summaryrefslogtreecommitdiffstats
path: root/xtables.c
blob: 8241687b8f5c57907458d8dddcbc84984d2cc719 (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
/*
 * (C) 2000-2006 by the netfilter coreteam <coreteam@netfilter.org>:
 *
 *	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.
 *
 *	This program is distributed in the hope that it will be useful,
 *	but WITHOUT ANY WARRANTY; without even the implied warranty of
 *	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *	GNU General Public License for more details.
 *
 *	You should have received a copy of the GNU General Public License
 *	along with this program; if not, write to the Free Software
 *	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <arpa/inet.h>

#include <xtables.h>

#ifndef NO_SHARED_LIBS
#include <dlfcn.h>
#endif

#define NPROTO	255

#ifndef PROC_SYS_MODPROBE
#define PROC_SYS_MODPROBE "/proc/sys/kernel/modprobe"
#endif

char *lib_dir;

/* the path to command to load kernel module */
const char *modprobe_program = NULL;

/* Keeping track of external matches and targets: linked lists.  */
struct xtables_match *xtables_matches;
struct xtables_target *xtables_targets;

void *fw_calloc(size_t count, size_t size)
{
	void *p;

	if ((p = calloc(count, size)) == NULL) {
		perror("ip[6]tables: calloc failed");
		exit(1);
	}

	return p;
}

void *fw_malloc(size_t size)
{
	void *p;

	if ((p = malloc(size)) == NULL) {
		perror("ip[6]tables: malloc failed");
		exit(1);
	}

	return p;
}

static char *get_modprobe(void)
{
	int procfile;
	char *ret;

#define PROCFILE_BUFSIZ	1024
	procfile = open(PROC_SYS_MODPROBE, O_RDONLY);
	if (procfile < 0)
		return NULL;

	ret = (char *) malloc(PROCFILE_BUFSIZ);
	if (ret) {
		memset(ret, 0, PROCFILE_BUFSIZ);
		switch (read(procfile, ret, PROCFILE_BUFSIZ)) {
		case -1: goto fail;
		case PROCFILE_BUFSIZ: goto fail; /* Partial read.  Wierd */
		}
		if (ret[strlen(ret)-1]=='\n') 
			ret[strlen(ret)-1]=0;
		close(procfile);
		return ret;
	}
 fail:
	free(ret);
	close(procfile);
	return NULL;
}

int xtables_insmod(const char *modname, const char *modprobe, int quiet)
{
	char *buf = NULL;
	char *argv[4];
	int status;

	/* If they don't explicitly set it, read out of kernel */
	if (!modprobe) {
		buf = get_modprobe();
		if (!buf)
			return -1;
		modprobe = buf;
	}

	switch (fork()) {
	case 0:
		argv[0] = (char *)modprobe;
		argv[1] = (char *)modname;
		if (quiet) {
			argv[2] = "-q";
			argv[3] = NULL;
		} else {
			argv[2] = NULL;
			argv[3] = NULL;
		}
		execv(argv[0], argv);

		/* not usually reached */
		exit(1);
	case -1:
		return -1;

	default: /* parent */
		wait(&status);
	}

	free(buf);
	if (WIFEXITED(status) && WEXITSTATUS(status) == 0)
		return 0;
	return -1;
}

int load_xtables_ko(const char *modprobe, int quiet)
{
	static int loaded = 0;
	static int ret = -1;

	if (!loaded) {
		ret = xtables_insmod(afinfo.kmod, modprobe, quiet);
		loaded = (ret == 0);
	}

	return ret;
}

int string_to_number_ll(const char *s, unsigned long long min,
			unsigned long long max, unsigned long long *ret)
{
	unsigned long long number;
	char *end;

	/* Handle hex, octal, etc. */
	errno = 0;
	number = strtoull(s, &end, 0);
	if (*end == '\0' && end != s) {
		/* we parsed a number, let's see if we want this */
		if (errno != ERANGE && min <= number && (!max || number <= max)) {
			*ret = number;
			return 0;
		}
	}
	return -1;
}

int string_to_number_l(const char *s, unsigned long min, unsigned long max,
		       unsigned long *ret)
{
	int result;
	unsigned long long number;

	result = string_to_number_ll(s, min, max, &number);
	*ret = (unsigned long)number;

	return result;
}

int string_to_number(const char *s, unsigned int min, unsigned int max,
		unsigned int *ret)
{
	int result;
	unsigned long number;

