1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* linux/net/ipv4/arp.c
4 * Copyright (C) 1994 by Florian La Roche
6 * This module implements the Address Resolution Protocol ARP (RFC 826),
7 * which is used to convert IP addresses (or in the future maybe other
8 * high-level addresses) into a low-level hardware address (like an Ethernet
12 * Alan Cox : Removed the Ethernet assumptions in
14 * Alan Cox : Fixed some small errors in the ARP
16 * Alan Cox : Allow >4K in /proc
17 * Alan Cox : Make ARP add its own protocol entry
18 * Ross Martin : Rewrote arp_rcv() and arp_get_info()
19 * Stephen Henson : Add AX25 support to arp_get_info()
20 * Alan Cox : Drop data when a device is downed.
21 * Alan Cox : Use init_timer().
22 * Alan Cox : Double lock fixes.
23 * Martin Seine : Move the arphdr structure
24 * to if_arp.h for compatibility.
25 * with BSD based programs.
26 * Andrew Tridgell : Added ARP netmask code and
27 * re-arranged proxy handling.
28 * Alan Cox : Changed to use notifiers.
29 * Niibe Yutaka : Reply for this device or proxies only.
30 * Alan Cox : Don't proxy across hardware types!
31 * Jonathan Naylor : Added support for NET/ROM.
32 * Mike Shaver : RFC1122 checks.
33 * Jonathan Naylor : Only lookup the hardware address for
34 * the correct hardware type.
35 * Germano Caronni : Assorted subtle races.
36 * Craig Schlenter : Don't modify permanent entry
38 * Russ Nelson : Tidied up a few bits.
39 * Alexey Kuznetsov: Major changes to caching and behaviour,
40 * eg intelligent arp probing and
42 * of host down events.
43 * Alan Cox : Missing unlock in device events.
44 * Eckes : ARP ioctl control errors.
45 * Alexey Kuznetsov: Arp free fix.
46 * Manuel Rodriguez: Gratuitous ARP.
47 * Jonathan Layes : Added arpd support through kerneld
48 * message queue (960314)
49 * Mike Shaver : /proc/sys/net/ipv4/arp_* support
50 * Mike McLagan : Routing by source
51 * Stuart Cheshire : Metricom and grat arp fixes
52 * *** FOR 2.1 clean this up ***
53 * Lawrence V. Stefani: (08/12/96) Added FDDI support.
54 * Alan Cox : Took the AP1000 nasty FDDI hack and
55 * folded into the mainstream FDDI code.
56 * Ack spit, Linus how did you allow that
58 * Jes Sorensen : Make FDDI work again in 2.1.x and
59 * clean up the APFDDI & gen. FDDI bits.
60 * Alexey Kuznetsov: new arp state machine;
61 * now it is in net/core/neighbour.c.
62 * Krzysztof Halasa: Added Frame Relay ARP support.
63 * Arnaldo C. Melo : convert /proc/net/arp to seq_file
64 * Shmulik Hen: Split arp_send to arp_create and
65 * arp_xmit so intermediate drivers like
66 * bonding can change the skb before
67 * sending (e.g. insert 8021q tag).
68 * Harald Welte : convert to make use of jenkins hash
69 * Jesper D. Brouer: Proxy ARP PVLAN RFC 3069 support.
72 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
74 #include <linux/module.h>
75 #include <linux/types.h>
76 #include <linux/string.h>
77 #include <linux/kernel.h>
78 #include <linux/capability.h>
79 #include <linux/socket.h>
80 #include <linux/sockios.h>
81 #include <linux/errno.h>
84 #include <linux/inet.h>
85 #include <linux/inetdevice.h>
86 #include <linux/netdevice.h>
87 #include <linux/etherdevice.h>
88 #include <linux/fddidevice.h>
89 #include <linux/if_arp.h>
90 #include <linux/skbuff.h>
91 #include <linux/proc_fs.h>
92 #include <linux/seq_file.h>
93 #include <linux/stat.h>
94 #include <linux/init.h>
95 #include <linux/net.h>
96 #include <linux/rcupdate.h>
97 #include <linux/slab.h>
99 #include <linux/sysctl.h>
102 #include <net/net_namespace.h>
104 #include <net/icmp.h>
105 #include <net/route.h>
106 #include <net/protocol.h>
108 #include <net/sock.h>
110 #include <net/ax25.h>
111 #include <net/netrom.h>
112 #include <net/dst_metadata.h>
113 #include <net/ip_tunnels.h>
115 #include <linux/uaccess.h>
117 #include <linux/netfilter_arp.h>
120 * Interface to generic neighbour cache.
