msk = subflow_req->msk;
+	u8 hmac[SHA256_DIGEST_SIZE];
+
+	subflow_generate_hmac(READ_ONCE(msk->remote_key),
+			      READ_ONCE(msk->local_key),
+			      subflow_req->remote_nonce,
+			      subflow_req->local_nonce, hmac);
+
+	return !crypto_memneq(hmac, mp_opt->hmac, MPTCPOPT_HMAC_LEN);
+}
+
+static void subflow_ulp_fallback(struct sock *sk,
+				 struct mptcp_subflow_context *old_ctx)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	mptcp_subflow_tcp_fallback(sk, old_ctx);
+	icsk->icsk_ulp_ops = NULL;
+	rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
+	tcp_sk(sk)->is_mptcp = 0;
+
+	mptcp_subflow_ops_undo_override(sk);
+}
+
+void mptcp_subflow_drop_ctx(struct sock *ssk)
+{
+	struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
+
+	if (!ctx)
+		return;
+
+	list_del(&mptcp_subflow_ctx(ssk)->node);
+	if (inet_csk(ssk)->icsk_ulp_ops) {
+		subflow_ulp_fallback(ssk, ctx);
+		if (ctx->conn)
+			sock_put(ctx->conn);
+	}
+
+	kfree_rcu(ctx, rcu);
+}
+
+void __mptcp_subflow_fully_established(struct mptcp_sock *msk,
+				       struct mptcp_subflow_context *subflow,
+				       const struct mptcp_options_received *mp_opt)
+{
+	subflow_set_remote_key(msk, subflow, mp_opt);
+	WRITE_ONCE(subflow->fully_established, true);
+	WRITE_ONCE(msk->fully_established, true);
+}
+
+static struct sock *subflow_syn_recv_sock(const struct sock *sk,
+					  struct sk_buff *skb,
+					  struct request_sock *req,
+					  struct dst_entry *dst,
+					  struct request_sock *req_unhash,
+					  bool *own_req,
+					  void (*opt_child_init)(struct sock *newsk,
+								 const struct sock *sk))
+{
+	struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
+	struct mptcp_subflow_request_sock *subflow_req;
+	struct mptcp_options_received mp_opt;
+	bool fallback, fallback_is_fatal;
+	enum sk_rst_reason reason;
+	struct mptcp_sock *owner;
+	struct sock *child;
+
+	pr_debug("listener=%p, req=%p, conn=%p\n", listener, req, listener->conn);
+
+	/* After child creation we must look for MPC even when options
+	 * are not parsed
+	 */
+	mp_opt.suboptions = 0;
+
+	/* hopefully temporary handling for MP_JOIN+syncookie */
+	subflow_req = mptcp_subflow_rsk(req);
+	fallback_is_fatal = tcp_rsk(req)->is_mptcp && subflow_req->mp_join;
+	fallback = !tcp_rsk(req)->is_mptcp;
+	if (fallback)
+		goto create_child;
+
+	/* if the sk is MP_CAPABLE, we try to fetch the client key */
+	if (subflow_req->mp_capable) {
+		/* we can receive and accept an in-window, out-of-order pkt,
+		 * which may not carry the MP_CAPABLE opt even on mptcp enabled
+		 * paths: always try to extract the peer key, and fallback
+		 * for packets missing it.
+		 * Even OoO DSS packets coming legitly after dropped or
+		 * reordered MPC will cause fallback, but we don't have other
+		 * options.
+		 */
+		mptcp_get_options(skb, &mp_opt);
+		if (!(mp_opt.suboptions &
+		      (OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_ACK)))
+			fallback = true;
+
+	} else if (subflow_req->mp_join) {
+		mptcp_get_options(skb, &mp_opt);
+		if (!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK))
+			fallback = true;
+	}
+
+create_child:
+	child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
+						     req_unhash, own_req, opt_child_init);
+
+	if (child && *own_req) {
+		struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
+
+		tcp_rsk(req)->drop_req = false;
+
+		/* we need to fallback on ctx allocation failure and on pre-reqs
+		 * checking above. In the latter scenario we additionally need
+		 * to reset the context to non MPTCP status.
+		 */
+		if (!ctx || fallback) {
+			if (fallback_is_fatal) {
+				if (!ctx)
+					MPTCP_INC_STATS(sock_net(sk),
+							MPTCP_MIB_MPJOINACKNOCTX);
+				else
+					MPTCP_INC_STATS(sock_net(sk),
+							MPTCP_MIB_MPJOINACKNOMPJOIN);
+				subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
+				goto dispose_child;
+			}
+			goto fallback;
+		}
+
+		/* ssk inherits options of listener sk */
+		ctx->setsockopt_seq = listener->setsockopt_seq;
+
+		if (ctx->mp_capable) {
+			ctx->conn = mptcp_sk_clone_init(listener->conn, &mp_opt, child, req);
+			if (!ctx->conn)
+				goto fallback;
+
+			ctx->subflow_id = 1;
+			owner = mptcp_sk(ctx->conn);
+
+			if (mp_opt.deny_join_id0)
+				WRITE_ONCE(owner->pm.remote_deny_join_id0, true);
+
+			mptcp_pm_new_connection(owner, child, 1);
+
+			/* with OoO packets we can reach here without ingress
+			 * mpc option
+			 */
+			if (mp_opt.suboptions & OPTION_MPTCP_MPC_ACK) {
+				mptcp_pm_fully_established(owner, child);
+				ctx->pm_notified = 1;
+			}
+		} else if (ctx->mp_join) {
+			owner = subflow_req->msk;
+			if (!owner) {
+				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
+				goto dispose_child;
+			}
+
+			if (!subflow_hmac_valid(subflow_req, &mp_opt)) {
+				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);
+				subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
+				goto dispose_child;
+			}
+
+			if (!mptcp_can_accept_new_subflow(owner)) {
+				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINREJECTED);
+				subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
+				goto dispose_child;
+			}
+
+			/* move the msk reference ownership to the subflow */
+			subflow_req->msk = NULL;
+			ctx->conn = (struct sock *)owner;
+
+			if (subflow_use_different_sport(owner, sk)) {
+				pr_debug("ack inet_sport=%d %d\n",
+					 ntohs(inet_sk(sk)->inet_sport),
+					 ntohs(inet_sk((struct sock *)owner)->inet_sport));
+				if (!mptcp_pm_announced_has_ssk(owner, sk)) {
+					SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTACKRX);
+					subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
+					goto dispose_child;
+				}
+				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTACKRX);
+			}
+
+			if (!mptcp_finish_join(child)) {
+				struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(child);
+
+				subflow_add_reset_reason(skb, subflow->reset_reason);
+				goto dispose_child;
+			}
+
+			SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKRX);
+			tcp_rsk(req)->drop_req = true;
+		}
+	}
+
+	/* check for expected invariant - should never trigger, just help
+	 * catching earlier subtle bugs
+	 */
+	WARN_ON_ONCE(child && *own_req && tcp_sk(child)->is_mptcp &&
+		     (!mptcp_subflow_ctx(child) ||
+		      !mptcp_subflow_ctx(child)->conn));
+	return child;
+
+dispose_child:
+	mptcp_subflow_drop_ctx(child);
+	tcp_rsk(req)->drop_req = true;
+	inet_csk_prepare_for_destroy_sock(child);
+	tcp_done(child);
+	reason = mptcp_get_rst_reason(skb);
+	req->rsk_ops->send_reset(sk, skb, reason);
+
+	/* The last child reference will be released by the caller */
+	return child;
+
+fallback:
+	if (fallback)
+		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
+	mptcp_subflow_drop_ctx(child);
+	return child;
+}
+
+static struct inet_connection_sock_af_ops subflow_specific __ro_after_init;
+static struct proto tcp_prot_override __ro_after_init;
+
+enum mapping_status {
+	MAPPING_OK,
+	MAPPING_INVALID,
+	MAPPING_EMPTY,
+	MAPPING_DATA_FIN,
+	MAPPING_DUMMY,
+	MAPPING_BAD_CSUM,
+	MAPPING_NODSS
+};
+
+static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
+{
+	pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d\n",
+		 ssn, subflow->map_subflow_seq, subflow->map_data_len);
+}
+
+static bool skb_is_fully_mapped(struct sock *ssk, struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	unsigned int skb_consumed;
+
+	skb_consumed = tcp_sk(ssk)->copied_seq - TCP_SKB_CB(skb)->seq;
+	if (unlikely(skb_consumed >= skb->len)) {
+		DEBUG_NET_WARN_ON_ONCE(1);
+		return true;
+	}
+
+	return skb->len - skb_consumed <= subflow->map_data_len -
+					  mptcp_subflow_get_map_offset(subflow);
+}
+
+static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	u32 ssn = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
+
+	if (unlikely(before(ssn, subflow->map_subflow_seq))) {
+		/* Mapping covers data later in the subflow stream,
+		 * currently unsupported.
