summaryrefslogtreecommitdiff
path: root/package/network/utils/xtables-addons/patches-1.x/100-add-rtsp-conntrack.patch
blob: 34cdc8c17cc959d3b15dd26600a0f027317ed722 (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
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
--- /dev/null
+++ b/extensions/rtsp/Kbuild
@@ -0,0 +1,4 @@
+# -*- Makefile -*-
+
+obj-m += nf_nat_rtsp.o
+obj-m += nf_conntrack_rtsp.o
--- /dev/null
+++ b/extensions/rtsp/netfilter_helpers.h
@@ -0,0 +1,133 @@
+/*
+ * Helpers for netfiler modules.  This file provides implementations for basic
+ * functions such as strncasecmp(), etc.
+ *
+ * gcc will warn for defined but unused functions, so we only include the
+ * functions requested.  The following macros are used:
+ *   NF_NEED_STRNCASECMP        nf_strncasecmp()
+ *   NF_NEED_STRTOU16           nf_strtou16()
+ *   NF_NEED_STRTOU32           nf_strtou32()
+ */
+#ifndef _NETFILTER_HELPERS_H
+#define _NETFILTER_HELPERS_H
+
+/* Only include these functions for kernel code. */
+#ifdef __KERNEL__
+
+#include <linux/ctype.h>
+#define iseol(c) ( (c) == '\r' || (c) == '\n' )
+
+/*
+ * The standard strncasecmp()
+ */
+#ifdef NF_NEED_STRNCASECMP
+static int
+nf_strncasecmp(const char* s1, const char* s2, u_int32_t len)
+{
+    if (s1 == NULL || s2 == NULL)
+    {
+        if (s1 == NULL && s2 == NULL)
+        {
+            return 0;
+        }
+        return (s1 == NULL) ? -1 : 1;
+    }
+    while (len > 0 && tolower(*s1) == tolower(*s2))
+    {
+        len--;
+        s1++;
+        s2++;
+    }
+    return ( (len == 0) ? 0 : (tolower(*s1) - tolower(*s2)) );
+}
+#endif /* NF_NEED_STRNCASECMP */
+
+/*
+ * Parse a string containing a 16-bit unsigned integer.
+ * Returns the number of chars used, or zero if no number is found.
+ */
+#ifdef NF_NEED_STRTOU16
+static int
+nf_strtou16(const char* pbuf, u_int16_t* pval)
+{
+    int n = 0;
+
+    *pval = 0;
+    while (isdigit(pbuf[n]))
+    {
+        *pval = (*pval * 10) + (pbuf[n] - '0');
+        n++;
+    }
+
+    return n;
+}
+#endif /* NF_NEED_STRTOU16 */
+
+/*
+ * Parse a string containing a 32-bit unsigned integer.
+ * Returns the number of chars used, or zero if no number is found.
+ */
+#ifdef NF_NEED_STRTOU32
+static int
+nf_strtou32(const char* pbuf, u_int32_t* pval)
+{
+    int n = 0;
+
+    *pval = 0;
+    while (pbuf[n] >= '0' && pbuf[n] <= '9')
+    {
+        *pval = (*pval * 10) + (pbuf[n] - '0');
+        n++;
+    }
+
+    return n;
+}
+#endif /* NF_NEED_STRTOU32 */
+
+/*
+ * Given a buffer and length, advance to the next line and mark the current
+ * line.
+ */
+#ifdef NF_NEED_NEXTLINE
+static int
+nf_nextline(char* p, uint len, uint* poff, uint* plineoff, uint* plinelen)
+{
+    uint    off = *poff;
+    uint    physlen = 0;
+
+    if (off >= len)
+    {
+        return 0;
+    }
+
+    while (p[off] != '\n')
+    {
+        if (len-off <= 1)
+        {
+            return 0;
+        }
+
+        physlen++;
+        off++;
+    }
+
+    /* if we saw a crlf, physlen needs adjusted */
+    if (physlen > 0 && p[off] == '\n' && p[off-1] == '\r')
+    {
+        physlen--;
+    }
+
+    /* advance past the newline */
+    off++;
+
+    *plineoff = *poff;
+    *plinelen = physlen;
+    *poff = off;
+
+    return 1;
+}
+#endif /* NF_NEED_NEXTLINE */
+
+#endif /* __KERNEL__ */
+
+#endif /* _NETFILTER_HELPERS_H */
--- /dev/null
+++ b/extensions/rtsp/netfilter_mime.h
@@ -0,0 +1,89 @@
+/*
+ * MIME functions for netfilter modules.  This file provides implementations
+ * for basic MIME parsing.  MIME headers are used in many protocols, such as
+ * HTTP, RTSP, SIP, etc.
+ *
+ * gcc will warn for defined but unused functions, so we only include the
+ * functions requested.  The following macros are used:
+ *   NF_NEED_MIME_NEXTLINE      nf_mime_nextline()
+ */
+#ifndef _NETFILTER_MIME_H
+#define _NETFILTER_MIME_H
+
+/* Only include these functions for kernel code. */
+#ifdef __KERNEL__
+
+#include <linux/ctype.h>
+
+/*
+ * Given a buffer and length, advance to the next line and mark the current
+ * line.  If the current line is empty, *plinelen will be set to zero.  If
+ * not, it will be set to the actual line length (including CRLF).
+ *
+ * 'line' in this context means logical line (includes LWS continuations).
+ * Returns 1 on success, 0 on failure.
