Pileus Git - ~andy/linux/blob - net/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, 2011, 2012 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/inet.h>
  16 #include <linux/udp.h>
  17 #include <linux/tcp.h>
  18
  19 #include <net/netfilter/nf_nat.h>
  20 #include <net/netfilter/nf_nat_helper.h>
  21 #include <net/netfilter/nf_conntrack_helper.h>
  22 #include <net/netfilter/nf_conntrack_expect.h>
  23 #include <linux/netfilter/nf_conntrack_sip.h>
  24
  25 MODULE_LICENSE("GPL");
  26 MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
  27 MODULE_DESCRIPTION("SIP NAT helper");
  28 MODULE_ALIAS("ip_nat_sip");
  29
  30
  31 static unsigned int mangle_packet(struct sk_buff *skb, unsigned int protoff,
  32                                   unsigned int dataoff,
  33                                   const char **dptr, unsigned int *datalen,
  34                                   unsigned int matchoff, unsigned int matchlen,
  35                                   const char *buffer, unsigned int buflen)
  36 {
  37         enum ip_conntrack_info ctinfo;
  38         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  39         struct tcphdr *th;
  40         unsigned int baseoff;
  41
  42         if (nf_ct_protonum(ct) == IPPROTO_TCP) {
  43                 th = (struct tcphdr *)(skb->data + protoff);
  44                 baseoff = protoff + th->doff * 4;
  45                 matchoff += dataoff - baseoff;
  46
  47                 if (!__nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
  48                                                 protoff, matchoff, matchlen,
  49                                                 buffer, buflen, false))
  50                         return 0;
  51         } else {
  52                 baseoff = protoff + sizeof(struct udphdr);
  53                 matchoff += dataoff - baseoff;
  54
  55                 if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
  56                                               protoff, matchoff, matchlen,
  57                                               buffer, buflen))
  58                         return 0;
  59         }
  60
  61         /* Reload data pointer and adjust datalen value */
  62         *dptr = skb->data + dataoff;
  63         *datalen += buflen - matchlen;
  64         return 1;
  65 }
  66
  67 static int sip_sprintf_addr(const struct nf_conn *ct, char *buffer,
  68                             const union nf_inet_addr *addr, bool delim)
  69 {
  70         if (nf_ct_l3num(ct) == NFPROTO_IPV4)
  71                 return sprintf(buffer, "%pI4", &addr->ip);
  72         else {
  73                 if (delim)
  74                         return sprintf(buffer, "[%pI6c]", &addr->ip6);
  75                 else
  76                         return sprintf(buffer, "%pI6c", &addr->ip6);
  77         }
  78 }
  79
  80 static int sip_sprintf_addr_port(const struct nf_conn *ct, char *buffer,
  81                                  const union nf_inet_addr *addr, u16 port)
  82 {
  83         if (nf_ct_l3num(ct) == NFPROTO_IPV4)
  84                 return sprintf(buffer, "%pI4:%u", &addr->ip, port);
  85         else
  86                 return sprintf(buffer, "[%pI6c]:%u", &addr->ip6, port);
  87 }
  88
  89 static int map_addr(struct sk_buff *skb, unsigned int protoff,
  90                     unsigned int dataoff,
  91                     const char **dptr, unsigned int *datalen,
  92                     unsigned int matchoff, unsigned int matchlen,
  93                     union nf_inet_addr *addr, __be16 port)
  94 {
  95         enum ip_conntrack_info ctinfo;
  96         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  97         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
  98         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
  99         char buffer[INET6_ADDRSTRLEN + sizeof("[]:nnnnn")];
 100         unsigned int buflen;
 101         union nf_inet_addr newaddr;
 102         __be16 newport;
 103
 104         if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3, addr) &&
 105             ct->tuplehash[dir].tuple.src.u.udp.port == port) {
 106                 newaddr = ct->tuplehash[!dir].tuple.dst.u3;
 107                 newport = ct->tuplehash[!dir].tuple.dst.u.udp.port;
 108         } else if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3, addr) &&
 109                    ct->tuplehash[dir].tuple.dst.u.udp.port == port) {
 110                 newaddr = ct->tuplehash[!dir].tuple.src.u3;
 111                 newport = ct_sip_info->forced_dport ? :
 112                           ct->tuplehash[!dir].tuple.src.u.udp.port;
 113         } else
 114                 return 1;
 115
 116         if (nf_inet_addr_cmp(&newaddr, addr) && newport == port)
 117                 return 1;
 118
