net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c

   1 /*
   2  * Copyright (C)2004 USAGI/WIDE Project
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Author:
   9  *      Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
  10  */
  11
  12 #include <linux/types.h>
  13 #include <linux/ipv6.h>
  14 #include <linux/in6.h>
  15 #include <linux/netfilter.h>
  16 #include <linux/module.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/icmp.h>
  19 #include <net/ipv6.h>
  20 #include <net/inet_frag.h>
  21
  22 #include <linux/netfilter_bridge.h>
  23 #include <linux/netfilter_ipv6.h>
  24 #include <linux/netfilter_ipv6/ip6_tables.h>
  25 #include <net/netfilter/nf_conntrack.h>
  26 #include <net/netfilter/nf_conntrack_helper.h>
  27 #include <net/netfilter/nf_conntrack_l4proto.h>
  28 #include <net/netfilter/nf_conntrack_l3proto.h>
  29 #include <net/netfilter/nf_conntrack_core.h>
  30 #include <net/netfilter/nf_conntrack_zones.h>
  31 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
  32 #include <net/netfilter/nf_nat_helper.h>
  33 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  34 #include <net/netfilter/nf_log.h>
  35
  36 static bool ipv6_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
  37                               struct nf_conntrack_tuple *tuple)
  38 {
  39         const u_int32_t *ap;
  40         u_int32_t _addrs[8];
  41
  42         ap = skb_header_pointer(skb, nhoff + offsetof(struct ipv6hdr, saddr),
  43                                 sizeof(_addrs), _addrs);
  44         if (ap == NULL)
  45                 return false;
  46
  47         memcpy(tuple->src.u3.ip6, ap, sizeof(tuple->src.u3.ip6));
  48         memcpy(tuple->dst.u3.ip6, ap + 4, sizeof(tuple->dst.u3.ip6));
  49
  50         return true;
  51 }
  52
  53 static bool ipv6_invert_tuple(struct nf_conntrack_tuple *tuple,
  54                               const struct nf_conntrack_tuple *orig)
  55 {
  56         memcpy(tuple->src.u3.ip6, orig->dst.u3.ip6, sizeof(tuple->src.u3.ip6));
  57         memcpy(tuple->dst.u3.ip6, orig->src.u3.ip6, sizeof(tuple->dst.u3.ip6));
  58
  59         return true;
  60 }
  61
  62 static int ipv6_print_tuple(struct seq_file *s,
  63                             const struct nf_conntrack_tuple *tuple)
  64 {
  65         return seq_printf(s, "src=%pI6 dst=%pI6 ",
  66                           tuple->src.u3.ip6, tuple->dst.u3.ip6);
  67 }
  68
  69 static int ipv6_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
  70                             unsigned int *dataoff, u_int8_t *protonum)
  71 {
  72         unsigned int extoff = nhoff + sizeof(struct ipv6hdr);
  73         __be16 frag_off;
  74         int protoff;
  75         u8 nexthdr;
  76
  77         if (skb_copy_bits(skb, nhoff + offsetof(struct ipv6hdr, nexthdr),
  78                           &nexthdr, sizeof(nexthdr)) != 0) {
  79                 pr_debug("ip6_conntrack_core: can't get nexthdr\n");
  80                 return -NF_ACCEPT;
  81         }
  82         protoff = ipv6_skip_exthdr(skb, extoff, &nexthdr, &frag_off);
  83         /*
  84          * (protoff == skb->len) means the packet has not data, just
  85          * IPv6 and possibly extensions headers, but it is tracked anyway
  86          */
  87         if (protoff < 0 || (frag_off & htons(~0x7)) != 0) {
  88                 pr_debug("ip6_conntrack_core: can't find proto in pkt\n");
  89                 return -NF_ACCEPT;
  90         }
  91
  92         *dataoff = protoff;
  93         *protonum = nexthdr;
  94         return NF_ACCEPT;
  95 }
  96
  97 static unsigned int ipv6_helper(unsigned int hooknum,
  98                                 struct sk_buff *skb,
  99                                 const struct net_device *in,
 100                                 const struct net_device *out,
 101                                 int (*okfn)(struct sk_buff *))
 102 {
 103         struct nf_conn *ct;
 104         const struct nf_conn_help *help;
 105         const struct nf_conntrack_helper *helper;
 106         enum ip_conntrack_info ctinfo;
