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 struct neigh_table arp_tbl = {
156 .constructor = arp_constructor,
157 .proxy_redo = parp_redo,
161 .reachable_time = 30 * HZ,
163 [NEIGH_VAR_MCAST_PROBES] = 3,
164 [NEIGH_VAR_UCAST_PROBES] = 3,
165 [NEIGH_VAR_RETRANS_TIME] = 1 * HZ,
166 [NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
167 [NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
168 [NEIGH_VAR_GC_STALETIME] = 60 * HZ,
169 [NEIGH_VAR_QUEUE_LEN_BYTES] = 64 * 1024,
170 [NEIGH_VAR_PROXY_QLEN] = 64,
171 [NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
172 [NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,
173 [NEIGH_VAR_LOCKTIME] = 1 * HZ,
176 .gc_interval = 30 * HZ,
181 EXPORT_SYMBOL(arp_tbl);
183 int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
189 ip_eth_mc_map(addr, haddr);
191 case ARPHRD_INFINIBAND:
192 ip_ib_mc_map(addr, dev->broadcast, haddr);
195 ip_ipgre_mc_map(addr, dev->broadcast, haddr);
199 memcpy(haddr, dev->broadcast, dev->addr_len);
207 static u32 arp_hash(const void *pkey,
208 const struct net_device *dev,
211 return arp_hashfn(*(u32 *)pkey, dev, *hash_rnd);
214 static int arp_constructor(struct neighbour *neigh)
216 __be32 addr = *(__be32 *)neigh->primary_key;
217 struct net_device *dev = neigh->dev;
218 struct in_device *in_dev;
219 struct neigh_parms *parms;
222 in_dev = __in_dev_get_rcu(dev);
223 if (in_dev == NULL) {
228 neigh->type = inet_addr_type(dev_net(dev), addr);
230 parms = in_dev->arp_parms;
231 __neigh_parms_put(neigh->parms);
232 neigh->parms = neigh_parms_clone(parms);
235 if (!dev->header_ops) {
236 neigh->nud_state = NUD_NOARP;
237 neigh->ops = &arp_direct_ops;
238 neigh->output = neigh_direct_output;
240 /* Good devices (checked by reading texts, but only Ethernet is
243 ARPHRD_ETHER: (ethernet, apfddi)
246 ARPHRD_METRICOM: (strip)
250 ARPHRD_IPDDP will also work, if author repairs it.
251 I did not it, because this driver does not work even
255 if (neigh->type == RTN_MULTICAST) {
256 neigh->nud_state = NUD_NOARP;
257 arp_mc_map(addr, neigh->ha, dev, 1);
258 } else if (dev->flags & (IFF_NOARP | IFF_LOOPBACK)) {
259 neigh->nud_state = NUD_NOARP;
260 memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
261 } else if (neigh->type == RTN_BROADCAST ||
262 (dev->flags & IFF_POINTOPOINT)) {
263 neigh->nud_state = NUD_NOARP;
264 memcpy(neigh->ha, dev->broadcast, dev->addr_len);
267 if (dev->header_ops->cache)
268 neigh->ops = &arp_hh_ops;
270 neigh->ops = &arp_generic_ops;
272 if (neigh->nud_state & NUD_VALID)
273 neigh->output = neigh->ops->connected_output;
275 neigh->output = neigh->ops->output;
280 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
282 dst_link_failure(skb);
286 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
289 u8 dst_ha[MAX_ADDR_LEN], *dst_hw = NULL;
290 struct net_device *dev = neigh->dev;
291 __be32 target = *(__be32 *)neigh->primary_key;
292 int probes = atomic_read(&neigh->probes);
293 struct in_device *in_dev;
296 in_dev = __in_dev_get_rcu(dev);
301 switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
303 case 0: /* By default announce any local IP */
304 if (skb && inet_addr_type(dev_net(dev),
305 ip_hdr(skb)->saddr) == RTN_LOCAL)
306 saddr = ip_hdr(skb)->saddr;
308 case 1: /* Restrict announcements of saddr in same subnet */
311 saddr = ip_hdr(skb)->saddr;
312 if (inet_addr_type(dev_net(dev), saddr) == RTN_LOCAL) {
313 /* saddr should be known to target */
314 if (inet_addr_onlink(in_dev, target, saddr))
