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