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>
116 #include <net/dst_metadata.h>
117 #include <net/ip_tunnels.h>
119 #include <linux/uaccess.h>
121 #include <linux/netfilter_arp.h>
124 * Interface to generic neighbour cache.
126 static u32 arp_hash(const void *pkey, const struct net_device *dev, __u32 *hash_rnd);
127 static bool arp_key_eq(const struct neighbour *n, const void *pkey);
128 static int arp_constructor(struct neighbour *neigh);
129 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb);
130 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb);
131 static void parp_redo(struct sk_buff *skb);
133 static const struct neigh_ops arp_generic_ops = {
135 .solicit = arp_solicit,
136 .error_report = arp_error_report,
137 .output = neigh_resolve_output,
138 .connected_output = neigh_connected_output,
141 static const struct neigh_ops arp_hh_ops = {
143 .solicit = arp_solicit,
144 .error_report = arp_error_report,
145 .output = neigh_resolve_output,
146 .connected_output = neigh_resolve_output,
149 static const struct neigh_ops arp_direct_ops = {
151 .output = neigh_direct_output,
152 .connected_output = neigh_direct_output,
155 struct neigh_table arp_tbl = {
158 .protocol = cpu_to_be16(ETH_P_IP),
160 .key_eq = arp_key_eq,
161 .constructor = arp_constructor,
162 .proxy_redo = parp_redo,
166 .reachable_time = 30 * HZ,
168 [NEIGH_VAR_MCAST_PROBES] = 3,
169 [NEIGH_VAR_UCAST_PROBES] = 3,
170 [NEIGH_VAR_RETRANS_TIME] = 1 * HZ,
171 [NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
172 [NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
173 [NEIGH_VAR_GC_STALETIME] = 60 * HZ,
174 [NEIGH_VAR_QUEUE_LEN_BYTES] = 64 * 1024,
175 [NEIGH_VAR_PROXY_QLEN] = 64,
176 [NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
177 [NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,
178 [NEIGH_VAR_LOCKTIME] = 1 * HZ,
181 .gc_interval = 30 * HZ,
186 EXPORT_SYMBOL(arp_tbl);
188 int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
194 ip_eth_mc_map(addr, haddr);
196 case ARPHRD_INFINIBAND:
197 ip_ib_mc_map(addr, dev->broadcast, haddr);
200 ip_ipgre_mc_map(addr, dev->broadcast, haddr);
204 memcpy(haddr, dev->broadcast, dev->addr_len);
212 static u32 arp_hash(const void *pkey,
213 const struct net_device *dev,
216 return arp_hashfn(pkey, dev, hash_rnd);
219 static bool arp_key_eq(const struct neighbour *neigh, const void *pkey)
221 return neigh_key_eq32(neigh, pkey);
224 static int arp_constructor(struct neighbour *neigh)
227 struct net_device *dev = neigh->dev;
228 struct in_device *in_dev;
229 struct neigh_parms *parms;
230 u32 inaddr_any = INADDR_ANY;
232 if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
233 memcpy(neigh->primary_key, &inaddr_any, arp_tbl.key_len);
235 addr = *(__be32 *)neigh->primary_key;
237 in_dev = __in_dev_get_rcu(dev);
243 neigh->type = inet_addr_type_dev_table(dev_net(dev), dev, addr);
245 parms = in_dev->arp_parms;
246 __neigh_parms_put(neigh->parms);
247 neigh->parms = neigh_parms_clone(parms);
250 if (!dev->header_ops) {
251 neigh->nud_state = NUD_NOARP;
252 neigh->ops = &arp_direct_ops;
253 neigh->output = neigh_direct_output;
