1 /* linux/net/ipv4/arp.c
3 * Copyright (C) 1994 by Florian La Roche
5 * This module implements the Address Resolution Protocol ARP (RFC 826),
6 * which is used to convert IP addresses (or in the future maybe other
7 * high-level addresses) into a low-level hardware address (like an Ethernet
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * as published by the Free Software Foundation; either version
13 * 2 of the License, or (at your option) any later version.
16 * Alan Cox : Removed the Ethernet assumptions in
18 * Alan Cox : Fixed some small errors in the ARP
20 * Alan Cox : Allow >4K in /proc
21 * Alan Cox : Make ARP add its own protocol entry
22 * Ross Martin : Rewrote arp_rcv() and arp_get_info()
23 * Stephen Henson : Add AX25 support to arp_get_info()
24 * Alan Cox : Drop data when a device is downed.
25 * Alan Cox : Use init_timer().
26 * Alan Cox : Double lock fixes.
27 * Martin Seine : Move the arphdr structure
28 * to if_arp.h for compatibility.
29 * with BSD based programs.
30 * Andrew Tridgell : Added ARP netmask code and
31 * re-arranged proxy handling.
32 * Alan Cox : Changed to use notifiers.
33 * Niibe Yutaka : Reply for this device or proxies only.
34 * Alan Cox : Don't proxy across hardware types!
35 * Jonathan Naylor : Added support for NET/ROM.
36 * Mike Shaver : RFC1122 checks.
37 * Jonathan Naylor : Only lookup the hardware address for
38 * the correct hardware type.
39 * Germano Caronni : Assorted subtle races.
40 * Craig Schlenter : Don't modify permanent entry
42 * Russ Nelson : Tidied up a few bits.
43 * Alexey Kuznetsov: Major changes to caching and behaviour,
44 * eg intelligent arp probing and
46 * of host down events.
47 * Alan Cox : Missing unlock in device events.
48 * Eckes : ARP ioctl control errors.
49 * Alexey Kuznetsov: Arp free fix.
50 * Manuel Rodriguez: Gratuitous ARP.
51 * Jonathan Layes : Added arpd support through kerneld
52 * message queue (960314)
53 * Mike Shaver : /proc/sys/net/ipv4/arp_* support
54 * Mike McLagan : Routing by source
55 * Stuart Cheshire : Metricom and grat arp fixes
56 * *** FOR 2.1 clean this up ***
57 * Lawrence V. Stefani: (08/12/96) Added FDDI support.
58 * Alan Cox : Took the AP1000 nasty FDDI hack and
59 * folded into the mainstream FDDI code.
60 * Ack spit, Linus how did you allow that
62 * Jes Sorensen : Make FDDI work again in 2.1.x and
63 * clean up the APFDDI & gen. FDDI bits.
64 * Alexey Kuznetsov: new arp state machine;
65 * now it is in net/core/neighbour.c.
66 * Krzysztof Halasa: Added Frame Relay ARP support.
67 * Arnaldo C. Melo : convert /proc/net/arp to seq_file
68 * Shmulik Hen: Split arp_send to arp_create and
69 * arp_xmit so intermediate drivers like
70 * bonding can change the skb before
71 * sending (e.g. insert 8021q tag).
72 * Harald Welte : convert to make use of jenkins hash
73 * Jesper D. Brouer: Proxy ARP PVLAN RFC 3069 support.
76 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
78 #include <linux/module.h>
79 #include <linux/types.h>
80 #include <linux/string.h>
81 #include <linux/kernel.h>
82 #include <linux/capability.h>
83 #include <linux/socket.h>
84 #include <linux/sockios.h>
85 #include <linux/errno.h>
88 #include <linux/inet.h>
89 #include <linux/inetdevice.h>
90 #include <linux/netdevice.h>
91 #include <linux/etherdevice.h>
92 #include <linux/fddidevice.h>
93 #include <linux/if_arp.h>
94 #include <linux/skbuff.h>
95 #include <linux/proc_fs.h>
96 #include <linux/seq_file.h>
97 #include <linux/stat.h>
98 #include <linux/init.h>
99 #include <linux/net.h>
100 #include <linux/rcupdate.h>
101 #include <linux/slab.h>
103 #include <linux/sysctl.h>
106 #include <net/net_namespace.h>
108 #include <net/icmp.h>
109 #include <net/route.h>
110 #include <net/protocol.h>
112 #include <net/sock.h>
114 #include <net/ax25.h>
115 #include <net/netrom.h>
117 #include <linux/uaccess.h>
119 #include <linux/netfilter_arp.h>
122 * Interface to generic neighbour cache.
