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