255 /* Good devices (checked by reading texts, but only Ethernet is
258 ARPHRD_ETHER: (ethernet, apfddi)
261 ARPHRD_METRICOM: (strip)
265 ARPHRD_IPDDP will also work, if author repairs it.
266 I did not it, because this driver does not work even
270 if (neigh->type == RTN_MULTICAST) {
271 neigh->nud_state = NUD_NOARP;
272 arp_mc_map(addr, neigh->ha, dev, 1);
273 } else if (dev->flags & (IFF_NOARP | IFF_LOOPBACK)) {
274 neigh->nud_state = NUD_NOARP;
275 memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
276 } else if (neigh->type == RTN_BROADCAST ||
277 (dev->flags & IFF_POINTOPOINT)) {
278 neigh->nud_state = NUD_NOARP;
279 memcpy(neigh->ha, dev->broadcast, dev->addr_len);
282 if (dev->header_ops->cache)
283 neigh->ops = &arp_hh_ops;
285 neigh->ops = &arp_generic_ops;
287 if (neigh->nud_state & NUD_VALID)
288 neigh->output = neigh->ops->connected_output;
290 neigh->output = neigh->ops->output;
295 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
297 dst_link_failure(skb);
301 /* Create and send an arp packet. */
302 static void arp_send_dst(int type, int ptype, __be32 dest_ip,
303 struct net_device *dev, __be32 src_ip,
304 const unsigned char *dest_hw,
305 const unsigned char *src_hw,
306 const unsigned char *target_hw,
307 struct dst_entry *dst)
311 /* arp on this interface. */
312 if (dev->flags & IFF_NOARP)
315 skb = arp_create(type, ptype, dest_ip, dev, src_ip,
316 dest_hw, src_hw, target_hw);
320 skb_dst_set(skb, dst_clone(dst));
324 void arp_send(int type, int ptype, __be32 dest_ip,
325 struct net_device *dev, __be32 src_ip,
326 const unsigned char *dest_hw, const unsigned char *src_hw,
327 const unsigned char *target_hw)
329 arp_send_dst(type, ptype, dest_ip, dev, src_ip, dest_hw, src_hw,
332 EXPORT_SYMBOL(arp_send);
334 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
337 u8 dst_ha[MAX_ADDR_LEN], *dst_hw = NULL;
338 struct net_device *dev = neigh->dev;
339 __be32 target = *(__be32 *)neigh->primary_key;
340 int probes = atomic_read(&neigh->probes);
341 struct in_device *in_dev;
342 struct dst_entry *dst = NULL;
345 in_dev = __in_dev_get_rcu(dev);
350 switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
352 case 0: /* By default announce any local IP */
353 if (skb && inet_addr_type_dev_table(dev_net(dev), dev,
354 ip_hdr(skb)->saddr) == RTN_LOCAL)
355 saddr = ip_hdr(skb)->saddr;
357 case 1: /* Restrict announcements of saddr in same subnet */
360 saddr = ip_hdr(skb)->saddr;
361 if (inet_addr_type_dev_table(dev_net(dev), dev,
362 saddr) == RTN_LOCAL) {
363 /* saddr should be known to target */
364 if (inet_addr_onlink(in_dev, target, saddr))
369 case 2: /* Avoid secondary IPs, get a primary/preferred one */
375 saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);
377 probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES);
379 if (!(neigh->nud_state & NUD_VALID))
380 pr_debug("trying to ucast probe in NUD_INVALID\n");
381 neigh_ha_snapshot(dst_ha, neigh, dev);
384 probes -= NEIGH_VAR(neigh->parms, APP_PROBES);
391 if (skb && !(dev->priv_flags & IFF_XMIT_DST_RELEASE))
393 arp_send_dst(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
394 dst_hw, dev->dev_addr, NULL, dst);
397 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
399 struct net *net = dev_net(in_dev->dev);
402 switch (IN_DEV_ARP_IGNORE(in_dev)) {
403 case 0: /* Reply, the tip is already validated */
405 case 1: /* Reply only if tip is configured on the incoming interface */
