libip6t_hl.c revision 03d99486d8283552705b58dc55b6085dffc38792 
1/*
2 * IPv6 Hop Limit matching module
3 * Maciej Soltysiak <solt@dns.toxicfilms.tv>
4 * Based on HW's ttl match
5 * This program is released under the terms of GNU GPL
6 * Cleanups by Stephane Ouellette <ouellettes@videotron.ca>
7 */
8
9#include <stdio.h>
10#include <stdlib.h>
11#include <string.h>
12#include <getopt.h>
13#include <ip6tables.h>
14
15#include <linux/netfilter_ipv6/ip6_tables.h>
16#include <linux/netfilter_ipv6/ip6t_hl.h>
17
18static void hl_help(void)
19{
20	printf(
21"hl match options:\n"
22"[!] --hl-eq value	Match hop limit value\n"
23"  --hl-lt value	Match HL < value\n"
24"  --hl-gt value	Match HL > value\n");
25}
26
27static int hl_parse(int c, char **argv, int invert, unsigned int *flags,
28                    const void *entry, struct xt_entry_match **match)
29{
30	struct ip6t_hl_info *info = (struct ip6t_hl_info *) (*match)->data;
31	u_int8_t value;
32
33	check_inverse(optarg, &invert, &optind, 0);
34	value = atoi(argv[optind-1]);
35
36	if (*flags)
37		exit_error(PARAMETER_PROBLEM,
38				"Can't specify HL option twice");
39
40	if (!optarg)
41		exit_error(PARAMETER_PROBLEM,
42				"hl: You must specify a value");
43	switch (c) {
44		case '2':
45			if (invert)
46				info->mode = IP6T_HL_NE;
47			else
48				info->mode = IP6T_HL_EQ;
49
50			/* is 0 allowed? */
51			info->hop_limit = value;
52			*flags = 1;
53
54			break;
55		case '3':
56			if (invert)
57				exit_error(PARAMETER_PROBLEM,
58						"hl: unexpected `!'");
59
60			info->mode = IP6T_HL_LT;
61			info->hop_limit = value;
62			*flags = 1;
63
64			break;
65		case '4':
66			if (invert)
67				exit_error(PARAMETER_PROBLEM,
68						"hl: unexpected `!'");
69
70			info->mode = IP6T_HL_GT;
71			info->hop_limit = value;
72			*flags = 1;
73
74			break;
75		default:
76			return 0;
77	}
78
79	return 1;
80}
81
82static void hl_check(unsigned int flags)
83{
84	if (!flags)
85		exit_error(PARAMETER_PROBLEM,
86			"HL match: You must specify one of "
87			"`--hl-eq', `--hl-lt', `--hl-gt'");
88}
89
90static void hl_print(const void *ip, const struct xt_entry_match *match,
91                     int numeric)
92{
93	static const char *op[] = {
94		[IP6T_HL_EQ] = "==",
95		[IP6T_HL_NE] = "!=",
96		[IP6T_HL_LT] = "<",
97		[IP6T_HL_GT] = ">" };
98
99	const struct ip6t_hl_info *info =
100		(struct ip6t_hl_info *) match->data;
101
102	printf("HL match HL %s %u ", op[info->mode], info->hop_limit);
103}
104
105static void hl_save(const void *ip, const struct xt_entry_match *match)
106{
107	static const char *op[] = {
108		[IP6T_HL_EQ] = "eq",
109		[IP6T_HL_NE] = "eq !",
110		[IP6T_HL_LT] = "lt",
111		[IP6T_HL_GT] = "gt" };
112
113	const struct ip6t_hl_info *info =
114		(struct ip6t_hl_info *) match->data;
115
116	printf("--hl-%s %u ", op[info->mode], info->hop_limit);
117}
118
119static const struct option hl_opts[] = {
120	{ .name = "hl",    .has_arg = 1, .val = '2' },
121	{ .name = "hl-eq", .has_arg = 1, .val = '2' },
122	{ .name = "hl-lt", .has_arg = 1, .val = '3' },
123	{ .name = "hl-gt", .has_arg = 1, .val = '4' },
124	{ .name = NULL }
125};
126
127static struct xtables_match hl_mt6_reg = {
128	.name          = "hl",
129	.version       = XTABLES_VERSION,
130	.family        = NFPROTO_IPV6,
131	.size          = XT_ALIGN(sizeof(struct ip6t_hl_info)),
132	.userspacesize = XT_ALIGN(sizeof(struct ip6t_hl_info)),
133	.help          = hl_help,
134	.parse         = hl_parse,
135	.final_check   = hl_check,
136	.print         = hl_print,
137	.save          = hl_save,
138	.extra_opts    = hl_opts,
139};
140
141
142void _init(void)
143{
144	xtables_register_match(&hl_mt6_reg);
145}
146