net/ipv4/netfilter/nf_nat_h323.c

   1 /*
   2  * H.323 extension for NAT alteration.
   3  *
   4  * Copyright (c) 2006 Jing Min Zhao <zhaojingmin@users.sourceforge.net>
   5  *
   6  * This source code is licensed under General Public License version 2.
   7  *
   8  * Based on the 'brute force' H.323 NAT module by
   9  * Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/tcp.h>
  14 #include <net/tcp.h>
  15
  16 #include <net/netfilter/nf_nat.h>
  17 #include <net/netfilter/nf_nat_helper.h>
  18 #include <net/netfilter/nf_nat_rule.h>
  19 #include <net/netfilter/nf_conntrack_helper.h>
  20 #include <net/netfilter/nf_conntrack_expect.h>
  21 #include <linux/netfilter/nf_conntrack_h323.h>
  22
  23 /****************************************************************************/
  24 static int set_addr(struct sk_buff *skb,
  25                     unsigned char **data, int dataoff,
  26                     unsigned int addroff, __be32 ip, __be16 port)
  27 {
  28         enum ip_conntrack_info ctinfo;
  29         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  30         struct {
  31                 __be32 ip;
  32                 __be16 port;
  33         } __attribute__ ((__packed__)) buf;
  34         const struct tcphdr *th;
  35         struct tcphdr _tcph;
  36
  37         buf.ip = ip;
  38         buf.port = port;
  39         addroff += dataoff;
  40
  41         if (ip_hdr(skb)->protocol == IPPROTO_TCP) {
  42                 if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
  43                                               addroff, sizeof(buf),
  44                                               (char *) &buf, sizeof(buf))) {
  45                         if (net_ratelimit())
  46                                 pr_notice("nf_nat_h323: nf_nat_mangle_tcp_packet"
  47                                        " error\n");
  48                         return -1;
  49                 }
  50
  51                 /* Relocate data pointer */
  52                 th = skb_header_pointer(skb, ip_hdrlen(skb),
  53                                         sizeof(_tcph), &_tcph);
  54                 if (th == NULL)
  55                         return -1;
  56                 *data = skb->data + ip_hdrlen(skb) + th->doff * 4 + dataoff;
  57         } else {
  58                 if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
  59                                               addroff, sizeof(buf),
  60                                               (char *) &buf, sizeof(buf))) {
  61                         if (net_ratelimit())
  62                                 pr_notice("nf_nat_h323: nf_nat_mangle_udp_packet"
  63                                        " error\n");
  64                         return -1;
  65                 }
  66                 /* nf_nat_mangle_udp_packet uses skb_make_writable() to copy
  67                  * or pull everything in a linear buffer, so we can safely
  68                  * use the skb pointers now */
  69                 *data = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr);
  70         }
  71
  72         return 0;
  73 }
  74
  75 /****************************************************************************/
  76 static int set_h225_addr(struct sk_buff *skb,
  77                          unsigned char **data, int dataoff,
  78                          TransportAddress *taddr,
  79                          union nf_inet_addr *addr, __be16 port)
  80 {
  81         return set_addr(skb, data, dataoff, taddr->ipAddress.ip,
  82                         addr->ip, port);
  83 }
  84
  85 /****************************************************************************/
  86 static int set_h245_addr(struct sk_buff *skb,
  87                          unsigned char **data, int dataoff,
  88                          H245_TransportAddress *taddr,
  89                          union nf_inet_addr *addr, __be16 port)
  90 {
  91         return set_addr(skb, data, dataoff,
  92                         taddr->unicastAddress.iPAddress.network,
  93                         addr->ip, port);
  94 }
  95
  96 /****************************************************************************/
  97 static int set_sig_addr(struct sk_buff *skb, struct nf_conn *ct,
  98                         enum ip_conntrack_info ctinfo,
  99                         unsigned char **data,
 100                         TransportAddress *taddr, int count)
 101 {
 102         const struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
 103         int dir = CTINFO2DIR(ctinfo);
 104         int i;
 105         __be16 port;
 106         union nf_inet_addr addr;
 107
 108         for (i = 0; i < count; i++) {
 109                 if (get_h225_addr(ct, *data, &taddr[i], &addr, &port)) {
 110                         if (addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
 111                             port == info->sig_port[dir]) {
 112                                 /* GW->GK */
 113
 114                                 /* Fix for Gnomemeeting */
 115                                 if (i > 0 &&
 116                                     get_h225_addr(ct, *data, &taddr[0],
 117                                                   &addr, &port) &&
 118                                     (ntohl(addr.ip) & 0xff000000) == 0x7f000000)
 119                                         i = 0;
 120
 121                                 pr_debug("nf_nat_ras: set signal address %pI4:%hu->%pI4:%hu\n",
 122                                          &addr.ip, port,
 123                                          &ct->tuplehash[!dir].tuple.dst.u3.ip,
 124                                          info->sig_port[!dir]);
 125                                 return set_h225_addr(skb, data, 0, &taddr[i],
 126                                                      &ct->tuplehash[!dir].