122 static u32 arp_hash(const void *pkey, const struct net_device *dev, __u32 *hash_rnd);
123 static bool arp_key_eq(const struct neighbour *n, const void *pkey);
124 static int arp_constructor(struct neighbour *neigh);
125 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb);
126 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb);
127 static void parp_redo(struct sk_buff *skb);
129 static const struct neigh_ops arp_generic_ops = {
131 .solicit = arp_solicit,
132 .error_report = arp_error_report,
133 .output = neigh_resolve_output,
134 .connected_output = neigh_connected_output,
137 static const struct neigh_ops arp_hh_ops = {
139 .solicit = arp_solicit,
140 .error_report = arp_error_report,
141 .output = neigh_resolve_output,
142 .connected_output = neigh_resolve_output,
145 static const struct neigh_ops arp_direct_ops = {
147 .output = neigh_direct_output,
148 .connected_output = neigh_direct_output,
151 struct neigh_table arp_tbl = {
154 .protocol = cpu_to_be16(ETH_P_IP),
156 .key_eq = arp_key_eq,
157 .constructor = arp_constructor,
158 .proxy_redo = parp_redo,
162 .reachable_time = 30 * HZ,
164 [NEIGH_VAR_MCAST_PROBES] = 3,
165 [NEIGH_VAR_UCAST_PROBES] = 3,
166 [NEIGH_VAR_RETRANS_TIME] = 1 * HZ,
167 [NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
168 [NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
169 [NEIGH_VAR_GC_STALETIME] = 60 * HZ,
170 [NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,
171 [NEIGH_VAR_PROXY_QLEN] = 64,
172 [NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
173 [NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,
174 [NEIGH_VAR_LOCKTIME] = 1 * HZ,
177 .gc_interval = 30 * HZ,
182 EXPORT_SYMBOL(arp_tbl);
184 int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
190 ip_eth_mc_map(addr, haddr);
192 case ARPHRD_INFINIBAND:
193 ip_ib_mc_map(addr, dev->broadcast, haddr);
196 ip_ipgre_mc_map(addr, dev->broadcast, haddr);
200 memcpy(haddr, dev->broadcast, dev->addr_len);
208 static u32 arp_hash(const void *pkey,
209 const struct net_device *dev,
212 return arp_hashfn(pkey, dev, hash_rnd);
215 static bool arp_key_eq(const struct neighbour *neigh, const void *pkey)
217 return neigh_key_eq32(neigh, pkey);
220 static int arp_constructor(struct neighbour *neigh)
223 struct net_device *dev = neigh->dev;
224 struct in_device *in_dev;
225 struct neigh_parms *parms;
226 u32 inaddr_any = INADDR_ANY;
228 if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
229 memcpy(neigh->primary_key, &inaddr_any, arp_tbl.key_len);
231 addr = *(__be32 *)neigh->primary_key;
233 in_dev = __in_dev_get_rcu(dev);
239 neigh->type = inet_addr_type_dev_table(dev_net(dev), dev, addr);
241 parms = in_dev->arp_parms;
242 __neigh_parms_put(neigh->parms);
243 neigh->parms = neigh_parms_clone(parms);
246 if (!dev->header_ops) {
247 neigh->nud_state = NUD_NOARP;
248 neigh->ops = &arp_direct_ops;
249 neigh->output = neigh_direct_output;
