aboutsummaryrefslogtreecommitdiffstats
path: root/net/ipv4/netfilter/nf_nat_h323.c
blob: 7875c98072eb93fb0f555feda39e8433b9c37719 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
/*
 * H.323 extension for NAT alteration.
 *
 * Copyright (c) 2006 Jing Min Zhao <zhaojingmin@users.sourceforge.net>
 * Copyright (c) 2006-2012 Patrick McHardy <kaber@trash.net>
 *
 * This source code is licensed under General Public License version 2.
 *
 * Based on the 'brute force' H.323 NAT module by
 * Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
 */

#include <linux/module.h>
#include <linux/tcp.h>
#include <net/tcp.h>

#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <linux/netfilter/nf_conntrack_h323.h>

/****************************************************************************/
static int set_addr(struct sk_buff *skb, unsigned int protoff,
		    unsigned char **data, int dataoff,
		    unsigned int addroff, __be32 ip, __be16 port)
{
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
	struct {
		__be32 ip;
		__be16 port;
	} __attribute__ ((__packed__)) buf;
	const struct tcphdr *th;
	struct tcphdr _tcph;

	buf.ip = ip;
	buf.port = port;
	addroff += dataoff;

	if (ip_hdr(skb)->protocol == IPPROTO_TCP) {
		if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
					      protoff, addroff, sizeof(buf),
					      (char *) &buf, sizeof(buf))) {
			net_notice_ratelimited("nf_nat_h323: nf_nat_mangle_tcp_packet error\n");
			return -1;
		}

		/* Relocate data pointer */
		th = skb_header_pointer(skb, ip_hdrlen(skb),
					sizeof(_tcph), &_tcph);
		if (th == NULL)
			return -1;
		*data = skb->data + ip_hdrlen(skb) + th->doff * 4 + dataoff;
	} else {
		if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
					      protoff, addroff, sizeof(buf),
					      (char *) &buf, sizeof(buf))) {
			net_notice_ratelimited("nf_nat_h323: nf_nat_mangle_udp_packet error\n");
			return -1;
		}
		/* nf_nat_mangle_udp_packet uses skb_make_writable() to copy
		 * or pull everything in a linear buffer, so we can safely
		 * use the skb pointers now */
		*data = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr);
	}

	return 0;
}

/****************************************************************************/
static int set_h225_addr(struct sk_buff *skb, unsigned int protoff,
			 unsigned char **data, int dataoff,
			 TransportAddress *taddr,
			 union nf_inet_addr *addr, __be16 port)
{
	return set_addr(skb, protoff, data, dataoff, taddr->ipAddress.ip,
			addr->ip, port);
}

/****************************************************************************/
static int set_h245_addr(struct sk_buff *skb, unsigned protoff,
			 unsigned char **data, int dataoff,
			 H245_TransportAddress *taddr,
			 union nf_inet_addr *addr, __be16 port)
{
	return set_addr(skb, protoff, data, dataoff,
			taddr->unicastAddress.iPAddress.network,
			addr->ip, port);
}

/****************************************************************************/
static int set_sig_addr(struct sk_buff *skb, struct nf_conn *ct,
			enum ip_conntrack_info ctinfo,
			unsigned int protoff, unsigned char **data,
			TransportAddress *taddr, int count)
{
	const struct nf_ct_h323_master *info = nfct_help_data(ct);
	int dir = CTINFO2DIR(ctinfo);
	int i;
	__be16 port;
	union nf_inet_addr addr;

	for (i = 0; i < count; i++) {
		if (get_h225_addr(ct, *data, &taddr[i], &addr, &port)) {
			if (addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
			    port == info->sig_port[dir]) {
				/* GW->GK */