+		 */
+		dbg_bad_map(subflow, ssn);
+		return false;
+	}
+	if (unlikely(!before(ssn, subflow->map_subflow_seq +
+				  subflow->map_data_len))) {
+		/* Mapping does covers past subflow data, invalid */
+		dbg_bad_map(subflow, ssn);
+		return false;
+	}
+	return true;
+}
+
+static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *skb,
+					      bool csum_reqd)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	u32 offset, seq, delta;
+	__sum16 csum;
+	int len;
+
+	if (!csum_reqd)
+		return MAPPING_OK;
+
+	/* mapping already validated on previous traversal */
+	if (subflow->map_csum_len == subflow->map_data_len)
+		return MAPPING_OK;
+
+	/* traverse the receive queue, ensuring it contains a full
+	 * DSS mapping and accumulating the related csum.
+	 * Preserve the accoumlate csum across multiple calls, to compute
+	 * the csum only once
+	 */
+	delta = subflow->map_data_len - subflow->map_csum_len;
+	for (;;) {
+		seq = tcp_sk(ssk)->copied_seq + subflow->map_csum_len;
+		offset = seq - TCP_SKB_CB(skb)->seq;
+
+		/* if the current skb has not been accounted yet, csum its contents
+		 * up to the amount covered by the current DSS
+		 */
+		if (offset < skb->len) {
+			__wsum csum;
+
+			len = min(skb->len - offset, delta);
+			csum = skb_checksum(skb, offset, len, 0);
+			subflow->map_data_csum = csum_block_add(subflow->map_data_csum, csum,
+								subflow->map_csum_len);
+
+			delta -= len;
+			subflow->map_csum_len += len;
+		}
+		if (delta == 0)
+			break;
+
+		if (skb_queue_is_last(&ssk->sk_receive_queue, skb)) {
+			/* if this subflow is closed, the partial mapping
+			 * will be never completed; flush the pending skbs, so
+			 * that subflow_sched_work_if_closed() can kick in
+			 */
+			if (unlikely(ssk->sk_state == TCP_CLOSE))
+				while ((skb = skb_peek(&ssk->sk_receive_queue)))
+					sk_eat_skb(ssk, skb);
+
+			/* not enough data to validate the csum */
+			return MAPPING_EMPTY;
+		}
+
+		/* the DSS mapping for next skbs will be validated later,
+		 * when a get_mapping_status call will process such skb
+		 */
+		skb = skb->next;
+	}
+
+	/* note that 'map_data_len' accounts only for the carried data, does
+	 * not include the eventual seq increment due to the data fin,
+	 * while the pseudo header requires the original DSS data len,
+	 * including that
+	 */
+	csum = __mptcp_make_csum(subflow->map_seq,
+				 subflow->map_subflow_seq,
+				 subflow->map_data_len + subflow->map_data_fin,
+				 subflow->map_data_csum);
+	if (unlikely(csum)) {
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
+		return MAPPING_BAD_CSUM;
+	}
+
+	subflow->valid_csum_seen = 1;
+	return MAPPING_OK;
+}
+
+static enum mapping_status get_mapping_status(struct sock *ssk,
+					      struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	bool csum_reqd = READ_ONCE(msk->csum_enabled);
+	struct mptcp_ext *mpext;
+	struct sk_buff *skb;
+	u16 data_len;
+	u64 map_seq;
+
+	skb = skb_peek(&ssk->sk_receive_queue);
+	if (!skb)
+		return MAPPING_EMPTY;
+
+	if (mptcp_check_fallback(ssk))
+		return MAPPING_DUMMY;
+
+	mpext = mptcp_get_ext(skb);
+	if (!mpext || !mpext->use_map) {
+		if (!subflow->map_valid && !skb->len) {
+			/* the TCP stack deliver 0 len FIN pkt to the receive
+			 * queue, that is the only 0len pkts ever expected here,
+			 * and we can admit no mapping only for 0 len pkts
+			 */
+			if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
+				WARN_ONCE(1, "0len seq %d:%d flags %x",
+					  TCP_SKB_CB(skb)->seq,
+					  TCP_SKB_CB(skb)->end_seq,
+					  TCP_SKB_CB(skb)->tcp_flags);
+			sk_eat_skb(ssk, skb);
+			return MAPPING_EMPTY;
+		}
+
+		/* If the required DSS has likely been dropped by a middlebox */
+		if (!subflow->map_valid)
+			return MAPPING_NODSS;
+
+		goto validate_seq;
+	}
+
+	trace_get_mapping_status(mpext);
+
+	data_len = mpext->data_len;
+	if (data_len == 0) {
+		pr_debug("infinite mapping received\n");
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
+		return MAPPING_INVALID;
+	}
+
+	if (mpext->data_fin == 1) {
+		u64 data_fin_seq;
+
+		if (data_len == 1) {
+			bool updated = mptcp_update_rcv_data_fin(msk, mpext->data_seq,
+								 mpext->dsn64);
+			pr_debug("DATA_FIN with no payload seq=%llu\n", mpext->data_seq);
+			if (subflow->map_valid) {
+				/* A DATA_FIN might arrive in a DSS
+				 * option before the previous mapping
+				 * has been fully consumed. Continue
+				 * handling the existing mapping.
+				 */
+				skb_ext_del(skb, SKB_EXT_MPTCP);
+				return MAPPING_OK;
+			}
+
+			if (updated)
+				mptcp_schedule_work((struct sock *)msk);
+
+			return MAPPING_DATA_FIN;
+		}
+
+		data_fin_seq = mpext->data_seq + data_len - 1;
+
+		/* If mpext->data_seq is a 32-bit value, data_fin_seq must also
+		 * be limited to 32 bits.
+		 */
+		if (!mpext->dsn64)
+			data_fin_seq &= GENMASK_ULL(31, 0);
+
+		mptcp_update_rcv_data_fin(msk, data_fin_seq, mpext->dsn64);
+		pr_debug("DATA_FIN with mapping seq=%llu dsn64=%d\n",
+			 data_fin_seq, mpext->dsn64);
+
+		/* Adjust for DATA_FIN using 1 byte of sequence space */
+		data_len--;
+	}
+
+	map_seq = mptcp_expand_seq(READ_ONCE(msk->ack_seq), mpext->data_seq, mpext->dsn64);
+	WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
+
+	if (subflow->map_valid) {
+		/* Allow replacing only with an identical map */
+		if (subflow->map_seq == map_seq &&
+		    subflow->map_subflow_seq == mpext->subflow_seq &&
+		    subflow->map_data_len == data_len &&
+		    subflow->map_csum_reqd == mpext->csum_reqd) {
+			skb_ext_del(skb, SKB_EXT_MPTCP);
+			goto validate_csum;
+		}
+
+		/* If this skb data are fully covered by the current mapping,
+		 * the new map would need caching, which is not supported
+		 */
+		if (skb_is_fully_mapped(ssk, skb)) {
+			MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSNOMATCH);
+			return MAPPING_INVALID;
+		}
+
+		/* will validate the next map after consuming the current one */
+		goto validate_csum;
+	}
+
+	subflow->map_seq = map_seq;
+	subflow->map_subflow_seq = mpext->subflow_seq;
+	subflow->map_data_len = data_len;
+	subflow->map_valid = 1;
+	subflow->map_data_fin = mpext->data_fin;
+	subflow->mpc_map = mpext->mpc_map;
+	subflow->map_csum_reqd = mpext->csum_reqd;
+	subflow->map_csum_len = 0;
+	subflow->map_data_csum = csum_unfold(mpext->csum);
+
+	/* Cfr RFC 8684 Section 3.3.0 */
+	if (unlikely(subflow->map_csum_reqd != csum_reqd))
+		return MAPPING_INVALID;
+
+	pr_debug("new map seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n",
+		 subflow->map_seq, subflow->map_subflow_seq,
+		 subflow->map_data_len, subflow->map_csum_reqd,
+		 subflow->map_data_csum);
+
+validate_seq:
+	/* we revalidate valid mapping on new skb, because we must ensure
+	 * the current skb is completely covered by the available mapping
+	 */
+	if (!validate_mapping(ssk, skb)) {
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSTCPMISMATCH);
+		return MAPPING_INVALID;
+	}
+
+	skb_ext_del(skb, SKB_EXT_MPTCP);
+
+validate_csum:
+	return validate_data_csum(ssk, skb, csum_reqd);
+}
+
+static void mptcp_subflow_discard_data(struct sock *ssk, struct sk_buff *skb,
+				       u64 limit)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	bool fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
+	struct tcp_sock *tp = tcp_sk(ssk);
+	u32 offset, incr, avail_len;
+
+	offset = tp->copied_seq - TCP_SKB_CB(skb)->seq;
+	if (WARN_ON_ONCE(offset > skb->len))
+		goto out;
+
+	avail_len = skb->len - offset;
+	incr = limit >= avail_len ? avail_len + fin : limit;
+
+	pr_debug("discarding=%d len=%d offset=%d seq=%d\n", incr, skb->len,