251 /* Good devices (checked by reading texts, but only Ethernet is
254 ARPHRD_ETHER: (ethernet, apfddi)
257 ARPHRD_METRICOM: (strip)
261 ARPHRD_IPDDP will also work, if author repairs it.
262 I did not it, because this driver does not work even
266 if (neigh->type == RTN_MULTICAST) {
267 neigh->nud_state = NUD_NOARP;
268 arp_mc_map(addr, neigh->ha, dev, 1);
269 } else if (dev->flags & (IFF_NOARP | IFF_LOOPBACK)) {
270 neigh->nud_state = NUD_NOARP;
271 memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
272 } else if (neigh->type == RTN_BROADCAST ||
273 (dev->flags & IFF_POINTOPOINT)) {
274 neigh->nud_state = NUD_NOARP;
275 memcpy(neigh->ha, dev->broadcast, dev->addr_len);
278 if (dev->header_ops->cache)
279 neigh->ops = &arp_hh_ops;
281 neigh->ops = &arp_generic_ops;
283 if (neigh->nud_state & NUD_VALID)
284 neigh->output = neigh->ops->connected_output;
286 neigh->output = neigh->ops->output;
291 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
293 dst_link_failure(skb);
297 /* Create and send an arp packet. */
298 static void arp_send_dst(int type, int ptype, __be32 dest_ip,
299 struct net_device *dev, __be32 src_ip,
300 const unsigned char *dest_hw,
301 const unsigned char *src_hw,
302 const unsigned char *target_hw,
303 struct dst_entry *dst)
307 /* arp on this interface. */
308 if (dev->flags & IFF_NOARP)
311 skb = arp_create(type, ptype, dest_ip, dev, src_ip,
312 dest_hw, src_hw, target_hw);
316 skb_dst_set(skb, dst_clone(dst));
320 void arp_send(int type, int ptype, __be32 dest_ip,
321 struct net_device *dev, __be32 src_ip,
322 const unsigned char *dest_hw, const unsigned char *src_hw,
323 const unsigned char *target_hw)
325 arp_send_dst(type, ptype, dest_ip, dev, src_ip, dest_hw, src_hw,
328 EXPORT_SYMBOL(arp_send);
330 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
333 u8 dst_ha[MAX_ADDR_LEN], *dst_hw = NULL;
334 struct net_device *dev = neigh->dev;
335 __be32 target = *(__be32 *)neigh->primary_key;
336 int probes = atomic_read(&neigh->probes);
337 struct in_device *in_dev;
338 struct dst_entry *dst = NULL;
341 in_dev = __in_dev_get_rcu(dev);
346 switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
348 case 0: /* By default announce any local IP */
349 if (skb && inet_addr_type_dev_table(dev_net(dev), dev,
350 ip_hdr(skb)->saddr) == RTN_LOCAL)
351 saddr = ip_hdr(skb)->saddr;
353 case 1: /* Restrict announcements of saddr in same subnet */
356 saddr = ip_hdr(skb)->saddr;
357 if (inet_addr_type_dev_table(dev_net(dev), dev,
358 saddr) == RTN_LOCAL) {
359 /* saddr should be known to target */
360 if (inet_addr_onlink(in_dev, target, saddr))
365 case 2: /* Avoid secondary IPs, get a primary/preferred one */
371 saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);
373 probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES);
375 if (!(neigh->nud_state & NUD_VALID))
376 pr_debug("trying to ucast probe in NUD_INVALID\n");
377 neigh_ha_snapshot(dst_ha, neigh, dev);
380 probes -= NEIGH_VAR(neigh->parms, APP_PROBES);
387 if (skb && !(dev->priv_flags & IFF_XMIT_DST_RELEASE))
389 arp_send_dst(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
390 dst_hw, dev->dev_addr, NULL, dst);
393 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
395 struct net *net = dev_net(in_dev->dev);
398 switch (IN_DEV_ARP_IGNORE(in_dev)) {
399 case 0: /* Reply, the tip is already validated */
401 case 1: /* Reply only if tip is configured on the incoming interface */
403 scope = RT_SCOPE_HOST;
406 * Reply only if tip is configured on the incoming interface
407 * and is in same subnet as sip
409 scope = RT_SCOPE_HOST;
411 case 3: /* Do not reply for scope host addresses */
413 scope = RT_SCOPE_LINK;
416 case 4: /* Reserved */
421 case 8: /* Do not reply */
426 return !inet_confirm_addr(net, in_dev, sip, tip, scope);
429 static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
433 /*unsigned long now; */
434 struct net *net = dev_net(dev);
436 rt = ip_route_output(net, sip, tip, 0, l3mdev_master_ifindex_rcu(dev));
439 if (rt->dst.dev != dev) {
440 __NET_INC_STATS(net, LINUX_MIB_ARPFILTER);
448 * Check if we can use proxy ARP for this path
450 static inline int arp_fwd_proxy(struct in_device *in_dev,
451 struct net_device *dev, struct rtable *rt)
453 struct in_device *out_dev;
456 if (rt->dst.dev == dev)
459 if (!IN_DEV_PROXY_ARP(in_dev))
461 imi = IN_DEV_MEDIUM_ID(in_dev);
467 /* place to check for proxy_arp for routes */
469 out_dev = __in_dev_get_rcu(rt->dst.dev);
471 omi = IN_DEV_MEDIUM_ID(out_dev);
473 return omi != imi && omi != -1;
477 * Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
479 * RFC3069 supports proxy arp replies back to the same interface. This
480 * is done to support (ethernet) switch features, like RFC 3069, where
481 * the individual ports are not allowed to communicate with each
482 * other, BUT they are allowed to talk to the upstream router. As
483 * described in RFC 3069, it is possible to allow these hosts to
484 * communicate through the upstream router, by proxy_arp'ing.
