release/src-rt-6.x.4708/linux/linux-2.6.36/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                 rtp_exp->tuple.dst.u.udp.port = htons(nated_port);
 226                 if (nf_ct_expect_related(rtp_exp) == 0) {
 227                         rtcp_exp->tuple.dst.u.udp.port =
 228                             htons(nated_port + 1);
 229                         if (nf_ct_expect_related(rtcp_exp) == 0)
 230                                 break;
 231                         nf_ct_unexpect_related(rtp_exp);
 232                 }
 233         }
 234
 235         if (nated_port == 0) {  /* No port available */
 236                 if (net_ratelimit())
 237                         pr_notice("nf_nat_h323: out of RTP ports\n");
 238                 return 0;
 239         }
 240
 241         /* Modify signal */
 242         if (set_h245_addr(skb, data, dataoff, taddr,
 243                           &ct->tuplehash[!dir].tuple.dst.u3,
 244                           htons((port & htons(1)) ? nated_port + 1 :
 245                                                     nated_port)) == 0) {
 246                 /* Save ports */
 247                 info->rtp_port[i][dir] = rtp_port;
 248                 info->rtp_port[i][!dir] = htons(nated_port);
 249         } else {
 250                 nf_ct_unexpect_related(rtp_exp);
 251                 nf_ct_unexpect_related(rtcp_exp);
 252                 return -1;
 253         }
 254
 255         /* Success */
 256         pr_debug("nf_nat_h323: expect RTP %pI4:%hu->%pI4:%hu\n",
 257                  &rtp_exp->tuple.src.u3.ip,
 258                  ntohs(rtp_exp->tuple.src.u.udp.port),
 259                  &rtp_exp->tuple.dst.u3.ip,
 260                  ntohs(rtp_exp->tuple.dst.u.udp.port));
 261         pr_debug("nf_nat_h323: expect RTCP %pI4:%hu->%pI4:%hu\n",
 262                  &rtcp_exp->tuple.src.u3.ip,
 263                  ntohs(rtcp_exp->tuple.src.u.udp.port),
 264                  &rtcp_exp->tuple.dst.u3.ip,
 265                  ntohs(rtcp_exp->tuple.dst.u.udp.port));
 266
 267         return 0;
 268 }
 269
 270 /****************************************************************************/
 271 static int nat_t120(struct sk_buff *skb, struct nf_conn *ct,
 272                     enum ip_conntrack_info ctinfo,
 273                     unsigned char **data, int dataoff,
 274                     H245_TransportAddress *taddr, __be16 port,
 275                     struct nf_conntrack_expect *exp)
 276 {
 277         int dir = CTINFO2DIR(ctinfo);
 278         u_int16_t nated_port = ntohs(port);
 279
 280         /* Set expectations for NAT */
 281         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 282         exp->expectfn = nf_nat_follow_master;
 283         exp->dir = !dir;
 284
 285         /* Try to get same port: if not, try to change it. */
 286         for (; nated_port != 0; nated_port++) {
 287                 exp->tuple.dst.u.tcp.port = htons(nated_port);
 288                 if (nf_ct_expect_related(exp) == 0)
 289                         break;
 290         }
 291
 292         if (nated_port == 0) {  /* No port available */
 293                 if (net_ratelimit())
 294                         pr_notice("nf_nat_h323: out of TCP ports\n");
 295                 return 0;
 296         }
 297
 298         /* Modify signal */
 299         if (set_h245_addr(skb, data, dataoff, taddr,
 300                           &ct->tuplehash[!dir].tuple.dst.u3,
 301                           htons(nated_port)) < 0) {
 302                 nf_ct_unexpect_related(exp);
 303                 return -1;
 304         }
 305
 306         pr_debug("nf_nat_h323: expect T.120 %pI4:%hu->%pI4:%hu\n",
 307                  &exp->tuple.src.u3.ip,
 308                  ntohs(exp->tuple.src.u.tcp.port),
 309                  &exp->tuple.dst.u3.ip,
 310                  ntohs(exp->tuple.dst.u.tcp.port));