 127                                                      tuple.dst.u3,
 128                                                      info->sig_port[!dir]);
 129                         } else if (addr.ip == ct->tuplehash[dir].tuple.dst.u3.ip &&
 130                                    port == info->sig_port[dir]) {
 131                                 /* GK->GW */
 132                                 pr_debug("nf_nat_ras: set signal address %pI4:%hu->%pI4:%hu\n",
 133                                          &addr.ip, port,
 134                                          &ct->tuplehash[!dir].tuple.src.u3.ip,
 135                                          info->sig_port[!dir]);
 136                                 return set_h225_addr(skb, data, 0, &taddr[i],
 137                                                      &ct->tuplehash[!dir].
 138                                                      tuple.src.u3,
 139                                                      info->sig_port[!dir]);
 140                         }
 141                 }
 142         }
 143
 144         return 0;
 145 }
 146
 147 /****************************************************************************/
 148 static int set_ras_addr(struct sk_buff *skb, struct nf_conn *ct,
 149                         enum ip_conntrack_info ctinfo,
 150                         unsigned char **data,
 151                         TransportAddress *taddr, int count)
 152 {
 153         int dir = CTINFO2DIR(ctinfo);
 154         int i;
 155         __be16 port;
 156         union nf_inet_addr addr;
 157
 158         for (i = 0; i < count; i++) {
 159                 if (get_h225_addr(ct, *data, &taddr[i], &addr, &port) &&
 160                     addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
 161                     port == ct->tuplehash[dir].tuple.src.u.udp.port) {
 162                         pr_debug("nf_nat_ras: set rasAddress %pI4:%hu->%pI4:%hu\n",
 163                                  &addr.ip, ntohs(port),
 164                                  &ct->tuplehash[!dir].tuple.dst.u3.ip,
 165                                  ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port));
 166                         return set_h225_addr(skb, data, 0, &taddr[i],
 167                                              &ct->tuplehash[!dir].tuple.dst.u3,
 168                                              ct->tuplehash[!dir].tuple.
 169                                                                 dst.u.udp.port);
 170                 }
 171         }
 172
 173         return 0;
 174 }
 175
 176 /****************************************************************************/
 177 static int nat_rtp_rtcp(struct sk_buff *skb, struct nf_conn *ct,
 178                         enum ip_conntrack_info ctinfo,
 179                         unsigned char **data, int dataoff,
 180                         H245_TransportAddress *taddr,
 181                         __be16 port, __be16 rtp_port,
 182                         struct nf_conntrack_expect *rtp_exp,
 183                         struct nf_conntrack_expect *rtcp_exp)
 184 {
 185         struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
 186         int dir = CTINFO2DIR(ctinfo);
 187         int i;
 188         u_int16_t nated_port;
 189
 190         /* Set expectations for NAT */
 191         rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
 192         rtp_exp->expectfn = nf_nat_follow_master;
 193         rtp_exp->dir = !dir;
 194         rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
 195         rtcp_exp->expectfn = nf_nat_follow_master;
 196         rtcp_exp->dir = !dir;
 197
 198         /* Lookup existing expects */
 199         for (i = 0; i < H323_RTP_CHANNEL_MAX; i++) {
 200                 if (info->rtp_port[i][dir] == rtp_port) {
 201                         /* Expected */
 202
 203                         /* Use allocated ports first. This will refresh
 204                          * the expects */
