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);
128 static int arp_is_multicast(const void *pkey);
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 = {
155 .protocol = cpu_to_be16(ETH_P_IP),
157 .key_eq = arp_key_eq,
158 .constructor = arp_constructor,
159 .proxy_redo = parp_redo,
160 .is_multicast = arp_is_multicast,
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_INTERVAL_PROBE_TIME_MS] = 5 * HZ,
172 [NEIGH_VAR_GC_STALETIME] = 60 * HZ,
173 [NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,
174 [NEIGH_VAR_PROXY_QLEN] = 64,
175 [NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
176 [NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,
177 [NEIGH_VAR_LOCKTIME] = 1 * HZ,
180 .gc_interval = 30 * HZ,
185 EXPORT_SYMBOL(arp_tbl);
187 int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
193 ip_eth_mc_map(addr, haddr);
195 case ARPHRD_INFINIBAND:
196 ip_ib_mc_map(addr, dev->broadcast, haddr);
199 ip_ipgre_mc_map(addr, dev->broadcast, haddr);
203 memcpy(haddr, dev->broadcast, dev->addr_len);
211 static u32 arp_hash(const void *pkey,
212 const struct net_device *dev,
215 return arp_hashfn(pkey, dev, hash_rnd);
218 static bool arp_key_eq(const struct neighbour *neigh, const void *pkey)
220 return neigh_key_eq32(neigh, pkey);
223 static int arp_constructor(struct neighbour *neigh)
226 struct net_device *dev = neigh->dev;
227 struct in_device *in_dev;
228 struct neigh_parms *parms;
229 u32 inaddr_any = INADDR_ANY;
231 if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
232 memcpy(neigh->primary_key, &inaddr_any, arp_tbl.key_len);
234 addr = *(__be32 *)neigh->primary_key;
236 in_dev = __in_dev_get_rcu(dev);
242 neigh->type = inet_addr_type_dev_table(dev_net(dev), dev, addr);
244 parms = in_dev->arp_parms;
245 __neigh_parms_put(neigh->parms);
246 neigh->parms = neigh_parms_clone(parms);
249 if (!dev->header_ops) {
250 neigh->nud_state = NUD_NOARP;
251 neigh->ops = &arp_direct_ops;
252 neigh->output = neigh_direct_output;
254 /* Good devices (checked by reading texts, but only Ethernet is
257 ARPHRD_ETHER: (ethernet, apfddi)
260 ARPHRD_METRICOM: (strip)
264 ARPHRD_IPDDP will also work, if author repairs it.
265 I did not it, because this driver does not work even
269 if (neigh->type == RTN_MULTICAST) {
270 neigh->nud_state = NUD_NOARP;
271 arp_mc_map(addr, neigh->ha, dev, 1);
272 } else if (dev->flags & (IFF_NOARP | IFF_LOOPBACK)) {
273 neigh->nud_state = NUD_NOARP;
274 memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
275 } else if (neigh->type == RTN_BROADCAST ||
276 (dev->flags & IFF_POINTOPOINT)) {
277 neigh->nud_state = NUD_NOARP;
278 memcpy(neigh->ha, dev->broadcast, dev->addr_len);
281 if (dev->header_ops->cache)
282 neigh->ops = &arp_hh_ops;
284 neigh->ops = &arp_generic_ops;
286 if (neigh->nud_state & NUD_VALID)
287 neigh->output = neigh->ops->connected_output;
289 neigh->output = neigh->ops->output;
294 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
296 dst_link_failure(skb);
297 kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_FAILED);
300 /* Create and send an arp packet. */
301 static void arp_send_dst(int type, int ptype, __be32 dest_ip,
302 struct net_device *dev, __be32 src_ip,
303 const unsigned char *dest_hw,
304 const unsigned char *src_hw,
305 const unsigned char *target_hw,
306 struct dst_entry *dst)
310 /* arp on this interface. */
311 if (dev->flags & IFF_NOARP)
314 skb = arp_create(type, ptype, dest_ip, dev, src_ip,
315 dest_hw, src_hw, target_hw);
319 skb_dst_set(skb, dst_clone(dst));
323 void arp_send(int type, int ptype, __be32 dest_ip,
324 struct net_device *dev, __be32 src_ip,
325 const unsigned char *dest_hw, const unsigned char *src_hw,
326 const unsigned char *target_hw)
328 arp_send_dst(type, ptype, dest_ip, dev, src_ip, dest_hw, src_hw,
