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