	result = string_to_number_l(s, min, max, &number);
	*ret = (unsigned int)number;

	return result;
}

/*
 * strtonum{,l} - string to number conversion
 *
 * If @end is NULL, we assume the caller does not want
 * a case like "15a", so reject it.
 */
bool strtonuml(const char *s, char **end, unsigned long *value,
               unsigned long min, unsigned long max)
{
	unsigned long v;
	char *my_end;

	errno = 0;
	v = strtoul(s, &my_end, 0);

	if (my_end == s)
		return false;
	if (end != NULL)
		*end = my_end;

	if (errno != ERANGE && min <= v && (max == 0 || v <= max)) {
		if (value != NULL)
			*value = v;
		if (end == NULL)
			return *my_end == '\0';
		return true;
	}

	return false;
}

bool strtonum(const char *s, char **end, unsigned int *value,
                  unsigned int min, unsigned int max)
{
	unsigned long v;
	bool ret;

	ret = strtonuml(s, end, &v, min, max);
	if (value != NULL)
		*value = v;
	return ret;
}

int service_to_port(const char *name, const char *proto)
{
	struct servent *service;

	if ((service = getservbyname(name, proto)) != NULL)
		return ntohs((unsigned short) service->s_port);

	return -1;
}

u_int16_t parse_port(const char *port, const char *proto)
{
	unsigned int portnum;

	if ((string_to_number(port, 0, 65535, &portnum)) != -1 ||
	    (portnum = service_to_port(port, proto)) != (unsigned)-1)
		return (u_int16_t)portnum;

	exit_error(PARAMETER_PROBLEM,
		   "invalid port/service `%s' specified", port);
}

void parse_interface(const char *arg, char *vianame, unsigned char *mask)
{
	int vialen = strlen(arg);
	unsigned int i;

	memset(mask, 0, IFNAMSIZ);
	memset(vianame, 0, IFNAMSIZ);

	if (vialen + 1 > IFNAMSIZ)
		exit_error(PARAMETER_PROBLEM,
			   "interface name `%s' must be shorter than IFNAMSIZ"
			   " (%i)", arg, IFNAMSIZ-1);

	strcpy(vianame, arg);
	if ((vialen == 0) || (vialen == 1 && vianame[0] == '+'))
		memset(mask, 0, IFNAMSIZ);
	else if (vianame[vialen - 1] == '+') {
		memset(mask, 0xFF, vialen - 1);
		memset(mask + vialen - 1, 0, IFNAMSIZ - vialen + 1);
		/* Don't remove `+' here! -HW */
	} else {
		/* Include nul-terminator in match */
		memset(mask, 0xFF, vialen + 1);
		memset(mask + vialen + 1, 0, IFNAMSIZ - vialen - 1);
		for (i = 0; vianame[i]; i++) {
			if (vianame[i] == ':' ||
			    vianame[i] == '!' ||
			    vianame[i] == '*') {
				fprintf(stderr,
					"Warning: weird character in interface"
					" `%s' (No aliases, :, ! or *).\n",
					vianame);
				break;
			}
		}
	}
}

#ifndef NO_SHARED_LIBS
static void *load_extension(const char *search_path, const char *prefix,
    const char *name, bool is_target)
{
	const char *dir = search_path, *next;
	void *ptr = NULL;
	struct stat sb;
	char path[256];

	do {
		next = strchr(dir, ':');
		if (next == NULL)
			next = dir + strlen(dir);
		snprintf(path, sizeof(path), "%.*s/libxt_%s.so",
		         (unsigned int)(next - dir), dir, name);

		if (dlopen(path, RTLD_NOW) != NULL) {
			/* Found library.  If it didn't register itself,
			   maybe they specified target as match. */
			if (is_target)
				ptr = find_target(name, DONT_LOAD);
			else
				ptr = find_match(name, DONT_LOAD, NULL);
		} else if (stat(path, &sb) == 0) {
			fprintf(stderr, "%s: %s\n", path, dlerror());
		}

		if (ptr != NULL)
			return ptr;

		snprintf(path, sizeof(path), "%.*s/%s%s.so",
		         (unsigned int)(next - dir), dir, prefix, name);
		if (dlopen(path, RTLD_NOW) != NULL) {
			if (is_target)
				ptr = find_target(name, DONT_LOAD);
			else
				ptr = find_match(name, DONT_LOAD, NULL);
		} else if (stat(path, &sb) == 0) {
			fprintf(stderr, "%s: %s\n", path, dlerror());
		}

		if (ptr != NULL)
			return ptr;

		dir = next + 1;
	} while (*next != '\0');

	return NULL;
}
#endif

struct xtables_match *find_match(const char *name, enum xt_tryload tryload,
				 struct xtables_rule_match **matches)
{
	struct xtables_match *ptr;
	const char *icmp6 = "icmp6";

