Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 1524 insertions, 0 deletions

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
new file mode 100644
index 000000000..d409f606a
--- /dev/null
+++ b/net/ipv4/arp.c
@@ -0,0 +1,1524 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* linux/net/ipv4/arp.c
+ *
+ * Copyright (C) 1994 by Florian  La Roche
+ *
+ * This module implements the Address Resolution Protocol ARP (RFC 826),
+ * which is used to convert IP addresses (or in the future maybe other
+ * high-level addresses) into a low-level hardware address (like an Ethernet
+ * address).
+ *
+ * Fixes:
+ *		Alan Cox	:	Removed the Ethernet assumptions in
+ *					Florian's code
+ *		Alan Cox	:	Fixed some small errors in the ARP
+ *					logic
+ *		Alan Cox	:	Allow >4K in /proc
+ *		Alan Cox	:	Make ARP add its own protocol entry
+ *		Ross Martin     :       Rewrote arp_rcv() and arp_get_info()
+ *		Stephen Henson	:	Add AX25 support to arp_get_info()
+ *		Alan Cox	:	Drop data when a device is downed.
+ *		Alan Cox	:	Use init_timer().
+ *		Alan Cox	:	Double lock fixes.
+ *		Martin Seine	:	Move the arphdr structure
+ *					to if_arp.h for compatibility.
+ *					with BSD based programs.
+ *		Andrew Tridgell :       Added ARP netmask code and
+ *					re-arranged proxy handling.
+ *		Alan Cox	:	Changed to use notifiers.
+ *		Niibe Yutaka	:	Reply for this device or proxies only.
+ *		Alan Cox	:	Don't proxy across hardware types!
+ *		Jonathan Naylor :	Added support for NET/ROM.
+ *		Mike Shaver     :       RFC1122 checks.
+ *		Jonathan Naylor :	Only lookup the hardware address for
+ *					the correct hardware type.
+ *		Germano Caronni	:	Assorted subtle races.
+ *		Craig Schlenter :	Don't modify permanent entry
+ *					during arp_rcv.
+ *		Russ Nelson	:	Tidied up a few bits.
+ *		Alexey Kuznetsov:	Major changes to caching and behaviour,
+ *					eg intelligent arp probing and
+ *					generation
+ *					of host down events.
+ *		Alan Cox	:	Missing unlock in device events.
+ *		Eckes		:	ARP ioctl control errors.
+ *		Alexey Kuznetsov:	Arp free fix.
+ *		Manuel Rodriguez:	Gratuitous ARP.
+ *              Jonathan Layes  :       Added arpd support through kerneld
+ *                                      message queue (960314)
+ *		Mike Shaver	:	/proc/sys/net/ipv4/arp_* support
+ *		Mike McLagan    :	Routing by source
+ *		Stuart Cheshire	:	Metricom and grat arp fixes
+ *					*** FOR 2.1 clean this up ***
+ *		Lawrence V. Stefani: (08/12/96) Added FDDI support.
+ *		Alan Cox	:	Took the AP1000 nasty FDDI hack and
+ *					folded into the mainstream FDDI code.
+ *					Ack spit, Linus how did you allow that
+ *					one in...
+ *		Jes Sorensen	:	Make FDDI work again in 2.1.x and
+ *					clean up the APFDDI & gen. FDDI bits.
+ *		Alexey Kuznetsov:	new arp state machine;
+ *					now it is in net/core/neighbour.c.
+ *		Krzysztof Halasa:	Added Frame Relay ARP support.
+ *		Arnaldo C. Melo :	convert /proc/net/arp to seq_file
+ *		Shmulik Hen:		Split arp_send to arp_create and
+ *					arp_xmit so intermediate drivers like
+ *					bonding can change the skb before
+ *					sending (e.g. insert 8021q tag).
+ *		Harald Welte	:	convert to make use of jenkins hash
+ *		Jesper D. Brouer:       Proxy ARP PVLAN RFC 3069 support.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/kernel.h>
+#include <linux/capability.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/errno.h>
+#include <linux/hex.h>
+#include <linux/in.h>
+#include <linux/mm.h>
+#include <linux/inet.h>
+#include <linux/inetdevice.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/fddidevice.h>
+#include <linux/if_arp.h>
+#include <linux/skbuff.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/stat.h>
+#include <linux/init.h>
+#include <linux/net.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+#ifdef CONFIG_SYSCTL
+#include <linux/sysctl.h>
+#endif
+
+#include <net/net_namespace.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/route.h>
+#include <net/protocol.h>
+#include <net/tcp.h>
+#include <net/sock.h>
+#include <net/arp.h>
+#include <net/ax25.h>
+#include <net/dst_metadata.h>
+#include <net/ip_tunnels.h>
+
+#include <linux/uaccess.h>
+
+#include <linux/netfilter_arp.h>
+
+/*
+ *	Interface to generic neighbour cache.