319 case 2: /* Avoid secondary IPs, get a primary/preferred one */
325 saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);
327 probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES);
329 if (!(neigh->nud_state & NUD_VALID))
330 pr_debug("trying to ucast probe in NUD_INVALID\n");
331 neigh_ha_snapshot(dst_ha, neigh, dev);
334 probes -= NEIGH_VAR(neigh->parms, APP_PROBES);
341 arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
342 dst_hw, dev->dev_addr, NULL);
345 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
347 struct net *net = dev_net(in_dev->dev);
350 switch (IN_DEV_ARP_IGNORE(in_dev)) {
351 case 0: /* Reply, the tip is already validated */
353 case 1: /* Reply only if tip is configured on the incoming interface */
355 scope = RT_SCOPE_HOST;
358 * Reply only if tip is configured on the incoming interface
359 * and is in same subnet as sip
361 scope = RT_SCOPE_HOST;
363 case 3: /* Do not reply for scope host addresses */
365 scope = RT_SCOPE_LINK;
368 case 4: /* Reserved */
373 case 8: /* Do not reply */
378 return !inet_confirm_addr(net, in_dev, sip, tip, scope);
381 static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
385 /*unsigned long now; */
386 struct net *net = dev_net(dev);
388 rt = ip_route_output(net, sip, tip, 0, 0);
391 if (rt->dst.dev != dev) {
392 NET_INC_STATS_BH(net, LINUX_MIB_ARPFILTER);
399 /* OBSOLETE FUNCTIONS */
402 * Find an arp mapping in the cache. If not found, post a request.
404 * It is very UGLY routine: it DOES NOT use skb->dst->neighbour,
405 * even if it exists. It is supposed that skb->dev was mangled
406 * by a virtual device (eql, shaper). Nobody but broken devices
407 * is allowed to use this function, it is scheduled to be removed. --ANK
410 static int arp_set_predefined(int addr_hint, unsigned char *haddr,
411 __be32 paddr, struct net_device *dev)
415 pr_debug("arp called for own IP address\n");
416 memcpy(haddr, dev->dev_addr, dev->addr_len);
419 arp_mc_map(paddr, haddr, dev, 1);
422 memcpy(haddr, dev->broadcast, dev->addr_len);
429 int arp_find(unsigned char *haddr, struct sk_buff *skb)
431 struct net_device *dev = skb->dev;
436 pr_debug("arp_find is called with dst==NULL\n");
441 paddr = rt_nexthop(skb_rtable(skb), ip_hdr(skb)->daddr);
442 if (arp_set_predefined(inet_addr_type(dev_net(dev), paddr), haddr,
446 n = __neigh_lookup(&arp_tbl, &paddr, dev, 1);
450 if (n->nud_state & NUD_VALID || neigh_event_send(n, skb) == 0) {
451 neigh_ha_snapshot(haddr, n, dev);
460 EXPORT_SYMBOL(arp_find);
462 /* END OF OBSOLETE FUNCTIONS */
465 * Check if we can use proxy ARP for this path
467 static inline int arp_fwd_proxy(struct in_device *in_dev,
468 struct net_device *dev, struct rtable *rt)
470 struct in_device *out_dev;
473 if (rt->dst.dev == dev)
476 if (!IN_DEV_PROXY_ARP(in_dev))
478 imi = IN_DEV_MEDIUM_ID(in_dev);
484 /* place to check for proxy_arp for routes */
486 out_dev = __in_dev_get_rcu(rt->dst.dev);
488 omi = IN_DEV_MEDIUM_ID(out_dev);
490 return omi != imi && omi != -1;
494 * Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
496 * RFC3069 supports proxy arp replies back to the same interface. This
497 * is done to support (ethernet) switch features, like RFC 3069, where
498 * the individual ports are not allowed to communicate with each
499 * other, BUT they are allowed to talk to the upstream router. As
500 * described in RFC 3069, it is possible to allow these hosts to
501 * communicate through the upstream router, by proxy_arp'ing.