	/* This is ugly as hell. Nonetheless, there is no way of changing
	 * this without hurting backwards compatibility */
	if ( (strcmp(name,"icmpv6") == 0) ||
	     (strcmp(name,"ipv6-icmp") == 0) ||
	     (strcmp(name,"icmp6") == 0) )
		name = icmp6;

	for (ptr = xtables_matches; ptr; ptr = ptr->next) {
		if (strcmp(name, ptr->name) == 0) {
			struct xtables_match *clone;

			/* First match of this type: */
			if (ptr->m == NULL)
				break;

			/* Second and subsequent clones */
			clone = fw_malloc(sizeof(struct xtables_match));
			memcpy(clone, ptr, sizeof(struct xtables_match));
			clone->mflags = 0;
			/* This is a clone: */
			clone->next = clone;

			ptr = clone;
			break;
		}
	}

#ifndef NO_SHARED_LIBS
	if (!ptr && tryload != DONT_LOAD && tryload != DURING_LOAD) {
		ptr = load_extension(lib_dir, afinfo.libprefix, name, false);

		if (ptr == NULL && tryload == LOAD_MUST_SUCCEED)
			exit_error(PARAMETER_PROBLEM,
				   "Couldn't load match `%s':%s\n",
				   name, dlerror());
	}
#else
	if (ptr && !ptr->loaded) {
		if (tryload != DONT_LOAD)
			ptr->loaded = 1;
		else
			ptr = NULL;
	}
	if(!ptr && (tryload == LOAD_MUST_SUCCEED)) {
		exit_error(PARAMETER_PROBLEM,
			   "Couldn't find match `%s'\n", name);
	}
#endif

	if (ptr && matches) {
		struct xtables_rule_match **i;
		struct xtables_rule_match *newentry;

		newentry = fw_malloc(sizeof(struct xtables_rule_match));

		for (i = matches; *i; i = &(*i)->next) {
			if (strcmp(name, (*i)->match->name) == 0)
				(*i)->completed = 1;
		}
		newentry->match = ptr;
		newentry->completed = 0;
		newentry->next = NULL;
		*i = newentry;
	}

	return ptr;
}


struct xtables_target *find_target(const char *name, enum xt_tryload tryload)
{
	struct xtables_target *ptr;

	/* Standard target? */
	if (strcmp(name, "") == 0
	    || strcmp(name, XTC_LABEL_ACCEPT) == 0
	    || strcmp(name, XTC_LABEL_DROP) == 0
	    || strcmp(name, XTC_LABEL_QUEUE) == 0
	    || strcmp(name, XTC_LABEL_RETURN) == 0)
		name = "standard";

	for (ptr = xtables_targets; ptr; ptr = ptr->next) {
		if (strcmp(name, ptr->name) == 0)
			break;
	}

#ifndef NO_SHARED_LIBS
	if (!ptr && tryload != DONT_LOAD && tryload != DURING_LOAD) {
		ptr = load_extension(lib_dir, afinfo.libprefix, name, true);

		if (ptr == NULL && tryload == LOAD_MUST_SUCCEED)
			exit_error(PARAMETER_PROBLEM,
				   "Couldn't load target `%s':%s\n",
				   name, dlerror());
	}
#else
	if (ptr && !ptr->loaded) {
		if (tryload != DONT_LOAD)
			ptr->loaded = 1;
		else
			ptr = NULL;
	}
	if(!ptr && (tryload == LOAD_MUST_SUCCEED)) {
		exit_error(PARAMETER_PROBLEM,
			   "Couldn't find target `%s'\n", name);
	}
#endif

	if (ptr)
		ptr->used = 1;

	return ptr;
}

static int compatible_revision(const char *name, u_int8_t revision, int opt)
{
	struct xt_get_revision rev;
	socklen_t s = sizeof(rev);
	int max_rev, sockfd;

	sockfd = socket(afinfo.family, SOCK_RAW, IPPROTO_RAW);
	if (sockfd < 0) {
		if (errno == EPERM) {
			/* revision 0 is always supported. */
			if (revision != 0)
				fprintf(stderr, "Could not determine whether "
						"revision %u is supported, "
						"assuming it is.\n",
					revision);
			return 1;
		}
		fprintf(stderr, "Could not open socket to kernel: %s\n",
			strerror(errno));
		exit(1);
	}