+ */
+static u32 arp_hash(const void *pkey, const struct net_device *dev, __u32 *hash_rnd);
+static bool arp_key_eq(const struct neighbour *n, const void *pkey);
+static int arp_constructor(struct neighbour *neigh);
+static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb);
+static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb);
+static void parp_redo(struct sk_buff *skb);
+static int arp_is_multicast(const void *pkey);
+
+static const struct neigh_ops arp_generic_ops = {
+	.family =		AF_INET,
+	.solicit =		arp_solicit,
+	.error_report =		arp_error_report,
+	.output =		neigh_resolve_output,
+	.connected_output =	neigh_connected_output,
+};
+
+static const struct neigh_ops arp_hh_ops = {
+	.family =		AF_INET,
+	.solicit =		arp_solicit,
+	.error_report =		arp_error_report,
+	.output =		neigh_resolve_output,
+	.connected_output =	neigh_resolve_output,
+};
+
+static const struct neigh_ops arp_direct_ops = {
+	.family =		AF_INET,
+	.output =		neigh_direct_output,
+	.connected_output =	neigh_direct_output,
+};
+
+struct neigh_table arp_tbl = {
+	.family		= AF_INET,
+	.key_len	= 4,
+	.protocol	= cpu_to_be16(ETH_P_IP),
+	.hash		= arp_hash,
+	.key_eq		= arp_key_eq,
+	.constructor	= arp_constructor,
+	.proxy_redo	= parp_redo,
+	.is_multicast	= arp_is_multicast,
+	.id		= "arp_cache",
+	.parms		= {
+		.tbl			= &arp_tbl,
+		.reachable_time		= 30 * HZ,
+		.data	= {
+			[NEIGH_VAR_MCAST_PROBES] = 3,
+			[NEIGH_VAR_UCAST_PROBES] = 3,
+			[NEIGH_VAR_RETRANS_TIME] = 1 * HZ,
+			[NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
+			[NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
+			[NEIGH_VAR_INTERVAL_PROBE_TIME_MS] = 5 * HZ,
+			[NEIGH_VAR_GC_STALETIME] = 60 * HZ,
+			[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_DEFAULT,
+			[NEIGH_VAR_PROXY_QLEN] = 64,
+			[NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
+			[NEIGH_VAR_PROXY_DELAY]	= (8 * HZ) / 10,
+			[NEIGH_VAR_LOCKTIME] = 1 * HZ,
+		},
+	},
+	.gc_interval	= 30 * HZ,
+	.gc_thresh1	= 128,
+	.gc_thresh2	= 512,
+	.gc_thresh3	= 1024,
+};
+EXPORT_SYMBOL(arp_tbl);
+
+int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
+{
+	switch (dev->type) {
+	case ARPHRD_ETHER:
+	case ARPHRD_FDDI:
+	case ARPHRD_IEEE802:
+		ip_eth_mc_map(addr, haddr);
+		return 0;
+	case ARPHRD_INFINIBAND:
+		ip_ib_mc_map(addr, dev->broadcast, haddr);
+		return 0;
+	case ARPHRD_IPGRE:
+		ip_ipgre_mc_map(addr, dev->broadcast, haddr);
+		return 0;
+	default:
+		if (dir) {
+			memcpy(haddr, dev->broadcast, dev->addr_len);
+			return 0;
+		}
+	}
+	return -EINVAL;
+}
+
+
+static u32 arp_hash(const void *pkey,
+		    const struct net_device *dev,
+		    __u32 *hash_rnd)
+{
+	return arp_hashfn(pkey, dev, hash_rnd);
+}
+
+static bool arp_key_eq(const struct neighbour *neigh, const void *pkey)
+{
+	return neigh_key_eq32(neigh, pkey);
+}
+
+static int arp_constructor(struct neighbour *neigh)
+{
+	__be32 addr;
+	struct net_device *dev = neigh->dev;
+	struct in_device *in_dev;
+	struct neigh_parms *parms;
+	u32 inaddr_any = INADDR_ANY;
+
+	if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
+		memcpy(neigh->primary_key, &inaddr_any, arp_tbl.key_len);
+
+	addr = *(__be32 *)neigh->primary_key;
+	rcu_read_lock();
+	in_dev = __in_dev_get_rcu(dev);
+	if (!in_dev) {
+		rcu_read_unlock();
+		return -EINVAL;
+	}
+
+	neigh->type = inet_addr_type_dev_table(dev_net(dev), dev, addr);
+
+	parms = in_dev->arp_parms;
+	__neigh_parms_put(neigh->parms);
+	neigh->parms = neigh_parms_clone(parms);
+	rcu_read_unlock();
+
+	if (!dev->header_ops) {
+		neigh->nud_state = NUD_NOARP;
+		neigh->ops = &arp_direct_ops;
+		neigh->output = neigh_direct_output;
+	} else {
+		/* Good devices (checked by reading texts, but only Ethernet is
+		   tested)
+
+		   ARPHRD_ETHER: (ethernet, apfddi)
+		   ARPHRD_FDDI: (fddi)
+		   ARPHRD_IEEE802: (tr)
+		   ARPHRD_METRICOM: (strip)
+		   ARPHRD_ARCNET:
+		   etc. etc. etc.
+
+		   ARPHRD_IPDDP will also work, if author repairs it.
+		   I did not it, because this driver does not work even
+		   in old paradigm.
+		 */
+
+		if (neigh->type == RTN_MULTICAST) {
+			neigh->nud_state = NUD_NOARP;
+			arp_mc_map(addr, neigh->ha, dev, 1);
+		} else if (dev->flags & (IFF_NOARP | IFF_LOOPBACK)) {
+			neigh->nud_state = NUD_NOARP;
+			memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
+		} else if (neigh->type == RTN_BROADCAST ||
+			   (dev->flags & IFF_POINTOPOINT)) {
+			neigh->nud_state = NUD_NOARP;
+			memcpy(neigh->ha, dev->broadcast, dev->addr_len);
+		}
+
+		if (dev->header_ops->cache)
+			neigh->ops = &arp_hh_ops;
+		else
+			neigh->ops = &arp_generic_ops;
+
+		if (neigh->nud_state & NUD_VALID)
+			neigh->output = neigh->ops->connected_output;
+		else
+			neigh->output = neigh->ops->output;
+	}
+	return 0;
+}
+
+static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
+{
+	dst_link_failure(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_FAILED);
+}
+
+/* Create and send an arp packet. */
+static void arp_send_dst(int type, int ptype, __be32 dest_ip,
+			 struct net_device *dev, __be32 src_ip,
+			 const unsigned char *dest_hw,
+			 const unsigned char *src_hw,
+			 const unsigned char *target_hw,
+			 struct dst_entry *dst)
+{
+	struct sk_buff *skb;
+
+	/* arp on this interface. */
+	if (dev->flags & IFF_NOARP)
+		return;
+
+	skb = arp_create(type, ptype, dest_ip, dev, src_ip,
+			 dest_hw, src_hw, target_hw);
+	if (!skb)
+		return;
+