				/* Fix for Gnomemeeting */
				if (i > 0 &&
				    get_h225_addr(ct, *data, &taddr[0],
						  &addr, &port) &&
				    (ntohl(addr.ip) & 0xff000000) == 0x7f000000)
					i = 0;

				pr_debug("nf_nat_ras: set signal address %pI4:%hu->%pI4:%hu\n",
					 &addr.ip, port,
					 &ct->tuplehash[!dir].tuple.dst.u3.ip,
					 info->sig_port[!dir]);
				return set_h225_addr(skb, protoff, data, 0,
						     &taddr[i],
						     &ct->tuplehash[!dir].
						     tuple.dst.u3,
						     info->sig_port[!dir]);
			} else if (addr.ip == ct->tuplehash[dir].tuple.dst.u3.ip &&
				   port == info->sig_port[dir]) {
				/* GK->GW */
				pr_debug("nf_nat_ras: set signal address %pI4:%hu->%pI4:%hu\n",
					 &addr.ip, port,
					 &ct->tuplehash[!dir].tuple.src.u3.ip,
					 info->sig_port[!dir]);
				return set_h225_addr(skb, protoff, data, 0,
						     &taddr[i],
						     &ct->tuplehash[!dir].
						     tuple.src.u3,
						     info->sig_port[!dir]);
			}
		}
	}

	return 0;
}

/****************************************************************************/
static int set_ras_addr(struct sk_buff *skb, struct nf_conn *ct,
			enum ip_conntrack_info ctinfo,
			unsigned int protoff, unsigned char **data,
			TransportAddress *taddr, int count)
{
	int dir = CTINFO2DIR(ctinfo);
	int i;
	__be16 port;
	union nf_inet_addr addr;

	for (i = 0; i < count; i++) {
		if (get_h225_addr(ct, *data, &taddr[i], &addr, &port) &&
		    addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
		    port == ct->tuplehash[dir].tuple.src.u.udp.port) {
			pr_debug("nf_nat_ras: set rasAddress %pI4:%hu->%pI4:%hu\n",
				 &addr.ip, ntohs(port),
				 &ct->tuplehash[!dir].tuple.dst.u3.ip,
				 ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port));
			return set_h225_addr(skb, protoff, data, 0, &taddr[i],
					     &ct->tuplehash[!dir].tuple.dst.u3,
					     ct->tuplehash[!dir].tuple.
								dst.u.udp.port);
		}
	}

	return 0;
}

/****************************************************************************/
static int nat_rtp_rtcp(struct sk_buff *skb, struct nf_conn *ct,
			enum ip_conntrack_info ctinfo,
			unsigned int protoff, unsigned char **data, int dataoff,
			H245_TransportAddress *taddr,
			__be16 port, __be16 rtp_port,
			struct nf_conntrack_expect *rtp_exp,
			struct nf_conntrack_expect *rtcp_exp)
{
	struct nf_ct_h323_master *info = nfct_help_data(ct);
	int dir = CTINFO2DIR(ctinfo);
	int i;
	u_int16_t nated_port;

	/* Set expectations for NAT */
	rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
	rtp_exp->expectfn = nf_nat_follow_master;
	rtp_exp->dir = !dir;
	rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port;
	rtcp_exp->expectfn = nf_nat_follow_master;
	rtcp_exp->dir = !dir;

	/* Lookup existing expects */
	for (i = 0; i < H323_RTP_CHANNEL_MAX; i++) {
		if (info->rtp_port[i][dir] == rtp_port) {
			/* Expected */

			/* Use allocated ports first. This will refresh
			 * the expects */
			rtp_exp->tuple.dst.u.udp.port = info->rtp_port[i][dir];
			rtcp_exp->tuple.dst.u.udp.port =
			    htons(ntohs(info->rtp_port[i][dir]) + 1);
			break;
		} else if (info->rtp_port[i][dir] == 0) {
			/* Not expected */
			break;
		}
	}

	/* Run out of expectations */
	if (i >= H323_RTP_CHANNEL_MAX) {
		net_notice_ratelimited("nf_nat_h323: out of expectations\n");
		return 0;
	}

