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         enum skb_drop_reason reason;
 149         const struct ipv6hdr *hdr;
 150         u32 pkt_len;
 151         struct inet6_dev *idev;
 152
 153         if (skb->pkt_type == PACKET_OTHERHOST) {
 154                 dev_core_stats_rx_otherhost_dropped_inc(skb->dev);
 155                 kfree_skb_reason(skb, SKB_DROP_REASON_OTHERHOST);
 156                 return NULL;
 157         }
 158
 159         rcu_read_lock();
 160
 161         idev = __in6_dev_get(skb->dev);
 162
 163         __IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
 164
 165         SKB_DR_SET(reason, NOT_SPECIFIED);
 166         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
 167             !idev || unlikely(idev->cnf.disable_ipv6)) {
 168                 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 169                 if (idev && unlikely(idev->cnf.disable_ipv6))
 170                         SKB_DR_SET(reason, IPV6DISABLED);
 171                 goto drop;
 172         }
 173
 174         memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
 175
 176         /*
 177          * Store incoming device index. When the packet will
 178          * be queued, we cannot refer to skb->dev anymore.
 179          *
 180          * BTW, when we send a packet for our own local address on a
 181          * non-loopback interface (e.g. ethX), it is being delivered
 182          * via the loopback interface (lo) here; skb->dev = loopback_dev.
 183          * It, however, should be considered as if it is being
 184          * arrived via the sending interface (ethX), because of the
 185          * nature of scoping architecture. --yoshfuji
 186          */
 187         IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
 188
 189         if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
 190                 goto err;
 191
 192         hdr = ipv6_hdr(skb);
 193
 194         if (hdr->version != 6) {
 195                 SKB_DR_SET(reason, UNHANDLED_PROTO);
 196                 goto err;
 197         }
 198
 199         __IP6_ADD_STATS(net, idev,
 200                         IPSTATS_MIB_NOECTPKTS +
 201                                 (ipv6_get_dsfield(hdr) & INET_ECN_MASK),
 202                         max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
 203         /*
 204          * RFC4291 2.5.3
 205          * The loopback address must not be used as the source address in IPv6
 206          * packets that are sent outside of a single node. [..]
 207          * A packet received on an interface with a destination address
 208          * of loopback must be dropped.
 209          */
 210         if ((ipv6_addr_loopback(&hdr->saddr) ||
 211              ipv6_addr_loopback(&hdr->daddr)) &&
 212             !(dev->flags & IFF_LOOPBACK) &&
 213             !netif_is_l3_master(dev))
 214                 goto err;
 215
 216         /* RFC4291 Errata ID: 3480
 217          * Interface-Local scope spans only a single interface on a
 218          * node and is useful only for loopback transmission of
 219          * multicast.  Packets with interface-local scope received
 220          * from another node must be discarded.
 221          */
 222         if (!(skb->pkt_type == PACKET_LOOPBACK ||
 223               dev->flags & IFF_LOOPBACK) &&
 224             ipv6_addr_is_multicast(&hdr->daddr) &&
 225             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
 226                 goto err;
 227
 228         /* If enabled, drop unicast packets that were encapsulated in link-layer
 229          * multicast or broadcast to protected against the so-called "hole-196"
 230          * attack in 802.11 wireless.
 231          */
 232         if (!ipv6_addr_is_multicast(&hdr->daddr) &&
 233             (skb->pkt_type == PACKET_BROADCAST ||
 234              skb->pkt_type == PACKET_MULTICAST) &&
 235             idev->cnf.drop_unicast_in_l2_multicast) {
 236                 SKB_DR_SET(reason, UNICAST_IN_L2_MULTICAST);
 237                 goto err;
 238         }
 239
 240         /* RFC4291 2.7
 241          * Nodes must not originate a packet to a multicast address whose scope
 242          * field contains the reserved value 0; if such a packet is received, it
 243          * must be silently dropped.
 244          */
 245         if (ipv6_addr_is_multicast(&hdr->daddr) &&
 246             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
 247                 goto err;
 248
 249         /*
 250          * RFC4291 2.7
 251          * Multicast addresses must not be used as source addresses in IPv6
 252          * packets or appear in any Routing header.