+		 offset, subflow->map_subflow_seq);
+	MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DUPDATA);
+	tcp_sk(ssk)->copied_seq += incr;
+
+out:
+	if (!before(tcp_sk(ssk)->copied_seq, TCP_SKB_CB(skb)->end_seq))
+		sk_eat_skb(ssk, skb);
+	if (mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len)
+		subflow->map_valid = 0;
+}
+
+static bool subflow_is_done(const struct sock *sk)
+{
+	return sk->sk_shutdown & RCV_SHUTDOWN || sk->sk_state == TCP_CLOSE;
+}
+
+/* sched mptcp worker for subflow cleanup if no more data is pending */
+static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ssk)
+{
+	const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct sock *sk = (struct sock *)msk;
+
+	if (likely(ssk->sk_state != TCP_CLOSE &&
+		   (ssk->sk_state != TCP_CLOSE_WAIT ||
+		    inet_sk_state_load(sk) != TCP_ESTABLISHED)))
+		return;
+
+	if (!skb_queue_empty(&ssk->sk_receive_queue))
+		return;
+
+	if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
+		mptcp_schedule_work(sk);
+
+	/* when the fallback subflow closes the rx side, trigger a 'dummy'
+	 * ingress data fin, so that the msk state will follow along
+	 */
+	if (__mptcp_check_fallback(msk) && subflow_is_done(ssk) &&
+	    msk->first == ssk &&
+	    mptcp_update_rcv_data_fin(msk, subflow->map_seq +
+				      subflow->map_data_len, true))
+		mptcp_schedule_work(sk);
+}
+
+static bool mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	unsigned long fail_tout;
+
+	/* we are really failing, prevent any later subflow join */
+	spin_lock_bh(&msk->fallback_lock);
+	if (!msk->allow_infinite_fallback) {
+		spin_unlock_bh(&msk->fallback_lock);
+		return false;
+	}
+	msk->allow_subflows = false;
+	spin_unlock_bh(&msk->fallback_lock);
+
+	/* graceful failure can happen only on the MPC subflow */
+	if (WARN_ON_ONCE(ssk != READ_ONCE(msk->first)))
+		return false;
+
+	/* since the close timeout take precedence on the fail one,
+	 * no need to start the latter when the first is already set
+	 */
+	if (sock_flag((struct sock *)msk, SOCK_DEAD))
+		return true;
+
+	/* we don't need extreme accuracy here, use a zero fail_tout as special
+	 * value meaning no fail timeout at all;
+	 */
+	fail_tout = jiffies + TCP_RTO_MAX;
+	if (!fail_tout)
+		fail_tout = 1;
+	WRITE_ONCE(subflow->fail_tout, fail_tout);
+	tcp_send_ack(ssk);
+
+	mptcp_reset_tout_timer(msk, subflow->fail_tout);
+	return true;
+}
+
+static bool subflow_check_data_avail(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	enum mapping_status status;
+	struct mptcp_sock *msk;
+	struct sk_buff *skb;
+
+	if (!skb_peek(&ssk->sk_receive_queue))
+		WRITE_ONCE(subflow->data_avail, false);
+	if (subflow->data_avail)
+		return true;
+
+	msk = mptcp_sk(subflow->conn);
+	for (;;) {
+		u64 ack_seq;
+		u64 old_ack;
+
+		status = get_mapping_status(ssk, msk);
+		trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
+		if (unlikely(status == MAPPING_INVALID || status == MAPPING_DUMMY ||
+			     status == MAPPING_BAD_CSUM || status == MAPPING_NODSS))
+			goto fallback;
+
+		if (status != MAPPING_OK)
+			goto no_data;
+
+		skb = skb_peek(&ssk->sk_receive_queue);
+		if (WARN_ON_ONCE(!skb))
+			goto no_data;
+
+		if (unlikely(!READ_ONCE(msk->can_ack)))
+			goto fallback;
+
+		old_ack = READ_ONCE(msk->ack_seq);
+		ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
+		pr_debug("msk ack_seq=%llx subflow ack_seq=%llx\n", old_ack,
+			 ack_seq);
+		if (unlikely(before64(ack_seq, old_ack))) {
+			mptcp_subflow_discard_data(ssk, skb, old_ack - ack_seq);
+			continue;
+		}
+
+		WRITE_ONCE(subflow->data_avail, true);
+		break;
+	}
+	return true;
+
+no_data:
+	subflow_sched_work_if_closed(msk, ssk);
+	return false;
+
+fallback:
+	if (!__mptcp_check_fallback(msk)) {
+		/* RFC 8684 section 3.7. */
+		if (status == MAPPING_BAD_CSUM &&
+		    (subflow->mp_join || subflow->valid_csum_seen)) {
+			subflow->send_mp_fail = 1;
+
+			if (!mptcp_subflow_fail(msk, ssk)) {
+				subflow->reset_transient = 0;
+				subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
+				goto reset;
+			}
+			WRITE_ONCE(subflow->data_avail, true);
+			return true;
+		}
+
+		if (!mptcp_try_fallback(ssk, MPTCP_MIB_DSSFALLBACK)) {
+			/* fatal protocol error, close the socket.
+			 * subflow_error_report() will introduce the appropriate barriers
+			 */
+			subflow->reset_transient = 0;
+			MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSRESET);
+			subflow->reset_reason = status == MAPPING_NODSS ?
+						MPTCP_RST_EMIDDLEBOX :
+						MPTCP_RST_EMPTCP;
+
+reset:
+			WRITE_ONCE(ssk->sk_err, EBADMSG);
+			tcp_set_state(ssk, TCP_CLOSE);
+			while ((skb = skb_peek(&ssk->sk_receive_queue)))
+				sk_eat_skb(ssk, skb);
+			mptcp_send_active_reset_reason(ssk);
+			WRITE_ONCE(subflow->data_avail, false);
+			return false;
+		}
+	}
+
+	skb = skb_peek(&ssk->sk_receive_queue);
+	subflow->map_valid = 1;
+	subflow->map_data_len = skb->len;
+	subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
+	subflow->map_seq = __mptcp_expand_seq(subflow->map_seq,
+					      subflow->iasn +
+					      TCP_SKB_CB(skb)->seq -
+					      subflow->ssn_offset - 1);
+	WRITE_ONCE(subflow->data_avail, true);
+	return true;
+}
+
+bool mptcp_subflow_data_available(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	/* check if current mapping is still valid */
+	if (subflow->map_valid &&
+	    mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len) {
+		subflow->map_valid = 0;
+		WRITE_ONCE(subflow->data_avail, false);
+
+		pr_debug("Done with mapping: seq=%u data_len=%u\n",
+			 subflow->map_subflow_seq,
+			 subflow->map_data_len);
+	}
+
+	return subflow_check_data_avail(sk);
+}
+
+/* If ssk has an mptcp parent socket, use the mptcp rcvbuf occupancy,
+ * not the ssk one.
+ *
+ * In mptcp, rwin is about the mptcp-level connection data.
+ *
+ * Data that is still on the ssk rx queue can thus be ignored,
+ * as far as mptcp peer is concerned that data is still inflight.
+ * DSS ACK is updated when skb is moved to the mptcp rx queue.
+ */
+void mptcp_space(const struct sock *ssk, int *space, int *full_space)
+{
+	const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	const struct sock *sk = subflow->conn;
+
+	*space = __mptcp_space(sk);
+	*full_space = mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf));
+}
+
+static void subflow_error_report(struct sock *ssk)
+{
+	struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
+
+	/* bail early if this is a no-op, so that we avoid introducing a
+	 * problematic lockdep dependency between TCP accept queue lock
+	 * and msk socket spinlock
+	 */
+	if (!sk->sk_socket)
+		return;
+
+	mptcp_data_lock(sk);
+	if (!sock_owned_by_user(sk))
+		__mptcp_error_report(sk);
+	else
+		__set_bit(MPTCP_ERROR_REPORT,  &mptcp_sk(sk)->cb_flags);
+	mptcp_data_unlock(sk);
+}
+
+static void subflow_data_ready(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	u16 state = 1 << inet_sk_state_load(sk);
+	struct sock *parent = subflow->conn;
+	struct mptcp_sock *msk;
+
+	trace_sk_data_ready(sk);
+
+	msk = mptcp_sk(parent);
+	if (state & TCPF_LISTEN) {
+		/* MPJ subflow are removed from accept queue before reaching here,
+		 * avoid stray wakeups
+		 */
+		if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
+			return;
+
+		parent->sk_data_ready(parent);
+		return;
+	}
+
+	WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
+		     !subflow->mp_join && !(state & TCPF_CLOSE));
+
+	if (mptcp_subflow_data_available(sk)) {
+		mptcp_data_ready(parent, sk);
+
+		/* subflow-level lowat test are not relevant.
