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 IP6CB(skb)->flags & IP6SKB_MULTIPATH)
104 return NULL;
105
106 return skb;
107 }
108
ip6_list_rcv_finish(struct net * net,struct sock * sk,struct list_head * head)109 static void ip6_list_rcv_finish(struct net *net, struct sock *sk,
110 struct list_head *head)
111 {
112 struct sk_buff *skb, *next, *hint = NULL;
113 struct dst_entry *curr_dst = NULL;
114 LIST_HEAD(sublist);
115
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(READ_ONCE(idev->cnf.disable_ipv6))) {
171 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
172 if (idev && unlikely(READ_ONCE(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 READ_ONCE(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 LIST_HEAD(sublist);
330
331 list_for_each_entry_safe(skb, next, head, list) {
332 struct net_device *dev = skb->dev;
333 struct net *net = dev_net(dev);
334
335 skb_list_del_init(skb);
336 skb = ip6_rcv_core(skb, dev, net);
337 if (skb == NULL)
338 continue;
339
340 if (curr_dev != dev || curr_net != net) {
341 /* dispatch old sublist */
342 if (!list_empty(&sublist))
343 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
344 /* start new sublist */
345 INIT_LIST_HEAD(&sublist);
346 curr_dev = dev;
347 curr_net = net;
348 }
349 list_add_tail(&skb->list, &sublist);
350 }
351 /* dispatch final sublist */
352 if (!list_empty(&sublist))
353 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
354 }
355
356 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
357
358 /*
359 * Deliver the packet to the host
360 */
ip6_protocol_deliver_rcu(struct net * net,struct sk_buff * skb,int nexthdr,bool have_final)361 void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
362 bool have_final)
363 {
364 const struct inet6_protocol *ipprot;
365 struct inet6_dev *idev;
366 unsigned int nhoff;
367 SKB_DR(reason);
368 bool raw;
369
370 /*
371 * Parse extension headers
372 */
373
374 resubmit:
375 idev = ip6_dst_idev(skb_dst(skb));
376 nhoff = IP6CB(skb)->nhoff;
377 if (!have_final) {
378 if (!pskb_pull(skb, skb_transport_offset(skb)))
379 goto discard;
380 nexthdr = skb_network_header(skb)[nhoff];
381 }
382
383 resubmit_final:
384 raw = raw6_local_deliver(skb, nexthdr);
385 ipprot = rcu_dereference(inet6_protos[nexthdr]);
386 if (ipprot) {
387 int ret;
388
389 if (have_final) {
390 if (!(ipprot->flags & INET6_PROTO_FINAL)) {
391 /* Once we've seen a final protocol don't
392 * allow encapsulation on any non-final
393 * ones. This allows foo in UDP encapsulation
394 * to work.
395 */
396 goto discard;
397 }
398 } else if (ipprot->flags & INET6_PROTO_FINAL) {
399 const struct ipv6hdr *hdr;
400 int sdif = inet6_sdif(skb);
401 struct net_device *dev;
402
403 /* Only do this once for first final protocol */
404 have_final = true;
405
406
407 skb_postpull_rcsum(skb, skb_network_header(skb),
408 skb_network_header_len(skb));
409 hdr = ipv6_hdr(skb);
410
411 /* skb->dev passed may be master dev for vrfs. */
412 if (sdif) {
413 dev = dev_get_by_index_rcu(net, sdif);
414 if (!dev)
415 goto discard;
416 } else {
417 dev = skb->dev;
418 }
419
420 if (ipv6_addr_is_multicast(&hdr->daddr) &&
421 !ipv6_chk_mcast_addr(dev, &hdr->daddr,
422 &hdr->saddr) &&
423 !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb))) {
424 SKB_DR_SET(reason, IP_INADDRERRORS);
425 goto discard;
426 }
427 }
428 if (!(ipprot->flags & INET6_PROTO_NOPOLICY)) {
429 if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
430 SKB_DR_SET(reason, XFRM_POLICY);
431 goto discard;
432 }
433 nf_reset_ct(skb);
434 }
435
436 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
437 skb);
438 if (ret > 0) {
439 if (ipprot->flags & INET6_PROTO_FINAL) {
440 /* Not an extension header, most likely UDP
441 * encapsulation. Use return value as nexthdr
442 * protocol not nhoff (which presumably is
443 * not set by handler).