486 * RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
488 * This technology is known by different names:
489 * In RFC 3069 it is called VLAN Aggregation.
490 * Cisco and Allied Telesyn call it Private VLAN.
491 * Hewlett-Packard call it Source-Port filtering or port-isolation.
492 * Ericsson call it MAC-Forced Forwarding (RFC Draft).
495 static inline int arp_fwd_pvlan(struct in_device *in_dev,
496 struct net_device *dev, struct rtable *rt,
497 __be32 sip, __be32 tip)
499 /* Private VLAN is only concerned about the same ethernet segment */
500 if (rt->dst.dev != dev)
503 /* Don't reply on self probes (often done by windowz boxes)*/
507 if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
514 * Interface to link layer: send routine and receive handler.
518 * Create an arp packet. If dest_hw is not set, we create a broadcast
521 struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
522 struct net_device *dev, __be32 src_ip,
523 const unsigned char *dest_hw,
524 const unsigned char *src_hw,
525 const unsigned char *target_hw)
529 unsigned char *arp_ptr;
530 int hlen = LL_RESERVED_SPACE(dev);
531 int tlen = dev->needed_tailroom;
537 skb = alloc_skb(arp_hdr_len(dev) + hlen + tlen, GFP_ATOMIC);
541 skb_reserve(skb, hlen);
542 skb_reset_network_header(skb);
543 arp = skb_put(skb, arp_hdr_len(dev));
545 skb->protocol = htons(ETH_P_ARP);
547 src_hw = dev->dev_addr;
549 dest_hw = dev->broadcast;
552 * Fill the device header for the ARP frame
554 if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
558 * Fill out the arp protocol part.
560 * The arp hardware type should match the device type, except for FDDI,
561 * which (according to RFC 1390) should always equal 1 (Ethernet).
564 * Exceptions everywhere. AX.25 uses the AX.25 PID value not the
565 * DIX code for the protocol. Make these device structure fields.
569 arp->ar_hrd = htons(dev->type);
570 arp->ar_pro = htons(ETH_P_IP);
573 #if IS_ENABLED(CONFIG_AX25)
575 arp->ar_hrd = htons(ARPHRD_AX25);
576 arp->ar_pro = htons(AX25_P_IP);
579 #if IS_ENABLED(CONFIG_NETROM)
581 arp->ar_hrd = htons(ARPHRD_NETROM);
582 arp->ar_pro = htons(AX25_P_IP);
587 #if IS_ENABLED(CONFIG_FDDI)
589 arp->ar_hrd = htons(ARPHRD_ETHER);
590 arp->ar_pro = htons(ETH_P_IP);
595 arp->ar_hln = dev->addr_len;
597 arp->ar_op = htons(type);
599 arp_ptr = (unsigned char *)(arp + 1);
601 memcpy(arp_ptr, src_hw, dev->addr_len);
602 arp_ptr += dev->addr_len;
603 memcpy(arp_ptr, &src_ip, 4);
607 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
608 case ARPHRD_IEEE1394:
613 memcpy(arp_ptr, target_hw, dev->addr_len);
615 memset(arp_ptr, 0, dev->addr_len);
616 arp_ptr += dev->addr_len;
618 memcpy(arp_ptr, &dest_ip, 4);
626 EXPORT_SYMBOL(arp_create);
628 static int arp_xmit_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
630 return dev_queue_xmit(skb);
634 * Send an arp packet.