 311
 312         return 0;
 313 }
 314
 315 /****************************************************************************/
 316 static int nat_h245(struct sk_buff *skb, struct nf_conn *ct,
 317                     enum ip_conntrack_info ctinfo,
 318                     unsigned char **data, int dataoff,
 319                     TransportAddress *taddr, __be16 port,
 320                     struct nf_conntrack_expect *exp)
 321 {
 322         struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
 323         int dir = CTINFO2DIR(ctinfo);
 324         u_int16_t nated_port = ntohs(port);
 325
 326         /* Set expectations for NAT */
 327         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 328         exp->expectfn = nf_nat_follow_master;
 329         exp->dir = !dir;
 330
 331         /* Check existing expects */
 332         if (info->sig_port[dir] == port)
 333                 nated_port = ntohs(info->sig_port[!dir]);
 334
 335         /* Try to get same port: if not, try to change it. */
 336         for (; nated_port != 0; nated_port++) {
 337                 exp->tuple.dst.u.tcp.port = htons(nated_port);
 338                 if (nf_ct_expect_related(exp) == 0)
 339                         break;
 340         }
 341
 342         if (nated_port == 0) {  /* No port available */
 343                 if (net_ratelimit())
 344                         pr_notice("nf_nat_q931: out of TCP ports\n");
 345                 return 0;
 346         }
 347
 348         /* Modify signal */
 349         if (set_h225_addr(skb, data, dataoff, taddr,
 350                           &ct->tuplehash[!dir].tuple.dst.u3,
 351                           htons(nated_port)) == 0) {
 352                 /* Save ports */
 353                 info->sig_port[dir] = port;
 354                 info->sig_port[!dir] = htons(nated_port);
 355         } else {
 356                 nf_ct_unexpect_related(exp);
 357                 return -1;
 358         }
 359
 360         pr_debug("nf_nat_q931: expect H.245 %pI4:%hu->%pI4:%hu\n",
 361                  &exp->tuple.src.u3.ip,
 362                  ntohs(exp->tuple.src.u.tcp.port),
 363                  &exp->tuple.dst.u3.ip,
 364                  ntohs(exp->tuple.dst.u.tcp.port));
 365
 366         return 0;
 367 }
 368
 369 /****************************************************************************
 370  * This conntrack expect function replaces nf_conntrack_q931_expect()
 371  * which was set by nf_conntrack_h323.c.
 372  ****************************************************************************/
 373 static void ip_nat_q931_expect(struct nf_conn *new,
 374                                struct nf_conntrack_expect *this)
 375 {
 376         struct nf_nat_range range;
 377
 378         if (this->tuple.src.u3.ip != 0) {       /* Only accept calls from GK */
 379                 nf_nat_follow_master(new, this);
 380                 return;
 381         }
 382
 383         /* This must be a fresh one. */
 384         BUG_ON(new->status & IPS_NAT_DONE_MASK);
 385
 386         /* Change src to where master sends to */
 387         range.flags = IP_NAT_RANGE_MAP_IPS;
 388         range.min_ip = range.max_ip = new->tuplehash[!this->dir].tuple.src.u3.ip;
 389         nf_nat_setup_info(new, &range, IP_NAT_MANIP_SRC);
 390
 391         /* For DST manip, map port here to where it's expected. */
 392         range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
 393         range.min = range.max = this->saved_proto;
 394         range.min_ip = range.max_ip =
 395             new->master->tuplehash[!this->dir].tuple.src.u3.ip;
 396         nf_nat_setup_info(new, &range, IP_NAT_MANIP_DST);
 397 }
 398
 399 /****************************************************************************/
 400 static int nat_q931(struct sk_buff *skb, struct nf_conn *ct,
 401                     enum ip_conntrack_info ctinfo,