+		 * respect the msk-level threshold eventually mandating an immediate ack
+		 */
+		if (mptcp_data_avail(msk) < parent->sk_rcvlowat &&
+		    (tcp_sk(sk)->rcv_nxt - tcp_sk(sk)->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss)
+			inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
+	} else if (unlikely(sk->sk_err)) {
+		subflow_error_report(sk);
+	}
+}
+
+static void subflow_write_space(struct sock *ssk)
+{
+	struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
+
+	mptcp_propagate_sndbuf(sk, ssk);
+	mptcp_write_space(sk);
+}
+
+static const struct inet_connection_sock_af_ops *
+subflow_default_af_ops(struct sock *sk)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (sk->sk_family == AF_INET6)
+		return &subflow_v6_specific;
+#endif
+	return &subflow_specific;
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+void mptcpv6_handle_mapped(struct sock *sk, bool mapped)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	const struct inet_connection_sock_af_ops *target;
+
+	target = mapped ? &subflow_v6m_specific : subflow_default_af_ops(sk);
+
+	pr_debug("subflow=%p family=%d ops=%p target=%p mapped=%d\n",
+		 subflow, sk->sk_family, icsk->icsk_af_ops, target, mapped);
+
+	if (likely(icsk->icsk_af_ops == target))
+		return;
+
+	subflow->icsk_af_ops = icsk->icsk_af_ops;
+	icsk->icsk_af_ops = target;
+}
+#endif
+
+void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
+			 struct sockaddr_storage *addr,
+			 unsigned short family)
+{
+	memset(addr, 0, sizeof(*addr));
+	addr->ss_family = family;
+	if (addr->ss_family == AF_INET) {
+		struct sockaddr_in *in_addr = (struct sockaddr_in *)addr;
+
+		if (info->family == AF_INET)
+			in_addr->sin_addr = info->addr;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+		else if (ipv6_addr_v4mapped(&info->addr6))
+			in_addr->sin_addr.s_addr = info->addr6.s6_addr32[3];
+#endif
+		in_addr->sin_port = info->port;
+	}
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (addr->ss_family == AF_INET6) {
+		struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)addr;
+
+		if (info->family == AF_INET)
+			ipv6_addr_set_v4mapped(info->addr.s_addr,
+					       &in6_addr->sin6_addr);
+		else
+			in6_addr->sin6_addr = info->addr6;
+		in6_addr->sin6_port = info->port;
+	}
+#endif
+}
+
+int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_pm_local *local,
+			    const struct mptcp_addr_info *remote)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_subflow_context *subflow;
+	int local_id = local->addr.id;
+	struct sockaddr_storage addr;
+	int remote_id = remote->id;
+	int err = -ENOTCONN;
+	struct socket *sf;
+	struct sock *ssk;
+	u32 remote_token;
+	int addrlen;
+
+	/* The userspace PM sent the request too early? */
+	if (!mptcp_is_fully_established(sk))
+		goto err_out;
+
+	err = mptcp_subflow_create_socket(sk, local->addr.family, &sf);
+	if (err) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXCREATSKERR);
+		pr_debug("msk=%p local=%d remote=%d create sock error: %d\n",
+			 msk, local_id, remote_id, err);
+		goto err_out;
+	}
+
+	ssk = sf->sk;
+	subflow = mptcp_subflow_ctx(ssk);
+	do {
+		subflow->local_nonce = get_random_u32();
+	} while (!subflow->local_nonce);
+
+	/* if 'IPADDRANY', the ID will be set later, after the routing */
+	if (local->addr.family == AF_INET) {
+		if (!local->addr.addr.s_addr)
+			local_id = -1;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	} else if (sk->sk_family == AF_INET6) {
+		if (ipv6_addr_any(&local->addr.addr6))
+			local_id = -1;
+#endif
+	}
+
+	if (local_id >= 0)
+		subflow_set_local_id(subflow, local_id);
+
+	subflow->remote_key_valid = 1;
+	subflow->remote_key = READ_ONCE(msk->remote_key);
+	subflow->local_key = READ_ONCE(msk->local_key);
+	subflow->token = msk->token;
+	mptcp_info2sockaddr(&local->addr, &addr, ssk->sk_family);
+
+	addrlen = sizeof(struct sockaddr_in);
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (addr.ss_family == AF_INET6)
+		addrlen = sizeof(struct sockaddr_in6);
+#endif
+	ssk->sk_bound_dev_if = local->ifindex;
+	err = kernel_bind(sf, (struct sockaddr_unsized *)&addr, addrlen);
+	if (err) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXBINDERR);
+		pr_debug("msk=%p local=%d remote=%d bind error: %d\n",
+			 msk, local_id, remote_id, err);
+		goto failed;
+	}
+
+	mptcp_crypto_key_sha(subflow->remote_key, &remote_token, NULL);
+	pr_debug("msk=%p remote_token=%u local_id=%d remote_id=%d\n", msk,
+		 remote_token, local_id, remote_id);
+	subflow->remote_token = remote_token;
+	WRITE_ONCE(subflow->remote_id, remote_id);
+	subflow->request_join = 1;
+	subflow->request_bkup = !!(local->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
+	subflow->subflow_id = msk->subflow_id++;
+	mptcp_info2sockaddr(remote, &addr, ssk->sk_family);
+
+	sock_hold(ssk);
+	list_add_tail(&subflow->node, &msk->conn_list);
+	err = kernel_connect(sf, (struct sockaddr_unsized *)&addr, addrlen, O_NONBLOCK);
+	if (err && err != -EINPROGRESS) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXCONNECTERR);
+		pr_debug("msk=%p local=%d remote=%d connect error: %d\n",
+			 msk, local_id, remote_id, err);
+		goto failed_unlink;
+	}
+
+	MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTX);
+
+	/* discard the subflow socket */
+	mptcp_sock_graft(ssk, sk->sk_socket);
+	iput(SOCK_INODE(sf));
+	mptcp_stop_tout_timer(sk);
+	return 0;
+
+failed_unlink:
+	list_del(&subflow->node);
+	sock_put(mptcp_subflow_tcp_sock(subflow));
+
+failed:
+	subflow->disposable = 1;
+	sock_release(sf);
+
+err_out:
+	/* we account subflows before the creation, and this failures will not
+	 * be caught by sk_state_change()
+	 */
+	mptcp_pm_close_subflow(msk);
+	return err;
+}
+
+void __mptcp_inherit_memcg(struct sock *sk, struct sock *ssk, gfp_t gfp)
+{
+	/* Only if the msk has been accepted already (and not orphaned).*/
+	if (!mem_cgroup_sockets_enabled || !sk->sk_socket)
+		return;
+
+	mem_cgroup_sk_inherit(sk, ssk);
+	__sk_charge(ssk, gfp);
+}
+
+void __mptcp_inherit_cgrp_data(struct sock *sk, struct sock *ssk)
+{
+#ifdef CONFIG_SOCK_CGROUP_DATA
+	struct sock_cgroup_data *sk_cd = &sk->sk_cgrp_data,
+				*ssk_cd = &ssk->sk_cgrp_data;
+
+	/* only the additional subflows created by kworkers have to be modified */
+	if (cgroup_id(sock_cgroup_ptr(sk_cd)) !=
+	    cgroup_id(sock_cgroup_ptr(ssk_cd))) {
+		cgroup_sk_free(ssk_cd);
+		*ssk_cd = *sk_cd;
+		cgroup_sk_clone(sk_cd);
+	}
+#endif /* CONFIG_SOCK_CGROUP_DATA */
+}
+
+static void mptcp_attach_cgroup(struct sock *parent, struct sock *child)
+{
+	__mptcp_inherit_cgrp_data(parent, child);
+	if (mem_cgroup_sockets_enabled)
+		mem_cgroup_sk_inherit(parent, child);
+}
+
+static void mptcp_subflow_ops_override(struct sock *ssk)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (ssk->sk_prot == &tcpv6_prot)
+		ssk->sk_prot = &tcpv6_prot_override;
+	else
+#endif
+		ssk->sk_prot = &tcp_prot_override;
+}
+
+static void mptcp_subflow_ops_undo_override(struct sock *ssk)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (ssk->sk_prot == &tcpv6_prot_override)
+		ssk->sk_prot = &tcpv6_prot;
+	else
+#endif
+		ssk->sk_prot = &tcp_prot;
+}
+
+int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
+				struct socket **new_sock)
+{
+	struct mptcp_subflow_context *subflow;
+	struct net *net = sock_net(sk);
+	struct socket *sf;
+	int err;
+
+	/* un-accepted server sockets can reach here - on bad configuration
+	 * bail early to avoid greater trouble later
+	 */
+	if (unlikely(!sk->sk_socket))
+		return -EINVAL;
+
+	err = sock_create_kern(net, family, SOCK_STREAM, IPPROTO_TCP, &sf);
+	if (err)
+		return err;
+
+	lock_sock_nested(sf->sk, SINGLE_DEPTH_NESTING);
+
+	err = security_mptcp_add_subflow(sk, sf->sk);
+	if (err)
+		goto err_free;
+
+	/* the newly created socket has to be in the same cgroup as its parent */
+	mptcp_attach_cgroup(sk, sf->sk);
+
+	/* kernel sockets do not by default acquire net ref, but TCP timer
+	 * needs it.
+	 * Update ns_tracker to current stack trace and refcounted tracker.
+	 */
+	sk_net_refcnt_upgrade(sf->sk);
+	err = tcp_set_ulp(sf->sk, "mptcp");
+	if (err)
+		goto err_free;
+
+	mptcp_sockopt_sync_locked(mptcp_sk(sk), sf->sk);
+	release_sock(sf->sk);
+
+	/* the newly created socket really belongs to the owning MPTCP
+	 * socket, even if for additional subflows the allocation is performed
+	 * by a kernel workqueue. Adjust inode references, so that the
+	 * procfs/diag interfaces really show this one belonging to the correct
+	 * user.