124 static u32 arp_hash(const void *pkey, const struct net_device *dev, __u32 *hash_rnd);
125 static bool arp_key_eq(const struct neighbour *n, const void *pkey);
126 static int arp_constructor(struct neighbour *neigh);
127 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb);
128 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb);
129 static void parp_redo(struct sk_buff *skb);
131 static const struct neigh_ops arp_generic_ops = {
133 .solicit = arp_solicit,
134 .error_report = arp_error_report,
135 .output = neigh_resolve_output,
136 .connected_output = neigh_connected_output,
139 static const struct neigh_ops arp_hh_ops = {
141 .solicit = arp_solicit,
142 .error_report = arp_error_report,
143 .output = neigh_resolve_output,
144 .connected_output = neigh_resolve_output,
147 static const struct neigh_ops arp_direct_ops = {
149 .output = neigh_direct_output,
150 .connected_output = neigh_direct_output,
153 struct neigh_table arp_tbl = {
156 .protocol = cpu_to_be16(ETH_P_IP),
158 .key_eq = arp_key_eq,
159 .constructor = arp_constructor,
160 .proxy_redo = parp_redo,
164 .reachable_time = 30 * HZ,
166 [NEIGH_VAR_MCAST_PROBES] = 3,
167 [NEIGH_VAR_UCAST_PROBES] = 3,
168 [NEIGH_VAR_RETRANS_TIME] = 1 * HZ,
169 [NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
170 [NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
171 [NEIGH_VAR_GC_STALETIME] = 60 * HZ,
172 [NEIGH_VAR_QUEUE_LEN_BYTES] = 64 * 1024,
173 [NEIGH_VAR_PROXY_QLEN] = 64,
174 [NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
175 [NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,
176 [NEIGH_VAR_LOCKTIME] = 1 * HZ,
179 .gc_interval = 30 * HZ,
184 EXPORT_SYMBOL(arp_tbl);
186 int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
192 ip_eth_mc_map(addr, haddr);
194 case ARPHRD_INFINIBAND:
195 ip_ib_mc_map(addr, dev->broadcast, haddr);
198 ip_ipgre_mc_map(addr, dev->broadcast, haddr);
202 memcpy(haddr, dev->broadcast, dev->addr_len);
210 static u32 arp_hash(const void *pkey,
211 const struct net_device *dev,
214 return arp_hashfn(pkey, dev, hash_rnd);
217 static bool arp_key_eq(const struct neighbour *neigh, const void *pkey)
219 return neigh_key_eq32(neigh, pkey);
222 static int arp_constructor(struct neighbour *neigh)
224 __be32 addr = *(__be32 *)neigh->primary_key;
225 struct net_device *dev = neigh->dev;
226 struct in_device *in_dev;
227 struct neigh_parms *parms;
230 in_dev = __in_dev_get_rcu(dev);
236 neigh->type = inet_addr_type(dev_net(dev), addr);
238 parms = in_dev->arp_parms;
239 __neigh_parms_put(neigh->parms);
240 neigh->parms = neigh_parms_clone(parms);
243 if (!dev->header_ops) {
244 neigh->nud_state = NUD_NOARP;
245 neigh->ops = &arp_direct_ops;
246 neigh->output = neigh_direct_output;