+	skb_dst_set(skb, dst_clone(dst));
+	arp_xmit(skb);
+}
+
+void arp_send(int type, int ptype, __be32 dest_ip,
+	      struct net_device *dev, __be32 src_ip,
+	      const unsigned char *dest_hw, const unsigned char *src_hw,
+	      const unsigned char *target_hw)
+{
+	arp_send_dst(type, ptype, dest_ip, dev, src_ip, dest_hw, src_hw,
+		     target_hw, NULL);
+}
+EXPORT_SYMBOL(arp_send);
+
+static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
+{
+	__be32 saddr = 0;
+	u8 dst_ha[MAX_ADDR_LEN], *dst_hw = NULL;
+	struct net_device *dev = neigh->dev;
+	__be32 target = *(__be32 *)neigh->primary_key;
+	int probes = atomic_read(&neigh->probes);
+	struct in_device *in_dev;
+	struct dst_entry *dst = NULL;
+
+	rcu_read_lock();
+	in_dev = __in_dev_get_rcu(dev);
+	if (!in_dev) {
+		rcu_read_unlock();
+		return;
+	}
+	switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
+	default:
+	case 0:		/* By default announce any local IP */
+		if (skb && inet_addr_type_dev_table(dev_net(dev), dev,
+					  ip_hdr(skb)->saddr) == RTN_LOCAL)
+			saddr = ip_hdr(skb)->saddr;
+		break;
+	case 1:		/* Restrict announcements of saddr in same subnet */
+		if (!skb)
+			break;
+		saddr = ip_hdr(skb)->saddr;
+		if (inet_addr_type_dev_table(dev_net(dev), dev,
+					     saddr) == RTN_LOCAL) {
+			/* saddr should be known to target */
+			if (inet_addr_onlink(in_dev, target, saddr))
+				break;
+		}
+		saddr = 0;
+		break;
+	case 2:		/* Avoid secondary IPs, get a primary/preferred one */
+		break;
+	}
+	rcu_read_unlock();
+
+	if (!saddr)
+		saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);
+
+	probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES);
+	if (probes < 0) {
+		if (!(READ_ONCE(neigh->nud_state) & NUD_VALID))
+			pr_debug("trying to ucast probe in NUD_INVALID\n");
+		neigh_ha_snapshot(dst_ha, neigh, dev);
+		dst_hw = dst_ha;
+	} else {
+		probes -= NEIGH_VAR(neigh->parms, APP_PROBES);
+		if (probes < 0) {
+			neigh_app_ns(neigh);
+			return;
+		}
+	}
+
+	if (skb && !(dev->priv_flags & IFF_XMIT_DST_RELEASE))
+		dst = skb_dst(skb);
+	arp_send_dst(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
+		     dst_hw, dev->dev_addr, NULL, dst);
+}
+
+static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
+{
+	struct net *net = dev_net(in_dev->dev);
+	int scope;
+
+	switch (IN_DEV_ARP_IGNORE(in_dev)) {
+	case 0:	/* Reply, the tip is already validated */
+		return 0;
+	case 1:	/* Reply only if tip is configured on the incoming interface */
+		sip = 0;
+		scope = RT_SCOPE_HOST;
+		break;
+	case 2:	/*
+		 * Reply only if tip is configured on the incoming interface
+		 * and is in same subnet as sip
+		 */
+		scope = RT_SCOPE_HOST;
+		break;
+	case 3:	/* Do not reply for scope host addresses */
+		sip = 0;
+		scope = RT_SCOPE_LINK;
+		in_dev = NULL;
+		break;
+	case 4:	/* Reserved */
+	case 5:
+	case 6:
+	case 7:
+		return 0;
+	case 8:	/* Do not reply */
+		return 1;
+	default:
+		return 0;
+	}
+	return !inet_confirm_addr(net, in_dev, sip, tip, scope);
+}
+
+static int arp_accept(struct in_device *in_dev, __be32 sip)
+{
+	struct net *net = dev_net(in_dev->dev);
+	int scope = RT_SCOPE_LINK;
+
+	switch (IN_DEV_ARP_ACCEPT(in_dev)) {
+	case 0: /* Don't create new entries from garp */
+		return 0;
+	case 1: /* Create new entries from garp */
+		return 1;
+	case 2: /* Create a neighbor in the arp table only if sip
+		 * is in the same subnet as an address configured
+		 * on the interface that received the garp message
+		 */
+		return !!inet_confirm_addr(net, in_dev, sip, 0, scope);
+	default:
+		return 0;
+	}
+}
+
+static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
+{
+	struct rtable *rt;
+	int flag = 0;
+	/*unsigned long now; */
+	struct net *net = dev_net(dev);
+
+	rt = ip_route_output(net, sip, tip, 0, l3mdev_master_ifindex_rcu(dev),
+			     RT_SCOPE_UNIVERSE);
+	if (IS_ERR(rt))
+		return 1;
+	if (rt->dst.dev != dev) {
+		__NET_INC_STATS(net, LINUX_MIB_ARPFILTER);
+		flag = 1;
+	}
+	ip_rt_put(rt);
+	return flag;
+}
+
+/*
+ * Check if we can use proxy ARP for this path
+ */
+static inline int arp_fwd_proxy(struct in_device *in_dev,
+				struct net_device *dev,	struct rtable *rt)
+{
+	struct in_device *out_dev;
+	int imi, omi = -1;
+
+	if (rt->dst.dev == dev)
+		return 0;
+
+	if (!IN_DEV_PROXY_ARP(in_dev))
+		return 0;
+	imi = IN_DEV_MEDIUM_ID(in_dev);
+	if (imi == 0)
+		return 1;
+	if (imi == -1)
+		return 0;
+
+	/* place to check for proxy_arp for routes */
+
+	out_dev = __in_dev_get_rcu(rt->dst.dev);
+	if (out_dev)
+		omi = IN_DEV_MEDIUM_ID(out_dev);
+
+	return omi != imi && omi != -1;
+}
+
+/*
+ * Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
+ *
+ * RFC3069 supports proxy arp replies back to the same interface.  This
+ * is done to support (ethernet) switch features, like RFC 3069, where
+ * the individual ports are not allowed to communicate with each
+ * other, BUT they are allowed to talk to the upstream router.  As
+ * described in RFC 3069, it is possible to allow these hosts to
+ * communicate through the upstream router, by proxy_arp'ing.
+ *
+ * RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
+ *
+ *  This technology is known by different names:
+ *    In RFC 3069 it is called VLAN Aggregation.
+ *    Cisco and Allied Telesyn call it Private VLAN.
+ *    Hewlett-Packard call it Source-Port filtering or port-isolation.
+ *    Ericsson call it MAC-Forced Forwarding (RFC Draft).
