Pileus Git - ~andy/linux/blob - net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c

   1
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/types.h>
  11 #include <linux/ip.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/icmp.h>
  16 #include <linux/sysctl.h>
  17 #include <net/route.h>
  18 #include <net/ip.h>
  19
  20 #include <linux/netfilter_ipv4.h>
  21 #include <net/netfilter/nf_conntrack.h>
  22 #include <net/netfilter/nf_conntrack_helper.h>
  23 #include <net/netfilter/nf_conntrack_l4proto.h>
  24 #include <net/netfilter/nf_conntrack_l3proto.h>
  25 #include <net/netfilter/nf_conntrack_zones.h>
  26 #include <net/netfilter/nf_conntrack_core.h>
  27 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  28 #include <net/netfilter/nf_nat_helper.h>
  29 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  30 #include <net/netfilter/nf_log.h>
  31
  32 static bool ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
  33                               struct nf_conntrack_tuple *tuple)
  34 {
  35         const __be32 *ap;
  36         __be32 _addrs[2];
  37         ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
  38                                 sizeof(u_int32_t) * 2, _addrs);
  39         if (ap == NULL)
  40                 return false;
  41
  42         tuple->src.u3.ip = ap[0];
  43         tuple->dst.u3.ip = ap[1];
  44
  45         return true;
  46 }
  47
  48 static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
  49                               const struct nf_conntrack_tuple *orig)
  50 {
  51         tuple->src.u3.ip = orig->dst.u3.ip;
  52         tuple->dst.u3.ip = orig->src.u3.ip;
  53
  54         return true;
  55 }
  56
  57 static int ipv4_print_tuple(struct seq_file *s,
  58                             const struct nf_conntrack_tuple *tuple)
  59 {
  60         return seq_printf(s, "src=%pI4 dst=%pI4 ",
  61                           &tuple->src.u3.ip, &tuple->dst.u3.ip);
  62 }
  63
  64 static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
  65                             unsigned int *dataoff, u_int8_t *protonum)
  66 {
  67         const struct iphdr *iph;
  68         struct iphdr _iph;
  69
  70         iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  71         if (iph == NULL)
  72                 return -NF_ACCEPT;
  73
  74         /* Conntrack defragments packets, we might still see fragments
  75          * inside ICMP packets though. */
  76         if (iph->frag_off & htons(IP_OFFSET))
  77                 return -NF_ACCEPT;
  78
  79         *dataoff = nhoff + (iph->ihl << 2);
  80         *protonum = iph->protocol;
  81
  82         /* Check bogus IP headers */
  83         if (*dataoff > skb->len) {
  84                 pr_debug("nf_conntrack_ipv4: bogus IPv4 packet: "
  85                          "nhoff %u, ihl %u, skblen %u\n",
  86                          nhoff, iph->ihl << 2, skb->len);
  87                 return -NF_ACCEPT;
  88         }
  89
  90         return NF_ACCEPT;
  91 }
  92
  93 static unsigned int ipv4_helper(unsigned int hooknum,
  94                                 struct sk_buff *skb,
  95                                 const struct net_device *in,
  96                                 const struct net_device *out,
  97                                 int (*okfn)(struct sk_buff *))
  98 {
  99         struct nf_conn *ct;
 100         enum ip_conntrack_info ctinfo;
 101         const struct nf_conn_help *help;
 102         const struct nf_conntrack_helper *helper;
 103
 104         /* This is where we call the helper: as the packet goes out. */
 105         ct = nf_ct_get(skb, &ctinfo);
 106         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
 107                 return NF_ACCEPT;
 108
 109         help = nfct_help(ct);
 110         if (!help)
 111                 return NF_ACCEPT;
 112
 113         /* rcu_read_lock()ed by nf_hook_slow */
 114         helper = rcu_dereference(help->helper);
 115         if (!helper)
 116                 return NF_ACCEPT;
 117
 118         return helper->help(skb, skb_network_offset(skb) + ip_hdrlen(skb),
 119                             ct, ctinfo);
 120 }
 121
 122 static unsigned int ipv4_confirm(unsigned int hooknum,
 123                                  struct sk_buff *skb,
 124                                  const struct net_device *in,
 125                                  const struct net_device *out,