	load_xtables_ko(modprobe_program, 1);

	strcpy(rev.name, name);
	rev.revision = revision;

	max_rev = getsockopt(sockfd, afinfo.ipproto, opt, &rev, &s);
	if (max_rev < 0) {
		/* Definitely don't support this? */
		if (errno == ENOENT || errno == EPROTONOSUPPORT) {
			close(sockfd);
			return 0;
		} else if (errno == ENOPROTOOPT) {
			close(sockfd);
			/* Assume only revision 0 support (old kernel) */
			return (revision == 0);
		} else {
			fprintf(stderr, "getsockopt failed strangely: %s\n",
				strerror(errno));
			exit(1);
		}
	}
	close(sockfd);
	return 1;
}


static int compatible_match_revision(const char *name, u_int8_t revision)
{
	return compatible_revision(name, revision, afinfo.so_rev_match);
}

static int compatible_target_revision(const char *name, u_int8_t revision)
{
	return compatible_revision(name, revision, afinfo.so_rev_target);
}

void xtables_register_match(struct xtables_match *me)
{
	struct xtables_match **i, *old;

	if (strcmp(me->version, program_version) != 0) {
		fprintf(stderr, "%s: match `%s' v%s (I'm v%s).\n",
			program_name, me->name, me->version, program_version);
		exit(1);
	}

	/* Revision field stole a char from name. */
	if (strlen(me->name) >= XT_FUNCTION_MAXNAMELEN-1) {
		fprintf(stderr, "%s: target `%s' has invalid name\n",
			program_name, me->name);
		exit(1);
	}

	if (me->family >= NPROTO) {
		fprintf(stderr,
			"%s: BUG: match %s has invalid protocol family\n",
			program_name, me->name);
		exit(1);
	}

	/* ignore not interested match */
	if (me->family != afinfo.family && me->family != AF_UNSPEC)
		return;

	old = find_match(me->name, DURING_LOAD, NULL);
	if (old) {
		if (old->revision == me->revision &&
		    old->family == me->family) {
			fprintf(stderr,
				"%s: match `%s' already registered.\n",
				program_name, me->name);
			exit(1);
		}

		/* Now we have two (or more) options, check compatibility. */
		if (compatible_match_revision(old->name, old->revision)
		    && old->revision > me->revision)
			return;

		/* See if new match can be used. */
		if (!compatible_match_revision(me->name, me->revision))
			return;

		/* Prefer !AF_UNSPEC over AF_UNSPEC for same revision. */
		if (old->revision == me->revision && me->family == AF_UNSPEC)
			return;

		/* Delete old one. */
		for (i = &xtables_matches; *i!=old; i = &(*i)->next);
		*i = old->next;
	}

	if (me->size != XT_ALIGN(me->size)) {
		fprintf(stderr, "%s: match `%s' has invalid size %u.\n",
			program_name, me->name, (unsigned int)me->size);
		exit(1);
	}

	/* Append to list. */
	for (i = &xtables_matches; *i; i = &(*i)->next);
	me->next = NULL;
	*i = me;

	me->m = NULL;
	me->mflags = 0;
}

void xtables_register_target(struct xtables_target *me)
{
	struct xtables_target *old;

	if (strcmp(me->version, program_version) != 0) {
		fprintf(stderr, "%s: target `%s' v%s (I'm v%s).\n",
			program_name, me->name, me->version, program_version);
		exit(1);
	}

	/* Revision field stole a char from name. */
	if (strlen(me->name) >= XT_FUNCTION_MAXNAMELEN-1) {
		fprintf(stderr, "%s: target `%s' has invalid name\n",
			program_name, me->name);
		exit(1);
	}

	if (me->family >= NPROTO) {
		fprintf(stderr,
			"%s: BUG: target %s has invalid protocol family\n",
			program_name, me->name);
		exit(1);
	}

	/* ignore not interested target */
	if (me->family != afinfo.family && me->family != AF_UNSPEC)
		return;

	old = find_target(me->name, DURING_LOAD);
	if (old) {
		struct xtables_target **i;

		if (old->revision == me->revision &&
		    old->family == me->family) {
			fprintf(stderr,
				"%s: target `%s' already registered.\n",
				program_name, me->name);
			exit(1);
		}