 253          */
 254         if (ipv6_addr_is_multicast(&hdr->saddr))
 255                 goto err;
 256
 257         skb->transport_header = skb->network_header + sizeof(*hdr);
 258         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
 259
 260         pkt_len = ntohs(hdr->payload_len);
 261
 262         /* pkt_len may be zero if Jumbo payload option is present */
 263         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
 264                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
 265                         __IP6_INC_STATS(net,
 266                                         idev, IPSTATS_MIB_INTRUNCATEDPKTS);
 267                         SKB_DR_SET(reason, PKT_TOO_SMALL);
 268                         goto drop;
 269                 }
 270                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
 271                         goto err;
 272                 hdr = ipv6_hdr(skb);
 273         }
 274
 275         if (hdr->nexthdr == NEXTHDR_HOP) {
 276                 if (ipv6_parse_hopopts(skb) < 0) {
 277                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 278                         rcu_read_unlock();
 279                         return NULL;
 280                 }
 281         }
 282
 283         rcu_read_unlock();
 284
 285         /* Must drop socket now because of tproxy. */
 286         if (!skb_sk_is_prefetched(skb))
 287                 skb_orphan(skb);
 288
 289         return skb;
 290 err:
 291         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 292         SKB_DR_OR(reason, IP_INHDR);
 293 drop:
 294         rcu_read_unlock();
 295         kfree_skb_reason(skb, reason);
 296         return NULL;
 297 }
 298
 299 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 300 {
 301         struct net *net = dev_net(skb->dev);
 302
 303         skb = ip6_rcv_core(skb, dev, net);
 304         if (skb == NULL)
 305                 return NET_RX_DROP;
 306         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
 307                        net, NULL, skb, dev, NULL,
 308                        ip6_rcv_finish);
 309 }
 310
 311 static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
 312                             struct net *net)
 313 {
 314         NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
 315                      head, dev, NULL, ip6_rcv_finish);
 316         ip6_list_rcv_finish(net, NULL, head);
 317 }
 318
 319 /* Receive a list of IPv6 packets */
 320 void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
 321                    struct net_device *orig_dev)
 322 {
 323         struct net_device *curr_dev = NULL;
 324         struct net *curr_net = NULL;
 325         struct sk_buff *skb, *next;
 326         struct list_head sublist;
 327
 328         INIT_LIST_HEAD(&sublist);
 329         list_for_each_entry_safe(skb, next, head, list) {
 330                 struct net_device *dev = skb->dev;
 331                 struct net *net = dev_net(dev);
 332
 333                 skb_list_del_init(skb);
 334                 skb = ip6_rcv_core(skb, dev, net);
 335                 if (skb == NULL)
 336                         continue;
 337
 338                 if (curr_dev != dev || curr_net != net) {
 339                         /* dispatch old sublist */
 340                         if (!list_empty(&sublist))
 341                                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 342                         /* start new sublist */
 343                         INIT_LIST_HEAD(&sublist);
 344                         curr_dev = dev;
 345                         curr_net = net;
 346                 }
 347                 list_add_tail(&skb->list, &sublist);
 348         }
 349         /* dispatch final sublist */
 350         if (!list_empty(&sublist))
 351                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 352 }
 353
 354 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
 355
 356 /*
 357  *      Deliver the packet to the host
 358  */
 359 void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
 360                               bool have_final)
 361 {
 362         const struct inet6_protocol *ipprot;
 363         struct inet6_dev *idev;
 364         unsigned int nhoff;
 365         SKB_DR(reason);
 366         bool raw;
 367
 368         /*
 369          *      Parse extension headers
 370          */
 371
 372 resubmit:
 373         idev = ip6_dst_idev(skb_dst(skb));
 374         nhoff = IP6CB(skb)->nhoff;
 375         if (!have_final) {
 376                 if (!pskb_pull(skb, skb_transport_offset(skb)))
 377                         goto discard;
 378                 nexthdr = skb_network_header(skb)[nhoff];
 379         }
 380
 381 resubmit_final:
 382         raw = raw6_local_deliver(skb, nexthdr);
 383         ipprot = rcu_dereference(inet6_protos[nexthdr]);
 384         if (ipprot) {
 385                 int ret;
 386
 387                 if (have_final) {
 388                         if (!(ipprot->flags & INET6_PROTO_FINAL)) {
 389                                 /* Once we've seen a final protocol don't
 390                                  * allow encapsulation on any non-final
 391                                  * ones. This allows foo in UDP encapsulation
 392                                  * to work.
 393                                  */
 394                                 goto discard;
 395                         }
 396                 } else if (ipprot->flags & INET6_PROTO_FINAL) {
 397                         const struct ipv6hdr *hdr;
 398                         int sdif = inet6_sdif(skb);
 399                         struct net_device *dev;
 400
 401                         /* Only do this once for first final protocol */
 402                         have_final = true;
 403
 404                         /* Free reference early: we don't need it any more,
 405                            and it may hold ip_conntrack module loaded
 406                            indefinitely. */
 407                         nf_reset_ct(skb);
 408
 409                         skb_postpull_rcsum(skb, skb_network_header(skb),
 410                                            skb_network_header_len(skb));
 411                         hdr = ipv6_hdr(skb);
 412
 413                         /* skb->dev passed may be master dev for vrfs. */
 414                         if (sdif) {
 415                                 dev = dev_get_by_index_rcu(net, sdif);
 416                                 if (!dev)
 417                                         goto discard;
 418                         } else {
 419                                 dev = skb->dev;
 420                         }
 421
 422                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
 423                             !ipv6_chk_mcast_addr(dev, &hdr->daddr,
 424                                                  &hdr->saddr) &&
 425                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb))) {
 426                                 SKB_DR_SET(reason, IP_INADDRERRORS);
 427                                 goto discard;
 428                         }
 429                 }
 430                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
 431                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 432                         SKB_DR_SET(reason, XFRM_POLICY);
 433                         goto discard;
 434                 }
 435
 436                 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
 437                                       skb);
 438                 if (ret > 0) {
 439                         if (ipprot->flags & INET6_PROTO_FINAL) {
 440                                 /* Not an extension header, most likely UDP
 441                                  * encapsulation. Use return value as nexthdr
 442                                  * protocol not nhoff (which presumably is
 443                                  * not set by handler).
