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Linux/net/ipv6/ip6_input.c

  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 int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 51 {
 52         /* if ingress device is enslaved to an L3 master device pass the
 53          * skb to its handler for processing
 54          */
 55         skb = l3mdev_ip6_rcv(skb);
 56         if (!skb)
 57                 return NET_RX_SUCCESS;
 58 
 59         if (net->ipv4.sysctl_ip_early_demux && !skb_dst(skb) && skb->sk == NULL) {
 60                 const struct inet6_protocol *ipprot;
 61 
 62                 ipprot = rcu_dereference(inet6_protos[ipv6_hdr(skb)->nexthdr]);
 63                 if (ipprot && ipprot->early_demux)
 64                         ipprot->early_demux(skb);
 65         }
 66         if (!skb_valid_dst(skb))
 67                 ip6_route_input(skb);
 68 
 69         return dst_input(skb);
 70 }
 71 
 72 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 73 {
 74         const struct ipv6hdr *hdr;
 75         u32 pkt_len;
 76         struct inet6_dev *idev;
 77         struct net *net = dev_net(skb->dev);
 78 
 79         if (skb->pkt_type == PACKET_OTHERHOST) {
 80                 kfree_skb(skb);
 81                 return NET_RX_DROP;
 82         }
 83 
 84         rcu_read_lock();
 85 
 86         idev = __in6_dev_get(skb->dev);
 87 
 88         __IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
 89 
 90         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
 91             !idev || unlikely(idev->cnf.disable_ipv6)) {
 92                 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 93                 goto drop;
 94         }
 95 
 96         memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
 97 
 98         /*
 99          * Store incoming device index. When the packet will
100          * be queued, we cannot refer to skb->dev anymore.
101          *
102          * BTW, when we send a packet for our own local address on a
103          * non-loopback interface (e.g. ethX), it is being delivered
104          * via the loopback interface (lo) here; skb->dev = loopback_dev.
105          * It, however, should be considered as if it is being
106          * arrived via the sending interface (ethX), because of the
107          * nature of scoping architecture. --yoshfuji
108          */
109         IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
110 
111         if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
112                 goto err;
113 
114         hdr = ipv6_hdr(skb);
115 
116         if (hdr->version != 6)
117                 goto err;
118 
119         __IP6_ADD_STATS(net, idev,
120                         IPSTATS_MIB_NOECTPKTS +
121                                 (ipv6_get_dsfield(hdr) & INET_ECN_MASK),
122                         max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
123         /*
124          * RFC4291 2.5.3
125          * A packet received on an interface with a destination address
126          * of loopback must be dropped.
127          */
128         if (!(dev->flags & IFF_LOOPBACK) &&
129             ipv6_addr_loopback(&hdr->daddr))
130                 goto err;
131 
132         /* RFC4291 Errata ID: 3480
133          * Interface-Local scope spans only a single interface on a
134          * node and is useful only for loopback transmission of
135          * multicast.  Packets with interface-local scope received
136          * from another node must be discarded.
137          */
138         if (!(skb->pkt_type == PACKET_LOOPBACK ||
139               dev->flags & IFF_LOOPBACK) &&
140             ipv6_addr_is_multicast(&hdr->daddr) &&
141             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
142                 goto err;
143 
144         /* If enabled, drop unicast packets that were encapsulated in link-layer
145          * multicast or broadcast to protected against the so-called "hole-196"
146          * attack in 802.11 wireless.
147          */
148         if (!ipv6_addr_is_multicast(&hdr->daddr) &&
149             (skb->pkt_type == PACKET_BROADCAST ||
150              skb->pkt_type == PACKET_MULTICAST) &&
151             idev->cnf.drop_unicast_in_l2_multicast)
152                 goto err;
153 
154         /* RFC4291 2.7
155          * Nodes must not originate a packet to a multicast address whose scope
156          * field contains the reserved value 0; if such a packet is received, it
157          * must be silently dropped.
158          */
159         if (ipv6_addr_is_multicast(&hdr->daddr) &&
160             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
161                 goto err;
162 
163         /*
164          * RFC4291 2.7
165          * Multicast addresses must not be used as source addresses in IPv6
166          * packets or appear in any Routing header.
167          */
168         if (ipv6_addr_is_multicast(&hdr->saddr))
169                 goto err;
170 
171         skb->transport_header = skb->network_header + sizeof(*hdr);
172         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
173 
174         pkt_len = ntohs(hdr->payload_len);
175 
176         /* pkt_len may be zero if Jumbo payload option is present */
177         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
178                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
179                         __IP6_INC_STATS(net,
180                                         idev, IPSTATS_MIB_INTRUNCATEDPKTS);
181                         goto drop;
182                 }
183                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
184                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
185                         goto drop;
186                 }
187                 hdr = ipv6_hdr(skb);
188         }
189 
190         if (hdr->nexthdr == NEXTHDR_HOP) {
191                 if (ipv6_parse_hopopts(skb) < 0) {
192                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
193                         rcu_read_unlock();
194                         return NET_RX_DROP;
195                 }
196         }
197 
198         rcu_read_unlock();
199 
200         /* Must drop socket now because of tproxy. */
201         skb_orphan(skb);
202 
203         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
204                        net, NULL, skb, dev, NULL,
205                        ip6_rcv_finish);
206 err:
207         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
208 drop:
209         rcu_read_unlock();
210         kfree_skb(skb);
211         return NET_RX_DROP;
212 }
213 
214 /*
215  *      Deliver the packet to the host
216  */
217 
218 
219 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
220 {
221         const struct inet6_protocol *ipprot;
222         struct inet6_dev *idev;
223         unsigned int nhoff;
224         int nexthdr;
225         bool raw;
226         bool have_final = false;
227 
228         /*
229          *      Parse extension headers
230          */
231 
232         rcu_read_lock();
233 resubmit:
234         idev = ip6_dst_idev(skb_dst(skb));
235         if (!pskb_pull(skb, skb_transport_offset(skb)))
236                 goto discard;
237         nhoff = IP6CB(skb)->nhoff;
238         nexthdr = skb_network_header(skb)[nhoff];
239 
240 resubmit_final:
241         raw = raw6_local_deliver(skb, nexthdr);
242         ipprot = rcu_dereference(inet6_protos[nexthdr]);
243         if (ipprot) {
244                 int ret;
245 
246                 if (have_final) {
247                         if (!(ipprot->flags & INET6_PROTO_FINAL)) {
248                                 /* Once we've seen a final protocol don't
249                                  * allow encapsulation on any non-final
250                                  * ones. This allows foo in UDP encapsulation
251                                  * to work.