 107         __be16 frag_off;
 108         int protoff;
 109         u8 nexthdr;
 110
 111         /* This is where we call the helper: as the packet goes out. */
 112         ct = nf_ct_get(skb, &ctinfo);
 113         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
 114                 return NF_ACCEPT;
 115
 116         help = nfct_help(ct);
 117         if (!help)
 118                 return NF_ACCEPT;
 119         /* rcu_read_lock()ed by nf_hook_slow */
 120         helper = rcu_dereference(help->helper);
 121         if (!helper)
 122                 return NF_ACCEPT;
 123
 124         nexthdr = ipv6_hdr(skb)->nexthdr;
 125         protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
 126                                    &frag_off);
 127         if (protoff < 0 || (frag_off & htons(~0x7)) != 0) {
 128                 pr_debug("proto header not found\n");
 129                 return NF_ACCEPT;
 130         }
 131
 132         return helper->help(skb, protoff, ct, ctinfo);
 133 }
 134
 135 static unsigned int ipv6_confirm(unsigned int hooknum,
 136                                  struct sk_buff *skb,
 137                                  const struct net_device *in,
 138                                  const struct net_device *out,
 139                                  int (*okfn)(struct sk_buff *))
 140 {
 141         struct nf_conn *ct;
 142         enum ip_conntrack_info ctinfo;
 143         unsigned char pnum = ipv6_hdr(skb)->nexthdr;
 144         int protoff;
 145         __be16 frag_off;
 146
 147         ct = nf_ct_get(skb, &ctinfo);
 148         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
 149                 goto out;
 150
 151         protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &pnum,
 152                                    &frag_off);
 153         if (protoff < 0 || (frag_off & htons(~0x7)) != 0) {
 154                 pr_debug("proto header not found\n");
 155                 goto out;
 156         }
 157
 158         /* adjust seqs for loopback traffic only in outgoing direction */
 159         if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
 160             !nf_is_loopback_packet(skb)) {
 161                 typeof(nf_nat_seq_adjust_hook) seq_adjust;
 162
 163                 seq_adjust = rcu_dereference(nf_nat_seq_adjust_hook);
 164                 if (!seq_adjust ||
 165                     !seq_adjust(skb, ct, ctinfo, protoff)) {
 166                         NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop);
 167                         return NF_DROP;
 168                 }
 169         }
 170 out:
 171         /* We've seen it coming out the other side: confirm it */
 172         return nf_conntrack_confirm(skb);
 173 }
 174
 175 static unsigned int __ipv6_conntrack_in(struct net *net,
 176                                         unsigned int hooknum,
 177                                         struct sk_buff *skb,
 178                                         const struct net_device *in,
 179                                         const struct net_device *out,
 180                                         int (*okfn)(struct sk_buff *))
 181 {
 182         struct sk_buff *reasm = skb->nfct_reasm;
 183         const struct nf_conn_help *help;
 184         struct nf_conn *ct;
 185         enum ip_conntrack_info ctinfo;
 186
 187         /* This packet is fragmented and has reassembled packet. */
 188         if (reasm) {
 189                 /* Reassembled packet isn't parsed yet ? */
 190                 if (!reasm->nfct) {
 191                         unsigned int ret;
 192
 193                         ret = nf_conntrack_in(net, PF_INET6, hooknum, reasm);
 194                         if (ret != NF_ACCEPT)
 195                                 return ret;
 196                 }
 197
 198                 /* Conntrack helpers need the entire reassembled packet in the
 199                  * POST_ROUTING hook. In case of unconfirmed connections NAT
 200                  * might reassign a helper, so the entire packet is also
 201                  * required.
