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 int arp_constructor(struct neighbour *neigh);
126 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb);
127 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb);
128 static void parp_redo(struct sk_buff *skb);
130 static const struct neigh_ops arp_generic_ops = {
132 .solicit = arp_solicit,
133 .error_report = arp_error_report,
134 .output = neigh_resolve_output,
135 .connected_output = neigh_connected_output,
138 static const struct neigh_ops arp_hh_ops = {
140 .solicit = arp_solicit,
141 .error_report = arp_error_report,
142 .output = neigh_resolve_output,
143 .connected_output = neigh_resolve_output,
146 static const struct neigh_ops arp_direct_ops = {
148 .output = neigh_direct_output,
149 .connected_output = neigh_direct_output,
152 static const struct neigh_ops arp_broken_ops = {
154 .solicit = arp_solicit,
155 .error_report = arp_error_report,
156 .output = neigh_compat_output,
157 .connected_output = neigh_compat_output,
160 struct neigh_table arp_tbl = {
164 .constructor = arp_constructor,
165 .proxy_redo = parp_redo,
169 .reachable_time = 30 * HZ,
171 [NEIGH_VAR_MCAST_PROBES] = 3,
172 [NEIGH_VAR_UCAST_PROBES] = 3,
173 [NEIGH_VAR_RETRANS_TIME] = 1 * HZ,
174 [NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
175 [NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
176 [NEIGH_VAR_GC_STALETIME] = 60 * HZ,
177 [NEIGH_VAR_QUEUE_LEN_BYTES] = 64 * 1024,
178 [NEIGH_VAR_PROXY_QLEN] = 64,
179 [NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
180 [NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,
181 [NEIGH_VAR_LOCKTIME] = 1 * HZ,
184 .gc_interval = 30 * HZ,
189 EXPORT_SYMBOL(arp_tbl);
191 int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
197 ip_eth_mc_map(addr, haddr);
199 case ARPHRD_INFINIBAND:
200 ip_ib_mc_map(addr, dev->broadcast, haddr);
203 ip_ipgre_mc_map(addr, dev->broadcast, haddr);
207 memcpy(haddr, dev->broadcast, dev->addr_len);
215 static u32 arp_hash(const void *pkey,
216 const struct net_device *dev,
219 return arp_hashfn(*(u32 *)pkey, dev, *hash_rnd);
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);
231 if (in_dev == NULL) {
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
264 /* So... these "amateur" devices are hopeless.
265 The only thing, that I can say now:
266 It is very sad that we need to keep ugly obsolete
267 code to make them happy.
269 They should be moved to more reasonable state, now
270 they use rebuild_header INSTEAD OF hard_start_xmit!!!
271 Besides that, they are sort of out of date
272 (a lot of redundant clones/copies, useless in 2.1),
273 I wonder why people believe that they work.
279 #if IS_ENABLED(CONFIG_AX25)
281 #if IS_ENABLED(CONFIG_NETROM)
284 neigh->ops = &arp_broken_ops;
285 neigh->output = neigh->ops->output;
292 if (neigh->type == RTN_MULTICAST) {
293 neigh->nud_state = NUD_NOARP;
294 arp_mc_map(addr, neigh->ha, dev, 1);
295 } else if (dev->flags & (IFF_NOARP | IFF_LOOPBACK)) {
296 neigh->nud_state = NUD_NOARP;
297 memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
298 } else if (neigh->type == RTN_BROADCAST ||
299 (dev->flags & IFF_POINTOPOINT)) {
300 neigh->nud_state = NUD_NOARP;
301 memcpy(neigh->ha, dev->broadcast, dev->addr_len);
304 if (dev->header_ops->cache)
305 neigh->ops = &arp_hh_ops;
307 neigh->ops = &arp_generic_ops;
309 if (neigh->nud_state & NUD_VALID)
310 neigh->output = neigh->ops->connected_output;
312 neigh->output = neigh->ops->output;
317 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
319 dst_link_failure(skb);
323 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
326 u8 dst_ha[MAX_ADDR_LEN], *dst_hw = NULL;
327 struct net_device *dev = neigh->dev;
328 __be32 target = *(__be32 *)neigh->primary_key;
329 int probes = atomic_read(&neigh->probes);
330 struct in_device *in_dev;
333 in_dev = __in_dev_get_rcu(dev);