 119         buflen = sip_sprintf_addr_port(ct, buffer, &newaddr, ntohs(newport));
 120         return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 121                              matchoff, matchlen, buffer, buflen);
 122 }
 123
 124 static int map_sip_addr(struct sk_buff *skb, unsigned int protoff,
 125                         unsigned int dataoff,
 126                         const char **dptr, unsigned int *datalen,
 127                         enum sip_header_types type)
 128 {
 129         enum ip_conntrack_info ctinfo;
 130         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 131         unsigned int matchlen, matchoff;
 132         union nf_inet_addr addr;
 133         __be16 port;
 134
 135         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, type, NULL,
 136                                     &matchoff, &matchlen, &addr, &port) <= 0)
 137                 return 1;
 138         return map_addr(skb, protoff, dataoff, dptr, datalen,
 139                         matchoff, matchlen, &addr, port);
 140 }
 141
 142 static unsigned int nf_nat_sip(struct sk_buff *skb, unsigned int protoff,
 143                                unsigned int dataoff,
 144                                const char **dptr, unsigned int *datalen)
 145 {
 146         enum ip_conntrack_info ctinfo;
 147         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 148         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 149         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 150         unsigned int coff, matchoff, matchlen;
 151         enum sip_header_types hdr;
 152         union nf_inet_addr addr;
 153         __be16 port;
 154         int request, in_header;
 155
 156         /* Basic rules: requests and responses. */
 157         if (strnicmp(*dptr, "SIP/2.0", strlen("SIP/2.0")) != 0) {
 158                 if (ct_sip_parse_request(ct, *dptr, *datalen,
 159                                          &matchoff, &matchlen,
 160                                          &addr, &port) > 0 &&
 161                     !map_addr(skb, protoff, dataoff, dptr, datalen,
 162                               matchoff, matchlen, &addr, port))
 163                         return NF_DROP;
 164                 request = 1;
 165         } else
 166                 request = 0;
 167
 168         if (nf_ct_protonum(ct) == IPPROTO_TCP)
 169                 hdr = SIP_HDR_VIA_TCP;
 170         else
 171                 hdr = SIP_HDR_VIA_UDP;
 172
 173         /* Translate topmost Via header and parameters */
 174         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
 175                                     hdr, NULL, &matchoff, &matchlen,
 176                                     &addr, &port) > 0) {
 177                 unsigned int olen, matchend, poff, plen, buflen, n;
 178                 char buffer[INET6_ADDRSTRLEN + sizeof("[]:nnnnn")];
 179
 180                 /* We're only interested in headers related to this
 181                  * connection */
 182                 if (request) {
 183                         if (!nf_inet_addr_cmp(&addr,
 184                                         &ct->tuplehash[dir].tuple.src.u3) ||
 185                             port != ct->tuplehash[dir].tuple.src.u.udp.port)
 186                                 goto next;
 187                 } else {
 188                         if (!nf_inet_addr_cmp(&addr,
 189                                         &ct->tuplehash[dir].tuple.dst.u3) ||
 190                             port != ct->tuplehash[dir].tuple.dst.u.udp.port)
 191                                 goto next;
 192                 }
 193
 194                 olen = *datalen;
 195                 if (!map_addr(skb, protoff, dataoff, dptr, datalen,
 196                               matchoff, matchlen, &addr, port))
 197                         return NF_DROP;
 198
 199                 matchend = matchoff + matchlen + *datalen - olen;
 200
 201                 /* The maddr= parameter (RFC 2361) specifies where to send
 202                  * the reply. */
 203                 if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
 204                                                "maddr=", &poff, &plen,
 205                                                &addr, true) > 0 &&
 206                     nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.src.u3) &&
 207                     !nf_inet_addr_cmp(&addr, &ct->tuplehash[!dir].tuple.dst.u3)) {
 208                         buflen = sip_sprintf_addr(ct, buffer,
 209                                         &ct->tuplehash[!dir].tuple.dst.u3,
 210                                         true);
 211                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 212                                            poff, plen, buffer, buflen))
