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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 (net->ipv4.sysctl_ip_early_demux && !skb_dst(skb) && skb->sk == NULL) {
 53                 const struct inet6_protocol *ipprot;
 54 
 55                 ipprot = rcu_dereference(inet6_protos[ipv6_hdr(skb)->nexthdr]);
 56                 if (ipprot && ipprot->early_demux)
 57                         ipprot->early_demux(skb);
 58         }
 59         if (!skb_valid_dst(skb))
 60                 ip6_route_input(skb);
 61 
 62         return dst_input(skb);
 63 }
 64 
 65 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 66 {
 67         const struct ipv6hdr *hdr;
 68         u32 pkt_len;
 69         struct inet6_dev *idev;
 70         struct net *net = dev_net(skb->dev);
 71 
 72         if (skb->pkt_type == PACKET_OTHERHOST) {
 73                 kfree_skb(skb);
 74                 return NET_RX_DROP;
 75         }
 76 
 77         rcu_read_lock();
 78 
 79         idev = __in6_dev_get(skb->dev);
 80 
 81         IP6_UPD_PO_STATS_BH(net, idev, IPSTATS_MIB_IN, skb->len);
 82 
 83         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
 84             !idev || unlikely(idev->cnf.disable_ipv6)) {
 85                 IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDISCARDS);
 86                 goto drop;
 87         }
 88 
 89         memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
 90 
 91         /*
 92          * Store incoming device index. When the packet will
 93          * be queued, we cannot refer to skb->dev anymore.
 94          *
 95          * BTW, when we send a packet for our own local address on a
 96          * non-loopback interface (e.g. ethX), it is being delivered
 97          * via the loopback interface (lo) here; skb->dev = loopback_dev.
 98          * It, however, should be considered as if it is being
 99          * arrived via the sending interface (ethX), because of the
100          * nature of scoping architecture. --yoshfuji
101          */
102         IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
103 
104         if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
105                 goto err;
106 
107         hdr = ipv6_hdr(skb);
108 
109         if (hdr->version != 6)
110                 goto err;
111 
112         IP6_ADD_STATS_BH(net, idev,
113                          IPSTATS_MIB_NOECTPKTS +
114                                 (ipv6_get_dsfield(hdr) & INET_ECN_MASK),
115                          max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
116         /*
117          * RFC4291 2.5.3
118          * A packet received on an interface with a destination address
119          * of loopback must be dropped.
120          */
121         if (!(dev->flags & IFF_LOOPBACK) &&
122             ipv6_addr_loopback(&hdr->daddr))
123                 goto err;
124 
125         /* RFC4291 Errata ID: 3480
126          * Interface-Local scope spans only a single interface on a
127          * node and is useful only for loopback transmission of
128          * multicast.  Packets with interface-local scope received
129          * from another node must be discarded.
130          */
131         if (!(skb->pkt_type == PACKET_LOOPBACK ||
132               dev->flags & IFF_LOOPBACK) &&
133             ipv6_addr_is_multicast(&hdr->daddr) &&
134             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
135                 goto err;
136 
137         /* If enabled, drop unicast packets that were encapsulated in link-layer
138          * multicast or broadcast to protected against the so-called "hole-196"
139          * attack in 802.11 wireless.
140          */
141         if (!ipv6_addr_is_multicast(&hdr->daddr) &&
142             (skb->pkt_type == PACKET_BROADCAST ||
143              skb->pkt_type == PACKET_MULTICAST) &&
144             idev->cnf.drop_unicast_in_l2_multicast)
145                 goto err;
146 
147         /* RFC4291 2.7
148          * Nodes must not originate a packet to a multicast address whose scope
149          * field contains the reserved value 0; if such a packet is received, it
150          * must be silently dropped.
151          */
152         if (ipv6_addr_is_multicast(&hdr->daddr) &&
153             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
154                 goto err;
155 
156         /*
157          * RFC4291 2.7
158          * Multicast addresses must not be used as source addresses in IPv6
159          * packets or appear in any Routing header.