331 EXPORT_SYMBOL(arp_send);
333 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
336 u8 dst_ha[MAX_ADDR_LEN], *dst_hw = NULL;
337 struct net_device *dev = neigh->dev;
338 __be32 target = *(__be32 *)neigh->primary_key;
339 int probes = atomic_read(&neigh->probes);
340 struct in_device *in_dev;
341 struct dst_entry *dst = NULL;
344 in_dev = __in_dev_get_rcu(dev);
349 switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
351 case 0: /* By default announce any local IP */
352 if (skb && inet_addr_type_dev_table(dev_net(dev), dev,
353 ip_hdr(skb)->saddr) == RTN_LOCAL)
354 saddr = ip_hdr(skb)->saddr;
356 case 1: /* Restrict announcements of saddr in same subnet */
359 saddr = ip_hdr(skb)->saddr;
360 if (inet_addr_type_dev_table(dev_net(dev), dev,
361 saddr) == RTN_LOCAL) {
362 /* saddr should be known to target */
363 if (inet_addr_onlink(in_dev, target, saddr))
368 case 2: /* Avoid secondary IPs, get a primary/preferred one */
374 saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);
376 probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES);
378 if (!(READ_ONCE(neigh->nud_state) & NUD_VALID))
379 pr_debug("trying to ucast probe in NUD_INVALID\n");
380 neigh_ha_snapshot(dst_ha, neigh, dev);
383 probes -= NEIGH_VAR(neigh->parms, APP_PROBES);
390 if (skb && !(dev->priv_flags & IFF_XMIT_DST_RELEASE))
392 arp_send_dst(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
393 dst_hw, dev->dev_addr, NULL, dst);
396 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
398 struct net *net = dev_net(in_dev->dev);
401 switch (IN_DEV_ARP_IGNORE(in_dev)) {
402 case 0: /* Reply, the tip is already validated */
404 case 1: /* Reply only if tip is configured on the incoming interface */
406 scope = RT_SCOPE_HOST;
409 * Reply only if tip is configured on the incoming interface
410 * and is in same subnet as sip
412 scope = RT_SCOPE_HOST;
414 case 3: /* Do not reply for scope host addresses */
416 scope = RT_SCOPE_LINK;
419 case 4: /* Reserved */
424 case 8: /* Do not reply */
429 return !inet_confirm_addr(net, in_dev, sip, tip, scope);
432 static int arp_accept(struct in_device *in_dev, __be32 sip)
434 struct net *net = dev_net(in_dev->dev);
435 int scope = RT_SCOPE_LINK;
437 switch (IN_DEV_ARP_ACCEPT(in_dev)) {
438 case 0: /* Don't create new entries from garp */
440 case 1: /* Create new entries from garp */
442 case 2: /* Create a neighbor in the arp table only if sip
443 * is in the same subnet as an address configured
444 * on the interface that received the garp message
446 return !!inet_confirm_addr(net, in_dev, sip, 0, scope);
452 static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
456 /*unsigned long now; */
457 struct net *net = dev_net(dev);
459 rt = ip_route_output(net, sip, tip, 0, l3mdev_master_ifindex_rcu(dev),
463 if (rt->dst.dev != dev) {
464 __NET_INC_STATS(net, LINUX_MIB_ARPFILTER);
472 * Check if we can use proxy ARP for this path
474 static inline int arp_fwd_proxy(struct in_device *in_dev,
475 struct net_device *dev, struct rtable *rt)
477 struct in_device *out_dev;
480 if (rt->dst.dev == dev)
483 if (!IN_DEV_PROXY_ARP(in_dev))
485 imi = IN_DEV_MEDIUM_ID(in_dev);
491 /* place to check for proxy_arp for routes */
493 out_dev = __in_dev_get_rcu(rt->dst.dev);
495 omi = IN_DEV_MEDIUM_ID(out_dev);
497 return omi != imi && omi != -1;
501 * Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
503 * RFC3069 supports proxy arp replies back to the same interface. This
504 * is done to support (ethernet) switch features, like RFC 3069, where
505 * the individual ports are not allowed to communicate with each
506 * other, BUT they are allowed to talk to the upstream router. As
507 * described in RFC 3069, it is possible to allow these hosts to
508 * communicate through the upstream router, by proxy_arp'ing.