248 /* Good devices (checked by reading texts, but only Ethernet is
251 ARPHRD_ETHER: (ethernet, apfddi)
254 ARPHRD_METRICOM: (strip)
258 ARPHRD_IPDDP will also work, if author repairs it.
259 I did not it, because this driver does not work even
263 if (neigh->type == RTN_MULTICAST) {
264 neigh->nud_state = NUD_NOARP;
265 arp_mc_map(addr, neigh->ha, dev, 1);
266 } else if (dev->flags & (IFF_NOARP | IFF_LOOPBACK)) {
267 neigh->nud_state = NUD_NOARP;
268 memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
269 } else if (neigh->type == RTN_BROADCAST ||
270 (dev->flags & IFF_POINTOPOINT)) {
271 neigh->nud_state = NUD_NOARP;
272 memcpy(neigh->ha, dev->broadcast, dev->addr_len);
275 if (dev->header_ops->cache)
276 neigh->ops = &arp_hh_ops;
278 neigh->ops = &arp_generic_ops;
280 if (neigh->nud_state & NUD_VALID)
281 neigh->output = neigh->ops->connected_output;
283 neigh->output = neigh->ops->output;
288 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
290 dst_link_failure(skb);
294 /* Create and send an arp packet. */
295 static void arp_send_dst(int type, int ptype, __be32 dest_ip,
296 struct net_device *dev, __be32 src_ip,
297 const unsigned char *dest_hw,
298 const unsigned char *src_hw,
299 const unsigned char *target_hw, struct sk_buff *oskb)
303 /* arp on this interface. */
304 if (dev->flags & IFF_NOARP)
307 skb = arp_create(type, ptype, dest_ip, dev, src_ip,
308 dest_hw, src_hw, target_hw);
313 skb_dst_copy(skb, oskb);
318 void arp_send(int type, int ptype, __be32 dest_ip,
319 struct net_device *dev, __be32 src_ip,
320 const unsigned char *dest_hw, const unsigned char *src_hw,
321 const unsigned char *target_hw)
323 arp_send_dst(type, ptype, dest_ip, dev, src_ip, dest_hw, src_hw,
326 EXPORT_SYMBOL(arp_send);
328 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
331 u8 dst_ha[MAX_ADDR_LEN], *dst_hw = NULL;
332 struct net_device *dev = neigh->dev;
333 __be32 target = *(__be32 *)neigh->primary_key;
334 int probes = atomic_read(&neigh->probes);
335 struct in_device *in_dev;
338 in_dev = __in_dev_get_rcu(dev);
343 switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
345 case 0: /* By default announce any local IP */
346 if (skb && inet_addr_type(dev_net(dev),
347 ip_hdr(skb)->saddr) == RTN_LOCAL)
348 saddr = ip_hdr(skb)->saddr;
350 case 1: /* Restrict announcements of saddr in same subnet */
353 saddr = ip_hdr(skb)->saddr;
354 if (inet_addr_type(dev_net(dev), saddr) == RTN_LOCAL) {
355 /* saddr should be known to target */
356 if (inet_addr_onlink(in_dev, target, saddr))
361 case 2: /* Avoid secondary IPs, get a primary/preferred one */
367 saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);
369 probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES);
371 if (!(neigh->nud_state & NUD_VALID))
372 pr_debug("trying to ucast probe in NUD_INVALID\n");
373 neigh_ha_snapshot(dst_ha, neigh, dev);
376 probes -= NEIGH_VAR(neigh->parms, APP_PROBES);
383 arp_send_dst(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
384 dst_hw, dev->dev_addr, NULL,
385 dev->priv_flags & IFF_XMIT_DST_RELEASE ? NULL : skb);
388 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
390 struct net *net = dev_net(in_dev->dev);
393 switch (IN_DEV_ARP_IGNORE(in_dev)) {
394 case 0: /* Reply, the tip is already validated */
396 case 1: /* Reply only if tip is configured on the incoming interface */
398 scope = RT_SCOPE_HOST;
401 * Reply only if tip is configured on the incoming interface
402 * and is in same subnet as sip
404 scope = RT_SCOPE_HOST;
406 case 3: /* Do not reply for scope host addresses */
408 scope = RT_SCOPE_LINK;
411 case 4: /* Reserved */
416 case 8: /* Do not reply */
421 return !inet_confirm_addr(net, in_dev, sip, tip, scope);
424 static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
428 /*unsigned long now; */
429 struct net *net = dev_net(dev);
431 rt = ip_route_output(net, sip, tip, 0, 0);
434 if (rt->dst.dev != dev) {
435 NET_INC_STATS_BH(net, LINUX_MIB_ARPFILTER);
443 * Check if we can use proxy ARP for this path
445 static inline int arp_fwd_proxy(struct in_device *in_dev,
446 struct net_device *dev, struct rtable *rt)
448 struct in_device *out_dev;
451 if (rt->dst.dev == dev)
454 if (!IN_DEV_PROXY_ARP(in_dev))
456 imi = IN_DEV_MEDIUM_ID(in_dev);
462 /* place to check for proxy_arp for routes */
464 out_dev = __in_dev_get_rcu(rt->dst.dev);
466 omi = IN_DEV_MEDIUM_ID(out_dev);
468 return omi != imi && omi != -1;
472 * Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
474 * RFC3069 supports proxy arp replies back to the same interface. This
475 * is done to support (ethernet) switch features, like RFC 3069, where
476 * the individual ports are not allowed to communicate with each
477 * other, BUT they are allowed to talk to the upstream router. As
478 * described in RFC 3069, it is possible to allow these hosts to
479 * communicate through the upstream router, by proxy_arp'ing.