	/* Try to get a pair of ports. */
	for (nated_port = ntohs(rtp_exp->tuple.dst.u.udp.port);
	     nated_port != 0; nated_port += 2) {
		int ret;

		rtp_exp->tuple.dst.u.udp.port = htons(nated_port);
		ret = nf_ct_expect_related(rtp_exp);
		if (ret == 0) {
			rtcp_exp->tuple.dst.u.udp.port =
			    htons(nated_port + 1);
			ret = nf_ct_expect_related(rtcp_exp);
			if (ret == 0)
				break;
			else if (ret == -EBUSY) {
				nf_ct_unexpect_related(rtp_exp);
				continue;
			} else if (ret < 0) {
				nf_ct_unexpect_related(rtp_exp);
				nated_port = 0;
				break;
			}
		} else if (ret != -EBUSY) {
			nated_port = 0;
			break;
		}
	}

	if (nated_port == 0) {	/* No port available */
		net_notice_ratelimited("nf_nat_h323: out of RTP ports\n");
		return 0;
	}

	/* Modify signal */
	if (set_h245_addr(skb, protoff, data, dataoff, taddr,
			  &ct->tuplehash[!dir].tuple.dst.u3,
			  htons((port & htons(1)) ? nated_port + 1 :
						    nated_port))) {
		nf_ct_unexpect_related(rtp_exp);
		nf_ct_unexpect_related(rtcp_exp);
		return -1;
	}

	/* Save ports */
	info->rtp_port[i][dir] = rtp_port;
	info->rtp_port[i][!dir] = htons(nated_port);

	/* Success */
	pr_debug("nf_nat_h323: expect RTP %pI4:%hu->%pI4:%hu\n",
		 &rtp_exp->tuple.src.u3.ip,
		 ntohs(rtp_exp->tuple.src.u.udp.port),
		 &rtp_exp->tuple.dst.u3.ip,
		 ntohs(rtp_exp->tuple.dst.u.udp.port));
	pr_debug("nf_nat_h323: expect RTCP %pI4:%hu->%pI4:%hu\n",
		 &rtcp_exp->tuple.src.u3.ip,
		 ntohs(rtcp_exp->tuple.src.u.udp.port),
		 &rtcp_exp->tuple.dst.u3.ip,
		 ntohs(rtcp_exp->tuple.dst.u.udp.port));

	return 0;
}

/****************************************************************************/
static int nat_t120(struct sk_buff *skb, struct nf_conn *ct,
		    enum ip_conntrack_info ctinfo,
		    unsigned int protoff, unsigned char **data, int dataoff,
		    H245_TransportAddress *taddr, __be16 port,
		    struct nf_conntrack_expect *exp)
{
	int dir = CTINFO2DIR(ctinfo);
	u_int16_t nated_port = ntohs(port);

	/* Set expectations for NAT */
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->expectfn = nf_nat_follow_master;
	exp->dir = !dir;

	/* Try to get same port: if not, try to change it. */
	for (; nated_port != 0; nated_port++) {
		int ret;

		exp->tuple.dst.u.tcp.port = htons(nated_port);
		ret = nf_ct_expect_related(exp);
		if (ret == 0)
			break;
		else if (ret != -EBUSY) {
			nated_port = 0;
			break;
		}
	}

	if (nated_port == 0) {	/* No port available */
		net_notice_ratelimited("nf_nat_h323: out of TCP ports\n");
		return 0;
	}

