1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * IPv6 input
4 * Linux INET6 implementation
5 *
6 * Authors:
7 * Pedro Roque <roque@di.fc.ul.pt>
8 * Ian P. Morris <I.P.Morris@soton.ac.uk>
9 *
10 * Based in linux/net/ipv4/ip_input.c
11 */
12 /* Changes
13 *
14 * Mitsuru KANDA @USAGI and
15 * YOSHIFUJI Hideaki @USAGI: Remove ipv6_parse_exthdrs().
16 */
17
18 #include <linux/errno.h>
19 #include <linux/types.h>
20 #include <linux/socket.h>
21 #include <linux/sockios.h>
22 #include <linux/net.h>
23 #include <linux/netdevice.h>
24 #include <linux/in6.h>
25 #include <linux/icmpv6.h>
26 #include <linux/mroute6.h>
27 #include <linux/slab.h>
28 #include <linux/indirect_call_wrapper.h>
29
30 #include <linux/netfilter.h>
31 #include <linux/netfilter_ipv6.h>
32
33 #include <net/sock.h>
34 #include <net/snmp.h>
35 #include <net/udp.h>
36
37 #include <net/ipv6.h>
38 #include <net/protocol.h>
39 #include <net/transp_v6.h>
40 #include <net/rawv6.h>
41 #include <net/ndisc.h>
42 #include <net/ip6_route.h>
43 #include <net/addrconf.h>
44 #include <net/xfrm.h>
45 #include <net/inet_ecn.h>
46 #include <net/dst_metadata.h>
47
ip6_rcv_finish_core(struct net * net,struct sock * sk,struct sk_buff * skb)48 static void ip6_rcv_finish_core(struct net *net, struct sock *sk,
49 struct sk_buff *skb)
50 {
51 if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
52 !skb_dst(skb) && !skb->sk) {
53 switch (ipv6_hdr(skb)->nexthdr) {
54 case IPPROTO_TCP:
55 if (READ_ONCE(net->ipv4.sysctl_tcp_early_demux))
56 tcp_v6_early_demux(skb);
57 break;
58 case IPPROTO_UDP:
59 if (READ_ONCE(net->ipv4.sysctl_udp_early_demux))
60 udp_v6_early_demux(skb);
61 break;
62 }
63 }
64
65 if (!skb_valid_dst(skb))
66 ip6_route_input(skb);
67 }
68
ip6_rcv_finish(struct net * net,struct sock * sk,struct sk_buff * skb)69 int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
70 {
71 /* if ingress device is enslaved to an L3 master device pass the
72 * skb to its handler for processing
73 */
74 skb = l3mdev_ip6_rcv(skb);
75 if (!skb)
76 return NET_RX_SUCCESS;
77 ip6_rcv_finish_core(net, sk, skb);
78
79 return dst_input(skb);
80 }
81
ip6_sublist_rcv_finish(struct list_head * head)82 static void ip6_sublist_rcv_finish(struct list_head *head)
83 {
84 struct sk_buff *skb, *next;
85
86 list_for_each_entry_safe(skb, next, head, list) {
87 skb_list_del_init(skb);
88 dst_input(skb);
89 }
90 }
91
ip6_can_use_hint(const struct sk_buff * skb,const struct sk_buff * hint)92 static bool ip6_can_use_hint(const struct sk_buff *skb,
93 const struct sk_buff *hint)
94 {
95 return hint && !skb_dst(skb) &&
96 ipv6_addr_equal(&ipv6_hdr(hint)->daddr, &ipv6_hdr(skb)->daddr);
97 }
98
ip6_extract_route_hint(const struct net * net,struct sk_buff * skb)99 static struct sk_buff *ip6_extract_route_hint(const struct net *net,
100 struct sk_buff *skb)
101 {
102 if (fib6_routes_require_src(net) || fib6_has_custom_rules(net))
103 return NULL;
104
105 return skb;
106 }
107
ip6_list_rcv_finish(struct net * net,struct sock * sk,struct list_head * head)108 static void ip6_list_rcv_finish(struct net *net, struct sock *sk,
109 struct list_head *head)
110 {