407 scope = RT_SCOPE_HOST;
410 * Reply only if tip is configured on the incoming interface
411 * and is in same subnet as sip
413 scope = RT_SCOPE_HOST;
415 case 3: /* Do not reply for scope host addresses */
417 scope = RT_SCOPE_LINK;
420 case 4: /* Reserved */
425 case 8: /* Do not reply */
430 return !inet_confirm_addr(net, in_dev, sip, tip, scope);
433 static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
437 /*unsigned long now; */
438 struct net *net = dev_net(dev);
440 rt = ip_route_output(net, sip, tip, 0, l3mdev_master_ifindex_rcu(dev));
443 if (rt->dst.dev != dev) {
444 __NET_INC_STATS(net, LINUX_MIB_ARPFILTER);
452 * Check if we can use proxy ARP for this path
454 static inline int arp_fwd_proxy(struct in_device *in_dev,
455 struct net_device *dev, struct rtable *rt)
457 struct in_device *out_dev;
460 if (rt->dst.dev == dev)
463 if (!IN_DEV_PROXY_ARP(in_dev))
465 imi = IN_DEV_MEDIUM_ID(in_dev);
471 /* place to check for proxy_arp for routes */
473 out_dev = __in_dev_get_rcu(rt->dst.dev);
475 omi = IN_DEV_MEDIUM_ID(out_dev);
477 return omi != imi && omi != -1;
481 * Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
483 * RFC3069 supports proxy arp replies back to the same interface. This
484 * is done to support (ethernet) switch features, like RFC 3069, where
485 * the individual ports are not allowed to communicate with each
486 * other, BUT they are allowed to talk to the upstream router. As
487 * described in RFC 3069, it is possible to allow these hosts to
488 * communicate through the upstream router, by proxy_arp'ing.
490 * RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
492 * This technology is known by different names:
493 * In RFC 3069 it is called VLAN Aggregation.
494 * Cisco and Allied Telesyn call it Private VLAN.
495 * Hewlett-Packard call it Source-Port filtering or port-isolation.
496 * Ericsson call it MAC-Forced Forwarding (RFC Draft).
499 static inline int arp_fwd_pvlan(struct in_device *in_dev,
500 struct net_device *dev, struct rtable *rt,
501 __be32 sip, __be32 tip)
503 /* Private VLAN is only concerned about the same ethernet segment */
504 if (rt->dst.dev != dev)
507 /* Don't reply on self probes (often done by windowz boxes)*/
511 if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
518 * Interface to link layer: send routine and receive handler.
522 * Create an arp packet. If dest_hw is not set, we create a broadcast
525 struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
526 struct net_device *dev, __be32 src_ip,
527 const unsigned char *dest_hw,
528 const unsigned char *src_hw,
529 const unsigned char *target_hw)
533 unsigned char *arp_ptr;
534 int hlen = LL_RESERVED_SPACE(dev);
535 int tlen = dev->needed_tailroom;
541 skb = alloc_skb(arp_hdr_len(dev) + hlen + tlen, GFP_ATOMIC);
545 skb_reserve(skb, hlen);
546 skb_reset_network_header(skb);
547 arp = (struct arphdr *) skb_put(skb, arp_hdr_len(dev));
549 skb->protocol = htons(ETH_P_ARP);
551 src_hw = dev->dev_addr;
553 dest_hw = dev->broadcast;
556 * Fill the device header for the ARP frame
558 if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
562 * Fill out the arp protocol part.
564 * The arp hardware type should match the device type, except for FDDI,
565 * which (according to RFC 1390) should always equal 1 (Ethernet).
568 * Exceptions everywhere. AX.25 uses the AX.25 PID value not the
569 * DIX code for the protocol. Make these device structure fields.
