net/ipv4/netfilter/nf_nat_sip.c

   1 /* SIP extension for NAT alteration.
   2  *
   3  * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
   4  * based on RR's ip_nat_ftp.c and other modules.
   5  * (C) 2007 United Security Providers
   6  * (C) 2007, 2008 Patrick McHardy <kaber@trash.net>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/ip.h>
  16 #include <net/ip.h>
  17 #include <linux/udp.h>
  18 #include <linux/tcp.h>
  19
  20 #include <net/netfilter/nf_nat.h>
  21 #include <net/netfilter/nf_nat_helper.h>
  22 #include <net/netfilter/nf_nat_rule.h>
  23 #include <net/netfilter/nf_conntrack_helper.h>
  24 #include <net/netfilter/nf_conntrack_expect.h>
  25 #include <linux/netfilter/nf_conntrack_sip.h>
  26
  27 MODULE_LICENSE("GPL");
  28 MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
  29 MODULE_DESCRIPTION("SIP NAT helper");
  30 MODULE_ALIAS("ip_nat_sip");
  31
  32
  33 static unsigned int mangle_packet(struct sk_buff *skb, unsigned int dataoff,
  34                                   const char **dptr, unsigned int *datalen,
  35                                   unsigned int matchoff, unsigned int matchlen,
  36                                   const char *buffer, unsigned int buflen)
  37 {
  38         enum ip_conntrack_info ctinfo;
  39         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  40         struct tcphdr *th;
  41         unsigned int baseoff;
  42
  43         if (nf_ct_protonum(ct) == IPPROTO_TCP) {
  44                 th = (struct tcphdr *)(skb->data + ip_hdrlen(skb));
  45                 baseoff = ip_hdrlen(skb) + th->doff * 4;
  46                 matchoff += dataoff - baseoff;
  47
  48                 if (!__nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
  49                                                 matchoff, matchlen,
  50                                                 buffer, buflen, false))
  51                         return 0;
  52         } else {
  53                 baseoff = ip_hdrlen(skb) + sizeof(struct udphdr);
  54                 matchoff += dataoff - baseoff;
  55
  56                 if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
  57                                               matchoff, matchlen,
  58                                               buffer, buflen))
  59                         return 0;
  60         }
  61
  62         /* Reload data pointer and adjust datalen value */
  63         *dptr = skb->data + dataoff;
  64         *datalen += buflen - matchlen;
  65         return 1;
  66 }
  67
  68 static int map_addr(struct sk_buff *skb, unsigned int dataoff,
  69                     const char **dptr, unsigned int *datalen,
  70                     unsigned int matchoff, unsigned int matchlen,
  71                     union nf_inet_addr *addr, __be16 port)
  72 {
  73         enum ip_conntrack_info ctinfo;
  74         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  75         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
  76         char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
  77         unsigned int buflen;
  78         __be32 newaddr;
  79         __be16 newport;
  80
  81         if (ct->tuplehash[dir].tuple.src.u3.ip == addr->ip &&
  82             ct->tuplehash[dir].tuple.src.u.udp.port == port) {
  83                 newaddr = ct->tuplehash[!dir].tuple.dst.u3.ip;
  84                 newport = ct->tuplehash[!dir].tuple.dst.u.udp.port;
  85         } else if (ct->tuplehash[dir].tuple.dst.u3.ip == addr->ip &&
  86                    ct->tuplehash[dir].tuple.dst.u.udp.port == port) {
  87                 newaddr = ct->tuplehash[!dir].tuple.src.u3.ip;
  88                 newport = ct->tuplehash[!dir].tuple.src.u.udp.port;
  89         } else
  90                 return 1;
  91
  92         if (newaddr == addr->ip && newport == port)
  93                 return 1;
  94
  95         buflen = sprintf(buffer, "%pI4:%u", &newaddr, ntohs(newport));
  96
  97         return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
  98                              buffer, buflen);
  99 }
 100
 101 static int map_sip_addr(struct sk_buff *skb, unsigned int dataoff,
 102                         const char **dptr, unsigned int *datalen,
