release/src-rt/linux/linux-2.6/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, "%u.%u.%u.%u:%u",
  96                          NIPQUAD(newaddr), ntohs(newport));
  97
  98         return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
  99                              buffer, buflen);
 100 }
 101
 102 static int map_sip_addr(struct sk_buff *skb, unsigned int dataoff,
 103                         const char **dptr, unsigned int *datalen,
 104                         enum sip_header_types type)
 105 {
 106         enum ip_conntrack_info ctinfo;
 107         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 108         unsigned int matchlen, matchoff;
 109         union nf_inet_addr addr;
 110         __be16 port;
 111
 112         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, type, NULL,
 113                                     &matchoff, &matchlen, &addr, &port) <= 0)
 114                 return 1;
 115         return map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
 116                         &addr, port);
 117 }
 118
 119 static unsigned int ip_nat_sip(struct sk_buff *skb, unsigned int dataoff,
 120                                const char **dptr, unsigned int *datalen)
 121 {
 122         enum ip_conntrack_info ctinfo;
 123         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 124         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 125         unsigned int coff, matchoff, matchlen;
 126         enum sip_header_types hdr;
 127         union nf_inet_addr addr;
 128         __be16 port;
 129         int request, in_header;
 130
 131         /* Basic rules: requests and responses. */
 132         if (strnicmp(*dptr, "SIP/2.0", strlen("SIP/2.0")) != 0) {
 133                 if (ct_sip_parse_request(ct, *dptr, *datalen,
 134                                          &matchoff, &matchlen,
 135                                          &addr, &port) > 0 &&
 136                     !map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
 137                               &addr, port))
 138                         return NF_DROP;
 139                 request = 1;
 140         } else
 141                 request = 0;
 142
 143         if (nf_ct_protonum(ct) == IPPROTO_TCP)
 144                 hdr = SIP_HDR_VIA_TCP;
 145         else
 146                 hdr = SIP_HDR_VIA_UDP;
 147
 148         /* Translate topmost Via header and parameters */
 149         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
 150                                     hdr, NULL, &matchoff, &matchlen,
 151                                     &addr, &port) > 0) {
 152                 unsigned int matchend, poff, plen, buflen, n;
 153                 char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
 154
 155                 /* We're only interested in headers related to this
 156                  * connection */
 157                 if (request) {
 158                         if (addr.ip != ct->tuplehash[dir].tuple.src.u3.ip ||
 159                             port != ct->tuplehash[dir].tuple.src.u.udp.port)
 160                                 goto next;
 161                 } else {
 162                         if (addr.ip != ct->tuplehash[dir].tuple.dst.u3.ip ||
 163                             port != ct->tuplehash[dir].tuple.dst.u.udp.port)
 164                                 goto next;
 165                 }
 166
 167                 if (!map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
 168                               &addr, port))
 169                         return NF_DROP;
 170
 171                 matchend = matchoff + matchlen;
 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                         __be32 ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 181                         buflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(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                         __be32 ip = ct->tuplehash[!dir].tuple.src.u3.ip;
 195                         buflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(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         /* hook doesn't matter, but it has to do destination manip */
 263         nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
 264
 265         /* Change src to where master sends to, but only if the connection
 266          * actually came from the same source. */
 267         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip ==
 268             ct->master->tuplehash[exp->dir].tuple.src.u3.ip) {
 269                 range.flags = IP_NAT_RANGE_MAP_IPS;
 270                 range.min_ip = range.max_ip
 271                         = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
 272                 /* hook doesn't matter, but it has to do source manip */
 273                 nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
 274         }
 275 }
 276
 277 static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int dataoff,
 278                                       const char **dptr, unsigned int *datalen,
 279                                       struct nf_conntrack_expect *exp,
 280                                       unsigned int matchoff,
 281                                       unsigned int matchlen)
 282 {
 283         enum ip_conntrack_info ctinfo;
 284         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 285         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 286         __be32 newip;
 287         u_int16_t port;
 288         char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
 289         unsigned buflen;
 290
 291         /* Connection will come from reply */
 292         if (ct->tuplehash[dir].tuple.src.u3.ip == ct->tuplehash[!dir].tuple.dst.u3.ip)
 293                 newip = exp->tuple.dst.u3.ip;
 294         else
 295                 newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 296
 297         /* If the signalling port matches the connection's source port in the
 298          * original direction, try to use the destination port in the opposite
 299          * direction. */
 300         if (exp->tuple.dst.u.udp.port ==
 301             ct->tuplehash[dir].tuple.src.u.udp.port)
 302                 port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port);
 303         else