510 * RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
512 * This technology is known by different names:
513 * In RFC 3069 it is called VLAN Aggregation.
514 * Cisco and Allied Telesyn call it Private VLAN.
515 * Hewlett-Packard call it Source-Port filtering or port-isolation.
516 * Ericsson call it MAC-Forced Forwarding (RFC Draft).
519 static inline int arp_fwd_pvlan(struct in_device *in_dev,
520 struct net_device *dev, struct rtable *rt,
521 __be32 sip, __be32 tip)
523 /* Private VLAN is only concerned about the same ethernet segment */
524 if (rt->dst.dev != dev)
527 /* Don't reply on self probes (often done by windowz boxes)*/
531 if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
538 * Interface to link layer: send routine and receive handler.
542 * Create an arp packet. If dest_hw is not set, we create a broadcast
545 struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
546 struct net_device *dev, __be32 src_ip,
547 const unsigned char *dest_hw,
548 const unsigned char *src_hw,
549 const unsigned char *target_hw)
553 unsigned char *arp_ptr;
554 int hlen = LL_RESERVED_SPACE(dev);
555 int tlen = dev->needed_tailroom;
561 skb = alloc_skb(arp_hdr_len(dev) + hlen + tlen, GFP_ATOMIC);
565 skb_reserve(skb, hlen);
566 skb_reset_network_header(skb);
567 arp = skb_put(skb, arp_hdr_len(dev));
569 skb->protocol = htons(ETH_P_ARP);
571 src_hw = dev->dev_addr;
573 dest_hw = dev->broadcast;
576 * Fill the device header for the ARP frame
578 if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
582 * Fill out the arp protocol part.
584 * The arp hardware type should match the device type, except for FDDI,
585 * which (according to RFC 1390) should always equal 1 (Ethernet).
588 * Exceptions everywhere. AX.25 uses the AX.25 PID value not the
589 * DIX code for the protocol. Make these device structure fields.
593 arp->ar_hrd = htons(dev->type);
594 arp->ar_pro = htons(ETH_P_IP);
597 #if IS_ENABLED(CONFIG_AX25)
599 arp->ar_hrd = htons(ARPHRD_AX25);
600 arp->ar_pro = htons(AX25_P_IP);
603 #if IS_ENABLED(CONFIG_NETROM)
605 arp->ar_hrd = htons(ARPHRD_NETROM);
606 arp->ar_pro = htons(AX25_P_IP);
611 #if IS_ENABLED(CONFIG_FDDI)
613 arp->ar_hrd = htons(ARPHRD_ETHER);
614 arp->ar_pro = htons(ETH_P_IP);
619 arp->ar_hln = dev->addr_len;
621 arp->ar_op = htons(type);
623 arp_ptr = (unsigned char *)(arp + 1);
625 memcpy(arp_ptr, src_hw, dev->addr_len);
626 arp_ptr += dev->addr_len;
627 memcpy(arp_ptr, &src_ip, 4);
631 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
632 case ARPHRD_IEEE1394:
637 memcpy(arp_ptr, target_hw, dev->addr_len);
639 memset(arp_ptr, 0, dev->addr_len);
640 arp_ptr += dev->addr_len;
642 memcpy(arp_ptr, &dest_ip, 4);
650 EXPORT_SYMBOL(arp_create);
652 static int arp_xmit_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
654 return dev_queue_xmit(skb);
658 * Send an arp packet.