 213                                 return NF_DROP;
 214                 }
 215
 216                 /* The received= parameter (RFC 2361) contains the address
 217                  * from which the server received the request. */
 218                 if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
 219                                                "received=", &poff, &plen,
 220                                                &addr, false) > 0 &&
 221                     nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.dst.u3) &&
 222                     !nf_inet_addr_cmp(&addr, &ct->tuplehash[!dir].tuple.src.u3)) {
 223                         buflen = sip_sprintf_addr(ct, buffer,
 224                                         &ct->tuplehash[!dir].tuple.src.u3,
 225                                         false);
 226                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 227                                            poff, plen, buffer, buflen))
 228                                 return NF_DROP;
 229                 }
 230
 231                 /* The rport= parameter (RFC 3581) contains the port number
 232                  * from which the server received the request. */
 233                 if (ct_sip_parse_numerical_param(ct, *dptr, matchend, *datalen,
 234                                                  "rport=", &poff, &plen,
 235                                                  &n) > 0 &&
 236                     htons(n) == ct->tuplehash[dir].tuple.dst.u.udp.port &&
 237                     htons(n) != ct->tuplehash[!dir].tuple.src.u.udp.port) {
 238                         __be16 p = ct->tuplehash[!dir].tuple.src.u.udp.port;
 239                         buflen = sprintf(buffer, "%u", ntohs(p));
 240                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 241                                            poff, plen, buffer, buflen))
 242                                 return NF_DROP;
 243                 }
 244         }
 245
 246 next:
 247         /* Translate Contact headers */
 248         coff = 0;
 249         in_header = 0;
 250         while (ct_sip_parse_header_uri(ct, *dptr, &coff, *datalen,
 251                                        SIP_HDR_CONTACT, &in_header,
 252                                        &matchoff, &matchlen,
 253                                        &addr, &port) > 0) {
 254                 if (!map_addr(skb, protoff, dataoff, dptr, datalen,
 255                               matchoff, matchlen,
 256                               &addr, port))
 257                         return NF_DROP;
 258         }
 259
 260         if (!map_sip_addr(skb, protoff, dataoff, dptr, datalen, SIP_HDR_FROM) ||
 261             !map_sip_addr(skb, protoff, dataoff, dptr, datalen, SIP_HDR_TO))
 262                 return NF_DROP;
 263
 264         /* Mangle destination port for Cisco phones, then fix up checksums */
 265         if (dir == IP_CT_DIR_REPLY && ct_sip_info->forced_dport) {
 266                 struct udphdr *uh;
 267
 268                 if (!skb_make_writable(skb, skb->len))
 269                         return NF_DROP;
 270
 271                 uh = (void *)skb->data + protoff;
 272                 uh->dest = ct_sip_info->forced_dport;
 273
 274                 if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, protoff,
 275                                               0, 0, NULL, 0))
 276                         return NF_DROP;
 277         }
 278
 279         return NF_ACCEPT;
 280 }
 281
 282 static void nf_nat_sip_seq_adjust(struct sk_buff *skb, unsigned int protoff,
 283                                   s16 off)
 284 {
 285         enum ip_conntrack_info ctinfo;
 286         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 287         const struct tcphdr *th;
 288
 289         if (nf_ct_protonum(ct) != IPPROTO_TCP || off == 0)
 290                 return;
 291
 292         th = (struct tcphdr *)(skb->data + protoff);
 293         nf_nat_set_seq_adjust(ct, ctinfo, th->seq, off);
 294 }
 295
 296 /* Handles expected signalling connections and media streams */
 297 static void nf_nat_sip_expected(struct nf_conn *ct,
 298                                 struct nf_conntrack_expect *exp)
 299 {
 300         struct nf_nat_range range;
 301
 302         /* This must be a fresh one. */
 303         BUG_ON(ct->status & IPS_NAT_DONE_MASK);
 304
 305         /* For DST manip, map port here to where it's expected. */
 306         range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
 307         range.min_proto = range.max_proto = exp->saved_proto;
 308         range.min_addr = range.max_addr = exp->saved_addr;
 309         nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
 310
 311         /* Change src to where master sends to, but only if the connection
 312          * actually came from the same source. */