 304                 port = ntohs(exp->tuple.dst.u.udp.port);
 305
 306         exp->saved_ip = exp->tuple.dst.u3.ip;
 307         exp->tuple.dst.u3.ip = newip;
 308         exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
 309         exp->dir = !dir;
 310         exp->expectfn = ip_nat_sip_expected;
 311
 312         for (; port != 0; port++) {
 313                 exp->tuple.dst.u.udp.port = htons(port);
 314                 if (nf_conntrack_expect_related(exp) == 0)
 315                         break;
 316         }
 317
 318         if (port == 0)
 319                 return NF_DROP;
 320
 321         if (exp->tuple.dst.u3.ip != exp->saved_ip ||
 322             exp->tuple.dst.u.udp.port != exp->saved_proto.udp.port) {
 323                 buflen = sprintf(buffer, "%u.%u.%u.%u:%u",
 324                                  NIPQUAD(newip), port);
 325                 if (!mangle_packet(skb, dataoff, dptr, datalen,
 326                                    matchoff, matchlen, buffer, buflen))
 327                         goto err;
 328         }
 329         return NF_ACCEPT;
 330
 331 err:
 332         nf_conntrack_unexpect_related(exp);
 333         return NF_DROP;
 334 }
 335
 336 static int mangle_content_len(struct sk_buff *skb, unsigned int dataoff,
 337                               const char **dptr, unsigned int *datalen)
 338 {
 339         enum ip_conntrack_info ctinfo;
 340         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 341         unsigned int matchoff, matchlen;
 342         char buffer[sizeof("65536")];
 343         int buflen, c_len;
 344
 345         /* Get actual SDP length */
 346         if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen,
 347                                   SDP_HDR_VERSION, SDP_HDR_UNSPEC,
 348                                   &matchoff, &matchlen) <= 0)
 349                 return 0;
 350         c_len = *datalen - matchoff + strlen("v=");
 351
 352         /* Now, update SDP length */
 353         if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CONTENT_LENGTH,
 354                               &matchoff, &matchlen) <= 0)
 355                 return 0;
 356
 357         buflen = sprintf(buffer, "%u", c_len);
 358         return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
 359                              buffer, buflen);
 360 }
 361
 362 static int mangle_sdp_packet(struct sk_buff *skb, unsigned int dataoff,
 363                              const char **dptr, unsigned int *datalen,
 364                              unsigned int sdpoff,
 365                              enum sdp_header_types type,
 366                              enum sdp_header_types term,
 367                              char *buffer, int buflen)
 368 {
 369         enum ip_conntrack_info ctinfo;
 370         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 371         unsigned int matchlen, matchoff;
 372
 373         if (ct_sip_get_sdp_header(ct, *dptr, sdpoff, *datalen, type, term,
 374                                   &matchoff, &matchlen) <= 0)
 375                 return -ENOENT;
 376         return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
 377                              buffer, buflen) ? 0 : -EINVAL;
 378 }
 379
 380 static unsigned int ip_nat_sdp_addr(struct sk_buff *skb, unsigned int dataoff,
 381                                     const char **dptr, unsigned int *datalen,
 382                                     unsigned int sdpoff,
 383                                     enum sdp_header_types type,
 384                                     enum sdp_header_types term,
 385                                     const union nf_inet_addr *addr)
 386 {
 387         char buffer[sizeof("nnn.nnn.nnn.nnn")];
 388         unsigned int buflen;
 389
 390         buflen = sprintf(buffer, NIPQUAD_FMT, NIPQUAD(addr->ip));
 391         if (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff, type, term,
 392                               buffer, buflen))
 393                 return 0;
 394
 395         return mangle_content_len(skb, dataoff, dptr, datalen);
 396 }
 397
 398 static unsigned int ip_nat_sdp_port(struct sk_buff *skb, unsigned int dataoff,
 399                                     const char **dptr, unsigned int *datalen,
 400                                     unsigned int matchoff,
 401                                     unsigned int matchlen,
 402                                     u_int16_t port)
 403 {
 404         char buffer[sizeof("nnnnn")];
 405         unsigned int buflen;
 406
 407         buflen = sprintf(buffer, "%u", port);
 408         if (!mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
 409                            buffer, buflen))
 410                 return 0;
 411
 412         return mangle_content_len(skb, dataoff, dptr, datalen);
 413 }
 414
 415 static unsigned int ip_nat_sdp_session(struct sk_buff *skb, unsigned int dataoff,
 416                                        const char **dptr, unsigned int *datalen,
 417                                        unsigned int sdpoff,
 418                                        const union nf_inet_addr *addr)
 419 {
 420         char buffer[sizeof("nnn.nnn.nnn.nnn")];
 421         unsigned int buflen;
 422
 423         /* Mangle session description owner and contact addresses */
 424         buflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(addr->ip));
 425         if (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff,
 426                                SDP_HDR_OWNER_IP4, SDP_HDR_MEDIA,
 427                                buffer, buflen))
 428                 return 0;
 429
 430         switch (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff,
 431                                   SDP_HDR_CONNECTION_IP4, SDP_HDR_MEDIA,
 432                                   buffer, buflen)) {
 433         case 0:
 434         /*
 435          * RFC 2327:
 436          *
 437          * Session description
 438          *
 439          * c=* (connection information - not required if included in all media)
 440          */
 441         case -ENOENT:
 442                 break;
 443         default:
 444                 return 0;
 445         }
 446
 447         return mangle_content_len(skb, dataoff, dptr, datalen);
 448 }
 449
 450 /* So, this packet has hit the connection tracking matching code.