 205                         rtp_exp->tuple.dst.u.udp.port = info->rtp_port[i][dir];
 206                         rtcp_exp->tuple.dst.u.udp.port =
 207                             htons(ntohs(info->rtp_port[i][dir]) + 1);
 208                         break;
 209                 } else if (info->rtp_port[i][dir] == 0) {
 210                         /* Not expected */
 211                         break;
 212                 }
 213         }
 214
 215         /* Run out of expectations */
 216         if (i >= H323_RTP_CHANNEL_MAX) {
 217                 if (net_ratelimit())
 218                         pr_notice("nf_nat_h323: out of expectations\n");
 219                 return 0;
 220         }
 221
 222         /* Try to get a pair of ports. */
 223         for (nated_port = ntohs(rtp_exp->tuple.dst.u.udp.port);
 224              nated_port != 0; nated_port += 2) {
 225                 int ret;
 226
 227                 rtp_exp->tuple.dst.u.udp.port = htons(nated_port);
 228                 ret = nf_ct_expect_related(rtp_exp);
 229                 if (ret == 0) {
 230                         rtcp_exp->tuple.dst.u.udp.port =
 231                             htons(nated_port + 1);
 232                         ret = nf_ct_expect_related(rtcp_exp);
 233                         if (ret == 0)
 234                                 break;
 235                         else if (ret != -EBUSY) {
 236                                 nf_ct_unexpect_related(rtp_exp);
 237                                 nated_port = 0;
 238                                 break;
 239                         }
 240                 } else if (ret != -EBUSY) {
 241                         nated_port = 0;
 242                         break;
 243                 }
 244         }
 245
 246         if (nated_port == 0) {  /* No port available */
 247                 if (net_ratelimit())
 248                         pr_notice("nf_nat_h323: out of RTP ports\n");
 249                 return 0;
 250         }
 251
 252         /* Modify signal */
 253         if (set_h245_addr(skb, data, dataoff, taddr,
 254                           &ct->tuplehash[!dir].tuple.dst.u3,
 255                           htons((port & htons(1)) ? nated_port + 1 :
 256                                                     nated_port)) == 0) {
 257                 /* Save ports */
 258                 info->rtp_port[i][dir] = rtp_port;
 259                 info->rtp_port[i][!dir] = htons(nated_port);
 260         } else {
 261                 nf_ct_unexpect_related(rtp_exp);
 262                 nf_ct_unexpect_related(rtcp_exp);
 263                 return -1;
 264         }
 265
 266         /* Success */
 267         pr_debug("nf_nat_h323: expect RTP %pI4:%hu->%pI4:%hu\n",
 268                  &rtp_exp->tuple.src.u3.ip,
 269                  ntohs(rtp_exp->tuple.src.u.udp.port),
 270                  &rtp_exp->tuple.dst.u3.ip,
 271                  ntohs(rtp_exp->tuple.dst.u.udp.port));
 272         pr_debug("nf_nat_h323: expect RTCP %pI4:%hu->%pI4:%hu\n",
 273                  &rtcp_exp->tuple.src.u3.ip,
 274                  ntohs(rtcp_exp->tuple.src.u.udp.port),
 275                  &rtcp_exp->tuple.dst.u3.ip,
 276                  ntohs(rtcp_exp->tuple.dst.u.udp.port));
 277
 278         return 0;
 279 }
 280
 281 /****************************************************************************/
 282 static int nat_t120(struct sk_buff *skb, struct nf_conn *ct,
 283                     enum ip_conntrack_info ctinfo,
 284                     unsigned char **data, int dataoff,
 285                     H245_TransportAddress *taddr, __be16 port,
 286                     struct nf_conntrack_expect *exp)
 287 {
 288         int dir = CTINFO2DIR(ctinfo);
 289         u_int16_t nated_port = ntohs(port);
 290
 291         /* Set expectations for NAT */
 292         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 293         exp->expectfn = nf_nat_follow_master;
 294         exp->dir = !dir;
 295
 296         /* Try to get same port: if not, try to change it. */