+	 */
+	SOCK_INODE(sf)->i_ino = SOCK_INODE(sk->sk_socket)->i_ino;
+	SOCK_INODE(sf)->i_uid = SOCK_INODE(sk->sk_socket)->i_uid;
+	SOCK_INODE(sf)->i_gid = SOCK_INODE(sk->sk_socket)->i_gid;
+
+	subflow = mptcp_subflow_ctx(sf->sk);
+	pr_debug("subflow=%p\n", subflow);
+
+	*new_sock = sf;
+	sock_hold(sk);
+	subflow->conn = sk;
+	mptcp_subflow_ops_override(sf->sk);
+
+	return 0;
+
+err_free:
+	release_sock(sf->sk);
+	sock_release(sf);
+	return err;
+}
+
+static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,
+							gfp_t priority)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct mptcp_subflow_context *ctx;
+
+	ctx = kzalloc_obj(*ctx, priority);
+	if (!ctx)
+		return NULL;
+
+	rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
+	INIT_LIST_HEAD(&ctx->node);
+	INIT_LIST_HEAD(&ctx->delegated_node);
+
+	pr_debug("subflow=%p\n", ctx);
+
+	ctx->tcp_sock = sk;
+	WRITE_ONCE(ctx->local_id, -1);
+
+	return ctx;
+}
+
+static void __subflow_state_change(struct sock *sk)
+{
+	struct socket_wq *wq;
+
+	rcu_read_lock();
+	wq = rcu_dereference(sk->sk_wq);
+	if (skwq_has_sleeper(wq))
+		wake_up_interruptible_all(&wq->wait);
+	rcu_read_unlock();
+}
+
+static void subflow_state_change(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct sock *parent = subflow->conn;
+
+	__subflow_state_change(sk);
+
+	/* as recvmsg() does not acquire the subflow socket for ssk selection
+	 * a fin packet carrying a DSS can be unnoticed if we don't trigger
+	 * the data available machinery here.
+	 */
+	if (mptcp_subflow_data_available(sk))
+		mptcp_data_ready(parent, sk);
+	else if (unlikely(sk->sk_err))
+		subflow_error_report(sk);
+
+	subflow_sched_work_if_closed(mptcp_sk(parent), sk);
+}
+
+void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_ssk)
+{
+	struct request_sock_queue *queue = &inet_csk(listener_ssk)->icsk_accept_queue;
+	struct request_sock *req, *head, *tail;
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk, *ssk;
+
+	/* Due to lock dependencies no relevant lock can be acquired under rskq_lock.
+	 * Splice the req list, so that accept() can not reach the pending ssk after
+	 * the listener socket is released below.
+	 */
+	spin_lock_bh(&queue->rskq_lock);
+	head = queue->rskq_accept_head;
+	tail = queue->rskq_accept_tail;
+	queue->rskq_accept_head = NULL;
+	queue->rskq_accept_tail = NULL;
+	spin_unlock_bh(&queue->rskq_lock);
+
+	if (!head)
+		return;
+
+	/* can't acquire the msk socket lock under the subflow one,
+	 * or will cause ABBA deadlock
+	 */
+	release_sock(listener_ssk);
+
+	for (req = head; req; req = req->dl_next) {
+		ssk = req->sk;
+		if (!sk_is_mptcp(ssk))
+			continue;
+
+		subflow = mptcp_subflow_ctx(ssk);
+		if (!subflow || !subflow->conn)
+			continue;
+
+		sk = subflow->conn;
+		sock_hold(sk);
+
+		lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
+		__mptcp_unaccepted_force_close(sk);
+		release_sock(sk);
+
+		/* lockdep will report a false positive ABBA deadlock
+		 * between cancel_work_sync and the listener socket.
+		 * The involved locks belong to different sockets WRT
+		 * the existing AB chain.
+		 * Using a per socket key is problematic as key
+		 * deregistration requires process context and must be
+		 * performed at socket disposal time, in atomic
+		 * context.
+		 * Just tell lockdep to consider the listener socket
+		 * released here.
+		 */
+		mutex_release(&listener_sk->sk_lock.dep_map, _RET_IP_);
+		mptcp_cancel_work(sk);
+		mutex_acquire(&listener_sk->sk_lock.dep_map, 0, 0, _RET_IP_);
+
+		sock_put(sk);
+	}
+
+	/* we are still under the listener msk socket lock */
+	lock_sock_nested(listener_ssk, SINGLE_DEPTH_NESTING);
+
+	/* restore the listener queue, to let the TCP code clean it up */
+	spin_lock_bh(&queue->rskq_lock);
+	WARN_ON_ONCE(queue->rskq_accept_head);
+	queue->rskq_accept_head = head;
+	queue->rskq_accept_tail = tail;
+	spin_unlock_bh(&queue->rskq_lock);
+}
+
+static int subflow_ulp_init(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct mptcp_subflow_context *ctx;
+	struct tcp_sock *tp = tcp_sk(sk);
+	int err = 0;
+
+	/* disallow attaching ULP to a socket unless it has been
+	 * created with sock_create_kern()
+	 */
+	if (!sk->sk_kern_sock) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+
+	ctx = subflow_create_ctx(sk, GFP_KERNEL);
+	if (!ctx) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	pr_debug("subflow=%p, family=%d\n", ctx, sk->sk_family);
+
+	tp->is_mptcp = 1;
+	ctx->icsk_af_ops = icsk->icsk_af_ops;
+	icsk->icsk_af_ops = subflow_default_af_ops(sk);
+	ctx->tcp_state_change = sk->sk_state_change;
+	ctx->tcp_error_report = sk->sk_error_report;
+
+	WARN_ON_ONCE(sk->sk_data_ready != sock_def_readable);
+	WARN_ON_ONCE(sk->sk_write_space != sk_stream_write_space);
+
+	sk->sk_data_ready = subflow_data_ready;
+	sk->sk_write_space = subflow_write_space;
+	sk->sk_state_change = subflow_state_change;
+	sk->sk_error_report = subflow_error_report;
+out:
+	return err;
+}
+
+static void subflow_ulp_release(struct sock *ssk)
+{
+	struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
+	bool release = true;
+	struct sock *sk;
+
+	if (!ctx)
+		return;
+
+	sk = ctx->conn;
+	if (sk) {
+		/* if the msk has been orphaned, keep the ctx
+		 * alive, will be freed by __mptcp_close_ssk(),
+		 * when the subflow is still unaccepted
+		 */
+		release = ctx->disposable || list_empty(&ctx->node);
+
+		/* inet_child_forget() does not call sk_state_change(),
+		 * explicitly trigger the socket close machinery
+		 */
+		if (!release && !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW,
+						  &mptcp_sk(sk)->flags))
+			mptcp_schedule_work(sk);
+		sock_put(sk);
+	}
+
+	mptcp_subflow_ops_undo_override(ssk);
+	if (release)
+		kfree_rcu(ctx, rcu);
+}
+
+static void subflow_ulp_clone(const struct request_sock *req,
+			      struct sock *newsk,
+			      const gfp_t priority)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk);
+	struct mptcp_subflow_context *new_ctx;
+
+	if (!tcp_rsk(req)->is_mptcp ||
+	    (!subflow_req->mp_capable && !subflow_req->mp_join)) {
+		subflow_ulp_fallback(newsk, old_ctx);
+		return;
+	}
+
+	new_ctx = subflow_create_ctx(newsk, priority);
+	if (!new_ctx) {
+		subflow_ulp_fallback(newsk, old_ctx);
+		return;
+	}
+
+	new_ctx->conn_finished = 1;
+	new_ctx->icsk_af_ops = old_ctx->icsk_af_ops;
+	new_ctx->tcp_state_change = old_ctx->tcp_state_change;
+	new_ctx->tcp_error_report = old_ctx->tcp_error_report;
+	new_ctx->rel_write_seq = 1;
+
+	if (subflow_req->mp_capable) {
+		/* see comments in subflow_syn_recv_sock(), MPTCP connection
+		 * is fully established only after we receive the remote key
+		 */
+		new_ctx->mp_capable = 1;
+		new_ctx->local_key = subflow_req->local_key;
+		new_ctx->token = subflow_req->token;
+		new_ctx->ssn_offset = subflow_req->ssn_offset;
+		new_ctx->idsn = subflow_req->idsn;
+
+		/* this is the first subflow, id is always 0 */
+		subflow_set_local_id(new_ctx, 0);
+	} else if (subflow_req->mp_join) {
+		new_ctx->ssn_offset = subflow_req->ssn_offset;
+		new_ctx->mp_join = 1;
+		WRITE_ONCE(new_ctx->fully_established, true);
+		new_ctx->remote_key_valid = 1;
+		new_ctx->backup = subflow_req->backup;
+		new_ctx->request_bkup = subflow_req->request_bkup;
+		WRITE_ONCE(new_ctx->remote_id, subflow_req->remote_id);
+		new_ctx->token = subflow_req->token;
+
+		/* the subflow req id is valid, fetched via subflow_check_req()
+		 * and subflow_token_join_request()
+		 */
+		subflow_set_local_id(new_ctx, subflow_req->local_id);
+	}
+}
+
+static void tcp_release_cb_override(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	long status;
+
+	/* process and clear all the pending actions, but leave the subflow into
+	 * the napi queue. To respect locking, only the same CPU that originated
+	 * the action can touch the list. mptcp_napi_poll will take care of it.
