sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 414 insertions, 0 deletions

diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
new file mode 100644
index 000000000..abd77162f
--- /dev/null
+++ b/net/ipv4/esp4_offload.c
@@ -0,0 +1,414 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * IPV4 GSO/GRO offload support
+ * Linux INET implementation
+ *
+ * Copyright (C) 2016 secunet Security Networks AG
+ * Author: Steffen Klassert <steffen.klassert@secunet.com>
+ *
+ * ESP GRO support
+ */
+
+#include <linux/skbuff.h>
+#include <linux/init.h>
+#include <net/protocol.h>
+#include <crypto/aead.h>
+#include <crypto/authenc.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <net/gro.h>
+#include <net/gso.h>
+#include <net/ip.h>
+#include <net/xfrm.h>
+#include <net/esp.h>
+#include <linux/scatterlist.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <net/udp.h>
+
+static struct sk_buff *esp4_gro_receive(struct list_head *head,
+					struct sk_buff *skb)
+{
+	int offset = skb_gro_offset(skb);
+	struct xfrm_offload *xo;
+	struct xfrm_state *x;
+	int encap_type = 0;
+	__be32 seq;
+	__be32 spi;
+
+	if (!pskb_pull(skb, offset))
+		return NULL;
+
+	if (xfrm_parse_spi(skb, IPPROTO_ESP, &spi, &seq) != 0)
+		goto out;
+
+	xo = xfrm_offload(skb);
+	if (!xo || !(xo->flags & CRYPTO_DONE)) {
+		struct sec_path *sp = secpath_set(skb);
+
+		if (!sp)
+			goto out;
+
+		if (sp->len == XFRM_MAX_DEPTH)
+			goto out_reset;
+
+		x = xfrm_input_state_lookup(dev_net(skb->dev), skb->mark,
+					    (xfrm_address_t *)&ip_hdr(skb)->daddr,
+					    spi, IPPROTO_ESP, AF_INET);
+
+		if (unlikely(x && x->dir && x->dir != XFRM_SA_DIR_IN)) {
+			/* non-offload path will record the error and audit log */
+			xfrm_state_put(x);
+			x = NULL;
+		}
+
+		if (!x)
+			goto out_reset;
+
+		skb->mark = xfrm_smark_get(skb->mark, x);
+
+		sp->xvec[sp->len++] = x;
+		sp->olen++;
+
+		xo = xfrm_offload(skb);
+		if (!xo)
+			goto out_reset;
+	}
+
+	xo->flags |= XFRM_GRO;
+
+	if (NAPI_GRO_CB(skb)->proto == IPPROTO_UDP)
+		encap_type = UDP_ENCAP_ESPINUDP;
+
+	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
+	XFRM_SPI_SKB_CB(skb)->family = AF_INET;
+	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
+	XFRM_SPI_SKB_CB(skb)->seq = seq;
+
+	/* We don't need to handle errors from xfrm_input, it does all
+	 * the error handling and frees the resources on error. */
+	xfrm_input(skb, IPPROTO_ESP, spi, encap_type);
+
+	return ERR_PTR(-EINPROGRESS);
+out_reset:
+	secpath_reset(skb);
+out:
+	skb_push(skb, offset);
+	NAPI_GRO_CB(skb)->same_flow = 0;
+	NAPI_GRO_CB(skb)->flush = 1;
+
+	return NULL;
+}
+
+static void esp4_gso_encap(struct xfrm_state *x, struct sk_buff *skb)
+{
+	struct ip_esp_hdr *esph;
+	struct iphdr *iph = ip_hdr(skb);
+	struct xfrm_offload *xo = xfrm_offload(skb);
+	int proto = iph->protocol;
+
+	skb_push(skb, -skb_network_offset(skb));
+	esph = ip_esp_hdr(skb);
+	*skb_mac_header(skb) = IPPROTO_ESP;
+
+	esph->spi = x->id.spi;
+	esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
+
+	xo->proto = proto;
+}
+
+static struct sk_buff *xfrm4_tunnel_gso_segment(struct xfrm_state *x,
+						struct sk_buff *skb,
+						netdev_features_t features)
+{
+	struct xfrm_offload *xo = xfrm_offload(skb);
+	const struct xfrm_mode *inner_mode = xfrm_ip2inner_mode(x, xo->proto);
+	__be16 type = inner_mode->family == AF_INET6 ? htons(ETH_P_IPV6)
+						     : htons(ETH_P_IP);
+
+	return skb_eth_gso_segment(skb, features, type);
+}
+
+static struct sk_buff *xfrm4_transport_gso_segment(struct xfrm_state *x,
+						   struct sk_buff *skb,
+						   netdev_features_t features)
+{
