net/ipv6/ip6_input.c

   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 #include <net/udp.h>
  36
  37 #include <net/ipv6.h>
  38 #include <net/protocol.h>
  39 #include <net/transp_v6.h>
  40 #include <net/rawv6.h>
  41 #include <net/ndisc.h>
  42 #include <net/ip6_route.h>
  43 #include <net/addrconf.h>
  44 #include <net/xfrm.h>
  45 #include <net/inet_ecn.h>
  46 #include <net/dst_metadata.h>
  47
  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         skb->transport_header = skb->network_header + sizeof(*hdr);
 249         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
 250
 251         pkt_len = ntohs(hdr->payload_len);
 252
 253         /* pkt_len may be zero if Jumbo payload option is present */
 254         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
 255                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
 256                         __IP6_INC_STATS(net,
 257                                         idev, IPSTATS_MIB_INTRUNCATEDPKTS);
 258                         goto drop;
 259                 }
 260                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
 261                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 262                         goto drop;
 263                 }
 264                 hdr = ipv6_hdr(skb);
 265         }
 266
 267         if (hdr->nexthdr == NEXTHDR_HOP) {
 268                 if (ipv6_parse_hopopts(skb) < 0) {
 269                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 270                         rcu_read_unlock();
 271                         return NULL;
 272                 }
 273         }
 274
 275         rcu_read_unlock();
 276
 277         /* Must drop socket now because of tproxy. */
 278         if (!skb_sk_is_prefetched(skb))
 279                 skb_orphan(skb);
 280
 281         return skb;
 282 err:
 283         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 284 drop:
 285         rcu_read_unlock();
 286         kfree_skb(skb);
 287         return NULL;
 288 }
 289
 290 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 291 {
 292         struct net *net = dev_net(skb->dev);
 293
 294         skb = ip6_rcv_core(skb, dev, net);
 295         if (skb == NULL)
 296                 return NET_RX_DROP;
 297         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
 298                        net, NULL, skb, dev, NULL,
 299                        ip6_rcv_finish);
 300 }
 301
 302 static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
 303                             struct net *net)
 304 {
 305         NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
 306                      head, dev, NULL, ip6_rcv_finish);
 307         ip6_list_rcv_finish(net, NULL, head);
 308 }
 309
 310 /* Receive a list of IPv6 packets */
 311 void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
 312                    struct net_device *orig_dev)
 313 {
 314         struct net_device *curr_dev = NULL;
 315         struct net *curr_net = NULL;
 316         struct sk_buff *skb, *next;
 317         struct list_head sublist;
 318
 319         INIT_LIST_HEAD(&sublist);
 320         list_for_each_entry_safe(skb, next, head, list) {
 321                 struct net_device *dev = skb->dev;
 322                 struct net *net = dev_net(dev);
 323
 324                 skb_list_del_init(skb);
 325                 skb = ip6_rcv_core(skb, dev, net);
 326                 if (skb == NULL)
 327                         continue;
 328
 329                 if (curr_dev != dev || curr_net != net) {
 330                         /* dispatch old sublist */
 331                         if (!list_empty(&sublist))
 332                                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 333                         /* start new sublist */
 334                         INIT_LIST_HEAD(&sublist);
 335                         curr_dev = dev;
 336                         curr_net = net;
 337                 }
 338                 list_add_tail(&skb->list, &sublist);
 339         }
 340         /* dispatch final sublist */
 341         if (!list_empty(&sublist))
 342                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 343 }
 344
 345 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
 346
 347 /*
 348  *      Deliver the packet to the host
 349  */
 350 void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
 351                               bool have_final)
 352 {
 353         const struct inet6_protocol *ipprot;
 354         struct inet6_dev *idev;
 355         unsigned int nhoff;
 356         bool raw;
 357
 358         /*
 359          *      Parse extension headers
 360          */
 361
 362 resubmit:
 363         idev = ip6_dst_idev(skb_dst(skb));
 364         nhoff = IP6CB(skb)->nhoff;
 365         if (!have_final) {
 366                 if (!pskb_pull(skb, skb_transport_offset(skb)))
 367                         goto discard;
 368                 nexthdr = skb_network_header(skb)[nhoff];
 369         }
 370
 371 resubmit_final:
 372         raw = raw6_local_deliver(skb, nexthdr);
 373         ipprot = rcu_dereference(inet6_protos[nexthdr]);
 374         if (ipprot) {
 375                 int ret;
 376
 377                 if (have_final) {
 378                         if (!(ipprot->flags & INET6_PROTO_FINAL)) {
 379                                 /* Once we've seen a final protocol don't
 380                                  * allow encapsulation on any non-final
 381                                  * ones. This allows foo in UDP encapsulation
 382                                  * to work.
