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 static void ip6_rcv_finish_core(struct net *net, struct sock *sk,
  49                                 struct sk_buff *skb)
  50 {
  51         if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
  52             !skb_dst(skb) && !skb->sk) {
  53                 switch (ipv6_hdr(skb)->nexthdr) {
  54                 case IPPROTO_TCP:
  55                         if (READ_ONCE(net->ipv4.sysctl_tcp_early_demux))
  56                                 tcp_v6_early_demux(skb);
  57                         break;
  58                 case IPPROTO_UDP:
  59                         if (READ_ONCE(net->ipv4.sysctl_udp_early_demux))
  60                                 udp_v6_early_demux(skb);
  61                         break;
  62                 }
  63         }
  64
  65         if (!skb_valid_dst(skb))
  66                 ip6_route_input(skb);
  67 }
  68
  69 int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  70 {
  71         /* if ingress device is enslaved to an L3 master device pass the
  72          * skb to its handler for processing
  73          */
  74         skb = l3mdev_ip6_rcv(skb);
  75         if (!skb)
  76                 return NET_RX_SUCCESS;
  77         ip6_rcv_finish_core(net, sk, skb);
  78
  79         return dst_input(skb);
  80 }
  81
  82 static void ip6_sublist_rcv_finish(struct list_head *head)
  83 {
  84         struct sk_buff *skb, *next;
  85
  86         list_for_each_entry_safe(skb, next, head, list) {
  87                 skb_list_del_init(skb);
  88                 dst_input(skb);
  89         }
  90 }
  91
  92 static bool ip6_can_use_hint(const struct sk_buff *skb,
  93                              const struct sk_buff *hint)
  94 {
  95         return hint && !skb_dst(skb) &&
  96                ipv6_addr_equal(&ipv6_hdr(hint)->daddr, &ipv6_hdr(skb)->daddr);
  97 }
  98
  99 static struct sk_buff *ip6_extract_route_hint(const struct net *net,
 100                                               struct sk_buff *skb)
 101 {
 102         if (fib6_routes_require_src(net) || fib6_has_custom_rules(net) ||
 103             IP6CB(skb)->flags & IP6SKB_MULTIPATH)
 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         LIST_HEAD(sublist);
 115
 116         list_for_each_entry_safe(skb, next, head, list) {
 117                 struct dst_entry *dst;
 118
 119                 skb_list_del_init(skb);
 120                 /* if ingress device is enslaved to an L3 master device pass the
 121                  * skb to its handler for processing
 122                  */
 123                 skb = l3mdev_ip6_rcv(skb);
 124                 if (!skb)
 125                         continue;
 126
 127                 if (ip6_can_use_hint(skb, hint))
 128                         skb_dst_copy(skb, hint);
 129                 else
 130                         ip6_rcv_finish_core(net, sk, skb);
 131                 dst = skb_dst(skb);
 132                 if (curr_dst != dst) {
 133                         hint = ip6_extract_route_hint(net, skb);
 134
 135                         /* dispatch old sublist */
 136                         if (!list_empty(&sublist))
 137                                 ip6_sublist_rcv_finish(&sublist);
 138                         /* start new sublist */
 139                         INIT_LIST_HEAD(&sublist);
 140                         curr_dst = dst;
 141                 }
 142                 list_add_tail(&skb->list, &sublist);
 143         }
 144         /* dispatch final sublist */
 145         ip6_sublist_rcv_finish(&sublist);
 146 }
 147
 148 static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
 149                                     struct net *net)
 150 {
 151         enum skb_drop_reason reason;
 152         const struct ipv6hdr *hdr;
 153         u32 pkt_len;
 154         struct inet6_dev *idev;
 155
 156         if (skb->pkt_type == PACKET_OTHERHOST) {
 157                 dev_core_stats_rx_otherhost_dropped_inc(skb->dev);
 158                 kfree_skb_reason(skb, SKB_DROP_REASON_OTHERHOST);
 159                 return NULL;
 160         }
 161
 162         rcu_read_lock();
 163
 164         idev = __in6_dev_get(skb->dev);
 165
 166         __IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
 167
 168         SKB_DR_SET(reason, NOT_SPECIFIED);
 169         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
 170             !idev || unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
 171                 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 172                 if (idev && unlikely(READ_ONCE(idev->cnf.disable_ipv6)))
 173                         SKB_DR_SET(reason, IPV6DISABLED);
 174                 goto drop;
 175         }
 176
 177         memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
 178
 179         /*
 180          * Store incoming device index. When the packet will
 181          * be queued, we cannot refer to skb->dev anymore.