660 void arp_xmit(struct sk_buff *skb)
662 /* Send it off, maybe filter it using firewalling first. */
663 NF_HOOK(NFPROTO_ARP, NF_ARP_OUT,
664 dev_net(skb->dev), NULL, skb, NULL, skb->dev,
667 EXPORT_SYMBOL(arp_xmit);
669 static bool arp_is_garp(struct net *net, struct net_device *dev,
670 int *addr_type, __be16 ar_op,
671 __be32 sip, __be32 tip,
672 unsigned char *sha, unsigned char *tha)
674 bool is_garp = tip == sip;
676 /* Gratuitous ARP _replies_ also require target hwaddr to be
677 * the same as source.
679 if (is_garp && ar_op == htons(ARPOP_REPLY))
681 /* IPv4 over IEEE 1394 doesn't provide target
682 * hardware address field in its ARP payload.
685 !memcmp(tha, sha, dev->addr_len);
688 *addr_type = inet_addr_type_dev_table(net, dev, sip);
689 if (*addr_type != RTN_UNICAST)
696 * Process an arp request.
699 static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
701 struct net_device *dev = skb->dev;
702 struct in_device *in_dev = __in_dev_get_rcu(dev);
704 unsigned char *arp_ptr;
707 unsigned char *tha = NULL;
709 u16 dev_type = dev->type;
712 struct dst_entry *reply_dst = NULL;
713 bool is_garp = false;
715 /* arp_rcv below verifies the ARP header and verifies the device
726 if (arp->ar_pro != htons(ETH_P_IP) ||
727 htons(dev_type) != arp->ar_hrd)
734 * ETHERNET, and Fibre Channel (which are IEEE 802
735 * devices, according to RFC 2625) devices will accept ARP
736 * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
737 * This is the case also of FDDI, where the RFC 1390 says that
738 * FDDI devices should accept ARP hardware of (1) Ethernet,
739 * however, to be more robust, we'll accept both 1 (Ethernet)
742 if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
743 arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
744 arp->ar_pro != htons(ETH_P_IP))
748 if (arp->ar_pro != htons(AX25_P_IP) ||
749 arp->ar_hrd != htons(ARPHRD_AX25))
753 if (arp->ar_pro != htons(AX25_P_IP) ||
754 arp->ar_hrd != htons(ARPHRD_NETROM))
759 /* Understand only these message types */
761 if (arp->ar_op != htons(ARPOP_REPLY) &&
762 arp->ar_op != htons(ARPOP_REQUEST))
768 arp_ptr = (unsigned char *)(arp + 1);
770 arp_ptr += dev->addr_len;
771 memcpy(&sip, arp_ptr, 4);
774 #if IS_ENABLED(CONFIG_FIREWIRE_NET)
775 case ARPHRD_IEEE1394:
780 arp_ptr += dev->addr_len;
782 memcpy(&tip, arp_ptr, 4);
784 * Check for bad requests for 127.x.x.x and requests for multicast
785 * addresses. If this is one such, delete it.
787 if (ipv4_is_multicast(tip) ||
788 (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
792 * For some 802.11 wireless deployments (and possibly other networks),
793 * there will be an ARP proxy and gratuitous ARP frames are attacks
794 * and thus should not be accepted.
796 if (sip == tip && IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP))
800 * Special case: We must set Frame Relay source Q.922 address
802 if (dev_type == ARPHRD_DLCI)
803 sha = dev->broadcast;
806 * Process entry. The idea here is we want to send a reply if it is a
807 * request for us or if it is a request for someone else that we hold
808 * a proxy for. We want to add an entry to our cache if it is a reply
809 * to us or if it is a request for our address.
810 * (The assumption for this last is that if someone is requesting our
811 * address, they are probably intending to talk to us, so it saves time
812 * if we cache their address. Their address is also probably not in
813 * our cache, since ours is not in their cache.)