338 switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
340 case 0: /* By default announce any local IP */
341 if (skb && inet_addr_type(dev_net(dev),
342 ip_hdr(skb)->saddr) == RTN_LOCAL)
343 saddr = ip_hdr(skb)->saddr;
345 case 1: /* Restrict announcements of saddr in same subnet */
348 saddr = ip_hdr(skb)->saddr;
349 if (inet_addr_type(dev_net(dev), saddr) == RTN_LOCAL) {
350 /* saddr should be known to target */
351 if (inet_addr_onlink(in_dev, target, saddr))
356 case 2: /* Avoid secondary IPs, get a primary/preferred one */
362 saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);
364 probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES);
366 if (!(neigh->nud_state & NUD_VALID))
367 pr_debug("trying to ucast probe in NUD_INVALID\n");
368 neigh_ha_snapshot(dst_ha, neigh, dev);
371 probes -= NEIGH_VAR(neigh->parms, APP_PROBES);
378 arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
379 dst_hw, dev->dev_addr, NULL);
382 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
386 switch (IN_DEV_ARP_IGNORE(in_dev)) {
387 case 0: /* Reply, the tip is already validated */
389 case 1: /* Reply only if tip is configured on the incoming interface */
391 scope = RT_SCOPE_HOST;
394 * Reply only if tip is configured on the incoming interface
395 * and is in same subnet as sip
397 scope = RT_SCOPE_HOST;
399 case 3: /* Do not reply for scope host addresses */
401 scope = RT_SCOPE_LINK;
403 case 4: /* Reserved */
408 case 8: /* Do not reply */
413 return !inet_confirm_addr(in_dev, sip, tip, scope);
416 static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
420 /*unsigned long now; */
421 struct net *net = dev_net(dev);
423 rt = ip_route_output(net, sip, tip, 0, 0);
426 if (rt->dst.dev != dev) {
427 NET_INC_STATS_BH(net, LINUX_MIB_ARPFILTER);
434 /* OBSOLETE FUNCTIONS */
437 * Find an arp mapping in the cache. If not found, post a request.
439 * It is very UGLY routine: it DOES NOT use skb->dst->neighbour,
440 * even if it exists. It is supposed that skb->dev was mangled
441 * by a virtual device (eql, shaper). Nobody but broken devices
442 * is allowed to use this function, it is scheduled to be removed. --ANK
445 static int arp_set_predefined(int addr_hint, unsigned char *haddr,
446 __be32 paddr, struct net_device *dev)
450 pr_debug("arp called for own IP address\n");
451 memcpy(haddr, dev->dev_addr, dev->addr_len);
454 arp_mc_map(paddr, haddr, dev, 1);
457 memcpy(haddr, dev->broadcast, dev->addr_len);
464 int arp_find(unsigned char *haddr, struct sk_buff *skb)
466 struct net_device *dev = skb->dev;
471 pr_debug("arp_find is called with dst==NULL\n");
476 paddr = rt_nexthop(skb_rtable(skb), ip_hdr(skb)->daddr);
477 if (arp_set_predefined(inet_addr_type(dev_net(dev), paddr), haddr,
481 n = __neigh_lookup(&arp_tbl, &paddr, dev, 1);
485 if (n->nud_state & NUD_VALID || neigh_event_send(n, skb) == 0) {
486 neigh_ha_snapshot(haddr, n, dev);
495 EXPORT_SYMBOL(arp_find);
497 /* END OF OBSOLETE FUNCTIONS */
500 * Check if we can use proxy ARP for this path
502 static inline int arp_fwd_proxy(struct in_device *in_dev,
503 struct net_device *dev, struct rtable *rt)
505 struct in_device *out_dev;
508 if (rt->dst.dev == dev)
511 if (!IN_DEV_PROXY_ARP(in_dev))
513 imi = IN_DEV_MEDIUM_ID(in_dev);
519 /* place to check for proxy_arp for routes */
521 out_dev = __in_dev_get_rcu(rt->dst.dev);
523 omi = IN_DEV_MEDIUM_ID(out_dev);
525 return omi != imi && omi != -1;
529 * Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
531 * RFC3069 supports proxy arp replies back to the same interface. This
532 * is done to support (ethernet) switch features, like RFC 3069, where
533 * the individual ports are not allowed to communicate with each
534 * other, BUT they are allowed to talk to the upstream router. As
535 * described in RFC 3069, it is possible to allow these hosts to
536 * communicate through the upstream router, by proxy_arp'ing.
