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
  36 #include <net/ipv6.h>
  37 #include <net/protocol.h>
  38 #include <net/transp_v6.h>
  39 #include <net/rawv6.h>
  40 #include <net/ndisc.h>
  41 #include <net/ip6_route.h>
  42 #include <net/addrconf.h>
  43 #include <net/xfrm.h>
  44 #include <net/inet_ecn.h>
  45 #include <net/dst_metadata.h>
  46
  47 INDIRECT_CALLABLE_DECLARE(void udp_v6_early_demux(struct sk_buff *));
  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         /* While RFC4291 is not explicit about v4mapped addresses
 249          * in IPv6 headers, it seems clear linux dual-stack
 250          * model can not deal properly with these.
 251          * Security models could be fooled by ::ffff:127.0.0.1 for example.
 252          *
 253          * https://tools.ietf.org/html/draft-itojun-v6ops-v4mapped-harmful-02
 254          */
 255         if (ipv6_addr_v4mapped(&hdr->saddr))
 256                 goto err;
 257
 258         skb->transport_header = skb->network_header + sizeof(*hdr);
 259         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
 260
 261         pkt_len = ntohs(hdr->payload_len);
 262
 263         /* pkt_len may be zero if Jumbo payload option is present */
 264         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
 265                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
 266                         __IP6_INC_STATS(net,
 267                                         idev, IPSTATS_MIB_INTRUNCATEDPKTS);
 268                         goto drop;
 269                 }
 270                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
 271                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 272                         goto drop;
 273                 }
 274                 hdr = ipv6_hdr(skb);
 275         }
 276
 277         if (hdr->nexthdr == NEXTHDR_HOP) {
 278                 if (ipv6_parse_hopopts(skb) < 0) {
 279                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 280                         rcu_read_unlock();
 281                         return NULL;
 282                 }
 283         }
 284
 285         rcu_read_unlock();
 286
 287         /* Must drop socket now because of tproxy. */
 288         if (!skb_sk_is_prefetched(skb))
 289                 skb_orphan(skb);
 290
 291         return skb;
 292 err:
 293         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 294 drop:
 295         rcu_read_unlock();
 296         kfree_skb(skb);
 297         return NULL;
 298 }
 299
 300 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 301 {
 302         struct net *net = dev_net(skb->dev);
 303
 304         skb = ip6_rcv_core(skb, dev, net);
 305         if (skb == NULL)
 306                 return NET_RX_DROP;
 307         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
 308                        net, NULL, skb, dev, NULL,
 309                        ip6_rcv_finish);
 310 }
 311
 312 static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
 313                             struct net *net)
 314 {
 315         NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
 316                      head, dev, NULL, ip6_rcv_finish);
 317         ip6_list_rcv_finish(net, NULL, head);
 318 }
 319
 320 /* Receive a list of IPv6 packets */
 321 void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
 322                    struct net_device *orig_dev)
 323 {
 324         struct net_device *curr_dev = NULL;
 325         struct net *curr_net = NULL;
 326         struct sk_buff *skb, *next;
 327         struct list_head sublist;
 328
 329         INIT_LIST_HEAD(&sublist);
 330         list_for_each_entry_safe(skb, next, head, list) {
 331                 struct net_device *dev = skb->dev;
 332                 struct net *net = dev_net(dev);
 333
 334                 skb_list_del_init(skb);
 335                 skb = ip6_rcv_core(skb, dev, net);
 336                 if (skb == NULL)
 337                         continue;
 338
 339                 if (curr_dev != dev || curr_net != net) {
 340                         /* dispatch old sublist */
 341                         if (!list_empty(&sublist))
 342                                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 343                         /* start new sublist */
 344                         INIT_LIST_HEAD(&sublist);
 345                         curr_dev = dev;
 346                         curr_net = net;
 347                 }
 348                 list_add_tail(&skb->list, &sublist);
 349         }
 350         /* dispatch final sublist */
 351         if (!list_empty(&sublist))
 352                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 353 }
 354
 355 INDIRECT_CALLABLE_DECLARE(int udpv6_rcv(struct sk_buff *));
 356 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
 357
 358 /*
 359  *      Deliver the packet to the host
 360  */
 361 void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
 362                               bool have_final)
 363 {
 364         const struct inet6_protocol *ipprot;
 365         struct inet6_dev *idev;
 366         unsigned int nhoff;
 367         bool raw;
 368
 369         /*
 370          *      Parse extension headers
 371          */
 372
 373 resubmit:
 374         idev = ip6_dst_idev(skb_dst(skb));
 375         nhoff = IP6CB(skb)->nhoff;
 376         if (!have_final) {
 377                 if (!pskb_pull(skb, skb_transport_offset(skb)))
 378                         goto discard;
 379                 nexthdr = skb_network_header(skb)[nhoff];
 380         }
 381
 382 resubmit_final:
 383         raw = raw6_local_deliver(skb, nexthdr);
 384         ipprot = rcu_dereference(inet6_protos[nexthdr]);
 385         if (ipprot) {
 386                 int ret;
 387
 388                 if (have_final) {
 389                         if (!(ipprot->flags & INET6_PROTO_FINAL)) {
 390                                 /* Once we've seen a final protocol don't
 391                                  * allow encapsulation on any non-final
 392                                  * ones. This allows foo in UDP encapsulation
 393                                  * to work.