815 * Putting this another way, we only care about replies if they are to
816 * us, in which case we add them to the cache. For requests, we care
817 * about those for us and those for our proxies. We reply to both,
818 * and in the case of requests for us we add the requester to the arp
822 if (arp->ar_op == htons(ARPOP_REQUEST) && skb_metadata_dst(skb))
823 reply_dst = (struct dst_entry *)
824 iptunnel_metadata_reply(skb_metadata_dst(skb),
827 /* Special case: IPv4 duplicate address detection packet (RFC2131) */
829 if (arp->ar_op == htons(ARPOP_REQUEST) &&
830 inet_addr_type_dev_table(net, dev, tip) == RTN_LOCAL &&
831 !arp_ignore(in_dev, sip, tip))
832 arp_send_dst(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip,
833 sha, dev->dev_addr, sha, reply_dst);
834 goto out_consume_skb;
837 if (arp->ar_op == htons(ARPOP_REQUEST) &&
838 ip_route_input_noref(skb, tip, sip, 0, dev) == 0) {
840 rt = skb_rtable(skb);
841 addr_type = rt->rt_type;
843 if (addr_type == RTN_LOCAL) {
846 dont_send = arp_ignore(in_dev, sip, tip);
847 if (!dont_send && IN_DEV_ARPFILTER(in_dev))
848 dont_send = arp_filter(sip, tip, dev);
850 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
852 arp_send_dst(ARPOP_REPLY, ETH_P_ARP,
859 goto out_consume_skb;
860 } else if (IN_DEV_FORWARD(in_dev)) {
861 if (addr_type == RTN_UNICAST &&
862 (arp_fwd_proxy(in_dev, dev, rt) ||
863 arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
864 (rt->dst.dev != dev &&
865 pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) {
866 n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
870 if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
871 skb->pkt_type == PACKET_HOST ||
872 NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) {
873 arp_send_dst(ARPOP_REPLY, ETH_P_ARP,
878 pneigh_enqueue(&arp_tbl,
879 in_dev->arp_parms, skb);
882 goto out_consume_skb;
887 /* Update our ARP tables */
889 n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
892 if (n || arp_accept(in_dev, sip)) {
893 is_garp = arp_is_garp(net, dev, &addr_type, arp->ar_op,
897 if (arp_accept(in_dev, sip)) {
898 /* Unsolicited ARP is not accepted by default.
899 It is possible, that this option should be enabled for some
900 devices (strip is candidate)
904 (arp->ar_op == htons(ARPOP_REPLY) &&
905 (addr_type == RTN_UNICAST ||
907 /* postpone calculation to as late as possible */
908 inet_addr_type_dev_table(net, dev, sip) ==
910 n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
914 int state = NUD_REACHABLE;
917 /* If several different ARP replies follows back-to-back,
918 use the FIRST one. It is possible, if several proxy
919 agents are active. Taking the first reply prevents
920 arp trashing and chooses the fastest router.
922 override = time_after(jiffies,
924 NEIGH_VAR(n->parms, LOCKTIME)) ||
927 /* Broadcast replies and request packets
928 do not assert neighbour reachability.
930 if (arp->ar_op != htons(ARPOP_REPLY) ||
931 skb->pkt_type != PACKET_HOST)
933 neigh_update(n, sha, state,
934 override ? NEIGH_UPDATE_F_OVERRIDE : 0, 0);
942 dst_release(reply_dst);
943 return NET_RX_SUCCESS;
950 static void parp_redo(struct sk_buff *skb)
952 arp_process(dev_net(skb->dev), NULL, skb);
955 static int arp_is_multicast(const void *pkey)
957 return ipv4_is_multicast(*((__be32 *)pkey));
961 * Receive an arp request from the device layer.