 313         if (nf_inet_addr_cmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
 314                              &ct->master->tuplehash[exp->dir].tuple.src.u3)) {
 315                 range.flags = NF_NAT_RANGE_MAP_IPS;
 316                 range.min_addr = range.max_addr
 317                         = ct->master->tuplehash[!exp->dir].tuple.dst.u3;
 318                 nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
 319         }
 320 }
 321
 322 static unsigned int nf_nat_sip_expect(struct sk_buff *skb, unsigned int protoff,
 323                                       unsigned int dataoff,
 324                                       const char **dptr, unsigned int *datalen,
 325                                       struct nf_conntrack_expect *exp,
 326                                       unsigned int matchoff,
 327                                       unsigned int matchlen)
 328 {
 329         enum ip_conntrack_info ctinfo;
 330         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 331         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 332         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 333         union nf_inet_addr newaddr;
 334         u_int16_t port;
 335         __be16 srcport;
 336         char buffer[INET6_ADDRSTRLEN + sizeof("[]:nnnnn")];
 337         unsigned int buflen;
 338
 339         /* Connection will come from reply */
 340         if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 341                              &ct->tuplehash[!dir].tuple.dst.u3))
 342                 newaddr = exp->tuple.dst.u3;
 343         else
 344                 newaddr = ct->tuplehash[!dir].tuple.dst.u3;
 345
 346         /* If the signalling port matches the connection's source port in the
 347          * original direction, try to use the destination port in the opposite
 348          * direction. */
 349         srcport = ct_sip_info->forced_dport ? :
 350                   ct->tuplehash[dir].tuple.src.u.udp.port;
 351         if (exp->tuple.dst.u.udp.port == srcport)
 352                 port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port);
 353         else
 354                 port = ntohs(exp->tuple.dst.u.udp.port);
 355
 356         exp->saved_addr = exp->tuple.dst.u3;
 357         exp->tuple.dst.u3 = newaddr;
 358         exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
 359         exp->dir = !dir;
 360         exp->expectfn = nf_nat_sip_expected;
 361
 362         for (; port != 0; port++) {
 363                 int ret;
 364
 365                 exp->tuple.dst.u.udp.port = htons(port);
 366                 ret = nf_ct_expect_related(exp);
 367                 if (ret == 0)
 368                         break;
 369                 else if (ret != -EBUSY) {
 370                         port = 0;
 371                         break;
 372                 }
 373         }
 374
 375         if (port == 0)
 376                 return NF_DROP;
 377
 378         if (!nf_inet_addr_cmp(&exp->tuple.dst.u3, &exp->saved_addr) ||
 379             exp->tuple.dst.u.udp.port != exp->saved_proto.udp.port) {
 380                 buflen = sip_sprintf_addr_port(ct, buffer, &newaddr, port);
 381                 if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 382                                    matchoff, matchlen, buffer, buflen))
 383                         goto err;
 384         }
 385         return NF_ACCEPT;
 386
 387 err:
 388         nf_ct_unexpect_related(exp);
 389         return NF_DROP;
 390 }
 391
 392 static int mangle_content_len(struct sk_buff *skb, unsigned int protoff,
 393                               unsigned int dataoff,
 394                               const char **dptr, unsigned int *datalen)
 395 {
 396         enum ip_conntrack_info ctinfo;
 397         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 398         unsigned int matchoff, matchlen;
 399         char buffer[sizeof("65536")];
 400         int buflen, c_len;
 401
 402         /* Get actual SDP length */
 403         if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen,
 404                                   SDP_HDR_VERSION, SDP_HDR_UNSPEC,
 405                                   &matchoff, &matchlen) <= 0)
 406                 return 0;
 407         c_len = *datalen - matchoff + strlen("v=");
 408
 409         /* Now, update SDP length */
 410         if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CONTENT_LENGTH,
 411                               &matchoff, &matchlen) <= 0)
 412                 return 0;
 413
 414         buflen = sprintf(buffer, "%u", c_len);
 415         return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 416                              matchoff, matchlen, buffer, buflen);
 417 }
 418
 419 static int mangle_sdp_packet(struct sk_buff *skb, unsigned int protoff,