160          */
161         if (ipv6_addr_is_multicast(&hdr->saddr))
162                 goto err;
163 
164         skb->transport_header = skb->network_header + sizeof(*hdr);
165         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
166 
167         pkt_len = ntohs(hdr->payload_len);
168 
169         /* pkt_len may be zero if Jumbo payload option is present */
170         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
171                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
172                         IP6_INC_STATS_BH(net,
173                                          idev, IPSTATS_MIB_INTRUNCATEDPKTS);
174                         goto drop;
175                 }
176                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
177                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INHDRERRORS);
178                         goto drop;
179                 }
180                 hdr = ipv6_hdr(skb);
181         }
182 
183         if (hdr->nexthdr == NEXTHDR_HOP) {
184                 if (ipv6_parse_hopopts(skb) < 0) {
185                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INHDRERRORS);
186                         rcu_read_unlock();
187                         return NET_RX_DROP;
188                 }
189         }
190 
191         rcu_read_unlock();
192 
193         /* Must drop socket now because of tproxy. */
194         skb_orphan(skb);
195 
196         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
197                        net, NULL, skb, dev, NULL,
198                        ip6_rcv_finish);
199 err:
200         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INHDRERRORS);
201 drop:
202         rcu_read_unlock();
203         kfree_skb(skb);
204         return NET_RX_DROP;
205 }
206 
207 /*
208  *      Deliver the packet to the host
209  */
210 
211 
212 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
213 {
214         const struct inet6_protocol *ipprot;
215         struct inet6_dev *idev;
216         unsigned int nhoff;
217         int nexthdr;
218         bool raw;
219 
220         /*
221          *      Parse extension headers
222          */
223 
224         rcu_read_lock();
225 resubmit:
226         idev = ip6_dst_idev(skb_dst(skb));
227         if (!pskb_pull(skb, skb_transport_offset(skb)))
228                 goto discard;
229         nhoff = IP6CB(skb)->nhoff;
230         nexthdr = skb_network_header(skb)[nhoff];
231 
232         raw = raw6_local_deliver(skb, nexthdr);
233         ipprot = rcu_dereference(inet6_protos[nexthdr]);
234         if (ipprot) {
235                 int ret;
236 
237                 if (ipprot->flags & INET6_PROTO_FINAL) {
238                         const struct ipv6hdr *hdr;
239 
240                         /* Free reference early: we don't need it any more,
241                            and it may hold ip_conntrack module loaded
242                            indefinitely. */
243                         nf_reset(skb);
244 
245                         skb_postpull_rcsum(skb, skb_network_header(skb),
246                                            skb_network_header_len(skb));
247                         hdr = ipv6_hdr(skb);
248                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
249                             !ipv6_chk_mcast_addr(skb->dev, &hdr->daddr,
250                             &hdr->saddr) &&
251                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
252                                 goto discard;
253                 }
254                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
255                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
256                         goto discard;
257 
258                 ret = ipprot->handler(skb);
259                 if (ret > 0)
260                         goto resubmit;
261                 else if (ret == 0)
262                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDELIVERS);
263         } else {
264                 if (!raw) {
265                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
266                                 IP6_INC_STATS_BH(net, idev,
267                                                  IPSTATS_MIB_INUNKNOWNPROTOS);
268                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
269                                             ICMPV6_UNK_NEXTHDR, nhoff);
270                         }
271                         kfree_skb(skb);
272                 } else {
273                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDELIVERS);
274                         consume_skb(skb);
275                 }
276         }
277         rcu_read_unlock();
278         return 0;
279 
280 discard:
281         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDISCARDS);
282         rcu_read_unlock();
283         kfree_skb(skb);
284         return 0;
285 }
286 
287 
288 int ip6_input(struct sk_buff *skb)
289 {
290         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
291                        dev_net(skb->dev), NULL, skb, skb->dev, NULL,
292                        ip6_input_finish);
293 }
294 
295 int ip6_mc_input(struct sk_buff *skb)
296 {
297         const struct ipv6hdr *hdr;
298         bool deliver;
299 
300         IP6_UPD_PO_STATS_BH(dev_net(skb_dst(skb)->dev),
301                          ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_INMCAST,
302                          skb->len);
303 
304         hdr = ipv6_hdr(skb);
305         deliver = ipv6_chk_mcast_addr(skb->dev, &hdr->daddr, NULL);
306 
307 #ifdef CONFIG_IPV6_MROUTE
308         /*
309          *      IPv6 multicast router mode is now supported ;)
310          */
311         if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
312             !(ipv6_addr_type(&hdr->daddr) &
313               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
314             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
315                 /*
316                  * Okay, we try to forward - split and duplicate
317                  * packets.
318                  */
319                 struct sk_buff *skb2;
320                 struct inet6_skb_parm *opt = IP6CB(skb);
321 
322                 /* Check for MLD */
323                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
324                         /* Check if this is a mld message */
325                         u8 nexthdr = hdr->nexthdr;
326                         __be16 frag_off;
327                         int offset;
328 
329                         /* Check if the value of Router Alert
330                          * is for MLD (0x0000).
331                          */
332                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
333                                 deliver = false;
334 
335                                 if (!ipv6_ext_hdr(nexthdr)) {
336                                         /* BUG */
337                                         goto out;
338                                 }
339                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
340                                                           &nexthdr, &frag_off);
341                                 if (offset < 0)
342                                         goto out;
343 
344                                 if (ipv6_is_mld(skb, nexthdr, offset))
345                                         deliver = true;
346 
347                                 goto out;
348                         }
349                         /* unknown RA - process it normally */
350                 }
351 
352                 if (deliver)
353                         skb2 = skb_clone(skb, GFP_ATOMIC);
354                 else {
355                         skb2 = skb;
356                         skb = NULL;
357                 }
358 
359                 if (skb2) {
360                         ip6_mr_input(skb2);
361                 }
362         }
363 out:
364 #endif
365         if (likely(deliver))
366                 ip6_input(skb);
367         else {
368                 /* discard */
369                 kfree_skb(skb);
370         }
371 
372         return 0;
373 }
374 

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