+ */
+#ifdef NF_NEED_MIME_NEXTLINE
+static int
+nf_mime_nextline(char* p, uint len, uint* poff, uint* plineoff, uint* plinelen)
+{
+    uint    off = *poff;
+    uint    physlen = 0;
+    int     is_first_line = 1;
+
+    if (off >= len)
+    {
+        return 0;
+    }
+
+    do
+    {
+        while (p[off] != '\n')
+        {
+            if (len-off <= 1)
+            {
+                return 0;
+            }
+
+            physlen++;
+            off++;
+        }
+
+        /* if we saw a crlf, physlen needs adjusted */
+        if (physlen > 0 && p[off] == '\n' && p[off-1] == '\r')
+        {
+            physlen--;
+        }
+
+        /* advance past the newline */
+        off++;
+
+        /* check for an empty line */
+        if (physlen == 0)
+        {
+            break;
+        }
+
+        /* check for colon on the first physical line */
+        if (is_first_line)
+        {
+            is_first_line = 0;
+            if (memchr(p+(*poff), ':', physlen) == NULL)
+            {
+                return 0;
+            }
+        }
+    }
+    while (p[off] == ' ' || p[off] == '\t');
+
+    *plineoff = *poff;
+    *plinelen = (physlen == 0) ? 0 : (off - *poff);
+    *poff = off;
+
+    return 1;
+}
+#endif /* NF_NEED_MIME_NEXTLINE */
+
+#endif /* __KERNEL__ */
+
+#endif /* _NETFILTER_MIME_H */
--- /dev/null
+++ b/extensions/rtsp/nf_conntrack_rtsp.c
@@ -0,0 +1,519 @@
+/*
+ * RTSP extension for IP connection tracking
+ * (C) 2003 by Tom Marshall <tmarshall at real.com>
+ * based on ip_conntrack_irc.c
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ *
+ * Module load syntax:
+ *   insmod nf_conntrack_rtsp.o ports=port1,port2,...port<MAX_PORTS>
+ *                              max_outstanding=n setup_timeout=secs
+ *
+ * If no ports are specified, the default will be port 554.
+ *
+ * With max_outstanding you can define the maximum number of not yet
+ * answered SETUP requests per RTSP session (default 8).
+ * With setup_timeout you can specify how long the system waits for
+ * an expected data channel (default 300 seconds).
+ *
+ * 2005-02-13: Harald Welte <laforge at netfilter.org>
+ * 	- port to 2.6
+ * 	- update to recent post-2.6.11 api changes
+ * 2006-09-14: Steven Van Acker <deepstar at singularity.be>
+ *      - removed calls to NAT code from conntrack helper: NAT no longer needed to use rtsp-conntrack
+ * 2007-04-18: Michael Guntsche <mike at it-loops.com>
+ * 			- Port to new NF API
+ */
+
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/ip.h>
+#include <linux/inet.h>
+#include <net/tcp.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include "nf_conntrack_rtsp.h"
+
+#define NF_NEED_STRNCASECMP
+#define NF_NEED_STRTOU16
+#define NF_NEED_STRTOU32
+#define NF_NEED_NEXTLINE
+#include "netfilter_helpers.h"
+#define NF_NEED_MIME_NEXTLINE
+#include "netfilter_mime.h"
+
+#include <linux/ctype.h>
+#define MAX_SIMUL_SETUP 8 /* XXX: use max_outstanding */
+
+#define MAX_PORTS 8
+static int ports[MAX_PORTS];
+static int num_ports = 0;
+static int max_outstanding = 8;
+static unsigned int setup_timeout = 300;
+
+MODULE_AUTHOR("Tom Marshall <tmarshall at real.com>");
+MODULE_DESCRIPTION("RTSP connection tracking module");
+MODULE_LICENSE("GPL");
+module_param_array(ports, int, &num_ports, 0400);
+MODULE_PARM_DESC(ports, "port numbers of RTSP servers");
+module_param(max_outstanding, int, 0400);
+MODULE_PARM_DESC(max_outstanding, "max number of outstanding SETUP requests per RTSP session");
+module_param(setup_timeout, int, 0400);
+MODULE_PARM_DESC(setup_timeout, "timeout on for unestablished data channels");
+
+static char *rtsp_buffer;
+static DEFINE_SPINLOCK(rtsp_buffer_lock);
+
+static struct nf_conntrack_expect_policy rtsp_exp_policy; 
+
+unsigned int (*nf_nat_rtsp_hook)(struct sk_buff *skb,
+				 enum ip_conntrack_info ctinfo,
+				 unsigned int matchoff, unsigned int matchlen,struct ip_ct_rtsp_expect* prtspexp,
+				 struct nf_conntrack_expect *exp);
+void (*nf_nat_rtsp_hook_expectfn)(struct nf_conn *ct, struct nf_conntrack_expect *exp);
+
+EXPORT_SYMBOL_GPL(nf_nat_rtsp_hook);
+
+/*
+ * Max mappings we will allow for one RTSP connection (for RTP, the number
+ * of allocated ports is twice this value).  Note that SMIL burns a lot of
+ * ports so keep this reasonably high.  If this is too low, you will see a
+ * lot of "no free client map entries" messages.
+ */
+#define MAX_PORT_MAPS 16
+
+/*** default port list was here in the masq code: 554, 3030, 4040 ***/
+
+#define SKIP_WSPACE(ptr,len,off) while(off < len && isspace(*(ptr+off))) { off++; }
+
+/*
+ * Parse an RTSP packet.
+ *
+ * Returns zero if parsing failed.