 126                                  int (*okfn)(struct sk_buff *))
 127 {
 128         struct nf_conn *ct;
 129         enum ip_conntrack_info ctinfo;
 130
 131         ct = nf_ct_get(skb, &ctinfo);
 132         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
 133                 goto out;
 134
 135         /* adjust seqs for loopback traffic only in outgoing direction */
 136         if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
 137             !nf_is_loopback_packet(skb)) {
 138                 typeof(nf_nat_seq_adjust_hook) seq_adjust;
 139
 140                 seq_adjust = rcu_dereference(nf_nat_seq_adjust_hook);
 141                 if (!seq_adjust ||
 142                     !seq_adjust(skb, ct, ctinfo, ip_hdrlen(skb))) {
 143                         NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop);
 144                         return NF_DROP;
 145                 }
 146         }
 147 out:
 148         /* We've seen it coming out the other side: confirm it */
 149         return nf_conntrack_confirm(skb);
 150 }
 151
 152 static unsigned int ipv4_conntrack_in(unsigned int hooknum,
 153                                       struct sk_buff *skb,
 154                                       const struct net_device *in,
 155                                       const struct net_device *out,
 156                                       int (*okfn)(struct sk_buff *))
 157 {
 158         return nf_conntrack_in(dev_net(in), PF_INET, hooknum, skb);
 159 }
 160
 161 static unsigned int ipv4_conntrack_local(unsigned int hooknum,
 162                                          struct sk_buff *skb,
 163                                          const struct net_device *in,
 164                                          const struct net_device *out,
 165                                          int (*okfn)(struct sk_buff *))
 166 {
 167         /* root is playing with raw sockets. */
 168         if (skb->len < sizeof(struct iphdr) ||
 169             ip_hdrlen(skb) < sizeof(struct iphdr))
 170                 return NF_ACCEPT;
 171         return nf_conntrack_in(dev_net(out), PF_INET, hooknum, skb);
 172 }
 173
 174 /* Connection tracking may drop packets, but never alters them, so
 175    make it the first hook. */
 176 static struct nf_hook_ops ipv4_conntrack_ops[] __read_mostly = {
 177         {
 178                 .hook           = ipv4_conntrack_in,
 179                 .owner          = THIS_MODULE,
 180                 .pf             = NFPROTO_IPV4,
 181                 .hooknum        = NF_INET_PRE_ROUTING,
 182                 .priority       = NF_IP_PRI_CONNTRACK,
 183         },
 184         {
 185                 .hook           = ipv4_conntrack_local,
 186                 .owner          = THIS_MODULE,
 187                 .pf             = NFPROTO_IPV4,
 188                 .hooknum        = NF_INET_LOCAL_OUT,
 189                 .priority       = NF_IP_PRI_CONNTRACK,
 190         },
 191         {
 192                 .hook           = ipv4_helper,
 193                 .owner          = THIS_MODULE,
 194                 .pf             = NFPROTO_IPV4,
 195                 .hooknum        = NF_INET_POST_ROUTING,
 196                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 197         },
 198         {
 199                 .hook           = ipv4_confirm,
 200                 .owner          = THIS_MODULE,
 201                 .pf             = NFPROTO_IPV4,
 202                 .hooknum        = NF_INET_POST_ROUTING,
 203                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 204         },
 205         {
 206                 .hook           = ipv4_helper,
 207                 .owner          = THIS_MODULE,
 208                 .pf             = NFPROTO_IPV4,
 209                 .hooknum        = NF_INET_LOCAL_IN,
 210                 .priority       = NF_IP_PRI_CONNTRACK_HELPER,
 211         },
 212         {
 213                 .hook           = ipv4_confirm,
 214                 .owner          = THIS_MODULE,
 215                 .pf             = NFPROTO_IPV4,
 216                 .hooknum        = NF_INET_LOCAL_IN,
 217                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 218         },
 219 };
 220
 221 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 222 static int log_invalid_proto_min = 0;
 223 static int log_invalid_proto_max = 255;
