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