		/* Now we have two (or more) options, check compatibility. */
		if (compatible_target_revision(old->name, old->revision)
		    && old->revision > me->revision)
			return;

		/* See if new target can be used. */
		if (!compatible_target_revision(me->name, me->revision))
			return;

		/* Prefer !AF_UNSPEC over AF_UNSPEC for same revision. */
		if (old->revision == me->revision && me->family == AF_UNSPEC)
			return;

		/* Delete old one. */
		for (i = &xtables_targets; *i!=old; i = &(*i)->next);
		*i = old->next;
	}

	if (me->size != XT_ALIGN(me->size)) {
		fprintf(stderr, "%s: target `%s' has invalid size %u.\n",
			program_name, me->name, (unsigned int)me->size);
		exit(1);
	}

	/* Prepend to list. */
	me->next = xtables_targets;
	xtables_targets = me;
	me->t = NULL;
	me->tflags = 0;
}

void param_act(unsigned int status, const char *p1, ...)
{
	const char *p2, *p3;
	va_list args;
	bool b;

	va_start(args, p1);

	switch (status) {
	case P_ONLY_ONCE:
		p2 = va_arg(args, const char *);
		b  = va_arg(args, unsigned int);
		if (!b)
			return;
		exit_error(PARAMETER_PROBLEM,
		           "%s: \"%s\" option may only be specified once",
		           p1, p2);
		break;
	case P_NO_INVERT:
		p2 = va_arg(args, const char *);
		b  = va_arg(args, unsigned int);
		if (!b)
			return;
		exit_error(PARAMETER_PROBLEM,
		           "%s: \"%s\" option cannot be inverted", p1, p2);
		break;
	case P_BAD_VALUE:
		p2 = va_arg(args, const char *);
		p3 = va_arg(args, const char *);
		exit_error(PARAMETER_PROBLEM,
		           "%s: Bad value for \"%s\" option: \"%s\"",
		           p1, p2, p3);
		break;
	case P_ONE_ACTION:
		b = va_arg(args, unsigned int);
		if (!b)
			return;
		exit_error(PARAMETER_PROBLEM,
		           "%s: At most one action is possible", p1);
		break;
	default:
		exit_error(status, p1, args);
		break;
	}

	va_end(args);
}

const char *ipaddr_to_numeric(const struct in_addr *addrp)
{
	static char buf[20];
	const unsigned char *bytep = (const void *)&addrp->s_addr;

	sprintf(buf, "%u.%u.%u.%u", bytep[0], bytep[1], bytep[2], bytep[3]);
	return buf;
}

static const char *ipaddr_to_host(const struct in_addr *addr)
{
	struct hostent *host;

	host = gethostbyaddr(addr, sizeof(struct in_addr), AF_INET);
	if (host == NULL)
		return NULL;

	return host->h_name;
}

static const char *ipaddr_to_network(const struct in_addr *addr)
{
	struct netent *net;

	if ((net = getnetbyaddr(ntohl(addr->s_addr), AF_INET)) != NULL)
		return net->n_name;

	return NULL;
}

const char *ipaddr_to_anyname(const struct in_addr *addr)
{
	const char *name;

	if ((name = ipaddr_to_host(addr)) != NULL ||
	    (name = ipaddr_to_network(addr)) != NULL)
		return name;

	return ipaddr_to_numeric(addr);
}

const char *ipmask_to_numeric(const struct in_addr *mask)
{
	static char buf[20];
	uint32_t maskaddr, bits;
	int i;

	maskaddr = ntohl(mask->s_addr);

	if (maskaddr == 0xFFFFFFFFL)
		/* we don't want to see "/32" */
		return "";

	i = 32;
	bits = 0xFFFFFFFEL;
	while (--i >= 0 && maskaddr != bits)
		bits <<= 1;
	if (i >= 0)
		sprintf(buf, "/%d", i);
	else
		/* mask was not a decent combination of 1's and 0's */
		sprintf(buf, "/%s", ipaddr_to_numeric(mask));

	return buf;
}

static struct in_addr *__numeric_to_ipaddr(const char *dotted, bool is_mask)
{
	static struct in_addr addr;
	unsigned char *addrp;
	unsigned int onebyte;
	char buf[20], *p, *q;
	int i;