 202                  */
 203                 ct = nf_ct_get(reasm, &ctinfo);
 204                 if (ct != NULL && !nf_ct_is_untracked(ct)) {
 205                         help = nfct_help(ct);
 206                         if ((help && help->helper) || !nf_ct_is_confirmed(ct)) {
 207                                 nf_conntrack_get_reasm(skb);
 208                                 NF_HOOK_THRESH(NFPROTO_IPV6, hooknum, reasm,
 209                                                (struct net_device *)in,
 210                                                (struct net_device *)out,
 211                                                okfn, NF_IP6_PRI_CONNTRACK + 1);
 212                                 return NF_DROP_ERR(-ECANCELED);
 213                         }
 214                 }
 215
 216                 nf_conntrack_get(reasm->nfct);
 217                 skb->nfct = reasm->nfct;
 218                 skb->nfctinfo = reasm->nfctinfo;
 219                 return NF_ACCEPT;
 220         }
 221
 222         return nf_conntrack_in(net, PF_INET6, hooknum, skb);
 223 }
 224
 225 static unsigned int ipv6_conntrack_in(unsigned int hooknum,
 226                                       struct sk_buff *skb,
 227                                       const struct net_device *in,
 228                                       const struct net_device *out,
 229                                       int (*okfn)(struct sk_buff *))
 230 {
 231         return __ipv6_conntrack_in(dev_net(in), hooknum, skb, in, out, okfn);
 232 }
 233
 234 static unsigned int ipv6_conntrack_local(unsigned int hooknum,
 235                                          struct sk_buff *skb,
 236                                          const struct net_device *in,
 237                                          const struct net_device *out,
 238                                          int (*okfn)(struct sk_buff *))
 239 {
 240         /* root is playing with raw sockets. */
 241         if (skb->len < sizeof(struct ipv6hdr)) {
 242                 net_notice_ratelimited("ipv6_conntrack_local: packet too short\n");
 243                 return NF_ACCEPT;
 244         }
 245         return __ipv6_conntrack_in(dev_net(out), hooknum, skb, in, out, okfn);
 246 }
 247
 248 static struct nf_hook_ops ipv6_conntrack_ops[] __read_mostly = {
 249         {
 250                 .hook           = ipv6_conntrack_in,
 251                 .owner          = THIS_MODULE,
 252                 .pf             = NFPROTO_IPV6,
 253                 .hooknum        = NF_INET_PRE_ROUTING,
 254                 .priority       = NF_IP6_PRI_CONNTRACK,
 255         },
 256         {
 257                 .hook           = ipv6_conntrack_local,
 258                 .owner          = THIS_MODULE,
 259                 .pf             = NFPROTO_IPV6,
 260                 .hooknum        = NF_INET_LOCAL_OUT,
 261                 .priority       = NF_IP6_PRI_CONNTRACK,
 262         },
 263         {
 264                 .hook           = ipv6_helper,
 265                 .owner          = THIS_MODULE,
 266                 .pf             = NFPROTO_IPV6,
 267                 .hooknum        = NF_INET_POST_ROUTING,
 268                 .priority       = NF_IP6_PRI_CONNTRACK_HELPER,
 269         },
 270         {
 271                 .hook           = ipv6_confirm,
 272                 .owner          = THIS_MODULE,
 273                 .pf             = NFPROTO_IPV6,
 274                 .hooknum        = NF_INET_POST_ROUTING,
 275                 .priority       = NF_IP6_PRI_LAST,
 276         },
 277         {
 278                 .hook           = ipv6_helper,
 279                 .owner          = THIS_MODULE,
 280                 .pf             = NFPROTO_IPV6,
 281                 .hooknum        = NF_INET_LOCAL_IN,
 282                 .priority       = NF_IP6_PRI_CONNTRACK_HELPER,
 283         },
 284         {
 285                 .hook           = ipv6_confirm,
 286                 .owner          = THIS_MODULE,
 287                 .pf             = NFPROTO_IPV6,
 288                 .hooknum        = NF_INET_LOCAL_IN,
 289                 .priority       = NF_IP6_PRI_LAST-1,
 290         },
 291 };
 292
 293 static int
 294 ipv6_getorigdst(struct sock *sk, int optval, void __user *user, int *len)
 295 {
 296         const struct inet_sock *inet = inet_sk(sk);
 297         const struct ipv6_pinfo *inet6 = inet6_sk(sk);
 298         const struct nf_conntrack_tuple_hash *h;
 299         struct sockaddr_in6 sin6;
 300         struct nf_conntrack_tuple tuple = { .src.l3num = NFPROTO_IPV6 };
 301         struct nf_conn *ct;
 302
 303         tuple.src.u3.in6 = inet6->rcv_saddr;