252                                  */
253                                 goto discard;
254                         }
255                 } else if (ipprot->flags & INET6_PROTO_FINAL) {
256                         const struct ipv6hdr *hdr;
257 
258                         /* Only do this once for first final protocol */
259                         have_final = true;
260 
261                         /* Free reference early: we don't need it any more,
262                            and it may hold ip_conntrack module loaded
263                            indefinitely. */
264                         nf_reset(skb);
265 
266                         skb_postpull_rcsum(skb, skb_network_header(skb),
267                                            skb_network_header_len(skb));
268                         hdr = ipv6_hdr(skb);
269                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
270                             !ipv6_chk_mcast_addr(skb->dev, &hdr->daddr,
271                             &hdr->saddr) &&
272                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
273                                 goto discard;
274                 }
275                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
276                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
277                         goto discard;
278 
279                 ret = ipprot->handler(skb);
280                 if (ret > 0) {
281                         if (ipprot->flags & INET6_PROTO_FINAL) {
282                                 /* Not an extension header, most likely UDP
283                                  * encapsulation. Use return value as nexthdr
284                                  * protocol not nhoff (which presumably is
285                                  * not set by handler).
286                                  */
287                                 nexthdr = ret;
288                                 goto resubmit_final;
289                         } else {
290                                 goto resubmit;
291                         }
292                 } else if (ret == 0) {
293                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
294                 }
295         } else {
296                 if (!raw) {
297                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
298                                 __IP6_INC_STATS(net, idev,
299                                                 IPSTATS_MIB_INUNKNOWNPROTOS);
300                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
301                                             ICMPV6_UNK_NEXTHDR, nhoff);
302                         }
303                         kfree_skb(skb);
304                 } else {
305                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
306                         consume_skb(skb);
307                 }
308         }
309         rcu_read_unlock();
310         return 0;
311 
312 discard:
313         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
314         rcu_read_unlock();
315         kfree_skb(skb);
316         return 0;
317 }
318 
319 
320 int ip6_input(struct sk_buff *skb)
321 {
322         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
323                        dev_net(skb->dev), NULL, skb, skb->dev, NULL,
324                        ip6_input_finish);
325 }
326 EXPORT_SYMBOL_GPL(ip6_input);
327 
328 int ip6_mc_input(struct sk_buff *skb)
329 {
330         const struct ipv6hdr *hdr;
331         bool deliver;
332 
333         __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
334                          ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_INMCAST,
335                          skb->len);
336 
337         hdr = ipv6_hdr(skb);
338         deliver = ipv6_chk_mcast_addr(skb->dev, &hdr->daddr, NULL);
339 
340 #ifdef CONFIG_IPV6_MROUTE
341         /*
342          *      IPv6 multicast router mode is now supported ;)
343          */
344         if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
345             !(ipv6_addr_type(&hdr->daddr) &
346               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
347             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
348                 /*
349                  * Okay, we try to forward - split and duplicate
350                  * packets.
351                  */
352                 struct sk_buff *skb2;
353                 struct inet6_skb_parm *opt = IP6CB(skb);
354 
355                 /* Check for MLD */
356                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
357                         /* Check if this is a mld message */
358                         u8 nexthdr = hdr->nexthdr;
359                         __be16 frag_off;
360                         int offset;
361 
362                         /* Check if the value of Router Alert
363                          * is for MLD (0x0000).
364                          */
365                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
366                                 deliver = false;
367 
368                                 if (!ipv6_ext_hdr(nexthdr)) {
369                                         /* BUG */
370                                         goto out;
371                                 }
372                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
373                                                           &nexthdr, &frag_off);
374                                 if (offset < 0)
375                                         goto out;
376 
377                                 if (ipv6_is_mld(skb, nexthdr, offset))
378                                         deliver = true;
379 
380                                 goto out;
381                         }
382                         /* unknown RA - process it normally */
383                 }
384 
385                 if (deliver)
386                         skb2 = skb_clone(skb, GFP_ATOMIC);
387                 else {
388                         skb2 = skb;
389                         skb = NULL;
390                 }
391 
392                 if (skb2) {
393                         ip6_mr_input(skb2);
394                 }
395         }
396 out:
397 #endif
398         if (likely(deliver))
399                 ip6_input(skb);
400         else {
401                 /* discard */
402                 kfree_skb(skb);
403         }
404 
405         return 0;
406 }
407 

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