	/* copy dotted string, because we need to modify it */
	strncpy(buf, dotted, sizeof(buf) - 1);
	buf[sizeof(buf) - 1] = '\0';
	addrp = (void *)&addr.s_addr;

	p = buf;
	for (i = 0; i < 3; ++i) {
		if ((q = strchr(p, '.')) == NULL) {
			if (is_mask)
				return NULL;

			/* autocomplete, this is a network address */
			if (!strtonum(p, NULL, &onebyte, 0, 255))
				return NULL;

			addrp[i] = onebyte;
			while (i < 3)
				addrp[++i] = 0;

			return &addr;
		}

		*q = '\0';
		if (!strtonum(p, NULL, &onebyte, 0, 255))
			return NULL;

		addrp[i] = onebyte;
		p = q + 1;
	}

	/* we have checked 3 bytes, now we check the last one */
	if (!strtonum(p, NULL, &onebyte, 0, 255))
		return NULL;

	addrp[3] = onebyte;
	return &addr;
}

struct in_addr *numeric_to_ipaddr(const char *dotted)
{
	return __numeric_to_ipaddr(dotted, false);
}

struct in_addr *numeric_to_ipmask(const char *dotted)
{
	return __numeric_to_ipaddr(dotted, true);
}

static struct in_addr *network_to_ipaddr(const char *name)
{
	static struct in_addr addr;
	struct netent *net;

	if ((net = getnetbyname(name)) != NULL) {
		if (net->n_addrtype != AF_INET)
			return NULL;
		addr.s_addr = htonl(net->n_net);
		return &addr;
	}

	return NULL;
}

static struct in_addr *host_to_ipaddr(const char *name, unsigned int *naddr)
{
	struct hostent *host;
	struct in_addr *addr;
	unsigned int i;

	*naddr = 0;
	if ((host = gethostbyname(name)) != NULL) {
		if (host->h_addrtype != AF_INET ||
		    host->h_length != sizeof(struct in_addr))
			return NULL;

		while (host->h_addr_list[*naddr] != NULL)
			++*naddr;
		addr = fw_calloc(*naddr, sizeof(struct in_addr) * *naddr);
		for (i = 0; i < *naddr; i++)
			memcpy(&addr[i], host->h_addr_list[i],
			       sizeof(struct in_addr));
		return addr;
	}

	return NULL;
}

static struct in_addr *
ipparse_hostnetwork(const char *name, unsigned int *naddrs)
{
	struct in_addr *addrptmp, *addrp;

	if ((addrptmp = numeric_to_ipaddr(name)) != NULL ||
	    (addrptmp = network_to_ipaddr(name)) != NULL) {
		addrp = fw_malloc(sizeof(struct in_addr));
		memcpy(addrp, addrptmp, sizeof(*addrp));
		*naddrs = 1;
		return addrp;
	}
	if ((addrptmp = host_to_ipaddr(name, naddrs)) != NULL)
		return addrptmp;

	exit_error(PARAMETER_PROBLEM, "host/network `%s' not found", name);
}

static struct in_addr *parse_ipmask(const char *mask)
{
	static struct in_addr maskaddr;
	struct in_addr *addrp;
	unsigned int bits;

	if (mask == NULL) {
		/* no mask at all defaults to 32 bits */
		maskaddr.s_addr = 0xFFFFFFFF;
		return &maskaddr;
	}
	if ((addrp = numeric_to_ipmask(mask)) != NULL)
		/* dotted_to_addr already returns a network byte order addr */
		return addrp;
	if (string_to_number(mask, 0, 32, &bits) == -1)
		exit_error(PARAMETER_PROBLEM,
			   "invalid mask `%s' specified", mask);
	if (bits != 0) {
		maskaddr.s_addr = htonl(0xFFFFFFFF << (32 - bits));
		return &maskaddr;
	}

	maskaddr.s_addr = 0U;
	return &maskaddr;
}

void ipparse_hostnetworkmask(const char *name, struct in_addr **addrpp,
                             struct in_addr *maskp, unsigned int *naddrs)
{
	unsigned int i, j, k, n;
	struct in_addr *addrp;
	char buf[256], *p;

	strncpy(buf, name, sizeof(buf) - 1);
	buf[sizeof(buf) - 1] = '\0';
	if ((p = strrchr(buf, '/')) != NULL) {
		*p = '\0';
		addrp = parse_ipmask(p + 1);
	} else {
		addrp = parse_ipmask(NULL);
	}
	memcpy(maskp, addrp, sizeof(*maskp));