111 struct sk_buff *skb, *next, *hint = NULL;
112 struct dst_entry *curr_dst = NULL;
113 struct list_head sublist;
114
115 INIT_LIST_HEAD(&sublist);
116 list_for_each_entry_safe(skb, next, head, list) {
117 struct dst_entry *dst;
118
119 skb_list_del_init(skb);
120 /* if ingress device is enslaved to an L3 master device pass the
121 * skb to its handler for processing
122 */
123 skb = l3mdev_ip6_rcv(skb);
124 if (!skb)
125 continue;
126
127 if (ip6_can_use_hint(skb, hint))
128 skb_dst_copy(skb, hint);
129 else
130 ip6_rcv_finish_core(net, sk, skb);
131 dst = skb_dst(skb);
132 if (curr_dst != dst) {
133 hint = ip6_extract_route_hint(net, skb);
134
135 /* dispatch old sublist */
136 if (!list_empty(&sublist))
137 ip6_sublist_rcv_finish(&sublist);
138 /* start new sublist */
139 INIT_LIST_HEAD(&sublist);
140 curr_dst = dst;
141 }
142 list_add_tail(&skb->list, &sublist);
143 }
144 /* dispatch final sublist */
145 ip6_sublist_rcv_finish(&sublist);
146 }
147
ip6_rcv_core(struct sk_buff * skb,struct net_device * dev,struct net * net)148 static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
149 struct net *net)
150 {
151 enum skb_drop_reason reason;
152 const struct ipv6hdr *hdr;
153 u32 pkt_len;
154 struct inet6_dev *idev;
155
156 if (skb->pkt_type == PACKET_OTHERHOST) {
157 dev_core_stats_rx_otherhost_dropped_inc(skb->dev);
158 kfree_skb_reason(skb, SKB_DROP_REASON_OTHERHOST);
159 return NULL;
160 }
161
162 rcu_read_lock();
163
164 idev = __in6_dev_get(skb->dev);
165
166 __IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
167
168 SKB_DR_SET(reason, NOT_SPECIFIED);
169 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
170 !idev || unlikely(idev->cnf.disable_ipv6)) {
171 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
172 if (idev && unlikely(idev->cnf.disable_ipv6))
173 SKB_DR_SET(reason, IPV6DISABLED);
174 goto drop;
175 }
176
177 memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
178
179 /*
180 * Store incoming device index. When the packet will
181 * be queued, we cannot refer to skb->dev anymore.
182 *
183 * BTW, when we send a packet for our own local address on a
184 * non-loopback interface (e.g. ethX), it is being delivered
185 * via the loopback interface (lo) here; skb->dev = loopback_dev.
186 * It, however, should be considered as if it is being
187 * arrived via the sending interface (ethX), because of the
188 * nature of scoping architecture. --yoshfuji
189 */
190 IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
191
192 if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
193 goto err;
194
195 hdr = ipv6_hdr(skb);
196
197 if (hdr->version != 6) {
198 SKB_DR_SET(reason, UNHANDLED_PROTO);
199 goto err;
200 }
201
202 __IP6_ADD_STATS(net, idev,
203 IPSTATS_MIB_NOECTPKTS +
204 (ipv6_get_dsfield(hdr) & INET_ECN_MASK),
205 max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
206 /*
207 * RFC4291 2.5.3
208 * The loopback address must not be used as the source address in IPv6
209 * packets that are sent outside of a single node. [..]
210 * A packet received on an interface with a destination address
211 * of loopback must be dropped.