 420                              unsigned int dataoff,
 421                              const char **dptr, unsigned int *datalen,
 422                              unsigned int sdpoff,
 423                              enum sdp_header_types type,
 424                              enum sdp_header_types term,
 425                              char *buffer, int buflen)
 426 {
 427         enum ip_conntrack_info ctinfo;
 428         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 429         unsigned int matchlen, matchoff;
 430
 431         if (ct_sip_get_sdp_header(ct, *dptr, sdpoff, *datalen, type, term,
 432                                   &matchoff, &matchlen) <= 0)
 433                 return -ENOENT;
 434         return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 435                              matchoff, matchlen, buffer, buflen) ? 0 : -EINVAL;
 436 }
 437
 438 static unsigned int nf_nat_sdp_addr(struct sk_buff *skb, unsigned int protoff,
 439                                     unsigned int dataoff,
 440                                     const char **dptr, unsigned int *datalen,
 441                                     unsigned int sdpoff,
 442                                     enum sdp_header_types type,
 443                                     enum sdp_header_types term,
 444                                     const union nf_inet_addr *addr)
 445 {
 446         enum ip_conntrack_info ctinfo;
 447         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 448         char buffer[INET6_ADDRSTRLEN];
 449         unsigned int buflen;
 450
 451         buflen = sip_sprintf_addr(ct, buffer, addr, false);
 452         if (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen,
 453                               sdpoff, type, term, buffer, buflen))
 454                 return 0;
 455
 456         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 457 }
 458
 459 static unsigned int nf_nat_sdp_port(struct sk_buff *skb, unsigned int protoff,
 460                                     unsigned int dataoff,
 461                                     const char **dptr, unsigned int *datalen,
 462                                     unsigned int matchoff,
 463                                     unsigned int matchlen,
 464                                     u_int16_t port)
 465 {
 466         char buffer[sizeof("nnnnn")];
 467         unsigned int buflen;
 468
 469         buflen = sprintf(buffer, "%u", port);
 470         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 471                            matchoff, matchlen, buffer, buflen))
 472                 return 0;
 473
 474         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 475 }
 476
 477 static unsigned int nf_nat_sdp_session(struct sk_buff *skb, unsigned int protoff,
 478                                        unsigned int dataoff,
 479                                        const char **dptr, unsigned int *datalen,
 480                                        unsigned int sdpoff,
 481                                        const union nf_inet_addr *addr)
 482 {
 483         enum ip_conntrack_info ctinfo;
 484         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 485         char buffer[INET6_ADDRSTRLEN];
 486         unsigned int buflen;
 487
 488         /* Mangle session description owner and contact addresses */
 489         buflen = sip_sprintf_addr(ct, buffer, addr, false);
 490         if (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen, sdpoff,
 491                               SDP_HDR_OWNER, SDP_HDR_MEDIA, buffer, buflen))
 492                 return 0;
 493
 494         switch (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen, sdpoff,
 495                                   SDP_HDR_CONNECTION, SDP_HDR_MEDIA,
 496                                   buffer, buflen)) {
 497         case 0:
 498         /*
 499          * RFC 2327:
 500          *
 501          * Session description
 502          *
 503          * c=* (connection information - not required if included in all media)
 504          */
 505         case -ENOENT:
 506                 break;
 507         default:
 508                 return 0;
 509         }
 510
 511         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 512 }
 513
 514 /* So, this packet has hit the connection tracking matching code.
 515    Mangle it, and change the expectation to match the new version. */
 516 static unsigned int nf_nat_sdp_media(struct sk_buff *skb, unsigned int protoff,
 517                                      unsigned int dataoff,
 518                                      const char **dptr, unsigned int *datalen,
 519                                      struct nf_conntrack_expect *rtp_exp,
 520                                      struct nf_conntrack_expect *rtcp_exp,