 304         tuple.src.u.tcp.port = inet->inet_sport;
 305         tuple.dst.u3.in6 = inet6->daddr;
 306         tuple.dst.u.tcp.port = inet->inet_dport;
 307         tuple.dst.protonum = sk->sk_protocol;
 308
 309         if (sk->sk_protocol != IPPROTO_TCP && sk->sk_protocol != IPPROTO_SCTP)
 310                 return -ENOPROTOOPT;
 311
 312         if (*len < 0 || (unsigned int) *len < sizeof(sin6))
 313                 return -EINVAL;
 314
 315         h = nf_conntrack_find_get(sock_net(sk), NF_CT_DEFAULT_ZONE, &tuple);
 316         if (!h) {
 317                 pr_debug("IP6T_SO_ORIGINAL_DST: Can't find %pI6c/%u-%pI6c/%u.\n",
 318                          &tuple.src.u3.ip6, ntohs(tuple.src.u.tcp.port),
 319                          &tuple.dst.u3.ip6, ntohs(tuple.dst.u.tcp.port));
 320                 return -ENOENT;
 321         }
 322
 323         ct = nf_ct_tuplehash_to_ctrack(h);
 324
 325         sin6.sin6_family = AF_INET6;
 326         sin6.sin6_port = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u.tcp.port;
 327         sin6.sin6_flowinfo = inet6->flow_label & IPV6_FLOWINFO_MASK;
 328         memcpy(&sin6.sin6_addr,
 329                 &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.in6,
 330                                         sizeof(sin6.sin6_addr));
 331
 332         nf_ct_put(ct);
 333         sin6.sin6_scope_id = ipv6_iface_scope_id(&sin6.sin6_addr,
 334                                                  sk->sk_bound_dev_if);
 335         return copy_to_user(user, &sin6, sizeof(sin6)) ? -EFAULT : 0;
 336 }
 337
 338 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 339
 340 #include <linux/netfilter/nfnetlink.h>
 341 #include <linux/netfilter/nfnetlink_conntrack.h>
 342
 343 static int ipv6_tuple_to_nlattr(struct sk_buff *skb,
 344                                 const struct nf_conntrack_tuple *tuple)
 345 {
 346         if (nla_put(skb, CTA_IP_V6_SRC, sizeof(u_int32_t) * 4,
 347                     &tuple->src.u3.ip6) ||
 348             nla_put(skb, CTA_IP_V6_DST, sizeof(u_int32_t) * 4,
 349                     &tuple->dst.u3.ip6))
 350                 goto nla_put_failure;
 351         return 0;
 352
 353 nla_put_failure:
 354         return -1;
 355 }
 356
 357 static const struct nla_policy ipv6_nla_policy[CTA_IP_MAX+1] = {
 358         [CTA_IP_V6_SRC] = { .len = sizeof(u_int32_t)*4 },
 359         [CTA_IP_V6_DST] = { .len = sizeof(u_int32_t)*4 },
 360 };
 361
 362 static int ipv6_nlattr_to_tuple(struct nlattr *tb[],
 363                                 struct nf_conntrack_tuple *t)
 364 {
 365         if (!tb[CTA_IP_V6_SRC] || !tb[CTA_IP_V6_DST])
 366                 return -EINVAL;
 367
 368         memcpy(&t->src.u3.ip6, nla_data(tb[CTA_IP_V6_SRC]),
 369                sizeof(u_int32_t) * 4);
 370         memcpy(&t->dst.u3.ip6, nla_data(tb[CTA_IP_V6_DST]),
 371                sizeof(u_int32_t) * 4);
 372
 373         return 0;
 374 }
 375
 376 static int ipv6_nlattr_tuple_size(void)
 377 {
 378         return nla_policy_len(ipv6_nla_policy, CTA_IP_MAX + 1);
 379 }
 380 #endif
 381
 382 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv6 __read_mostly = {
 383         .l3proto                = PF_INET6,
 384         .name                   = "ipv6",
 385         .pkt_to_tuple           = ipv6_pkt_to_tuple,
 386         .invert_tuple           = ipv6_invert_tuple,
 387         .print_tuple            = ipv6_print_tuple,
 388         .get_l4proto            = ipv6_get_l4proto,
 389 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 390         .tuple_to_nlattr        = ipv6_tuple_to_nlattr,
 391         .nlattr_tuple_size      = ipv6_nlattr_tuple_size,
 392         .nlattr_to_tuple        = ipv6_nlattr_to_tuple,
 393         .nla_policy             = ipv6_nla_policy,
 394 #endif
 395         .me                     = THIS_MODULE,
 396 };
 397
 398 MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET6));
 399 MODULE_LICENSE("GPL");
 400 MODULE_AUTHOR("Yasuyuki KOZAKAI @USAGI <yasuyuki.kozakai@toshiba.co.jp>");
 401
 402 static struct nf_sockopt_ops so_getorigdst6 = {
 403         .pf             = NFPROTO_IPV6,
 404         .get_optmin     = IP6T_SO_ORIGINAL_DST,
 405         .get_optmax     = IP6T_SO_ORIGINAL_DST + 1,
 406         .get            = ipv6_getorigdst,
 407         .owner          = THIS_MODULE,
 408 };
 409
 410 static int ipv6_net_init(struct net *net)
 411 {
 412         int ret = 0;
 413
 414         ret = nf_ct_l4proto_pernet_register(net, &nf_conntrack_l4proto_tcp6);
 415         if (ret < 0) {
 416                 pr_err("nf_conntrack_tcp6: pernet registration failed\n");
 417                 goto out;
 418         }
 419         ret = nf_ct_l4proto_pernet_register(net, &nf_conntrack_l4proto_udp6);
