libipt_ttl.c revision 703828fffcbcefa7adf1b835ffe930d91dcb75d7 
1/* Shared library add-on to iptables to add TTL matching support
2 * (C) 2000 by Harald Welte <laforge@gnumonks.org>
3 *
4 * Version: 1.3
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 <iptables.h>
13
14#include <linux/netfilter_ipv4/ip_tables.h>
15#include <linux/netfilter_ipv4/ipt_ttl.h>
16
17static void help(void)
18{
19	printf(
20"TTL match v%s options:\n"
21"  --ttl value		Match time to live value\n", NETFILTER_VERSION);
22}
23
24static void init(struct ipt_entry_match *m, unsigned int *nfcache)
25{
26	/* caching not yet implemented */
27}
28
29static int parse(int c, char **argv, int invert, unsigned int *flags,
30		const struct ipt_entry *entry, unsigned int *nfcache,
31		struct ipt_entry_match **match)
32{
33	struct ipt_ttl_info *info = (struct ipt_ttl_info *) (*match)->data;
34	u_int8_t value;
35
36	switch (c) {
37		case '1':
38			if (check_inverse(optarg, &invert))
39				optind++;
40			value = atoi(argv[optind-1]);
41
42			/* is 0 allowed? */
43			info->ttl = value;
44			if (invert)
45				info->invert = 1;
46			break;
47		default:
48			return 0;
49
50	}
51
52	return 1;
53}
54
55static void final_check(unsigned int flags)
56{
57	if (!flags)
58		exit_error(PARAMETER_PROBLEM,
59			"TTL match: You must specify `--ttl'");
60}
61
62static void print(const struct ipt_ip *ip,
63		const struct ipt_entry_match *match,
64		int numeric)
65{
66	const struct ipt_ttl_info *info =
67		(struct ipt_ttl_info *) match->data;
68
69	printf("TTL match ");
70	if (info->invert)
71		printf("!");
72	printf("%u ", info->ttl);
73}
74
75static void save(const struct ipt_ip *ip,
76		const struct ipt_entry_match *match)
77{
78	const struct ipt_ttl_info *info =
79		(struct ipt_ttl_info *) match->data;
80
81	printf("--ttl ");
82	if (info->invert)
83		printf("!");
84	printf("%u ", info->ttl);
85}
86
87static struct option opts[] = {
88	{ "ttl", 0, '1' },
89	{ 0 }
90};
91
92struct iptables_match ttl = {
93	NULL,
94	"ttl",
95	NETFILTER_VERSION,
96	IPT_ALIGN(sizeof(struct ipt_ttl_info)),
97	IPT_ALIGN(sizeof(struct ipt_ttl_info)),
98	&help,
99	&init,
100	&parse,
101	&final_check,
102	&print,
103	&save,
104	opts
105};
106
107
108void _init(void)
109{
110	register_match(&ttl);
111}
112