	/* if a null mask is given, the name is ignored, like in "any/0" */
	if (maskp->s_addr == 0U)
		strcpy(buf, "0.0.0.0");

	addrp = *addrpp = ipparse_hostnetwork(buf, naddrs);
	n = *naddrs;
	for (i = 0, j = 0; i < n; ++i) {
		addrp[j++].s_addr &= maskp->s_addr;
		for (k = 0; k < j - 1; ++k)
			if (addrp[k].s_addr == addrp[j-1].s_addr) {
				--*naddrs;
				--j;
				break;
			}
	}
}

const char *ip6addr_to_numeric(const struct in6_addr *addrp)
{
	/* 0000:0000:0000:0000:0000:000.000.000.000
	 * 0000:0000:0000:0000:0000:0000:0000:0000 */
	static char buf[50+1];
	return inet_ntop(AF_INET6, addrp, buf, sizeof(buf));
}

static const char *ip6addr_to_host(const struct in6_addr *addr)
{
	static char hostname[NI_MAXHOST];
	struct sockaddr_in6 saddr;
	int err;

	memset(&saddr, 0, sizeof(struct sockaddr_in6));
	memcpy(&saddr.sin6_addr, addr, sizeof(*addr));
	saddr.sin6_family = AF_INET6;

	err = getnameinfo((const void *)&saddr, sizeof(struct sockaddr_in6),
	      hostname, sizeof(hostname) - 1, NULL, 0, 0);
	if (err != 0) {
#ifdef DEBUG
		fprintf(stderr,"IP2Name: %s\n",gai_strerror(err));
#endif
		return NULL;
	}

#ifdef DEBUG
	fprintf (stderr, "\naddr2host: %s\n", hostname);
#endif
	return hostname;
}

const char *ip6addr_to_anyname(const struct in6_addr *addr)
{
	const char *name;

	if ((name = ip6addr_to_host(addr)) != NULL)
		return name;

	return ip6addr_to_numeric(addr);
}

static int ip6addr_prefix_length(const struct in6_addr *k)
{
	unsigned int bits = 0;
	uint32_t a, b, c, d;

	a = k->s6_addr32[0];
	b = k->s6_addr32[1];
	c = k->s6_addr32[2];
	d = k->s6_addr32[3];
	while (a & 0x80000000U) {
		++bits;
		a <<= 1;
		a  |= (b >> 31) & 1;
		b <<= 1;
		b  |= (c >> 31) & 1;
		c <<= 1;
		c  |= (d >> 31) & 1;
		d <<= 1;
	}
	if (a != 0 || b != 0 || c != 0 || d != 0)
		return -1;
	return bits;
}

const char *ip6mask_to_numeric(const struct in6_addr *addrp)
{
	static char buf[50+2];
	int l = ip6addr_prefix_length(addrp);

	if (l == -1) {
		strcpy(buf, "/");
		strcat(buf, ip6addr_to_numeric(addrp));
		return buf;
	}
	sprintf(buf, "/%d", l);
	return buf;
}

struct in6_addr *numeric_to_ip6addr(const char *num)
{
	static struct in6_addr ap;
	int err;

	if ((err = inet_pton(AF_INET6, num, &ap)) == 1)
		return &ap;
#ifdef DEBUG
	fprintf(stderr, "\nnumeric2addr: %d\n", err);
#endif
	return NULL;
}

static struct in6_addr *
host_to_ip6addr(const char *name, unsigned int *naddr)
{
	static struct in6_addr *addr;
	struct addrinfo hints;
	struct addrinfo *res;
	int err;

	memset(&hints, 0, sizeof(hints));
	hints.ai_flags    = AI_CANONNAME;
	hints.ai_family   = AF_INET6;
	hints.ai_socktype = SOCK_RAW;
	hints.ai_protocol = IPPROTO_IPV6;
	hints.ai_next     = NULL;

	*naddr = 0;
	if ((err = getaddrinfo(name, NULL, &hints, &res)) != 0) {
#ifdef DEBUG
		fprintf(stderr,"Name2IP: %s\n",gai_strerror(err));
#endif
		return NULL;
	} else {
		if (res->ai_family != AF_INET6 ||
		    res->ai_addrlen != sizeof(struct sockaddr_in6))
			return NULL;

