libipt_TTL.c revision bf97128c7262f17a02fec41cdae75b472ba77f88 
1/* Shared library add-on to iptables for the TTL target
2 * (C) 2000 by Harald Welte <laforge@gnumonks.org>
3 *
4 * $Id$
5 *
6 * This program is distributed under the terms of GNU GPL
7 */
8#include <stdio.h>
9#include <string.h>
10#include <stdlib.h>
11#include <getopt.h>
12#include <xtables.h>
13
14#include <linux/netfilter_ipv4/ipt_TTL.h>
15
16#define IPT_TTL_USED	1
17
18static void TTL_help(void)
19{
20	printf(
21"TTL target options\n"
22"  --ttl-set value		Set TTL to <value 0-255>\n"
23"  --ttl-dec value		Decrement TTL by <value 1-255>\n"
24"  --ttl-inc value		Increment TTL by <value 1-255>\n");
25}
26
27static int TTL_parse(int c, char **argv, int invert, unsigned int *flags,
28                     const void *entry, struct xt_entry_target **target)
29{
30	struct ipt_TTL_info *info = (struct ipt_TTL_info *) (*target)->data;
31	unsigned int value;
32
33	if (*flags & IPT_TTL_USED) {
34		xtables_error(PARAMETER_PROBLEM,
35				"Can't specify TTL option twice");
36	}
37
38	if (!optarg)
39		xtables_error(PARAMETER_PROBLEM,
40				"TTL: You must specify a value");
41
42	if (xtables_check_inverse(optarg, &invert, NULL, 0, argv))
43		xtables_error(PARAMETER_PROBLEM,
44				"TTL: unexpected `!'");
45
46	if (!xtables_strtoui(optarg, NULL, &value, 0, UINT8_MAX))
47		xtables_error(PARAMETER_PROBLEM,
48		           "TTL: Expected value between 0 and 255");
49
50	switch (c) {
51
52		case '1':
53			info->mode = IPT_TTL_SET;
54			break;
55
56		case '2':
57			if (value == 0) {
58				xtables_error(PARAMETER_PROBLEM,
59					"TTL: decreasing by 0?");
60			}
61
62			info->mode = IPT_TTL_DEC;
63			break;
64
65		case '3':
66			if (value == 0) {
67				xtables_error(PARAMETER_PROBLEM,
68					"TTL: increasing by 0?");
69			}
70
71			info->mode = IPT_TTL_INC;
72			break;
73
74		default:
75			return 0;
76
77	}
78
79	info->ttl = value;
80	*flags |= IPT_TTL_USED;
81
82	return 1;
83}
84
85static void TTL_check(unsigned int flags)
86{
87	if (!(flags & IPT_TTL_USED))
88		xtables_error(PARAMETER_PROBLEM,
89				"TTL: You must specify an action");
90}
91
92static void TTL_save(const void *ip, const struct xt_entry_target *target)
93{
94	const struct ipt_TTL_info *info =
95		(struct ipt_TTL_info *) target->data;
96
97	switch (info->mode) {
98		case IPT_TTL_SET:
99			printf("--ttl-set ");
100			break;
101		case IPT_TTL_DEC:
102			printf("--ttl-dec ");
103			break;
104
105		case IPT_TTL_INC:
106			printf("--ttl-inc ");
107			break;
108	}
109	printf("%u ", info->ttl);
110}
111
112static void TTL_print(const void *ip, const struct xt_entry_target *target,
113                      int numeric)
114{
115	const struct ipt_TTL_info *info =
116		(struct ipt_TTL_info *) target->data;
117
118	printf("TTL ");
119	switch (info->mode) {
120		case IPT_TTL_SET:
121			printf("set to ");
122			break;
123		case IPT_TTL_DEC:
124			printf("decrement by ");
125			break;
126		case IPT_TTL_INC:
127			printf("increment by ");
128			break;
129	}
130	printf("%u ", info->ttl);
131}
132
133static const struct option TTL_opts[] = {
134	{ "ttl-set", 1, NULL, '1' },
135	{ "ttl-dec", 1, NULL, '2' },
136	{ "ttl-inc", 1, NULL, '3' },
137	{ .name = NULL }
138};
139
140static struct xtables_target ttl_tg_reg = {
141	.name		= "TTL",
142	.version	= XTABLES_VERSION,
143	.family		= NFPROTO_IPV4,
144	.size		= XT_ALIGN(sizeof(struct ipt_TTL_info)),
145	.userspacesize	= XT_ALIGN(sizeof(struct ipt_TTL_info)),
146	.help		= TTL_help,
147	.parse		= TTL_parse,
148	.final_check	= TTL_check,
149	.print		= TTL_print,
150	.save		= TTL_save,
151	.extra_opts	= TTL_opts,
152};
153
154void _init(void)
155{
156	xtables_register_target(&ttl_tg_reg);
157}
158