481 * RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
483 * This technology is known by different names:
484 * In RFC 3069 it is called VLAN Aggregation.
485 * Cisco and Allied Telesyn call it Private VLAN.
486 * Hewlett-Packard call it Source-Port filtering or port-isolation.
487 * Ericsson call it MAC-Forced Forwarding (RFC Draft).
490 static inline int arp_fwd_pvlan(struct in_device *in_dev,
491 struct net_device *dev, struct rtable *rt,
492 __be32 sip, __be32 tip)
494 /* Private VLAN is only concerned about the same ethernet segment */
495 if (rt->dst.dev != dev)
498 /* Don't reply on self probes (often done by windowz boxes)*/
502 if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
509 * Interface to link layer: send routine and receive handler.
513 * Create an arp packet. If dest_hw is not set, we create a broadcast
516 struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
517 struct net_device *dev, __be32 src_ip,
518 const unsigned char *dest_hw,
519 const unsigned char *src_hw,
520 const unsigned char *target_hw)
524 unsigned char *arp_ptr;
525 int hlen = LL_RESERVED_SPACE(dev);
526 int tlen = dev->needed_tailroom;
532 skb = alloc_skb(arp_hdr_len(dev) + hlen + tlen, GFP_ATOMIC);
536 skb_reserve(skb, hlen);
537 skb_reset_network_header(skb);
538 arp = (struct arphdr *) skb_put(skb, arp_hdr_len(dev));
540 skb->protocol = htons(ETH_P_ARP);
542 src_hw = dev->dev_addr;
544 dest_hw = dev->broadcast;
547 * Fill the device header for the ARP frame
549 if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
553 * Fill out the arp protocol part.
555 * The arp hardware type should match the device type, except for FDDI,
556 * which (according to RFC 1390) should always equal 1 (Ethernet).
559 * Exceptions everywhere. AX.25 uses the AX.25 PID value not the
560 * DIX code for the protocol. Make these device structure fields.
564 arp->ar_hrd = htons(dev->type);
565 arp->ar_pro = htons(ETH_P_IP);
568 #if IS_ENABLED(CONFIG_AX25)
570 arp->ar_hrd = htons(ARPHRD_AX25);
571 arp->ar_pro = htons(AX25_P_IP);
574 #if IS_ENABLED(CONFIG_NETROM)
576 arp->ar_hrd = htons(ARPHRD_NETROM);
577 arp->ar_pro = htons(AX25_P_IP);
582 #if IS_ENABLED(CONFIG_FDDI)
584 arp->ar_hrd = htons(ARPHRD_ETHER);
585 arp->ar_pro = htons(ETH_P_IP);
590 arp->ar_hln = dev->addr_len;
592 arp->ar_op = htons(type);
594 arp_ptr = (unsigned char *)(arp + 1);
596 memcpy(arp_ptr, src_hw, dev->addr_len);
597 arp_ptr += dev->addr_len;
598 memcpy(arp_ptr, &src_ip, 4);
602 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
603 case ARPHRD_IEEE1394:
608 memcpy(arp_ptr, target_hw, dev->addr_len);
610 memset(arp_ptr, 0, dev->addr_len);
611 arp_ptr += dev->addr_len;
613 memcpy(arp_ptr, &dest_ip, 4);
621 EXPORT_SYMBOL(arp_create);
624 * Send an arp packet.
