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 void udp_v6_early_demux(struct sk_buff *);
  48 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         if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
  53             !skb_dst(skb) && !skb->sk) {
  54                 switch (ipv6_hdr(skb)->nexthdr) {
  55                 case IPPROTO_TCP:
  56                         if (READ_ONCE(net->ipv4.sysctl_tcp_early_demux))
  57                                 tcp_v6_early_demux(skb);
  58                         break;
  59                 case IPPROTO_UDP:
  60                         if (READ_ONCE(net->ipv4.sysctl_udp_early_demux))
  61                                 udp_v6_early_demux(skb);
  62                         break;
  63                 }
  64         }
  65
  66         if (!skb_valid_dst(skb))
  67                 ip6_route_input(skb);
  68 }
  69
  70 int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  71 {
  72         /* if ingress device is enslaved to an L3 master device pass the
  73          * skb to its handler for processing
  74          */
  75         skb = l3mdev_ip6_rcv(skb);
  76         if (!skb)
  77                 return NET_RX_SUCCESS;
  78         ip6_rcv_finish_core(net, sk, skb);
  79
  80         return dst_input(skb);
  81 }
  82
  83 static void ip6_sublist_rcv_finish(struct list_head *head)
  84 {
  85         struct sk_buff *skb, *next;
  86
  87         list_for_each_entry_safe(skb, next, head, list) {
  88                 skb_list_del_init(skb);
  89                 dst_input(skb);
  90         }
  91 }
  92
  93 static bool ip6_can_use_hint(const struct sk_buff *skb,
  94                              const struct sk_buff *hint)
  95 {
  96         return hint && !skb_dst(skb) &&
  97                ipv6_addr_equal(&ipv6_hdr(hint)->daddr, &ipv6_hdr(skb)->daddr);
  98 }
  99
 100 static struct sk_buff *ip6_extract_route_hint(const struct net *net,
 101                                               struct sk_buff *skb)
 102 {
 103         if (fib6_routes_require_src(net) || fib6_has_custom_rules(net))
 104                 return NULL;
 105
 106         return skb;
 107 }
 108
 109 static void ip6_list_rcv_finish(struct net *net, struct sock *sk,
 110                                 struct list_head *head)
 111 {
 112         struct sk_buff *skb, *next, *hint = NULL;
 113         struct dst_entry *curr_dst = NULL;
 114         struct list_head sublist;
 115
 116         INIT_LIST_HEAD(&sublist);
 117         list_for_each_entry_safe(skb, next, head, list) {
 118                 struct dst_entry *dst;
 119
 120                 skb_list_del_init(skb);
 121                 /* if ingress device is enslaved to an L3 master device pass the
 122                  * skb to its handler for processing
 123                  */
 124                 skb = l3mdev_ip6_rcv(skb);
 125                 if (!skb)
 126                         continue;
 127
 128                 if (ip6_can_use_hint(skb, hint))
 129                         skb_dst_copy(skb, hint);
 130                 else
 131                         ip6_rcv_finish_core(net, sk, skb);
 132                 dst = skb_dst(skb);
 133                 if (curr_dst != dst) {
 134                         hint = ip6_extract_route_hint(net, skb);
 135
 136                         /* dispatch old sublist */
 137                         if (!list_empty(&sublist))
 138                                 ip6_sublist_rcv_finish(&sublist);
 139                         /* start new sublist */
 140                         INIT_LIST_HEAD(&sublist);
 141                         curr_dst = dst;
 142                 }
 143                 list_add_tail(&skb->list, &sublist);
 144         }
 145         /* dispatch final sublist */
 146         ip6_sublist_rcv_finish(&sublist);
 147 }
 148
 149 static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
 150                                     struct net *net)
 151 {
 152         const struct ipv6hdr *hdr;
 153         u32 pkt_len;
 154         struct inet6_dev *idev;
 155
 156         if (skb->pkt_type == PACKET_OTHERHOST) {
 157                 kfree_skb(skb);
 158                 return NULL;
 159         }
 160
 161         rcu_read_lock();
 162
 163         idev = __in6_dev_get(skb->dev);
 164
 165         __IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
 166
 167         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
 168             !idev || unlikely(idev->cnf.disable_ipv6)) {
 169                 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 170                 goto drop;
 171         }
 172
 173         memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
 174
 175         /*
 176          * Store incoming device index. When the packet will
 177          * be queued, we cannot refer to skb->dev anymore.
