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_conntrack_helper.h>
  23 #include <net/netfilter/nf_conntrack_expect.h>
  24 #include <linux/netfilter/nf_conntrack_sip.h>
  25
  26 MODULE_LICENSE("GPL");
  27 MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
  28 MODULE_DESCRIPTION("SIP NAT helper");
  29 MODULE_ALIAS("ip_nat_sip");
  30
  31
  32 static unsigned int mangle_packet(struct sk_buff *skb, unsigned int protoff,
  33                                   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                                                 protoff, 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                                               protoff, 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 protoff,
  69                     unsigned int dataoff,
  70                     const char **dptr, unsigned int *datalen,
  71                     unsigned int matchoff, unsigned int matchlen,
  72                     union nf_inet_addr *addr, __be16 port)
  73 {
  74         enum ip_conntrack_info ctinfo;
  75         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  76         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
  77         char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
  78         unsigned int buflen;
  79         __be32 newaddr;
  80         __be16 newport;
  81
  82         if (ct->tuplehash[dir].tuple.src.u3.ip == addr->ip &&
  83             ct->tuplehash[dir].tuple.src.u.udp.port == port) {
  84                 newaddr = ct->tuplehash[!dir].tuple.dst.u3.ip;
  85                 newport = ct->tuplehash[!dir].tuple.dst.u.udp.port;
  86         } else if (ct->tuplehash[dir].tuple.dst.u3.ip == addr->ip &&
  87                    ct->tuplehash[dir].tuple.dst.u.udp.port == port) {
  88                 newaddr = ct->tuplehash[!dir].tuple.src.u3.ip;
  89                 newport = ct->tuplehash[!dir].tuple.src.u.udp.port;
  90         } else
  91                 return 1;
  92
  93         if (newaddr == addr->ip && newport == port)
  94                 return 1;
  95
  96         buflen = sprintf(buffer, "%pI4:%u", &newaddr, ntohs(newport));
  97
  98         return mangle_packet(skb, protoff, dataoff, dptr, datalen,
  99                              matchoff, matchlen, buffer, buflen);
 100 }
 101
 102 static int map_sip_addr(struct sk_buff *skb, unsigned int protoff,
 103                         unsigned int dataoff,
 104                         const char **dptr, unsigned int *datalen,
 105                         enum sip_header_types type)
 106 {
 107         enum ip_conntrack_info ctinfo;
 108         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 109         unsigned int matchlen, matchoff;
 110         union nf_inet_addr addr;
 111         __be16 port;
 112
 113         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, type, NULL,
 114                                     &matchoff, &matchlen, &addr, &port) <= 0)
 115                 return 1;
 116         return map_addr(skb, protoff, dataoff, dptr, datalen,
 117                         matchoff, matchlen, &addr, port);
 118 }
 119
 120 static unsigned int ip_nat_sip(struct sk_buff *skb, unsigned int protoff,
 121                                unsigned int dataoff,
 122                                const char **dptr, unsigned int *datalen)
 123 {
 124         enum ip_conntrack_info ctinfo;
 125         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 126         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 127         unsigned int coff, matchoff, matchlen;
 128         enum sip_header_types hdr;
 129         union nf_inet_addr addr;
 130         __be16 port;
 131         int request, in_header;
 132
 133         /* Basic rules: requests and responses. */
 134         if (strnicmp(*dptr, "SIP/2.0", strlen("SIP/2.0")) != 0) {
 135                 if (ct_sip_parse_request(ct, *dptr, *datalen,
 136                                          &matchoff, &matchlen,
 137                                          &addr, &port) > 0 &&
 138                     !map_addr(skb, protoff, dataoff, dptr, datalen,
 139                               matchoff, matchlen, &addr, port))
 140                         return NF_DROP;
 141                 request = 1;
 142         } else
 143                 request = 0;
 144
 145         if (nf_ct_protonum(ct) == IPPROTO_TCP)
 146                 hdr = SIP_HDR_VIA_TCP;
 147         else
 148                 hdr = SIP_HDR_VIA_UDP;
 149
 150         /* Translate topmost Via header and parameters */
 151         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
 152                                     hdr, NULL, &matchoff, &matchlen,
 153                                     &addr, &port) > 0) {
 154                 unsigned int olen, matchend, poff, plen, buflen, n;
 155                 char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