503 * RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
505 * This technology is known by different names:
506 * In RFC 3069 it is called VLAN Aggregation.
507 * Cisco and Allied Telesyn call it Private VLAN.
508 * Hewlett-Packard call it Source-Port filtering or port-isolation.
509 * Ericsson call it MAC-Forced Forwarding (RFC Draft).
512 static inline int arp_fwd_pvlan(struct in_device *in_dev,
513 struct net_device *dev, struct rtable *rt,
514 __be32 sip, __be32 tip)
516 /* Private VLAN is only concerned about the same ethernet segment */
517 if (rt->dst.dev != dev)
520 /* Don't reply on self probes (often done by windowz boxes)*/
524 if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
531 * Interface to link layer: send routine and receive handler.
535 * Create an arp packet. If (dest_hw == NULL), we create a broadcast
538 struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
539 struct net_device *dev, __be32 src_ip,
540 const unsigned char *dest_hw,
541 const unsigned char *src_hw,
542 const unsigned char *target_hw)
546 unsigned char *arp_ptr;
547 int hlen = LL_RESERVED_SPACE(dev);
548 int tlen = dev->needed_tailroom;
554 skb = alloc_skb(arp_hdr_len(dev) + hlen + tlen, GFP_ATOMIC);
558 skb_reserve(skb, hlen);
559 skb_reset_network_header(skb);
560 arp = (struct arphdr *) skb_put(skb, arp_hdr_len(dev));
562 skb->protocol = htons(ETH_P_ARP);
564 src_hw = dev->dev_addr;
566 dest_hw = dev->broadcast;
569 * Fill the device header for the ARP frame
571 if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
575 * Fill out the arp protocol part.
577 * The arp hardware type should match the device type, except for FDDI,
578 * which (according to RFC 1390) should always equal 1 (Ethernet).
581 * Exceptions everywhere. AX.25 uses the AX.25 PID value not the
582 * DIX code for the protocol. Make these device structure fields.
586 arp->ar_hrd = htons(dev->type);
587 arp->ar_pro = htons(ETH_P_IP);
590 #if IS_ENABLED(CONFIG_AX25)
592 arp->ar_hrd = htons(ARPHRD_AX25);
593 arp->ar_pro = htons(AX25_P_IP);
596 #if IS_ENABLED(CONFIG_NETROM)
598 arp->ar_hrd = htons(ARPHRD_NETROM);
599 arp->ar_pro = htons(AX25_P_IP);
604 #if IS_ENABLED(CONFIG_FDDI)
606 arp->ar_hrd = htons(ARPHRD_ETHER);
607 arp->ar_pro = htons(ETH_P_IP);
612 arp->ar_hln = dev->addr_len;
614 arp->ar_op = htons(type);
616 arp_ptr = (unsigned char *)(arp + 1);
618 memcpy(arp_ptr, src_hw, dev->addr_len);
619 arp_ptr += dev->addr_len;
620 memcpy(arp_ptr, &src_ip, 4);
624 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
625 case ARPHRD_IEEE1394:
629 if (target_hw != NULL)
630 memcpy(arp_ptr, target_hw, dev->addr_len);
632 memset(arp_ptr, 0, dev->addr_len);
633 arp_ptr += dev->addr_len;
635 memcpy(arp_ptr, &dest_ip, 4);
643 EXPORT_SYMBOL(arp_create);
646 * Send an arp packet.
648 void arp_xmit(struct sk_buff *skb)
650 /* Send it off, maybe filter it using firewalling first. */
651 NF_HOOK(NFPROTO_ARP, NF_ARP_OUT, skb, NULL, skb->dev, dev_queue_xmit);
653 EXPORT_SYMBOL(arp_xmit);
656 * Create and send an arp packet.
658 void arp_send(int type, int ptype, __be32 dest_ip,
659 struct net_device *dev, __be32 src_ip,
660 const unsigned char *dest_hw, const unsigned char *src_hw,
661 const unsigned char *target_hw)
666 * No arp on this interface.
669 if (dev->flags&IFF_NOARP)
672 skb = arp_create(type, ptype, dest_ip, dev, src_ip,
673 dest_hw, src_hw, target_hw);
679 EXPORT_SYMBOL(arp_send);
682 * Process an arp request.