 103                         enum sip_header_types type)
 104 {
 105         enum ip_conntrack_info ctinfo;
 106         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 107         unsigned int matchlen, matchoff;
 108         union nf_inet_addr addr;
 109         __be16 port;
 110
 111         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, type, NULL,
 112                                     &matchoff, &matchlen, &addr, &port) <= 0)
 113                 return 1;
 114         return map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
 115                         &addr, port);
 116 }
 117
 118 static unsigned int ip_nat_sip(struct sk_buff *skb, unsigned int dataoff,
 119                                const char **dptr, unsigned int *datalen)
 120 {
 121         enum ip_conntrack_info ctinfo;
 122         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 123         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 124         unsigned int coff, matchoff, matchlen;
 125         enum sip_header_types hdr;
 126         union nf_inet_addr addr;
 127         __be16 port;
 128         int request, in_header;
 129
 130         /* Basic rules: requests and responses. */
 131         if (strnicmp(*dptr, "SIP/2.0", strlen("SIP/2.0")) != 0) {
 132                 if (ct_sip_parse_request(ct, *dptr, *datalen,
 133                                          &matchoff, &matchlen,
 134                                          &addr, &port) > 0 &&
 135                     !map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
 136                               &addr, port))
 137                         return NF_DROP;
 138                 request = 1;
 139         } else
 140                 request = 0;
 141
 142         if (nf_ct_protonum(ct) == IPPROTO_TCP)
 143                 hdr = SIP_HDR_VIA_TCP;
 144         else
 145                 hdr = SIP_HDR_VIA_UDP;
 146
 147         /* Translate topmost Via header and parameters */
 148         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
 149                                     hdr, NULL, &matchoff, &matchlen,
 150                                     &addr, &port) > 0) {
 151                 unsigned int olen, matchend, poff, plen, buflen, n;
 152                 char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
 153
 154                 /* We're only interested in headers related to this
 155                  * connection */
 156                 if (request) {
 157                         if (addr.ip != ct->tuplehash[dir].tuple.src.u3.ip ||
 158                             port != ct->tuplehash[dir].tuple.src.u.udp.port)
 159                                 goto next;
 160                 } else {
 161                         if (addr.ip != ct->tuplehash[dir].tuple.dst.u3.ip ||
 162                             port != ct->tuplehash[dir].tuple.dst.u.udp.port)
 163                                 goto next;
 164                 }
 165
 166                 olen = *datalen;
 167                 if (!map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
 168                               &addr, port))
 169                         return NF_DROP;
 170
 171                 matchend = matchoff + matchlen + *datalen - olen;
 172
 173                 /* The maddr= parameter (RFC 2361) specifies where to send
 174                  * the reply. */
 175                 if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
 176                                                "maddr=", &poff, &plen,
 177                                                &addr) > 0 &&
 178                     addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
 179                     addr.ip != ct->tuplehash[!dir].tuple.dst.u3.ip) {
 180                         buflen = sprintf(buffer, "%pI4",
 181                                         &ct->tuplehash[!dir].tuple.dst.u3.ip);
 182                         if (!mangle_packet(skb, dataoff, dptr, datalen,
 183                                            poff, plen, buffer, buflen))
 184                                 return NF_DROP;
 185                 }
 186
 187                 /* The received= parameter (RFC 2361) contains the address
 188                  * from which the server received the request. */