 156
 157                 /* We're only interested in headers related to this
 158                  * connection */
 159                 if (request) {
 160                         if (addr.ip != ct->tuplehash[dir].tuple.src.u3.ip ||
 161                             port != ct->tuplehash[dir].tuple.src.u.udp.port)
 162                                 goto next;
 163                 } else {
 164                         if (addr.ip != ct->tuplehash[dir].tuple.dst.u3.ip ||
 165                             port != ct->tuplehash[dir].tuple.dst.u.udp.port)
 166                                 goto next;
 167                 }
 168
 169                 olen = *datalen;
 170                 if (!map_addr(skb, protoff, dataoff, dptr, datalen,
 171                               matchoff, matchlen, &addr, port))
 172                         return NF_DROP;
 173
 174                 matchend = matchoff + matchlen + *datalen - olen;
 175
 176                 /* The maddr= parameter (RFC 2361) specifies where to send
 177                  * the reply. */
 178                 if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
 179                                                "maddr=", &poff, &plen,
 180                                                &addr, true) > 0 &&
 181                     addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
 182                     addr.ip != ct->tuplehash[!dir].tuple.dst.u3.ip) {
 183                         buflen = sprintf(buffer, "%pI4",
 184                                         &ct->tuplehash[!dir].tuple.dst.u3.ip);
 185                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 186                                            poff, plen, buffer, buflen))
 187                                 return NF_DROP;
 188                 }
 189
 190                 /* The received= parameter (RFC 2361) contains the address
 191                  * from which the server received the request. */
 192                 if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
 193                                                "received=", &poff, &plen,
 194                                                &addr, false) > 0 &&
 195                     addr.ip == ct->tuplehash[dir].tuple.dst.u3.ip &&
 196                     addr.ip != ct->tuplehash[!dir].tuple.src.u3.ip) {
 197                         buflen = sprintf(buffer, "%pI4",
 198                                         &ct->tuplehash[!dir].tuple.src.u3.ip);
 199                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 200                                            poff, plen, buffer, buflen))
 201                                 return NF_DROP;
 202                 }
 203
 204                 /* The rport= parameter (RFC 3581) contains the port number
 205                  * from which the server received the request. */
 206                 if (ct_sip_parse_numerical_param(ct, *dptr, matchend, *datalen,
 207                                                  "rport=", &poff, &plen,
 208                                                  &n) > 0 &&
 209                     htons(n) == ct->tuplehash[dir].tuple.dst.u.udp.port &&
 210                     htons(n) != ct->tuplehash[!dir].tuple.src.u.udp.port) {
 211                         __be16 p = ct->tuplehash[!dir].tuple.src.u.udp.port;
 212                         buflen = sprintf(buffer, "%u", ntohs(p));
 213                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 214                                            poff, plen, buffer, buflen))
 215                                 return NF_DROP;
 216                 }
 217         }
 218
 219 next:
 220         /* Translate Contact headers */
 221         coff = 0;
 222         in_header = 0;
 223         while (ct_sip_parse_header_uri(ct, *dptr, &coff, *datalen,
 224                                        SIP_HDR_CONTACT, &in_header,
 225                                        &matchoff, &matchlen,
 226                                        &addr, &port) > 0) {
 227                 if (!map_addr(skb, protoff, dataoff, dptr, datalen,
 228                               matchoff, matchlen,
 229                               &addr, port))
 230                         return NF_DROP;
 231         }
 232
 233         if (!map_sip_addr(skb, protoff, dataoff, dptr, datalen, SIP_HDR_FROM) ||
 234             !map_sip_addr(skb, protoff, dataoff, dptr, datalen, SIP_HDR_TO))
 235                 return NF_DROP;
 236
 237         return NF_ACCEPT;
 238 }
 239
 240 static void ip_nat_sip_seq_adjust(struct sk_buff *skb, s16 off)
 241 {
 242         enum ip_conntrack_info ctinfo;
 243         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 244         const struct tcphdr *th;
 245
 246         if (nf_ct_protonum(ct) != IPPROTO_TCP || off == 0)
 247                 return;