+ *
+ */
+static inline int arp_fwd_pvlan(struct in_device *in_dev,
+				struct net_device *dev,	struct rtable *rt,
+				__be32 sip, __be32 tip)
+{
+	/* Private VLAN is only concerned about the same ethernet segment */
+	if (rt->dst.dev != dev)
+		return 0;
+
+	/* Don't reply on self probes (often done by windowz boxes)*/
+	if (sip == tip)
+		return 0;
+
+	if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
+		return 1;
+	else
+		return 0;
+}
+
+/*
+ *	Interface to link layer: send routine and receive handler.
+ */
+
+/*
+ *	Create an arp packet. If dest_hw is not set, we create a broadcast
+ *	message.
+ */
+struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
+			   struct net_device *dev, __be32 src_ip,
+			   const unsigned char *dest_hw,
+			   const unsigned char *src_hw,
+			   const unsigned char *target_hw)
+{
+	struct sk_buff *skb;
+	struct arphdr *arp;
+	unsigned char *arp_ptr;
+	int hlen = LL_RESERVED_SPACE(dev);
+	int tlen = dev->needed_tailroom;
+
+	/*
+	 *	Allocate a buffer
+	 */
+
+	skb = alloc_skb(arp_hdr_len(dev) + hlen + tlen, GFP_ATOMIC);
+	if (!skb)
+		return NULL;
+
+	skb_reserve(skb, hlen);
+	skb_reset_network_header(skb);
+	skb_put(skb, arp_hdr_len(dev));
+	skb->dev = dev;
+	skb->protocol = htons(ETH_P_ARP);
+	if (!src_hw)
+		src_hw = dev->dev_addr;
+	if (!dest_hw)
+		dest_hw = dev->broadcast;
+
+	/* Fill the device header for the ARP frame.
+	 * Note: skb->head can be changed.
+	 */
+	if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
+		goto out;
+
+	arp = arp_hdr(skb);
+	/*
+	 * Fill out the arp protocol part.
+	 *
+	 * The arp hardware type should match the device type, except for FDDI,
+	 * which (according to RFC 1390) should always equal 1 (Ethernet).
+	 */
+	/*
+	 *	Exceptions everywhere. AX.25 uses the AX.25 PID value not the
+	 *	DIX code for the protocol. Make these device structure fields.
+	 */
+	switch (dev->type) {
+	default:
+		arp->ar_hrd = htons(dev->type);
+		arp->ar_pro = htons(ETH_P_IP);
+		break;
+
+#if IS_ENABLED(CONFIG_AX25)
+	case ARPHRD_AX25:
+		arp->ar_hrd = htons(ARPHRD_AX25);
+		arp->ar_pro = htons(AX25_P_IP);
+		break;
+
+#if IS_ENABLED(CONFIG_NETROM)
+	case ARPHRD_NETROM:
+		arp->ar_hrd = htons(ARPHRD_NETROM);
+		arp->ar_pro = htons(AX25_P_IP);
+		break;
+#endif
+#endif
+
+#if IS_ENABLED(CONFIG_FDDI)
+	case ARPHRD_FDDI:
+		arp->ar_hrd = htons(ARPHRD_ETHER);
+		arp->ar_pro = htons(ETH_P_IP);
+		break;
+#endif
+	}
+
+	arp->ar_hln = dev->addr_len;
+	arp->ar_pln = 4;
+	arp->ar_op = htons(type);
+
+	arp_ptr = (unsigned char *)(arp + 1);
+
+	memcpy(arp_ptr, src_hw, dev->addr_len);
+	arp_ptr += dev->addr_len;
+	memcpy(arp_ptr, &src_ip, 4);
+	arp_ptr += 4;
+
+	switch (dev->type) {
+#if IS_ENABLED(CONFIG_FIREWIRE_NET)
+	case ARPHRD_IEEE1394:
+		break;
+#endif
+	default:
+		if (target_hw)
+			memcpy(arp_ptr, target_hw, dev->addr_len);
+		else
+			memset(arp_ptr, 0, dev->addr_len);
+		arp_ptr += dev->addr_len;
+	}
+	memcpy(arp_ptr, &dest_ip, 4);
+
+	return skb;
+
+out:
+	kfree_skb(skb);
+	return NULL;
+}
+EXPORT_SYMBOL(arp_create);
+
+static int arp_xmit_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	return dev_queue_xmit(skb);
+}
+
+/*
+ *	Send an arp packet.
+ */
+void arp_xmit(struct sk_buff *skb)
+{
+	rcu_read_lock();
+	/* Send it off, maybe filter it using firewalling first.  */
+	NF_HOOK(NFPROTO_ARP, NF_ARP_OUT,
+		dev_net_rcu(skb->dev), NULL, skb, NULL, skb->dev,
+		arp_xmit_finish);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL(arp_xmit);
+
+static bool arp_is_garp(struct net *net, struct net_device *dev,
+			int *addr_type, __be16 ar_op,
+			__be32 sip, __be32 tip,
+			unsigned char *sha, unsigned char *tha)
+{
+	bool is_garp = tip == sip;
+
+	/* Gratuitous ARP _replies_ also require target hwaddr to be
+	 * the same as source.
+	 */
+	if (is_garp && ar_op == htons(ARPOP_REPLY))
+		is_garp =
+			/* IPv4 over IEEE 1394 doesn't provide target
+			 * hardware address field in its ARP payload.
+			 */
+			tha &&
+			!memcmp(tha, sha, dev->addr_len);
+
+	if (is_garp) {
+		*addr_type = inet_addr_type_dev_table(net, dev, sip);
+		if (*addr_type != RTN_UNICAST)
+			is_garp = false;
+	}
+	return is_garp;
+}
+
+/*
+ *	Process an arp request.
+ */
+
+static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	struct net_device *dev = skb->dev;
+	struct in_device *in_dev = __in_dev_get_rcu(dev);
+	struct arphdr *arp;
+	unsigned char *arp_ptr;
+	struct rtable *rt;
+	unsigned char *sha;
+	unsigned char *tha = NULL;
+	__be32 sip, tip;
+	u16 dev_type = dev->type;
+	int addr_type;
+	struct neighbour *n;
+	struct dst_entry *reply_dst = NULL;
+	bool is_garp = false;
+
+	/* arp_rcv below verifies the ARP header and verifies the device
+	 * is ARP'able.