685 static int arp_process(struct sk_buff *skb)
687 struct net_device *dev = skb->dev;
688 struct in_device *in_dev = __in_dev_get_rcu(dev);
690 unsigned char *arp_ptr;
694 u16 dev_type = dev->type;
697 struct net *net = dev_net(dev);
698 bool is_garp = false;
700 /* arp_rcv below verifies the ARP header and verifies the device
711 if (arp->ar_pro != htons(ETH_P_IP) ||
712 htons(dev_type) != arp->ar_hrd)
719 * ETHERNET, and Fibre Channel (which are IEEE 802
720 * devices, according to RFC 2625) devices will accept ARP
721 * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
722 * This is the case also of FDDI, where the RFC 1390 says that
723 * FDDI devices should accept ARP hardware of (1) Ethernet,
724 * however, to be more robust, we'll accept both 1 (Ethernet)
727 if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
728 arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
729 arp->ar_pro != htons(ETH_P_IP))
733 if (arp->ar_pro != htons(AX25_P_IP) ||
734 arp->ar_hrd != htons(ARPHRD_AX25))
738 if (arp->ar_pro != htons(AX25_P_IP) ||
739 arp->ar_hrd != htons(ARPHRD_NETROM))
744 /* Understand only these message types */
746 if (arp->ar_op != htons(ARPOP_REPLY) &&
747 arp->ar_op != htons(ARPOP_REQUEST))
753 arp_ptr = (unsigned char *)(arp + 1);
755 arp_ptr += dev->addr_len;
756 memcpy(&sip, arp_ptr, 4);
759 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
760 case ARPHRD_IEEE1394:
764 arp_ptr += dev->addr_len;
766 memcpy(&tip, arp_ptr, 4);
768 * Check for bad requests for 127.x.x.x and requests for multicast
769 * addresses. If this is one such, delete it.
771 if (ipv4_is_multicast(tip) ||
772 (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
776 * Special case: We must set Frame Relay source Q.922 address
778 if (dev_type == ARPHRD_DLCI)
779 sha = dev->broadcast;
782 * Process entry. The idea here is we want to send a reply if it is a
783 * request for us or if it is a request for someone else that we hold
784 * a proxy for. We want to add an entry to our cache if it is a reply
785 * to us or if it is a request for our address.
786 * (The assumption for this last is that if someone is requesting our
787 * address, they are probably intending to talk to us, so it saves time
788 * if we cache their address. Their address is also probably not in
789 * our cache, since ours is not in their cache.)
791 * Putting this another way, we only care about replies if they are to
792 * us, in which case we add them to the cache. For requests, we care
793 * about those for us and those for our proxies. We reply to both,
794 * and in the case of requests for us we add the requester to the arp
798 /* Special case: IPv4 duplicate address detection packet (RFC2131) */
800 if (arp->ar_op == htons(ARPOP_REQUEST) &&
801 inet_addr_type(net, tip) == RTN_LOCAL &&
802 !arp_ignore(in_dev, sip, tip))
803 arp_send(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,
808 if (arp->ar_op == htons(ARPOP_REQUEST) &&
809 ip_route_input_noref(skb, tip, sip, 0, dev) == 0) {
811 rt = skb_rtable(skb);
812 addr_type = rt->rt_type;
814 if (addr_type == RTN_LOCAL) {
817 dont_send = arp_ignore(in_dev, sip, tip);
818 if (!dont_send && IN_DEV_ARPFILTER(in_dev))
819 dont_send = arp_filter(sip, tip, dev);
821 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
823 arp_send(ARPOP_REPLY, ETH_P_ARP, sip,
824 dev, tip, sha, dev->dev_addr,
830 } else if (IN_DEV_FORWARD(in_dev)) {
831 if (addr_type == RTN_UNICAST &&
832 (arp_fwd_proxy(in_dev, dev, rt) ||
833 arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
834 (rt->dst.dev != dev &&
835 pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) {
836 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
840 if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
841 skb->pkt_type == PACKET_HOST ||
842 NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) {
843 arp_send(ARPOP_REPLY, ETH_P_ARP, sip,
844 dev, tip, sha, dev->dev_addr,
847 pneigh_enqueue(&arp_tbl,
848 in_dev->arp_parms, skb);
856 /* Update our ARP tables */
858 n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
860 if (IN_DEV_ARP_ACCEPT(in_dev)) {
861 /* Unsolicited ARP is not accepted by default.
