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_table(dev_net(dev), 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_table(dev_net(dev), 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_table(dev_net(dev), dev,
355 saddr) == RTN_LOCAL) {
356 /* saddr should be known to target */
357 if (inet_addr_onlink(in_dev, target, saddr))
362 case 2: /* Avoid secondary IPs, get a primary/preferred one */
368 saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);
370 probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES);
372 if (!(neigh->nud_state & NUD_VALID))
373 pr_debug("trying to ucast probe in NUD_INVALID\n");
374 neigh_ha_snapshot(dst_ha, neigh, dev);
377 probes -= NEIGH_VAR(neigh->parms, APP_PROBES);
384 arp_send_dst(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
385 dst_hw, dev->dev_addr, NULL,
386 dev->priv_flags & IFF_XMIT_DST_RELEASE ? NULL : skb);
389 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
391 struct net *net = dev_net(in_dev->dev);
394 switch (IN_DEV_ARP_IGNORE(in_dev)) {
395 case 0: /* Reply, the tip is already validated */
397 case 1: /* Reply only if tip is configured on the incoming interface */
399 scope = RT_SCOPE_HOST;
402 * Reply only if tip is configured on the incoming interface
403 * and is in same subnet as sip
405 scope = RT_SCOPE_HOST;
407 case 3: /* Do not reply for scope host addresses */
409 scope = RT_SCOPE_LINK;
412 case 4: /* Reserved */
417 case 8: /* Do not reply */
422 return !inet_confirm_addr(net, in_dev, sip, tip, scope);
425 static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
429 /*unsigned long now; */
430 struct net *net = dev_net(dev);
432 rt = ip_route_output(net, sip, tip, 0, 0);
435 if (rt->dst.dev != dev) {
436 NET_INC_STATS_BH(net, LINUX_MIB_ARPFILTER);
444 * Check if we can use proxy ARP for this path
446 static inline int arp_fwd_proxy(struct in_device *in_dev,
447 struct net_device *dev, struct rtable *rt)
449 struct in_device *out_dev;
452 if (rt->dst.dev == dev)
455 if (!IN_DEV_PROXY_ARP(in_dev))
457 imi = IN_DEV_MEDIUM_ID(in_dev);
463 /* place to check for proxy_arp for routes */
465 out_dev = __in_dev_get_rcu(rt->dst.dev);
467 omi = IN_DEV_MEDIUM_ID(out_dev);
469 return omi != imi && omi != -1;
473 * Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
475 * RFC3069 supports proxy arp replies back to the same interface. This
476 * is done to support (ethernet) switch features, like RFC 3069, where
477 * the individual ports are not allowed to communicate with each
478 * other, BUT they are allowed to talk to the upstream router. As
479 * described in RFC 3069, it is possible to allow these hosts to
480 * communicate through the upstream router, by proxy_arp'ing.
482 * RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
484 * This technology is known by different names:
485 * In RFC 3069 it is called VLAN Aggregation.
486 * Cisco and Allied Telesyn call it Private VLAN.
487 * Hewlett-Packard call it Source-Port filtering or port-isolation.
488 * Ericsson call it MAC-Forced Forwarding (RFC Draft).
491 static inline int arp_fwd_pvlan(struct in_device *in_dev,
492 struct net_device *dev, struct rtable *rt,
493 __be32 sip, __be32 tip)
495 /* Private VLAN is only concerned about the same ethernet segment */
496 if (rt->dst.dev != dev)
499 /* Don't reply on self probes (often done by windowz boxes)*/
503 if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
510 * Interface to link layer: send routine and receive handler.
514 * Create an arp packet. If dest_hw is not set, we create a broadcast
517 struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
518 struct net_device *dev, __be32 src_ip,
519 const unsigned char *dest_hw,
520 const unsigned char *src_hw,
521 const unsigned char *target_hw)
525 unsigned char *arp_ptr;
526 int hlen = LL_RESERVED_SPACE(dev);
527 int tlen = dev->needed_tailroom;
533 skb = alloc_skb(arp_hdr_len(dev) + hlen + tlen, GFP_ATOMIC);
537 skb_reserve(skb, hlen);
538 skb_reset_network_header(skb);
539 arp = (struct arphdr *) skb_put(skb, arp_hdr_len(dev));
541 skb->protocol = htons(ETH_P_ARP);
543 src_hw = dev->dev_addr;
545 dest_hw = dev->broadcast;
548 * Fill the device header for the ARP frame
550 if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
554 * Fill out the arp protocol part.
556 * The arp hardware type should match the device type, except for FDDI,
557 * which (according to RFC 1390) should always equal 1 (Ethernet).