212 */
213 if ((ipv6_addr_loopback(&hdr->saddr) ||
214 ipv6_addr_loopback(&hdr->daddr)) &&
215 !(dev->flags & IFF_LOOPBACK) &&
216 !netif_is_l3_master(dev))
217 goto err;
218
219 /* RFC4291 Errata ID: 3480
220 * Interface-Local scope spans only a single interface on a
221 * node and is useful only for loopback transmission of
222 * multicast. Packets with interface-local scope received
223 * from another node must be discarded.
224 */
225 if (!(skb->pkt_type == PACKET_LOOPBACK ||
226 dev->flags & IFF_LOOPBACK) &&
227 ipv6_addr_is_multicast(&hdr->daddr) &&
228 IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
229 goto err;
230
231 /* If enabled, drop unicast packets that were encapsulated in link-layer
232 * multicast or broadcast to protected against the so-called "hole-196"
233 * attack in 802.11 wireless.
234 */
235 if (!ipv6_addr_is_multicast(&hdr->daddr) &&
236 (skb->pkt_type == PACKET_BROADCAST ||
237 skb->pkt_type == PACKET_MULTICAST) &&
238 idev->cnf.drop_unicast_in_l2_multicast) {
239 SKB_DR_SET(reason, UNICAST_IN_L2_MULTICAST);
240 goto err;
241 }
242
243 /* RFC4291 2.7
244 * Nodes must not originate a packet to a multicast address whose scope
245 * field contains the reserved value 0; if such a packet is received, it
246 * must be silently dropped.
247 */
248 if (ipv6_addr_is_multicast(&hdr->daddr) &&
249 IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
250 goto err;
251
252 /*
253 * RFC4291 2.7
254 * Multicast addresses must not be used as source addresses in IPv6
255 * packets or appear in any Routing header.
256 */
257 if (ipv6_addr_is_multicast(&hdr->saddr))
258 goto err;
259
260 skb->transport_header = skb->network_header + sizeof(*hdr);
261 IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
262
263 pkt_len = ntohs(hdr->payload_len);
264
265 /* pkt_len may be zero if Jumbo payload option is present */
266 if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
267 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
268 __IP6_INC_STATS(net,
269 idev, IPSTATS_MIB_INTRUNCATEDPKTS);
270 SKB_DR_SET(reason, PKT_TOO_SMALL);
271 goto drop;
272 }
273 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
274 goto err;
275 hdr = ipv6_hdr(skb);
276 }
277
278 if (hdr->nexthdr == NEXTHDR_HOP) {
279 if (ipv6_parse_hopopts(skb) < 0) {
280 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
281 rcu_read_unlock();
282 return NULL;
283 }
284 }
285
286 rcu_read_unlock();
287
288 /* Must drop socket now because of tproxy. */
289 if (!skb_sk_is_prefetched(skb))
290 skb_orphan(skb);
291
292 return skb;
293 err:
294 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
295 SKB_DR_OR(reason, IP_INHDR);
296 drop:
297 rcu_read_unlock();
298 kfree_skb_reason(skb, reason);
299 return NULL;
300 }
301
ipv6_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt,struct net_device * orig_dev)302 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
303 {
304 struct net *net = dev_net(skb->dev);
305
306 skb = ip6_rcv_core(skb, dev, net);
307 if (skb == NULL)
308 return NET_RX_DROP;
309 return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
310 net, NULL, skb, dev, NULL,
311 ip6_rcv_finish);
312 }
313
ip6_sublist_rcv(struct list_head * head,struct net_device * dev,struct net * net)314 static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
315 struct net *net)
316 {
317 NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
318 head, dev, NULL, ip6_rcv_finish);
319 ip6_list_rcv_finish(net, NULL, head);
320 }
321
322 /* Receive a list of IPv6 packets */