	/* Modify signal */
	if (set_h245_addr(skb, protoff, data, dataoff, taddr,
			  &ct->tuplehash[!dir].tuple.dst.u3,
			  htons(nated_port)) < 0) {
		nf_ct_unexpect_related(exp);
		return -1;
	}

	pr_debug("nf_nat_h323: expect T.120 %pI4:%hu->%pI4:%hu\n",
		 &exp->tuple.src.u3.ip,
		 ntohs(exp->tuple.src.u.tcp.port),
		 &exp->tuple.dst.u3.ip,
		 ntohs(exp->tuple.dst.u.tcp.port));

	return 0;
}

/****************************************************************************/
static int nat_h245(struct sk_buff *skb, struct nf_conn *ct,
		    enum ip_conntrack_info ctinfo,
		    unsigned int protoff, unsigned char **data, int dataoff,
		    TransportAddress *taddr, __be16 port,
		    struct nf_conntrack_expect *exp)
{
	struct nf_ct_h323_master *info = nfct_help_data(ct);
	int dir = CTINFO2DIR(ctinfo);
	u_int16_t nated_port = ntohs(port);

	/* Set expectations for NAT */
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->expectfn = nf_nat_follow_master;
	exp->dir = !dir;

	/* Check existing expects */
	if (info->sig_port[dir] == port)
		nated_port = ntohs(info->sig_port[!dir]);

	/* Try to get same port: if not, try to change it. */
	for (; nated_port != 0; nated_port++) {
		int ret;

		exp->tuple.dst.u.tcp.port = htons(nated_port);
		ret = nf_ct_expect_related(exp);
		if (ret == 0)
			break;
		else if (ret != -EBUSY) {
			nated_port = 0;
			break;
		}
	}

	if (nated_port == 0) {	/* No port available */
		net_notice_ratelimited("nf_nat_q931: out of TCP ports\n");
		return 0;
	}

	/* Modify signal */
	if (set_h225_addr(skb, protoff, data, dataoff, taddr,
			  &ct->tuplehash[!dir].tuple.dst.u3,
			  htons(nated_port))) {
		nf_ct_unexpect_related(exp);
		return -1;
	}

	/* Save ports */
	info->sig_port[dir] = port;
	info->sig_port[!dir] = htons(nated_port);

	pr_debug("nf_nat_q931: expect H.245 %pI4:%hu->%pI4:%hu\n",
		 &exp->tuple.src.u3.ip,
		 ntohs(exp->tuple.src.u.tcp.port),
		 &exp->tuple.dst.u3.ip,
		 ntohs(exp->tuple.dst.u.tcp.port));

	return 0;
}

/****************************************************************************
 * This conntrack expect function replaces nf_conntrack_q931_expect()
 * which was set by nf_conntrack_h323.c.
 ****************************************************************************/
static void ip_nat_q931_expect(struct nf_conn *new,
			       struct nf_conntrack_expect *this)
{
	struct nf_nat_range2 range;

	if (this->tuple.src.u3.ip != 0) {	/* Only accept calls from GK */
		nf_nat_follow_master(new, this);
		return;
	}

	/* This must be a fresh one. */
	BUG_ON(new->status & IPS_NAT_DONE_MASK);

	/* Change src to where master sends to */
	range.flags = NF_NAT_RANGE_MAP_IPS;
	range.min_addr = range.max_addr =
	    new->tuplehash[!this->dir].tuple.src.u3;
	nf_nat_setup_info(new, &range, NF_NAT_MANIP_SRC);

	/* For DST manip, map port here to where it's expected. */
	range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
	range.min_proto = range.max_proto = this->saved_proto;
	range.min_addr = range.max_addr =
	    new->master->tuplehash[!this->dir].tuple.src.u3;
	nf_nat_setup_info(new, &range, NF_NAT_MANIP_DST);
}

/****************************************************************************/
static int nat_q931(struct sk_buff *skb, struct nf_conn *ct,
		    enum ip_conntrack_info ctinfo,
		    unsigned int protoff, unsigned char **data,
		    TransportAddress *taddr, int idx,
		    __be16 port, struct nf_conntrack_expect *exp)
{
	struct nf_ct_h323_master *info = nfct_help_data(ct);
	int dir = CTINFO2DIR(ctinfo);
	u_int16_t nated_port = ntohs(port);
	union nf_inet_addr addr;