964 static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
965 struct packet_type *pt, struct net_device *orig_dev)
967 const struct arphdr *arp;
969 /* do not tweak dropwatch on an ARP we will ignore */
970 if (dev->flags & IFF_NOARP ||
971 skb->pkt_type == PACKET_OTHERHOST ||
972 skb->pkt_type == PACKET_LOOPBACK)
975 skb = skb_share_check(skb, GFP_ATOMIC);
979 /* ARP header, plus 2 device addresses, plus 2 IP addresses. */
980 if (!pskb_may_pull(skb, arp_hdr_len(dev)))
984 if (arp->ar_hln != dev->addr_len || arp->ar_pln != 4)
987 memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
989 return NF_HOOK(NFPROTO_ARP, NF_ARP_IN,
990 dev_net(dev), NULL, skb, dev, NULL,
995 return NET_RX_SUCCESS;
1003 * User level interface (ioctl)
1006 static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r,
1009 struct net_device *dev;
1012 dev = dev_get_by_name_rcu(net, r->arp_dev);
1014 dev = __dev_get_by_name(net, r->arp_dev);
1016 return ERR_PTR(-ENODEV);
1018 /* Mmmm... It is wrong... ARPHRD_NETROM == 0 */
1019 if (!r->arp_ha.sa_family)
1020 r->arp_ha.sa_family = dev->type;
1022 if ((r->arp_flags & ATF_COM) && r->arp_ha.sa_family != dev->type)
1023 return ERR_PTR(-EINVAL);
1028 static struct net_device *arp_req_dev(struct net *net, struct arpreq *r)
1030 struct net_device *dev;
1035 return arp_req_dev_by_name(net, r, false);
1037 if (r->arp_flags & ATF_PUBL)
1040 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1042 rt = ip_route_output(net, ip, 0, 0, 0, RT_SCOPE_LINK);
1044 return ERR_CAST(rt);
1050 return ERR_PTR(-EINVAL);
1056 * Set (create) an ARP cache entry.
1059 static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
1062 IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
1065 if (__in_dev_get_rtnl(dev)) {
1066 IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
1072 static int arp_req_set_public(struct net *net, struct arpreq *r,
1073 struct net_device *dev)
1075 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1077 if (!dev && (r->arp_flags & ATF_COM)) {
1078 dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
1084 __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1086 if (!pneigh_lookup(&arp_tbl, net, &ip, dev, 1))
1091 return arp_req_set_proxy(net, dev, 1);
1094 static int arp_req_set(struct net *net, struct arpreq *r)
1096 struct neighbour *neigh;
1097 struct net_device *dev;
1101 dev = arp_req_dev(net, r);
1103 return PTR_ERR(dev);
1105 if (r->arp_flags & ATF_PUBL)
1106 return arp_req_set_public(net, r, dev);
1108 switch (dev->type) {
1109 #if IS_ENABLED(CONFIG_FDDI)
1112 * According to RFC 1390, FDDI devices should accept ARP
1113 * hardware types of 1 (Ethernet). However, to be more
1114 * robust, we'll accept hardware types of either 1 (Ethernet)
1115 * or 6 (IEEE 802.2).
1117 if (r->arp_ha.sa_family != ARPHRD_FDDI &&
1118 r->arp_ha.sa_family != ARPHRD_ETHER &&
1119 r->arp_ha.sa_family != ARPHRD_IEEE802)
1124 if (r->arp_ha.sa_family != dev->type)
1129 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1131 neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
1132 err = PTR_ERR(neigh);
1133 if (!IS_ERR(neigh)) {
1134 unsigned int state = NUD_STALE;
1136 if (r->arp_flags & ATF_PERM) {
1137 r->arp_flags |= ATF_COM;
1138 state = NUD_PERMANENT;
1141 err = neigh_update(neigh, (r->arp_flags & ATF_COM) ?
1142 r->arp_ha.sa_data : NULL, state,
1143 NEIGH_UPDATE_F_OVERRIDE |
1144 NEIGH_UPDATE_F_ADMIN, 0);
1145 neigh_release(neigh);
1150 static unsigned int arp_state_to_flags(struct neighbour *neigh)
1152 if (neigh->nud_state&NUD_PERMANENT)
1153 return ATF_PERM | ATF_COM;
1154 else if (neigh->nud_state&NUD_VALID)
1161 * Get an ARP cache entry.