+	 */
+
+	if (!in_dev)
+		goto out_free_skb;
+
+	arp = arp_hdr(skb);
+
+	switch (dev_type) {
+	default:
+		if (arp->ar_pro != htons(ETH_P_IP) ||
+		    htons(dev_type) != arp->ar_hrd)
+			goto out_free_skb;
+		break;
+	case ARPHRD_ETHER:
+	case ARPHRD_FDDI:
+	case ARPHRD_IEEE802:
+		/*
+		 * ETHERNET, and Fibre Channel (which are IEEE 802
+		 * devices, according to RFC 2625) devices will accept ARP
+		 * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
+		 * This is the case also of FDDI, where the RFC 1390 says that
+		 * FDDI devices should accept ARP hardware of (1) Ethernet,
+		 * however, to be more robust, we'll accept both 1 (Ethernet)
+		 * or 6 (IEEE 802.2)
+		 */
+		if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
+		     arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
+		    arp->ar_pro != htons(ETH_P_IP))
+			goto out_free_skb;
+		break;
+	case ARPHRD_AX25:
+		if (arp->ar_pro != htons(AX25_P_IP) ||
+		    arp->ar_hrd != htons(ARPHRD_AX25))
+			goto out_free_skb;
+		break;
+	case ARPHRD_NETROM:
+		if (arp->ar_pro != htons(AX25_P_IP) ||
+		    arp->ar_hrd != htons(ARPHRD_NETROM))
+			goto out_free_skb;
+		break;
+	}
+
+	/* Understand only these message types */
+
+	if (arp->ar_op != htons(ARPOP_REPLY) &&
+	    arp->ar_op != htons(ARPOP_REQUEST))
+		goto out_free_skb;
+
+/*
+ *	Extract fields
+ */
+	arp_ptr = (unsigned char *)(arp + 1);
+	sha	= arp_ptr;
+	arp_ptr += dev->addr_len;
+	memcpy(&sip, arp_ptr, 4);
+	arp_ptr += 4;
+	switch (dev_type) {
+#if IS_ENABLED(CONFIG_FIREWIRE_NET)
+	case ARPHRD_IEEE1394:
+		break;
+#endif
+	default:
+		tha = arp_ptr;
+		arp_ptr += dev->addr_len;
+	}
+	memcpy(&tip, arp_ptr, 4);
+/*
+ *	Check for bad requests for 127.x.x.x and requests for multicast
+ *	addresses.  If this is one such, delete it.
+ */
+	if (ipv4_is_multicast(tip) ||
+	    (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
+		goto out_free_skb;
+
+ /*
+  *	For some 802.11 wireless deployments (and possibly other networks),
+  *	there will be an ARP proxy and gratuitous ARP frames are attacks
+  *	and thus should not be accepted.
+  */
+	if (sip == tip && IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP))
+		goto out_free_skb;
+
+/*
+ *     Special case: We must set Frame Relay source Q.922 address
+ */
+	if (dev_type == ARPHRD_DLCI)
+		sha = dev->broadcast;
+
+/*
+ *  Process entry.  The idea here is we want to send a reply if it is a
+ *  request for us or if it is a request for someone else that we hold
+ *  a proxy for.  We want to add an entry to our cache if it is a reply
+ *  to us or if it is a request for our address.
+ *  (The assumption for this last is that if someone is requesting our
+ *  address, they are probably intending to talk to us, so it saves time
+ *  if we cache their address.  Their address is also probably not in
+ *  our cache, since ours is not in their cache.)
+ *
+ *  Putting this another way, we only care about replies if they are to
+ *  us, in which case we add them to the cache.  For requests, we care
+ *  about those for us and those for our proxies.  We reply to both,
+ *  and in the case of requests for us we add the requester to the arp
+ *  cache.
+ */
+
+	if (arp->ar_op == htons(ARPOP_REQUEST) && skb_metadata_dst(skb))
+		reply_dst = (struct dst_entry *)
+			    iptunnel_metadata_reply(skb_metadata_dst(skb),
+						    GFP_ATOMIC);
+
+	/* Special case: IPv4 duplicate address detection packet (RFC2131) */
+	if (sip == 0) {
+		if (arp->ar_op == htons(ARPOP_REQUEST) &&
+		    inet_addr_type_dev_table(net, dev, tip) == RTN_LOCAL &&
+		    !arp_ignore(in_dev, sip, tip))
+			arp_send_dst(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip,
+				     sha, dev->dev_addr, sha, reply_dst);
+		goto out_consume_skb;
+	}
+
+	if (arp->ar_op == htons(ARPOP_REQUEST) &&
+	    ip_route_input_noref(skb, tip, sip, 0, dev) == 0) {
+
+		rt = skb_rtable(skb);
+		addr_type = rt->rt_type;
+
+		if (addr_type == RTN_LOCAL) {
+			int dont_send;
+
+			dont_send = arp_ignore(in_dev, sip, tip);
+			if (!dont_send && IN_DEV_ARPFILTER(in_dev))
+				dont_send = arp_filter(sip, tip, dev);
+			if (!dont_send) {
+				n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
+				if (n) {
+					arp_send_dst(ARPOP_REPLY, ETH_P_ARP,
+						     sip, dev, tip, sha,
+						     dev->dev_addr, sha,
+						     reply_dst);
+					neigh_release(n);
+				}
+			}
+			goto out_consume_skb;
+		} else if (IN_DEV_FORWARD(in_dev)) {
+			if (addr_type == RTN_UNICAST  &&
+			    (arp_fwd_proxy(in_dev, dev, rt) ||
+			     arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
+			     (rt->dst.dev != dev &&
+			      pneigh_lookup(&arp_tbl, net, &tip, dev)))) {
+				n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
+				if (n)
+					neigh_release(n);
+
+				if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
+				    skb->pkt_type == PACKET_HOST ||
+				    NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) {
+					arp_send_dst(ARPOP_REPLY, ETH_P_ARP,
+						     sip, dev, tip, sha,
+						     dev->dev_addr, sha,
+						     reply_dst);
+				} else {
+					pneigh_enqueue(&arp_tbl,
+						       in_dev->arp_parms, skb);
+					goto out_free_dst;
+				}
+				goto out_consume_skb;
+			}
+		}
+	}
+
+	/* Update our ARP tables */
+
+	n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
+
+	addr_type = -1;
+	if (n || arp_accept(in_dev, sip)) {
+		is_garp = arp_is_garp(net, dev, &addr_type, arp->ar_op,
+				      sip, tip, sha, tha);
+	}
+
+	if (arp_accept(in_dev, sip)) {
+		/* Unsolicited ARP is not accepted by default.