 248
 249         th = (struct tcphdr *)(skb->data + ip_hdrlen(skb));
 250         nf_nat_set_seq_adjust(ct, ctinfo, th->seq, off);
 251 }
 252
 253 /* Handles expected signalling connections and media streams */
 254 static void ip_nat_sip_expected(struct nf_conn *ct,
 255                                 struct nf_conntrack_expect *exp)
 256 {
 257         struct nf_nat_range range;
 258
 259         /* This must be a fresh one. */
 260         BUG_ON(ct->status & IPS_NAT_DONE_MASK);
 261
 262         /* For DST manip, map port here to where it's expected. */
 263         range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
 264         range.min_proto = range.max_proto = exp->saved_proto;
 265         range.min_addr = range.max_addr = exp->saved_addr;
 266         nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
 267
 268         /* Change src to where master sends to, but only if the connection
 269          * actually came from the same source. */
 270         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip ==
 271             ct->master->tuplehash[exp->dir].tuple.src.u3.ip) {
 272                 range.flags = NF_NAT_RANGE_MAP_IPS;
 273                 range.min_addr = range.max_addr
 274                         = ct->master->tuplehash[!exp->dir].tuple.dst.u3;
 275                 nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
 276         }
 277 }
 278
 279 static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int protoff,
 280                                       unsigned int dataoff,
 281                                       const char **dptr, unsigned int *datalen,
 282                                       struct nf_conntrack_expect *exp,
 283                                       unsigned int matchoff,
 284                                       unsigned int matchlen)
 285 {
 286         enum ip_conntrack_info ctinfo;
 287         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 288         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 289         __be32 newip;
 290         u_int16_t port;
 291         char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
 292         unsigned int buflen;
 293
 294         /* Connection will come from reply */
 295         if (ct->tuplehash[dir].tuple.src.u3.ip == ct->tuplehash[!dir].tuple.dst.u3.ip)
 296                 newip = exp->tuple.dst.u3.ip;
 297         else
 298                 newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 299
 300         /* If the signalling port matches the connection's source port in the
 301          * original direction, try to use the destination port in the opposite
 302          * direction. */
 303         if (exp->tuple.dst.u.udp.port ==
 304             ct->tuplehash[dir].tuple.src.u.udp.port)
 305                 port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port);
 306         else
 307                 port = ntohs(exp->tuple.dst.u.udp.port);
 308
 309         exp->saved_addr = exp->tuple.dst.u3;
 310         exp->tuple.dst.u3.ip = newip;
 311         exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
 312         exp->dir = !dir;
 313         exp->expectfn = ip_nat_sip_expected;
 314
 315         for (; port != 0; port++) {
 316                 int ret;
 317
 318                 exp->tuple.dst.u.udp.port = htons(port);
 319                 ret = nf_ct_expect_related(exp);
 320                 if (ret == 0)
 321                         break;
 322                 else if (ret != -EBUSY) {
 323                         port = 0;
 324                         break;
 325                 }
 326         }
 327
 328         if (port == 0)
 329                 return NF_DROP;
 330
 331         if (exp->tuple.dst.u3.ip != exp->saved_addr.ip ||
 332             exp->tuple.dst.u.udp.port != exp->saved_proto.udp.port) {
 333                 buflen = sprintf(buffer, "%pI4:%u", &newip, port);
 334                 if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 335                                    matchoff, matchlen, buffer, buflen))
 336                         goto err;
 337         }
 338         return NF_ACCEPT;
 339
 340 err:
 341         nf_ct_unexpect_related(exp);
 342         return NF_DROP;
 343 }
 344
 345 static int mangle_content_len(struct sk_buff *skb, unsigned int protoff,
 346                               unsigned int dataoff,
 347                               const char **dptr, unsigned int *datalen)
 348 {
 349         enum ip_conntrack_info ctinfo;
 350         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 351         unsigned int matchoff, matchlen;
 352         char buffer[sizeof("65536")];
 353         int buflen, c_len;
 354
 355         /* Get actual SDP length */
 356         if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen,
 357                                   SDP_HDR_VERSION, SDP_HDR_UNSPEC,