 189                 if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
 190                                                "received=", &poff, &plen,
 191                                                &addr) > 0 &&
 192                     addr.ip == ct->tuplehash[dir].tuple.dst.u3.ip &&
 193                     addr.ip != ct->tuplehash[!dir].tuple.src.u3.ip) {
 194                         buflen = sprintf(buffer, "%pI4",
 195                                         &ct->tuplehash[!dir].tuple.src.u3.ip);
 196                         if (!mangle_packet(skb, dataoff, dptr, datalen,
 197                                            poff, plen, buffer, buflen))
 198                                 return NF_DROP;
 199                 }
 200
 201                 /* The rport= parameter (RFC 3581) contains the port number
 202                  * from which the server received the request. */
 203                 if (ct_sip_parse_numerical_param(ct, *dptr, matchend, *datalen,
 204                                                  "rport=", &poff, &plen,
 205                                                  &n) > 0 &&
 206                     htons(n) == ct->tuplehash[dir].tuple.dst.u.udp.port &&
 207                     htons(n) != ct->tuplehash[!dir].tuple.src.u.udp.port) {
 208                         __be16 p = ct->tuplehash[!dir].tuple.src.u.udp.port;
 209                         buflen = sprintf(buffer, "%u", ntohs(p));
 210                         if (!mangle_packet(skb, dataoff, dptr, datalen,
 211                                            poff, plen, buffer, buflen))
 212                                 return NF_DROP;
 213                 }
 214         }
 215
 216 next:
 217         /* Translate Contact headers */
 218         coff = 0;
 219         in_header = 0;
 220         while (ct_sip_parse_header_uri(ct, *dptr, &coff, *datalen,
 221                                        SIP_HDR_CONTACT, &in_header,
 222                                        &matchoff, &matchlen,
 223                                        &addr, &port) > 0) {
 224                 if (!map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
 225                               &addr, port))
 226                         return NF_DROP;
 227         }
 228
 229         if (!map_sip_addr(skb, dataoff, dptr, datalen, SIP_HDR_FROM) ||
 230             !map_sip_addr(skb, dataoff, dptr, datalen, SIP_HDR_TO))
 231                 return NF_DROP;
 232
 233         return NF_ACCEPT;
 234 }
 235
 236 static void ip_nat_sip_seq_adjust(struct sk_buff *skb, s16 off)
 237 {
 238         enum ip_conntrack_info ctinfo;
 239         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 240         const struct tcphdr *th;
 241
 242         if (nf_ct_protonum(ct) != IPPROTO_TCP || off == 0)
 243                 return;
 244
 245         th = (struct tcphdr *)(skb->data + ip_hdrlen(skb));
 246         nf_nat_set_seq_adjust(ct, ctinfo, th->seq, off);
 247 }
 248
 249 /* Handles expected signalling connections and media streams */
 250 static void ip_nat_sip_expected(struct nf_conn *ct,
 251                                 struct nf_conntrack_expect *exp)
 252 {
 253         struct nf_nat_range range;
 254
 255         /* This must be a fresh one. */
 256         BUG_ON(ct->status & IPS_NAT_DONE_MASK);
 257
 258         /* For DST manip, map port here to where it's expected. */
 259         range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
 260         range.min = range.max = exp->saved_proto;
 261         range.min_ip = range.max_ip = exp->saved_ip;
 262         nf_nat_setup_info(ct, &range, IP_NAT_MANIP_DST);
 263
 264         /* Change src to where master sends to, but only if the connection
 265          * actually came from the same source. */
 266         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip ==
 267             ct->master->tuplehash[exp->dir].tuple.src.u3.ip) {
 268                 range.flags = IP_NAT_RANGE_MAP_IPS;
 269                 range.min_ip = range.max_ip
 270                         = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
 271                 nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC);
 272         }
 273 }
 274
