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                         nf_ct_helper_log(skb, ct, "cannot mangle SIP message");
 164                         return NF_DROP;
 165                 }
 166                 request = 1;
 167         } else
 168                 request = 0;
 169
 170         if (nf_ct_protonum(ct) == IPPROTO_TCP)
 171                 hdr = SIP_HDR_VIA_TCP;
 172         else
 173                 hdr = SIP_HDR_VIA_UDP;
 174
 175         /* Translate topmost Via header and parameters */
 176         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
 177                                     hdr, NULL, &matchoff, &matchlen,
 178                                     &addr, &port) > 0) {
 179                 unsigned int olen, matchend, poff, plen, buflen, n;
 180                 char buffer[INET6_ADDRSTRLEN + sizeof("[]:nnnnn")];
 181
 182                 /* We're only interested in headers related to this
 183                  * connection */
 184                 if (request) {
 185                         if (!nf_inet_addr_cmp(&addr,
 186                                         &ct->tuplehash[dir].tuple.src.u3) ||
 187                             port != ct->tuplehash[dir].tuple.src.u.udp.port)
 188                                 goto next;
 189                 } else {
 190                         if (!nf_inet_addr_cmp(&addr,
 191                                         &ct->tuplehash[dir].tuple.dst.u3) ||
 192                             port != ct->tuplehash[dir].tuple.dst.u.udp.port)
 193                                 goto next;
 194                 }
 195
 196                 olen = *datalen;
 197                 if (!map_addr(skb, protoff, dataoff, dptr, datalen,
 198                               matchoff, matchlen, &addr, port)) {
 199                         nf_ct_helper_log(skb, ct, "cannot mangle Via header");
 200                         return NF_DROP;
 201                 }
 202
 203                 matchend = matchoff + matchlen + *datalen - olen;
 204
 205                 /* The maddr= parameter (RFC 2361) specifies where to send
 206                  * the reply. */
 207                 if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
 208                                                "maddr=", &poff, &plen,
 209                                                &addr, true) > 0 &&
 210                     nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.src.u3) &&
 211                     !nf_inet_addr_cmp(&addr, &ct->tuplehash[!dir].tuple.dst.u3)) {
 212                         buflen = sip_sprintf_addr(ct, buffer,
 213                                         &ct->tuplehash[!dir].tuple.dst.u3,
 214                                         true);
 215                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 216                                            poff, plen, buffer, buflen)) {
 217                                 nf_ct_helper_log(skb, ct, "cannot mangle maddr");
 218                                 return NF_DROP;
 219                         }
 220                 }
 221
 222                 /* The received= parameter (RFC 2361) contains the address
 223                  * from which the server received the request. */
 224                 if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
 225                                                "received=", &poff, &plen,
 226                                                &addr, false) > 0 &&
 227                     nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.dst.u3) &&
 228                     !nf_inet_addr_cmp(&addr, &ct->tuplehash[!dir].tuple.src.u3)) {
 229                         buflen = sip_sprintf_addr(ct, buffer,
 230                                         &ct->tuplehash[!dir].tuple.src.u3,
 231                                         false);
 232                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 233                                            poff, plen, buffer, buflen))
 234                                 nf_ct_helper_log(skb, ct, "cannot mangle received");
 235                                 return NF_DROP;
 236                 }
 237
 238                 /* The rport= parameter (RFC 3581) contains the port number
 239                  * from which the server received the request. */
 240                 if (ct_sip_parse_numerical_param(ct, *dptr, matchend, *datalen,
 241                                                  "rport=", &poff, &plen,
 242                                                  &n) > 0 &&
 243                     htons(n) == ct->tuplehash[dir].tuple.dst.u.udp.port &&
 244                     htons(n) != ct->tuplehash[!dir].tuple.src.u.udp.port) {