560 * Exceptions everywhere. AX.25 uses the AX.25 PID value not the
561 * DIX code for the protocol. Make these device structure fields.
565 arp->ar_hrd = htons(dev->type);
566 arp->ar_pro = htons(ETH_P_IP);
569 #if IS_ENABLED(CONFIG_AX25)
571 arp->ar_hrd = htons(ARPHRD_AX25);
572 arp->ar_pro = htons(AX25_P_IP);
575 #if IS_ENABLED(CONFIG_NETROM)
577 arp->ar_hrd = htons(ARPHRD_NETROM);
578 arp->ar_pro = htons(AX25_P_IP);
583 #if IS_ENABLED(CONFIG_FDDI)
585 arp->ar_hrd = htons(ARPHRD_ETHER);
586 arp->ar_pro = htons(ETH_P_IP);
591 arp->ar_hln = dev->addr_len;
593 arp->ar_op = htons(type);
595 arp_ptr = (unsigned char *)(arp + 1);
597 memcpy(arp_ptr, src_hw, dev->addr_len);
598 arp_ptr += dev->addr_len;
599 memcpy(arp_ptr, &src_ip, 4);
603 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
604 case ARPHRD_IEEE1394:
609 memcpy(arp_ptr, target_hw, dev->addr_len);
611 memset(arp_ptr, 0, dev->addr_len);
612 arp_ptr += dev->addr_len;
614 memcpy(arp_ptr, &dest_ip, 4);
622 EXPORT_SYMBOL(arp_create);
625 * Send an arp packet.
627 void arp_xmit(struct sk_buff *skb)
629 /* Send it off, maybe filter it using firewalling first. */
630 NF_HOOK(NFPROTO_ARP, NF_ARP_OUT, NULL, skb,
631 NULL, skb->dev, dev_queue_xmit_sk);
633 EXPORT_SYMBOL(arp_xmit);
636 * Process an arp request.
639 static int arp_process(struct sock *sk, struct sk_buff *skb)
641 struct net_device *dev = skb->dev;
642 struct in_device *in_dev = __in_dev_get_rcu(dev);
644 unsigned char *arp_ptr;
648 u16 dev_type = dev->type;
651 struct net *net = dev_net(dev);
652 bool is_garp = false;
654 /* arp_rcv below verifies the ARP header and verifies the device
665 if (arp->ar_pro != htons(ETH_P_IP) ||
666 htons(dev_type) != arp->ar_hrd)
673 * ETHERNET, and Fibre Channel (which are IEEE 802
674 * devices, according to RFC 2625) devices will accept ARP
675 * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
676 * This is the case also of FDDI, where the RFC 1390 says that
677 * FDDI devices should accept ARP hardware of (1) Ethernet,
678 * however, to be more robust, we'll accept both 1 (Ethernet)
681 if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
682 arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
683 arp->ar_pro != htons(ETH_P_IP))
687 if (arp->ar_pro != htons(AX25_P_IP) ||
688 arp->ar_hrd != htons(ARPHRD_AX25))
692 if (arp->ar_pro != htons(AX25_P_IP) ||
693 arp->ar_hrd != htons(ARPHRD_NETROM))
698 /* Understand only these message types */
700 if (arp->ar_op != htons(ARPOP_REPLY) &&
701 arp->ar_op != htons(ARPOP_REQUEST))
707 arp_ptr = (unsigned char *)(arp + 1);
709 arp_ptr += dev->addr_len;
710 memcpy(&sip, arp_ptr, 4);
713 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
714 case ARPHRD_IEEE1394:
718 arp_ptr += dev->addr_len;
720 memcpy(&tip, arp_ptr, 4);
722 * Check for bad requests for 127.x.x.x and requests for multicast
723 * addresses. If this is one such, delete it.
725 if (ipv4_is_multicast(tip) ||
726 (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
730 * Special case: We must set Frame Relay source Q.922 address
732 if (dev_type == ARPHRD_DLCI)
733 sha = dev->broadcast;
736 * Process entry. The idea here is we want to send a reply if it is a
737 * request for us or if it is a request for someone else that we hold
738 * a proxy for. We want to add an entry to our cache if it is a reply
739 * to us or if it is a request for our address.
740 * (The assumption for this last is that if someone is requesting our
741 * address, they are probably intending to talk to us, so it saves time
742 * if we cache their address. Their address is also probably not in
743 * our cache, since ours is not in their cache.)