573 arp->ar_hrd = htons(dev->type);
574 arp->ar_pro = htons(ETH_P_IP);
577 #if IS_ENABLED(CONFIG_AX25)
579 arp->ar_hrd = htons(ARPHRD_AX25);
580 arp->ar_pro = htons(AX25_P_IP);
583 #if IS_ENABLED(CONFIG_NETROM)
585 arp->ar_hrd = htons(ARPHRD_NETROM);
586 arp->ar_pro = htons(AX25_P_IP);
591 #if IS_ENABLED(CONFIG_FDDI)
593 arp->ar_hrd = htons(ARPHRD_ETHER);
594 arp->ar_pro = htons(ETH_P_IP);
599 arp->ar_hln = dev->addr_len;
601 arp->ar_op = htons(type);
603 arp_ptr = (unsigned char *)(arp + 1);
605 memcpy(arp_ptr, src_hw, dev->addr_len);
606 arp_ptr += dev->addr_len;
607 memcpy(arp_ptr, &src_ip, 4);
611 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
612 case ARPHRD_IEEE1394:
617 memcpy(arp_ptr, target_hw, dev->addr_len);
619 memset(arp_ptr, 0, dev->addr_len);
620 arp_ptr += dev->addr_len;
622 memcpy(arp_ptr, &dest_ip, 4);
630 EXPORT_SYMBOL(arp_create);
632 static int arp_xmit_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
634 return dev_queue_xmit(skb);
638 * Send an arp packet.
640 void arp_xmit(struct sk_buff *skb)
642 /* Send it off, maybe filter it using firewalling first. */
643 NF_HOOK(NFPROTO_ARP, NF_ARP_OUT,
644 dev_net(skb->dev), NULL, skb, NULL, skb->dev,
647 EXPORT_SYMBOL(arp_xmit);
650 * Process an arp request.
653 static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
655 struct net_device *dev = skb->dev;
656 struct in_device *in_dev = __in_dev_get_rcu(dev);
658 unsigned char *arp_ptr;
661 unsigned char *tha = NULL;
663 u16 dev_type = dev->type;
666 struct dst_entry *reply_dst = NULL;
667 bool is_garp = false;
669 /* arp_rcv below verifies the ARP header and verifies the device
680 if (arp->ar_pro != htons(ETH_P_IP) ||
681 htons(dev_type) != arp->ar_hrd)
688 * ETHERNET, and Fibre Channel (which are IEEE 802
689 * devices, according to RFC 2625) devices will accept ARP
690 * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
691 * This is the case also of FDDI, where the RFC 1390 says that
692 * FDDI devices should accept ARP hardware of (1) Ethernet,
693 * however, to be more robust, we'll accept both 1 (Ethernet)
696 if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
697 arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
698 arp->ar_pro != htons(ETH_P_IP))
702 if (arp->ar_pro != htons(AX25_P_IP) ||
703 arp->ar_hrd != htons(ARPHRD_AX25))
707 if (arp->ar_pro != htons(AX25_P_IP) ||
708 arp->ar_hrd != htons(ARPHRD_NETROM))
713 /* Understand only these message types */
715 if (arp->ar_op != htons(ARPOP_REPLY) &&
716 arp->ar_op != htons(ARPOP_REQUEST))
722 arp_ptr = (unsigned char *)(arp + 1);
724 arp_ptr += dev->addr_len;
725 memcpy(&sip, arp_ptr, 4);
728 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
729 case ARPHRD_IEEE1394:
734 arp_ptr += dev->addr_len;
736 memcpy(&tip, arp_ptr, 4);
738 * Check for bad requests for 127.x.x.x and requests for multicast
739 * addresses. If this is one such, delete it.
741 if (ipv4_is_multicast(tip) ||
742 (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
746 * For some 802.11 wireless deployments (and possibly other networks),
747 * there will be an ARP proxy and gratuitous ARP frames are attacks
748 * and thus should not be accepted.