 182          *
 183          * BTW, when we send a packet for our own local address on a
 184          * non-loopback interface (e.g. ethX), it is being delivered
 185          * via the loopback interface (lo) here; skb->dev = loopback_dev.
 186          * It, however, should be considered as if it is being
 187          * arrived via the sending interface (ethX), because of the
 188          * nature of scoping architecture. --yoshfuji
 189          */
 190         IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
 191
 192         if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
 193                 goto err;
 194
 195         hdr = ipv6_hdr(skb);
 196
 197         if (hdr->version != 6) {
 198                 SKB_DR_SET(reason, UNHANDLED_PROTO);
 199                 goto err;
 200         }
 201
 202         __IP6_ADD_STATS(net, idev,
 203                         IPSTATS_MIB_NOECTPKTS +
 204                                 (ipv6_get_dsfield(hdr) & INET_ECN_MASK),
 205                         max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
 206         /*
 207          * RFC4291 2.5.3
 208          * The loopback address must not be used as the source address in IPv6
 209          * packets that are sent outside of a single node. [..]
 210          * A packet received on an interface with a destination address
 211          * of loopback must be dropped.
 212          */
 213         if ((ipv6_addr_loopback(&hdr->saddr) ||
 214              ipv6_addr_loopback(&hdr->daddr)) &&
 215             !(dev->flags & IFF_LOOPBACK) &&
 216             !netif_is_l3_master(dev))
 217                 goto err;
 218
 219         /* RFC4291 Errata ID: 3480
 220          * Interface-Local scope spans only a single interface on a
 221          * node and is useful only for loopback transmission of
 222          * multicast.  Packets with interface-local scope received
 223          * from another node must be discarded.
 224          */
 225         if (!(skb->pkt_type == PACKET_LOOPBACK ||
 226               dev->flags & IFF_LOOPBACK) &&
 227             ipv6_addr_is_multicast(&hdr->daddr) &&
 228             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
 229                 goto err;
 230
 231         /* If enabled, drop unicast packets that were encapsulated in link-layer
 232          * multicast or broadcast to protected against the so-called "hole-196"
 233          * attack in 802.11 wireless.
 234          */
 235         if (!ipv6_addr_is_multicast(&hdr->daddr) &&
 236             (skb->pkt_type == PACKET_BROADCAST ||
 237              skb->pkt_type == PACKET_MULTICAST) &&
 238             READ_ONCE(idev->cnf.drop_unicast_in_l2_multicast)) {
 239                 SKB_DR_SET(reason, UNICAST_IN_L2_MULTICAST);
 240                 goto err;
 241         }
 242
 243         /* RFC4291 2.7
 244          * Nodes must not originate a packet to a multicast address whose scope
 245          * field contains the reserved value 0; if such a packet is received, it
 246          * must be silently dropped.
 247          */
 248         if (ipv6_addr_is_multicast(&hdr->daddr) &&
 249             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
 250                 goto err;
 251
 252         /*
 253          * RFC4291 2.7
 254          * Multicast addresses must not be used as source addresses in IPv6
 255          * packets or appear in any Routing header.
