libip6t_HL.c revision 8b7c64d6ba156a99008fcd810cba874c73294333 
1/*
2 * IPv6 Hop Limit Target module
3 * Maciej Soltysiak <solt@dns.toxicfilms.tv>
4 * Based on HW's ttl target
5 * This program is distributed under the terms of GNU GPL
6 */
7
8#include <stdio.h>
9#include <string.h>
10#include <stdlib.h>
11#include <getopt.h>
12#include <ip6tables.h>
13
14#include <linux/netfilter_ipv6/ip6_tables.h>
15#include <linux/netfilter_ipv6/ip6t_HL.h>
16
17#define IP6T_HL_USED	1
18
19static void HL_help(void)
20{
21	printf(
22"HL target options\n"
23"  --hl-set value		Set HL to <value 0-255>\n"
24"  --hl-dec value		Decrement HL by <value 1-255>\n"
25"  --hl-inc value		Increment HL by <value 1-255>\n");
26}
27
28static int HL_parse(int c, char **argv, int invert, unsigned int *flags,
29                    const void *entry, struct xt_entry_target **target)
30{
31	struct ip6t_HL_info *info = (struct ip6t_HL_info *) (*target)->data;
32	unsigned int value;
33
34	if (*flags & IP6T_HL_USED) {
35		exit_error(PARAMETER_PROBLEM,
36				"Can't specify HL option twice");
37	}
38
39	if (!optarg)
40		exit_error(PARAMETER_PROBLEM,
41				"HL: You must specify a value");
42
43	if (check_inverse(optarg, &invert, NULL, 0))
44		exit_error(PARAMETER_PROBLEM,
45				"HL: unexpected `!'");
46
47	if (string_to_number(optarg, 0, 255, &value) == -1)
48		exit_error(PARAMETER_PROBLEM,
49		           "HL: Expected value between 0 and 255");
50
51	switch (c) {
52
53		case '1':
54			info->mode = IP6T_HL_SET;
55			break;
56
57		case '2':
58			if (value == 0) {
59				exit_error(PARAMETER_PROBLEM,
60					"HL: decreasing by 0?");
61			}
62
63			info->mode = IP6T_HL_DEC;
64			break;
65
66		case '3':
67			if (value == 0) {
68				exit_error(PARAMETER_PROBLEM,
69					"HL: increasing by 0?");
70			}
71
72			info->mode = IP6T_HL_INC;
73			break;
74
75		default:
76			return 0;
77
78	}
79
80	info->hop_limit = value;
81	*flags |= IP6T_HL_USED;
82
83	return 1;
84}
85
86static void HL_check(unsigned int flags)
87{
88	if (!(flags & IP6T_HL_USED))
89		exit_error(PARAMETER_PROBLEM,
90				"HL: You must specify an action");
91}
92
93static void HL_save(const void *ip, const struct xt_entry_target *target)
94{
95	const struct ip6t_HL_info *info =
96		(struct ip6t_HL_info *) target->data;
97
98	switch (info->mode) {
99		case IP6T_HL_SET:
100			printf("--hl-set ");
101			break;
102		case IP6T_HL_DEC:
103			printf("--hl-dec ");
104			break;
105
106		case IP6T_HL_INC:
107			printf("--hl-inc ");
108			break;
109	}
110	printf("%u ", info->hop_limit);
111}
112
113static void HL_print(const void *ip, const struct xt_entry_target *target,
114                     int numeric)
115{
116	const struct ip6t_HL_info *info =
117		(struct ip6t_HL_info *) target->data;
118
119	printf("HL ");
120	switch (info->mode) {
121		case IP6T_HL_SET:
122			printf("set to ");
123			break;
124		case IP6T_HL_DEC:
125			printf("decrement by ");
126			break;
127		case IP6T_HL_INC:
128			printf("increment by ");
129			break;
130	}
131	printf("%u ", info->hop_limit);
132}
133
134static const struct option HL_opts[] = {
135	{ "hl-set", 1, NULL, '1' },
136	{ "hl-dec", 1, NULL, '2' },
137	{ "hl-inc", 1, NULL, '3' },
138	{ .name = NULL }
139};
140
141static struct xtables_target hl_tg6_reg = {
142	.name 		= "HL",
143	.version	= XTABLES_VERSION,
144	.family		= PF_INET6,
145	.size		= XT_ALIGN(sizeof(struct ip6t_HL_info)),
146	.userspacesize	= XT_ALIGN(sizeof(struct ip6t_HL_info)),
147	.help		= HL_help,
148	.parse		= HL_parse,
149	.final_check	= HL_check,
150	.print		= HL_print,
151	.save		= HL_save,
152	.extra_opts	= HL_opts,
153};
154
155void _init(void)
156{
157	xtables_register_target(&hl_tg6_reg);
158}
159