 358                                   &matchoff, &matchlen) <= 0)
 359                 return 0;
 360         c_len = *datalen - matchoff + strlen("v=");
 361
 362         /* Now, update SDP length */
 363         if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CONTENT_LENGTH,
 364                               &matchoff, &matchlen) <= 0)
 365                 return 0;
 366
 367         buflen = sprintf(buffer, "%u", c_len);
 368         return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 369                              matchoff, matchlen, buffer, buflen);
 370 }
 371
 372 static int mangle_sdp_packet(struct sk_buff *skb, unsigned int protoff,
 373                              unsigned int dataoff,
 374                              const char **dptr, unsigned int *datalen,
 375                              unsigned int sdpoff,
 376                              enum sdp_header_types type,
 377                              enum sdp_header_types term,
 378                              char *buffer, int buflen)
 379 {
 380         enum ip_conntrack_info ctinfo;
 381         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 382         unsigned int matchlen, matchoff;
 383
 384         if (ct_sip_get_sdp_header(ct, *dptr, sdpoff, *datalen, type, term,
 385                                   &matchoff, &matchlen) <= 0)
 386                 return -ENOENT;
 387         return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 388                              matchoff, matchlen, buffer, buflen) ? 0 : -EINVAL;
 389 }
 390
 391 static unsigned int ip_nat_sdp_addr(struct sk_buff *skb, unsigned int protoff,
 392                                     unsigned int dataoff,
 393                                     const char **dptr, unsigned int *datalen,
 394                                     unsigned int sdpoff,
 395                                     enum sdp_header_types type,
 396                                     enum sdp_header_types term,
 397                                     const union nf_inet_addr *addr)
 398 {
 399         char buffer[sizeof("nnn.nnn.nnn.nnn")];
 400         unsigned int buflen;
 401
 402         buflen = sprintf(buffer, "%pI4", &addr->ip);
 403         if (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen,
 404                               sdpoff, type, term, buffer, buflen))
 405                 return 0;
 406
 407         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 408 }
 409
 410 static unsigned int ip_nat_sdp_port(struct sk_buff *skb, unsigned int protoff,
 411                                     unsigned int dataoff,
 412                                     const char **dptr, unsigned int *datalen,
 413                                     unsigned int matchoff,
 414                                     unsigned int matchlen,
 415                                     u_int16_t port)
 416 {
 417         char buffer[sizeof("nnnnn")];
 418         unsigned int buflen;
 419
 420         buflen = sprintf(buffer, "%u", port);
 421         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 422                            matchoff, matchlen, buffer, buflen))
 423                 return 0;
 424
 425         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 426 }
 427
 428 static unsigned int ip_nat_sdp_session(struct sk_buff *skb, unsigned int protoff,
 429                                        unsigned int dataoff,
 430                                        const char **dptr, unsigned int *datalen,
 431                                        unsigned int sdpoff,
 432                                        const union nf_inet_addr *addr)
 433 {
 434         char buffer[sizeof("nnn.nnn.nnn.nnn")];
 435         unsigned int buflen;
 436
 437         /* Mangle session description owner and contact addresses */
 438         buflen = sprintf(buffer, "%pI4", &addr->ip);
 439         if (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen, sdpoff,
 440                                SDP_HDR_OWNER_IP4, SDP_HDR_MEDIA,
 441                                buffer, buflen))
 442                 return 0;
 443
 444         switch (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen, sdpoff,
 445                                   SDP_HDR_CONNECTION_IP4, SDP_HDR_MEDIA,
 446                                   buffer, buflen)) {
 447         case 0:
 448         /*
 449          * RFC 2327:
 450          *
 451          * Session description
 452          *
 453          * c=* (connection information - not required if included in all media)
 454          */
 455         case -ENOENT:
 456                 break;
 457         default:
 458                 return 0;
 459         }
 460
 461         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 462 }
 463
 464 /* So, this packet has hit the connection tracking matching code.