 275 static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int dataoff,
 276                                       const char **dptr, unsigned int *datalen,
 277                                       struct nf_conntrack_expect *exp,
 278                                       unsigned int matchoff,
 279                                       unsigned int matchlen)
 280 {
 281         enum ip_conntrack_info ctinfo;
 282         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 283         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 284         __be32 newip;
 285         u_int16_t port;
 286         char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
 287         unsigned buflen;
 288
 289         /* Connection will come from reply */
 290         if (ct->tuplehash[dir].tuple.src.u3.ip == ct->tuplehash[!dir].tuple.dst.u3.ip)
 291                 newip = exp->tuple.dst.u3.ip;
 292         else
 293                 newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 294
 295         /* If the signalling port matches the connection's source port in the
 296          * original direction, try to use the destination port in the opposite
 297          * direction. */
 298         if (exp->tuple.dst.u.udp.port ==
 299             ct->tuplehash[dir].tuple.src.u.udp.port)
 300                 port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port);
 301         else
 302                 port = ntohs(exp->tuple.dst.u.udp.port);
 303
 304         exp->saved_ip = exp->tuple.dst.u3.ip;
 305         exp->tuple.dst.u3.ip = newip;
 306         exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
 307         exp->dir = !dir;
 308         exp->expectfn = ip_nat_sip_expected;
 309
 310         for (; port != 0; port++) {
 311                 int ret;
 312
 313                 exp->tuple.dst.u.udp.port = htons(port);
 314                 ret = nf_ct_expect_related(exp);
 315                 if (ret == 0)
 316                         break;
 317                 else if (ret != -EBUSY) {
 318                         port = 0;
 319                         break;
 320                 }
 321         }
 322
 323         if (port == 0)
 324                 return NF_DROP;
 325
 326         if (exp->tuple.dst.u3.ip != exp->saved_ip ||
 327             exp->tuple.dst.u.udp.port != exp->saved_proto.udp.port) {
 328                 buflen = sprintf(buffer, "%pI4:%u", &newip, port);
 329                 if (!mangle_packet(skb, dataoff, dptr, datalen,
 330                                    matchoff, matchlen, buffer, buflen))
 331                         goto err;
 332         }
 333         return NF_ACCEPT;
 334
 335 err:
 336         nf_ct_unexpect_related(exp);
 337         return NF_DROP;
 338 }
 339
 340 static int mangle_content_len(struct sk_buff *skb, unsigned int dataoff,
 341                               const char **dptr, unsigned int *datalen)
 342 {
 343         enum ip_conntrack_info ctinfo;
 344         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 345         unsigned int matchoff, matchlen;
 346         char buffer[sizeof("65536")];
 347         int buflen, c_len;
 348
 349         /* Get actual SDP length */
 350         if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen,
 351                                   SDP_HDR_VERSION, SDP_HDR_UNSPEC,
 352                                   &matchoff, &matchlen) <= 0)
 353                 return 0;
 354         c_len = *datalen - matchoff + strlen("v=");
 355
 356         /* Now, update SDP length */
 357         if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CONTENT_LENGTH,
 358                               &matchoff, &matchlen) <= 0)
 359                 return 0;
 360
 361         buflen = sprintf(buffer, "%u", c_len);
 362         return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
 363                              buffer, buflen);
 364 }
 365
 366 static int mangle_sdp_packet(struct sk_buff *skb, unsigned int dataoff,
 367                              const char **dptr, unsigned int *datalen,
 368                              unsigned int sdpoff,
 369                              enum sdp_header_types type,
 370                              enum sdp_header_types term,
 371                              char *buffer, int buflen)