 224
 225 static ctl_table ip_ct_sysctl_table[] = {
 226         {
 227                 .procname       = "ip_conntrack_max",
 228                 .maxlen         = sizeof(int),
 229                 .mode           = 0644,
 230                 .proc_handler   = proc_dointvec,
 231         },
 232         {
 233                 .procname       = "ip_conntrack_count",
 234                 .maxlen         = sizeof(int),
 235                 .mode           = 0444,
 236                 .proc_handler   = proc_dointvec,
 237         },
 238         {
 239                 .procname       = "ip_conntrack_buckets",
 240                 .maxlen         = sizeof(unsigned int),
 241                 .mode           = 0444,
 242                 .proc_handler   = proc_dointvec,
 243         },
 244         {
 245                 .procname       = "ip_conntrack_checksum",
 246                 .maxlen         = sizeof(int),
 247                 .mode           = 0644,
 248                 .proc_handler   = proc_dointvec,
 249         },
 250         {
 251                 .procname       = "ip_conntrack_log_invalid",
 252                 .maxlen         = sizeof(unsigned int),
 253                 .mode           = 0644,
 254                 .proc_handler   = proc_dointvec_minmax,
 255                 .extra1         = &log_invalid_proto_min,
 256                 .extra2         = &log_invalid_proto_max,
 257         },
 258         { }
 259 };
 260 #endif /* CONFIG_SYSCTL && CONFIG_NF_CONNTRACK_PROC_COMPAT */
 261
 262 /* Fast function for those who don't want to parse /proc (and I don't
 263    blame them). */
 264 /* Reversing the socket's dst/src point of view gives us the reply
 265    mapping. */
 266 static int
 267 getorigdst(struct sock *sk, int optval, void __user *user, int *len)
 268 {
 269         const struct inet_sock *inet = inet_sk(sk);
 270         const struct nf_conntrack_tuple_hash *h;
 271         struct nf_conntrack_tuple tuple;
 272
 273         memset(&tuple, 0, sizeof(tuple));
 274         tuple.src.u3.ip = inet->inet_rcv_saddr;
 275         tuple.src.u.tcp.port = inet->inet_sport;
 276         tuple.dst.u3.ip = inet->inet_daddr;
 277         tuple.dst.u.tcp.port = inet->inet_dport;
 278         tuple.src.l3num = PF_INET;
 279         tuple.dst.protonum = sk->sk_protocol;
 280
 281         /* We only do TCP and SCTP at the moment: is there a better way? */
 282         if (sk->sk_protocol != IPPROTO_TCP && sk->sk_protocol != IPPROTO_SCTP) {
 283                 pr_debug("SO_ORIGINAL_DST: Not a TCP/SCTP socket\n");
 284                 return -ENOPROTOOPT;
 285         }
 286
 287         if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
 288                 pr_debug("SO_ORIGINAL_DST: len %d not %Zu\n",
 289                          *len, sizeof(struct sockaddr_in));
 290                 return -EINVAL;
 291         }
 292
 293         h = nf_conntrack_find_get(sock_net(sk), NF_CT_DEFAULT_ZONE, &tuple);
 294         if (h) {
 295                 struct sockaddr_in sin;
 296                 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
 297
 298                 sin.sin_family = AF_INET;
 299                 sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 300                         .tuple.dst.u.tcp.port;
 301                 sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
 302                         .tuple.dst.u3.ip;
 303                 memset(sin.sin_zero, 0, sizeof(sin.sin_zero));
 304
 305                 pr_debug("SO_ORIGINAL_DST: %pI4 %u\n",
 306                          &sin.sin_addr.s_addr, ntohs(sin.sin_port));
 307                 nf_ct_put(ct);
 308                 if (copy_to_user(user, &sin, sizeof(sin)) != 0)
 309                         return -EFAULT;
 310                 else
 311                         return 0;
 312         }
 313         pr_debug("SO_ORIGINAL_DST: Can't find %pI4/%u-%pI4/%u.\n",
 314                  &tuple.src.u3.ip, ntohs(tuple.src.u.tcp.port),
 315                  &tuple.dst.u3.ip, ntohs(tuple.dst.u.tcp.port));
 316         return -ENOENT;
 317 }
 318
 319 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 320
 321 #include <linux/netfilter/nfnetlink.h>
 322 #include <linux/netfilter/nfnetlink_conntrack.h>
 323
 324 static int ipv4_tuple_to_nlattr(struct sk_buff *skb,
 325                                 const struct nf_conntrack_tuple *tuple)
 326 {