+ *
+ * Parameters:
+ *  IN      ptcp        tcp data pointer
+ *  IN      tcplen      tcp data len
+ *  IN/OUT  ptcpoff     points to current tcp offset
+ *  OUT     phdrsoff    set to offset of rtsp headers
+ *  OUT     phdrslen    set to length of rtsp headers
+ *  OUT     pcseqoff    set to offset of CSeq header
+ *  OUT     pcseqlen    set to length of CSeq header
+ */
+static int
+rtsp_parse_message(char* ptcp, uint tcplen, uint* ptcpoff,
+                   uint* phdrsoff, uint* phdrslen,
+                   uint* pcseqoff, uint* pcseqlen,
+                   uint* transoff, uint* translen)
+{
+	uint    entitylen = 0;
+	uint    lineoff;
+	uint    linelen;
+	
+	if (!nf_nextline(ptcp, tcplen, ptcpoff, &lineoff, &linelen))
+		return 0;
+	
+	*phdrsoff = *ptcpoff;
+	while (nf_mime_nextline(ptcp, tcplen, ptcpoff, &lineoff, &linelen)) {
+		if (linelen == 0) {
+			if (entitylen > 0)
+				*ptcpoff += min(entitylen, tcplen - *ptcpoff);
+			break;
+		}
+		if (lineoff+linelen > tcplen) {
+			pr_info("!! overrun !!\n");
+			break;
+		}
+		
+		if (nf_strncasecmp(ptcp+lineoff, "CSeq:", 5) == 0) {
+			*pcseqoff = lineoff;
+			*pcseqlen = linelen;
+		} 
+
+		if (nf_strncasecmp(ptcp+lineoff, "Transport:", 10) == 0) {
+			*transoff = lineoff;
+			*translen = linelen;
+		}
+		
+		if (nf_strncasecmp(ptcp+lineoff, "Content-Length:", 15) == 0) {
+			uint off = lineoff+15;
+			SKIP_WSPACE(ptcp+lineoff, linelen, off);
+			nf_strtou32(ptcp+off, &entitylen);
+		}
+	}
+	*phdrslen = (*ptcpoff) - (*phdrsoff);
+	
+	return 1;
+}
+
+/*
+ * Find lo/hi client ports (if any) in transport header
+ * In:
+ *   ptcp, tcplen = packet
+ *   tranoff, tranlen = buffer to search
+ *
+ * Out:
+ *   pport_lo, pport_hi = lo/hi ports (host endian)
+ *
+ * Returns nonzero if any client ports found
+ *
+ * Note: it is valid (and expected) for the client to request multiple
+ * transports, so we need to parse the entire line.
+ */
+static int
+rtsp_parse_transport(char* ptran, uint tranlen,
+                     struct ip_ct_rtsp_expect* prtspexp)
+{
+	int     rc = 0;
+	uint    off = 0;
+	
+	if (tranlen < 10 || !iseol(ptran[tranlen-1]) ||
+	    nf_strncasecmp(ptran, "Transport:", 10) != 0) {
+		pr_info("sanity check failed\n");
+		return 0;
+	}
+	
+	pr_debug("tran='%.*s'\n", (int)tranlen, ptran);
+	off += 10;
+	SKIP_WSPACE(ptran, tranlen, off);
+	
+	/* Transport: tran;field;field=val,tran;field;field=val,... */
+	while (off < tranlen) {
+		const char* pparamend;
+		uint        nextparamoff;
+		
+		pparamend = memchr(ptran+off, ',', tranlen-off);
+		pparamend = (pparamend == NULL) ? ptran+tranlen : pparamend+1;
+		nextparamoff = pparamend-ptran;
+		
+		while (off < nextparamoff) {
+			const char* pfieldend;
+			uint        nextfieldoff;
+			
+			pfieldend = memchr(ptran+off, ';', nextparamoff-off);
+			nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran+1;
+		   
+			if (strncmp(ptran+off, "client_port=", 12) == 0) {
+				u_int16_t   port;
+				uint        numlen;
+		    
+				off += 12;
+				numlen = nf_strtou16(ptran+off, &port);
+				off += numlen;
+				if (prtspexp->loport != 0 && prtspexp->loport != port)
+					pr_debug("multiple ports found, port %hu ignored\n", port);
+				else {
+					pr_debug("lo port found : %hu\n", port);
+					prtspexp->loport = prtspexp->hiport = port;
+					if (ptran[off] == '-') {
+						off++;
+						numlen = nf_strtou16(ptran+off, &port);
+						off += numlen;
+						prtspexp->pbtype = pb_range;
+						prtspexp->hiport = port;
+						
+						// If we have a range, assume rtp:
+						// loport must be even, hiport must be loport+1
+						if ((prtspexp->loport & 0x0001) != 0 ||
+						    prtspexp->hiport != prtspexp->loport+1) {
+							pr_debug("incorrect range: %hu-%hu, correcting\n",
+							       prtspexp->loport, prtspexp->hiport);
+							prtspexp->loport &= 0xfffe;
+							prtspexp->hiport = prtspexp->loport+1;
+						}
+					} else if (ptran[off] == '/') {
+						off++;
+						numlen = nf_strtou16(ptran+off, &port);
+						off += numlen;
+						prtspexp->pbtype = pb_discon;
+						prtspexp->hiport = port;
+					}
+					rc = 1;
+				}
+			}
+			
+			/*
+			 * Note we don't look for the destination parameter here.
+			 * If we are using NAT, the NAT module will handle it.  If not,
+			 * and the client is sending packets elsewhere, the expectation
+			 * will quietly time out.