 245                         __be16 p = ct->tuplehash[!dir].tuple.src.u.udp.port;
 246                         buflen = sprintf(buffer, "%u", ntohs(p));
 247                         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 248                                            poff, plen, buffer, buflen)) {
 249                                 nf_ct_helper_log(skb, ct, "cannot mangle rport");
 250                                 return NF_DROP;
 251                         }
 252                 }
 253         }
 254
 255 next:
 256         /* Translate Contact headers */
 257         coff = 0;
 258         in_header = 0;
 259         while (ct_sip_parse_header_uri(ct, *dptr, &coff, *datalen,
 260                                        SIP_HDR_CONTACT, &in_header,
 261                                        &matchoff, &matchlen,
 262                                        &addr, &port) > 0) {
 263                 if (!map_addr(skb, protoff, dataoff, dptr, datalen,
 264                               matchoff, matchlen,
 265                               &addr, port)) {
 266                         nf_ct_helper_log(skb, ct, "cannot mangle contact");
 267                         return NF_DROP;
 268                 }
 269         }
 270
 271         if (!map_sip_addr(skb, protoff, dataoff, dptr, datalen, SIP_HDR_FROM) ||
 272             !map_sip_addr(skb, protoff, dataoff, dptr, datalen, SIP_HDR_TO)) {
 273                 nf_ct_helper_log(skb, ct, "cannot mangle SIP from/to");
 274                 return NF_DROP;
 275         }
 276
 277         /* Mangle destination port for Cisco phones, then fix up checksums */
 278         if (dir == IP_CT_DIR_REPLY && ct_sip_info->forced_dport) {
 279                 struct udphdr *uh;
 280
 281                 if (!skb_make_writable(skb, skb->len)) {
 282                         nf_ct_helper_log(skb, ct, "cannot mangle packet");
 283                         return NF_DROP;
 284                 }
 285
 286                 uh = (void *)skb->data + protoff;
 287                 uh->dest = ct_sip_info->forced_dport;
 288
 289                 if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, protoff,
 290                                               0, 0, NULL, 0)) {
 291                         nf_ct_helper_log(skb, ct, "cannot mangle packet");
 292                         return NF_DROP;
 293                 }
 294         }
 295
 296         return NF_ACCEPT;
 297 }
 298
 299 static void nf_nat_sip_seq_adjust(struct sk_buff *skb, unsigned int protoff,
 300                                   s16 off)
 301 {
 302         enum ip_conntrack_info ctinfo;
 303         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 304         const struct tcphdr *th;
 305
 306         if (nf_ct_protonum(ct) != IPPROTO_TCP || off == 0)
 307                 return;
 308
 309         th = (struct tcphdr *)(skb->data + protoff);
 310         nf_nat_set_seq_adjust(ct, ctinfo, th->seq, off);
 311 }
 312
 313 /* Handles expected signalling connections and media streams */
 314 static void nf_nat_sip_expected(struct nf_conn *ct,
 315                                 struct nf_conntrack_expect *exp)
 316 {
 317         struct nf_nat_range range;
 318
 319         /* This must be a fresh one. */
 320         BUG_ON(ct->status & IPS_NAT_DONE_MASK);
 321
 322         /* For DST manip, map port here to where it's expected. */
 323         range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
 324         range.min_proto = range.max_proto = exp->saved_proto;
 325         range.min_addr = range.max_addr = exp->saved_addr;
 326         nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
 327
 328         /* Change src to where master sends to, but only if the connection
 329          * actually came from the same source. */
 330         if (nf_inet_addr_cmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
 331                              &ct->master->tuplehash[exp->dir].tuple.src.u3)) {
 332                 range.flags = NF_NAT_RANGE_MAP_IPS;
 333                 range.min_addr = range.max_addr
 334                         = ct->master->tuplehash[!exp->dir].tuple.dst.u3;
 335                 nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
 336         }
 337 }
 338
 339 static unsigned int nf_nat_sip_expect(struct sk_buff *skb, unsigned int protoff,
 340                                       unsigned int dataoff,
 341                                       const char **dptr, unsigned int *datalen,
 342                                       struct nf_conntrack_expect *exp,
 343                                       unsigned int matchoff,