#ifdef DEBUG
		fprintf(stderr, "resolved: len=%d  %s ", res->ai_addrlen,
		        ip6addr_to_numeric(&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr));
#endif
		/* Get the first element of the address-chain */
		addr = fw_malloc(sizeof(struct in6_addr));
		memcpy(addr, &((const struct sockaddr_in6 *)res->ai_addr)->sin6_addr,
		       sizeof(struct in6_addr));
		freeaddrinfo(res);
		*naddr = 1;
		return addr;
	}

	return NULL;
}

static struct in6_addr *network_to_ip6addr(const char *name)
{
	/*	abort();*/
	/* TODO: not implemented yet, but the exception breaks the
	 *       name resolvation */
	return NULL;
}

static struct in6_addr *
ip6parse_hostnetwork(const char *name, unsigned int *naddrs)
{
	struct in6_addr *addrp, *addrptmp;

	if ((addrptmp = numeric_to_ip6addr(name)) != NULL ||
	    (addrptmp = network_to_ip6addr(name)) != NULL) {
		addrp = fw_malloc(sizeof(struct in6_addr));
		memcpy(addrp, addrptmp, sizeof(*addrp));
		*naddrs = 1;
		return addrp;
	}
	if ((addrp = host_to_ip6addr(name, naddrs)) != NULL)
		return addrp;

	exit_error(PARAMETER_PROBLEM, "host/network `%s' not found", name);
}

static struct in6_addr *parse_ip6mask(char *mask)
{
	static struct in6_addr maskaddr;
	struct in6_addr *addrp;
	unsigned int bits;

	if (mask == NULL) {
		/* no mask at all defaults to 128 bits */
		memset(&maskaddr, 0xff, sizeof maskaddr);
		return &maskaddr;
	}
	if ((addrp = numeric_to_ip6addr(mask)) != NULL)
		return addrp;
	if (string_to_number(mask, 0, 128, &bits) == -1)
		exit_error(PARAMETER_PROBLEM,
			   "invalid mask `%s' specified", mask);
	if (bits != 0) {
		char *p = (void *)&maskaddr;
		memset(p, 0xff, bits / 8);
		memset(p + (bits / 8) + 1, 0, (128 - bits) / 8);
		p[bits/8] = 0xff << (8 - (bits & 7));
		return &maskaddr;
	}

	memset(&maskaddr, 0, sizeof(maskaddr));
	return &maskaddr;
}

void ip6parse_hostnetworkmask(const char *name, struct in6_addr **addrpp,
                              struct in6_addr *maskp, unsigned int *naddrs)
{
	struct in6_addr *addrp;
	unsigned int i, j, k, n;
	char buf[256], *p;

	strncpy(buf, name, sizeof(buf) - 1);
	buf[sizeof(buf)-1] = '\0';
	if ((p = strrchr(buf, '/')) != NULL) {
		*p = '\0';
		addrp = parse_ip6mask(p + 1);
	} else {
		addrp = parse_ip6mask(NULL);
	}
	memcpy(maskp, addrp, sizeof(*maskp));

	/* if a null mask is given, the name is ignored, like in "any/0" */
	if (memcmp(maskp, &in6addr_any, sizeof(in6addr_any)) == 0)
		strcpy(buf, "::");

	addrp = *addrpp = ip6parse_hostnetwork(buf, naddrs);
	n = *naddrs;
	for (i = 0, j = 0; i < n; ++i) {
		for (k = 0; k < 4; ++k)
			addrp[j].s6_addr32[k] &= maskp->s6_addr32[k];
		++j;
		for (k = 0; k < j - 1; ++k)
			if (IN6_ARE_ADDR_EQUAL(&addrp[k], &addrp[j - 1])) {
				--*naddrs;
				--j;
				break;
			}
	}
}

void save_string(const char *value)
{
	static const char no_quote_chars[] = "_-0123456789"
		"abcdefghijklmnopqrstuvwxyz"
		"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	static const char escape_chars[] = "\"\\'";
	size_t length;
	const char *p;

	length = strcspn(value, no_quote_chars);
	if (length > 0 && value[length] == 0) {
		/* no quoting required */
		fputs(value, stdout);
		putchar(' ');
	} else {
		/* there is at least one dangerous character in the
		   value, which we have to quote.  Write double quotes
		   around the value and escape special characters with
		   a backslash */
		putchar('"');

		for (p = strpbrk(value, escape_chars); p != NULL;
		     p = strpbrk(value, escape_chars)) {
			if (p > value)
				fwrite(value, 1, p - value, stdout);
			putchar('\\');
			putchar(*p);
			value = p + 1;
		}

		/* print the rest and finish the double quoted
		   string */
		fputs(value, stdout);
		printf("\" ");
	}
}