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Linux/net/ipv6/ip6_input.c

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  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 INDIRECT_CALLABLE_DECLARE(void udp_v6_early_demux(struct sk_buff *));
 48 INDIRECT_CALLABLE_DECLARE(void tcp_v6_early_demux(struct sk_buff *));
 49 static void ip6_rcv_finish_core(struct net *net, struct sock *sk,
 50                                 struct sk_buff *skb)
 51 {
 52         void (*edemux)(struct sk_buff *skb);
 53 
 54         if (net->ipv4.sysctl_ip_early_demux && !skb_dst(skb) && skb->sk == NULL) {
 55                 const struct inet6_protocol *ipprot;
 56 
 57                 ipprot = rcu_dereference(inet6_protos[ipv6_hdr(skb)->nexthdr]);
 58                 if (ipprot && (edemux = READ_ONCE(ipprot->early_demux)))
 59                         INDIRECT_CALL_2(edemux, tcp_v6_early_demux,
 60                                         udp_v6_early_demux, skb);
 61         }
 62         if (!skb_valid_dst(skb))
 63                 ip6_route_input(skb);
 64 }
 65 
 66 int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 67 {
 68         /* if ingress device is enslaved to an L3 master device pass the
 69          * skb to its handler for processing
 70          */
 71         skb = l3mdev_ip6_rcv(skb);
 72         if (!skb)
 73                 return NET_RX_SUCCESS;
 74         ip6_rcv_finish_core(net, sk, skb);
 75 
 76         return dst_input(skb);
 77 }
 78 
 79 static void ip6_sublist_rcv_finish(struct list_head *head)
 80 {
 81         struct sk_buff *skb, *next;
 82 
 83         list_for_each_entry_safe(skb, next, head, list) {
 84                 skb_list_del_init(skb);
 85                 dst_input(skb);
 86         }
 87 }
 88 
 89 static bool ip6_can_use_hint(const struct sk_buff *skb,
 90                              const struct sk_buff *hint)
 91 {
 92         return hint && !skb_dst(skb) &&
 93                ipv6_addr_equal(&ipv6_hdr(hint)->daddr, &ipv6_hdr(skb)->daddr);
 94 }
 95 
 96 static struct sk_buff *ip6_extract_route_hint(const struct net *net,
 97                                               struct sk_buff *skb)
 98 {
 99         if (fib6_routes_require_src(net) || fib6_has_custom_rules(net))
100                 return NULL;
101 
102         return skb;
103 }
104 
105 static void ip6_list_rcv_finish(struct net *net, struct sock *sk,
106                                 struct list_head *head)
107 {
108         struct sk_buff *skb, *next, *hint = NULL;
109         struct dst_entry *curr_dst = NULL;
110         struct list_head sublist;
111 
112         INIT_LIST_HEAD(&sublist);
113         list_for_each_entry_safe(skb, next, head, list) {
114                 struct dst_entry *dst;
115 
116                 skb_list_del_init(skb);
117                 /* if ingress device is enslaved to an L3 master device pass the
118                  * skb to its handler for processing
119                  */
120                 skb = l3mdev_ip6_rcv(skb);
121                 if (!skb)
122                         continue;
123 
124                 if (ip6_can_use_hint(skb, hint))
125                         skb_dst_copy(skb, hint);
126                 else
127                         ip6_rcv_finish_core(net, sk, skb);
128                 dst = skb_dst(skb);
129                 if (curr_dst != dst) {
130                         hint = ip6_extract_route_hint(net, skb);
131 
132                         /* dispatch old sublist */
133                         if (!list_empty(&sublist))
134                                 ip6_sublist_rcv_finish(&sublist);
135                         /* start new sublist */
136                         INIT_LIST_HEAD(&sublist);
137                         curr_dst = dst;
138                 }
139                 list_add_tail(&skb->list, &sublist);
140         }
141         /* dispatch final sublist */
142         ip6_sublist_rcv_finish(&sublist);
143 }
144 
145 static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
146                                     struct net *net)
147 {
148         const struct ipv6hdr *hdr;
149         u32 pkt_len;
150         struct inet6_dev *idev;
151 
152         if (skb->pkt_type == PACKET_OTHERHOST) {
153                 kfree_skb(skb);
154                 return NULL;
155         }
156 
157         rcu_read_lock();
158 
159         idev = __in6_dev_get(skb->dev);
160 
161         __IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
162 
163         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
164             !idev || unlikely(idev->cnf.disable_ipv6)) {
165                 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
166                 goto drop;
167         }
168 
169         memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
170 
171         /*
172          * Store incoming device index. When the packet will
173          * be queued, we cannot refer to skb->dev anymore.