+		   It is possible, that this option should be enabled for some
+		   devices (strip is candidate)
+		 */
+		if (!n &&
+		    (is_garp ||
+		     (arp->ar_op == htons(ARPOP_REPLY) &&
+		      (addr_type == RTN_UNICAST ||
+		       (addr_type < 0 &&
+			/* postpone calculation to as late as possible */
+			inet_addr_type_dev_table(net, dev, sip) ==
+				RTN_UNICAST)))))
+			n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
+	}
+
+	if (n) {
+		int state = NUD_REACHABLE;
+		int override;
+
+		/* If several different ARP replies follows back-to-back,
+		   use the FIRST one. It is possible, if several proxy
+		   agents are active. Taking the first reply prevents
+		   arp trashing and chooses the fastest router.
+		 */
+		override = time_after(jiffies,
+				      n->updated +
+				      NEIGH_VAR(n->parms, LOCKTIME)) ||
+			   is_garp;
+
+		/* Broadcast replies and request packets
+		   do not assert neighbour reachability.
+		 */
+		if (arp->ar_op != htons(ARPOP_REPLY) ||
+		    skb->pkt_type != PACKET_HOST)
+			state = NUD_STALE;
+		neigh_update(n, sha, state,
+			     override ? NEIGH_UPDATE_F_OVERRIDE : 0, 0);
+		neigh_release(n);
+	}
+
+out_consume_skb:
+	consume_skb(skb);
+
+out_free_dst:
+	dst_release(reply_dst);
+	return NET_RX_SUCCESS;
+
+out_free_skb:
+	kfree_skb(skb);
+	return NET_RX_DROP;
+}
+
+static void parp_redo(struct sk_buff *skb)
+{
+	arp_process(dev_net(skb->dev), NULL, skb);
+}
+
+static int arp_is_multicast(const void *pkey)
+{
+	return ipv4_is_multicast(*((__be32 *)pkey));
+}
+
+/*
+ *	Receive an arp request from the device layer.
+ */
+
+static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
+		   struct packet_type *pt, struct net_device *orig_dev)
+{
+	enum skb_drop_reason drop_reason;
+	const struct arphdr *arp;
+
+	/* do not tweak dropwatch on an ARP we will ignore */
+	if (dev->flags & IFF_NOARP ||
+	    skb->pkt_type == PACKET_OTHERHOST ||
+	    skb->pkt_type == PACKET_LOOPBACK)
+		goto consumeskb;
+
+	skb = skb_share_check(skb, GFP_ATOMIC);
+	if (!skb)
+		goto out_of_mem;
+
+	/* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
+	drop_reason = pskb_may_pull_reason(skb, arp_hdr_len(dev));
+	if (drop_reason != SKB_NOT_DROPPED_YET)
+		goto freeskb;
+
+	arp = arp_hdr(skb);
+	if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4) {
+		drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
+		goto freeskb;
+	}
+
+	memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
+
+	return NF_HOOK(NFPROTO_ARP, NF_ARP_IN,
+		       dev_net(dev), NULL, skb, dev, NULL,
+		       arp_process);
+
+consumeskb:
+	consume_skb(skb);
+	return NET_RX_SUCCESS;
+freeskb:
+	kfree_skb_reason(skb, drop_reason);
+out_of_mem:
+	return NET_RX_DROP;
+}
+
+/*
+ *	User level interface (ioctl)
+ */
+
+static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r,
+					      bool getarp)
+{
+	struct net_device *dev;
+
+	if (getarp)
+		dev = dev_get_by_name_rcu(net, r->arp_dev);
+	else
+		dev = __dev_get_by_name(net, r->arp_dev);
+	if (!dev)
+		return ERR_PTR(-ENODEV);
+
+	/* Mmmm... It is wrong... ARPHRD_NETROM == 0 */
+	if (!r->arp_ha.sa_family)
+		r->arp_ha.sa_family = dev->type;
+
+	if ((r->arp_flags & ATF_COM) && r->arp_ha.sa_family != dev->type)
+		return ERR_PTR(-EINVAL);
+
+	return dev;
+}
+
+static struct net_device *arp_req_dev(struct net *net, struct arpreq *r)
+{
+	struct net_device *dev;
+	struct rtable *rt;
+	__be32 ip;
+
+	if (r->arp_dev[0])
+		return arp_req_dev_by_name(net, r, false);
+
+	if (r->arp_flags & ATF_PUBL)
+		return NULL;
+
+	ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+
+	rt = ip_route_output(net, ip, 0, 0, 0, RT_SCOPE_LINK);
+	if (IS_ERR(rt))
+		return ERR_CAST(rt);
+
+	dev = rt->dst.dev;
+	ip_rt_put(rt);
+
+	if (!dev)
+		return ERR_PTR(-EINVAL);
+
+	return dev;
+}
+
+/*
+ *	Set (create) an ARP cache entry.
+ */
+
+static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
+{
+	if (!dev) {
+		IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
+		return 0;
+	}
+	if (__in_dev_get_rtnl_net(dev)) {
+		IN_DEV_CONF_SET(__in_dev_get_rtnl_net(dev), PROXY_ARP, on);
+		return 0;
+	}
+	return -ENXIO;
+}
+
+static int arp_req_set_public(struct net *net, struct arpreq *r,
+		struct net_device *dev)
+{
+	__be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
+
+	if (!dev && (r->arp_flags & ATF_COM)) {
+		dev = dev_getbyhwaddr(net, r->arp_ha.sa_family,
+				      r->arp_ha.sa_data);
+		if (!dev)
+			return -ENODEV;
+	}
+	if (mask) {
+		__be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+
+		return pneigh_create(&arp_tbl, net, &ip, dev, 0, 0, false);
+	}
+
+	return arp_req_set_proxy(net, dev, 1);
+}
+
+static int arp_req_set(struct net *net, struct arpreq *r)
+{
+	struct neighbour *neigh;
+	struct net_device *dev;
+	__be32 ip;
+	int err;
+
+	dev = arp_req_dev(net, r);
+	if (IS_ERR(dev))
+		return PTR_ERR(dev);
+
+	if (r->arp_flags & ATF_PUBL)
+		return arp_req_set_public(net, r, dev);
+
+	switch (dev->type) {
+#if IS_ENABLED(CONFIG_FDDI)
+	case ARPHRD_FDDI:
+		/*
+		 * According to RFC 1390, FDDI devices should accept ARP
+		 * hardware types of 1 (Ethernet).  However, to be more
+		 * robust, we'll accept hardware types of either 1 (Ethernet)
+		 * or 6 (IEEE 802.2).