+	const struct net_offload *ops;
+	struct sk_buff *segs = ERR_PTR(-EINVAL);
+	struct xfrm_offload *xo = xfrm_offload(skb);
+
+	skb->transport_header += x->props.header_len;
+	ops = rcu_dereference(inet_offloads[xo->proto]);
+	if (likely(ops && ops->callbacks.gso_segment))
+		segs = ops->callbacks.gso_segment(skb, features);
+
+	return segs;
+}
+
+static struct sk_buff *xfrm4_beet_gso_segment(struct xfrm_state *x,
+					      struct sk_buff *skb,
+					      netdev_features_t features)
+{
+	struct xfrm_offload *xo = xfrm_offload(skb);
+	struct sk_buff *segs = ERR_PTR(-EINVAL);
+	const struct net_offload *ops;
+	u8 proto = xo->proto;
+
+	skb->transport_header += x->props.header_len;
+
+	if (x->sel.family != AF_INET6) {
+		if (proto == IPPROTO_BEETPH) {
+			struct ip_beet_phdr *ph =
+				(struct ip_beet_phdr *)skb->data;
+
+			skb->transport_header += ph->hdrlen * 8;
+			proto = ph->nexthdr;
+		} else {
+			skb->transport_header -= IPV4_BEET_PHMAXLEN;
+		}
+	} else {
+		__be16 frag;
+
+		skb->transport_header +=
+			ipv6_skip_exthdr(skb, 0, &proto, &frag);
+		if (proto == IPPROTO_TCP)
+			skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
+	}
+
+	if (proto == IPPROTO_IPV6)
+		skb_shinfo(skb)->gso_type |= SKB_GSO_IPXIP4;
+
+	__skb_pull(skb, skb_transport_offset(skb));
+	ops = rcu_dereference(inet_offloads[proto]);
+	if (likely(ops && ops->callbacks.gso_segment))
+		segs = ops->callbacks.gso_segment(skb, features);
+
+	return segs;
+}
+
+static struct sk_buff *xfrm4_outer_mode_gso_segment(struct xfrm_state *x,
+						    struct sk_buff *skb,
+						    netdev_features_t features)
+{
+	switch (x->outer_mode.encap) {
+	case XFRM_MODE_TUNNEL:
+		return xfrm4_tunnel_gso_segment(x, skb, features);
+	case XFRM_MODE_TRANSPORT:
+		return xfrm4_transport_gso_segment(x, skb, features);
+	case XFRM_MODE_BEET:
+		return xfrm4_beet_gso_segment(x, skb, features);
+	}
+
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+static struct sk_buff *esp4_gso_segment(struct sk_buff *skb,
+				        netdev_features_t features)
+{
+	struct xfrm_state *x;
+	struct ip_esp_hdr *esph;
+	struct crypto_aead *aead;
+	netdev_features_t esp_features = features;
+	struct xfrm_offload *xo = xfrm_offload(skb);
+	struct sec_path *sp;
+
+	if (!xo)
+		return ERR_PTR(-EINVAL);
+
+	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_ESP))
+		return ERR_PTR(-EINVAL);
+
+	sp = skb_sec_path(skb);
+	x = sp->xvec[sp->len - 1];
+	aead = x->data;
+	esph = ip_esp_hdr(skb);
+
+	if (esph->spi != x->id.spi)
+		return ERR_PTR(-EINVAL);
+
+	if (!pskb_may_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead)))
+		return ERR_PTR(-EINVAL);
+
+	__skb_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead));
+
+	skb->encap_hdr_csum = 1;
+
+	if ((!(skb->dev->gso_partial_features & NETIF_F_HW_ESP) &&
+	     !(features & NETIF_F_HW_ESP)) || x->xso.dev != skb->dev)
+		esp_features = features & ~(NETIF_F_SG | NETIF_F_CSUM_MASK |
+					    NETIF_F_SCTP_CRC);
+	else if (!(features & NETIF_F_HW_ESP_TX_CSUM) &&
+		 !(skb->dev->gso_partial_features & NETIF_F_HW_ESP_TX_CSUM))
+		esp_features = features & ~(NETIF_F_CSUM_MASK |
+					    NETIF_F_SCTP_CRC);
+
+	xo->flags |= XFRM_GSO_SEGMENT;
+
+	return xfrm4_outer_mode_gso_segment(x, skb, esp_features);
+}
+
+static int esp_input_tail(struct xfrm_state *x, struct sk_buff *skb)
+{
+	struct crypto_aead *aead = x->data;
+	struct xfrm_offload *xo = xfrm_offload(skb);
+
+	if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead)))
+		return -EINVAL;
+
+	if (!(xo->flags & CRYPTO_DONE))
+		skb->ip_summed = CHECKSUM_NONE;
+
+	return esp_input_done2(skb, 0);
+}
+