+			 */
+			
+			off = nextfieldoff;
+		}
+		
+		off = nextparamoff;
+	}
+	
+	return rc;
+}
+
+void expected(struct nf_conn *ct, struct nf_conntrack_expect *exp)
+{
+		typeof(nf_nat_rtsp_hook_expectfn) nf_nat_rtsp_expectfn;
+		nf_nat_rtsp_expectfn = rcu_dereference(nf_nat_rtsp_hook_expectfn);
+    if(nf_nat_rtsp_expectfn && ct->master->status & IPS_NAT_MASK) {
+        nf_nat_rtsp_expectfn(ct,exp);
+    }
+}
+
+/*** conntrack functions ***/
+
+/* outbound packet: client->server */
+
+static inline int
+help_out(struct sk_buff *skb, unsigned char *rb_ptr, unsigned int datalen,
+                struct nf_conn *ct, enum ip_conntrack_info ctinfo)
+{
+	struct ip_ct_rtsp_expect expinfo;
+	
+	int dir = CTINFO2DIR(ctinfo);   /* = IP_CT_DIR_ORIGINAL */
+	//struct  tcphdr* tcph = (void*)iph + iph->ihl * 4;
+	//uint    tcplen = pktlen - iph->ihl * 4;
+	char*   pdata = rb_ptr;
+	//uint    datalen = tcplen - tcph->doff * 4;
+	uint    dataoff = 0;
+	int ret = NF_ACCEPT;
+	
+	struct nf_conntrack_expect *exp;
+	
+	__be16 be_loport;
+	
+	typeof(nf_nat_rtsp_hook) nf_nat_rtsp;
+
+	memset(&expinfo, 0, sizeof(expinfo));
+	
+	while (dataoff < datalen) {
+		uint    cmdoff = dataoff;
+		uint    hdrsoff = 0;
+		uint    hdrslen = 0;
+		uint    cseqoff = 0;
+		uint    cseqlen = 0;
+		uint    transoff = 0;
+		uint    translen = 0;
+		uint    off;
+		
+		if (!rtsp_parse_message(pdata, datalen, &dataoff,
+					&hdrsoff, &hdrslen,
+					&cseqoff, &cseqlen,
+					&transoff, &translen))
+			break;      /* not a valid message */
+		
+		if (strncmp(pdata+cmdoff, "SETUP ", 6) != 0)
+			continue;   /* not a SETUP message */
+		pr_debug("found a setup message\n");
+
+		off = 0;
+		if(translen) {
+			rtsp_parse_transport(pdata+transoff, translen, &expinfo);
+		}
+
+		if (expinfo.loport == 0) {
+			pr_debug("no udp transports found\n");
+			continue;   /* no udp transports found */
+		}
+
+		pr_debug("udp transport found, ports=(%d,%hu,%hu)\n",
+		       (int)expinfo.pbtype, expinfo.loport, expinfo.hiport);
+
+		exp = nf_ct_expect_alloc(ct);
+		if (!exp) {
+			ret = NF_DROP;
+			goto out;
+		}
+
+		be_loport = htons(expinfo.loport);
+
+		nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct),
+			&ct->tuplehash[!dir].tuple.src.u3, &ct->tuplehash[!dir].tuple.dst.u3,
+			IPPROTO_UDP, NULL, &be_loport); 
+
+		exp->master = ct;
+
+		exp->expectfn = expected;
+		exp->flags = 0;
+
+		if (expinfo.pbtype == pb_range) {
+			pr_debug("Changing expectation mask to handle multiple ports\n");
+			//exp->mask.dst.u.udp.port  = 0xfffe;
+		}
+
+		pr_debug("expect_related %pI4:%u-%pI4:%u\n",
+		       &exp->tuple.src.u3.ip,
+		       ntohs(exp->tuple.src.u.udp.port),
+		       &exp->tuple.dst.u3.ip,
+		       ntohs(exp->tuple.dst.u.udp.port));
+
+		nf_nat_rtsp = rcu_dereference(nf_nat_rtsp_hook);
+		if (nf_nat_rtsp && ct->status & IPS_NAT_MASK)
+			/* pass the request off to the nat helper */
+			ret = nf_nat_rtsp(skb, ctinfo, hdrsoff, hdrslen, &expinfo, exp);
+		else if (nf_ct_expect_related(exp) != 0) {
+			pr_info("nf_conntrack_expect_related failed\n");
+			ret  = NF_DROP;
+		}
+		nf_ct_expect_put(exp);
+		goto out;
+	}
+out:
+
+	return ret;
+}
+
+
+static inline int
+help_in(struct sk_buff *skb, size_t pktlen,
+ struct nf_conn* ct, enum ip_conntrack_info ctinfo)
+{
+ return NF_ACCEPT;
+}
+
+static int help(struct sk_buff *skb, unsigned int protoff,
+		struct nf_conn *ct, enum ip_conntrack_info ctinfo) 
+{
+	struct tcphdr _tcph, *th;
+	unsigned int dataoff, datalen;
+	char *rb_ptr;
+	int ret = NF_DROP;
+
+	/* Until there's been traffic both ways, don't look in packets. */
+	if (ctinfo != IP_CT_ESTABLISHED && 
+	    ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
+		pr_debug("conntrackinfo = %u\n", ctinfo);
+		return NF_ACCEPT;
+	} 
+
+	/* Not whole TCP header? */
+	th = skb_header_pointer(skb,protoff, sizeof(_tcph), &_tcph);
+
+	if (!th)
+		return NF_ACCEPT;
+   
+	/* No data ? */
+	dataoff = protoff + th->doff*4;
+	datalen = skb->len - dataoff;
+	if (dataoff >= skb->len)
+		return NF_ACCEPT;
+
+	spin_lock_bh(&rtsp_buffer_lock);
+	rb_ptr = skb_header_pointer(skb, dataoff,
+				    skb->len - dataoff, rtsp_buffer);
+	BUG_ON(rb_ptr == NULL);
+
+#if 0
+	/* Checksum invalid?  Ignore. */
+	/* FIXME: Source route IP option packets --RR */
+	if (tcp_v4_check(tcph, tcplen, iph->saddr, iph->daddr,
+			 csum_partial((char*)tcph, tcplen, 0)))
+	{
+		DEBUGP("bad csum: %p %u %u.%u.%u.%u %u.%u.%u.%u\n",
+		       tcph, tcplen, NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
+		return NF_ACCEPT;
+	}
+#endif
+
+	switch (CTINFO2DIR(ctinfo)) {
+	case IP_CT_DIR_ORIGINAL:
+		ret = help_out(skb, rb_ptr, datalen, ct, ctinfo);
+		break;
+	case IP_CT_DIR_REPLY:
+		pr_debug("IP_CT_DIR_REPLY\n");
+		/* inbound packet: server->client */
+		ret = NF_ACCEPT;