636 void arp_xmit(struct sk_buff *skb)
638 /* Send it off, maybe filter it using firewalling first. */
639 NF_HOOK(NFPROTO_ARP, NF_ARP_OUT,
640 dev_net(skb->dev), NULL, skb, NULL, skb->dev,
643 EXPORT_SYMBOL(arp_xmit);
645 static bool arp_is_garp(struct net *net, struct net_device *dev,
646 int *addr_type, __be16 ar_op,
647 __be32 sip, __be32 tip,
648 unsigned char *sha, unsigned char *tha)
650 bool is_garp = tip == sip;
652 /* Gratuitous ARP _replies_ also require target hwaddr to be
653 * the same as source.
655 if (is_garp && ar_op == htons(ARPOP_REPLY))
657 /* IPv4 over IEEE 1394 doesn't provide target
658 * hardware address field in its ARP payload.
661 !memcmp(tha, sha, dev->addr_len);
664 *addr_type = inet_addr_type_dev_table(net, dev, sip);
665 if (*addr_type != RTN_UNICAST)
672 * Process an arp request.
675 static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
677 struct net_device *dev = skb->dev;
678 struct in_device *in_dev = __in_dev_get_rcu(dev);
680 unsigned char *arp_ptr;
683 unsigned char *tha = NULL;
685 u16 dev_type = dev->type;
688 struct dst_entry *reply_dst = NULL;
689 bool is_garp = false;
691 /* arp_rcv below verifies the ARP header and verifies the device
702 if (arp->ar_pro != htons(ETH_P_IP) ||
703 htons(dev_type) != arp->ar_hrd)
710 * ETHERNET, and Fibre Channel (which are IEEE 802
711 * devices, according to RFC 2625) devices will accept ARP
712 * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
713 * This is the case also of FDDI, where the RFC 1390 says that
714 * FDDI devices should accept ARP hardware of (1) Ethernet,
715 * however, to be more robust, we'll accept both 1 (Ethernet)
718 if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
719 arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
720 arp->ar_pro != htons(ETH_P_IP))
724 if (arp->ar_pro != htons(AX25_P_IP) ||
725 arp->ar_hrd != htons(ARPHRD_AX25))
729 if (arp->ar_pro != htons(AX25_P_IP) ||
730 arp->ar_hrd != htons(ARPHRD_NETROM))
735 /* Understand only these message types */
737 if (arp->ar_op != htons(ARPOP_REPLY) &&
738 arp->ar_op != htons(ARPOP_REQUEST))
744 arp_ptr = (unsigned char *)(arp + 1);
746 arp_ptr += dev->addr_len;
747 memcpy(&sip, arp_ptr, 4);
750 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
751 case ARPHRD_IEEE1394:
756 arp_ptr += dev->addr_len;
758 memcpy(&tip, arp_ptr, 4);
760 * Check for bad requests for 127.x.x.x and requests for multicast
761 * addresses. If this is one such, delete it.
763 if (ipv4_is_multicast(tip) ||
764 (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
768 * For some 802.11 wireless deployments (and possibly other networks),
769 * there will be an ARP proxy and gratuitous ARP frames are attacks
770 * and thus should not be accepted.
772 if (sip == tip && IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP))
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 if (arp->ar_op == htons(ARPOP_REQUEST) && skb_metadata_dst(skb))
799 reply_dst = (struct dst_entry *)
800 iptunnel_metadata_reply(skb_metadata_dst(skb),
803 /* Special case: IPv4 duplicate address detection packet (RFC2131) */
805 if (arp->ar_op == htons(ARPOP_REQUEST) &&
806 inet_addr_type_dev_table(net, dev, tip) == RTN_LOCAL &&
807 !arp_ignore(in_dev, sip, tip))
808 arp_send_dst(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip,
809 sha, dev->dev_addr, sha, reply_dst);
810 goto out_consume_skb;
813 if (arp->ar_op == htons(ARPOP_REQUEST) &&
814 ip_route_input_noref(skb, tip, sip, 0, dev) == 0) {
816 rt = skb_rtable(skb);
817 addr_type = rt->rt_type;
819 if (addr_type == RTN_LOCAL) {
822 dont_send = arp_ignore(in_dev, sip, tip);
823 if (!dont_send && IN_DEV_ARPFILTER(in_dev))
824 dont_send = arp_filter(sip, tip, dev);
826 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
828 arp_send_dst(ARPOP_REPLY, ETH_P_ARP,
835 goto out_consume_skb;
836 } else if (IN_DEV_FORWARD(in_dev)) {
837 if (addr_type == RTN_UNICAST &&
838 (arp_fwd_proxy(in_dev, dev, rt) ||
839 arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
840 (rt->dst.dev != dev &&
841 pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) {
842 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
846 if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
847 skb->pkt_type == PACKET_HOST ||
848 NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) {
849 arp_send_dst(ARPOP_REPLY, ETH_P_ARP,
854 pneigh_enqueue(&arp_tbl,
855 in_dev->arp_parms, skb);
858 goto out_consume_skb;
863 /* Update our ARP tables */
865 n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
868 if (n || IN_DEV_ARP_ACCEPT(in_dev)) {
869 is_garp = arp_is_garp(net, dev, &addr_type, arp->ar_op,
873 if (IN_DEV_ARP_ACCEPT(in_dev)) {
874 /* Unsolicited ARP is not accepted by default.