538 * RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
540 * This technology is known by different names:
541 * In RFC 3069 it is called VLAN Aggregation.
542 * Cisco and Allied Telesyn call it Private VLAN.
543 * Hewlett-Packard call it Source-Port filtering or port-isolation.
544 * Ericsson call it MAC-Forced Forwarding (RFC Draft).
547 static inline int arp_fwd_pvlan(struct in_device *in_dev,
548 struct net_device *dev, struct rtable *rt,
549 __be32 sip, __be32 tip)
551 /* Private VLAN is only concerned about the same ethernet segment */
552 if (rt->dst.dev != dev)
555 /* Don't reply on self probes (often done by windowz boxes)*/
559 if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
566 * Interface to link layer: send routine and receive handler.
570 * Create an arp packet. If (dest_hw == NULL), we create a broadcast
573 struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
574 struct net_device *dev, __be32 src_ip,
575 const unsigned char *dest_hw,
576 const unsigned char *src_hw,
577 const unsigned char *target_hw)
581 unsigned char *arp_ptr;
582 int hlen = LL_RESERVED_SPACE(dev);
583 int tlen = dev->needed_tailroom;
589 skb = alloc_skb(arp_hdr_len(dev) + hlen + tlen, GFP_ATOMIC);
593 skb_reserve(skb, hlen);
594 skb_reset_network_header(skb);
595 arp = (struct arphdr *) skb_put(skb, arp_hdr_len(dev));
597 skb->protocol = htons(ETH_P_ARP);
599 src_hw = dev->dev_addr;
601 dest_hw = dev->broadcast;
604 * Fill the device header for the ARP frame
606 if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
610 * Fill out the arp protocol part.
612 * The arp hardware type should match the device type, except for FDDI,
613 * which (according to RFC 1390) should always equal 1 (Ethernet).
616 * Exceptions everywhere. AX.25 uses the AX.25 PID value not the
617 * DIX code for the protocol. Make these device structure fields.
621 arp->ar_hrd = htons(dev->type);
622 arp->ar_pro = htons(ETH_P_IP);
625 #if IS_ENABLED(CONFIG_AX25)
627 arp->ar_hrd = htons(ARPHRD_AX25);
628 arp->ar_pro = htons(AX25_P_IP);
631 #if IS_ENABLED(CONFIG_NETROM)
633 arp->ar_hrd = htons(ARPHRD_NETROM);
634 arp->ar_pro = htons(AX25_P_IP);
639 #if IS_ENABLED(CONFIG_FDDI)
641 arp->ar_hrd = htons(ARPHRD_ETHER);
642 arp->ar_pro = htons(ETH_P_IP);
647 arp->ar_hln = dev->addr_len;
649 arp->ar_op = htons(type);
651 arp_ptr = (unsigned char *)(arp + 1);
653 memcpy(arp_ptr, src_hw, dev->addr_len);
654 arp_ptr += dev->addr_len;
655 memcpy(arp_ptr, &src_ip, 4);
659 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
660 case ARPHRD_IEEE1394:
664 if (target_hw != NULL)
665 memcpy(arp_ptr, target_hw, dev->addr_len);
667 memset(arp_ptr, 0, dev->addr_len);
668 arp_ptr += dev->addr_len;
670 memcpy(arp_ptr, &dest_ip, 4);
678 EXPORT_SYMBOL(arp_create);
681 * Send an arp packet.
683 void arp_xmit(struct sk_buff *skb)
685 /* Send it off, maybe filter it using firewalling first. */
686 NF_HOOK(NFPROTO_ARP, NF_ARP_OUT, skb, NULL, skb->dev, dev_queue_xmit);
688 EXPORT_SYMBOL(arp_xmit);
691 * Create and send an arp packet.