 297         for (; nated_port != 0; nated_port++) {
 298                 int ret;
 299
 300                 exp->tuple.dst.u.tcp.port = htons(nated_port);
 301                 ret = nf_ct_expect_related(exp);
 302                 if (ret == 0)
 303                         break;
 304                 else if (ret != -EBUSY) {
 305                         nated_port = 0;
 306                         break;
 307                 }
 308         }
 309
 310         if (nated_port == 0) {  /* No port available */
 311                 if (net_ratelimit())
 312                         pr_notice("nf_nat_h323: out of TCP ports\n");
 313                 return 0;
 314         }
 315
 316         /* Modify signal */
 317         if (set_h245_addr(skb, data, dataoff, taddr,
 318                           &ct->tuplehash[!dir].tuple.dst.u3,
 319                           htons(nated_port)) < 0) {
 320                 nf_ct_unexpect_related(exp);
 321                 return -1;
 322         }
 323
 324         pr_debug("nf_nat_h323: expect T.120 %pI4:%hu->%pI4:%hu\n",
 325                  &exp->tuple.src.u3.ip,
 326                  ntohs(exp->tuple.src.u.tcp.port),
 327                  &exp->tuple.dst.u3.ip,
 328                  ntohs(exp->tuple.dst.u.tcp.port));
 329
 330         return 0;
 331 }
 332
 333 /****************************************************************************/
 334 static int nat_h245(struct sk_buff *skb, struct nf_conn *ct,
 335                     enum ip_conntrack_info ctinfo,
 336                     unsigned char **data, int dataoff,
 337                     TransportAddress *taddr, __be16 port,
 338                     struct nf_conntrack_expect *exp)
 339 {
 340         struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
 341         int dir = CTINFO2DIR(ctinfo);
 342         u_int16_t nated_port = ntohs(port);
 343
 344         /* Set expectations for NAT */
 345         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 346         exp->expectfn = nf_nat_follow_master;
 347         exp->dir = !dir;
 348
 349         /* Check existing expects */
 350         if (info->sig_port[dir] == port)
 351                 nated_port = ntohs(info->sig_port[!dir]);
 352
 353         /* Try to get same port: if not, try to change it. */
 354         for (; nated_port != 0; nated_port++) {
 355                 int ret;
 356
 357                 exp->tuple.dst.u.tcp.port = htons(nated_port);
 358                 ret = nf_ct_expect_related(exp);
 359                 if (ret == 0)
 360                         break;
 361                 else if (ret != -EBUSY) {
 362                         nated_port = 0;
 363                         break;
 364                 }
 365         }
 366
 367         if (nated_port == 0) {  /* No port available */
 368                 if (net_ratelimit())
 369                         pr_notice("nf_nat_q931: out of TCP ports\n");
 370                 return 0;
 371         }
 372
 373         /* Modify signal */
 374         if (set_h225_addr(skb, data, dataoff, taddr,
 375                           &ct->tuplehash[!dir].tuple.dst.u3,
 376                           htons(nated_port)) == 0) {
 377                 /* Save ports */
 378                 info->sig_port[dir] = port;
 379                 info->sig_port[!dir] = htons(nated_port);
 380         } else {
 381                 nf_ct_unexpect_related(exp);
 382                 return -1;
 383         }
 384
 385         pr_debug("nf_nat_q931: expect H.245 %pI4:%hu->%pI4:%hu\n",
 386                  &exp->tuple.src.u3.ip,
 387                  ntohs(exp->tuple.src.u.tcp.port),
 388                  &exp->tuple.dst.u3.ip,
 389                  ntohs(exp->tuple.dst.u.tcp.port));
 390
 391         return 0;
 392 }
 393
 394 /****************************************************************************
 395  * This conntrack expect function replaces nf_conntrack_q931_expect()
 396  * which was set by nf_conntrack_h323.c.