862 It is possible, that this option should be enabled for some
863 devices (strip is candidate)
865 is_garp = arp->ar_op == htons(ARPOP_REQUEST) && tip == sip &&
866 inet_addr_type(net, sip) == RTN_UNICAST;
869 ((arp->ar_op == htons(ARPOP_REPLY) &&
870 inet_addr_type(net, sip) == RTN_UNICAST) || is_garp))
871 n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
875 int state = NUD_REACHABLE;
878 /* If several different ARP replies follows back-to-back,
879 use the FIRST one. It is possible, if several proxy
880 agents are active. Taking the first reply prevents
881 arp trashing and chooses the fastest router.
883 override = time_after(jiffies,
885 NEIGH_VAR(n->parms, LOCKTIME)) ||
888 /* Broadcast replies and request packets
889 do not assert neighbour reachability.
891 if (arp->ar_op != htons(ARPOP_REPLY) ||
892 skb->pkt_type != PACKET_HOST)
894 neigh_update(n, sha, state,
895 override ? NEIGH_UPDATE_F_OVERRIDE : 0);
904 static void parp_redo(struct sk_buff *skb)
911 * Receive an arp request from the device layer.
914 static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
915 struct packet_type *pt, struct net_device *orig_dev)
917 const struct arphdr *arp;
919 /* do not tweak dropwatch on an ARP we will ignore */
920 if (dev->flags & IFF_NOARP ||
921 skb->pkt_type == PACKET_OTHERHOST ||
922 skb->pkt_type == PACKET_LOOPBACK)
925 skb = skb_share_check(skb, GFP_ATOMIC);
929 /* ARP header, plus 2 device addresses, plus 2 IP addresses. */
930 if (!pskb_may_pull(skb, arp_hdr_len(dev)))
934 if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4)
937 memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
939 return NF_HOOK(NFPROTO_ARP, NF_ARP_IN, skb, dev, NULL, arp_process);
951 * User level interface (ioctl)
955 * Set (create) an ARP cache entry.
958 static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
961 IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
964 if (__in_dev_get_rtnl(dev)) {
965 IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
971 static int arp_req_set_public(struct net *net, struct arpreq *r,
972 struct net_device *dev)
974 __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
975 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
977 if (mask && mask != htonl(0xFFFFFFFF))
979 if (!dev && (r->arp_flags & ATF_COM)) {
980 dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
986 if (pneigh_lookup(&arp_tbl, net, &ip, dev, 1) == NULL)
991 return arp_req_set_proxy(net, dev, 1);
994 static int arp_req_set(struct net *net, struct arpreq *r,
995 struct net_device *dev)
998 struct neighbour *neigh;
1001 if (r->arp_flags & ATF_PUBL)
1002 return arp_req_set_public(net, r, dev);
1004 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1005 if (r->arp_flags & ATF_PERM)
1006 r->arp_flags |= ATF_COM;
1008 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1017 switch (dev->type) {
1018 #if IS_ENABLED(CONFIG_FDDI)
1021 * According to RFC 1390, FDDI devices should accept ARP
1022 * hardware types of 1 (Ethernet). However, to be more
1023 * robust, we'll accept hardware types of either 1 (Ethernet)
1024 * or 6 (IEEE 802.2).
1026 if (r->arp_ha.sa_family != ARPHRD_FDDI &&
1027 r->arp_ha.sa_family != ARPHRD_ETHER &&
1028 r->arp_ha.sa_family != ARPHRD_IEEE802)
1033 if (r->arp_ha.sa_family != dev->type)
1038 neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
1039 err = PTR_ERR(neigh);
1040 if (!IS_ERR(neigh)) {
1041 unsigned int state = NUD_STALE;
1042 if (r->arp_flags & ATF_PERM)
1043 state = NUD_PERMANENT;
1044 err = neigh_update(neigh, (r->arp_flags & ATF_COM) ?