+	 */
+	status = set_mask_bits(&subflow->delegated_status, MPTCP_DELEGATE_ACTIONS_MASK, 0);
+	if (status)
+		mptcp_subflow_process_delegated(ssk, status);
+
+	tcp_release_cb(ssk);
+}
+
+static int tcp_abort_override(struct sock *ssk, int err)
+{
+	/* closing a listener subflow requires a great deal of care.
+	 * keep it simple and just prevent such operation
+	 */
+	if (inet_sk_state_load(ssk) == TCP_LISTEN)
+		return -EINVAL;
+
+	return tcp_abort(ssk, err);
+}
+
+static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = {
+	.name		= "mptcp",
+	.owner		= THIS_MODULE,
+	.init		= subflow_ulp_init,
+	.release	= subflow_ulp_release,
+	.clone		= subflow_ulp_clone,
+};
+
+static int subflow_ops_init(struct request_sock_ops *subflow_ops)
+{
+	subflow_ops->obj_size = sizeof(struct mptcp_subflow_request_sock);
+
+	subflow_ops->slab = kmem_cache_create(subflow_ops->slab_name,
+					      subflow_ops->obj_size, 0,
+					      SLAB_ACCOUNT |
+					      SLAB_TYPESAFE_BY_RCU,
+					      NULL);
+	if (!subflow_ops->slab)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void __init mptcp_subflow_init(void)
+{
+	mptcp_subflow_v4_request_sock_ops = tcp_request_sock_ops;
+	mptcp_subflow_v4_request_sock_ops.slab_name = "request_sock_subflow_v4";
+	mptcp_subflow_v4_request_sock_ops.destructor = subflow_v4_req_destructor;
+
+	if (subflow_ops_init(&mptcp_subflow_v4_request_sock_ops) != 0)
+		panic("MPTCP: failed to init subflow v4 request sock ops\n");
+
+	subflow_request_sock_ipv4_ops = tcp_request_sock_ipv4_ops;
+	subflow_request_sock_ipv4_ops.route_req = subflow_v4_route_req;
+	subflow_request_sock_ipv4_ops.send_synack = subflow_v4_send_synack;
+
+	subflow_specific = ipv4_specific;
+	subflow_specific.conn_request = subflow_v4_conn_request;
+	subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
+	subflow_specific.sk_rx_dst_set = subflow_finish_connect;
+	subflow_specific.rebuild_header = subflow_rebuild_header;
+
+	tcp_prot_override = tcp_prot;
+	tcp_prot_override.release_cb = tcp_release_cb_override;
+	tcp_prot_override.diag_destroy = tcp_abort_override;
+#ifdef CONFIG_BPF_SYSCALL
+	/* Disable sockmap processing for subflows */
+	tcp_prot_override.psock_update_sk_prot = NULL;
+#endif
+
+	mptcp_diag_subflow_init(&subflow_ulp_ops);
+
+	if (tcp_register_ulp(&subflow_ulp_ops) != 0)
+		panic("MPTCP: failed to register subflows to ULP\n");
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+void __init mptcp_subflow_v6_init(void)
+{
+	/* In struct mptcp_subflow_request_sock, we assume the TCP request sock
+	 * structures for v4 and v6 have the same size. It should not changed in
+	 * the future but better to make sure to be warned if it is no longer
+	 * the case.
+	 */
+	BUILD_BUG_ON(sizeof(struct tcp_request_sock) != sizeof(struct tcp6_request_sock));
+
+	mptcp_subflow_v6_request_sock_ops = tcp6_request_sock_ops;
+	mptcp_subflow_v6_request_sock_ops.slab_name = "request_sock_subflow_v6";
+	mptcp_subflow_v6_request_sock_ops.destructor = subflow_v6_req_destructor;
+
+	if (subflow_ops_init(&mptcp_subflow_v6_request_sock_ops) != 0)
+		panic("MPTCP: failed to init subflow v6 request sock ops\n");
+
+	subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
+	subflow_request_sock_ipv6_ops.route_req = subflow_v6_route_req;
+	subflow_request_sock_ipv6_ops.send_synack = subflow_v6_send_synack;
+
+	subflow_v6_specific = ipv6_specific;
+	subflow_v6_specific.conn_request = subflow_v6_conn_request;
+	subflow_v6_specific.syn_recv_sock = subflow_syn_recv_sock;
+	subflow_v6_specific.sk_rx_dst_set = subflow_finish_connect;
+	subflow_v6_specific.rebuild_header = subflow_v6_rebuild_header;
+
+	subflow_v6m_specific = subflow_v6_specific;
+	subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;
+	subflow_v6m_specific.net_header_len = ipv4_specific.net_header_len;
+	subflow_v6m_specific.mtu_reduced = ipv4_specific.mtu_reduced;
+	subflow_v6m_specific.rebuild_header = subflow_rebuild_header;
+
+	tcpv6_prot_override = tcpv6_prot;
+	tcpv6_prot_override.release_cb = tcp_release_cb_override;
+	tcpv6_prot_override.diag_destroy = tcp_abort_override;
+#ifdef CONFIG_BPF_SYSCALL
+	/* Disable sockmap processing for subflows */
+	tcpv6_prot_override.psock_update_sk_prot = NULL;
+#endif
+}
+#endif
diff --git a/net/mptcp/syncookies.c b/net/mptcp/syncookies.c
new file mode 100644
index 000000000..947470664
--- /dev/null
+++ b/net/mptcp/syncookies.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/skbuff.h>
+
+#include "protocol.h"
+
+/* Syncookies do not work for JOIN requests.
+ *
+ * Unlike MP_CAPABLE, where the ACK cookie contains the needed MPTCP
+ * options to reconstruct the initial syn state, MP_JOIN does not contain
+ * the token to obtain the mptcp socket nor the server-generated nonce
+ * that was used in the cookie SYN/ACK response.
+ *
+ * Keep a small best effort state table to store the syn/synack data,
+ * indexed by skb hash.
+ *
+ * A MP_JOIN SYN packet handled by syn cookies is only stored if the 32bit
+ * token matches a known mptcp connection that can still accept more subflows.
+ *
+ * There is no timeout handling -- state is only re-constructed
+ * when the TCP ACK passed the cookie validation check.
+ */
+
+struct join_entry {
+	u32 token;
+	u32 remote_nonce;
+	u32 local_nonce;
+	u8 join_id;
+	u8 local_id;
+	u8 backup:1,
+	   request_bkup:1;
+	u8 valid;
+};
+
+#define COOKIE_JOIN_SLOTS	1024
+
+static struct join_entry join_entries[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp;
+static spinlock_t join_entry_locks[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp;
+
+static u32 mptcp_join_entry_hash(struct sk_buff *skb, struct net *net)
+{
+	static u32 mptcp_join_hash_secret __read_mostly;
+	struct tcphdr *th = tcp_hdr(skb);
+	u32 seq, i;
+
+	net_get_random_once(&mptcp_join_hash_secret,
+			    sizeof(mptcp_join_hash_secret));
+
+	if (th->syn)
+		seq = TCP_SKB_CB(skb)->seq;
+	else
+		seq = TCP_SKB_CB(skb)->seq - 1;
+
+	i = jhash_3words(seq, net_hash_mix(net),
+			 (__force __u32)th->source << 16 | (__force __u32)th->dest,
+			 mptcp_join_hash_secret);
+
+	return i % ARRAY_SIZE(join_entries);
+}
+
+static void mptcp_join_store_state(struct join_entry *entry,
+				   const struct mptcp_subflow_request_sock *subflow_req)
+{
+	entry->token = subflow_req->token;
+	entry->remote_nonce = subflow_req->remote_nonce;
+	entry->local_nonce = subflow_req->local_nonce;
+	entry->backup = subflow_req->backup;
+	entry->request_bkup = subflow_req->request_bkup;
+	entry->join_id = subflow_req->remote_id;
+	entry->local_id = subflow_req->local_id;
+	entry->valid = 1;
+}
+
+void subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,
+				       struct sk_buff *skb)
+{
+	struct net *net = read_pnet(&subflow_req->sk.req.ireq_net);
+	u32 i = mptcp_join_entry_hash(skb, net);
+
+	/* No use in waiting if other cpu is already using this slot --
+	 * would overwrite the data that got stored.
+	 */
+	spin_lock_bh(&join_entry_locks[i]);
+	mptcp_join_store_state(&join_entries[i], subflow_req);
+	spin_unlock_bh(&join_entry_locks[i]);
+}
+
+/* Called for a cookie-ack with MP_JOIN option present.
+ * Look up the saved state based on skb hash & check token matches msk
+ * in same netns.
+ *
+ * Caller will check msk can still accept another subflow.  The hmac
+ * present in the cookie ACK mptcp option space will be checked later.