 344                                       unsigned int matchlen)
 345 {
 346         enum ip_conntrack_info ctinfo;
 347         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 348         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 349         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 350         union nf_inet_addr newaddr;
 351         u_int16_t port;
 352         __be16 srcport;
 353         char buffer[INET6_ADDRSTRLEN + sizeof("[]:nnnnn")];
 354         unsigned int buflen;
 355
 356         /* Connection will come from reply */
 357         if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 358                              &ct->tuplehash[!dir].tuple.dst.u3))
 359                 newaddr = exp->tuple.dst.u3;
 360         else
 361                 newaddr = ct->tuplehash[!dir].tuple.dst.u3;
 362
 363         /* If the signalling port matches the connection's source port in the
 364          * original direction, try to use the destination port in the opposite
 365          * direction. */
 366         srcport = ct_sip_info->forced_dport ? :
 367                   ct->tuplehash[dir].tuple.src.u.udp.port;
 368         if (exp->tuple.dst.u.udp.port == srcport)
 369                 port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port);
 370         else
 371                 port = ntohs(exp->tuple.dst.u.udp.port);
 372
 373         exp->saved_addr = exp->tuple.dst.u3;
 374         exp->tuple.dst.u3 = newaddr;
 375         exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
 376         exp->dir = !dir;
 377         exp->expectfn = nf_nat_sip_expected;
 378
 379         for (; port != 0; port++) {
 380                 int ret;
 381
 382                 exp->tuple.dst.u.udp.port = htons(port);
 383                 ret = nf_ct_expect_related(exp);
 384                 if (ret == 0)
 385                         break;
 386                 else if (ret != -EBUSY) {
 387                         port = 0;
 388                         break;
 389                 }
 390         }
 391
 392         if (port == 0) {
 393                 nf_ct_helper_log(skb, ct, "all ports in use for SIP");
 394                 return NF_DROP;
 395         }
 396
 397         if (!nf_inet_addr_cmp(&exp->tuple.dst.u3, &exp->saved_addr) ||
 398             exp->tuple.dst.u.udp.port != exp->saved_proto.udp.port) {
 399                 buflen = sip_sprintf_addr_port(ct, buffer, &newaddr, port);
 400                 if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 401                                    matchoff, matchlen, buffer, buflen)) {
 402                         nf_ct_helper_log(skb, ct, "cannot mangle packet");
 403                         goto err;
 404                 }
 405         }
 406         return NF_ACCEPT;
 407
 408 err:
 409         nf_ct_unexpect_related(exp);
 410         return NF_DROP;
 411 }
 412
 413 static int mangle_content_len(struct sk_buff *skb, unsigned int protoff,
 414                               unsigned int dataoff,
 415                               const char **dptr, unsigned int *datalen)
 416 {
 417         enum ip_conntrack_info ctinfo;
 418         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 419         unsigned int matchoff, matchlen;
 420         char buffer[sizeof("65536")];
 421         int buflen, c_len;
 422
 423         /* Get actual SDP length */
 424         if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen,
 425                                   SDP_HDR_VERSION, SDP_HDR_UNSPEC,
 426                                   &matchoff, &matchlen) <= 0)
 427                 return 0;
 428         c_len = *datalen - matchoff + strlen("v=");
 429
 430         /* Now, update SDP length */
 431         if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CONTENT_LENGTH,
 432                               &matchoff, &matchlen) <= 0)
 433                 return 0;
 434
 435         buflen = sprintf(buffer, "%u", c_len);
 436         return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 437                              matchoff, matchlen, buffer, buflen);
 438 }
 439
 440 static int mangle_sdp_packet(struct sk_buff *skb, unsigned int protoff,
 441                              unsigned int dataoff,
 442                              const char **dptr, unsigned int *datalen,
 443                              unsigned int sdpoff,
 444                              enum sdp_header_types type,
 445                              enum sdp_header_types term,
 446                              char *buffer, int buflen)
 447 {
 448         enum ip_conntrack_info ctinfo;