 372 {
 373         enum ip_conntrack_info ctinfo;
 374         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 375         unsigned int matchlen, matchoff;
 376
 377         if (ct_sip_get_sdp_header(ct, *dptr, sdpoff, *datalen, type, term,
 378                                   &matchoff, &matchlen) <= 0)
 379                 return -ENOENT;
 380         return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
 381                              buffer, buflen) ? 0 : -EINVAL;
 382 }
 383
 384 static unsigned int ip_nat_sdp_addr(struct sk_buff *skb, unsigned int dataoff,
 385                                     const char **dptr, unsigned int *datalen,
 386                                     unsigned int sdpoff,
 387                                     enum sdp_header_types type,
 388                                     enum sdp_header_types term,
 389                                     const union nf_inet_addr *addr)
 390 {
 391         char buffer[sizeof("nnn.nnn.nnn.nnn")];
 392         unsigned int buflen;
 393
 394         buflen = sprintf(buffer, "%pI4", &addr->ip);
 395         if (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff, type, term,
 396                               buffer, buflen))
 397                 return 0;
 398
 399         return mangle_content_len(skb, dataoff, dptr, datalen);
 400 }
 401
 402 static unsigned int ip_nat_sdp_port(struct sk_buff *skb, unsigned int dataoff,
 403                                     const char **dptr, unsigned int *datalen,
 404                                     unsigned int matchoff,
 405                                     unsigned int matchlen,
 406                                     u_int16_t port)
 407 {
 408         char buffer[sizeof("nnnnn")];
 409         unsigned int buflen;
 410
 411         buflen = sprintf(buffer, "%u", port);
 412         if (!mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
 413                            buffer, buflen))
 414                 return 0;
 415
 416         return mangle_content_len(skb, dataoff, dptr, datalen);
 417 }
 418
 419 static unsigned int ip_nat_sdp_session(struct sk_buff *skb, unsigned int dataoff,
 420                                        const char **dptr, unsigned int *datalen,
 421                                        unsigned int sdpoff,
 422                                        const union nf_inet_addr *addr)
 423 {
 424         char buffer[sizeof("nnn.nnn.nnn.nnn")];
 425         unsigned int buflen;
 426
 427         /* Mangle session description owner and contact addresses */
 428         buflen = sprintf(buffer, "%pI4", &addr->ip);
 429         if (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff,
 430                                SDP_HDR_OWNER_IP4, SDP_HDR_MEDIA,
 431                                buffer, buflen))
 432                 return 0;
 433
 434         switch (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff,
 435                                   SDP_HDR_CONNECTION_IP4, SDP_HDR_MEDIA,
 436                                   buffer, buflen)) {
 437         case 0:
 438         /*
 439          * RFC 2327:
 440          *
 441          * Session description
 442          *
 443          * c=* (connection information - not required if included in all media)
 444          */
 445         case -ENOENT:
 446                 break;
 447         default:
 448                 return 0;
 449         }
 450
 451         return mangle_content_len(skb, dataoff, dptr, datalen);
 452 }
 453
 454 /* So, this packet has hit the connection tracking matching code.
 455    Mangle it, and change the expectation to match the new version. */
 456 static unsigned int ip_nat_sdp_media(struct sk_buff *skb, unsigned int dataoff,
 457                                      const char **dptr, unsigned int *datalen,
 458                                      struct nf_conntrack_expect *rtp_exp,
 459                                      struct nf_conntrack_expect *rtcp_exp,
 460                                      unsigned int mediaoff,
 461                                      unsigned int medialen,
 462                                      union nf_inet_addr *rtp_addr)
 463 {
 464         enum ip_conntrack_info ctinfo;