 402                     unsigned char **data, TransportAddress *taddr, int idx,
 403                     __be16 port, struct nf_conntrack_expect *exp)
 404 {
 405         struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
 406         int dir = CTINFO2DIR(ctinfo);
 407         u_int16_t nated_port = ntohs(port);
 408         union nf_inet_addr addr;
 409
 410         /* Set expectations for NAT */
 411         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 412         exp->expectfn = ip_nat_q931_expect;
 413         exp->dir = !dir;
 414
 415         /* Check existing expects */
 416         if (info->sig_port[dir] == port)
 417                 nated_port = ntohs(info->sig_port[!dir]);
 418
 419         /* Try to get same port: if not, try to change it. */
 420         for (; nated_port != 0; nated_port++) {
 421                 exp->tuple.dst.u.tcp.port = htons(nated_port);
 422                 if (nf_ct_expect_related(exp) == 0)
 423                         break;
 424         }
 425
 426         if (nated_port == 0) {  /* No port available */
 427                 if (net_ratelimit())
 428                         pr_notice("nf_nat_ras: out of TCP ports\n");
 429                 return 0;
 430         }
 431
 432         /* Modify signal */
 433         if (set_h225_addr(skb, data, 0, &taddr[idx],
 434                           &ct->tuplehash[!dir].tuple.dst.u3,
 435                           htons(nated_port)) == 0) {
 436                 /* Save ports */
 437                 info->sig_port[dir] = port;
 438                 info->sig_port[!dir] = htons(nated_port);
 439
 440                 /* Fix for Gnomemeeting */
 441                 if (idx > 0 &&
 442                     get_h225_addr(ct, *data, &taddr[0], &addr, &port) &&
 443                     (ntohl(addr.ip) & 0xff000000) == 0x7f000000) {
 444                         set_h225_addr(skb, data, 0, &taddr[0],
 445                                       &ct->tuplehash[!dir].tuple.dst.u3,
 446                                       info->sig_port[!dir]);
 447                 }
 448         } else {
 449                 nf_ct_unexpect_related(exp);
 450                 return -1;
 451         }
 452
 453         /* Success */
 454         pr_debug("nf_nat_ras: expect Q.931 %pI4:%hu->%pI4:%hu\n",
 455                  &exp->tuple.src.u3.ip,
 456                  ntohs(exp->tuple.src.u.tcp.port),
 457                  &exp->tuple.dst.u3.ip,
 458                  ntohs(exp->tuple.dst.u.tcp.port));
 459
 460         return 0;
 461 }
 462
 463 /****************************************************************************/
 464 static void ip_nat_callforwarding_expect(struct nf_conn *new,
 465                                          struct nf_conntrack_expect *this)
 466 {
 467         struct nf_nat_range range;
 468
 469         /* This must be a fresh one. */
 470         BUG_ON(new->status & IPS_NAT_DONE_MASK);
 471
 472         /* Change src to where master sends to */
 473         range.flags = IP_NAT_RANGE_MAP_IPS;
 474         range.min_ip = range.max_ip = new->tuplehash[!this->dir].tuple.src.u3.ip;
 475         nf_nat_setup_info(new, &range, IP_NAT_MANIP_SRC);
 476
 477         /* For DST manip, map port here to where it's expected. */
 478         range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
 479         range.min = range.max = this->saved_proto;
 480         range.min_ip = range.max_ip = this->saved_ip;
 481         nf_nat_setup_info(new, &range, IP_NAT_MANIP_DST);
 482 }
 483
 484 /****************************************************************************/
 485 static int nat_callforwarding(struct sk_buff *skb, struct nf_conn *ct,
 486                               enum ip_conntrack_info ctinfo,
 487                               unsigned char **data, int dataoff,
 488                               TransportAddress *taddr, __be16 port,