+		break;
+	}
+
+	spin_unlock_bh(&rtsp_buffer_lock);
+
+	return ret;
+}
+
+static struct nf_conntrack_helper rtsp_helpers[MAX_PORTS];
+static char rtsp_names[MAX_PORTS][10];
+
+/* This function is intentionally _NOT_ defined as __exit */
+static void
+fini(void)
+{
+	int i;
+	for (i = 0; i < num_ports; i++) {
+		pr_debug("unregistering port %d\n", ports[i]);
+		nf_conntrack_helper_unregister(&rtsp_helpers[i]);
+	}
+	kfree(rtsp_buffer);
+}
+
+static int __init
+init(void)
+{
+	int i, ret;
+	struct nf_conntrack_helper *hlpr;
+	char *tmpname;
+
+	printk("nf_conntrack_rtsp v" IP_NF_RTSP_VERSION " loading\n");
+
+	if (max_outstanding < 1) {
+		printk("nf_conntrack_rtsp: max_outstanding must be a positive integer\n");
+		return -EBUSY;
+	}
+	if (setup_timeout < 0) {
+		printk("nf_conntrack_rtsp: setup_timeout must be a positive integer\n");
+		return -EBUSY;
+	}
+
+  rtsp_exp_policy.max_expected = max_outstanding;
+  rtsp_exp_policy.timeout = setup_timeout;
+	
+	rtsp_buffer = kmalloc(65536, GFP_KERNEL);
+	if (!rtsp_buffer) 
+		return -ENOMEM;
+
+	/* If no port given, default to standard rtsp port */
+	if (ports[0] == 0) {
+		ports[0] = RTSP_PORT;
+	}
+
+	for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
+		hlpr = &rtsp_helpers[i];
+		memset(hlpr, 0, sizeof(struct nf_conntrack_helper));
+		hlpr->tuple.src.l3num = AF_INET;
+		hlpr->tuple.src.u.tcp.port = htons(ports[i]);
+		hlpr->tuple.dst.protonum = IPPROTO_TCP;
+		//hlpr->mask.src.u.tcp.port = 0xFFFF;
+		//hlpr->mask.dst.protonum = 0xFF;
+		hlpr->expect_policy = &rtsp_exp_policy;
+		hlpr->me = THIS_MODULE;
+		hlpr->help = help;
+
+		tmpname = &rtsp_names[i][0];
+		if (ports[i] == RTSP_PORT) {
+			sprintf(tmpname, "rtsp");
+		} else {
+			sprintf(tmpname, "rtsp-%d", i);
+		}
+		hlpr->name = tmpname;
+
+		pr_debug("port #%d: %d\n", i, ports[i]);
+
+		ret = nf_conntrack_helper_register(hlpr);
+
+		if (ret) {
+			printk("nf_conntrack_rtsp: ERROR registering port %d\n", ports[i]);
+			fini();
+			return -EBUSY;
+		}
+		num_ports++;
+	}
+	return 0;
+}
+
+module_init(init);
+module_exit(fini);
+
+EXPORT_SYMBOL(nf_nat_rtsp_hook_expectfn);
+
--- /dev/null
+++ b/extensions/rtsp/nf_conntrack_rtsp.h
@@ -0,0 +1,63 @@
+/*
+ * RTSP extension for IP connection tracking.
+ * (C) 2003 by Tom Marshall <tmarshall at real.com>
+ * based on ip_conntrack_irc.h
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+#ifndef _IP_CONNTRACK_RTSP_H
+#define _IP_CONNTRACK_RTSP_H
+
+//#define IP_NF_RTSP_DEBUG 1
+#define IP_NF_RTSP_VERSION "0.6.21"
+
+#ifdef __KERNEL__
+/* port block types */
+typedef enum {
+    pb_single,  /* client_port=x */
+    pb_range,   /* client_port=x-y */
+    pb_discon   /* client_port=x/y (rtspbis) */
+} portblock_t;
+
+/* We record seq number and length of rtsp headers here, all in host order. */
+
+/*
+ * This structure is per expected connection.  It is a member of struct
+ * ip_conntrack_expect.  The TCP SEQ for the conntrack expect is stored
+ * there and we are expected to only store the length of the data which
+ * needs replaced.  If a packet contains multiple RTSP messages, we create
+ * one expected connection per message.
+ *
+ * We use these variables to mark the entire header block.  This may seem
+ * like overkill, but the nature of RTSP requires it.  A header may appear
+ * multiple times in a message.  We must treat two Transport headers the
+ * same as one Transport header with two entries.
+ */
+struct ip_ct_rtsp_expect
+{
+    u_int32_t   len;        /* length of header block */
+    portblock_t pbtype;     /* Type of port block that was requested */
+    u_int16_t   loport;     /* Port that was requested, low or first */
+    u_int16_t   hiport;     /* Port that was requested, high or second */
+#if 0
+    uint        method;     /* RTSP method */
+    uint        cseq;       /* CSeq from request */
+#endif
+};
+
+extern unsigned int (*nf_nat_rtsp_hook)(struct sk_buff *skb,
+				 enum ip_conntrack_info ctinfo,
+				 unsigned int matchoff, unsigned int matchlen,
+				 struct ip_ct_rtsp_expect *prtspexp,
+				 struct nf_conntrack_expect *exp);
+
+extern void (*nf_nat_rtsp_hook_expectfn)(struct nf_conn *ct, struct nf_conntrack_expect *exp);
+
+#define RTSP_PORT   554
+
+#endif /* __KERNEL__ */
+
+#endif /* _IP_CONNTRACK_RTSP_H */
--- /dev/null
+++ b/extensions/rtsp/nf_nat_rtsp.c
@@ -0,0 +1,491 @@
+/*
+ * RTSP extension for TCP NAT alteration
+ * (C) 2003 by Tom Marshall <tmarshall at real.com>
+ * based on ip_nat_irc.c
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ *
+ * Module load syntax:
+ *      insmod nf_nat_rtsp.o ports=port1,port2,...port<MAX_PORTS>
+ *                           stunaddr=<address>
+ *                           destaction=[auto|strip|none]
+ *
+ * If no ports are specified, the default will be port 554 only.