745 * Putting this another way, we only care about replies if they are to
746 * us, in which case we add them to the cache. For requests, we care
747 * about those for us and those for our proxies. We reply to both,
748 * and in the case of requests for us we add the requester to the arp
752 /* Special case: IPv4 duplicate address detection packet (RFC2131) */
754 if (arp->ar_op == htons(ARPOP_REQUEST) &&
755 inet_addr_type_dev_table(net, dev, tip) == RTN_LOCAL &&
756 !arp_ignore(in_dev, sip, tip))
757 arp_send(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,
762 if (arp->ar_op == htons(ARPOP_REQUEST) &&
763 ip_route_input_noref(skb, tip, sip, 0, dev) == 0) {
765 rt = skb_rtable(skb);
766 addr_type = rt->rt_type;
768 if (addr_type == RTN_LOCAL) {
771 dont_send = arp_ignore(in_dev, sip, tip);
772 if (!dont_send && IN_DEV_ARPFILTER(in_dev))
773 dont_send = arp_filter(sip, tip, dev);
775 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
777 arp_send(ARPOP_REPLY, ETH_P_ARP, sip,
778 dev, tip, sha, dev->dev_addr,
784 } else if (IN_DEV_FORWARD(in_dev)) {
785 if (addr_type == RTN_UNICAST &&
786 (arp_fwd_proxy(in_dev, dev, rt) ||
787 arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
788 (rt->dst.dev != dev &&
789 pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) {
790 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
794 if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
795 skb->pkt_type == PACKET_HOST ||
796 NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) {
797 arp_send(ARPOP_REPLY, ETH_P_ARP, sip,
798 dev, tip, sha, dev->dev_addr,
801 pneigh_enqueue(&arp_tbl,
802 in_dev->arp_parms, skb);
810 /* Update our ARP tables */
812 n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
814 if (IN_DEV_ARP_ACCEPT(in_dev)) {
815 unsigned int addr_type = inet_addr_type_dev_table(net, dev, sip);
817 /* Unsolicited ARP is not accepted by default.
818 It is possible, that this option should be enabled for some
819 devices (strip is candidate)
821 is_garp = arp->ar_op == htons(ARPOP_REQUEST) && tip == sip &&
822 addr_type == RTN_UNICAST;
825 ((arp->ar_op == htons(ARPOP_REPLY) &&
826 addr_type == RTN_UNICAST) || is_garp))
827 n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
831 int state = NUD_REACHABLE;
834 /* If several different ARP replies follows back-to-back,
835 use the FIRST one. It is possible, if several proxy
836 agents are active. Taking the first reply prevents
837 arp trashing and chooses the fastest router.
839 override = time_after(jiffies,
841 NEIGH_VAR(n->parms, LOCKTIME)) ||
844 /* Broadcast replies and request packets
845 do not assert neighbour reachability.
847 if (arp->ar_op != htons(ARPOP_REPLY) ||
848 skb->pkt_type != PACKET_HOST)
850 neigh_update(n, sha, state,
851 override ? NEIGH_UPDATE_F_OVERRIDE : 0);
860 static void parp_redo(struct sk_buff *skb)
862 arp_process(NULL, skb);
867 * Receive an arp request from the device layer.
870 static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
871 struct packet_type *pt, struct net_device *orig_dev)
873 const struct arphdr *arp;
875 /* do not tweak dropwatch on an ARP we will ignore */
876 if (dev->flags & IFF_NOARP ||
877 skb->pkt_type == PACKET_OTHERHOST ||
878 skb->pkt_type == PACKET_LOOPBACK)
881 skb = skb_share_check(skb, GFP_ATOMIC);
885 /* ARP header, plus 2 device addresses, plus 2 IP addresses. */
886 if (!pskb_may_pull(skb, arp_hdr_len(dev)))
890 if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4)
893 memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
895 return NF_HOOK(NFPROTO_ARP, NF_ARP_IN, NULL, skb,
896 dev, NULL, arp_process);
908 * User level interface (ioctl)
912 * Set (create) an ARP cache entry.