626 void arp_xmit(struct sk_buff *skb)
628 /* Send it off, maybe filter it using firewalling first. */
629 NF_HOOK(NFPROTO_ARP, NF_ARP_OUT, NULL, skb,
630 NULL, skb->dev, dev_queue_xmit_sk);
632 EXPORT_SYMBOL(arp_xmit);
635 * Process an arp request.
638 static int arp_process(struct sock *sk, struct sk_buff *skb)
640 struct net_device *dev = skb->dev;
641 struct in_device *in_dev = __in_dev_get_rcu(dev);
643 unsigned char *arp_ptr;
647 u16 dev_type = dev->type;
650 struct net *net = dev_net(dev);
651 bool is_garp = false;
653 /* arp_rcv below verifies the ARP header and verifies the device
664 if (arp->ar_pro != htons(ETH_P_IP) ||
665 htons(dev_type) != arp->ar_hrd)
672 * ETHERNET, and Fibre Channel (which are IEEE 802
673 * devices, according to RFC 2625) devices will accept ARP
674 * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
675 * This is the case also of FDDI, where the RFC 1390 says that
676 * FDDI devices should accept ARP hardware of (1) Ethernet,
677 * however, to be more robust, we'll accept both 1 (Ethernet)
680 if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
681 arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
682 arp->ar_pro != htons(ETH_P_IP))
686 if (arp->ar_pro != htons(AX25_P_IP) ||
687 arp->ar_hrd != htons(ARPHRD_AX25))
691 if (arp->ar_pro != htons(AX25_P_IP) ||
692 arp->ar_hrd != htons(ARPHRD_NETROM))
697 /* Understand only these message types */
699 if (arp->ar_op != htons(ARPOP_REPLY) &&
700 arp->ar_op != htons(ARPOP_REQUEST))
706 arp_ptr = (unsigned char *)(arp + 1);
708 arp_ptr += dev->addr_len;
709 memcpy(&sip, arp_ptr, 4);
712 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
713 case ARPHRD_IEEE1394:
717 arp_ptr += dev->addr_len;
719 memcpy(&tip, arp_ptr, 4);
721 * Check for bad requests for 127.x.x.x and requests for multicast
722 * addresses. If this is one such, delete it.
724 if (ipv4_is_multicast(tip) ||
725 (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
729 * Special case: We must set Frame Relay source Q.922 address
731 if (dev_type == ARPHRD_DLCI)
732 sha = dev->broadcast;
735 * Process entry. The idea here is we want to send a reply if it is a
736 * request for us or if it is a request for someone else that we hold
737 * a proxy for. We want to add an entry to our cache if it is a reply
738 * to us or if it is a request for our address.
739 * (The assumption for this last is that if someone is requesting our
740 * address, they are probably intending to talk to us, so it saves time
741 * if we cache their address. Their address is also probably not in
742 * our cache, since ours is not in their cache.)
744 * Putting this another way, we only care about replies if they are to
745 * us, in which case we add them to the cache. For requests, we care
746 * about those for us and those for our proxies. We reply to both,
747 * and in the case of requests for us we add the requester to the arp
751 /* Special case: IPv4 duplicate address detection packet (RFC2131) */
753 if (arp->ar_op == htons(ARPOP_REQUEST) &&
754 inet_addr_type(net, tip) == RTN_LOCAL &&
755 !arp_ignore(in_dev, sip, tip))
756 arp_send(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,
761 if (arp->ar_op == htons(ARPOP_REQUEST) &&
762 ip_route_input_noref(skb, tip, sip, 0, dev) == 0) {
764 rt = skb_rtable(skb);
765 addr_type = rt->rt_type;
767 if (addr_type == RTN_LOCAL) {
770 dont_send = arp_ignore(in_dev, sip, tip);
771 if (!dont_send && IN_DEV_ARPFILTER(in_dev))
772 dont_send = arp_filter(sip, tip, dev);
774 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
776 arp_send(ARPOP_REPLY, ETH_P_ARP, sip,
777 dev, tip, sha, dev->dev_addr,
783 } else if (IN_DEV_FORWARD(in_dev)) {
784 if (addr_type == RTN_UNICAST &&
785 (arp_fwd_proxy(in_dev, dev, rt) ||
786 arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
787 (rt->dst.dev != dev &&
788 pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) {
789 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
793 if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
794 skb->pkt_type == PACKET_HOST ||
795 NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) {
796 arp_send(ARPOP_REPLY, ETH_P_ARP, sip,
797 dev, tip, sha, dev->dev_addr,
800 pneigh_enqueue(&arp_tbl,
801 in_dev->arp_parms, skb);
809 /* Update our ARP tables */
811 n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
813 if (IN_DEV_ARP_ACCEPT(in_dev)) {
814 /* Unsolicited ARP is not accepted by default.