+ *
+ * stunaddr specifies the address used to detect that a client is using STUN.
+ * If this address is seen in the destination parameter, it is assumed that
+ * the client has already punched a UDP hole in the firewall, so we don't
+ * mangle the client_port.  If none is specified, it is autodetected.  It
+ * only needs to be set if you have multiple levels of NAT.  It should be
+ * set to the external address that the STUN clients detect.  Note that in
+ * this case, it will not be possible for clients to use UDP with servers
+ * between the NATs.
+ *
+ * If no destaction is specified, auto is used.
+ *   destaction=auto:  strip destination parameter if it is not stunaddr.
+ *   destaction=strip: always strip destination parameter (not recommended).
+ *   destaction=none:  do not touch destination parameter (not recommended).
+ */
+
+#include <linux/module.h>
+#include <net/tcp.h>
+#include <net/netfilter/nf_nat_helper.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include "nf_conntrack_rtsp.h"
+#include <net/netfilter/nf_conntrack_expect.h>
+
+#include <linux/inet.h>
+#include <linux/ctype.h>
+#define NF_NEED_STRNCASECMP
+#define NF_NEED_STRTOU16
+#include "netfilter_helpers.h"
+#define NF_NEED_MIME_NEXTLINE
+#include "netfilter_mime.h"
+
+#include "../compat_xtables.h"
+
+#define MAX_PORTS       8
+#define DSTACT_AUTO     0
+#define DSTACT_STRIP    1
+#define DSTACT_NONE     2
+
+static char*    stunaddr = NULL;
+static char*    destaction = NULL;
+
+static u_int32_t extip = 0;
+static int       dstact = 0;
+
+MODULE_AUTHOR("Tom Marshall <tmarshall at real.com>");
+MODULE_DESCRIPTION("RTSP network address translation module");
+MODULE_LICENSE("GPL");
+module_param(stunaddr, charp, 0644);
+MODULE_PARM_DESC(stunaddr, "Address for detecting STUN");
+module_param(destaction, charp, 0644);
+MODULE_PARM_DESC(destaction, "Action for destination parameter (auto/strip/none)");
+
+#define SKIP_WSPACE(ptr,len,off) while(off < len && isspace(*(ptr+off))) { off++; }
+
+/*** helper functions ***/
+
+static void
+get_skb_tcpdata(struct sk_buff* skb, char** pptcpdata, uint* ptcpdatalen)
+{
+    struct iphdr*   iph  = ip_hdr(skb);
+    struct tcphdr*  tcph = (void *)iph + ip_hdrlen(skb);
+
+    *pptcpdata = (char*)tcph +  tcph->doff*4;
+    *ptcpdatalen = ((char*)skb_transport_header(skb) + skb->len) - *pptcpdata;
+}
+
+/*** nat functions ***/
+
+/*
+ * Mangle the "Transport:" header:
+ *   - Replace all occurences of "client_port=<spec>"
+ *   - Handle destination parameter
+ *
+ * In:
+ *   ct, ctinfo = conntrack context
+ *   skb        = packet
+ *   tranoff    = Transport header offset from TCP data
+ *   tranlen    = Transport header length (incl. CRLF)
+ *   rport_lo   = replacement low  port (host endian)
+ *   rport_hi   = replacement high port (host endian)
+ *
+ * Returns packet size difference.
+ *
+ * Assumes that a complete transport header is present, ending with CR or LF
+ */
+static int
+rtsp_mangle_tran(enum ip_conntrack_info ctinfo,
+                 struct nf_conntrack_expect* exp,
+								 struct ip_ct_rtsp_expect* prtspexp,
+                 struct sk_buff* skb, uint tranoff, uint tranlen)
+{
+    char*       ptcp;
+    uint        tcplen;
+    char*       ptran;
+    char        rbuf1[16];      /* Replacement buffer (one port) */
+    uint        rbuf1len;       /* Replacement len (one port) */
+    char        rbufa[16];      /* Replacement buffer (all ports) */
+    uint        rbufalen;       /* Replacement len (all ports) */
+    u_int32_t   newip;
+    u_int16_t   loport, hiport;
+    uint        off = 0;
+    uint        diff;           /* Number of bytes we removed */
+
+    struct nf_conn *ct = exp->master;
+    struct nf_conntrack_tuple *t;
+
+    char    szextaddr[15+1];
+    uint    extaddrlen;
+    int     is_stun;
+
+    get_skb_tcpdata(skb, &ptcp, &tcplen);
+    ptran = ptcp+tranoff;
+
+    if (tranoff+tranlen > tcplen || tcplen-tranoff < tranlen ||
+        tranlen < 10 || !iseol(ptran[tranlen-1]) ||
+        nf_strncasecmp(ptran, "Transport:", 10) != 0)
+    {
+        pr_info("sanity check failed\n");
+        return 0;
+    }
+    off += 10;
+    SKIP_WSPACE(ptcp+tranoff, tranlen, off);
+
+    newip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip;
+    t = &exp->tuple;
+    t->dst.u3.ip = newip;
+
+    extaddrlen = extip ? sprintf(szextaddr, "%pI4", &extip)
+                       : sprintf(szextaddr, "%pI4", &newip);
+    pr_debug("stunaddr=%s (%s)\n", szextaddr, (extip?"forced":"auto"));
+
+    rbuf1len = rbufalen = 0;
+    switch (prtspexp->pbtype)
+    {
+    case pb_single:
+        for (loport = prtspexp->loport; loport != 0; loport++) /* XXX: improper wrap? */
+        {
+            t->dst.u.udp.port = htons(loport);
+            if (nf_ct_expect_related(exp) == 0)
+            {
+                pr_debug("using port %hu\n", loport);
+                break;
+            }
+        }
+        if (loport != 0)
+        {
+            rbuf1len = sprintf(rbuf1, "%hu", loport);
+            rbufalen = sprintf(rbufa, "%hu", loport);
+        }
+        break;
+    case pb_range:
+        for (loport = prtspexp->loport; loport != 0; loport += 2) /* XXX: improper wrap? */
+        {
+            t->dst.u.udp.port = htons(loport);
+            if (nf_ct_expect_related(exp) == 0)
+            {
+                hiport = loport + 1; //~exp->mask.dst.u.udp.port;