 449         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 450         unsigned int matchlen, matchoff;
 451
 452         if (ct_sip_get_sdp_header(ct, *dptr, sdpoff, *datalen, type, term,
 453                                   &matchoff, &matchlen) <= 0)
 454                 return -ENOENT;
 455         return mangle_packet(skb, protoff, dataoff, dptr, datalen,
 456                              matchoff, matchlen, buffer, buflen) ? 0 : -EINVAL;
 457 }
 458
 459 static unsigned int nf_nat_sdp_addr(struct sk_buff *skb, unsigned int protoff,
 460                                     unsigned int dataoff,
 461                                     const char **dptr, unsigned int *datalen,
 462                                     unsigned int sdpoff,
 463                                     enum sdp_header_types type,
 464                                     enum sdp_header_types term,
 465                                     const union nf_inet_addr *addr)
 466 {
 467         enum ip_conntrack_info ctinfo;
 468         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 469         char buffer[INET6_ADDRSTRLEN];
 470         unsigned int buflen;
 471
 472         buflen = sip_sprintf_addr(ct, buffer, addr, false);
 473         if (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen,
 474                               sdpoff, type, term, buffer, buflen))
 475                 return 0;
 476
 477         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 478 }
 479
 480 static unsigned int nf_nat_sdp_port(struct sk_buff *skb, unsigned int protoff,
 481                                     unsigned int dataoff,
 482                                     const char **dptr, unsigned int *datalen,
 483                                     unsigned int matchoff,
 484                                     unsigned int matchlen,
 485                                     u_int16_t port)
 486 {
 487         char buffer[sizeof("nnnnn")];
 488         unsigned int buflen;
 489
 490         buflen = sprintf(buffer, "%u", port);
 491         if (!mangle_packet(skb, protoff, dataoff, dptr, datalen,
 492                            matchoff, matchlen, buffer, buflen))
 493                 return 0;
 494
 495         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 496 }
 497
 498 static unsigned int nf_nat_sdp_session(struct sk_buff *skb, unsigned int protoff,
 499                                        unsigned int dataoff,
 500                                        const char **dptr, unsigned int *datalen,
 501                                        unsigned int sdpoff,
 502                                        const union nf_inet_addr *addr)
 503 {
 504         enum ip_conntrack_info ctinfo;
 505         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 506         char buffer[INET6_ADDRSTRLEN];
 507         unsigned int buflen;
 508
 509         /* Mangle session description owner and contact addresses */
 510         buflen = sip_sprintf_addr(ct, buffer, addr, false);
 511         if (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen, sdpoff,
 512                               SDP_HDR_OWNER, SDP_HDR_MEDIA, buffer, buflen))
 513                 return 0;
 514
 515         switch (mangle_sdp_packet(skb, protoff, dataoff, dptr, datalen, sdpoff,
 516                                   SDP_HDR_CONNECTION, SDP_HDR_MEDIA,
 517                                   buffer, buflen)) {
 518         case 0:
 519         /*
 520          * RFC 2327:
 521          *
 522          * Session description
 523          *
 524          * c=* (connection information - not required if included in all media)
 525          */
 526         case -ENOENT:
 527                 break;
 528         default:
 529                 return 0;
 530         }
 531
 532         return mangle_content_len(skb, protoff, dataoff, dptr, datalen);
 533 }
 534
 535 /* So, this packet has hit the connection tracking matching code.
 536    Mangle it, and change the expectation to match the new version. */
 537 static unsigned int nf_nat_sdp_media(struct sk_buff *skb, unsigned int protoff,
 538                                      unsigned int dataoff,
 539                                      const char **dptr, unsigned int *datalen,
 540                                      struct nf_conntrack_expect *rtp_exp,
 541                                      struct nf_conntrack_expect *rtcp_exp,
 542                                      unsigned int mediaoff,
 543                                      unsigned int medialen,
 544                                      union nf_inet_addr *rtp_addr)
 545 {
 546         enum ip_conntrack_info ctinfo;