 178          *
 179          * BTW, when we send a packet for our own local address on a
 180          * non-loopback interface (e.g. ethX), it is being delivered
 181          * via the loopback interface (lo) here; skb->dev = loopback_dev.
 182          * It, however, should be considered as if it is being
 183          * arrived via the sending interface (ethX), because of the
 184          * nature of scoping architecture. --yoshfuji
 185          */
 186         IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
 187
 188         if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
 189                 goto err;
 190
 191         hdr = ipv6_hdr(skb);
 192
 193         if (hdr->version != 6)
 194                 goto err;
 195
 196         __IP6_ADD_STATS(net, idev,
 197                         IPSTATS_MIB_NOECTPKTS +
 198                                 (ipv6_get_dsfield(hdr) & INET_ECN_MASK),
 199                         max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
 200         /*
 201          * RFC4291 2.5.3
 202          * The loopback address must not be used as the source address in IPv6
 203          * packets that are sent outside of a single node. [..]
 204          * A packet received on an interface with a destination address
 205          * of loopback must be dropped.
 206          */
 207         if ((ipv6_addr_loopback(&hdr->saddr) ||
 208              ipv6_addr_loopback(&hdr->daddr)) &&
 209             !(dev->flags & IFF_LOOPBACK) &&
 210             !netif_is_l3_master(dev))
 211                 goto err;
 212
 213         /* RFC4291 Errata ID: 3480
 214          * Interface-Local scope spans only a single interface on a
 215          * node and is useful only for loopback transmission of
 216          * multicast.  Packets with interface-local scope received
 217          * from another node must be discarded.
 218          */
 219         if (!(skb->pkt_type == PACKET_LOOPBACK ||
 220               dev->flags & IFF_LOOPBACK) &&
 221             ipv6_addr_is_multicast(&hdr->daddr) &&
 222             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
 223                 goto err;
 224
 225         /* If enabled, drop unicast packets that were encapsulated in link-layer
 226          * multicast or broadcast to protected against the so-called "hole-196"
 227          * attack in 802.11 wireless.
 228          */
 229         if (!ipv6_addr_is_multicast(&hdr->daddr) &&
 230             (skb->pkt_type == PACKET_BROADCAST ||
 231              skb->pkt_type == PACKET_MULTICAST) &&
 232             idev->cnf.drop_unicast_in_l2_multicast)
 233                 goto err;
 234
 235         /* RFC4291 2.7
 236          * Nodes must not originate a packet to a multicast address whose scope
 237          * field contains the reserved value 0; if such a packet is received, it
 238          * must be silently dropped.
 239          */
 240         if (ipv6_addr_is_multicast(&hdr->daddr) &&
 241             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
 242                 goto err;
 243
 244         /*
 245          * RFC4291 2.7
 246          * Multicast addresses must not be used as source addresses in IPv6
 247          * packets or appear in any Routing header.
 248          */
 249         if (ipv6_addr_is_multicast(&hdr->saddr))
 250                 goto err;
 251
 252         skb->transport_header = skb->network_header + sizeof(*hdr);
 253         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
 254
 255         pkt_len = ntohs(hdr->payload_len);
 256
 257         /* pkt_len may be zero if Jumbo payload option is present */
 258         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
 259                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
 260                         __IP6_INC_STATS(net,
 261                                         idev, IPSTATS_MIB_INTRUNCATEDPKTS);
 262                         goto drop;
 263                 }
 264                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
 265                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 266                         goto drop;
 267                 }
 268                 hdr = ipv6_hdr(skb);
 269         }
 270
 271         if (hdr->nexthdr == NEXTHDR_HOP) {
 272                 if (ipv6_parse_hopopts(skb) < 0) {
 273                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 274                         rcu_read_unlock();
 275                         return NULL;
 276                 }
 277         }
 278
 279         rcu_read_unlock();
 280
 281         /* Must drop socket now because of tproxy. */
 282         if (!skb_sk_is_prefetched(skb))
 283                 skb_orphan(skb);
 284
 285         return skb;
 286 err:
 287         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 288 drop:
 289         rcu_read_unlock();
 290         kfree_skb(skb);
 291         return NULL;
 292 }
 293
 294 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 295 {
 296         struct net *net = dev_net(skb->dev);
 297
 298         skb = ip6_rcv_core(skb, dev, net);
 299         if (skb == NULL)
 300                 return NET_RX_DROP;
 301         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
 302                        net, NULL, skb, dev, NULL,
 303                        ip6_rcv_finish);
 304 }
 305
 306 static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
 307                             struct net *net)
 308 {
 309         NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
