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TOMOYO Linux Cross Reference
Linux/net/ipv6/ip6_input.c

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

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