+ */
+bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,
+					struct sk_buff *skb)
+{
+	struct net *net = read_pnet(&subflow_req->sk.req.ireq_net);
+	u32 i = mptcp_join_entry_hash(skb, net);
+	struct mptcp_sock *msk;
+	struct join_entry *e;
+
+	e = &join_entries[i];
+
+	spin_lock_bh(&join_entry_locks[i]);
+
+	if (e->valid == 0) {
+		spin_unlock_bh(&join_entry_locks[i]);
+		return false;
+	}
+
+	e->valid = 0;
+
+	msk = mptcp_token_get_sock(net, e->token);
+	if (!msk) {
+		spin_unlock_bh(&join_entry_locks[i]);
+		return false;
+	}
+
+	subflow_req->remote_nonce = e->remote_nonce;
+	subflow_req->local_nonce = e->local_nonce;
+	subflow_req->backup = e->backup;
+	subflow_req->request_bkup = e->request_bkup;
+	subflow_req->remote_id = e->join_id;
+	subflow_req->local_id = e->local_id;
+	subflow_req->token = e->token;
+	subflow_req->msk = msk;
+	spin_unlock_bh(&join_entry_locks[i]);
+	return true;
+}
+
+void __init mptcp_join_cookie_init(void)
+{
+	int i;
+
+	for (i = 0; i < COOKIE_JOIN_SLOTS; i++)
+		spin_lock_init(&join_entry_locks[i]);
+}
diff --git a/net/mptcp/token.c b/net/mptcp/token.c
new file mode 100644
index 000000000..f1a50f367
--- /dev/null
+++ b/net/mptcp/token.c
@@ -0,0 +1,424 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP token management
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ *
+ * Note: This code is based on mptcp_ctrl.c from multipath-tcp.org,
+ *       authored by:
+ *
+ *       Sébastien Barré <sebastien.barre@uclouvain.be>
+ *       Christoph Paasch <christoph.paasch@uclouvain.be>
+ *       Jaakko Korkeaniemi <jaakko.korkeaniemi@aalto.fi>
+ *       Gregory Detal <gregory.detal@uclouvain.be>
+ *       Fabien Duchêne <fabien.duchene@uclouvain.be>
+ *       Andreas Seelinger <Andreas.Seelinger@rwth-aachen.de>
+ *       Lavkesh Lahngir <lavkesh51@gmail.com>
+ *       Andreas Ripke <ripke@neclab.eu>
+ *       Vlad Dogaru <vlad.dogaru@intel.com>
+ *       Octavian Purdila <octavian.purdila@intel.com>
+ *       John Ronan <jronan@tssg.org>
+ *       Catalin Nicutar <catalin.nicutar@gmail.com>
+ *       Brandon Heller <brandonh@stanford.edu>
+ */
+
+#define pr_fmt(fmt) "MPTCP: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/memblock.h>
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <net/sock.h>
+#include <net/inet_common.h>
+#include <net/protocol.h>
+#include <net/mptcp.h>
+#include "protocol.h"
+
+#define TOKEN_MAX_CHAIN_LEN	4
+
+struct token_bucket {
+	spinlock_t		lock;
+	int			chain_len;
+	struct hlist_nulls_head	req_chain;
+	struct hlist_nulls_head	msk_chain;
+};
+
+static struct token_bucket *token_hash __read_mostly;
+static unsigned int token_mask __read_mostly;
+
+static struct token_bucket *token_bucket(u32 token)
+{
+	return &token_hash[token & token_mask];
+}
+
+/* called with bucket lock held */
+static struct mptcp_subflow_request_sock *
+__token_lookup_req(struct token_bucket *t, u32 token)
+{
+	struct mptcp_subflow_request_sock *req;
+	struct hlist_nulls_node *pos;
+
+	hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node)
+		if (req->token == token)
+			return req;
+	return NULL;
+}
+
+/* called with bucket lock held */
+static struct mptcp_sock *
+__token_lookup_msk(struct token_bucket *t, u32 token)
+{
+	struct hlist_nulls_node *pos;
+	struct sock *sk;
+
+	sk_nulls_for_each_rcu(sk, pos, &t->msk_chain)
+		if (mptcp_sk(sk)->token == token)
+			return mptcp_sk(sk);
+	return NULL;
+}
+
+static bool __token_bucket_busy(struct token_bucket *t, u32 token)
+{
+	return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN ||
+	       __token_lookup_req(t, token) || __token_lookup_msk(t, token);
+}
+
+static void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
+{
+	/* we might consider a faster version that computes the key as a
+	 * hash of some information available in the MPTCP socket. Use
+	 * random data at the moment, as it's probably the safest option
+	 * in case multiple sockets are opened in different namespaces at
+	 * the same time.
+	 */
+	get_random_bytes(key, sizeof(u64));
+	mptcp_crypto_key_sha(*key, token, idsn);
+}
+
+/**
+ * mptcp_token_new_request - create new key/idsn/token for subflow_request
+ * @req: the request socket
+ *
+ * This function is called when a new mptcp connection is coming in.
+ *
+ * It creates a unique token to identify the new mptcp connection,
+ * a secret local key and the initial data sequence number (idsn).
+ *
+ * Return: 0 on success.
+ */
+int mptcp_token_new_request(struct request_sock *req)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct token_bucket *bucket;
+	u32 token;
+
+	mptcp_crypto_key_sha(subflow_req->local_key,
+			     &subflow_req->token,
+			     &subflow_req->idsn);
+	pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
+		 req, subflow_req->local_key, subflow_req->token,
+		 subflow_req->idsn);
+
+	token = subflow_req->token;
+	bucket = token_bucket(token);
+	spin_lock_bh(&bucket->lock);
+	if (__token_bucket_busy(bucket, token)) {
+		spin_unlock_bh(&bucket->lock);
+		return -EBUSY;
+	}
+
+	hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain);
+	bucket->chain_len++;
+	spin_unlock_bh(&bucket->lock);
+	return 0;
+}
+
+/**
+ * mptcp_token_new_connect - create new key/idsn/token for subflow
+ * @ssk: the socket that will initiate a connection
+ *
+ * This function is called when a new outgoing mptcp connection is
+ * initiated.
+ *
+ * It creates a unique token to identify the new mptcp connection,
+ * a secret local key and the initial data sequence number (idsn).
+ *
+ * On success, the mptcp connection can be found again using
+ * the computed token at a later time, this is needed to process
+ * join requests.
+ *
+ * Return: 0 on success.
+ */
+int mptcp_token_new_connect(struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	int retries = MPTCP_TOKEN_MAX_RETRIES;
+	struct sock *sk = subflow->conn;
+	struct token_bucket *bucket;
+
+again:
+	mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
+				 &subflow->idsn);
+
+	bucket = token_bucket(subflow->token);
+	spin_lock_bh(&bucket->lock);
+	if (__token_bucket_busy(bucket, subflow->token)) {
+		spin_unlock_bh(&bucket->lock);
+		if (!--retries)
+			return -EBUSY;
+		goto again;
+	}
+
+	pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
+		 ssk, subflow->local_key, subflow->token, subflow->idsn);
+
+	WRITE_ONCE(msk->token, subflow->token);
+	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
+	bucket->chain_len++;
+	spin_unlock_bh(&bucket->lock);
+	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
+	return 0;
+}
+
+/**
+ * mptcp_token_accept - replace a req sk with full sock in token hash
+ * @req: the request socket to be removed
+ * @msk: the just cloned socket linked to the new connection
+ *
+ * Called when a SYN packet creates a new logical connection, i.e.
+ * is not a join request.
+ */
+void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
+			struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_request_sock *pos;
+	struct sock *sk = (struct sock *)msk;
+	struct token_bucket *bucket;
+
+	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
+	bucket = token_bucket(req->token);
+	spin_lock_bh(&bucket->lock);
+
+	/* pedantic lookup check for the moved token */
+	pos = __token_lookup_req(bucket, req->token);
+	if (!WARN_ON_ONCE(pos != req))
+		hlist_nulls_del_init_rcu(&req->token_node);
+	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
+	spin_unlock_bh(&bucket->lock);
+}
+
+bool mptcp_token_exists(u32 token)
+{
+	struct hlist_nulls_node *pos;
+	struct token_bucket *bucket;
+	struct mptcp_sock *msk;
+	struct sock *sk;
+
+	rcu_read_lock();
+	bucket = token_bucket(token);
+
+again:
+	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
+		msk = mptcp_sk(sk);
+		if (READ_ONCE(msk->token) == token)
+			goto found;
+	}
+	if (get_nulls_value(pos) != (token & token_mask))
+		goto again;
+
+	rcu_read_unlock();
+	return false;
+found:
+	rcu_read_unlock();
+	return true;
+}
+
+/**
+ * mptcp_token_get_sock - retrieve mptcp connection sock using its token
+ * @net: restrict to this namespace
+ * @token: token of the mptcp connection to retrieve
+ *
+ * This function returns the mptcp connection structure with the given token.
+ * A reference count on the mptcp socket returned is taken.
+ *
+ * Return: NULL if no connection with the given token value exists.