815 It is possible, that this option should be enabled for some
816 devices (strip is candidate)
818 is_garp = arp->ar_op == htons(ARPOP_REQUEST) && tip == sip &&
819 inet_addr_type(net, sip) == RTN_UNICAST;
822 ((arp->ar_op == htons(ARPOP_REPLY) &&
823 inet_addr_type(net, sip) == RTN_UNICAST) || is_garp))
824 n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
828 int state = NUD_REACHABLE;
831 /* If several different ARP replies follows back-to-back,
832 use the FIRST one. It is possible, if several proxy
833 agents are active. Taking the first reply prevents
834 arp trashing and chooses the fastest router.
836 override = time_after(jiffies,
838 NEIGH_VAR(n->parms, LOCKTIME)) ||
841 /* Broadcast replies and request packets
842 do not assert neighbour reachability.
844 if (arp->ar_op != htons(ARPOP_REPLY) ||
845 skb->pkt_type != PACKET_HOST)
847 neigh_update(n, sha, state,
848 override ? NEIGH_UPDATE_F_OVERRIDE : 0);
857 static void parp_redo(struct sk_buff *skb)
859 arp_process(NULL, skb);
864 * Receive an arp request from the device layer.
867 static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
868 struct packet_type *pt, struct net_device *orig_dev)
870 const struct arphdr *arp;
872 /* do not tweak dropwatch on an ARP we will ignore */
873 if (dev->flags & IFF_NOARP ||
874 skb->pkt_type == PACKET_OTHERHOST ||
875 skb->pkt_type == PACKET_LOOPBACK)
878 skb = skb_share_check(skb, GFP_ATOMIC);
882 /* ARP header, plus 2 device addresses, plus 2 IP addresses. */
883 if (!pskb_may_pull(skb, arp_hdr_len(dev)))
887 if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4)
890 memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
892 return NF_HOOK(NFPROTO_ARP, NF_ARP_IN, NULL, skb,
893 dev, NULL, arp_process);
905 * User level interface (ioctl)
909 * Set (create) an ARP cache entry.
912 static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
915 IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
918 if (__in_dev_get_rtnl(dev)) {
919 IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
925 static int arp_req_set_public(struct net *net, struct arpreq *r,
926 struct net_device *dev)
928 __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
929 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
931 if (mask && mask != htonl(0xFFFFFFFF))
933 if (!dev && (r->arp_flags & ATF_COM)) {
934 dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
940 if (!pneigh_lookup(&arp_tbl, net, &ip, dev, 1))
945 return arp_req_set_proxy(net, dev, 1);
948 static int arp_req_set(struct net *net, struct arpreq *r,
949 struct net_device *dev)
952 struct neighbour *neigh;
955 if (r->arp_flags & ATF_PUBL)
956 return arp_req_set_public(net, r, dev);
958 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
959 if (r->arp_flags & ATF_PERM)
960 r->arp_flags |= ATF_COM;
962 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
972 #if IS_ENABLED(CONFIG_FDDI)
975 * According to RFC 1390, FDDI devices should accept ARP
976 * hardware types of 1 (Ethernet). However, to be more
977 * robust, we'll accept hardware types of either 1 (Ethernet)
980 if (r->arp_ha.sa_family != ARPHRD_FDDI &&
981 r->arp_ha.sa_family != ARPHRD_ETHER &&
982 r->arp_ha.sa_family != ARPHRD_IEEE802)
987 if (r->arp_ha.sa_family != dev->type)
992 neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
993 err = PTR_ERR(neigh);
994 if (!IS_ERR(neigh)) {
995 unsigned int state = NUD_STALE;
996 if (r->arp_flags & ATF_PERM)
997 state = NUD_PERMANENT;
998 err = neigh_update(neigh, (r->arp_flags & ATF_COM) ?