ipv6_list_rcv(struct list_head * head,struct packet_type * pt,struct net_device * orig_dev)323 void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
324 struct net_device *orig_dev)
325 {
326 struct net_device *curr_dev = NULL;
327 struct net *curr_net = NULL;
328 struct sk_buff *skb, *next;
329 struct list_head sublist;
330
331 INIT_LIST_HEAD(&sublist);
332 list_for_each_entry_safe(skb, next, head, list) {
333 struct net_device *dev = skb->dev;
334 struct net *net = dev_net(dev);
335
336 skb_list_del_init(skb);
337 skb = ip6_rcv_core(skb, dev, net);
338 if (skb == NULL)
339 continue;
340
341 if (curr_dev != dev || curr_net != net) {
342 /* dispatch old sublist */
343 if (!list_empty(&sublist))
344 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
345 /* start new sublist */
346 INIT_LIST_HEAD(&sublist);
347 curr_dev = dev;
348 curr_net = net;
349 }
350 list_add_tail(&skb->list, &sublist);
351 }
352 /* dispatch final sublist */
353 if (!list_empty(&sublist))
354 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
355 }
356
357 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
358
359 /*
360 * Deliver the packet to the host
361 */
ip6_protocol_deliver_rcu(struct net * net,struct sk_buff * skb,int nexthdr,bool have_final)362 void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
363 bool have_final)
364 {
365 const struct inet6_protocol *ipprot;
366 struct inet6_dev *idev;
367 unsigned int nhoff;
368 SKB_DR(reason);
369 bool raw;
370
371 /*
372 * Parse extension headers
373 */
374
375 resubmit:
376 idev = ip6_dst_idev(skb_dst(skb));
377 nhoff = IP6CB(skb)->nhoff;
378 if (!have_final) {
379 if (!pskb_pull(skb, skb_transport_offset(skb)))
380 goto discard;
381 nexthdr = skb_network_header(skb)[nhoff];
382 }
383
384 resubmit_final:
385 raw = raw6_local_deliver(skb, nexthdr);
386 ipprot = rcu_dereference(inet6_protos[nexthdr]);
387 if (ipprot) {
388 int ret;
389
390 if (have_final) {
391 if (!(ipprot->flags & INET6_PROTO_FINAL)) {
392 /* Once we've seen a final protocol don't
393 * allow encapsulation on any non-final
394 * ones. This allows foo in UDP encapsulation
395 * to work.
396 */
397 goto discard;
398 }
399 } else if (ipprot->flags & INET6_PROTO_FINAL) {
400 const struct ipv6hdr *hdr;
401 int sdif = inet6_sdif(skb);
402 struct net_device *dev;
403
404 /* Only do this once for first final protocol */
405 have_final = true;
406
407 /* Free reference early: we don't need it any more,
408 and it may hold ip_conntrack module loaded
409 indefinitely. */
410 nf_reset_ct(skb);
411
412 skb_postpull_rcsum(skb, skb_network_header(skb),
413 skb_network_header_len(skb));
414 hdr = ipv6_hdr(skb);
415
416 /* skb->dev passed may be master dev for vrfs. */
417 if (sdif) {
418 dev = dev_get_by_index_rcu(net, sdif);
419 if (!dev)
420 goto discard;
421 } else {
422 dev = skb->dev;
423 }
424
425 if (ipv6_addr_is_multicast(&hdr->daddr) &&
426 !ipv6_chk_mcast_addr(dev, &hdr->daddr,
427 &hdr->saddr) &&
428 !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb))) {
429 SKB_DR_SET(reason, IP_INADDRERRORS);
430 goto discard;
431 }
432 }
433 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
434 !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
435 SKB_DR_SET(reason, XFRM_POLICY);
436 goto discard;
437 }
438
439 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
440 skb);
441 if (ret > 0) {
442 if (ipprot->flags & INET6_PROTO_FINAL) {
443 /* Not an extension header, most likely UDP
444 * encapsulation. Use return value as nexthdr
445 * protocol not nhoff (which presumably is
446 * not set by handler).