 327         if (nla_put_be32(skb, CTA_IP_V4_SRC, tuple->src.u3.ip) ||
 328             nla_put_be32(skb, CTA_IP_V4_DST, tuple->dst.u3.ip))
 329                 goto nla_put_failure;
 330         return 0;
 331
 332 nla_put_failure:
 333         return -1;
 334 }
 335
 336 static const struct nla_policy ipv4_nla_policy[CTA_IP_MAX+1] = {
 337         [CTA_IP_V4_SRC] = { .type = NLA_U32 },
 338         [CTA_IP_V4_DST] = { .type = NLA_U32 },
 339 };
 340
 341 static int ipv4_nlattr_to_tuple(struct nlattr *tb[],
 342                                 struct nf_conntrack_tuple *t)
 343 {
 344         if (!tb[CTA_IP_V4_SRC] || !tb[CTA_IP_V4_DST])
 345                 return -EINVAL;
 346
 347         t->src.u3.ip = nla_get_be32(tb[CTA_IP_V4_SRC]);
 348         t->dst.u3.ip = nla_get_be32(tb[CTA_IP_V4_DST]);
 349
 350         return 0;
 351 }
 352
 353 static int ipv4_nlattr_tuple_size(void)
 354 {
 355         return nla_policy_len(ipv4_nla_policy, CTA_IP_MAX + 1);
 356 }
 357 #endif
 358
 359 static struct nf_sockopt_ops so_getorigdst = {
 360         .pf             = PF_INET,
 361         .get_optmin     = SO_ORIGINAL_DST,
 362         .get_optmax     = SO_ORIGINAL_DST+1,
 363         .get            = &getorigdst,
 364         .owner          = THIS_MODULE,
 365 };
 366
 367 static int ipv4_init_net(struct net *net)
 368 {
 369 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 370         struct nf_ip_net *in = &net->ct.nf_ct_proto;
 371         in->ctl_table = kmemdup(ip_ct_sysctl_table,
 372                                 sizeof(ip_ct_sysctl_table),
 373                                 GFP_KERNEL);
 374         if (!in->ctl_table)
 375                 return -ENOMEM;
 376
 377         in->ctl_table[0].data = &nf_conntrack_max;
 378         in->ctl_table[1].data = &net->ct.count;
 379         in->ctl_table[2].data = &net->ct.htable_size;
 380         in->ctl_table[3].data = &net->ct.sysctl_checksum;
 381         in->ctl_table[4].data = &net->ct.sysctl_log_invalid;
 382 #endif
 383         return 0;
 384 }
 385
 386 struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
 387         .l3proto         = PF_INET,
 388         .name            = "ipv4",
 389         .pkt_to_tuple    = ipv4_pkt_to_tuple,
 390         .invert_tuple    = ipv4_invert_tuple,
 391         .print_tuple     = ipv4_print_tuple,
 392         .get_l4proto     = ipv4_get_l4proto,
 393 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 394         .tuple_to_nlattr = ipv4_tuple_to_nlattr,
 395         .nlattr_tuple_size = ipv4_nlattr_tuple_size,
 396         .nlattr_to_tuple = ipv4_nlattr_to_tuple,
 397         .nla_policy      = ipv4_nla_policy,
 398 #endif
 399 #if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 400         .ctl_table_path  = "net/ipv4/netfilter",
 401 #endif
 402         .init_net        = ipv4_init_net,
 403         .me              = THIS_MODULE,
 404 };
 405
 406 module_param_call(hashsize, nf_conntrack_set_hashsize, param_get_uint,
 407                   &nf_conntrack_htable_size, 0600);
 408
 409 MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET));
 410 MODULE_ALIAS("ip_conntrack");
 411 MODULE_LICENSE("GPL");
 412
 413 static int ipv4_net_init(struct net *net)
 414 {
 415         int ret = 0;
 416
 417         ret = nf_ct_l4proto_pernet_register(net, &nf_conntrack_l4proto_tcp4);
 418         if (ret < 0) {
 419                 pr_err("nf_conntrack_tcp4: pernet registration failed\n");
 420                 goto out_tcp;
 421         }
 422         ret = nf_ct_l4proto_pernet_register(net, &nf_conntrack_l4proto_udp4);
 423         if (ret < 0) {
 424                 pr_err("nf_conntrack_udp4: pernet registration failed\n");
 425                 goto out_udp;
 426         }
 427         ret = nf_ct_l4proto_pernet_register(net, &nf_conntrack_l4proto_icmp);
 428         if (ret < 0) {
 429                 pr_err("nf_conntrack_icmp4: pernet registration failed\n");
 430                 goto out_icmp;
 431         }
 432         ret = nf_ct_l3proto_pernet_register(net, &nf_conntrack_l3proto_ipv4);
 433         if (ret < 0) {
 434                 pr_err("nf_conntrack_ipv4: pernet registration failed\n");
 435                 goto out_ipv4;
 436         }
 437         return 0;
 438 out_ipv4:
 439         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_icmp);
 440 out_icmp:
 441         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_udp4);
