libipt_ttl.c revision 73866357e4a7a0fdc1b293bf8863fee2bd56da9e 
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#include <stdbool.h>
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	}
72
73	if (*flags)
74		xtables_error(PARAMETER_PROBLEM,
75				"Can't specify TTL option twice");
76	*flags = 1;
77
78	return 1;
79}
80
81static void ttl_check(unsigned int flags)
82{
83	if (!flags)
84		xtables_error(PARAMETER_PROBLEM,
85			"TTL match: You must specify one of "
86			"`--ttl-eq', `--ttl-lt', `--ttl-gt");
87}
88
89static void ttl_print(const void *ip, const struct xt_entry_match *match,
90                      int numeric)
91{
92	const struct ipt_ttl_info *info =
93		(struct ipt_ttl_info *) match->data;
94
95	printf(" TTL match ");
96	switch (info->mode) {
97		case IPT_TTL_EQ:
98			printf("TTL ==");
99			break;
100		case IPT_TTL_NE:
101			printf("TTL !=");
102			break;
103		case IPT_TTL_LT:
104			printf("TTL <");
105			break;
106		case IPT_TTL_GT:
107			printf("TTL >");
108			break;
109	}
110	printf(" %u", info->ttl);
111}
112
113static void ttl_save(const void *ip, const struct xt_entry_match *match)
114{
115	const struct ipt_ttl_info *info =
116		(struct ipt_ttl_info *) match->data;
117
118	switch (info->mode) {
119		case IPT_TTL_EQ:
120			printf(" --ttl-eq");
121			break;
122		case IPT_TTL_NE:
123			printf(" ! --ttl-eq");
124			break;
125		case IPT_TTL_LT:
126			printf(" --ttl-lt");
127			break;
128		case IPT_TTL_GT:
129			printf(" --ttl-gt");
130			break;
131		default:
132			/* error */
133			break;
134	}
135	printf(" %u", info->ttl);
136}
137
138static const struct option ttl_opts[] = {
139	{.name = "ttl",    .has_arg = true, .val = '2'},
140	{.name = "ttl-eq", .has_arg = true, .val = '2'},
141	{.name = "ttl-lt", .has_arg = true, .val = '3'},
142	{.name = "ttl-gt", .has_arg = true, .val = '4'},
143	XT_GETOPT_TABLEEND,
144};
145
146static struct xtables_match ttl_mt_reg = {
147	.name		= "ttl",
148	.version	= XTABLES_VERSION,
149	.family		= NFPROTO_IPV4,
150	.size		= XT_ALIGN(sizeof(struct ipt_ttl_info)),
151	.userspacesize	= XT_ALIGN(sizeof(struct ipt_ttl_info)),
152	.help		= ttl_help,
153	.parse		= ttl_parse,
154	.final_check	= ttl_check,
155	.print		= ttl_print,
156	.save		= ttl_save,
157	.extra_opts	= ttl_opts,
158};
159
160
161void _init(void)
162{
163	xtables_register_match(&ttl_mt_reg);
164}
165