 256          */
 257         if (ipv6_addr_is_multicast(&hdr->saddr))
 258                 goto err;
 259
 260         skb->transport_header = skb->network_header + sizeof(*hdr);
 261         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
 262
 263         pkt_len = ntohs(hdr->payload_len);
 264
 265         /* pkt_len may be zero if Jumbo payload option is present */
 266         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
 267                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
 268                         __IP6_INC_STATS(net,
 269                                         idev, IPSTATS_MIB_INTRUNCATEDPKTS);
 270                         SKB_DR_SET(reason, PKT_TOO_SMALL);
 271                         goto drop;
 272                 }
 273                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
 274                         goto err;
 275                 hdr = ipv6_hdr(skb);
 276         }
 277
 278         if (hdr->nexthdr == NEXTHDR_HOP) {
 279                 if (ipv6_parse_hopopts(skb) < 0) {
 280                         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 281                         rcu_read_unlock();
 282                         return NULL;
 283                 }
 284         }
 285
 286         rcu_read_unlock();
 287
 288         /* Must drop socket now because of tproxy. */
 289         if (!skb_sk_is_prefetched(skb))
 290                 skb_orphan(skb);
 291
 292         return skb;
 293 err:
 294         __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 295         SKB_DR_OR(reason, IP_INHDR);
 296 drop:
 297         rcu_read_unlock();
 298         kfree_skb_reason(skb, reason);
 299         return NULL;
 300 }
 301
 302 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 303 {
 304         struct net *net = dev_net(skb->dev);
 305
 306         skb = ip6_rcv_core(skb, dev, net);
 307         if (skb == NULL)
 308                 return NET_RX_DROP;
 309         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
 310                        net, NULL, skb, dev, NULL,
 311                        ip6_rcv_finish);
 312 }
 313
 314 static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
 315                             struct net *net)
 316 {
 317         NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
 318                      head, dev, NULL, ip6_rcv_finish);
 319         ip6_list_rcv_finish(net, NULL, head);
 320 }
 321
 322 /* Receive a list of IPv6 packets */
 323 void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
 324                    struct net_device *orig_dev)
 325 {
 326         struct net_device *curr_dev = NULL;
 327         struct net *curr_net = NULL;
 328         struct sk_buff *skb, *next;
 329         LIST_HEAD(sublist);
 330
 331         list_for_each_entry_safe(skb, next, head, list) {
 332                 struct net_device *dev = skb->dev;
 333                 struct net *net = dev_net(dev);
 334
 335                 skb_list_del_init(skb);
 336                 skb = ip6_rcv_core(skb, dev, net);
 337                 if (skb == NULL)
 338                         continue;
 339
 340                 if (curr_dev != dev || curr_net != net) {
 341                         /* dispatch old sublist */
 342                         if (!list_empty(&sublist))
 343                                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 344                         /* start new sublist */
 345                         INIT_LIST_HEAD(&sublist);
 346                         curr_dev = dev;
 347                         curr_net = net;
 348                 }
 349                 list_add_tail(&skb->list, &sublist);
 350         }
 351         /* dispatch final sublist */
 352         if (!list_empty(&sublist))
 353                 ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 354 }
 355
 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         SKB_DR(reason);
 368         bool raw;
 369
 370         /*
 371          *      Parse extension headers
 372          */
 373
 374 resubmit:
 375         idev = ip6_dst_idev(skb_dst(skb));
 376         nhoff = IP6CB(skb)->nhoff;
 377         if (!have_final) {
 378                 if (!pskb_pull(skb, skb_transport_offset(skb)))
 379                         goto discard;
 380                 nexthdr = skb_network_header(skb)[nhoff];
 381         }
 382
 383 resubmit_final:
 384         raw = raw6_local_deliver(skb, nexthdr);
 385         ipprot = rcu_dereference(inet6_protos[nexthdr]);
 386         if (ipprot) {
 387                 int ret;
 388
 389                 if (have_final) {
 390                         if (!(ipprot->flags & INET6_PROTO_FINAL)) {
 391                                 /* Once we've seen a final protocol don't
 392                                  * allow encapsulation on any non-final
 393                                  * ones. This allows foo in UDP encapsulation
 394                                  * to work.