 465    Mangle it, and change the expectation to match the new version. */
 466 static unsigned int ip_nat_sdp_media(struct sk_buff *skb, unsigned int protoff,
 467                                      unsigned int dataoff,
 468                                      const char **dptr, unsigned int *datalen,
 469                                      struct nf_conntrack_expect *rtp_exp,
 470                                      struct nf_conntrack_expect *rtcp_exp,
 471                                      unsigned int mediaoff,
 472                                      unsigned int medialen,
 473                                      union nf_inet_addr *rtp_addr)
 474 {
 475         enum ip_conntrack_info ctinfo;
 476         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 477         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 478         u_int16_t port;
 479
 480         /* Connection will come from reply */
 481         if (ct->tuplehash[dir].tuple.src.u3.ip ==
 482             ct->tuplehash[!dir].tuple.dst.u3.ip)
 483                 rtp_addr->ip = rtp_exp->tuple.dst.u3.ip;
 484         else
 485                 rtp_addr->ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 486
 487         rtp_exp->saved_addr = rtp_exp->tuple.dst.u3;
 488         rtp_exp->tuple.dst.u3.ip = rtp_addr->ip;
 489         rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
 490         rtp_exp->dir = !dir;
 491         rtp_exp->expectfn = ip_nat_sip_expected;
 492
 493         rtcp_exp->saved_addr = rtcp_exp->tuple.dst.u3;
 494         rtcp_exp->tuple.dst.u3.ip = rtp_addr->ip;
 495         rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
 496         rtcp_exp->dir = !dir;
 497         rtcp_exp->expectfn = ip_nat_sip_expected;
 498
 499         /* Try to get same pair of ports: if not, try to change them. */
 500         for (port = ntohs(rtp_exp->tuple.dst.u.udp.port);
 501              port != 0; port += 2) {
 502                 int ret;
 503
 504                 rtp_exp->tuple.dst.u.udp.port = htons(port);
 505                 ret = nf_ct_expect_related(rtp_exp);
 506                 if (ret == -EBUSY)
 507                         continue;
 508                 else if (ret < 0) {
 509                         port = 0;
 510                         break;
 511                 }
 512                 rtcp_exp->tuple.dst.u.udp.port = htons(port + 1);
 513                 ret = nf_ct_expect_related(rtcp_exp);
 514                 if (ret == 0)
 515                         break;
 516                 else if (ret != -EBUSY) {
 517                         nf_ct_unexpect_related(rtp_exp);
 518                         port = 0;
 519                         break;
 520                 }
 521         }
 522
 523         if (port == 0)
 524                 goto err1;
 525
 526         /* Update media port. */
 527         if (rtp_exp->tuple.dst.u.udp.port != rtp_exp->saved_proto.udp.port &&
 528             !ip_nat_sdp_port(skb, protoff, dataoff, dptr, datalen,
 529                              mediaoff, medialen, port))
 530                 goto err2;
 531
 532         return NF_ACCEPT;
 533
 534 err2:
 535         nf_ct_unexpect_related(rtp_exp);
 536         nf_ct_unexpect_related(rtcp_exp);
 537 err1:
 538         return NF_DROP;
 539 }
 540
 541 static struct nf_ct_helper_expectfn sip_nat = {
 542         .name           = "sip",
 543         .expectfn       = ip_nat_sip_expected,
 544 };
 545
 546 static void __exit nf_nat_sip_fini(void)
 547 {
 548         RCU_INIT_POINTER(nf_nat_sip_hook, NULL);
 549         RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, NULL);
 550         RCU_INIT_POINTER(nf_nat_sip_expect_hook, NULL);
 551         RCU_INIT_POINTER(nf_nat_sdp_addr_hook, NULL);
 552         RCU_INIT_POINTER(nf_nat_sdp_port_hook, NULL);
 553         RCU_INIT_POINTER(nf_nat_sdp_session_hook, NULL);
 554         RCU_INIT_POINTER(nf_nat_sdp_media_hook, NULL);
 555         nf_ct_helper_expectfn_unregister(&sip_nat);
 556         synchronize_rcu();
 557 }
 558
 559 static int __init nf_nat_sip_init(void)
 560 {
 561         BUG_ON(nf_nat_sip_hook != NULL);
 562         BUG_ON(nf_nat_sip_seq_adjust_hook != NULL);
 563         BUG_ON(nf_nat_sip_expect_hook != NULL);
 564         BUG_ON(nf_nat_sdp_addr_hook != NULL);
 565         BUG_ON(nf_nat_sdp_port_hook != NULL);
 566         BUG_ON(nf_nat_sdp_session_hook != NULL);
 567         BUG_ON(nf_nat_sdp_media_hook != NULL);
 568         RCU_INIT_POINTER(nf_nat_sip_hook, ip_nat_sip);
 569         RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, ip_nat_sip_seq_adjust);
 570         RCU_INIT_POINTER(nf_nat_sip_expect_hook, ip_nat_sip_expect);
 571         RCU_INIT_POINTER(nf_nat_sdp_addr_hook, ip_nat_sdp_addr);
 572         RCU_INIT_POINTER(nf_nat_sdp_port_hook, ip_nat_sdp_port);
 573         RCU_INIT_POINTER(nf_nat_sdp_session_hook, ip_nat_sdp_session);
 574         RCU_INIT_POINTER(nf_nat_sdp_media_hook, ip_nat_sdp_media);
 575         nf_ct_helper_expectfn_register(&sip_nat);
 576         return 0;
 577 }
 578
 579 module_init(nf_nat_sip_init);
 580 module_exit(nf_nat_sip_fini);