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         skb_orphan(skb);
 289
 290         return skb;
 291 err:
 292         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 293 drop:
 294         rcu_read_unlock();
 295         kfree_skb(skb);
 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 udpv6_rcv(struct sk_buff *));
 355 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
 356
 357 /*
 358  *      Deliver the packet to the host
 359  */
 360 void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
 361                               bool have_final)
 362 {
 363         const struct inet6_protocol *ipprot;
 364         struct inet6_dev *idev;
 365         unsigned int nhoff;
 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                                 goto discard;
 427                 }
 428                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
 429                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
 430                         goto discard;
 431
 432                 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
 433                                       skb);
 434                 if (ret > 0) {
 435                         if (ipprot->flags & INET6_PROTO_FINAL) {
 436                                 /* Not an extension header, most likely UDP
 437                                  * encapsulation. Use return value as nexthdr
 438                                  * protocol not nhoff (which presumably is
 439                                  * not set by handler).
 440                                  */
 441                                 nexthdr = ret;
 442                                 goto resubmit_final;
 443                         } else {
 444                                 goto resubmit;
 445                         }
 446                 } else if (ret == 0) {
 447                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 448                 }
 449         } else {
 450                 if (!raw) {
 451                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 452                                 __IP6_INC_STATS(net, idev,
 453                                                 IPSTATS_MIB_INUNKNOWNPROTOS);
 454                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
 455                                             ICMPV6_UNK_NEXTHDR, nhoff);
 456                         }
 457                         kfree_skb(skb);
 458                 } else {
 459                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 460                         consume_skb(skb);
 461                 }
 462         }
 463         return;
 464
 465 discard:
 466         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 467         kfree_skb(skb);
 468 }
 469
 470 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 471 {
 472         rcu_read_lock();
 473         ip6_protocol_deliver_rcu(net, skb, 0, false);
 474         rcu_read_unlock();
 475
 476         return 0;
 477 }
 478
 479
 480 int ip6_input(struct sk_buff *skb)
 481 {
 482         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
 483                        dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 484                        ip6_input_finish);
 485 }
 486 EXPORT_SYMBOL_GPL(ip6_input);
 487
 488 int ip6_mc_input(struct sk_buff *skb)
 489 {
 490         int sdif = inet6_sdif(skb);
 491         const struct ipv6hdr *hdr;
 492         struct net_device *dev;
 493         bool deliver;
 494
 495         __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
 496                          __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
 497                          skb->len);
 498
 499         /* skb->dev passed may be master dev for vrfs. */
 500         if (sdif) {
 501                 rcu_read_lock();
 502                 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
 503                 if (!dev) {
 504                         rcu_read_unlock();
 505                         kfree_skb(skb);
 506                         return -ENODEV;
 507                 }
 508         } else {
 509                 dev = skb->dev;
 510         }
 511
 512         hdr = ipv6_hdr(skb);
 513         deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
 514         if (sdif)
 515                 rcu_read_unlock();
 516
 517 #ifdef CONFIG_IPV6_MROUTE
 518         /*
 519          *      IPv6 multicast router mode is now supported ;)
 520          */
 521         if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
 522             !(ipv6_addr_type(&hdr->daddr) &
 523               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
 524             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
 525                 /*
 526                  * Okay, we try to forward - split and duplicate
 527                  * packets.
 528                  */
 529                 struct sk_buff *skb2;
 530                 struct inet6_skb_parm *opt = IP6CB(skb);
 531
 532                 /* Check for MLD */
 533                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
 534                         /* Check if this is a mld message */
 535                         u8 nexthdr = hdr->nexthdr;
 536                         __be16 frag_off;
 537                         int offset;
 538
 539                         /* Check if the value of Router Alert
 540                          * is for MLD (0x0000).
 541                          */
 542                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
 543                                 deliver = false;
 544
 545                                 if (!ipv6_ext_hdr(nexthdr)) {
 546                                         /* BUG */
 547                                         goto out;
 548                                 }
 549                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
 550                                                           &nexthdr, &frag_off);
 551                                 if (offset < 0)
 552                                         goto out;
 553
 554                                 if (ipv6_is_mld(skb, nexthdr, offset))
 555                                         deliver = true;
 556
 557                                 goto out;
 558                         }
 559                         /* unknown RA - process it normally */
 560                 }
 561
 562                 if (deliver)
 563                         skb2 = skb_clone(skb, GFP_ATOMIC);
 564                 else {
 565                         skb2 = skb;
 566                         skb = NULL;
 567                 }
 568
 569                 if (skb2) {
 570                         ip6_mr_input(skb2);
 571                 }
 572         }
 573 out:
 574 #endif
 575         if (likely(deliver))
 576                 ip6_input(skb);
 577         else {
 578                 /* discard */
 579                 kfree_skb(skb);
 580         }
 581
 582         return 0;
 583 }