 397  ****************************************************************************/
 398 static void ip_nat_q931_expect(struct nf_conn *new,
 399                                struct nf_conntrack_expect *this)
 400 {
 401         struct nf_nat_range range;
 402
 403         if (this->tuple.src.u3.ip != 0) {       /* Only accept calls from GK */
 404                 nf_nat_follow_master(new, this);
 405                 return;
 406         }
 407
 408         /* This must be a fresh one. */
 409         BUG_ON(new->status & IPS_NAT_DONE_MASK);
 410
 411         /* Change src to where master sends to */
 412         range.flags = IP_NAT_RANGE_MAP_IPS;
 413         range.min_ip = range.max_ip = new->tuplehash[!this->dir].tuple.src.u3.ip;
 414         nf_nat_setup_info(new, &range, IP_NAT_MANIP_SRC);
 415
 416         /* For DST manip, map port here to where it's expected. */
 417         range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
 418         range.min = range.max = this->saved_proto;
 419         range.min_ip = range.max_ip =
 420             new->master->tuplehash[!this->dir].tuple.src.u3.ip;
 421         nf_nat_setup_info(new, &range, IP_NAT_MANIP_DST);
 422 }
 423
 424 /****************************************************************************/
 425 static int nat_q931(struct sk_buff *skb, struct nf_conn *ct,
 426                     enum ip_conntrack_info ctinfo,
 427                     unsigned char **data, TransportAddress *taddr, int idx,
 428                     __be16 port, struct nf_conntrack_expect *exp)
 429 {
 430         struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
 431         int dir = CTINFO2DIR(ctinfo);
 432         u_int16_t nated_port = ntohs(port);
 433         union nf_inet_addr addr;
 434
 435         /* Set expectations for NAT */
 436         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 437         exp->expectfn = ip_nat_q931_expect;
 438         exp->dir = !dir;
 439
 440         /* Check existing expects */
 441         if (info->sig_port[dir] == port)
 442                 nated_port = ntohs(info->sig_port[!dir]);
 443
 444         /* Try to get same port: if not, try to change it. */
 445         for (; nated_port != 0; nated_port++) {
 446                 int ret;
 447
 448                 exp->tuple.dst.u.tcp.port = htons(nated_port);
 449                 ret = nf_ct_expect_related(exp);
 450                 if (ret == 0)
 451                         break;
 452                 else if (ret != -EBUSY) {
 453                         nated_port = 0;
 454                         break;
 455                 }
 456         }
 457
 458         if (nated_port == 0) {  /* No port available */
 459                 if (net_ratelimit())
 460                         pr_notice("nf_nat_ras: out of TCP ports\n");
 461                 return 0;
 462         }
 463
 464         /* Modify signal */
 465         if (set_h225_addr(skb, data, 0, &taddr[idx],
 466                           &ct->tuplehash[!dir].tuple.dst.u3,
 467                           htons(nated_port)) == 0) {
 468                 /* Save ports */
 469                 info->sig_port[dir] = port;
 470                 info->sig_port[!dir] = htons(nated_port);
 471
 472                 /* Fix for Gnomemeeting */
 473                 if (idx > 0 &&
 474                     get_h225_addr(ct, *data, &taddr[0], &addr, &port) &&
 475                     (ntohl(addr.ip) & 0xff000000) == 0x7f000000) {
 476                         set_h225_addr(skb, data, 0, &taddr[0],
 477                                       &ct->tuplehash[!dir].tuple.dst.u3,
 478                                       info->sig_port[!dir]);
 479                 }
 480         } else {
 481                 nf_ct_unexpect_related(exp);
 482                 return -1;
 483         }
 484
 485         /* Success */
 486         pr_debug("nf_nat_ras: expect Q.931 %pI4:%hu->%pI4:%hu\n",
 487                  &exp->tuple.src.u3.ip,
 488                  ntohs(exp->tuple.src.u.tcp.port),
 489                  &exp->tuple.dst.u3.ip,
 490                  ntohs(exp->tuple.dst.u.tcp.port));
 491
 492         return 0;
 493 }
 494
 495 /****************************************************************************/
 496 static void ip_nat_callforwarding_expect(struct nf_conn *new,
 497                                          struct nf_conntrack_expect *this)
 498 {
 499         struct nf_nat_range range;
 500
 501         /* This must be a fresh one. */
 502         BUG_ON(new->status & IPS_NAT_DONE_MASK);
 503
 504         /* Change src to where master sends to */
 505         range.flags = IP_NAT_RANGE_MAP_IPS;
 506         range.min_ip = range.max_ip = new->tuplehash[!this->dir].tuple.src.u3.ip;
 507         nf_nat_setup_info(new, &range, IP_NAT_MANIP_SRC);