 395                                  */
 396                                 goto discard;
 397                         }
 398                 } else if (ipprot->flags & INET6_PROTO_FINAL) {
 399                         const struct ipv6hdr *hdr;
 400                         int sdif = inet6_sdif(skb);
 401                         struct net_device *dev;
 402
 403                         /* Only do this once for first final protocol */
 404                         have_final = true;
 405
 406
 407                         skb_postpull_rcsum(skb, skb_network_header(skb),
 408                                            skb_network_header_len(skb));
 409                         hdr = ipv6_hdr(skb);
 410
 411                         /* skb->dev passed may be master dev for vrfs. */
 412                         if (sdif) {
 413                                 dev = dev_get_by_index_rcu(net, sdif);
 414                                 if (!dev)
 415                                         goto discard;
 416                         } else {
 417                                 dev = skb->dev;
 418                         }
 419
 420                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
 421                             !ipv6_chk_mcast_addr(dev, &hdr->daddr,
 422                                                  &hdr->saddr) &&
 423                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb))) {
 424                                 SKB_DR_SET(reason, IP_INADDRERRORS);
 425                                 goto discard;
 426                         }
 427                 }
 428                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY)) {
 429                         if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 430                                 SKB_DR_SET(reason, XFRM_POLICY);
 431                                 goto discard;
 432                         }
 433                         nf_reset_ct(skb);
 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         ip6_protocol_deliver_rcu(net, skb, 0, false);
 481
 482         return 0;
 483 }
 484
 485
 486 int ip6_input(struct sk_buff *skb)
 487 {
 488         int res;
 489
 490         rcu_read_lock();
 491         res = NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
 492                       dev_net_rcu(skb->dev), NULL, skb, skb->dev, NULL,
 493                       ip6_input_finish);
 494         rcu_read_unlock();
 495
 496         return res;
 497 }
 498 EXPORT_SYMBOL_GPL(ip6_input);
 499
 500 int ip6_mc_input(struct sk_buff *skb)
 501 {
 502         int sdif = inet6_sdif(skb);
 503         const struct ipv6hdr *hdr;
 504         struct net_device *dev;
 505         bool deliver;
 506
 507         __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
 508                          __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
 509                          skb->len);
 510
 511         /* skb->dev passed may be master dev for vrfs. */
 512         if (sdif) {
 513                 rcu_read_lock();
 514                 dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
 515                 if (!dev) {
 516                         rcu_read_unlock();
 517                         kfree_skb(skb);
 518                         return -ENODEV;
 519                 }
 520         } else {
 521                 dev = skb->dev;
 522         }
 523
 524         hdr = ipv6_hdr(skb);
 525         deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
 526         if (sdif)
 527                 rcu_read_unlock();
 528
 529 #ifdef CONFIG_IPV6_MROUTE
 530         /*
 531          *      IPv6 multicast router mode is now supported ;)
 532          */
 533         if (atomic_read(&dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding) &&
 534             !(ipv6_addr_type(&hdr->daddr) &
 535               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
 536             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
 537                 /*
 538                  * Okay, we try to forward - split and duplicate
 539                  * packets.
 540                  */
 541                 struct sk_buff *skb2;
 542                 struct inet6_skb_parm *opt = IP6CB(skb);
 543
 544                 /* Check for MLD */
 545                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
 546                         /* Check if this is a mld message */
 547                         u8 nexthdr = hdr->nexthdr;
 548                         __be16 frag_off;
 549                         int offset;
 550
 551                         /* Check if the value of Router Alert
 552                          * is for MLD (0x0000).
 553                          */
 554                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
 555                                 deliver = false;
 556
 557                                 if (!ipv6_ext_hdr(nexthdr)) {
 558                                         /* BUG */
 559                                         goto out;
 560                                 }
 561                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
 562                                                           &nexthdr, &frag_off);
 563                                 if (offset < 0)
 564                                         goto out;
 565
 566                                 if (ipv6_is_mld(skb, nexthdr, offset))
 567                                         deliver = true;
 568
 569                                 goto out;
 570                         }
 571                         /* unknown RA - process it normally */
 572                 }
 573
 574                 if (deliver)
 575                         skb2 = skb_clone(skb, GFP_ATOMIC);
 576                 else {
 577                         skb2 = skb;
 578                         skb = NULL;
 579                 }
 580
 581                 if (skb2) {
 582                         ip6_mr_input(skb2);
 583                 }
 584         }
 585 out:
 586 #endif
 587         if (likely(deliver))
 588                 ip6_input(skb);
 589         else {
 590                 /* discard */
 591                 kfree_skb(skb);
 592         }
 593
 594         return 0;
 595 }