875 It is possible, that this option should be enabled for some
876 devices (strip is candidate)
880 (arp->ar_op == htons(ARPOP_REPLY) &&
881 (addr_type == RTN_UNICAST ||
883 /* postpone calculation to as late as possible */
884 inet_addr_type_dev_table(net, dev, sip) ==
886 n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
890 int state = NUD_REACHABLE;
893 /* If several different ARP replies follows back-to-back,
894 use the FIRST one. It is possible, if several proxy
895 agents are active. Taking the first reply prevents
896 arp trashing and chooses the fastest router.
898 override = time_after(jiffies,
900 NEIGH_VAR(n->parms, LOCKTIME)) ||
903 /* Broadcast replies and request packets
904 do not assert neighbour reachability.
906 if (arp->ar_op != htons(ARPOP_REPLY) ||
907 skb->pkt_type != PACKET_HOST)
909 neigh_update(n, sha, state,
910 override ? NEIGH_UPDATE_F_OVERRIDE : 0, 0);
918 dst_release(reply_dst);
919 return NET_RX_SUCCESS;
926 static void parp_redo(struct sk_buff *skb)
928 arp_process(dev_net(skb->dev), NULL, skb);
933 * Receive an arp request from the device layer.
936 static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
937 struct packet_type *pt, struct net_device *orig_dev)
939 const struct arphdr *arp;
941 /* do not tweak dropwatch on an ARP we will ignore */
942 if (dev->flags & IFF_NOARP ||
943 skb->pkt_type == PACKET_OTHERHOST ||
944 skb->pkt_type == PACKET_LOOPBACK)
947 skb = skb_share_check(skb, GFP_ATOMIC);
951 /* ARP header, plus 2 device addresses, plus 2 IP addresses. */
952 if (!pskb_may_pull(skb, arp_hdr_len(dev)))
956 if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4)
959 memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
961 return NF_HOOK(NFPROTO_ARP, NF_ARP_IN,
962 dev_net(dev), NULL, skb, dev, NULL,
967 return NET_RX_SUCCESS;
975 * User level interface (ioctl)
979 * Set (create) an ARP cache entry.
982 static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
985 IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
988 if (__in_dev_get_rtnl(dev)) {
989 IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
995 static int arp_req_set_public(struct net *net, struct arpreq *r,
996 struct net_device *dev)
998 __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
999 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1001 if (mask && mask != htonl(0xFFFFFFFF))
1003 if (!dev && (r->arp_flags & ATF_COM)) {
1004 dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
1010 if (!pneigh_lookup(&arp_tbl, net, &ip, dev, 1))
1015 return arp_req_set_proxy(net, dev, 1);
1018 static int arp_req_set(struct net *net, struct arpreq *r,
1019 struct net_device *dev)
1022 struct neighbour *neigh;
1025 if (r->arp_flags & ATF_PUBL)
1026 return arp_req_set_public(net, r, dev);
1028 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1029 if (r->arp_flags & ATF_PERM)
1030 r->arp_flags |= ATF_COM;
1032 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1041 switch (dev->type) {
1042 #if IS_ENABLED(CONFIG_FDDI)
1045 * According to RFC 1390, FDDI devices should accept ARP
1046 * hardware types of 1 (Ethernet). However, to be more
1047 * robust, we'll accept hardware types of either 1 (Ethernet)
1048 * or 6 (IEEE 802.2).