444 */
445 nexthdr = ret;
446 goto resubmit_final;
447 } else {
448 goto resubmit;
449 }
450 } else if (ret == 0) {
451 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
452 }
453 } else {
454 if (!raw) {
455 if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
456 __IP6_INC_STATS(net, idev,
457 IPSTATS_MIB_INUNKNOWNPROTOS);
458 icmpv6_send(skb, ICMPV6_PARAMPROB,
459 ICMPV6_UNK_NEXTHDR, nhoff);
460 SKB_DR_SET(reason, IP_NOPROTO);
461 } else {
462 SKB_DR_SET(reason, XFRM_POLICY);
463 }
464 kfree_skb_reason(skb, reason);
465 } else {
466 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
467 consume_skb(skb);
468 }
469 }
470 return;
471
472 discard:
473 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
474 kfree_skb_reason(skb, reason);
475 }
476
ip6_input_finish(struct net * net,struct sock * sk,struct sk_buff * skb)477 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
478 {
479 skb_clear_delivery_time(skb);
480 rcu_read_lock();
481 ip6_protocol_deliver_rcu(net, skb, 0, false);
482 rcu_read_unlock();
483
484 return 0;
485 }
486
487
ip6_input(struct sk_buff * skb)488 int ip6_input(struct sk_buff *skb)
489 {
490 return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
491 dev_net(skb->dev), NULL, skb, skb->dev, NULL,
492 ip6_input_finish);
493 }
494 EXPORT_SYMBOL_GPL(ip6_input);
495
ip6_mc_input(struct sk_buff * skb)496 int ip6_mc_input(struct sk_buff *skb)
497 {
498 int sdif = inet6_sdif(skb);
499 const struct ipv6hdr *hdr;
500 struct net_device *dev;
501 bool deliver;
502
503 __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
504 __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
505 skb->len);
506
507 /* skb->dev passed may be master dev for vrfs. */
508 if (sdif) {
509 rcu_read_lock();
510 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
511 if (!dev) {
512 rcu_read_unlock();
513 kfree_skb(skb);
514 return -ENODEV;
515 }
516 } else {
517 dev = skb->dev;
518 }
519
520 hdr = ipv6_hdr(skb);
521 deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
522 if (sdif)
523 rcu_read_unlock();
524
525 #ifdef CONFIG_IPV6_MROUTE
526 /*
527 * IPv6 multicast router mode is now supported ;)
528 */
529 if (atomic_read(&dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding) &&
530 !(ipv6_addr_type(&hdr->daddr) &
531 (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
532 likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
533 /*
534 * Okay, we try to forward - split and duplicate
535 * packets.
536 */
537 struct sk_buff *skb2;
538 struct inet6_skb_parm *opt = IP6CB(skb);
539
540 /* Check for MLD */
541 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
542 /* Check if this is a mld message */
543 u8 nexthdr = hdr->nexthdr;
544 __be16 frag_off;
545 int offset;
546
547 /* Check if the value of Router Alert
548 * is for MLD (0x0000).
549 */
550 if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
551 deliver = false;
552
553 if (!ipv6_ext_hdr(nexthdr)) {
554 /* BUG */
555 goto out;
556 }
557 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
558 &nexthdr, &frag_off);
559 if (offset < 0)
560 goto out;
561
562 if (ipv6_is_mld(skb, nexthdr, offset))
563 deliver = true;
564
565 goto out;
566 }
567 /* unknown RA - process it normally */
568 }
569
570 if (deliver)
571 skb2 = skb_clone(skb, GFP_ATOMIC);
572 else {
573 skb2 = skb;
574 skb = NULL;
575 }
576
577 if (skb2) {
578 ip6_mr_input(skb2);
579 }
580 }
581 out:
582 #endif
583 if (likely(deliver))
584 ip6_input(skb);
585 else {
586 /* discard */
587 kfree_skb(skb);
588 }
589
590 return 0;
591 }
592