750 if (sip == tip && IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP))
754 * Special case: We must set Frame Relay source Q.922 address
756 if (dev_type == ARPHRD_DLCI)
757 sha = dev->broadcast;
760 * Process entry. The idea here is we want to send a reply if it is a
761 * request for us or if it is a request for someone else that we hold
762 * a proxy for. We want to add an entry to our cache if it is a reply
763 * to us or if it is a request for our address.
764 * (The assumption for this last is that if someone is requesting our
765 * address, they are probably intending to talk to us, so it saves time
766 * if we cache their address. Their address is also probably not in
767 * our cache, since ours is not in their cache.)
769 * Putting this another way, we only care about replies if they are to
770 * us, in which case we add them to the cache. For requests, we care
771 * about those for us and those for our proxies. We reply to both,
772 * and in the case of requests for us we add the requester to the arp
776 if (arp->ar_op == htons(ARPOP_REQUEST) && skb_metadata_dst(skb))
777 reply_dst = (struct dst_entry *)
778 iptunnel_metadata_reply(skb_metadata_dst(skb),
781 /* Special case: IPv4 duplicate address detection packet (RFC2131) */
783 if (arp->ar_op == htons(ARPOP_REQUEST) &&
784 inet_addr_type_dev_table(net, dev, tip) == RTN_LOCAL &&
785 !arp_ignore(in_dev, sip, tip))
786 arp_send_dst(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip,
787 sha, dev->dev_addr, sha, reply_dst);
788 goto out_consume_skb;
791 if (arp->ar_op == htons(ARPOP_REQUEST) &&
792 ip_route_input_noref(skb, tip, sip, 0, dev) == 0) {
794 rt = skb_rtable(skb);
795 addr_type = rt->rt_type;
797 if (addr_type == RTN_LOCAL) {
800 dont_send = arp_ignore(in_dev, sip, tip);
801 if (!dont_send && IN_DEV_ARPFILTER(in_dev))
802 dont_send = arp_filter(sip, tip, dev);
804 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
806 arp_send_dst(ARPOP_REPLY, ETH_P_ARP,
813 goto out_consume_skb;
814 } else if (IN_DEV_FORWARD(in_dev)) {
815 if (addr_type == RTN_UNICAST &&
816 (arp_fwd_proxy(in_dev, dev, rt) ||
817 arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
818 (rt->dst.dev != dev &&
819 pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) {
820 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
824 if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
825 skb->pkt_type == PACKET_HOST ||
826 NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) {
827 arp_send_dst(ARPOP_REPLY, ETH_P_ARP,
832 pneigh_enqueue(&arp_tbl,
833 in_dev->arp_parms, skb);
836 goto out_consume_skb;
841 /* Update our ARP tables */
843 n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
845 if (IN_DEV_ARP_ACCEPT(in_dev)) {
846 unsigned int addr_type = inet_addr_type_dev_table(net, dev, sip);
848 /* Unsolicited ARP is not accepted by default.
849 It is possible, that this option should be enabled for some
850 devices (strip is candidate)
852 is_garp = tip == sip && addr_type == RTN_UNICAST;
854 /* Unsolicited ARP _replies_ also require target hwaddr to be
855 * the same as source.
857 if (is_garp && arp->ar_op == htons(ARPOP_REPLY))
859 /* IPv4 over IEEE 1394 doesn't provide target
860 * hardware address field in its ARP payload.
863 !memcmp(tha, sha, dev->addr_len);
866 ((arp->ar_op == htons(ARPOP_REPLY) &&
867 addr_type == RTN_UNICAST) || is_garp))
868 n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
872 int state = NUD_REACHABLE;
875 /* If several different ARP replies follows back-to-back,
876 use the FIRST one. It is possible, if several proxy
877 agents are active. Taking the first reply prevents
878 arp trashing and chooses the fastest router.
880 override = time_after(jiffies,
882 NEIGH_VAR(n->parms, LOCKTIME)) ||
885 /* Broadcast replies and request packets
886 do not assert neighbour reachability.