1164 static int arp_req_get(struct net *net, struct arpreq *r)
1166 __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
1167 struct neighbour *neigh;
1168 struct net_device *dev;
1173 dev = arp_req_dev_by_name(net, r, true);
1175 return PTR_ERR(dev);
1177 neigh = neigh_lookup(&arp_tbl, &ip, dev);
1181 if (READ_ONCE(neigh->nud_state) & NUD_NOARP) {
1182 neigh_release(neigh);
1186 read_lock_bh(&neigh->lock);
1187 memcpy(r->arp_ha.sa_data, neigh->ha,
1188 min(dev->addr_len, sizeof(r->arp_ha.sa_data_min)));
1189 r->arp_flags = arp_state_to_flags(neigh);
1190 read_unlock_bh(&neigh->lock);
1192 neigh_release(neigh);
1194 r->arp_ha.sa_family = dev->type;
1195 netdev_copy_name(dev, r->arp_dev);
1200 int arp_invalidate(struct net_device *dev, __be32 ip, bool force)
1202 struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
1204 struct neigh_table *tbl = &arp_tbl;
1207 if ((READ_ONCE(neigh->nud_state) & NUD_VALID) && !force) {
1208 neigh_release(neigh);
1212 if (READ_ONCE(neigh->nud_state) & ~NUD_NOARP)
1213 err = neigh_update(neigh, NULL, NUD_FAILED,
1214 NEIGH_UPDATE_F_OVERRIDE|
1215 NEIGH_UPDATE_F_ADMIN, 0);
1216 write_lock_bh(&tbl->lock);
1217 neigh_release(neigh);
1218 neigh_remove_one(neigh, tbl);
1219 write_unlock_bh(&tbl->lock);
1225 static int arp_req_delete_public(struct net *net, struct arpreq *r,
1226 struct net_device *dev)
1228 __be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
1231 __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1233 return pneigh_delete(&arp_tbl, net, &ip, dev);
1236 return arp_req_set_proxy(net, dev, 0);
1239 static int arp_req_delete(struct net *net, struct arpreq *r)
1241 struct net_device *dev;
1244 dev = arp_req_dev(net, r);
1246 return PTR_ERR(dev);
1248 if (r->arp_flags & ATF_PUBL)
1249 return arp_req_delete_public(net, r, dev);
1251 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
1253 return arp_invalidate(dev, ip, true);
1257 * Handle an ARP layer I/O control request.
1260 int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
1269 if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
1273 err = copy_from_user(&r, arg, sizeof(struct arpreq));
1281 if (r.arp_pa.sa_family != AF_INET)
1282 return -EPFNOSUPPORT;
1284 if (!(r.arp_flags & ATF_PUBL) &&
1285 (r.arp_flags & (ATF_NETMASK | ATF_DONTPUB)))
1288 netmask = &((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr;
1289 if (!(r.arp_flags & ATF_NETMASK))
1290 *netmask = htonl(0xFFFFFFFFUL);
1291 else if (*netmask && *netmask != htonl(0xFFFFFFFFUL))
1297 err = arp_req_delete(net, &r);
1302 err = arp_req_set(net, &r);
1307 err = arp_req_get(net, &r);
1310 if (!err && copy_to_user(arg, &r, sizeof(r)))
1318 static int arp_netdev_event(struct notifier_block *this, unsigned long event,
1321 struct net_device *dev = netdev_notifier_info_to_dev(ptr);
1322 struct netdev_notifier_change_info *change_info;
1323 struct in_device *in_dev;
1324 bool evict_nocarrier;
1327 case NETDEV_CHANGEADDR:
1328 neigh_changeaddr(&arp_tbl, dev);
1329 rt_cache_flush(dev_net(dev));
1333 if (change_info->flags_changed & IFF_NOARP)
1334 neigh_changeaddr(&arp_tbl, dev);
1336 in_dev = __in_dev_get_rtnl(dev);
1338 evict_nocarrier = true;
1340 evict_nocarrier = IN_DEV_ARP_EVICT_NOCARRIER(in_dev);
1342 if (evict_nocarrier && !netif_carrier_ok(dev))
1343 neigh_carrier_down(&arp_tbl, dev);
1352 static struct notifier_block arp_netdev_notifier = {
1353 .notifier_call = arp_netdev_event,
1356 /* Note, that it is not on notifier chain.
