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 }