999 r->arp_ha.sa_data : NULL, state,
1000 NEIGH_UPDATE_F_OVERRIDE |
1001 NEIGH_UPDATE_F_ADMIN);
1002 neigh_release(neigh);
1007 static unsigned int arp_state_to_flags(struct neighbour *neigh)
1009 if (neigh->nud_state&NUD_PERMANENT)
1010 return ATF_PERM | ATF_COM;
1011 else if (neigh->nud_state&NUD_VALID)
1018 * Get an ARP cache entry.
1021 static int arp_req_get(struct arpreq *r, struct net_device *dev)
1023 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1024 struct neighbour *neigh;
1027 neigh = neigh_lookup(&arp_tbl, &ip, dev);
1029 read_lock_bh(&neigh->lock);
1030 memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
1031 r->arp_flags = arp_state_to_flags(neigh);
1032 read_unlock_bh(&neigh->lock);
1033 r->arp_ha.sa_family = dev->type;
1034 strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
1035 neigh_release(neigh);
1041 static int arp_invalidate(struct net_device *dev, __be32 ip)
1043 struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
1047 if (neigh->nud_state & ~NUD_NOARP)
1048 err = neigh_update(neigh, NULL, NUD_FAILED,
1049 NEIGH_UPDATE_F_OVERRIDE|
1050 NEIGH_UPDATE_F_ADMIN);
1051 neigh_release(neigh);
1057 static int arp_req_delete_public(struct net *net, struct arpreq *r,
1058 struct net_device *dev)
1060 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1061 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1063 if (mask == htonl(0xFFFFFFFF))
1064 return pneigh_delete(&arp_tbl, net, &ip, dev);
1069 return arp_req_set_proxy(net, dev, 0);
1072 static int arp_req_delete(struct net *net, struct arpreq *r,
1073 struct net_device *dev)
1077 if (r->arp_flags & ATF_PUBL)
1078 return arp_req_delete_public(net, r, dev);
1080 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1082 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1090 return arp_invalidate(dev, ip);
1094 * Handle an ARP layer I/O control request.
1097 int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
1101 struct net_device *dev = NULL;
1106 if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
1109 err = copy_from_user(&r, arg, sizeof(struct arpreq));
1117 if (r.arp_pa.sa_family != AF_INET)
1118 return -EPFNOSUPPORT;
1120 if (!(r.arp_flags & ATF_PUBL) &&
1121 (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
1123 if (!(r.arp_flags & ATF_NETMASK))
1124 ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
1125 htonl(0xFFFFFFFFUL);
1129 dev = __dev_get_by_name(net, r.arp_dev);
1133 /* Mmmm... It is wrong... ARPHRD_NETROM==0 */
1134 if (!r.arp_ha.sa_family)
1135 r.arp_ha.sa_family = dev->type;
1137 if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
1139 } else if (cmd == SIOCGARP) {
1146 err = arp_req_delete(net, &r, dev);
1149 err = arp_req_set(net, &r, dev);
1152 err = arp_req_get(&r, dev);
1157 if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
1162 static int arp_netdev_event(struct notifier_block *this, unsigned long event,
1165 struct net_device *dev = netdev_notifier_info_to_dev(ptr);
1166 struct netdev_notifier_change_info *change_info;
1169 case NETDEV_CHANGEADDR:
1170 neigh_changeaddr(&arp_tbl, dev);
1171 rt_cache_flush(dev_net(dev));
1175 if (change_info->flags_changed & IFF_NOARP)
1176 neigh_changeaddr(&arp_tbl, dev);
1185 static struct notifier_block arp_netdev_notifier = {
1186 .notifier_call = arp_netdev_event,
1189 /* Note, that it is not on notifier chain.
1190 It is necessary, that this routine was called after route cache will be
1193 void arp_ifdown(struct net_device *dev)
1195 neigh_ifdown(&arp_tbl, dev);
1200 * Called once on startup.