+		 */
+		if (r->arp_ha.sa_family != ARPHRD_FDDI &&
+		    r->arp_ha.sa_family != ARPHRD_ETHER &&
+		    r->arp_ha.sa_family != ARPHRD_IEEE802)
+			return -EINVAL;
+		break;
+#endif
+	default:
+		if (r->arp_ha.sa_family != dev->type)
+			return -EINVAL;
+		break;
+	}
+
+	ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+
+	neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
+	err = PTR_ERR(neigh);
+	if (!IS_ERR(neigh)) {
+		unsigned int state = NUD_STALE;
+
+		if (r->arp_flags & ATF_PERM) {
+			r->arp_flags |= ATF_COM;
+			state = NUD_PERMANENT;
+		}
+
+		err = neigh_update(neigh, (r->arp_flags & ATF_COM) ?
+				   r->arp_ha.sa_data : NULL, state,
+				   NEIGH_UPDATE_F_OVERRIDE |
+				   NEIGH_UPDATE_F_ADMIN, 0);
+		neigh_release(neigh);
+	}
+	return err;
+}
+
+static unsigned int arp_state_to_flags(struct neighbour *neigh)
+{
+	if (neigh->nud_state&NUD_PERMANENT)
+		return ATF_PERM | ATF_COM;
+	else if (neigh->nud_state&NUD_VALID)
+		return ATF_COM;
+	else
+		return 0;
+}
+
+/*
+ *	Get an ARP cache entry.
+ */
+
+static int arp_req_get(struct net *net, struct arpreq *r)
+{
+	__be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
+	struct neighbour *neigh;
+	struct net_device *dev;
+
+	if (!r->arp_dev[0])
+		return -ENODEV;
+
+	dev = arp_req_dev_by_name(net, r, true);
+	if (IS_ERR(dev))
+		return PTR_ERR(dev);
+
+	neigh = neigh_lookup(&arp_tbl, &ip, dev);
+	if (!neigh)
+		return -ENXIO;
+
+	if (READ_ONCE(neigh->nud_state) & NUD_NOARP) {
+		neigh_release(neigh);
+		return -ENXIO;
+	}
+
+	read_lock_bh(&neigh->lock);
+	memcpy(r->arp_ha.sa_data, neigh->ha,
+	       min(dev->addr_len, sizeof(r->arp_ha.sa_data)));
+	r->arp_flags = arp_state_to_flags(neigh);
+	read_unlock_bh(&neigh->lock);
+
+	neigh_release(neigh);
+
+	r->arp_ha.sa_family = dev->type;
+	netdev_copy_name(dev, r->arp_dev);
+
+	return 0;
+}
+
+int arp_invalidate(struct net_device *dev, __be32 ip, bool force)
+{
+	struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
+	int err = -ENXIO;
+	struct neigh_table *tbl = &arp_tbl;
+
+	if (neigh) {
+		if ((READ_ONCE(neigh->nud_state) & NUD_VALID) && !force) {
+			neigh_release(neigh);
+			return 0;
+		}
+
+		if (READ_ONCE(neigh->nud_state) & ~NUD_NOARP)
+			err = neigh_update(neigh, NULL, NUD_FAILED,
+					   NEIGH_UPDATE_F_OVERRIDE|
+					   NEIGH_UPDATE_F_ADMIN, 0);
+		spin_lock_bh(&tbl->lock);
+		neigh_release(neigh);
+		neigh_remove_one(neigh);
+		spin_unlock_bh(&tbl->lock);
+	}
+
+	return err;
+}
+
+static int arp_req_delete_public(struct net *net, struct arpreq *r,
+		struct net_device *dev)
+{
+	__be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
+
+	if (mask) {
+		__be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+
+		return pneigh_delete(&arp_tbl, net, &ip, dev);
+	}
+
+	return arp_req_set_proxy(net, dev, 0);
+}
+
+static int arp_req_delete(struct net *net, struct arpreq *r)
+{
+	struct net_device *dev;
+	__be32 ip;
+
+	dev = arp_req_dev(net, r);
+	if (IS_ERR(dev))
+		return PTR_ERR(dev);
+
+	if (r->arp_flags & ATF_PUBL)
+		return arp_req_delete_public(net, r, dev);
+
+	ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+
+	return arp_invalidate(dev, ip, true);
+}
+
+/*
+ *	Handle an ARP layer I/O control request.