174          *
175          * BTW, when we send a packet for our own local address on a
176          * non-loopback interface (e.g. ethX), it is being delivered
177          * via the loopback interface (lo) here; skb->dev = loopback_dev.
178          * It, however, should be considered as if it is being
179          * arrived via the sending interface (ethX), because of the
180          * nature of scoping architecture. --yoshfuji
181          */
182         IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
183 
184         if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
185                 goto err;
186 
187         hdr = ipv6_hdr(skb);
188 
189         if (hdr->version != 6)
190                 goto err;
191 
192         __IP6_ADD_STATS(net, idev,
193                         IPSTATS_MIB_NOECTPKTS +
194                                 (ipv6_get_dsfield(hdr) & INET_ECN_MASK),
195                         max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
196         /*
197          * RFC4291 2.5.3
198          * The loopback address must not be used as the source address in IPv6
199          * packets that are sent outside of a single node. [..]
200          * A packet received on an interface with a destination address
201          * of loopback must be dropped.
202          */
203         if ((ipv6_addr_loopback(&hdr->saddr) ||
204              ipv6_addr_loopback(&hdr->daddr)) &&
205             !(dev->flags & IFF_LOOPBACK) &&
206             !netif_is_l3_master(dev))
207                 goto err;
208 
209         /* RFC4291 Errata ID: 3480
210          * Interface-Local scope spans only a single interface on a
211          * node and is useful only for loopback transmission of
212          * multicast.  Packets with interface-local scope received
213          * from another node must be discarded.
214          */
215         if (!(skb->pkt_type == PACKET_LOOPBACK ||
216               dev->flags & IFF_LOOPBACK) &&
217             ipv6_addr_is_multicast(&hdr->daddr) &&
218             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
219                 goto err;
220 
221         /* If enabled, drop unicast packets that were encapsulated in link-layer
222          * multicast or broadcast to protected against the so-called "hole-196"
223          * attack in 802.11 wireless.
224          */
225         if (!ipv6_addr_is_multicast(&hdr->daddr) &&
226             (skb->pkt_type == PACKET_BROADCAST ||
227              skb->pkt_type == PACKET_MULTICAST) &&
228             idev->cnf.drop_unicast_in_l2_multicast)
229                 goto err;
230 
231         /* RFC4291 2.7
232          * Nodes must not originate a packet to a multicast address whose scope
233          * field contains the reserved value 0; if such a packet is received, it
234          * must be silently dropped.
235          */
236         if (ipv6_addr_is_multicast(&hdr->daddr) &&
237             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
238                 goto err;
239 
240         /*
241          * RFC4291 2.7
242          * Multicast addresses must not be used as source addresses in IPv6
243          * packets or appear in any Routing header.
244          */
245         if (ipv6_addr_is_multicast(&hdr->saddr))
246                 goto err;
247 
248         /* While RFC4291 is not explicit about v4mapped addresses
249          * in IPv6 headers, it seems clear linux dual-stack
250          * model can not deal properly with these.
251          * Security models could be fooled by ::ffff:127.0.0.1 for example.
