Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1472 insertions, 0 deletions

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
new file mode 100644
index 0000000000..9456f5bb35
--- /dev/null
+++ b/net/ipv4/arp.c
@@ -0,0 +1,1472 @@
+// 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/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/netrom.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_MAX,
+			[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));
+	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);
+	arp = 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
+	 */
+	if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
+		goto out;
+
+	/*
+	 * 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)
+{
+	/* Send it off, maybe filter it using firewalling first.  */
+	NF_HOOK(NFPROTO_ARP, NF_ARP_OUT,
+		dev_net(skb->dev), NULL, skb, NULL, skb->dev,
+		arp_xmit_finish);
+}
+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, 0)))) {
+				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)
+{
+	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.  */
+	if (!pskb_may_pull(skb, arp_hdr_len(dev)))
+		goto freeskb;
+
+	arp = arp_hdr(skb);
+	if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4)
+		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(skb);
+out_of_mem:
+	return NET_RX_DROP;
+}
+
+/*
+ *	User level interface (ioctl)
+ */
+
+/*
+ *	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(dev)) {
+		IN_DEV_CONF_SET(__in_dev_get_rtnl(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 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+	__be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
+
+	if (mask && mask != htonl(0xFFFFFFFF))
+		return -EINVAL;
+	if (!dev && (r->arp_flags & ATF_COM)) {
+		dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
+				      r->arp_ha.sa_data);
+		if (!dev)
+			return -ENODEV;
+	}
+	if (mask) {
+		if (!pneigh_lookup(&arp_tbl, net, &ip, dev, 1))
+			return -ENOBUFS;
+		return 0;
+	}
+
+	return arp_req_set_proxy(net, dev, 1);
+}
+
+static int arp_req_set(struct net *net, struct arpreq *r,
+		       struct net_device *dev)
+{
+	__be32 ip;
+	struct neighbour *neigh;
+	int err;
+
+	if (r->arp_flags & ATF_PUBL)
+		return arp_req_set_public(net, r, dev);
+
+	ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+	if (r->arp_flags & ATF_PERM)
+		r->arp_flags |= ATF_COM;
+	if (!dev) {
+		struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
+
+		if (IS_ERR(rt))
+			return PTR_ERR(rt);
+		dev = rt->dst.dev;
+		ip_rt_put(rt);
+		if (!dev)
+			return -EINVAL;
+	}
+	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;
+	}
+
+	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)
+			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 arpreq *r, struct net_device *dev)
+{
+	__be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
+	struct neighbour *neigh;
+	int err = -ENXIO;
+
+	neigh = neigh_lookup(&arp_tbl, &ip, dev);
+	if (neigh) {
+		if (!(READ_ONCE(neigh->nud_state) & NUD_NOARP)) {
+			read_lock_bh(&neigh->lock);
+			memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
+			r->arp_flags = arp_state_to_flags(neigh);
+			read_unlock_bh(&neigh->lock);
+			r->arp_ha.sa_family = dev->type;
+			strscpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
+			err = 0;
+		}
+		neigh_release(neigh);
+	}
+	return err;
+}
+
+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);
+		write_lock_bh(&tbl->lock);
+		neigh_release(neigh);
+		neigh_remove_one(neigh, tbl);
+		write_unlock_bh(&tbl->lock);
+	}
+
+	return err;
+}
+
+static int arp_req_delete_public(struct net *net, struct arpreq *r,
+		struct net_device *dev)
+{
+	__be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
+	__be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
+
+	if (mask == htonl(0xFFFFFFFF))
+		return pneigh_delete(&arp_tbl, net, &ip, dev);
+
+	if (mask)
+		return -EINVAL;
+
+	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;
+
+	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;
+	if (!dev) {
+		struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
+		if (IS_ERR(rt))
+			return PTR_ERR(rt);
+		dev = rt->dst.dev;
+		ip_rt_put(rt);
+		if (!dev)
+			return -EINVAL;
+	}
+	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)
+{
+	int err;
+	struct arpreq r;
+	struct net_device *dev = NULL;
+
+	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;
+	if (!(r.arp_flags & ATF_NETMASK))
+		((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
+							   htonl(0xFFFFFFFFUL);
+	rtnl_lock();
+	if (r.arp_dev[0]) {
+		err = -ENODEV;
+		dev = __dev_get_by_name(net, r.arp_dev);
+		if (!dev)
+			goto out;
+
+		/* Mmmm... It is wrong... ARPHRD_NETROM==0 */
+		if (!r.arp_ha.sa_family)
+			r.arp_ha.sa_family = dev->type;
+		err = -EINVAL;
+		if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
+			goto out;
+	} else if (cmd == SIOCGARP) {
+		err = -ENODEV;
+		goto out;
+	}
+
+	switch (cmd) {
+	case SIOCDARP:
+		err = arp_req_delete(net, &r, dev);
+		break;
+	case SIOCSARP:
+		err = arp_req_set(net, &r, dev);
+		break;
+	case SIOCGARP:
+		err = arp_req_get(&r, dev);
+		break;
+	}
+out:
+	rtnl_unlock();
+	if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
+		err = -EFAULT;
+	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);
+}