 451    Mangle it, and change the expectation to match the new version. */
 452 static unsigned int ip_nat_sdp_media(struct sk_buff *skb, unsigned int dataoff,
 453                                      const char **dptr, unsigned int *datalen,
 454                                      struct nf_conntrack_expect *rtp_exp,
 455                                      struct nf_conntrack_expect *rtcp_exp,
 456                                      unsigned int mediaoff,
 457                                      unsigned int medialen,
 458                                      union nf_inet_addr *rtp_addr)
 459 {
 460         enum ip_conntrack_info ctinfo;
 461         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 462         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 463         u_int16_t port;
 464
 465         /* Connection will come from reply */
 466         if (ct->tuplehash[dir].tuple.src.u3.ip ==
 467             ct->tuplehash[!dir].tuple.dst.u3.ip)
 468                 rtp_addr->ip = rtp_exp->tuple.dst.u3.ip;
 469         else
 470                 rtp_addr->ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 471
 472         rtp_exp->saved_ip = rtp_exp->tuple.dst.u3.ip;
 473         rtp_exp->tuple.dst.u3.ip = rtp_addr->ip;
 474         rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
 475         rtp_exp->dir = !dir;
 476         rtp_exp->expectfn = ip_nat_sip_expected;
 477
 478         rtcp_exp->saved_ip = rtcp_exp->tuple.dst.u3.ip;
 479         rtcp_exp->tuple.dst.u3.ip = rtp_addr->ip;
 480         rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
 481         rtcp_exp->dir = !dir;
 482         rtcp_exp->expectfn = ip_nat_sip_expected;
 483
 484         /* Try to get same pair of ports: if not, try to change them. */
 485         for (port = ntohs(rtp_exp->tuple.dst.u.udp.port);
 486              port != 0; port += 2) {
 487                 rtp_exp->tuple.dst.u.udp.port = htons(port);
 488                 if (nf_conntrack_expect_related(rtp_exp) != 0)
 489                         continue;
 490                 rtcp_exp->tuple.dst.u.udp.port = htons(port + 1);
 491                 if (nf_conntrack_expect_related(rtcp_exp) == 0)
 492                         break;
 493                 nf_conntrack_unexpect_related(rtp_exp);
 494         }
 495
 496         if (port == 0)
 497                 goto err1;
 498
 499         /* Update media port. */
 500         if (rtp_exp->tuple.dst.u.udp.port != rtp_exp->saved_proto.udp.port &&
 501             !ip_nat_sdp_port(skb, dataoff, dptr, datalen,
 502                              mediaoff, medialen, port))
 503                 goto err2;
 504
 505         return NF_ACCEPT;
 506
 507 err2:
 508         nf_conntrack_unexpect_related(rtp_exp);
 509         nf_conntrack_unexpect_related(rtcp_exp);
 510 err1:
 511         return NF_DROP;
 512 }
 513
 514 static void __exit nf_nat_sip_fini(void)
 515 {
 516         rcu_assign_pointer(nf_nat_sip_hook, NULL);
 517         rcu_assign_pointer(nf_nat_sip_seq_adjust_hook, NULL);
 518         rcu_assign_pointer(nf_nat_sip_expect_hook, NULL);
 519         rcu_assign_pointer(nf_nat_sdp_addr_hook, NULL);
 520         rcu_assign_pointer(nf_nat_sdp_port_hook, NULL);
 521         rcu_assign_pointer(nf_nat_sdp_session_hook, NULL);
 522         rcu_assign_pointer(nf_nat_sdp_media_hook, NULL);
 523         synchronize_rcu();
 524 }
 525
 526 static int __init nf_nat_sip_init(void)
 527 {
 528         BUG_ON(rcu_dereference(nf_nat_sip_hook));
 529         BUG_ON(rcu_dereference(nf_nat_sip_seq_adjust_hook));
 530         BUG_ON(rcu_dereference(nf_nat_sip_expect_hook));
 531         BUG_ON(rcu_dereference(nf_nat_sdp_addr_hook));
 532         BUG_ON(rcu_dereference(nf_nat_sdp_port_hook));
 533         BUG_ON(rcu_dereference(nf_nat_sdp_session_hook));
 534         BUG_ON(rcu_dereference(nf_nat_sdp_media_hook));
 535         rcu_assign_pointer(nf_nat_sip_hook, ip_nat_sip);
 536         rcu_assign_pointer(nf_nat_sip_seq_adjust_hook, ip_nat_sip_seq_adjust);
 537         rcu_assign_pointer(nf_nat_sip_expect_hook, ip_nat_sip_expect);
 538         rcu_assign_pointer(nf_nat_sdp_addr_hook, ip_nat_sdp_addr);
 539         rcu_assign_pointer(nf_nat_sdp_port_hook, ip_nat_sdp_port);
 540         rcu_assign_pointer(nf_nat_sdp_session_hook, ip_nat_sdp_session);
 541         rcu_assign_pointer(nf_nat_sdp_media_hook, ip_nat_sdp_media);
 542         return 0;
 543 }
 544
 545 module_init(nf_nat_sip_init);
 546 module_exit(nf_nat_sip_fini);