 310                      head, dev, NULL, ip6_rcv_finish);
 311         ip6_list_rcv_finish(net, NULL, head);
 312 }
 313
 314 /* Receive a list of IPv6 packets */
 315 void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
 316                    struct net_device *orig_dev)
 317 {
 318         struct net_device *curr_dev = NULL;
 319         struct net *curr_net = NULL;
 320         struct sk_buff *skb, *next;
 321         struct list_head sublist;
 322
 323         INIT_LIST_HEAD(&sublist);
 324         list_for_each_entry_safe(skb, next, head, list) {
 325                 struct net_device *dev = skb->dev;
 326                 struct net *net = dev_net(dev);
 327
 328                 skb_list_del_init(skb);
 329                 skb = ip6_rcv_core(skb, dev, net);
 330                 if (skb == NULL)
 331                         continue;
 332
 333                 if (curr_dev != dev || curr_net != net) {
 334                         /* dispatch old sublist */
 335                         if (!list_empty(&sublist))
 336                                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 337                         /* start new sublist */
 338                         INIT_LIST_HEAD(&sublist);
 339                         curr_dev = dev;
 340                         curr_net = net;
 341                 }
 342                 list_add_tail(&skb->list, &sublist);
 343         }
 344         /* dispatch final sublist */
 345         if (!list_empty(&sublist))
 346                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 347 }
 348
 349 INDIRECT_CALLABLE_DECLARE(int udpv6_rcv(struct sk_buff *));
 350 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
 351
 352 /*
 353  *      Deliver the packet to the host
 354  */
 355 void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
 356                               bool have_final)
 357 {
 358         const struct inet6_protocol *ipprot;
 359         struct inet6_dev *idev;
 360         unsigned int nhoff;
 361         bool raw;
 362
 363         /*
 364          *      Parse extension headers
 365          */
 366
 367 resubmit:
 368         idev = ip6_dst_idev(skb_dst(skb));
 369         nhoff = IP6CB(skb)->nhoff;
 370         if (!have_final) {
 371                 if (!pskb_pull(skb, skb_transport_offset(skb)))
 372                         goto discard;
 373                 nexthdr = skb_network_header(skb)[nhoff];
 374         }
 375
 376 resubmit_final:
 377         raw = raw6_local_deliver(skb, nexthdr);
 378         ipprot = rcu_dereference(inet6_protos[nexthdr]);
 379         if (ipprot) {
 380                 int ret;
 381
 382                 if (have_final) {
 383                         if (!(ipprot->flags & INET6_PROTO_FINAL)) {
 384                                 /* Once we've seen a final protocol don't
 385                                  * allow encapsulation on any non-final
 386                                  * ones. This allows foo in UDP encapsulation
 387                                  * to work.
 388                                  */
 389                                 goto discard;
 390                         }
 391                 } else if (ipprot->flags & INET6_PROTO_FINAL) {
 392                         const struct ipv6hdr *hdr;
 393                         int sdif = inet6_sdif(skb);
 394                         struct net_device *dev;
 395
 396                         /* Only do this once for first final protocol */
 397                         have_final = true;
 398
 399                         /* Free reference early: we don't need it any more,
 400                            and it may hold ip_conntrack module loaded
 401                            indefinitely. */
 402                         nf_reset_ct(skb);
 403
 404                         skb_postpull_rcsum(skb, skb_network_header(skb),
 405                                            skb_network_header_len(skb));
 406                         hdr = ipv6_hdr(skb);
 407
 408                         /* skb->dev passed may be master dev for vrfs. */
 409                         if (sdif) {
 410                                 dev = dev_get_by_index_rcu(net, sdif);
 411                                 if (!dev)
 412                                         goto discard;
 413                         } else {
 414                                 dev = skb->dev;
 415                         }
 416
 417                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
 418                             !ipv6_chk_mcast_addr(dev, &hdr->daddr,
 419                                                  &hdr->saddr) &&
 420                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
 421                                 goto discard;
 422                 }
 423                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
 424                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
 425                         goto discard;
 426
 427                 ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
 428                                       skb);
 429                 if (ret > 0) {
 430                         if (ipprot->flags & INET6_PROTO_FINAL) {
 431                                 /* Not an extension header, most likely UDP
 432                                  * encapsulation. Use return value as nexthdr
 433                                  * protocol not nhoff (which presumably is
 434                                  * not set by handler).