1203 static struct packet_type arp_packet_type __read_mostly = {
1204 .type = cpu_to_be16(ETH_P_ARP),
1208 static int arp_proc_init(void);
1210 void __init arp_init(void)
1212 neigh_table_init(NEIGH_ARP_TABLE, &arp_tbl);
1214 dev_add_pack(&arp_packet_type);
1216 #ifdef CONFIG_SYSCTL
1217 neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
1219 register_netdevice_notifier(&arp_netdev_notifier);
1222 #ifdef CONFIG_PROC_FS
1223 #if IS_ENABLED(CONFIG_AX25)
1225 /* ------------------------------------------------------------------------ */
1227 * ax25 -> ASCII conversion
1229 static char *ax2asc2(ax25_address *a, char *buf)
1234 for (n = 0, s = buf; n < 6; n++) {
1235 c = (a->ax25_call[n] >> 1) & 0x7F;
1242 n = (a->ax25_call[6] >> 1) & 0x0F;
1251 if (*buf == '\0' || *buf == '-')
1256 #endif /* CONFIG_AX25 */
1258 #define HBUFFERLEN 30
1260 static void arp_format_neigh_entry(struct seq_file *seq,
1261 struct neighbour *n)
1263 char hbuffer[HBUFFERLEN];
1266 struct net_device *dev = n->dev;
1267 int hatype = dev->type;
1269 read_lock(&n->lock);
1270 /* Convert hardware address to XX:XX:XX:XX ... form. */
1271 #if IS_ENABLED(CONFIG_AX25)
1272 if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
1273 ax2asc2((ax25_address *)n->ha, hbuffer);
1276 for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
1277 hbuffer[k++] = hex_asc_hi(n->ha[j]);
1278 hbuffer[k++] = hex_asc_lo(n->ha[j]);
1284 #if IS_ENABLED(CONFIG_AX25)
1287 sprintf(tbuf, "%pI4", n->primary_key);
1288 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1289 tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
1290 read_unlock(&n->lock);
1293 static void arp_format_pneigh_entry(struct seq_file *seq,
1294 struct pneigh_entry *n)
1296 struct net_device *dev = n->dev;
1297 int hatype = dev ? dev->type : 0;
1300 sprintf(tbuf, "%pI4", n->key);
1301 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1302 tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
1303 dev ? dev->name : "*");
1306 static int arp_seq_show(struct seq_file *seq, void *v)
1308 if (v == SEQ_START_TOKEN) {
1309 seq_puts(seq, "IP address HW type Flags "
1310 "HW address Mask Device\n");
1312 struct neigh_seq_state *state = seq->private;
1314 if (state->flags & NEIGH_SEQ_IS_PNEIGH)
1315 arp_format_pneigh_entry(seq, v);
1317 arp_format_neigh_entry(seq, v);
1323 static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
1325 /* Don't want to confuse "arp -a" w/ magic entries,
1326 * so we tell the generic iterator to skip NUD_NOARP.
1328 return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
1331 /* ------------------------------------------------------------------------ */
1333 static const struct seq_operations arp_seq_ops = {
1334 .start = arp_seq_start,
1335 .next = neigh_seq_next,
1336 .stop = neigh_seq_stop,
1337 .show = arp_seq_show,
1340 static int arp_seq_open(struct inode *inode, struct file *file)
1342 return seq_open_net(inode, file, &arp_seq_ops,
1343 sizeof(struct neigh_seq_state));
1346 static const struct file_operations arp_seq_fops = {
1347 .owner = THIS_MODULE,
1348 .open = arp_seq_open,
1350 .llseek = seq_lseek,
1351 .release = seq_release_net,
1355 static int __net_init arp_net_init(struct net *net)
1357 if (!proc_create("arp", S_IRUGO, net->proc_net, &arp_seq_fops))
1362 static void __net_exit arp_net_exit(struct net *net)
1364 remove_proc_entry("arp", net->proc_net);
1367 static struct pernet_operations arp_net_ops = {
1368 .init = arp_net_init,
1369 .exit = arp_net_exit,
1372 static int __init arp_proc_init(void)
1374 return register_pernet_subsys(&arp_net_ops);
1377 #else /* CONFIG_PROC_FS */
1379 static int __init arp_proc_init(void)
1384 #endif /* CONFIG_PROC_FS */