 465         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 466         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 467         u_int16_t port;
 468
 469         /* Connection will come from reply */
 470         if (ct->tuplehash[dir].tuple.src.u3.ip ==
 471             ct->tuplehash[!dir].tuple.dst.u3.ip)
 472                 rtp_addr->ip = rtp_exp->tuple.dst.u3.ip;
 473         else
 474                 rtp_addr->ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 475
 476         rtp_exp->saved_ip = rtp_exp->tuple.dst.u3.ip;
 477         rtp_exp->tuple.dst.u3.ip = rtp_addr->ip;
 478         rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
 479         rtp_exp->dir = !dir;
 480         rtp_exp->expectfn = ip_nat_sip_expected;
 481
 482         rtcp_exp->saved_ip = rtcp_exp->tuple.dst.u3.ip;
 483         rtcp_exp->tuple.dst.u3.ip = rtp_addr->ip;
 484         rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
 485         rtcp_exp->dir = !dir;
 486         rtcp_exp->expectfn = ip_nat_sip_expected;
 487
 488         /* Try to get same pair of ports: if not, try to change them. */
 489         for (port = ntohs(rtp_exp->tuple.dst.u.udp.port);
 490              port != 0; port += 2) {
 491                 int ret;
 492
 493                 rtp_exp->tuple.dst.u.udp.port = htons(port);
 494                 ret = nf_ct_expect_related(rtp_exp);
 495                 if (ret == -EBUSY)
 496                         continue;
 497                 else if (ret < 0) {
 498                         port = 0;
 499                         break;
 500                 }
 501                 rtcp_exp->tuple.dst.u.udp.port = htons(port + 1);
 502                 ret = nf_ct_expect_related(rtcp_exp);
 503                 if (ret == 0)
 504                         break;
 505                 else if (ret == -EBUSY) {
 506                         nf_ct_unexpect_related(rtp_exp);
 507                         continue;
 508                 } else if (ret < 0) {
 509                         nf_ct_unexpect_related(rtp_exp);
 510                         port = 0;
 511                         break;
 512                 }
 513         }
 514
 515         if (port == 0)
 516                 goto err1;
 517
 518         /* Update media port. */
 519         if (rtp_exp->tuple.dst.u.udp.port != rtp_exp->saved_proto.udp.port &&
 520             !ip_nat_sdp_port(skb, dataoff, dptr, datalen,
 521                              mediaoff, medialen, port))
 522                 goto err2;
 523
 524         return NF_ACCEPT;
 525
 526 err2:
 527         nf_ct_unexpect_related(rtp_exp);
 528         nf_ct_unexpect_related(rtcp_exp);
 529 err1:
 530         return NF_DROP;
 531 }
 532
 533 static void __exit nf_nat_sip_fini(void)
 534 {
 535         RCU_INIT_POINTER(nf_nat_sip_hook, NULL);
 536         RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, NULL);
 537         RCU_INIT_POINTER(nf_nat_sip_expect_hook, NULL);
 538         RCU_INIT_POINTER(nf_nat_sdp_addr_hook, NULL);
 539         RCU_INIT_POINTER(nf_nat_sdp_port_hook, NULL);
 540         RCU_INIT_POINTER(nf_nat_sdp_session_hook, NULL);
 541         RCU_INIT_POINTER(nf_nat_sdp_media_hook, NULL);
 542         synchronize_rcu();
 543 }
 544
 545 static int __init nf_nat_sip_init(void)
 546 {
 547         BUG_ON(nf_nat_sip_hook != NULL);
 548         BUG_ON(nf_nat_sip_seq_adjust_hook != NULL);
 549         BUG_ON(nf_nat_sip_expect_hook != NULL);
 550         BUG_ON(nf_nat_sdp_addr_hook != NULL);
 551         BUG_ON(nf_nat_sdp_port_hook != NULL);
 552         BUG_ON(nf_nat_sdp_session_hook != NULL);
 553         BUG_ON(nf_nat_sdp_media_hook != NULL);
 554         RCU_INIT_POINTER(nf_nat_sip_hook, ip_nat_sip);
 555         RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, ip_nat_sip_seq_adjust);
 556         RCU_INIT_POINTER(nf_nat_sip_expect_hook, ip_nat_sip_expect);
 557         RCU_INIT_POINTER(nf_nat_sdp_addr_hook, ip_nat_sdp_addr);
 558         RCU_INIT_POINTER(nf_nat_sdp_port_hook, ip_nat_sdp_port);
 559         RCU_INIT_POINTER(nf_nat_sdp_session_hook, ip_nat_sdp_session);
 560         RCU_INIT_POINTER(nf_nat_sdp_media_hook, ip_nat_sdp_media);
 561         return 0;
 562 }
 563
 564 module_init(nf_nat_sip_init);
 565 module_exit(nf_nat_sip_fini);