 435                                  */
 436                                 nexthdr = ret;
 437                                 goto resubmit_final;
 438                         } else {
 439                                 goto resubmit;
 440                         }
 441                 } else if (ret == 0) {
 442                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 443                 }
 444         } else {
 445                 if (!raw) {
 446                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 447                                 __IP6_INC_STATS(net, idev,
 448                                                 IPSTATS_MIB_INUNKNOWNPROTOS);
 449                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
 450                                             ICMPV6_UNK_NEXTHDR, nhoff);
 451                         }
 452                         kfree_skb(skb);
 453                 } else {
 454                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
 455                         consume_skb(skb);
 456                 }
 457         }
 458         return;
 459
 460 discard:
 461         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 462         kfree_skb(skb);
 463 }
 464
 465 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 466 {
 467         rcu_read_lock();
 468         ip6_protocol_deliver_rcu(net, skb, 0, false);
 469         rcu_read_unlock();
 470
 471         return 0;
 472 }
 473
 474
 475 int ip6_input(struct sk_buff *skb)
 476 {
 477         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
 478                        dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 479                        ip6_input_finish);
 480 }
 481 EXPORT_SYMBOL_GPL(ip6_input);
 482
 483 int ip6_mc_input(struct sk_buff *skb)
 484 {
 485         int sdif = inet6_sdif(skb);
 486         const struct ipv6hdr *hdr;
 487         struct net_device *dev;
 488         bool deliver;
 489
 490         __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
 491                          __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
 492                          skb->len);
 493
 494         /* skb->dev passed may be master dev for vrfs. */
 495         if (sdif) {
 496                 rcu_read_lock();
 497                 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
 498                 if (!dev) {
 499                         rcu_read_unlock();
 500                         kfree_skb(skb);
 501                         return -ENODEV;
 502                 }
 503         } else {
 504                 dev = skb->dev;
 505         }
 506
 507         hdr = ipv6_hdr(skb);
 508         deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
 509         if (sdif)
 510                 rcu_read_unlock();
 511
 512 #ifdef CONFIG_IPV6_MROUTE
 513         /*
 514          *      IPv6 multicast router mode is now supported ;)
 515          */
 516         if (atomic_read(&dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding) &&
 517             !(ipv6_addr_type(&hdr->daddr) &
 518               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
 519             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
 520                 /*
 521                  * Okay, we try to forward - split and duplicate
 522                  * packets.
 523                  */
 524                 struct sk_buff *skb2;
 525                 struct inet6_skb_parm *opt = IP6CB(skb);
 526
 527                 /* Check for MLD */
 528                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
 529                         /* Check if this is a mld message */
 530                         u8 nexthdr = hdr->nexthdr;
 531                         __be16 frag_off;
 532                         int offset;
 533
 534                         /* Check if the value of Router Alert
 535                          * is for MLD (0x0000).
 536                          */
 537                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
 538                                 deliver = false;
 539
 540                                 if (!ipv6_ext_hdr(nexthdr)) {
 541                                         /* BUG */
 542                                         goto out;
 543                                 }
 544                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
 545                                                           &nexthdr, &frag_off);
 546                                 if (offset < 0)
 547                                         goto out;
 548
 549                                 if (ipv6_is_mld(skb, nexthdr, offset))
 550                                         deliver = true;
 551
 552                                 goto out;
 553                         }
 554                         /* unknown RA - process it normally */
 555                 }
 556
 557                 if (deliver)
 558                         skb2 = skb_clone(skb, GFP_ATOMIC);
 559                 else {
 560                         skb2 = skb;
 561                         skb = NULL;
 562                 }
 563
 564                 if (skb2) {
 565                         ip6_mr_input(skb2);
 566                 }
 567         }
 568 out:
 569 #endif
 570         if (likely(deliver))
 571                 ip6_input(skb);
 572         else {
 573                 /* discard */
 574                 kfree_skb(skb);
 575         }
 576
 577         return 0;
 578 }