	/* Set expectations for NAT */
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->expectfn = ip_nat_q931_expect;
	exp->dir = !dir;

	/* Check existing expects */
	if (info->sig_port[dir] == port)
		nated_port = ntohs(info->sig_port[!dir]);

	/* Try to get same port: if not, try to change it. */
	for (; nated_port != 0; nated_port++) {
		int ret;

		exp->tuple.dst.u.tcp.port = htons(nated_port);
		ret = nf_ct_expect_related(exp);
		if (ret == 0)
			break;
		else if (ret != -EBUSY) {
			nated_port = 0;
			break;
		}
	}

	if (nated_port == 0) {	/* No port available */
		net_notice_ratelimited("nf_nat_ras: out of TCP ports\n");
		return 0;
	}

	/* Modify signal */
	if (set_h225_addr(skb, protoff, data, 0, &taddr[idx],
			  &ct->tuplehash[!dir].tuple.dst.u3,
			  htons(nated_port))) {
		nf_ct_unexpect_related(exp);
		return -1;
	}

	/* Save ports */
	info->sig_port[dir] = port;
	info->sig_port[!dir] = htons(nated_port);

	/* Fix for Gnomemeeting */
	if (idx > 0 &&
	    get_h225_addr(ct, *data, &taddr[0], &addr, &port) &&
	    (ntohl(addr.ip) & 0xff000000) == 0x7f000000) {
		if (set_h225_addr(skb, protoff, data, 0, &taddr[0],
				  &ct->tuplehash[!dir].tuple.dst.u3,
				  info->sig_port[!dir])) {
			nf_ct_unexpect_related(exp);
			return -1;
		}
	}

	/* Success */
	pr_debug("nf_nat_ras: expect Q.931 %pI4:%hu->%pI4:%hu\n",
		 &exp->tuple.src.u3.ip,
		 ntohs(exp->tuple.src.u.tcp.port),
		 &exp->tuple.dst.u3.ip,
		 ntohs(exp->tuple.dst.u.tcp.port));

	return 0;
}

/****************************************************************************/
static void ip_nat_callforwarding_expect(struct nf_conn *new,
					 struct nf_conntrack_expect *this)
{
	struct nf_nat_range2 range;

	/* This must be a fresh one. */
	BUG_ON(new->status & IPS_NAT_DONE_MASK);

	/* Change src to where master sends to */
	range.flags = NF_NAT_RANGE_MAP_IPS;
	range.min_addr = range.max_addr =
	    new->tuplehash[!this->dir].tuple.src.u3;
	nf_nat_setup_info(new, &range, NF_NAT_MANIP_SRC);

	/* For DST manip, map port here to where it's expected. */
	range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
	range.min_proto = range.max_proto = this->saved_proto;
	range.min_addr = range.max_addr = this->saved_addr;
	nf_nat_setup_info(new, &range, NF_NAT_MANIP_DST);
}

/****************************************************************************/
static int nat_callforwarding(struct sk_buff *skb, struct nf_conn *ct,
			      enum ip_conntrack_info ctinfo,
			      unsigned int protoff,
			      unsigned char **data, int dataoff,
			      TransportAddress *taddr, __be16 port,
			      struct nf_conntrack_expect *exp)
{
	int dir = CTINFO2DIR(ctinfo);
	u_int16_t nated_port;

	/* Set expectations for NAT */
	exp->saved_addr = exp->tuple.dst.u3;
	exp->tuple.dst.u3.ip = ct->tuplehash[!dir].tuple.dst.u3.ip;
	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	exp->expectfn = ip_nat_callforwarding_expect;
	exp->dir = !dir;

	/* Try to get same port: if not, try to change it. */
	for (nated_port = ntohs(port); nated_port != 0; nated_port++) {
		int ret;

		exp->tuple.dst.u.tcp.port = htons(nated_port);
		ret = nf_ct_expect_related(exp);
		if (ret == 0)
			break;
		else if (ret != -EBUSY) {
			nated_port = 0;
			break;
		}
	}

	if (nated_port == 0) {	/* No port available */
		net_notice_ratelimited("nf_nat_q931: out of TCP ports\n");
		return 0;
	}