888 if (arp->ar_op != htons(ARPOP_REPLY) ||
889 skb->pkt_type != PACKET_HOST)
891 neigh_update(n, sha, state,
892 override ? NEIGH_UPDATE_F_OVERRIDE : 0);
900 dst_release(reply_dst);
901 return NET_RX_SUCCESS;
908 static void parp_redo(struct sk_buff *skb)
910 arp_process(dev_net(skb->dev), NULL, skb);
915 * Receive an arp request from the device layer.
918 static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
919 struct packet_type *pt, struct net_device *orig_dev)
921 const struct arphdr *arp;
923 /* do not tweak dropwatch on an ARP we will ignore */
924 if (dev->flags & IFF_NOARP ||
925 skb->pkt_type == PACKET_OTHERHOST ||
926 skb->pkt_type == PACKET_LOOPBACK)
929 skb = skb_share_check(skb, GFP_ATOMIC);
933 /* ARP header, plus 2 device addresses, plus 2 IP addresses. */
934 if (!pskb_may_pull(skb, arp_hdr_len(dev)))
938 if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4)
941 memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
943 return NF_HOOK(NFPROTO_ARP, NF_ARP_IN,
944 dev_net(dev), NULL, skb, dev, NULL,
949 return NET_RX_SUCCESS;
957 * User level interface (ioctl)
961 * Set (create) an ARP cache entry.
964 static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
967 IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
970 if (__in_dev_get_rtnl(dev)) {
971 IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
977 static int arp_req_set_public(struct net *net, struct arpreq *r,
978 struct net_device *dev)
980 __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
981 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
983 if (mask && mask != htonl(0xFFFFFFFF))
985 if (!dev && (r->arp_flags & ATF_COM)) {
986 dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
992 if (!pneigh_lookup(&arp_tbl, net, &ip, dev, 1))
997 return arp_req_set_proxy(net, dev, 1);
1000 static int arp_req_set(struct net *net, struct arpreq *r,
1001 struct net_device *dev)
1004 struct neighbour *neigh;
1007 if (r->arp_flags & ATF_PUBL)
1008 return arp_req_set_public(net, r, dev);
1010 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1011 if (r->arp_flags & ATF_PERM)
1012 r->arp_flags |= ATF_COM;
1014 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1023 switch (dev->type) {
1024 #if IS_ENABLED(CONFIG_FDDI)
1027 * According to RFC 1390, FDDI devices should accept ARP
1028 * hardware types of 1 (Ethernet). However, to be more
1029 * robust, we'll accept hardware types of either 1 (Ethernet)
1030 * or 6 (IEEE 802.2).
1032 if (r->arp_ha.sa_family != ARPHRD_FDDI &&
1033 r->arp_ha.sa_family != ARPHRD_ETHER &&
1034 r->arp_ha.sa_family != ARPHRD_IEEE802)
1039 if (r->arp_ha.sa_family != dev->type)
1044 neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
1045 err = PTR_ERR(neigh);
1046 if (!IS_ERR(neigh)) {
1047 unsigned int state = NUD_STALE;
1048 if (r->arp_flags & ATF_PERM)
1049 state = NUD_PERMANENT;
1050 err = neigh_update(neigh, (r->arp_flags & ATF_COM) ?
1051 r->arp_ha.sa_data : NULL, state,
1052 NEIGH_UPDATE_F_OVERRIDE |
1053 NEIGH_UPDATE_F_ADMIN);
1054 neigh_release(neigh);
1059 static unsigned int arp_state_to_flags(struct neighbour *neigh)
1061 if (neigh->nud_state&NUD_PERMANENT)
1062 return ATF_PERM | ATF_COM;
1063 else if (neigh->nud_state&NUD_VALID)
1070 * Get an ARP cache entry.