+ */
+
+int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
+{
+	struct arpreq r;
+	__be32 *netmask;
+	int err;
+
+	switch (cmd) {
+	case SIOCDARP:
+	case SIOCSARP:
+		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+			return -EPERM;
+		fallthrough;
+	case SIOCGARP:
+		err = copy_from_user(&r, arg, sizeof(struct arpreq));
+		if (err)
+			return -EFAULT;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (r.arp_pa.sa_family != AF_INET)
+		return -EPFNOSUPPORT;
+
+	if (!(r.arp_flags & ATF_PUBL) &&
+	    (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
+		return -EINVAL;
+
+	netmask = &((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr;
+	if (!(r.arp_flags & ATF_NETMASK))
+		*netmask = htonl(0xFFFFFFFFUL);
+	else if (*netmask && *netmask != htonl(0xFFFFFFFFUL))
+		return -EINVAL;
+
+	switch (cmd) {
+	case SIOCDARP:
+		rtnl_net_lock(net);
+		err = arp_req_delete(net, &r);
+		rtnl_net_unlock(net);
+		break;
+	case SIOCSARP:
+		rtnl_net_lock(net);
+		err = arp_req_set(net, &r);
+		rtnl_net_unlock(net);
+		break;
+	case SIOCGARP:
+		rcu_read_lock();
+		err = arp_req_get(net, &r);
+		rcu_read_unlock();
+
+		if (!err && copy_to_user(arg, &r, sizeof(r)))
+			err = -EFAULT;
+		break;
+	}
+
+	return err;
+}
+
+static int arp_netdev_event(struct notifier_block *this, unsigned long event,
+			    void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct netdev_notifier_change_info *change_info;
+	struct in_device *in_dev;
+	bool evict_nocarrier;
+
+	switch (event) {
+	case NETDEV_CHANGEADDR:
+		neigh_changeaddr(&arp_tbl, dev);
+		rt_cache_flush(dev_net(dev));
+		break;
+	case NETDEV_CHANGE:
+		change_info = ptr;
+		if (change_info->flags_changed & IFF_NOARP)
+			neigh_changeaddr(&arp_tbl, dev);
+
+		in_dev = __in_dev_get_rtnl(dev);
+		if (!in_dev)
+			evict_nocarrier = true;
+		else
+			evict_nocarrier = IN_DEV_ARP_EVICT_NOCARRIER(in_dev);
+
+		if (evict_nocarrier && !netif_carrier_ok(dev))
+			neigh_carrier_down(&arp_tbl, dev);
+		break;
+	default:
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block arp_netdev_notifier = {
+	.notifier_call = arp_netdev_event,
+};
+
+/* Note, that it is not on notifier chain.
+   It is necessary, that this routine was called after route cache will be
+   flushed.
+ */
+void arp_ifdown(struct net_device *dev)
+{
+	neigh_ifdown(&arp_tbl, dev);
+}
+
+
+/*
+ *	Called once on startup.
+ */
+
+static struct packet_type arp_packet_type __read_mostly = {
+	.type =	cpu_to_be16(ETH_P_ARP),
+	.func =	arp_rcv,
+};
+
+#ifdef CONFIG_PROC_FS
+#if IS_ENABLED(CONFIG_AX25)
+
+/*
+ *	ax25 -> ASCII conversion
+ */
+static void ax2asc2(ax25_address *a, char *buf)
+{
+	char c, *s;
+	int n;
+
+	for (n = 0, s = buf; n < 6; n++) {
+		c = (a->ax25_call[n] >> 1) & 0x7F;
+
+		if (c != ' ')
+			*s++ = c;
+	}
+
+	*s++ = '-';
+	n = (a->ax25_call[6] >> 1) & 0x0F;
+	if (n > 9) {
+		*s++ = '1';
+		n -= 10;
+	}
+
+	*s++ = n + '0';
+	*s++ = '\0';
+
+	if (*buf == '\0' || *buf == '-') {
+		buf[0] = '*';
+		buf[1] = '\0';
+	}
+}
+#endif /* CONFIG_AX25 */
+
+#define HBUFFERLEN 30
+
+static void arp_format_neigh_entry(struct seq_file *seq,
+				   struct neighbour *n)
+{
+	char hbuffer[HBUFFERLEN];
+	int k, j;
+	char tbuf[16];
+	struct net_device *dev = n->dev;
+	int hatype = dev->type;
+
+	read_lock(&n->lock);
+	/* Convert hardware address to XX:XX:XX:XX ... form. */
+#if IS_ENABLED(CONFIG_AX25)
+	if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
+		ax2asc2((ax25_address *)n->ha, hbuffer);
+	else {
+#endif
+	for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
+		hbuffer[k++] = hex_asc_hi(n->ha[j]);
+		hbuffer[k++] = hex_asc_lo(n->ha[j]);
+		hbuffer[k++] = ':';
+	}
+	if (k != 0)
+		--k;
+	hbuffer[k] = 0;
+#if IS_ENABLED(CONFIG_AX25)
+	}
+#endif
+	sprintf(tbuf, "%pI4", n->primary_key);
+	seq_printf(seq, "%-16s 0x%-10x0x%-10x%-17s     *        %s\n",
+		   tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
+	read_unlock(&n->lock);
+}
+
+static void arp_format_pneigh_entry(struct seq_file *seq,
+				    struct pneigh_entry *n)
+{
+	struct net_device *dev = n->dev;
+	int hatype = dev ? dev->type : 0;
+	char tbuf[16];
+
+	sprintf(tbuf, "%pI4", n->key);
+	seq_printf(seq, "%-16s 0x%-10x0x%-10x%s     *        %s\n",
+		   tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
+		   dev ? dev->name : "*");
+}
+
+static int arp_seq_show(struct seq_file *seq, void *v)
+{
+	if (v == SEQ_START_TOKEN) {
+		seq_puts(seq, "IP address       HW type     Flags       "
+			      "HW address            Mask     Device\n");
+	} else {
+		struct neigh_seq_state *state = seq->private;
+
+		if (state->flags & NEIGH_SEQ_IS_PNEIGH)
+			arp_format_pneigh_entry(seq, v);
+		else
+			arp_format_neigh_entry(seq, v);
+	}
+
+	return 0;
+}
+
+static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	/* Don't want to confuse "arp -a" w/ magic entries,
+	 * so we tell the generic iterator to skip NUD_NOARP.
+	 */
+	return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
+}
+
+static const struct seq_operations arp_seq_ops = {
+	.start	= arp_seq_start,
+	.next	= neigh_seq_next,
+	.stop	= neigh_seq_stop,
+	.show	= arp_seq_show,
+};
+#endif /* CONFIG_PROC_FS */
+
+static int __net_init arp_net_init(struct net *net)
+{
+	if (!proc_create_net("arp", 0444, net->proc_net, &arp_seq_ops,
+			sizeof(struct neigh_seq_state)))
+		return -ENOMEM;
+	return 0;
+}
+
+static void __net_exit arp_net_exit(struct net *net)
+{
+	remove_proc_entry("arp", net->proc_net);
+}
+
+static struct pernet_operations arp_net_ops = {
+	.init = arp_net_init,
+	.exit = arp_net_exit,
+};
+
+void __init arp_init(void)
+{
+	neigh_table_init(NEIGH_ARP_TABLE, &arp_tbl);
+
+	dev_add_pack(&arp_packet_type);
+	register_pernet_subsys(&arp_net_ops);
+#ifdef CONFIG_SYSCTL
+	neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
+#endif
+	register_netdevice_notifier(&arp_netdev_notifier);
+}