netfilter: nf_nat: better error handling of nf_ct_expect_related() in helpers
[linux-2.6.git] / 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_assign_pointer(set_h245_addr_hook, set_h245_addr);
585         rcu_assign_pointer(set_h225_addr_hook, set_h225_addr);
586         rcu_assign_pointer(set_sig_addr_hook, set_sig_addr);
587         rcu_assign_pointer(set_ras_addr_hook, set_ras_addr);
588         rcu_assign_pointer(nat_rtp_rtcp_hook, nat_rtp_rtcp);
589         rcu_assign_pointer(nat_t120_hook, nat_t120);
590         rcu_assign_pointer(nat_h245_hook, nat_h245);
591         rcu_assign_pointer(nat_callforwarding_hook, nat_callforwarding);
592         rcu_assign_pointer(nat_q931_hook, nat_q931);
593         return 0;
594 }
595
596 /****************************************************************************/
597 static void __exit fini(void)
598 {
599         rcu_assign_pointer(set_h245_addr_hook, NULL);
600         rcu_assign_pointer(set_h225_addr_hook, NULL);
601         rcu_assign_pointer(set_sig_addr_hook, NULL);
602         rcu_assign_pointer(set_ras_addr_hook, NULL);
603         rcu_assign_pointer(nat_rtp_rtcp_hook, NULL);
604         rcu_assign_pointer(nat_t120_hook, NULL);
605         rcu_assign_pointer(nat_h245_hook, NULL);
606         rcu_assign_pointer(nat_callforwarding_hook, NULL);
607         rcu_assign_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");