915 static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
918 IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
921 if (__in_dev_get_rtnl(dev)) {
922 IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
928 static int arp_req_set_public(struct net *net, struct arpreq *r,
929 struct net_device *dev)
931 __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
932 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
934 if (mask && mask != htonl(0xFFFFFFFF))
936 if (!dev && (r->arp_flags & ATF_COM)) {
937 dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
943 if (!pneigh_lookup(&arp_tbl, net, &ip, dev, 1))
948 return arp_req_set_proxy(net, dev, 1);
951 static int arp_req_set(struct net *net, struct arpreq *r,
952 struct net_device *dev)
955 struct neighbour *neigh;
958 if (r->arp_flags & ATF_PUBL)
959 return arp_req_set_public(net, r, dev);
961 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
962 if (r->arp_flags & ATF_PERM)
963 r->arp_flags |= ATF_COM;
965 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
975 #if IS_ENABLED(CONFIG_FDDI)
978 * According to RFC 1390, FDDI devices should accept ARP
979 * hardware types of 1 (Ethernet). However, to be more
980 * robust, we'll accept hardware types of either 1 (Ethernet)
983 if (r->arp_ha.sa_family != ARPHRD_FDDI &&
984 r->arp_ha.sa_family != ARPHRD_ETHER &&
985 r->arp_ha.sa_family != ARPHRD_IEEE802)
990 if (r->arp_ha.sa_family != dev->type)
995 neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
996 err = PTR_ERR(neigh);
997 if (!IS_ERR(neigh)) {
998 unsigned int state = NUD_STALE;
999 if (r->arp_flags & ATF_PERM)
1000 state = NUD_PERMANENT;
1001 err = neigh_update(neigh, (r->arp_flags & ATF_COM) ?
1002 r->arp_ha.sa_data : NULL, state,
1003 NEIGH_UPDATE_F_OVERRIDE |
1004 NEIGH_UPDATE_F_ADMIN);
1005 neigh_release(neigh);
1010 static unsigned int arp_state_to_flags(struct neighbour *neigh)
1012 if (neigh->nud_state&NUD_PERMANENT)
1013 return ATF_PERM | ATF_COM;
1014 else if (neigh->nud_state&NUD_VALID)
1021 * Get an ARP cache entry.
1024 static int arp_req_get(struct arpreq *r, struct net_device *dev)
1026 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1027 struct neighbour *neigh;
1030 neigh = neigh_lookup(&arp_tbl, &ip, dev);
1032 if (!(neigh->nud_state & NUD_NOARP)) {
1033 read_lock_bh(&neigh->lock);
1034 memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
1035 r->arp_flags = arp_state_to_flags(neigh);
1036 read_unlock_bh(&neigh->lock);
1037 r->arp_ha.sa_family = dev->type;
1038 strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
1041 neigh_release(neigh);
1046 static int arp_invalidate(struct net_device *dev, __be32 ip)
1048 struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
1052 if (neigh->nud_state & ~NUD_NOARP)
1053 err = neigh_update(neigh, NULL, NUD_FAILED,
1054 NEIGH_UPDATE_F_OVERRIDE|
1055 NEIGH_UPDATE_F_ADMIN);
1056 neigh_release(neigh);
1062 static int arp_req_delete_public(struct net *net, struct arpreq *r,
1063 struct net_device *dev)
1065 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1066 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1068 if (mask == htonl(0xFFFFFFFF))
1069 return pneigh_delete(&arp_tbl, net, &ip, dev);
1074 return arp_req_set_proxy(net, dev, 0);
1077 static int arp_req_delete(struct net *net, struct arpreq *r,
1078 struct net_device *dev)
1082 if (r->arp_flags & ATF_PUBL)
1083 return arp_req_delete_public(net, r, dev);
1085 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1087 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1095 return arp_invalidate(dev, ip);
1099 * Handle an ARP layer I/O control request.
1102 int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
1106 struct net_device *dev = NULL;
1111 if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
1114 err = copy_from_user(&r, arg, sizeof(struct arpreq));
1122 if (r.arp_pa.sa_family != AF_INET)
1123 return -EPFNOSUPPORT;
1125 if (!(r.arp_flags & ATF_PUBL) &&
1126 (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
1128 if (!(r.arp_flags & ATF_NETMASK))
1129 ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
1130 htonl(0xFFFFFFFFUL);
1134 dev = __dev_get_by_name(net, r.arp_dev);
1138 /* Mmmm... It is wrong... ARPHRD_NETROM==0 */
1139 if (!r.arp_ha.sa_family)
1140 r.arp_ha.sa_family = dev->type;
1142 if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
1144 } else if (cmd == SIOCGARP) {
1151 err = arp_req_delete(net, &r, dev);
1154 err = arp_req_set(net, &r, dev);
1157 err = arp_req_get(&r, dev);
1162 if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
1167 static int arp_netdev_event(struct notifier_block *this, unsigned long event,
1170 struct net_device *dev = netdev_notifier_info_to_dev(ptr);
1171 struct netdev_notifier_change_info *change_info;
1174 case NETDEV_CHANGEADDR:
1175 neigh_changeaddr(&arp_tbl, dev);
1176 rt_cache_flush(dev_net(dev));
1180 if (change_info->flags_changed & IFF_NOARP)
1181 neigh_changeaddr(&arp_tbl, dev);
1190 static struct notifier_block arp_netdev_notifier = {
1191 .notifier_call = arp_netdev_event,
1194 /* Note, that it is not on notifier chain.