+                pr_debug("using ports %hu-%hu\n", loport, hiport);
+                break;
+            }
+        }
+        if (loport != 0)
+        {
+            rbuf1len = sprintf(rbuf1, "%hu", loport);
+            rbufalen = sprintf(rbufa, "%hu-%hu", loport, loport+1);
+        }
+        break;
+    case pb_discon:
+        for (loport = prtspexp->loport; loport != 0; loport++) /* XXX: improper wrap? */
+        {
+            t->dst.u.udp.port = htons(loport);
+            if (nf_ct_expect_related(exp) == 0)
+            {
+                pr_debug("using port %hu (1 of 2)\n", loport);
+                break;
+            }
+        }
+        for (hiport = prtspexp->hiport; hiport != 0; hiport++) /* XXX: improper wrap? */
+        {
+            t->dst.u.udp.port = htons(hiport);
+            if (nf_ct_expect_related(exp) == 0)
+            {
+                pr_debug("using port %hu (2 of 2)\n", hiport);
+                break;
+            }
+        }
+        if (loport != 0 && hiport != 0)
+        {
+            rbuf1len = sprintf(rbuf1, "%hu", loport);
+            if (hiport == loport+1)
+            {
+                rbufalen = sprintf(rbufa, "%hu-%hu", loport, hiport);
+            }
+            else
+            {
+                rbufalen = sprintf(rbufa, "%hu/%hu", loport, hiport);
+            }
+        }
+        break;
+    }
+
+    if (rbuf1len == 0)
+    {
+        return 0;   /* cannot get replacement port(s) */
+    }
+
+    /* Transport: tran;field;field=val,tran;field;field=val,... */
+    while (off < tranlen)
+    {
+        uint        saveoff;
+        const char* pparamend;
+        uint        nextparamoff;
+
+        pparamend = memchr(ptran+off, ',', tranlen-off);
+        pparamend = (pparamend == NULL) ? ptran+tranlen : pparamend+1;
+        nextparamoff = pparamend-ptcp;
+
+        /*
+         * We pass over each param twice.  On the first pass, we look for a
+         * destination= field.  It is handled by the security policy.  If it
+         * is present, allowed, and equal to our external address, we assume
+         * that STUN is being used and we leave the client_port= field alone.
+         */
+        is_stun = 0;
+        saveoff = off;
+        while (off < nextparamoff)
+        {
+            const char* pfieldend;
+            uint        nextfieldoff;
+
+            pfieldend = memchr(ptran+off, ';', nextparamoff-off);
+            nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran+1;
+
+            if (dstact != DSTACT_NONE && strncmp(ptran+off, "destination=", 12) == 0)
+            {
+                if (strncmp(ptran+off+12, szextaddr, extaddrlen) == 0)
+                {
+                    is_stun = 1;
+                }
+                if (dstact == DSTACT_STRIP || (dstact == DSTACT_AUTO && !is_stun))
+                {
+                    diff = nextfieldoff-off;
+                    if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
+                                                         off, diff, NULL, 0))
+                    {
+                        /* mangle failed, all we can do is bail */
+			nf_ct_unexpect_related(exp);
+                        return 0;
+                    }
+                    get_skb_tcpdata(skb, &ptcp, &tcplen);
+                    ptran = ptcp+tranoff;
+                    tranlen -= diff;
+                    nextparamoff -= diff;
+                    nextfieldoff -= diff;
+                }
+            }
+
+            off = nextfieldoff;
+        }
+        if (is_stun)
+        {
+            continue;
+        }
+        off = saveoff;
+        while (off < nextparamoff)
+        {
+            const char* pfieldend;
+            uint        nextfieldoff;
+
+            pfieldend = memchr(ptran+off, ';', nextparamoff-off);
+            nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran+1;
+
+            if (strncmp(ptran+off, "client_port=", 12) == 0)
+            {
+                u_int16_t   port;
+                uint        numlen;
+                uint        origoff;
+                uint        origlen;
+                char*       rbuf    = rbuf1;
+                uint        rbuflen = rbuf1len;
+
+                off += 12;
+                origoff = (ptran-ptcp)+off;
+                origlen = 0;
+                numlen = nf_strtou16(ptran+off, &port);
+                off += numlen;
+                origlen += numlen;
+                if (port != prtspexp->loport)
+                {
+                    pr_debug("multiple ports found, port %hu ignored\n", port);
+                }
+                else
+                {
+                    if (ptran[off] == '-' || ptran[off] == '/')
+                    {
+                        off++;
+                        origlen++;
+                        numlen = nf_strtou16(ptran+off, &port);
+                        off += numlen;
+                        origlen += numlen;
+                        rbuf = rbufa;
+                        rbuflen = rbufalen;
+                    }
+
+                    /*
+                     * note we cannot just memcpy() if the sizes are the same.
+                     * the mangle function does skb resizing, checks for a
+                     * cloned skb, and updates the checksums.
+                     *
+                     * parameter 4 below is offset from start of tcp data.