 508
 509         /* For DST manip, map port here to where it's expected. */
 510         range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
 511         range.min = range.max = this->saved_proto;
 512         range.min_ip = range.max_ip = this->saved_ip;
 513         nf_nat_setup_info(new, &range, IP_NAT_MANIP_DST);
 514 }
 515
 516 /****************************************************************************/
 517 static int nat_callforwarding(struct sk_buff *skb, struct nf_conn *ct,
 518                               enum ip_conntrack_info ctinfo,
 519                               unsigned char **data, int dataoff,
 520                               TransportAddress *taddr, __be16 port,
 521                               struct nf_conntrack_expect *exp)
 522 {
 523         int dir = CTINFO2DIR(ctinfo);
 524         u_int16_t nated_port;
 525
 526         /* Set expectations for NAT */
 527         exp->saved_ip = exp->tuple.dst.u3.ip;
 528         exp->tuple.dst.u3.ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 529         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 530         exp->expectfn = ip_nat_callforwarding_expect;
 531         exp->dir = !dir;
 532
 533         /* Try to get same port: if not, try to change it. */
 534         for (nated_port = ntohs(port); nated_port != 0; nated_port++) {
 535                 int ret;
 536
 537                 exp->tuple.dst.u.tcp.port = htons(nated_port);
 538                 ret = nf_ct_expect_related(exp);
 539                 if (ret == 0)
 540                         break;
 541                 else if (ret != -EBUSY) {
 542                         nated_port = 0;
 543                         break;
 544                 }
 545         }
 546
 547         if (nated_port == 0) {  /* No port available */
 548                 if (net_ratelimit())
 549                         pr_notice("nf_nat_q931: out of TCP ports\n");
 550                 return 0;
 551         }
 552
 553         /* Modify signal */
 554         if (!set_h225_addr(skb, data, dataoff, taddr,
 555                            &ct->tuplehash[!dir].tuple.dst.u3,
 556                            htons(nated_port)) == 0) {
 557                 nf_ct_unexpect_related(exp);
 558                 return -1;
 559         }
 560
 561         /* Success */
 562         pr_debug("nf_nat_q931: expect Call Forwarding %pI4:%hu->%pI4:%hu\n",
 563                  &exp->tuple.src.u3.ip,
 564                  ntohs(exp->tuple.src.u.tcp.port),
 565                  &exp->tuple.dst.u3.ip,
 566                  ntohs(exp->tuple.dst.u.tcp.port));
 567
 568         return 0;
 569 }
 570
 571 /****************************************************************************/
 572 static int __init init(void)
 573 {
 574         BUG_ON(set_h245_addr_hook != NULL);
 575         BUG_ON(set_h225_addr_hook != NULL);
 576         BUG_ON(set_sig_addr_hook != NULL);
 577         BUG_ON(set_ras_addr_hook != NULL);
 578         BUG_ON(nat_rtp_rtcp_hook != NULL);
 579         BUG_ON(nat_t120_hook != NULL);
 580         BUG_ON(nat_h245_hook != NULL);
 581         BUG_ON(nat_callforwarding_hook != NULL);
 582         BUG_ON(nat_q931_hook != NULL);
 583
 584         RCU_INIT_POINTER(set_h245_addr_hook, set_h245_addr);
 585         RCU_INIT_POINTER(set_h225_addr_hook, set_h225_addr);
 586         RCU_INIT_POINTER(set_sig_addr_hook, set_sig_addr);
 587         RCU_INIT_POINTER(set_ras_addr_hook, set_ras_addr);
 588         RCU_INIT_POINTER(nat_rtp_rtcp_hook, nat_rtp_rtcp);
 589         RCU_INIT_POINTER(nat_t120_hook, nat_t120);
 590         RCU_INIT_POINTER(nat_h245_hook, nat_h245);
 591         RCU_INIT_POINTER(nat_callforwarding_hook, nat_callforwarding);
 592         RCU_INIT_POINTER(nat_q931_hook, nat_q931);
 593         return 0;
 594 }
 595
 596 /****************************************************************************/
 597 static void __exit fini(void)
 598 {
 599         RCU_INIT_POINTER(set_h245_addr_hook, NULL);
 600         RCU_INIT_POINTER(set_h225_addr_hook, NULL);
 601         RCU_INIT_POINTER(set_sig_addr_hook, NULL);
 602         RCU_INIT_POINTER(set_ras_addr_hook, NULL);
 603         RCU_INIT_POINTER(nat_rtp_rtcp_hook, NULL);
 604         RCU_INIT_POINTER(nat_t120_hook, NULL);
 605         RCU_INIT_POINTER(nat_h245_hook, NULL);
 606         RCU_INIT_POINTER(nat_callforwarding_hook, NULL);
 607         RCU_INIT_POINTER(nat_q931_hook, NULL);
 608         synchronize_rcu();
 609 }
 610
 611 /****************************************************************************/
 612 module_init(init);
 613 module_exit(fini);
 614
 615 MODULE_AUTHOR("Jing Min Zhao <zhaojingmin@users.sourceforge.net>");
 616 MODULE_DESCRIPTION("H.323 NAT helper");
 617 MODULE_LICENSE("GPL");
 618 MODULE_ALIAS("ip_nat_h323");