 420         if (ret < 0) {
 421                 pr_err("nf_conntrack_udp6: pernet registration failed\n");
 422                 goto cleanup_tcp6;
 423         }
 424         ret = nf_ct_l4proto_pernet_register(net, &nf_conntrack_l4proto_icmpv6);
 425         if (ret < 0) {
 426                 pr_err("nf_conntrack_icmp6: pernet registration failed\n");
 427                 goto cleanup_udp6;
 428         }
 429         ret = nf_ct_l3proto_pernet_register(net, &nf_conntrack_l3proto_ipv6);
 430         if (ret < 0) {
 431                 pr_err("nf_conntrack_ipv6: pernet registration failed.\n");
 432                 goto cleanup_icmpv6;
 433         }
 434         return 0;
 435  cleanup_icmpv6:
 436         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_icmpv6);
 437  cleanup_udp6:
 438         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_udp6);
 439  cleanup_tcp6:
 440         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_tcp6);
 441  out:
 442         return ret;
 443 }
 444
 445 static void ipv6_net_exit(struct net *net)
 446 {
 447         nf_ct_l3proto_pernet_unregister(net, &nf_conntrack_l3proto_ipv6);
 448         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_icmpv6);
 449         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_udp6);
 450         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_tcp6);
 451 }
 452
 453 static struct pernet_operations ipv6_net_ops = {
 454         .init = ipv6_net_init,
 455         .exit = ipv6_net_exit,
 456 };
 457
 458 static int __init nf_conntrack_l3proto_ipv6_init(void)
 459 {
 460         int ret = 0;
 461
 462         need_conntrack();
 463         nf_defrag_ipv6_enable();
 464
 465         ret = nf_register_sockopt(&so_getorigdst6);
 466         if (ret < 0) {
 467                 pr_err("Unable to register netfilter socket option\n");
 468                 return ret;
 469         }
 470
 471         ret = register_pernet_subsys(&ipv6_net_ops);
 472         if (ret < 0)
 473                 goto cleanup_sockopt;
 474
 475         ret = nf_register_hooks(ipv6_conntrack_ops,
 476                                 ARRAY_SIZE(ipv6_conntrack_ops));
 477         if (ret < 0) {
 478                 pr_err("nf_conntrack_ipv6: can't register pre-routing defrag "
 479                        "hook.\n");
 480                 goto cleanup_pernet;
 481         }
 482
 483         ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_tcp6);
 484         if (ret < 0) {
 485                 pr_err("nf_conntrack_ipv6: can't register tcp6 proto.\n");
 486                 goto cleanup_hooks;
 487         }
 488
 489         ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_udp6);
 490         if (ret < 0) {
 491                 pr_err("nf_conntrack_ipv6: can't register udp6 proto.\n");
 492                 goto cleanup_tcp6;
 493         }
 494
 495         ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_icmpv6);
 496         if (ret < 0) {
 497                 pr_err("nf_conntrack_ipv6: can't register icmpv6 proto.\n");
 498                 goto cleanup_udp6;
 499         }
 500
 501         ret = nf_ct_l3proto_register(&nf_conntrack_l3proto_ipv6);
 502         if (ret < 0) {
 503                 pr_err("nf_conntrack_ipv6: can't register ipv6 proto.\n");
 504                 goto cleanup_icmpv6;
 505         }
 506         return ret;
 507
 508  cleanup_icmpv6:
 509         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_icmpv6);
 510  cleanup_udp6:
 511         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_udp6);
 512  cleanup_tcp6:
 513         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_tcp6);
 514  cleanup_hooks:
 515         nf_unregister_hooks(ipv6_conntrack_ops, ARRAY_SIZE(ipv6_conntrack_ops));
 516  cleanup_pernet:
 517         unregister_pernet_subsys(&ipv6_net_ops);
 518  cleanup_sockopt:
 519         nf_unregister_sockopt(&so_getorigdst6);
 520         return ret;
 521 }
 522
 523 static void __exit nf_conntrack_l3proto_ipv6_fini(void)
 524 {
 525         synchronize_net();
 526         nf_ct_l3proto_unregister(&nf_conntrack_l3proto_ipv6);
 527         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_tcp6);
 528         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_udp6);
 529         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_icmpv6);
 530         nf_unregister_hooks(ipv6_conntrack_ops, ARRAY_SIZE(ipv6_conntrack_ops));
 531         unregister_pernet_subsys(&ipv6_net_ops);
 532         nf_unregister_sockopt(&so_getorigdst6);
 533 }
 534
 535 module_init(nf_conntrack_l3proto_ipv6_init);
 536 module_exit(nf_conntrack_l3proto_ipv6_fini);