1195 It is necessary, that this routine was called after route cache will be
1198 void arp_ifdown(struct net_device *dev)
1200 neigh_ifdown(&arp_tbl, dev);
1205 * Called once on startup.
1208 static struct packet_type arp_packet_type __read_mostly = {
1209 .type = cpu_to_be16(ETH_P_ARP),
1213 static int arp_proc_init(void);
1215 void __init arp_init(void)
1217 neigh_table_init(NEIGH_ARP_TABLE, &arp_tbl);
1219 dev_add_pack(&arp_packet_type);
1221 #ifdef CONFIG_SYSCTL
1222 neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
1224 register_netdevice_notifier(&arp_netdev_notifier);
1227 #ifdef CONFIG_PROC_FS
1228 #if IS_ENABLED(CONFIG_AX25)
1230 /* ------------------------------------------------------------------------ */
1232 * ax25 -> ASCII conversion
1234 static char *ax2asc2(ax25_address *a, char *buf)
1239 for (n = 0, s = buf; n < 6; n++) {
1240 c = (a->ax25_call[n] >> 1) & 0x7F;
1247 n = (a->ax25_call[6] >> 1) & 0x0F;
1256 if (*buf == '\0' || *buf == '-')
1261 #endif /* CONFIG_AX25 */
1263 #define HBUFFERLEN 30
1265 static void arp_format_neigh_entry(struct seq_file *seq,
1266 struct neighbour *n)
1268 char hbuffer[HBUFFERLEN];
1271 struct net_device *dev = n->dev;
1272 int hatype = dev->type;
1274 read_lock(&n->lock);
1275 /* Convert hardware address to XX:XX:XX:XX ... form. */
1276 #if IS_ENABLED(CONFIG_AX25)
1277 if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
1278 ax2asc2((ax25_address *)n->ha, hbuffer);
1281 for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
1282 hbuffer[k++] = hex_asc_hi(n->ha[j]);
1283 hbuffer[k++] = hex_asc_lo(n->ha[j]);
1289 #if IS_ENABLED(CONFIG_AX25)
1292 sprintf(tbuf, "%pI4", n->primary_key);
1293 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1294 tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
1295 read_unlock(&n->lock);
1298 static void arp_format_pneigh_entry(struct seq_file *seq,
1299 struct pneigh_entry *n)
1301 struct net_device *dev = n->dev;
1302 int hatype = dev ? dev->type : 0;
1305 sprintf(tbuf, "%pI4", n->key);
1306 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1307 tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
1308 dev ? dev->name : "*");
1311 static int arp_seq_show(struct seq_file *seq, void *v)
1313 if (v == SEQ_START_TOKEN) {
1314 seq_puts(seq, "IP address HW type Flags "
1315 "HW address Mask Device\n");
1317 struct neigh_seq_state *state = seq->private;
1319 if (state->flags & NEIGH_SEQ_IS_PNEIGH)
1320 arp_format_pneigh_entry(seq, v);
1322 arp_format_neigh_entry(seq, v);
1328 static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
1330 /* Don't want to confuse "arp -a" w/ magic entries,
1331 * so we tell the generic iterator to skip NUD_NOARP.
1333 return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
1336 /* ------------------------------------------------------------------------ */
1338 static const struct seq_operations arp_seq_ops = {
1339 .start = arp_seq_start,
1340 .next = neigh_seq_next,
1341 .stop = neigh_seq_stop,
1342 .show = arp_seq_show,
1345 static int arp_seq_open(struct inode *inode, struct file *file)
1347 return seq_open_net(inode, file, &arp_seq_ops,
1348 sizeof(struct neigh_seq_state));
1351 static const struct file_operations arp_seq_fops = {
1352 .owner = THIS_MODULE,
1353 .open = arp_seq_open,
1355 .llseek = seq_lseek,
1356 .release = seq_release_net,
1360 static int __net_init arp_net_init(struct net *net)
1362 if (!proc_create("arp", S_IRUGO, net->proc_net, &arp_seq_fops))
1367 static void __net_exit arp_net_exit(struct net *net)
1369 remove_proc_entry("arp", net->proc_net);
1372 static struct pernet_operations arp_net_ops = {
1373 .init = arp_net_init,
1374 .exit = arp_net_exit,
1377 static int __init arp_proc_init(void)
1379 return register_pernet_subsys(&arp_net_ops);
1382 #else /* CONFIG_PROC_FS */
1384 static int __init arp_proc_init(void)
1389 #endif /* CONFIG_PROC_FS */