1050 if (r->arp_ha.sa_family != ARPHRD_FDDI &&
1051 r->arp_ha.sa_family != ARPHRD_ETHER &&
1052 r->arp_ha.sa_family != ARPHRD_IEEE802)
1057 if (r->arp_ha.sa_family != dev->type)
1062 neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
1063 err = PTR_ERR(neigh);
1064 if (!IS_ERR(neigh)) {
1065 unsigned int state = NUD_STALE;
1066 if (r->arp_flags & ATF_PERM)
1067 state = NUD_PERMANENT;
1068 err = neigh_update(neigh, (r->arp_flags & ATF_COM) ?
1069 r->arp_ha.sa_data : NULL, state,
1070 NEIGH_UPDATE_F_OVERRIDE |
1071 NEIGH_UPDATE_F_ADMIN, 0);
1072 neigh_release(neigh);
1077 static unsigned int arp_state_to_flags(struct neighbour *neigh)
1079 if (neigh->nud_state&NUD_PERMANENT)
1080 return ATF_PERM | ATF_COM;
1081 else if (neigh->nud_state&NUD_VALID)
1088 * Get an ARP cache entry.
1091 static int arp_req_get(struct arpreq *r, struct net_device *dev)
1093 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1094 struct neighbour *neigh;
1097 neigh = neigh_lookup(&arp_tbl, &ip, dev);
1099 if (!(neigh->nud_state & NUD_NOARP)) {
1100 read_lock_bh(&neigh->lock);
1101 memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
1102 r->arp_flags = arp_state_to_flags(neigh);
1103 read_unlock_bh(&neigh->lock);
1104 r->arp_ha.sa_family = dev->type;
1105 strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
1108 neigh_release(neigh);
1113 static int arp_invalidate(struct net_device *dev, __be32 ip)
1115 struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
1117 struct neigh_table *tbl = &arp_tbl;
1120 if (neigh->nud_state & ~NUD_NOARP)
1121 err = neigh_update(neigh, NULL, NUD_FAILED,
1122 NEIGH_UPDATE_F_OVERRIDE|
1123 NEIGH_UPDATE_F_ADMIN, 0);
1124 write_lock_bh(&tbl->lock);
1125 neigh_release(neigh);
1126 neigh_remove_one(neigh, tbl);
1127 write_unlock_bh(&tbl->lock);
1133 static int arp_req_delete_public(struct net *net, struct arpreq *r,
1134 struct net_device *dev)
1136 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1137 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1139 if (mask == htonl(0xFFFFFFFF))
1140 return pneigh_delete(&arp_tbl, net, &ip, dev);
1145 return arp_req_set_proxy(net, dev, 0);
1148 static int arp_req_delete(struct net *net, struct arpreq *r,
1149 struct net_device *dev)
1153 if (r->arp_flags & ATF_PUBL)
1154 return arp_req_delete_public(net, r, dev);
1156 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1158 struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
1166 return arp_invalidate(dev, ip);
1170 * Handle an ARP layer I/O control request.
1173 int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
1177 struct net_device *dev = NULL;
1182 if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
1186 err = copy_from_user(&r, arg, sizeof(struct arpreq));
1194 if (r.arp_pa.sa_family != AF_INET)
1195 return -EPFNOSUPPORT;
1197 if (!(r.arp_flags & ATF_PUBL) &&
1198 (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
1200 if (!(r.arp_flags & ATF_NETMASK))
1201 ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
1202 htonl(0xFFFFFFFFUL);
1206 dev = __dev_get_by_name(net, r.arp_dev);
1210 /* Mmmm... It is wrong... ARPHRD_NETROM==0 */
1211 if (!r.arp_ha.sa_family)
1212 r.arp_ha.sa_family = dev->type;
1214 if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
1216 } else if (cmd == SIOCGARP) {
1223 err = arp_req_delete(net, &r, dev);
1226 err = arp_req_set(net, &r, dev);
1229 err = arp_req_get(&r, dev);
1234 if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
1239 static int arp_netdev_event(struct notifier_block *this, unsigned long event,
1242 struct net_device *dev = netdev_notifier_info_to_dev(ptr);
1243 struct netdev_notifier_change_info *change_info;
1246 case NETDEV_CHANGEADDR:
1247 neigh_changeaddr(&arp_tbl, dev);
1248 rt_cache_flush(dev_net(dev));
1252 if (change_info->flags_changed & IFF_NOARP)
1253 neigh_changeaddr(&arp_tbl, dev);
1254 if (!netif_carrier_ok(dev))
1255 neigh_carrier_down(&arp_tbl, dev);
1264 static struct notifier_block arp_netdev_notifier = {
1265 .notifier_call = arp_netdev_event,
1268 /* Note, that it is not on notifier chain.