 521                                      unsigned int mediaoff,
 522                                      unsigned int medialen,
 523                                      union nf_inet_addr *rtp_addr)
 524 {
 525         enum ip_conntrack_info ctinfo;
 526         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 527         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 528         u_int16_t port;
 529
 530         /* Connection will come from reply */
 531         if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 532                              &ct->tuplehash[!dir].tuple.dst.u3))
 533                 *rtp_addr = rtp_exp->tuple.dst.u3;
 534         else
 535                 *rtp_addr = ct->tuplehash[!dir].tuple.dst.u3;
 536
 537         rtp_exp->saved_addr = rtp_exp->tuple.dst.u3;
 538         rtp_exp->tuple.dst.u3 = *rtp_addr;
 539         rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
 540         rtp_exp->dir = !dir;
 541         rtp_exp->expectfn = nf_nat_sip_expected;
 542
 543         rtcp_exp->saved_addr = rtcp_exp->tuple.dst.u3;
 544         rtcp_exp->tuple.dst.u3 = *rtp_addr;
 545         rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
 546         rtcp_exp->dir = !dir;
 547         rtcp_exp->expectfn = nf_nat_sip_expected;
 548
 549         /* Try to get same pair of ports: if not, try to change them. */
 550         for (port = ntohs(rtp_exp->tuple.dst.u.udp.port);
 551              port != 0; port += 2) {
 552                 int ret;
 553
 554                 rtp_exp->tuple.dst.u.udp.port = htons(port);
 555                 ret = nf_ct_expect_related(rtp_exp);
 556                 if (ret == -EBUSY)
 557                         continue;
 558                 else if (ret < 0) {
 559                         port = 0;
 560                         break;
 561                 }
 562                 rtcp_exp->tuple.dst.u.udp.port = htons(port + 1);
 563                 ret = nf_ct_expect_related(rtcp_exp);
 564                 if (ret == 0)
 565                         break;
 566                 else if (ret == -EBUSY) {
 567                         nf_ct_unexpect_related(rtp_exp);
 568                         continue;
 569                 } else if (ret < 0) {
 570                         nf_ct_unexpect_related(rtp_exp);
 571                         port = 0;
 572                         break;
 573                 }
 574         }
 575
 576         if (port == 0)
 577                 goto err1;
 578
 579         /* Update media port. */
 580         if (rtp_exp->tuple.dst.u.udp.port != rtp_exp->saved_proto.udp.port &&
 581             !nf_nat_sdp_port(skb, protoff, dataoff, dptr, datalen,
 582                              mediaoff, medialen, port))
 583                 goto err2;
 584
 585         return NF_ACCEPT;
 586
 587 err2:
 588         nf_ct_unexpect_related(rtp_exp);
 589         nf_ct_unexpect_related(rtcp_exp);
 590 err1:
 591         return NF_DROP;
 592 }
 593
 594 static struct nf_ct_helper_expectfn sip_nat = {
 595         .name           = "sip",
 596         .expectfn       = nf_nat_sip_expected,
 597 };
 598
 599 static void __exit nf_nat_sip_fini(void)
 600 {
 601         RCU_INIT_POINTER(nf_nat_sip_hook, NULL);
 602         RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, NULL);
 603         RCU_INIT_POINTER(nf_nat_sip_expect_hook, NULL);
 604         RCU_INIT_POINTER(nf_nat_sdp_addr_hook, NULL);
 605         RCU_INIT_POINTER(nf_nat_sdp_port_hook, NULL);
 606         RCU_INIT_POINTER(nf_nat_sdp_session_hook, NULL);
 607         RCU_INIT_POINTER(nf_nat_sdp_media_hook, NULL);
 608         nf_ct_helper_expectfn_unregister(&sip_nat);
 609         synchronize_rcu();
 610 }
 611
 612 static int __init nf_nat_sip_init(void)
 613 {
 614         BUG_ON(nf_nat_sip_hook != NULL);
 615         BUG_ON(nf_nat_sip_seq_adjust_hook != NULL);
 616         BUG_ON(nf_nat_sip_expect_hook != NULL);
 617         BUG_ON(nf_nat_sdp_addr_hook != NULL);
 618         BUG_ON(nf_nat_sdp_port_hook != NULL);
 619         BUG_ON(nf_nat_sdp_session_hook != NULL);
 620         BUG_ON(nf_nat_sdp_media_hook != NULL);
 621         RCU_INIT_POINTER(nf_nat_sip_hook, nf_nat_sip);
 622         RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, nf_nat_sip_seq_adjust);
 623         RCU_INIT_POINTER(nf_nat_sip_expect_hook, nf_nat_sip_expect);
 624         RCU_INIT_POINTER(nf_nat_sdp_addr_hook, nf_nat_sdp_addr);
 625         RCU_INIT_POINTER(nf_nat_sdp_port_hook, nf_nat_sdp_port);
 626         RCU_INIT_POINTER(nf_nat_sdp_session_hook, nf_nat_sdp_session);
 627         RCU_INIT_POINTER(nf_nat_sdp_media_hook, nf_nat_sdp_media);
 628         nf_ct_helper_expectfn_register(&sip_nat);
 629         return 0;
 630 }
 631
 632 module_init(nf_nat_sip_init);
 633 module_exit(nf_nat_sip_fini);