447 */
448 nexthdr = ret;
449 goto resubmit_final;
450 } else {
451 goto resubmit;
452 }
453 } else if (ret == 0) {
454 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
455 }
456 } else {
457 if (!raw) {
458 if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
459 __IP6_INC_STATS(net, idev,
460 IPSTATS_MIB_INUNKNOWNPROTOS);
461 icmpv6_send(skb, ICMPV6_PARAMPROB,
462 ICMPV6_UNK_NEXTHDR, nhoff);
463 SKB_DR_SET(reason, IP_NOPROTO);
464 } else {
465 SKB_DR_SET(reason, XFRM_POLICY);
466 }
467 kfree_skb_reason(skb, reason);
468 } else {
469 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
470 consume_skb(skb);
471 }
472 }
473 return;
474
475 discard:
476 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
477 kfree_skb_reason(skb, reason);
478 }
479
ip6_input_finish(struct net * net,struct sock * sk,struct sk_buff * skb)480 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
481 {
482 skb_clear_delivery_time(skb);
483 rcu_read_lock();
484 ip6_protocol_deliver_rcu(net, skb, 0, false);
485 rcu_read_unlock();
486
487 return 0;
488 }
489
490
ip6_input(struct sk_buff * skb)491 int ip6_input(struct sk_buff *skb)
492 {
493 return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
494 dev_net(skb->dev), NULL, skb, skb->dev, NULL,
495 ip6_input_finish);
496 }
497 EXPORT_SYMBOL_GPL(ip6_input);
498
ip6_mc_input(struct sk_buff * skb)499 int ip6_mc_input(struct sk_buff *skb)
500 {
501 int sdif = inet6_sdif(skb);
502 const struct ipv6hdr *hdr;
503 struct net_device *dev;
504 bool deliver;
505
506 __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
507 __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
508 skb->len);
509
510 /* skb->dev passed may be master dev for vrfs. */
511 if (sdif) {
512 rcu_read_lock();
513 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
514 if (!dev) {
515 rcu_read_unlock();
516 kfree_skb(skb);
517 return -ENODEV;
518 }
519 } else {
520 dev = skb->dev;
521 }
522
523 hdr = ipv6_hdr(skb);
524 deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
525 if (sdif)
526 rcu_read_unlock();
527
528 #ifdef CONFIG_IPV6_MROUTE
529 /*
530 * IPv6 multicast router mode is now supported ;)
531 */
532 if (atomic_read(&dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding) &&
533 !(ipv6_addr_type(&hdr->daddr) &
534 (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
535 likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
536 /*
537 * Okay, we try to forward - split and duplicate
538 * packets.
539 */
540 struct sk_buff *skb2;
541 struct inet6_skb_parm *opt = IP6CB(skb);
542
543 /* Check for MLD */
544 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
545 /* Check if this is a mld message */
546 u8 nexthdr = hdr->nexthdr;
547 __be16 frag_off;
548 int offset;
549
550 /* Check if the value of Router Alert
551 * is for MLD (0x0000).
552 */
553 if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
554 deliver = false;
555
556 if (!ipv6_ext_hdr(nexthdr)) {
557 /* BUG */
558 goto out;
559 }
560 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
561 &nexthdr, &frag_off);
562 if (offset < 0)
563 goto out;
564
565 if (ipv6_is_mld(skb, nexthdr, offset))
566 deliver = true;
567
568 goto out;
569 }
570 /* unknown RA - process it normally */
571 }
572
573 if (deliver)
574 skb2 = skb_clone(skb, GFP_ATOMIC);
575 else {
576 skb2 = skb;
577 skb = NULL;
578 }
579
580 if (skb2) {
581 ip6_mr_input(skb2);
582 }
583 }
584 out:
585 #endif
586 if (likely(deliver))
587 ip6_input(skb);
588 else {
589 /* discard */
590 kfree_skb(skb);
591 }
592
593 return 0;
594 }
595