1269 It is necessary, that this routine was called after route cache will be
1272 void arp_ifdown(struct net_device *dev)
1274 neigh_ifdown(&arp_tbl, dev);
1279 * Called once on startup.
1282 static struct packet_type arp_packet_type __read_mostly = {
1283 .type = cpu_to_be16(ETH_P_ARP),
1287 static int arp_proc_init(void);
1289 void __init arp_init(void)
1291 neigh_table_init(NEIGH_ARP_TABLE, &arp_tbl);
1293 dev_add_pack(&arp_packet_type);
1295 #ifdef CONFIG_SYSCTL
1296 neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
1298 register_netdevice_notifier(&arp_netdev_notifier);
1301 #ifdef CONFIG_PROC_FS
1302 #if IS_ENABLED(CONFIG_AX25)
1304 /* ------------------------------------------------------------------------ */
1306 * ax25 -> ASCII conversion
1308 static void ax2asc2(ax25_address *a, char *buf)
1313 for (n = 0, s = buf; n < 6; n++) {
1314 c = (a->ax25_call[n] >> 1) & 0x7F;
1321 n = (a->ax25_call[6] >> 1) & 0x0F;
1330 if (*buf == '\0' || *buf == '-') {
1335 #endif /* CONFIG_AX25 */
1337 #define HBUFFERLEN 30
1339 static void arp_format_neigh_entry(struct seq_file *seq,
1340 struct neighbour *n)
1342 char hbuffer[HBUFFERLEN];
1345 struct net_device *dev = n->dev;
1346 int hatype = dev->type;
1348 read_lock(&n->lock);
1349 /* Convert hardware address to XX:XX:XX:XX ... form. */
1350 #if IS_ENABLED(CONFIG_AX25)
1351 if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
1352 ax2asc2((ax25_address *)n->ha, hbuffer);
1355 for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
1356 hbuffer[k++] = hex_asc_hi(n->ha[j]);
1357 hbuffer[k++] = hex_asc_lo(n->ha[j]);
1363 #if IS_ENABLED(CONFIG_AX25)
1366 sprintf(tbuf, "%pI4", n->primary_key);
1367 seq_printf(seq, "%-16s 0x%-10x0x%-10x%-17s * %s\n",
1368 tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
1369 read_unlock(&n->lock);
1372 static void arp_format_pneigh_entry(struct seq_file *seq,
1373 struct pneigh_entry *n)
1375 struct net_device *dev = n->dev;
1376 int hatype = dev ? dev->type : 0;
1379 sprintf(tbuf, "%pI4", n->key);
1380 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1381 tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
1382 dev ? dev->name : "*");
1385 static int arp_seq_show(struct seq_file *seq, void *v)
1387 if (v == SEQ_START_TOKEN) {
1388 seq_puts(seq, "IP address HW type Flags "
1389 "HW address Mask Device\n");
1391 struct neigh_seq_state *state = seq->private;
1393 if (state->flags & NEIGH_SEQ_IS_PNEIGH)
1394 arp_format_pneigh_entry(seq, v);
1396 arp_format_neigh_entry(seq, v);
1402 static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
1404 /* Don't want to confuse "arp -a" w/ magic entries,
1405 * so we tell the generic iterator to skip NUD_NOARP.
1407 return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
1410 /* ------------------------------------------------------------------------ */
1412 static const struct seq_operations arp_seq_ops = {
1413 .start = arp_seq_start,
1414 .next = neigh_seq_next,
1415 .stop = neigh_seq_stop,
1416 .show = arp_seq_show,
1419 /* ------------------------------------------------------------------------ */
1421 static int __net_init arp_net_init(struct net *net)
1423 if (!proc_create_net("arp", 0444, net->proc_net, &arp_seq_ops,
1424 sizeof(struct neigh_seq_state)))
1429 static void __net_exit arp_net_exit(struct net *net)
1431 remove_proc_entry("arp", net->proc_net);
1434 static struct pernet_operations arp_net_ops = {
1435 .init = arp_net_init,
1436 .exit = arp_net_exit,
1439 static int __init arp_proc_init(void)
1441 return register_pernet_subsys(&arp_net_ops);
1444 #else /* CONFIG_PROC_FS */
1446 static int __init arp_proc_init(void)
1451 #endif /* CONFIG_PROC_FS */