693 void arp_send(int type, int ptype, __be32 dest_ip,
694 struct net_device *dev, __be32 src_ip,
695 const unsigned char *dest_hw, const unsigned char *src_hw,
696 const unsigned char *target_hw)
701 * No arp on this interface.
704 if (dev->flags&IFF_NOARP)
707 skb = arp_create(type, ptype, dest_ip, dev, src_ip,
708 dest_hw, src_hw, target_hw);
714 EXPORT_SYMBOL(arp_send);
717 * Process an arp request.
720 static int arp_process(struct sk_buff *skb)
722 struct net_device *dev = skb->dev;
723 struct in_device *in_dev = __in_dev_get_rcu(dev);
725 unsigned char *arp_ptr;
729 u16 dev_type = dev->type;
732 struct net *net = dev_net(dev);
734 /* arp_rcv below verifies the ARP header and verifies the device
745 if (arp->ar_pro != htons(ETH_P_IP) ||
746 htons(dev_type) != arp->ar_hrd)
753 * ETHERNET, and Fibre Channel (which are IEEE 802
754 * devices, according to RFC 2625) devices will accept ARP
755 * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
756 * This is the case also of FDDI, where the RFC 1390 says that
757 * FDDI devices should accept ARP hardware of (1) Ethernet,
758 * however, to be more robust, we'll accept both 1 (Ethernet)
761 if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
762 arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
763 arp->ar_pro != htons(ETH_P_IP))
767 if (arp->ar_pro != htons(AX25_P_IP) ||
768 arp->ar_hrd != htons(ARPHRD_AX25))
772 if (arp->ar_pro != htons(AX25_P_IP) ||
773 arp->ar_hrd != htons(ARPHRD_NETROM))
778 /* Understand only these message types */
780 if (arp->ar_op != htons(ARPOP_REPLY) &&
781 arp->ar_op != htons(ARPOP_REQUEST))
787 arp_ptr = (unsigned char *)(arp + 1);
789 arp_ptr += dev->addr_len;
790 memcpy(&sip, arp_ptr, 4);
793 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
794 case ARPHRD_IEEE1394:
798 arp_ptr += dev->addr_len;
800 memcpy(&tip, arp_ptr, 4);
802 * Check for bad requests for 127.x.x.x and requests for multicast
803 * addresses. If this is one such, delete it.
805 if (ipv4_is_multicast(tip) ||
806 (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
810 * Special case: We must set Frame Relay source Q.922 address
812 if (dev_type == ARPHRD_DLCI)
813 sha = dev->broadcast;
816 * Process entry. The idea here is we want to send a reply if it is a
817 * request for us or if it is a request for someone else that we hold
818 * a proxy for. We want to add an entry to our cache if it is a reply
819 * to us or if it is a request for our address.
820 * (The assumption for this last is that if someone is requesting our
821 * address, they are probably intending to talk to us, so it saves time
822 * if we cache their address. Their address is also probably not in
823 * our cache, since ours is not in their cache.)
825 * Putting this another way, we only care about replies if they are to
826 * us, in which case we add them to the cache. For requests, we care
827 * about those for us and those for our proxies. We reply to both,
828 * and in the case of requests for us we add the requester to the arp
832 /* Special case: IPv4 duplicate address detection packet (RFC2131) */
834 if (arp->ar_op == htons(ARPOP_REQUEST) &&
835 inet_addr_type(net, tip) == RTN_LOCAL &&
836 !arp_ignore(in_dev, sip, tip))
837 arp_send(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,
842 if (arp->ar_op == htons(ARPOP_REQUEST) &&
843 ip_route_input_noref(skb, tip, sip, 0, dev) == 0) {
845 rt = skb_rtable(skb);
846 addr_type = rt->rt_type;
848 if (addr_type == RTN_LOCAL) {
851 dont_send = arp_ignore(in_dev, sip, tip);
852 if (!dont_send && IN_DEV_ARPFILTER(in_dev))
853 dont_send = arp_filter(sip, tip, dev);
855 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
857 arp_send(ARPOP_REPLY, ETH_P_ARP, sip,
858 dev, tip, sha, dev->dev_addr,
864 } else if (IN_DEV_FORWARD(in_dev)) {
865 if (addr_type == RTN_UNICAST &&
866 (arp_fwd_proxy(in_dev, dev, rt) ||
867 arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
868 (rt->dst.dev != dev &&
869 pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) {
870 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
874 if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
875 skb->pkt_type == PACKET_HOST ||
876 NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) {
877 arp_send(ARPOP_REPLY, ETH_P_ARP, sip,
878 dev, tip, sha, dev->dev_addr,
881 pneigh_enqueue(&arp_tbl,
882 in_dev->arp_parms, skb);
890 /* Update our ARP tables */
892 n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
894 if (IN_DEV_ARP_ACCEPT(in_dev)) {
895 /* Unsolicited ARP is not accepted by default.