1045 r->arp_ha.sa_data : NULL, state,
1046 NEIGH_UPDATE_F_OVERRIDE |
1047 NEIGH_UPDATE_F_ADMIN);
1048 neigh_release(neigh);
1053 static unsigned int arp_state_to_flags(struct neighbour *neigh)
1055 if (neigh->nud_state&NUD_PERMANENT)
1056 return ATF_PERM | ATF_COM;
1057 else if (neigh->nud_state&NUD_VALID)
1064 * Get an ARP cache entry.
1067 static int arp_req_get(struct arpreq *r, struct net_device *dev)
1069 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1070 struct neighbour *neigh;
1073 neigh = neigh_lookup(&arp_tbl, &ip, dev);
1075 read_lock_bh(&neigh->lock);
1076 memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
1077 r->arp_flags = arp_state_to_flags(neigh);
1078 read_unlock_bh(&neigh->lock);
1079 r->arp_ha.sa_family = dev->type;
1080 strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
1081 neigh_release(neigh);
1087 static int arp_invalidate(struct net_device *dev, __be32 ip)
1089 struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
1093 if (neigh->nud_state & ~NUD_NOARP)
1094 err = neigh_update(neigh, NULL, NUD_FAILED,
1095 NEIGH_UPDATE_F_OVERRIDE|
1096 NEIGH_UPDATE_F_ADMIN);
1097 neigh_release(neigh);
1103 static int arp_req_delete_public(struct net *net, struct arpreq *r,
1104 struct net_device *dev)
1106 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1107 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1109 if (mask == htonl(0xFFFFFFFF))
1110 return pneigh_delete(&arp_tbl, net, &ip, dev);
1115 return arp_req_set_proxy(net, dev, 0);
1118 static int arp_req_delete(struct net *net, struct arpreq *r,
1119 struct net_device *dev)
1123 if (r->arp_flags & ATF_PUBL)
1124 return arp_req_delete_public(net, r, dev);
1126 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1128 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1136 return arp_invalidate(dev, ip);
1140 * Handle an ARP layer I/O control request.
1143 int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
1147 struct net_device *dev = NULL;
1152 if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
1155 err = copy_from_user(&r, arg, sizeof(struct arpreq));
1163 if (r.arp_pa.sa_family != AF_INET)
1164 return -EPFNOSUPPORT;
1166 if (!(r.arp_flags & ATF_PUBL) &&
1167 (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
1169 if (!(r.arp_flags & ATF_NETMASK))
1170 ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
1171 htonl(0xFFFFFFFFUL);
1175 dev = __dev_get_by_name(net, r.arp_dev);
1179 /* Mmmm... It is wrong... ARPHRD_NETROM==0 */
1180 if (!r.arp_ha.sa_family)
1181 r.arp_ha.sa_family = dev->type;
1183 if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
1185 } else if (cmd == SIOCGARP) {
1192 err = arp_req_delete(net, &r, dev);
1195 err = arp_req_set(net, &r, dev);
1198 err = arp_req_get(&r, dev);
1203 if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
1208 static int arp_netdev_event(struct notifier_block *this, unsigned long event,
1211 struct net_device *dev = netdev_notifier_info_to_dev(ptr);
1212 struct netdev_notifier_change_info *change_info;
1215 case NETDEV_CHANGEADDR:
1216 neigh_changeaddr(&arp_tbl, dev);
1217 rt_cache_flush(dev_net(dev));
1221 if (change_info->flags_changed & IFF_NOARP)
1222 neigh_changeaddr(&arp_tbl, dev);
1231 static struct notifier_block arp_netdev_notifier = {
1232 .notifier_call = arp_netdev_event,
1235 /* Note, that it is not on notifier chain.
1236 It is necessary, that this routine was called after route cache will be
1239 void arp_ifdown(struct net_device *dev)
1241 neigh_ifdown(&arp_tbl, dev);
1246 * Called once on startup.
