libipt_ttl.c revision bf97128c7262f17a02fec41cdae75b472ba77f88 
1/* Shared library add-on to iptables to add TTL matching support
2 * (C) 2000 by Harald Welte <laforge@gnumonks.org>
3 *
4 * $Id$
5 *
6 * This program is released under the terms of GNU GPL */
7
8#include <stdio.h>
9#include <stdlib.h>
10#include <string.h>
11#include <getopt.h>
12#include <xtables.h>
13
14#include <linux/netfilter_ipv4/ipt_ttl.h>
15
16static void ttl_help(void)
17{
18	printf(
19"ttl match options:\n"
20"  --ttl-eq value	Match time to live value\n"
21"  --ttl-lt value	Match TTL < value\n"
22"  --ttl-gt value	Match TTL > value\n");
23}
24
25static int ttl_parse(int c, char **argv, int invert, unsigned int *flags,
26                     const void *entry, struct xt_entry_match **match)
27{
28	struct ipt_ttl_info *info = (struct ipt_ttl_info *) (*match)->data;
29	unsigned int value;
30
31	xtables_check_inverse(optarg, &invert, &optind, 0, argv);
32
33	switch (c) {
34		case '2':
35			if (!xtables_strtoui(optarg, NULL, &value, 0, UINT8_MAX))
36				xtables_error(PARAMETER_PROBLEM,
37				           "ttl: Expected value between 0 and 255");
38
39			if (invert)
40				info->mode = IPT_TTL_NE;
41			else
42				info->mode = IPT_TTL_EQ;
43
44			/* is 0 allowed? */
45			info->ttl = value;
46			break;
47		case '3':
48			if (!xtables_strtoui(optarg, NULL, &value, 0, UINT8_MAX))
49				xtables_error(PARAMETER_PROBLEM,
50				           "ttl: Expected value between 0 and 255");
51
52			if (invert)
53				xtables_error(PARAMETER_PROBLEM,
54						"ttl: unexpected `!'");
55
56			info->mode = IPT_TTL_LT;
57			info->ttl = value;
58			break;
59		case '4':
60			if (!xtables_strtoui(optarg, NULL, &value, 0, UINT8_MAX))
61				xtables_error(PARAMETER_PROBLEM,
62				           "ttl: Expected value between 0 and 255");
63
64			if (invert)
65				xtables_error(PARAMETER_PROBLEM,
66						"ttl: unexpected `!'");
67
68			info->mode = IPT_TTL_GT;
69			info->ttl = value;
70			break;
71		default:
72			return 0;
73
74	}
75
76	if (*flags)
77		xtables_error(PARAMETER_PROBLEM,
78				"Can't specify TTL option twice");
79	*flags = 1;
80
81	return 1;
82}
83
84static void ttl_check(unsigned int flags)
85{
86	if (!flags)
87		xtables_error(PARAMETER_PROBLEM,
88			"TTL match: You must specify one of "
89			"`--ttl-eq', `--ttl-lt', `--ttl-gt");
90}
91
92static void ttl_print(const void *ip, const struct xt_entry_match *match,
93                      int numeric)
94{
95	const struct ipt_ttl_info *info =
96		(struct ipt_ttl_info *) match->data;
97
98	printf("TTL match ");
99	switch (info->mode) {
100		case IPT_TTL_EQ:
101			printf("TTL == ");
102			break;
103		case IPT_TTL_NE:
104			printf("TTL != ");
105			break;
106		case IPT_TTL_LT:
107			printf("TTL < ");
108			break;
109		case IPT_TTL_GT:
110			printf("TTL > ");
111			break;
112	}
113	printf("%u ", info->ttl);
114}
115
116static void ttl_save(const void *ip, const struct xt_entry_match *match)
117{
118	const struct ipt_ttl_info *info =
119		(struct ipt_ttl_info *) match->data;
120
121	switch (info->mode) {
122		case IPT_TTL_EQ:
123			printf("--ttl-eq ");
124			break;
125		case IPT_TTL_NE:
126			printf("! --ttl-eq ");
127			break;
128		case IPT_TTL_LT:
129			printf("--ttl-lt ");
130			break;
131		case IPT_TTL_GT:
132			printf("--ttl-gt ");
133			break;
134		default:
135			/* error */
136			break;
137	}
138	printf("%u ", info->ttl);
139}
140
141static const struct option ttl_opts[] = {
142	{ "ttl", 1, NULL, '2' },
143	{ "ttl-eq", 1, NULL, '2'},
144	{ "ttl-lt", 1, NULL, '3'},
145	{ "ttl-gt", 1, NULL, '4'},
146	{ .name = NULL }
147};
148
149static struct xtables_match ttl_mt_reg = {
150	.name		= "ttl",
151	.version	= XTABLES_VERSION,
152	.family		= NFPROTO_IPV4,
153	.size		= XT_ALIGN(sizeof(struct ipt_ttl_info)),
154	.userspacesize	= XT_ALIGN(sizeof(struct ipt_ttl_info)),
155	.help		= ttl_help,
156	.parse		= ttl_parse,
157	.final_check	= ttl_check,
158	.print		= ttl_print,
159	.save		= ttl_save,
160	.extra_opts	= ttl_opts,
161};
162
163
164void _init(void)
165{
166	xtables_register_match(&ttl_mt_reg);
167}
168