896 It is possible, that this option should be enabled for some
897 devices (strip is candidate)
900 (arp->ar_op == htons(ARPOP_REPLY) ||
901 (arp->ar_op == htons(ARPOP_REQUEST) && tip == sip)) &&
902 inet_addr_type(net, sip) == RTN_UNICAST)
903 n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
907 int state = NUD_REACHABLE;
910 /* If several different ARP replies follows back-to-back,
911 use the FIRST one. It is possible, if several proxy
912 agents are active. Taking the first reply prevents
913 arp trashing and chooses the fastest router.
915 override = time_after(jiffies, n->updated +
916 NEIGH_VAR(n->parms, LOCKTIME));
918 /* Broadcast replies and request packets
919 do not assert neighbour reachability.
921 if (arp->ar_op != htons(ARPOP_REPLY) ||
922 skb->pkt_type != PACKET_HOST)
924 neigh_update(n, sha, state,
925 override ? NEIGH_UPDATE_F_OVERRIDE : 0);
934 static void parp_redo(struct sk_buff *skb)
941 * Receive an arp request from the device layer.
944 static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
945 struct packet_type *pt, struct net_device *orig_dev)
947 const struct arphdr *arp;
949 if (dev->flags & IFF_NOARP ||
950 skb->pkt_type == PACKET_OTHERHOST ||
951 skb->pkt_type == PACKET_LOOPBACK)
954 skb = skb_share_check(skb, GFP_ATOMIC);
958 /* ARP header, plus 2 device addresses, plus 2 IP addresses. */
959 if (!pskb_may_pull(skb, arp_hdr_len(dev)))
963 if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4)
966 memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
968 return NF_HOOK(NFPROTO_ARP, NF_ARP_IN, skb, dev, NULL, arp_process);
977 * User level interface (ioctl)
981 * Set (create) an ARP cache entry.
984 static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
987 IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
990 if (__in_dev_get_rtnl(dev)) {
991 IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
997 static int arp_req_set_public(struct net *net, struct arpreq *r,
998 struct net_device *dev)
1000 __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1001 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1003 if (mask && mask != htonl(0xFFFFFFFF))
1005 if (!dev && (r->arp_flags & ATF_COM)) {
1006 dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
1012 if (pneigh_lookup(&arp_tbl, net, &ip, dev, 1) == NULL)
1017 return arp_req_set_proxy(net, dev, 1);
1020 static int arp_req_set(struct net *net, struct arpreq *r,
1021 struct net_device *dev)
1024 struct neighbour *neigh;
1027 if (r->arp_flags & ATF_PUBL)
1028 return arp_req_set_public(net, r, dev);
1030 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1031 if (r->arp_flags & ATF_PERM)
1032 r->arp_flags |= ATF_COM;
1034 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1043 switch (dev->type) {
1044 #if IS_ENABLED(CONFIG_FDDI)
1047 * According to RFC 1390, FDDI devices should accept ARP
1048 * hardware types of 1 (Ethernet). However, to be more
1049 * robust, we'll accept hardware types of either 1 (Ethernet)
1050 * or 6 (IEEE 802.2).
1052 if (r->arp_ha.sa_family != ARPHRD_FDDI &&
1053 r->arp_ha.sa_family != ARPHRD_ETHER &&
1054 r->arp_ha.sa_family != ARPHRD_IEEE802)
1059 if (r->arp_ha.sa_family != dev->type)
1064 neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
1065 err = PTR_ERR(neigh);
1066 if (!IS_ERR(neigh)) {
1067 unsigned int state = NUD_STALE;
1068 if (r->arp_flags & ATF_PERM)
1069 state = NUD_PERMANENT;
1070 err = neigh_update(neigh, (r->arp_flags & ATF_COM) ?