1249 static struct packet_type arp_packet_type __read_mostly = {
1250 .type = cpu_to_be16(ETH_P_ARP),
1254 static int arp_proc_init(void);
1256 void __init arp_init(void)
1258 neigh_table_init(NEIGH_ARP_TABLE, &arp_tbl);
1260 dev_add_pack(&arp_packet_type);
1262 #ifdef CONFIG_SYSCTL
1263 neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
1265 register_netdevice_notifier(&arp_netdev_notifier);
1268 #ifdef CONFIG_PROC_FS
1269 #if IS_ENABLED(CONFIG_AX25)
1271 /* ------------------------------------------------------------------------ */
1273 * ax25 -> ASCII conversion
1275 static char *ax2asc2(ax25_address *a, char *buf)
1280 for (n = 0, s = buf; n < 6; n++) {
1281 c = (a->ax25_call[n] >> 1) & 0x7F;
1288 n = (a->ax25_call[6] >> 1) & 0x0F;
1297 if (*buf == '\0' || *buf == '-')
1302 #endif /* CONFIG_AX25 */
1304 #define HBUFFERLEN 30
1306 static void arp_format_neigh_entry(struct seq_file *seq,
1307 struct neighbour *n)
1309 char hbuffer[HBUFFERLEN];
1312 struct net_device *dev = n->dev;
1313 int hatype = dev->type;
1315 read_lock(&n->lock);
1316 /* Convert hardware address to XX:XX:XX:XX ... form. */
1317 #if IS_ENABLED(CONFIG_AX25)
1318 if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
1319 ax2asc2((ax25_address *)n->ha, hbuffer);
1322 for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
1323 hbuffer[k++] = hex_asc_hi(n->ha[j]);
1324 hbuffer[k++] = hex_asc_lo(n->ha[j]);
1330 #if IS_ENABLED(CONFIG_AX25)
1333 sprintf(tbuf, "%pI4", n->primary_key);
1334 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1335 tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
1336 read_unlock(&n->lock);
1339 static void arp_format_pneigh_entry(struct seq_file *seq,
1340 struct pneigh_entry *n)
1342 struct net_device *dev = n->dev;
1343 int hatype = dev ? dev->type : 0;
1346 sprintf(tbuf, "%pI4", n->key);
1347 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1348 tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
1349 dev ? dev->name : "*");
1352 static int arp_seq_show(struct seq_file *seq, void *v)
1354 if (v == SEQ_START_TOKEN) {
1355 seq_puts(seq, "IP address HW type Flags "
1356 "HW address Mask Device\n");
1358 struct neigh_seq_state *state = seq->private;
1360 if (state->flags & NEIGH_SEQ_IS_PNEIGH)
1361 arp_format_pneigh_entry(seq, v);
1363 arp_format_neigh_entry(seq, v);
1369 static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
1371 /* Don't want to confuse "arp -a" w/ magic entries,
1372 * so we tell the generic iterator to skip NUD_NOARP.
1374 return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
1377 /* ------------------------------------------------------------------------ */
1379 static const struct seq_operations arp_seq_ops = {
1380 .start = arp_seq_start,
1381 .next = neigh_seq_next,
1382 .stop = neigh_seq_stop,
1383 .show = arp_seq_show,
1386 static int arp_seq_open(struct inode *inode, struct file *file)
1388 return seq_open_net(inode, file, &arp_seq_ops,
1389 sizeof(struct neigh_seq_state));
1392 static const struct file_operations arp_seq_fops = {
1393 .owner = THIS_MODULE,
1394 .open = arp_seq_open,
1396 .llseek = seq_lseek,
1397 .release = seq_release_net,
1401 static int __net_init arp_net_init(struct net *net)
1403 if (!proc_create("arp", S_IRUGO, net->proc_net, &arp_seq_fops))
1408 static void __net_exit arp_net_exit(struct net *net)
1410 remove_proc_entry("arp", net->proc_net);
1413 static struct pernet_operations arp_net_ops = {
1414 .init = arp_net_init,
1415 .exit = arp_net_exit,
1418 static int __init arp_proc_init(void)
1420 return register_pernet_subsys(&arp_net_ops);
1423 #else /* CONFIG_PROC_FS */
1425 static int __init arp_proc_init(void)
1430 #endif /* CONFIG_PROC_FS */