+                     */
+                    diff = origlen-rbuflen;
+                    if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
+                                              origoff, origlen, rbuf, rbuflen))
+                    {
+                        /* mangle failed, all we can do is bail */
+			nf_ct_unexpect_related(exp);
+                        return 0;
+                    }
+                    get_skb_tcpdata(skb, &ptcp, &tcplen);
+                    ptran = ptcp+tranoff;
+                    tranlen -= diff;
+                    nextparamoff -= diff;
+                    nextfieldoff -= diff;
+                }
+            }
+
+            off = nextfieldoff;
+        }
+
+        off = nextparamoff;
+    }
+
+    return 1;
+}
+
+static uint
+help_out(struct sk_buff *skb, enum ip_conntrack_info ctinfo,
+	 unsigned int matchoff, unsigned int matchlen, struct ip_ct_rtsp_expect* prtspexp, 
+	 struct nf_conntrack_expect* exp)
+{
+    char*   ptcp;
+    uint    tcplen;
+    uint    hdrsoff;
+    uint    hdrslen;
+    uint    lineoff;
+    uint    linelen;
+    uint    off;
+
+    //struct iphdr* iph = (struct iphdr*)(*pskb)->nh.iph;
+    //struct tcphdr* tcph = (struct tcphdr*)((void*)iph + iph->ihl*4);
+
+    get_skb_tcpdata(skb, &ptcp, &tcplen);
+    hdrsoff = matchoff;//exp->seq - ntohl(tcph->seq);
+    hdrslen = matchlen;
+    off = hdrsoff;
+    pr_debug("NAT rtsp help_out\n");
+
+    while (nf_mime_nextline(ptcp, hdrsoff+hdrslen, &off, &lineoff, &linelen))
+    {
+        if (linelen == 0)
+        {
+            break;
+        }
+        if (off > hdrsoff+hdrslen)
+        {
+            pr_info("!! overrun !!");
+            break;
+        }
+        pr_debug("hdr: len=%u, %.*s", linelen, (int)linelen, ptcp+lineoff);
+
+        if (nf_strncasecmp(ptcp+lineoff, "Transport:", 10) == 0)
+        {
+            uint oldtcplen = tcplen;
+	    pr_debug("hdr: Transport\n");
+            if (!rtsp_mangle_tran(ctinfo, exp, prtspexp, skb, lineoff, linelen))
+            {
+		pr_debug("hdr: Transport mangle failed");
+                break;
+            }
+            get_skb_tcpdata(skb, &ptcp, &tcplen);
+            hdrslen -= (oldtcplen-tcplen);
+            off -= (oldtcplen-tcplen);
+            lineoff -= (oldtcplen-tcplen);
+            linelen -= (oldtcplen-tcplen);
+            pr_debug("rep: len=%u, %.*s", linelen, (int)linelen, ptcp+lineoff);
+        }
+    }
+
+    return NF_ACCEPT;
+}
+
+static unsigned int
+help(struct sk_buff *skb, enum ip_conntrack_info ctinfo, 
+     unsigned int matchoff, unsigned int matchlen, struct ip_ct_rtsp_expect* prtspexp,
+     struct nf_conntrack_expect* exp)
+{
+    int dir = CTINFO2DIR(ctinfo);
+    int rc = NF_ACCEPT;
+
+    switch (dir)
+    {
+    case IP_CT_DIR_ORIGINAL:
+        rc = help_out(skb, ctinfo, matchoff, matchlen, prtspexp, exp);
+        break;
+    case IP_CT_DIR_REPLY:
+	pr_debug("unmangle ! %u\n", ctinfo);
+    	/* XXX: unmangle */
+	rc = NF_ACCEPT;
+        break;
+    }
+    //UNLOCK_BH(&ip_rtsp_lock);
+
+    return rc;
+}
+
+static void expected(struct nf_conn* ct, struct nf_conntrack_expect *exp)
+{
+    struct nf_nat_ipv4_multi_range_compat mr;
+    u_int32_t newdstip, newsrcip, newip;
+
+    struct nf_conn *master = ct->master;
+
+    newdstip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
+    newsrcip = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
+    //FIXME (how to port that ?)
+    //code from 2.4 : newip = (HOOK2MANIP(hooknum) == NF_NAT_MANIP_SRC) ? newsrcip : newdstip;
+    newip = newdstip;
+
+    pr_debug("newsrcip=%pI4, newdstip=%pI4, newip=%pI4\n",
+           &newsrcip, &newdstip, &newip);
+
+    mr.rangesize = 1;
+    // We don't want to manip the per-protocol, just the IPs. 
+    mr.range[0].flags = NF_NAT_RANGE_MAP_IPS;
+    mr.range[0].min_ip = mr.range[0].max_ip = newip;
+
+    nf_nat_setup_info(ct, &mr.range[0], NF_NAT_MANIP_DST);
+}
+
+
+static void __exit fini(void)
+{
+	nf_nat_rtsp_hook = NULL;
+        nf_nat_rtsp_hook_expectfn = NULL;
+	synchronize_net();
+}
+
+static int __init init(void)
+{
+	printk("nf_nat_rtsp v" IP_NF_RTSP_VERSION " loading\n");
+
+	BUG_ON(nf_nat_rtsp_hook);
+	nf_nat_rtsp_hook = help;
+        nf_nat_rtsp_hook_expectfn = &expected;
+
+	if (stunaddr != NULL)
+		extip = in_aton(stunaddr);
+
+	if (destaction != NULL) {
+	        if (strcmp(destaction, "auto") == 0)
+			dstact = DSTACT_AUTO;
+
+		if (strcmp(destaction, "strip") == 0)
+			dstact = DSTACT_STRIP;
+
+		if (strcmp(destaction, "none") == 0)
+			dstact = DSTACT_NONE;
+	}
+
+	return 0;
+}
+
+module_init(init);
+module_exit(fini);
--- a/extensions/Kbuild
+++ b/extensions/Kbuild
@@ -35,6 +35,7 @@ obj-${build_lscan}       += xt_lscan.o
 obj-${build_pknock}      += pknock/
 obj-${build_psd}         += xt_psd.o
 obj-${build_quota2}      += xt_quota2.o
+obj-${build_rtsp}        += rtsp/
 
 -include ${M}/*.Kbuild
 -include ${M}/Kbuild.*
--- a/mconfig
+++ b/mconfig
@@ -26,3 +26,4 @@ build_lscan=m
 build_pknock=m
 build_psd=m
 build_quota2=m
+build_rtsp=m