+ */
+struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token)
+{
+	struct hlist_nulls_node *pos;
+	struct token_bucket *bucket;
+	struct mptcp_sock *msk;
+	struct sock *sk;
+
+	rcu_read_lock();
+	bucket = token_bucket(token);
+
+again:
+	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
+		msk = mptcp_sk(sk);
+		if (READ_ONCE(msk->token) != token ||
+		    !net_eq(sock_net(sk), net))
+			continue;
+
+		if (!refcount_inc_not_zero(&sk->sk_refcnt))
+			goto not_found;
+
+		if (READ_ONCE(msk->token) != token ||
+		    !net_eq(sock_net(sk), net)) {
+			sock_put(sk);
+			goto again;
+		}
+		goto found;
+	}
+	if (get_nulls_value(pos) != (token & token_mask))
+		goto again;
+
+not_found:
+	msk = NULL;
+
+found:
+	rcu_read_unlock();
+	return msk;
+}
+EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
+
+/**
+ * mptcp_token_iter_next - iterate over the token container from given pos
+ * @net: namespace to be iterated
+ * @s_slot: start slot number
+ * @s_num: start number inside the given lock
+ *
+ * Description:
+ *   On successful iteration, the iterator is moved to the next position and a
+ *   reference to the returned socket is acquired.
+ *
+ * Return:
+ *   The first mptcp connection structure found inside the token container
+ *   starting from the specified position, or NULL.
+ */
+struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
+					 long *s_num)
+{
+	struct mptcp_sock *ret = NULL;
+	struct hlist_nulls_node *pos;
+	int slot, num = 0;
+
+	for (slot = *s_slot; slot <= token_mask; *s_num = 0, slot++) {
+		struct token_bucket *bucket = &token_hash[slot];
+		struct sock *sk;
+
+		num = 0;
+
+		if (hlist_nulls_empty(&bucket->msk_chain))
+			continue;
+
+		rcu_read_lock();
+		sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
+			++num;
+			if (!net_eq(sock_net(sk), net))
+				continue;
+
+			if (num <= *s_num)
+				continue;
+
+			if (!refcount_inc_not_zero(&sk->sk_refcnt))
+				continue;
+
+			if (!net_eq(sock_net(sk), net)) {
+				sock_put(sk);
+				continue;
+			}
+
+			ret = mptcp_sk(sk);
+			rcu_read_unlock();
+			goto out;
+		}
+		rcu_read_unlock();
+	}
+
+out:
+	*s_slot = slot;
+	*s_num = num;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(mptcp_token_iter_next);
+
+/**
+ * mptcp_token_destroy_request - remove mptcp connection/token
+ * @req: mptcp request socket dropping the token
+ *
+ * Remove the token associated to @req.
+ */
+void mptcp_token_destroy_request(struct request_sock *req)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct mptcp_subflow_request_sock *pos;
+	struct token_bucket *bucket;
+
+	if (hlist_nulls_unhashed(&subflow_req->token_node))
+		return;
+
+	bucket = token_bucket(subflow_req->token);
+	spin_lock_bh(&bucket->lock);
+	pos = __token_lookup_req(bucket, subflow_req->token);
+	if (!WARN_ON_ONCE(pos != subflow_req)) {
+		hlist_nulls_del_init_rcu(&pos->token_node);
+		bucket->chain_len--;
+	}
+	spin_unlock_bh(&bucket->lock);
+}
+
+/**
+ * mptcp_token_destroy - remove mptcp connection/token
+ * @msk: mptcp connection dropping the token
+ *
+ * Remove the token associated to @msk
+ */
+void mptcp_token_destroy(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct token_bucket *bucket;
+	struct mptcp_sock *pos;
+
+	if (sk_unhashed((struct sock *)msk))
+		return;
+
+	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
+	bucket = token_bucket(msk->token);
+	spin_lock_bh(&bucket->lock);
+	pos = __token_lookup_msk(bucket, msk->token);
+	if (!WARN_ON_ONCE(pos != msk)) {
+		__sk_nulls_del_node_init_rcu((struct sock *)pos);
+		bucket->chain_len--;
+	}
+	spin_unlock_bh(&bucket->lock);
+	WRITE_ONCE(msk->token, 0);
+}
+
+void __init mptcp_token_init(void)
+{
+	int i;
+
+	token_hash = alloc_large_system_hash("MPTCP token",
+					     sizeof(struct token_bucket),
+					     0,
+					     20,/* one slot per 1MB of memory */
+					     HASH_ZERO,
+					     NULL,
+					     &token_mask,
+					     0,
+					     64 * 1024);
+	for (i = 0; i < token_mask + 1; ++i) {
+		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
+		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
+		spin_lock_init(&token_hash[i].lock);
+	}
+}
+
+#if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)
+EXPORT_SYMBOL_GPL(mptcp_token_new_request);
+EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
+EXPORT_SYMBOL_GPL(mptcp_token_accept);
+EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
+EXPORT_SYMBOL_GPL(mptcp_token_destroy);
+#endif
diff --git a/net/mptcp/token_test.c b/net/mptcp/token_test.c
new file mode 100644
index 000000000..4fc39fa2e
--- /dev/null
+++ b/net/mptcp/token_test.c
@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <kunit/test.h>
+
+#include "protocol.h"
+
+static struct mptcp_subflow_request_sock *build_req_sock(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req;
+
+	req = kunit_kzalloc(test, sizeof(struct mptcp_subflow_request_sock),
+			    GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, req);
+	mptcp_token_init_request((struct request_sock *)req);
+	sock_net_set((struct sock *)req, &init_net);
+	return req;
+}
+
+static void mptcp_token_test_req_basic(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *null_msk = NULL;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	KUNIT_EXPECT_NE(test, 0, (int)req->token);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, req->token));
+
+	/* cleanup */
+	mptcp_token_destroy_request((struct request_sock *)req);
+}
+
+static struct inet_connection_sock *build_icsk(struct kunit *test)
+{
+	struct inet_connection_sock *icsk;
+
+	icsk = kunit_kzalloc(test, sizeof(struct inet_connection_sock),
+			     GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, icsk);
+	return icsk;
+}
+
+static struct mptcp_subflow_context *build_ctx(struct kunit *test)
+{
+	struct mptcp_subflow_context *ctx;
+
+	ctx = kunit_kzalloc(test, sizeof(struct mptcp_subflow_context),
+			    GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, ctx);
+	return ctx;
+}
+
+static struct mptcp_sock *build_msk(struct kunit *test)
+{
+	struct mptcp_sock *msk;
+	struct sock *sk;
+
+	msk = kunit_kzalloc(test, sizeof(struct mptcp_sock), GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, msk);
+	refcount_set(&((struct sock *)msk)->sk_refcnt, 1);
+	sock_net_set((struct sock *)msk, &init_net);
+
+	sk = (struct sock *)msk;
+
+	/* be sure the token helpers can dereference sk->sk_prot */
+	sk->sk_prot = &tcp_prot;
+	sk->sk_protocol = IPPROTO_MPTCP;
+
+	return msk;
+}
+
+static void mptcp_token_test_msk_basic(struct kunit *test)
+{
+	struct inet_connection_sock *icsk = build_icsk(test);
+	struct mptcp_subflow_context *ctx = build_ctx(test);
+	struct mptcp_sock *msk = build_msk(test);
+	struct mptcp_sock *null_msk = NULL;
+	struct sock *sk;
+
+	rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
+	ctx->conn = (struct sock *)msk;
+	sk = (struct sock *)msk;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_connect((struct sock *)icsk));
+	KUNIT_EXPECT_NE(test, 0, (int)ctx->token);
+	KUNIT_EXPECT_EQ(test, ctx->token, msk->token);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, ctx->token));
+	KUNIT_EXPECT_EQ(test, 2, (int)refcount_read(&sk->sk_refcnt));
+
+	mptcp_token_destroy(msk);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, ctx->token));
+}
+
+static void mptcp_token_test_accept(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *msk = build_msk(test);
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	msk->token = req->token;
+	mptcp_token_accept(req, msk);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, msk->token));
+
+	/* this is now a no-op */
+	mptcp_token_destroy_request((struct request_sock *)req);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, msk->token));
+
+	/* cleanup */
+	mptcp_token_destroy(msk);
+}
+
+static void mptcp_token_test_destroyed(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *msk = build_msk(test);
+	struct mptcp_sock *null_msk = NULL;
+	struct sock *sk;
+
+	sk = (struct sock *)msk;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	msk->token = req->token;
+	mptcp_token_accept(req, msk);
+
+	/* simulate race on removal */
+	refcount_set(&sk->sk_refcnt, 0);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, msk->token));
+
+	/* cleanup */
+	mptcp_token_destroy(msk);
+}
+
+static struct kunit_case mptcp_token_test_cases[] = {
+	KUNIT_CASE(mptcp_token_test_req_basic),
+	KUNIT_CASE(mptcp_token_test_msk_basic),
+	KUNIT_CASE(mptcp_token_test_accept),
+	KUNIT_CASE(mptcp_token_test_destroyed),
+	{}
+};
+
+static struct kunit_suite mptcp_token_suite = {
+	.name = "mptcp-token",
+	.test_cases = mptcp_token_test_cases,
+};
+
+kunit_test_suite(mptcp_token_suite);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("KUnit tests for MPTCP Token");