252          *
253          * https://tools.ietf.org/html/draft-itojun-v6ops-v4mapped-harmful-02
254          */
255         if (ipv6_addr_v4mapped(&hdr->saddr))
256                 goto err;
257 
258         skb->transport_header = skb->network_header + sizeof(*hdr);
259         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
260 
261         pkt_len = ntohs(hdr->payload_len);
262 
263         /* pkt_len may be zero if Jumbo payload option is present */
264         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
265                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
266                         __IP6_INC_STATS(net,
267                                         idev, IPSTATS_MIB_INTRUNCATEDPKTS);
268                         goto drop;
269                 }
270                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
271                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
272                         goto drop;
273                 }
274                 hdr = ipv6_hdr(skb);
275         }
276 
277         if (hdr->nexthdr == NEXTHDR_HOP) {
278                 if (ipv6_parse_hopopts(skb) < 0) {
279                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
280                         rcu_read_unlock();
281                         return NULL;
282                 }
283         }
284 
285         rcu_read_unlock();
286 
287         /* Must drop socket now because of tproxy. */
288         if (!skb_sk_is_prefetched(skb))
289                 skb_orphan(skb);
290 
291         return skb;
292 err:
293         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
294 drop:
295         rcu_read_unlock();
296         kfree_skb(skb);
297         return NULL;
298 }
299 
300 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
301 {
302         struct net *net = dev_net(skb->dev);
303 
304         skb = ip6_rcv_core(skb, dev, net);
305         if (skb == NULL)
306                 return NET_RX_DROP;
307         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
308                        net, NULL, skb, dev, NULL,
309                        ip6_rcv_finish);
310 }
311 
312 static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
313                             struct net *net)
314 {
315         NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
316                      head, dev, NULL, ip6_rcv_finish);
317         ip6_list_rcv_finish(net, NULL, head);
318 }
319 
320 /* Receive a list of IPv6 packets */
321 void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
322                    struct net_device *orig_dev)
323 {
324         struct net_device *curr_dev = NULL;
325         struct net *curr_net = NULL;
326         struct sk_buff *skb, *next;
327         struct list_head sublist;
328 
329         INIT_LIST_HEAD(&sublist);
330         list_for_each_entry_safe(skb, next, head, list) {
331                 struct net_device *dev = skb->dev;
332                 struct net *net = dev_net(dev);
333 
334                 skb_list_del_init(skb);
335                 skb = ip6_rcv_core(skb, dev, net);
336                 if (skb == NULL)
337                         continue;
338 
339                 if (curr_dev != dev || curr_net != net) {
340                         /* dispatch old sublist */
341                         if (!list_empty(&sublist))
342                                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
343                         /* start new sublist */
344                         INIT_LIST_HEAD(&sublist);
345                         curr_dev = dev;
346                         curr_net = net;
347                 }
348                 list_add_tail(&skb->list, &sublist);
349         }
350         /* dispatch final sublist */
351         if (!list_empty(&sublist))
352                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
353 }
354 
355 INDIRECT_CALLABLE_DECLARE(int udpv6_rcv(struct sk_buff *));
356 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
357 
358 /*
359  *      Deliver the packet to the host
360  */
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         bool raw;
368 
369         /*
370          *      Parse extension headers
371          */
372 
373 resubmit:
374         idev = ip6_dst_idev(skb_dst(skb));
375         nhoff = IP6CB(skb)->nhoff;
376         if (!have_final) {
377                 if (!pskb_pull(skb, skb_transport_offset(skb)))
378                         goto discard;
379                 nexthdr = skb_network_header(skb)[nhoff];
380         }
381 
382 resubmit_final:
383         raw = raw6_local_deliver(skb, nexthdr);
384         ipprot = rcu_dereference(inet6_protos[nexthdr]);
385         if (ipprot) {
386                 int ret;
387 
388                 if (have_final) {
389                         if (!(ipprot->flags & INET6_PROTO_FINAL)) {
390                                 /* Once we've seen a final protocol don't
391                                  * allow encapsulation on any non-final
392                                  * ones. This allows foo in UDP encapsulation
393                                  * to work.
394                                  */
395                                 goto discard;
396                         }
397                 } else if (ipprot->flags & INET6_PROTO_FINAL) {
398                         const struct ipv6hdr *hdr;
399                         int sdif = inet6_sdif(skb);
400                         struct net_device *dev;
401 
402                         /* Only do this once for first final protocol */
403                         have_final = true;
404 
405                         /* Free reference early: we don't need it any more,
406                            and it may hold ip_conntrack module loaded
407                            indefinitely. */
408                         nf_reset_ct(skb);
409 
410                         skb_postpull_rcsum(skb, skb_network_header(skb),
411                                            skb_network_header_len(skb));
412                         hdr = ipv6_hdr(skb);
413 
414                         /* skb->dev passed may be master dev for vrfs. */
415                         if (sdif) {
416                                 dev = dev_get_by_index_rcu(net, sdif);
417                                 if (!dev)
418                                         goto discard;
419                         } else {
420                                 dev = skb->dev;
421                         }
422 
423                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
424                             !ipv6_chk_mcast_addr(dev, &hdr->daddr,
425                                                  &hdr->saddr) &&
426                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
427                                 goto discard;
428                 }
429                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
430                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
431                         goto discard;
432 
433                 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
434                                       skb);
435                 if (ret > 0) {
436                         if (ipprot->flags & INET6_PROTO_FINAL) {
437                                 /* Not an extension header, most likely UDP
438                                  * encapsulation. Use return value as nexthdr
439                                  * protocol not nhoff (which presumably is
440                                  * not set by handler).