+static int esp_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features_t features)
+{
+	int err;
+	int alen;
+	int blksize;
+	struct xfrm_offload *xo;
+	struct ip_esp_hdr *esph;
+	struct crypto_aead *aead;
+	struct esp_info esp;
+	bool hw_offload = true;
+	__u32 seq;
+	int encap_type = 0;
+
+	esp.inplace = true;
+
+	xo = xfrm_offload(skb);
+
+	if (!xo)
+		return -EINVAL;
+
+	if ((!(features & NETIF_F_HW_ESP) &&
+	     !(skb->dev->gso_partial_features & NETIF_F_HW_ESP)) ||
+	    x->xso.dev != skb->dev) {
+		xo->flags |= CRYPTO_FALLBACK;
+		hw_offload = false;
+	}
+
+	esp.proto = xo->proto;
+
+	/* skb is pure payload to encrypt */
+
+	aead = x->data;
+	alen = crypto_aead_authsize(aead);
+
+	esp.tfclen = 0;
+	/* XXX: Add support for tfc padding here. */
+
+	blksize = ALIGN(crypto_aead_blocksize(aead), 4);
+	esp.clen = ALIGN(skb->len + 2 + esp.tfclen, blksize);
+	esp.plen = esp.clen - skb->len - esp.tfclen;
+	esp.tailen = esp.tfclen + esp.plen + alen;
+
+	esp.esph = ip_esp_hdr(skb);
+
+	if (x->encap)
+		encap_type = x->encap->encap_type;
+
+	if (!hw_offload || !skb_is_gso(skb) || (hw_offload && encap_type == UDP_ENCAP_ESPINUDP)) {
+		esp.nfrags = esp_output_head(x, skb, &esp);
+		if (esp.nfrags < 0)
+			return esp.nfrags;
+	}
+
+	seq = xo->seq.low;
+
+	esph = esp.esph;
+	esph->spi = x->id.spi;
+
+	skb_push(skb, -skb_network_offset(skb));
+
+	if (xo->flags & XFRM_GSO_SEGMENT) {
+		esph->seq_no = htonl(seq);
+
+		if (!skb_is_gso(skb))
+			xo->seq.low++;
+		else
+			xo->seq.low += skb_shinfo(skb)->gso_segs;
+	}
+
+	if (xo->seq.low < seq)
+		xo->seq.hi++;
+
+	esp.seqno = cpu_to_be64(seq + ((u64)xo->seq.hi << 32));
+
+	if (hw_offload && encap_type == UDP_ENCAP_ESPINUDP) {
+		/* In the XFRM stack, the encapsulation protocol is set to iphdr->protocol by
+		 * setting *skb_mac_header(skb) (see esp_output_udp_encap()) where skb->mac_header
+		 * points to iphdr->protocol (see xfrm4_tunnel_encap_add()).
+		 * However, in esp_xmit(), skb->mac_header doesn't point to iphdr->protocol.
+		 * Therefore, the protocol field needs to be corrected.
+		 */
+		ip_hdr(skb)->protocol = IPPROTO_UDP;
+
+		esph->seq_no = htonl(seq);
+	}
+
+	ip_hdr(skb)->tot_len = htons(skb->len);
+	ip_send_check(ip_hdr(skb));
+
+	if (hw_offload) {
+		if (!skb_ext_add(skb, SKB_EXT_SEC_PATH))
+			return -ENOMEM;
+
+		xo = xfrm_offload(skb);
+		if (!xo)
+			return -EINVAL;
+
+		xo->flags |= XFRM_XMIT;
+		return 0;
+	}
+
+	err = esp_output_tail(x, skb, &esp);
+	if (err)
+		return err;
+
+	secpath_reset(skb);
+
+	if (skb_needs_linearize(skb, skb->dev->features) &&
+	    __skb_linearize(skb))
+		return -ENOMEM;
+	return 0;
+}
+
+static const struct net_offload esp4_offload = {
+	.callbacks = {
+		.gro_receive = esp4_gro_receive,
+		.gso_segment = esp4_gso_segment,
+	},
+};
+
+static const struct xfrm_type_offload esp_type_offload = {
+	.owner		= THIS_MODULE,
+	.proto	     	= IPPROTO_ESP,
+	.input_tail	= esp_input_tail,
+	.xmit		= esp_xmit,
+	.encap		= esp4_gso_encap,
+};
+
+static int __init esp4_offload_init(void)
+{
+	if (xfrm_register_type_offload(&esp_type_offload, AF_INET) < 0) {
+		pr_info("%s: can't add xfrm type offload\n", __func__);
+		return -EAGAIN;
+	}
+
+	return inet_add_offload(&esp4_offload, IPPROTO_ESP);
+}
+
+static void __exit esp4_offload_exit(void)
+{
+	xfrm_unregister_type_offload(&esp_type_offload, AF_INET);
+	inet_del_offload(&esp4_offload, IPPROTO_ESP);
+}
+
+module_init(esp4_offload_init);
+module_exit(esp4_offload_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");
+MODULE_ALIAS_XFRM_OFFLOAD_TYPE(AF_INET, XFRM_PROTO_ESP);
+MODULE_DESCRIPTION("IPV4 GSO/GRO offload support");