1071 r->arp_ha.sa_data : NULL, state,
1072 NEIGH_UPDATE_F_OVERRIDE |
1073 NEIGH_UPDATE_F_ADMIN);
1074 neigh_release(neigh);
1079 static unsigned int arp_state_to_flags(struct neighbour *neigh)
1081 if (neigh->nud_state&NUD_PERMANENT)
1082 return ATF_PERM | ATF_COM;
1083 else if (neigh->nud_state&NUD_VALID)
1090 * Get an ARP cache entry.
1093 static int arp_req_get(struct arpreq *r, struct net_device *dev)
1095 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1096 struct neighbour *neigh;
1099 neigh = neigh_lookup(&arp_tbl, &ip, dev);
1101 read_lock_bh(&neigh->lock);
1102 memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
1103 r->arp_flags = arp_state_to_flags(neigh);
1104 read_unlock_bh(&neigh->lock);
1105 r->arp_ha.sa_family = dev->type;
1106 strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
1107 neigh_release(neigh);
1113 int arp_invalidate(struct net_device *dev, __be32 ip)
1115 struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
1119 if (neigh->nud_state & ~NUD_NOARP)
1120 err = neigh_update(neigh, NULL, NUD_FAILED,
1121 NEIGH_UPDATE_F_OVERRIDE|
1122 NEIGH_UPDATE_F_ADMIN);
1123 neigh_release(neigh);
1128 EXPORT_SYMBOL(arp_invalidate);
1130 static int arp_req_delete_public(struct net *net, struct arpreq *r,
1131 struct net_device *dev)
1133 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1134 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1136 if (mask == htonl(0xFFFFFFFF))
1137 return pneigh_delete(&arp_tbl, net, &ip, dev);
1142 return arp_req_set_proxy(net, dev, 0);
1145 static int arp_req_delete(struct net *net, struct arpreq *r,
1146 struct net_device *dev)
1150 if (r->arp_flags & ATF_PUBL)
1151 return arp_req_delete_public(net, r, dev);
1153 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1155 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1163 return arp_invalidate(dev, ip);
1167 * Handle an ARP layer I/O control request.
1170 int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
1174 struct net_device *dev = NULL;
1179 if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
1182 err = copy_from_user(&r, arg, sizeof(struct arpreq));
1190 if (r.arp_pa.sa_family != AF_INET)
1191 return -EPFNOSUPPORT;
1193 if (!(r.arp_flags & ATF_PUBL) &&
1194 (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
1196 if (!(r.arp_flags & ATF_NETMASK))
1197 ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
1198 htonl(0xFFFFFFFFUL);
1202 dev = __dev_get_by_name(net, r.arp_dev);
1206 /* Mmmm... It is wrong... ARPHRD_NETROM==0 */
1207 if (!r.arp_ha.sa_family)
1208 r.arp_ha.sa_family = dev->type;
1210 if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
1212 } else if (cmd == SIOCGARP) {
1219 err = arp_req_delete(net, &r, dev);
1222 err = arp_req_set(net, &r, dev);
1225 err = arp_req_get(&r, dev);
1230 if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
1235 static int arp_netdev_event(struct notifier_block *this, unsigned long event,
1238 struct net_device *dev = netdev_notifier_info_to_dev(ptr);
1239 struct netdev_notifier_change_info *change_info;
1242 case NETDEV_CHANGEADDR:
1243 neigh_changeaddr(&arp_tbl, dev);
1244 rt_cache_flush(dev_net(dev));
1248 if (change_info->flags_changed & IFF_NOARP)
1249 neigh_changeaddr(&arp_tbl, dev);
1258 static struct notifier_block arp_netdev_notifier = {
1259 .notifier_call = arp_netdev_event,
1262 /* Note, that it is not on notifier chain.
1263 It is necessary, that this routine was called after route cache will be
1266 void arp_ifdown(struct net_device *dev)
1268 neigh_ifdown(&arp_tbl, dev);
1273 * Called once on startup.