	/* Modify signal */
	if (set_h225_addr(skb, protoff, data, dataoff, taddr,
			  &ct->tuplehash[!dir].tuple.dst.u3,
			  htons(nated_port))) {
		nf_ct_unexpect_related(exp);
		return -1;
	}

	/* Success */
	pr_debug("nf_nat_q931: expect Call Forwarding %pI4:%hu->%pI4:%hu\n",
		 &exp->tuple.src.u3.ip,
		 ntohs(exp->tuple.src.u.tcp.port),
		 &exp->tuple.dst.u3.ip,
		 ntohs(exp->tuple.dst.u.tcp.port));

	return 0;
}

static struct nf_ct_helper_expectfn q931_nat = {
	.name		= "Q.931",
	.expectfn	= ip_nat_q931_expect,
};

static struct nf_ct_helper_expectfn callforwarding_nat = {
	.name		= "callforwarding",
	.expectfn	= ip_nat_callforwarding_expect,
};

/****************************************************************************/
static int __init init(void)
{
	BUG_ON(set_h245_addr_hook != NULL);
	BUG_ON(set_h225_addr_hook != NULL);
	BUG_ON(set_sig_addr_hook != NULL);
	BUG_ON(set_ras_addr_hook != NULL);
	BUG_ON(nat_rtp_rtcp_hook != NULL);
	BUG_ON(nat_t120_hook != NULL);
	BUG_ON(nat_h245_hook != NULL);
	BUG_ON(nat_callforwarding_hook != NULL);
	BUG_ON(nat_q931_hook != NULL);

	RCU_INIT_POINTER(set_h245_addr_hook, set_h245_addr);
	RCU_INIT_POINTER(set_h225_addr_hook, set_h225_addr);
	RCU_INIT_POINTER(set_sig_addr_hook, set_sig_addr);
	RCU_INIT_POINTER(set_ras_addr_hook, set_ras_addr);
	RCU_INIT_POINTER(nat_rtp_rtcp_hook, nat_rtp_rtcp);
	RCU_INIT_POINTER(nat_t120_hook, nat_t120);
	RCU_INIT_POINTER(nat_h245_hook, nat_h245);
	RCU_INIT_POINTER(nat_callforwarding_hook, nat_callforwarding);
	RCU_INIT_POINTER(nat_q931_hook, nat_q931);
	nf_ct_helper_expectfn_register(&q931_nat);
	nf_ct_helper_expectfn_register(&callforwarding_nat);
	return 0;
}

/****************************************************************************/
static void __exit fini(void)
{
	RCU_INIT_POINTER(set_h245_addr_hook, NULL);
	RCU_INIT_POINTER(set_h225_addr_hook, NULL);
	RCU_INIT_POINTER(set_sig_addr_hook, NULL);
	RCU_INIT_POINTER(set_ras_addr_hook, NULL);
	RCU_INIT_POINTER(nat_rtp_rtcp_hook, NULL);
	RCU_INIT_POINTER(nat_t120_hook, NULL);
	RCU_INIT_POINTER(nat_h245_hook, NULL);
	RCU_INIT_POINTER(nat_callforwarding_hook, NULL);
	RCU_INIT_POINTER(nat_q931_hook, NULL);
	nf_ct_helper_expectfn_unregister(&q931_nat);
	nf_ct_helper_expectfn_unregister(&callforwarding_nat);
	synchronize_rcu();
}

/****************************************************************************/
module_init(init);
module_exit(fini);

MODULE_AUTHOR("Jing Min Zhao <zhaojingmin@users.sourceforge.net>");
MODULE_DESCRIPTION("H.323 NAT helper");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NF_NAT_HELPER("h323");