1073 static int arp_req_get(struct arpreq *r, struct net_device *dev)
1075 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1076 struct neighbour *neigh;
1079 neigh = neigh_lookup(&arp_tbl, &ip, dev);
1081 if (!(neigh->nud_state & NUD_NOARP)) {
1082 read_lock_bh(&neigh->lock);
1083 memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
1084 r->arp_flags = arp_state_to_flags(neigh);
1085 read_unlock_bh(&neigh->lock);
1086 r->arp_ha.sa_family = dev->type;
1087 strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
1090 neigh_release(neigh);
1095 static int arp_invalidate(struct net_device *dev, __be32 ip)
1097 struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
1101 if (neigh->nud_state & ~NUD_NOARP)
1102 err = neigh_update(neigh, NULL, NUD_FAILED,
1103 NEIGH_UPDATE_F_OVERRIDE|
1104 NEIGH_UPDATE_F_ADMIN);
1105 neigh_release(neigh);
1111 static int arp_req_delete_public(struct net *net, struct arpreq *r,
1112 struct net_device *dev)
1114 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1115 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1117 if (mask == htonl(0xFFFFFFFF))
1118 return pneigh_delete(&arp_tbl, net, &ip, dev);
1123 return arp_req_set_proxy(net, dev, 0);
1126 static int arp_req_delete(struct net *net, struct arpreq *r,
1127 struct net_device *dev)
1131 if (r->arp_flags & ATF_PUBL)
1132 return arp_req_delete_public(net, r, dev);
1134 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1136 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1144 return arp_invalidate(dev, ip);
1148 * Handle an ARP layer I/O control request.
1151 int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
1155 struct net_device *dev = NULL;
1160 if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
1163 err = copy_from_user(&r, arg, sizeof(struct arpreq));
1171 if (r.arp_pa.sa_family != AF_INET)
1172 return -EPFNOSUPPORT;
1174 if (!(r.arp_flags & ATF_PUBL) &&
1175 (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
1177 if (!(r.arp_flags & ATF_NETMASK))
1178 ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
1179 htonl(0xFFFFFFFFUL);
1183 dev = __dev_get_by_name(net, r.arp_dev);
1187 /* Mmmm... It is wrong... ARPHRD_NETROM==0 */
1188 if (!r.arp_ha.sa_family)
1189 r.arp_ha.sa_family = dev->type;
1191 if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
1193 } else if (cmd == SIOCGARP) {
1200 err = arp_req_delete(net, &r, dev);
1203 err = arp_req_set(net, &r, dev);
1206 err = arp_req_get(&r, dev);
1211 if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
1216 static int arp_netdev_event(struct notifier_block *this, unsigned long event,
1219 struct net_device *dev = netdev_notifier_info_to_dev(ptr);
1220 struct netdev_notifier_change_info *change_info;
1223 case NETDEV_CHANGEADDR:
1224 neigh_changeaddr(&arp_tbl, dev);
1225 rt_cache_flush(dev_net(dev));
1229 if (change_info->flags_changed & IFF_NOARP)
1230 neigh_changeaddr(&arp_tbl, dev);
1239 static struct notifier_block arp_netdev_notifier = {
1240 .notifier_call = arp_netdev_event,
1243 /* Note, that it is not on notifier chain.
1244 It is necessary, that this routine was called after route cache will be
1247 void arp_ifdown(struct net_device *dev)
1249 neigh_ifdown(&arp_tbl, dev);
1254 * Called once on startup.