1276 static struct packet_type arp_packet_type __read_mostly = {
1277 .type = cpu_to_be16(ETH_P_ARP),
1281 static int arp_proc_init(void);
1283 void __init arp_init(void)
1285 neigh_table_init(&arp_tbl);
1287 dev_add_pack(&arp_packet_type);
1289 #ifdef CONFIG_SYSCTL
1290 neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
1292 register_netdevice_notifier(&arp_netdev_notifier);
1295 #ifdef CONFIG_PROC_FS
1296 #if IS_ENABLED(CONFIG_AX25)
1298 /* ------------------------------------------------------------------------ */
1300 * ax25 -> ASCII conversion
1302 static char *ax2asc2(ax25_address *a, char *buf)
1307 for (n = 0, s = buf; n < 6; n++) {
1308 c = (a->ax25_call[n] >> 1) & 0x7F;
1315 n = (a->ax25_call[6] >> 1) & 0x0F;
1324 if (*buf == '\0' || *buf == '-')
1329 #endif /* CONFIG_AX25 */
1331 #define HBUFFERLEN 30
1333 static void arp_format_neigh_entry(struct seq_file *seq,
1334 struct neighbour *n)
1336 char hbuffer[HBUFFERLEN];
1339 struct net_device *dev = n->dev;
1340 int hatype = dev->type;
1342 read_lock(&n->lock);
1343 /* Convert hardware address to XX:XX:XX:XX ... form. */
1344 #if IS_ENABLED(CONFIG_AX25)
1345 if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
1346 ax2asc2((ax25_address *)n->ha, hbuffer);
1349 for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
1350 hbuffer[k++] = hex_asc_hi(n->ha[j]);
1351 hbuffer[k++] = hex_asc_lo(n->ha[j]);
1357 #if IS_ENABLED(CONFIG_AX25)
1360 sprintf(tbuf, "%pI4", n->primary_key);
1361 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1362 tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
1363 read_unlock(&n->lock);
1366 static void arp_format_pneigh_entry(struct seq_file *seq,
1367 struct pneigh_entry *n)
1369 struct net_device *dev = n->dev;
1370 int hatype = dev ? dev->type : 0;
1373 sprintf(tbuf, "%pI4", n->key);
1374 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1375 tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
1376 dev ? dev->name : "*");
1379 static int arp_seq_show(struct seq_file *seq, void *v)
1381 if (v == SEQ_START_TOKEN) {
1382 seq_puts(seq, "IP address HW type Flags "
1383 "HW address Mask Device\n");
1385 struct neigh_seq_state *state = seq->private;
1387 if (state->flags & NEIGH_SEQ_IS_PNEIGH)
1388 arp_format_pneigh_entry(seq, v);
1390 arp_format_neigh_entry(seq, v);
1396 static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
1398 /* Don't want to confuse "arp -a" w/ magic entries,
1399 * so we tell the generic iterator to skip NUD_NOARP.
1401 return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
1404 /* ------------------------------------------------------------------------ */
1406 static const struct seq_operations arp_seq_ops = {
1407 .start = arp_seq_start,
1408 .next = neigh_seq_next,
1409 .stop = neigh_seq_stop,
1410 .show = arp_seq_show,
1413 static int arp_seq_open(struct inode *inode, struct file *file)
1415 return seq_open_net(inode, file, &arp_seq_ops,
1416 sizeof(struct neigh_seq_state));
1419 static const struct file_operations arp_seq_fops = {
1420 .owner = THIS_MODULE,
1421 .open = arp_seq_open,
1423 .llseek = seq_lseek,
1424 .release = seq_release_net,
1428 static int __net_init arp_net_init(struct net *net)
1430 if (!proc_create("arp", S_IRUGO, net->proc_net, &arp_seq_fops))
1435 static void __net_exit arp_net_exit(struct net *net)
1437 remove_proc_entry("arp", net->proc_net);
1440 static struct pernet_operations arp_net_ops = {
1441 .init = arp_net_init,
1442 .exit = arp_net_exit,
1445 static int __init arp_proc_init(void)
1447 return register_pernet_subsys(&arp_net_ops);
1450 #else /* CONFIG_PROC_FS */
1452 static int __init arp_proc_init(void)
1457 #endif /* CONFIG_PROC_FS */