441                                  */
442                                 nexthdr = ret;
443                                 goto resubmit_final;
444                         } else {
445                                 goto resubmit;
446                         }
447                 } else if (ret == 0) {
448                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
449                 }
450         } else {
451                 if (!raw) {
452                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
453                                 __IP6_INC_STATS(net, idev,
454                                                 IPSTATS_MIB_INUNKNOWNPROTOS);
455                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
456                                             ICMPV6_UNK_NEXTHDR, nhoff);
457                         }
458                         kfree_skb(skb);
459                 } else {
460                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
461                         consume_skb(skb);
462                 }
463         }
464         return;
465 
466 discard:
467         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
468         kfree_skb(skb);
469 }
470 
471 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
472 {
473         rcu_read_lock();
474         ip6_protocol_deliver_rcu(net, skb, 0, false);
475         rcu_read_unlock();
476 
477         return 0;
478 }
479 
480 
481 int ip6_input(struct sk_buff *skb)
482 {
483         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
484                        dev_net(skb->dev), NULL, skb, skb->dev, NULL,
485                        ip6_input_finish);
486 }
487 EXPORT_SYMBOL_GPL(ip6_input);
488 
489 int ip6_mc_input(struct sk_buff *skb)
490 {
491         int sdif = inet6_sdif(skb);
492         const struct ipv6hdr *hdr;
493         struct net_device *dev;
494         bool deliver;
495 
496         __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
497                          __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
498                          skb->len);
499 
500         /* skb->dev passed may be master dev for vrfs. */
501         if (sdif) {
502                 rcu_read_lock();
503                 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
504                 if (!dev) {
505                         rcu_read_unlock();
506                         kfree_skb(skb);
507                         return -ENODEV;
508                 }
509         } else {
510                 dev = skb->dev;
511         }
512 
513         hdr = ipv6_hdr(skb);
514         deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
515         if (sdif)
516                 rcu_read_unlock();
517 
518 #ifdef CONFIG_IPV6_MROUTE
519         /*
520          *      IPv6 multicast router mode is now supported ;)
521          */
522         if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
523             !(ipv6_addr_type(&hdr->daddr) &
524               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
525             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
526                 /*
527                  * Okay, we try to forward - split and duplicate
528                  * packets.
529                  */
530                 struct sk_buff *skb2;
531                 struct inet6_skb_parm *opt = IP6CB(skb);
532 
533                 /* Check for MLD */
534                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
535                         /* Check if this is a mld message */
536                         u8 nexthdr = hdr->nexthdr;
537                         __be16 frag_off;
538                         int offset;
539 
540                         /* Check if the value of Router Alert
541                          * is for MLD (0x0000).
542                          */
543                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
544                                 deliver = false;
545 
546                                 if (!ipv6_ext_hdr(nexthdr)) {
547                                         /* BUG */
548                                         goto out;
549                                 }
550                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
551                                                           &nexthdr, &frag_off);
552                                 if (offset < 0)
553                                         goto out;
554 
555                                 if (ipv6_is_mld(skb, nexthdr, offset))
556                                         deliver = true;
557 
558                                 goto out;
559                         }
560                         /* unknown RA - process it normally */
561                 }
562 
563                 if (deliver)
564                         skb2 = skb_clone(skb, GFP_ATOMIC);
565                 else {
566                         skb2 = skb;
567                         skb = NULL;
568                 }
569 
570                 if (skb2) {
571                         ip6_mr_input(skb2);
572                 }
573         }
574 out:
575 #endif
576         if (likely(deliver))
577                 ip6_input(skb);
578         else {
579                 /* discard */
580                 kfree_skb(skb);
581         }
582 
583         return 0;
584 }
585 

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