1257 static struct packet_type arp_packet_type __read_mostly = {
1258 .type = cpu_to_be16(ETH_P_ARP),
1262 static int arp_proc_init(void);
1264 void __init arp_init(void)
1266 neigh_table_init(NEIGH_ARP_TABLE, &arp_tbl);
1268 dev_add_pack(&arp_packet_type);
1270 #ifdef CONFIG_SYSCTL
1271 neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
1273 register_netdevice_notifier(&arp_netdev_notifier);
1276 #ifdef CONFIG_PROC_FS
1277 #if IS_ENABLED(CONFIG_AX25)
1279 /* ------------------------------------------------------------------------ */
1281 * ax25 -> ASCII conversion
1283 static void ax2asc2(ax25_address *a, char *buf)
1288 for (n = 0, s = buf; n < 6; n++) {
1289 c = (a->ax25_call[n] >> 1) & 0x7F;
1296 n = (a->ax25_call[6] >> 1) & 0x0F;
1305 if (*buf == '\0' || *buf == '-') {
1310 #endif /* CONFIG_AX25 */
1312 #define HBUFFERLEN 30
1314 static void arp_format_neigh_entry(struct seq_file *seq,
1315 struct neighbour *n)
1317 char hbuffer[HBUFFERLEN];
1320 struct net_device *dev = n->dev;
1321 int hatype = dev->type;
1323 read_lock(&n->lock);
1324 /* Convert hardware address to XX:XX:XX:XX ... form. */
1325 #if IS_ENABLED(CONFIG_AX25)
1326 if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
1327 ax2asc2((ax25_address *)n->ha, hbuffer);
1330 for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
1331 hbuffer[k++] = hex_asc_hi(n->ha[j]);
1332 hbuffer[k++] = hex_asc_lo(n->ha[j]);
1338 #if IS_ENABLED(CONFIG_AX25)
1341 sprintf(tbuf, "%pI4", n->primary_key);
1342 seq_printf(seq, "%-16s 0x%-10x0x%-10x%-17s * %s\n",
1343 tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
1344 read_unlock(&n->lock);
1347 static void arp_format_pneigh_entry(struct seq_file *seq,
1348 struct pneigh_entry *n)
1350 struct net_device *dev = n->dev;
1351 int hatype = dev ? dev->type : 0;
1354 sprintf(tbuf, "%pI4", n->key);
1355 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1356 tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
1357 dev ? dev->name : "*");
1360 static int arp_seq_show(struct seq_file *seq, void *v)
1362 if (v == SEQ_START_TOKEN) {
1363 seq_puts(seq, "IP address HW type Flags "
1364 "HW address Mask Device\n");
1366 struct neigh_seq_state *state = seq->private;
1368 if (state->flags & NEIGH_SEQ_IS_PNEIGH)
1369 arp_format_pneigh_entry(seq, v);
1371 arp_format_neigh_entry(seq, v);
1377 static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
1379 /* Don't want to confuse "arp -a" w/ magic entries,
1380 * so we tell the generic iterator to skip NUD_NOARP.
1382 return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
1385 /* ------------------------------------------------------------------------ */
1387 static const struct seq_operations arp_seq_ops = {
1388 .start = arp_seq_start,
1389 .next = neigh_seq_next,
1390 .stop = neigh_seq_stop,
1391 .show = arp_seq_show,
1394 static int arp_seq_open(struct inode *inode, struct file *file)
1396 return seq_open_net(inode, file, &arp_seq_ops,
1397 sizeof(struct neigh_seq_state));
1400 static const struct file_operations arp_seq_fops = {
1401 .owner = THIS_MODULE,
1402 .open = arp_seq_open,
1404 .llseek = seq_lseek,
1405 .release = seq_release_net,
1409 static int __net_init arp_net_init(struct net *net)
1411 if (!proc_create("arp", S_IRUGO, net->proc_net, &arp_seq_fops))
1416 static void __net_exit arp_net_exit(struct net *net)
1418 remove_proc_entry("arp", net->proc_net);
1421 static struct pernet_operations arp_net_ops = {
1422 .init = arp_net_init,
1423 .exit = arp_net_exit,
1426 static int __init arp_proc_init(void)
1428 return register_pernet_subsys(&arp_net_ops);
1431 #else /* CONFIG_PROC_FS */
1433 static int __init arp_proc_init(void)
1438 #endif /* CONFIG_PROC_FS */