 489                               struct nf_conntrack_expect *exp)
 490 {
 491         int dir = CTINFO2DIR(ctinfo);
 492         u_int16_t nated_port;
 493
 494         /* Set expectations for NAT */
 495         exp->saved_ip = exp->tuple.dst.u3.ip;
 496         exp->tuple.dst.u3.ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
 497         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 498         exp->expectfn = ip_nat_callforwarding_expect;
 499         exp->dir = !dir;
 500
 501         /* Try to get same port: if not, try to change it. */
 502         for (nated_port = ntohs(port); nated_port != 0; nated_port++) {
 503                 exp->tuple.dst.u.tcp.port = htons(nated_port);
 504                 if (nf_ct_expect_related(exp) == 0)
 505                         break;
 506         }
 507
 508         if (nated_port == 0) {  /* No port available */
 509                 if (net_ratelimit())
 510                         pr_notice("nf_nat_q931: out of TCP ports\n");
 511                 return 0;
 512         }
 513
 514         /* Modify signal */
 515         if (!set_h225_addr(skb, data, dataoff, taddr,
 516                            &ct->tuplehash[!dir].tuple.dst.u3,
 517                            htons(nated_port)) == 0) {
 518                 nf_ct_unexpect_related(exp);
 519                 return -1;
 520         }
 521
 522         /* Success */
 523         pr_debug("nf_nat_q931: expect Call Forwarding %pI4:%hu->%pI4:%hu\n",
 524                  &exp->tuple.src.u3.ip,
 525                  ntohs(exp->tuple.src.u.tcp.port),
 526                  &exp->tuple.dst.u3.ip,
 527                  ntohs(exp->tuple.dst.u.tcp.port));
 528
 529         return 0;
 530 }
 531
 532 /****************************************************************************/
 533 static int __init init(void)
 534 {
 535         BUG_ON(set_h245_addr_hook != NULL);
 536         BUG_ON(set_h225_addr_hook != NULL);
 537         BUG_ON(set_sig_addr_hook != NULL);
 538         BUG_ON(set_ras_addr_hook != NULL);
 539         BUG_ON(nat_rtp_rtcp_hook != NULL);
 540         BUG_ON(nat_t120_hook != NULL);
 541         BUG_ON(nat_h245_hook != NULL);
 542         BUG_ON(nat_callforwarding_hook != NULL);
 543         BUG_ON(nat_q931_hook != NULL);
 544
 545         rcu_assign_pointer(set_h245_addr_hook, set_h245_addr);
 546         rcu_assign_pointer(set_h225_addr_hook, set_h225_addr);
 547         rcu_assign_pointer(set_sig_addr_hook, set_sig_addr);
 548         rcu_assign_pointer(set_ras_addr_hook, set_ras_addr);
 549         rcu_assign_pointer(nat_rtp_rtcp_hook, nat_rtp_rtcp);
 550         rcu_assign_pointer(nat_t120_hook, nat_t120);
 551         rcu_assign_pointer(nat_h245_hook, nat_h245);
 552         rcu_assign_pointer(nat_callforwarding_hook, nat_callforwarding);
 553         rcu_assign_pointer(nat_q931_hook, nat_q931);
 554         return 0;
 555 }
 556
 557 /****************************************************************************/
 558 static void __exit fini(void)
 559 {
 560         rcu_assign_pointer(set_h245_addr_hook, NULL);
 561         rcu_assign_pointer(set_h225_addr_hook, NULL);
 562         rcu_assign_pointer(set_sig_addr_hook, NULL);
 563         rcu_assign_pointer(set_ras_addr_hook, NULL);
 564         rcu_assign_pointer(nat_rtp_rtcp_hook, NULL);
 565         rcu_assign_pointer(nat_t120_hook, NULL);
 566         rcu_assign_pointer(nat_h245_hook, NULL);
 567         rcu_assign_pointer(nat_callforwarding_hook, NULL);
 568         rcu_assign_pointer(nat_q931_hook, NULL);
 569         synchronize_rcu();
 570 }
 571
 572 /****************************************************************************/
 573 module_init(init);
 574 module_exit(fini);
 575
 576 MODULE_AUTHOR("Jing Min Zhao <zhaojingmin@users.sourceforge.net>");
 577 MODULE_DESCRIPTION("H.323 NAT helper");
 578 MODULE_LICENSE("GPL");
 579 MODULE_ALIAS("ip_nat_h323");