 444                                  */
 445                                 nexthdr = ret;
 446                                 goto resubmit_final;
 447                         } else {
 448                                 goto resubmit;
 449                         }
 450                 } else if (ret == 0) {
 451                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 452                 }
 453         } else {
 454                 if (!raw) {
 455                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 456                                 __IP6_INC_STATS(net, idev,
 457                                                 IPSTATS_MIB_INUNKNOWNPROTOS);
 458                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
 459                                             ICMPV6_UNK_NEXTHDR, nhoff);
 460                                 SKB_DR_SET(reason, IP_NOPROTO);
 461                         } else {
 462                                 SKB_DR_SET(reason, XFRM_POLICY);
 463                         }
 464                         kfree_skb_reason(skb, reason);
 465                 } else {
 466                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 467                         consume_skb(skb);
 468                 }
 469         }
 470         return;
 471
 472 discard:
 473         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 474         kfree_skb_reason(skb, reason);
 475 }
 476
 477 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 478 {
 479         skb_clear_delivery_time(skb);
 480         rcu_read_lock();
 481         ip6_protocol_deliver_rcu(net, skb, 0, false);
 482         rcu_read_unlock();
 483
 484         return 0;
 485 }
 486
 487
 488 int ip6_input(struct sk_buff *skb)
 489 {
 490         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
 491                        dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 492                        ip6_input_finish);
 493 }
 494 EXPORT_SYMBOL_GPL(ip6_input);
 495
 496 int ip6_mc_input(struct sk_buff *skb)
 497 {
 498         int sdif = inet6_sdif(skb);
 499         const struct ipv6hdr *hdr;
 500         struct net_device *dev;
 501         bool deliver;
 502
 503         __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
 504                          __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
 505                          skb->len);
 506
 507         /* skb->dev passed may be master dev for vrfs. */
 508         if (sdif) {
 509                 rcu_read_lock();
 510                 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
 511                 if (!dev) {
 512                         rcu_read_unlock();
 513                         kfree_skb(skb);
 514                         return -ENODEV;
 515                 }
 516         } else {
 517                 dev = skb->dev;
 518         }
 519
 520         hdr = ipv6_hdr(skb);
 521         deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
 522         if (sdif)
 523                 rcu_read_unlock();
 524
 525 #ifdef CONFIG_IPV6_MROUTE
 526         /*
 527          *      IPv6 multicast router mode is now supported ;)
 528          */
 529         if (atomic_read(&dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding) &&
 530             !(ipv6_addr_type(&hdr->daddr) &
 531               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
 532             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
 533                 /*
 534                  * Okay, we try to forward - split and duplicate
 535                  * packets.
 536                  */
 537                 struct sk_buff *skb2;
 538                 struct inet6_skb_parm *opt = IP6CB(skb);
 539
 540                 /* Check for MLD */
 541                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
 542                         /* Check if this is a mld message */
 543                         u8 nexthdr = hdr->nexthdr;
 544                         __be16 frag_off;
 545                         int offset;
 546
 547                         /* Check if the value of Router Alert
 548                          * is for MLD (0x0000).
 549                          */
 550                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
 551                                 deliver = false;
 552
 553                                 if (!ipv6_ext_hdr(nexthdr)) {
 554                                         /* BUG */
 555                                         goto out;
 556                                 }
 557                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
 558                                                           &nexthdr, &frag_off);
 559                                 if (offset < 0)
 560                                         goto out;
 561
 562                                 if (ipv6_is_mld(skb, nexthdr, offset))
 563                                         deliver = true;
 564
 565                                 goto out;
 566                         }
 567                         /* unknown RA - process it normally */
 568                 }
 569
 570                 if (deliver)
 571                         skb2 = skb_clone(skb, GFP_ATOMIC);
 572                 else {
 573                         skb2 = skb;
 574                         skb = NULL;
 575                 }
 576
 577                 if (skb2) {
 578                         ip6_mr_input(skb2);
 579                 }
 580         }
 581 out:
 582 #endif
 583         if (likely(deliver))
 584                 ip6_input(skb);
 585         else {
 586                 /* discard */
 587                 kfree_skb(skb);
 588         }
 589
 590         return 0;
 591 }