 547         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 548         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 549         u_int16_t port;
 550
 551         /* Connection will come from reply */
 552         if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 553                              &ct->tuplehash[!dir].tuple.dst.u3))
 554                 *rtp_addr = rtp_exp->tuple.dst.u3;
 555         else
 556                 *rtp_addr = ct->tuplehash[!dir].tuple.dst.u3;
 557
 558         rtp_exp->saved_addr = rtp_exp->tuple.dst.u3;
 559         rtp_exp->tuple.dst.u3 = *rtp_addr;
 560         rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
 561         rtp_exp->dir = !dir;
 562         rtp_exp->expectfn = nf_nat_sip_expected;
 563
 564         rtcp_exp->saved_addr = rtcp_exp->tuple.dst.u3;
 565         rtcp_exp->tuple.dst.u3 = *rtp_addr;
 566         rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
 567         rtcp_exp->dir = !dir;
 568         rtcp_exp->expectfn = nf_nat_sip_expected;
 569
 570         /* Try to get same pair of ports: if not, try to change them. */
 571         for (port = ntohs(rtp_exp->tuple.dst.u.udp.port);
 572              port != 0; port += 2) {
 573                 int ret;
 574
 575                 rtp_exp->tuple.dst.u.udp.port = htons(port);
 576                 ret = nf_ct_expect_related(rtp_exp);
 577                 if (ret == -EBUSY)
 578                         continue;
 579                 else if (ret < 0) {
 580                         port = 0;
 581                         break;
 582                 }
 583                 rtcp_exp->tuple.dst.u.udp.port = htons(port + 1);
 584                 ret = nf_ct_expect_related(rtcp_exp);
 585                 if (ret == 0)
 586                         break;
 587                 else if (ret == -EBUSY) {
 588                         nf_ct_unexpect_related(rtp_exp);
 589                         continue;
 590                 } else if (ret < 0) {
 591                         nf_ct_unexpect_related(rtp_exp);
 592                         port = 0;
 593                         break;
 594                 }
 595         }
 596
 597         if (port == 0) {
 598                 nf_ct_helper_log(skb, ct, "all ports in use for SDP media");
 599                 goto err1;
 600         }
 601
 602         /* Update media port. */
 603         if (rtp_exp->tuple.dst.u.udp.port != rtp_exp->saved_proto.udp.port &&
 604             !nf_nat_sdp_port(skb, protoff, dataoff, dptr, datalen,
 605                              mediaoff, medialen, port)) {
 606                 nf_ct_helper_log(skb, ct, "cannot mangle SDP message");
 607                 goto err2;
 608         }
 609
 610         return NF_ACCEPT;
 611
 612 err2:
 613         nf_ct_unexpect_related(rtp_exp);
 614         nf_ct_unexpect_related(rtcp_exp);
 615 err1:
 616         return NF_DROP;
 617 }
 618
 619 static struct nf_ct_helper_expectfn sip_nat = {
 620         .name           = "sip",
 621         .expectfn       = nf_nat_sip_expected,
 622 };
 623
 624 static void __exit nf_nat_sip_fini(void)
 625 {
 626         RCU_INIT_POINTER(nf_nat_sip_hook, NULL);
 627         RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, NULL);
 628         RCU_INIT_POINTER(nf_nat_sip_expect_hook, NULL);
 629         RCU_INIT_POINTER(nf_nat_sdp_addr_hook, NULL);
 630         RCU_INIT_POINTER(nf_nat_sdp_port_hook, NULL);
 631         RCU_INIT_POINTER(nf_nat_sdp_session_hook, NULL);
 632         RCU_INIT_POINTER(nf_nat_sdp_media_hook, NULL);
 633         nf_ct_helper_expectfn_unregister(&sip_nat);
 634         synchronize_rcu();
 635 }
 636
 637 static int __init nf_nat_sip_init(void)
 638 {
 639         BUG_ON(nf_nat_sip_hook != NULL);
 640         BUG_ON(nf_nat_sip_seq_adjust_hook != NULL);
 641         BUG_ON(nf_nat_sip_expect_hook != NULL);
 642         BUG_ON(nf_nat_sdp_addr_hook != NULL);
 643         BUG_ON(nf_nat_sdp_port_hook != NULL);
 644         BUG_ON(nf_nat_sdp_session_hook != NULL);
 645         BUG_ON(nf_nat_sdp_media_hook != NULL);
 646         RCU_INIT_POINTER(nf_nat_sip_hook, nf_nat_sip);
 647         RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, nf_nat_sip_seq_adjust);
 648         RCU_INIT_POINTER(nf_nat_sip_expect_hook, nf_nat_sip_expect);
 649         RCU_INIT_POINTER(nf_nat_sdp_addr_hook, nf_nat_sdp_addr);
 650         RCU_INIT_POINTER(nf_nat_sdp_port_hook, nf_nat_sdp_port);
 651         RCU_INIT_POINTER(nf_nat_sdp_session_hook, nf_nat_sdp_session);
 652         RCU_INIT_POINTER(nf_nat_sdp_media_hook, nf_nat_sdp_media);
 653         nf_ct_helper_expectfn_register(&sip_nat);
 654         return 0;
 655 }
 656
 657 module_init(nf_nat_sip_init);
 658 module_exit(nf_nat_sip_fini);