1357 It is necessary, that this routine was called after route cache will be
1360 void arp_ifdown(struct net_device *dev)
1362 neigh_ifdown(&arp_tbl, dev);
1367 * Called once on startup.
1370 static struct packet_type arp_packet_type __read_mostly = {
1371 .type = cpu_to_be16(ETH_P_ARP),
1375 #ifdef CONFIG_PROC_FS
1376 #if IS_ENABLED(CONFIG_AX25)
1379 * ax25 -> ASCII conversion
1381 static void ax2asc2(ax25_address *a, char *buf)
1386 for (n = 0, s = buf; n < 6; n++) {
1387 c = (a->ax25_call[n] >> 1) & 0x7F;
1394 n = (a->ax25_call[6] >> 1) & 0x0F;
1403 if (*buf == '\0' || *buf == '-') {
1408 #endif /* CONFIG_AX25 */
1410 #define HBUFFERLEN 30
1412 static void arp_format_neigh_entry(struct seq_file *seq,
1413 struct neighbour *n)
1415 char hbuffer[HBUFFERLEN];
1418 struct net_device *dev = n->dev;
1419 int hatype = dev->type;
1421 read_lock(&n->lock);
1422 /* Convert hardware address to XX:XX:XX:XX ... form. */
1423 #if IS_ENABLED(CONFIG_AX25)
1424 if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
1425 ax2asc2((ax25_address *)n->ha, hbuffer);
1428 for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
1429 hbuffer[k++] = hex_asc_hi(n->ha[j]);
1430 hbuffer[k++] = hex_asc_lo(n->ha[j]);
1436 #if IS_ENABLED(CONFIG_AX25)
1439 sprintf(tbuf, "%pI4", n->primary_key);
1440 seq_printf(seq, "%-16s 0x%-10x0x%-10x%-17s * %s\n",
1441 tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
1442 read_unlock(&n->lock);
1445 static void arp_format_pneigh_entry(struct seq_file *seq,
1446 struct pneigh_entry *n)
1448 struct net_device *dev = n->dev;
1449 int hatype = dev ? dev->type : 0;
1452 sprintf(tbuf, "%pI4", n->key);
1453 seq_printf(seq, "%-16s 0x%-10x0x%-10x%s * %s\n",
1454 tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
1455 dev ? dev->name : "*");
1458 static int arp_seq_show(struct seq_file *seq, void *v)
1460 if (v == SEQ_START_TOKEN) {
1461 seq_puts(seq, "IP address HW type Flags "
1462 "HW address Mask Device\n");
1464 struct neigh_seq_state *state = seq->private;
1466 if (state->flags & NEIGH_SEQ_IS_PNEIGH)
1467 arp_format_pneigh_entry(seq, v);
1469 arp_format_neigh_entry(seq, v);
1475 static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
1477 /* Don't want to confuse "arp -a" w/ magic entries,
1478 * so we tell the generic iterator to skip NUD_NOARP.
1480 return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
1483 static const struct seq_operations arp_seq_ops = {
1484 .start = arp_seq_start,
1485 .next = neigh_seq_next,
1486 .stop = neigh_seq_stop,
1487 .show = arp_seq_show,
1489 #endif /* CONFIG_PROC_FS */
1491 static int __net_init arp_net_init(struct net *net)
1493 if (!proc_create_net("arp", 0444, net->proc_net, &arp_seq_ops,
1494 sizeof(struct neigh_seq_state)))
1499 static void __net_exit arp_net_exit(struct net *net)
1501 remove_proc_entry("arp", net->proc_net);
1504 static struct pernet_operations arp_net_ops = {
1505 .init = arp_net_init,
1506 .exit = arp_net_exit,
1509 void __init arp_init(void)
1511 neigh_table_init(NEIGH_ARP_TABLE, &arp_tbl);
1513 dev_add_pack(&arp_packet_type);
1514 register_pernet_subsys(&arp_net_ops);
1515 #ifdef CONFIG_SYSCTL
1516 neigh_sysctl_register(NULL, &arp_tbl.parms, NULL);
1518 register_netdevice_notifier(&arp_netdev_notifier);