 383                                  */
 384                                 goto discard;
 385                         }
 386                 } else if (ipprot->flags & INET6_PROTO_FINAL) {
 387                         const struct ipv6hdr *hdr;
 388                         int sdif = inet6_sdif(skb);
 389                         struct net_device *dev;
 390
 391                         /* Only do this once for first final protocol */
 392                         have_final = true;
 393
 394                         /* Free reference early: we don't need it any more,
 395                            and it may hold ip_conntrack module loaded
 396                            indefinitely. */
 397                         nf_reset_ct(skb);
 398
 399                         skb_postpull_rcsum(skb, skb_network_header(skb),
 400                                            skb_network_header_len(skb));
 401                         hdr = ipv6_hdr(skb);
 402
 403                         /* skb->dev passed may be master dev for vrfs. */
 404                         if (sdif) {
 405                                 dev = dev_get_by_index_rcu(net, sdif);
 406                                 if (!dev)
 407                                         goto discard;
 408                         } else {
 409                                 dev = skb->dev;
 410                         }
 411
 412                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
 413                             !ipv6_chk_mcast_addr(dev, &hdr->daddr,
 414                                                  &hdr->saddr) &&
 415                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
 416                                 goto discard;
 417                 }
 418                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
 419                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
 420                         goto discard;
 421
 422                 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
 423                                       skb);
 424                 if (ret > 0) {
 425                         if (ipprot->flags & INET6_PROTO_FINAL) {
 426                                 /* Not an extension header, most likely UDP
 427                                  * encapsulation. Use return value as nexthdr
 428                                  * protocol not nhoff (which presumably is
 429                                  * not set by handler).
 430                                  */
 431                                 nexthdr = ret;
 432                                 goto resubmit_final;
 433                         } else {
 434                                 goto resubmit;
 435                         }
 436                 } else if (ret == 0) {
 437                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 438                 }
 439         } else {
 440                 if (!raw) {
 441                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 442                                 __IP6_INC_STATS(net, idev,
 443                                                 IPSTATS_MIB_INUNKNOWNPROTOS);
 444                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
 445                                             ICMPV6_UNK_NEXTHDR, nhoff);
 446                         }
 447                         kfree_skb(skb);
 448                 } else {
 449                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 450                         consume_skb(skb);
 451                 }
 452         }
 453         return;
 454
 455 discard:
 456         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 457         kfree_skb(skb);
 458 }
 459
 460 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 461 {
 462         rcu_read_lock();
 463         ip6_protocol_deliver_rcu(net, skb, 0, false);
 464         rcu_read_unlock();
 465
 466         return 0;
 467 }
 468
 469
 470 int ip6_input(struct sk_buff *skb)
 471 {
 472         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
 473                        dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 474                        ip6_input_finish);
 475 }
 476 EXPORT_SYMBOL_GPL(ip6_input);
 477
 478 int ip6_mc_input(struct sk_buff *skb)
 479 {
 480         int sdif = inet6_sdif(skb);
 481         const struct ipv6hdr *hdr;
 482         struct net_device *dev;
 483         bool deliver;
 484
 485         __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
 486                          __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
 487                          skb->len);
 488
 489         /* skb->dev passed may be master dev for vrfs. */
 490         if (sdif) {
 491                 rcu_read_lock();
 492                 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
 493                 if (!dev) {
 494                         rcu_read_unlock();
 495                         kfree_skb(skb);
 496                         return -ENODEV;
 497                 }
 498         } else {
 499                 dev = skb->dev;
 500         }
 501
 502         hdr = ipv6_hdr(skb);
 503         deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
 504         if (sdif)
 505                 rcu_read_unlock();
 506
 507 #ifdef CONFIG_IPV6_MROUTE
 508         /*
 509          *      IPv6 multicast router mode is now supported ;)
 510          */
 511         if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
 512             !(ipv6_addr_type(&hdr->daddr) &
 513               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
 514             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
 515                 /*
 516                  * Okay, we try to forward - split and duplicate
 517                  * packets.
 518                  */
 519                 struct sk_buff *skb2;
 520                 struct inet6_skb_parm *opt = IP6CB(skb);
 521
 522                 /* Check for MLD */
 523                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
 524                         /* Check if this is a mld message */
 525                         u8 nexthdr = hdr->nexthdr;
 526                         __be16 frag_off;
 527                         int offset;
 528
 529                         /* Check if the value of Router Alert
 530                          * is for MLD (0x0000).
 531                          */
 532                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
 533                                 deliver = false;
 534
 535                                 if (!ipv6_ext_hdr(nexthdr)) {
 536                                         /* BUG */
 537                                         goto out;
 538                                 }
 539                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
 540                                                           &nexthdr, &frag_off);
 541                                 if (offset < 0)
 542                                         goto out;
 543
 544                                 if (ipv6_is_mld(skb, nexthdr, offset))
 545                                         deliver = true;
 546
 547                                 goto out;
 548                         }
 549                         /* unknown RA - process it normally */
 550                 }
 551
 552                 if (deliver)
 553                         skb2 = skb_clone(skb, GFP_ATOMIC);
 554                 else {
 555                         skb2 = skb;
 556                         skb = NULL;
 557                 }
 558
 559                 if (skb2) {
 560                         ip6_mr_input(skb2);
 561                 }
 562         }
 563 out:
 564 #endif
 565         if (likely(deliver))
 566                 ip6_input(skb);
 567         else {
 568                 /* discard */
 569                 kfree_skb(skb);
 570         }
 571
 572         return 0;
 573 }