 394                                  */
 395                                 goto discard;
 396                         }
 397                 } else if (ipprot->flags & INET6_PROTO_FINAL) {
 398                         const struct ipv6hdr *hdr;
 399                         int sdif = inet6_sdif(skb);
 400                         struct net_device *dev;
 401
 402                         /* Only do this once for first final protocol */
 403                         have_final = true;
 404
 405                         /* Free reference early: we don't need it any more,
 406                            and it may hold ip_conntrack module loaded
 407                            indefinitely. */
 408                         nf_reset_ct(skb);
 409
 410                         skb_postpull_rcsum(skb, skb_network_header(skb),
 411                                            skb_network_header_len(skb));
 412                         hdr = ipv6_hdr(skb);
 413
 414                         /* skb->dev passed may be master dev for vrfs. */
 415                         if (sdif) {
 416                                 dev = dev_get_by_index_rcu(net, sdif);
 417                                 if (!dev)
 418                                         goto discard;
 419                         } else {
 420                                 dev = skb->dev;
 421                         }
 422
 423                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
 424                             !ipv6_chk_mcast_addr(dev, &hdr->daddr,
 425                                                  &hdr->saddr) &&
 426                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
 427                                 goto discard;
 428                 }
 429                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
 430                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
 431                         goto discard;
 432
 433                 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
 434                                       skb);
 435                 if (ret > 0) {
 436                         if (ipprot->flags & INET6_PROTO_FINAL) {
 437                                 /* Not an extension header, most likely UDP
 438                                  * encapsulation. Use return value as nexthdr
 439                                  * protocol not nhoff (which presumably is
 440                                  * not set by handler).
 441                                  */
 442                                 nexthdr = ret;
 443                                 goto resubmit_final;
 444                         } else {
 445                                 goto resubmit;
 446                         }
 447                 } else if (ret == 0) {
 448                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 449                 }
 450         } else {
 451                 if (!raw) {
 452                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 453                                 __IP6_INC_STATS(net, idev,
 454                                                 IPSTATS_MIB_INUNKNOWNPROTOS);
 455                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
 456                                             ICMPV6_UNK_NEXTHDR, nhoff);
 457                         }
 458                         kfree_skb(skb);
 459                 } else {
 460                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 461                         consume_skb(skb);
 462                 }
 463         }
 464         return;
 465
 466 discard:
 467         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 468         kfree_skb(skb);
 469 }
 470
 471 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 472 {
 473         rcu_read_lock();
 474         ip6_protocol_deliver_rcu(net, skb, 0, false);
 475         rcu_read_unlock();
 476
 477         return 0;
 478 }
 479
 480
 481 int ip6_input(struct sk_buff *skb)
 482 {
 483         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
 484                        dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 485                        ip6_input_finish);
 486 }
 487 EXPORT_SYMBOL_GPL(ip6_input);
 488
 489 int ip6_mc_input(struct sk_buff *skb)
 490 {
 491         int sdif = inet6_sdif(skb);
 492         const struct ipv6hdr *hdr;
 493         struct net_device *dev;
 494         bool deliver;
 495
 496         __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
 497                          __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
 498                          skb->len);
 499
 500         /* skb->dev passed may be master dev for vrfs. */
 501         if (sdif) {
 502                 rcu_read_lock();
 503                 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
 504                 if (!dev) {
 505                         rcu_read_unlock();
 506                         kfree_skb(skb);
 507                         return -ENODEV;
 508                 }
 509         } else {
 510                 dev = skb->dev;
 511         }
 512
 513         hdr = ipv6_hdr(skb);
 514         deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
 515         if (sdif)
 516                 rcu_read_unlock();
 517
 518 #ifdef CONFIG_IPV6_MROUTE
 519         /*
 520          *      IPv6 multicast router mode is now supported ;)
 521          */
 522         if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
 523             !(ipv6_addr_type(&hdr->daddr) &
 524               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
 525             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
 526                 /*
 527                  * Okay, we try to forward - split and duplicate
 528                  * packets.
 529                  */
 530                 struct sk_buff *skb2;
 531                 struct inet6_skb_parm *opt = IP6CB(skb);
 532
 533                 /* Check for MLD */
 534                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
 535                         /* Check if this is a mld message */
 536                         u8 nexthdr = hdr->nexthdr;
 537                         __be16 frag_off;
 538                         int offset;
 539
 540                         /* Check if the value of Router Alert
 541                          * is for MLD (0x0000).
 542                          */
 543                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
 544                                 deliver = false;
 545
 546                                 if (!ipv6_ext_hdr(nexthdr)) {
 547                                         /* BUG */
 548                                         goto out;
 549                                 }
 550                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
 551                                                           &nexthdr, &frag_off);
 552                                 if (offset < 0)
 553                                         goto out;
 554
 555                                 if (ipv6_is_mld(skb, nexthdr, offset))
 556                                         deliver = true;
 557
 558                                 goto out;
 559                         }
 560                         /* unknown RA - process it normally */
 561                 }
 562
 563                 if (deliver)
 564                         skb2 = skb_clone(skb, GFP_ATOMIC);
 565                 else {
 566                         skb2 = skb;
 567                         skb = NULL;
 568                 }
 569
 570                 if (skb2) {
 571                         ip6_mr_input(skb2);
 572                 }
 573         }
 574 out:
 575 #endif
 576         if (likely(deliver))
 577                 ip6_input(skb);
 578         else {
 579                 /* discard */
 580                 kfree_skb(skb);
 581         }
 582
 583         return 0;
 584 }