 442 out_udp:
 443         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_tcp4);
 444 out_tcp:
 445         return ret;
 446 }
 447
 448 static void ipv4_net_exit(struct net *net)
 449 {
 450         nf_ct_l3proto_pernet_unregister(net, &nf_conntrack_l3proto_ipv4);
 451         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_icmp);
 452         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_udp4);
 453         nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_tcp4);
 454 }
 455
 456 static struct pernet_operations ipv4_net_ops = {
 457         .init = ipv4_net_init,
 458         .exit = ipv4_net_exit,
 459 };
 460
 461 static int __init nf_conntrack_l3proto_ipv4_init(void)
 462 {
 463         int ret = 0;
 464
 465         need_conntrack();
 466         nf_defrag_ipv4_enable();
 467
 468         ret = nf_register_sockopt(&so_getorigdst);
 469         if (ret < 0) {
 470                 printk(KERN_ERR "Unable to register netfilter socket option\n");
 471                 return ret;
 472         }
 473
 474         ret = register_pernet_subsys(&ipv4_net_ops);
 475         if (ret < 0) {
 476                 pr_err("nf_conntrack_ipv4: can't register pernet ops\n");
 477                 goto cleanup_sockopt;
 478         }
 479
 480         ret = nf_register_hooks(ipv4_conntrack_ops,
 481                                 ARRAY_SIZE(ipv4_conntrack_ops));
 482         if (ret < 0) {
 483                 pr_err("nf_conntrack_ipv4: can't register hooks.\n");
 484                 goto cleanup_pernet;
 485         }
 486
 487         ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_tcp4);
 488         if (ret < 0) {
 489                 pr_err("nf_conntrack_ipv4: can't register tcp4 proto.\n");
 490                 goto cleanup_hooks;
 491         }
 492
 493         ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_udp4);
 494         if (ret < 0) {
 495                 pr_err("nf_conntrack_ipv4: can't register udp4 proto.\n");
 496                 goto cleanup_tcp4;
 497         }
 498
 499         ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_icmp);
 500         if (ret < 0) {
 501                 pr_err("nf_conntrack_ipv4: can't register icmpv4 proto.\n");
 502                 goto cleanup_udp4;
 503         }
 504
 505         ret = nf_ct_l3proto_register(&nf_conntrack_l3proto_ipv4);
 506         if (ret < 0) {
 507                 pr_err("nf_conntrack_ipv4: can't register ipv4 proto.\n");
 508                 goto cleanup_icmpv4;
 509         }
 510
 511 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 512         ret = nf_conntrack_ipv4_compat_init();
 513         if (ret < 0)
 514                 goto cleanup_proto;
 515 #endif
 516         return ret;
 517 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 518  cleanup_proto:
 519         nf_ct_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 520 #endif
 521  cleanup_icmpv4:
 522         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 523  cleanup_udp4:
 524         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 525  cleanup_tcp4:
 526         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 527  cleanup_hooks:
 528         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 529  cleanup_pernet:
 530         unregister_pernet_subsys(&ipv4_net_ops);
 531  cleanup_sockopt:
 532         nf_unregister_sockopt(&so_getorigdst);
 533         return ret;
 534 }
 535
 536 static void __exit nf_conntrack_l3proto_ipv4_fini(void)
 537 {
 538         synchronize_net();
 539 #if defined(CONFIG_PROC_FS) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
 540         nf_conntrack_ipv4_compat_fini();
 541 #endif
 542         nf_ct_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 543         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_icmp);
 544         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_udp4);
 545         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_tcp4);
 546         nf_unregister_hooks(ipv4_conntrack_ops, ARRAY_SIZE(ipv4_conntrack_ops));
 547         unregister_pernet_subsys(&ipv4_net_ops);
 548         nf_unregister_sockopt(&so_getorigdst);
 549 }
 550
 551 module_init(nf_conntrack_l3proto_ipv4_init);
 552 module_exit(nf_conntrack_l3proto_ipv4_fini);
 553
 554 void need_ipv4_conntrack(void)
 555 {
 556         return;
 557 }
 558 EXPORT_SYMBOL_GPL(need_ipv4_conntrack);