libip6t_HL.c revision d09b6d591ca7d7d7575cb6aa20384c9830f777ab 
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 <getopt.h>
9#include <stdbool.h>
10#include <stdio.h>
11#include <string.h>
12#include <stdlib.h>
13#include <xtables.h>
14
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		xtables_error(PARAMETER_PROBLEM,
36				"Can't specify HL option twice");
37	}
38
39	if (!optarg)
40		xtables_error(PARAMETER_PROBLEM,
41				"HL: You must specify a value");
42
43	if (xtables_check_inverse(optarg, &invert, NULL, 0, argv))
44		xtables_error(PARAMETER_PROBLEM,
45				"HL: unexpected `!'");
46
47	if (!xtables_strtoui(optarg, NULL, &value, 0, UINT8_MAX))
48		xtables_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				xtables_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				xtables_error(PARAMETER_PROBLEM,
69					"HL: increasing by 0?");
70			}
71
72			info->mode = IP6T_HL_INC;
73			break;
74	}
75
76	info->hop_limit = value;
77	*flags |= IP6T_HL_USED;
78
79	return 1;
80}
81
82static void HL_check(unsigned int flags)
83{
84	if (!(flags & IP6T_HL_USED))
85		xtables_error(PARAMETER_PROBLEM,
86				"HL: You must specify an action");
87}
88
89static void HL_save(const void *ip, const struct xt_entry_target *target)
90{
91	const struct ip6t_HL_info *info =
92		(struct ip6t_HL_info *) target->data;
93
94	switch (info->mode) {
95		case IP6T_HL_SET:
96			printf("--hl-set ");
97			break;
98		case IP6T_HL_DEC:
99			printf("--hl-dec ");
100			break;
101
102		case IP6T_HL_INC:
103			printf("--hl-inc ");
104			break;
105	}
106	printf("%u ", info->hop_limit);
107}
108
109static void HL_print(const void *ip, const struct xt_entry_target *target,
110                     int numeric)
111{
112	const struct ip6t_HL_info *info =
113		(struct ip6t_HL_info *) target->data;
114
115	printf("HL ");
116	switch (info->mode) {
117		case IP6T_HL_SET:
118			printf("set to ");
119			break;
120		case IP6T_HL_DEC:
121			printf("decrement by ");
122			break;
123		case IP6T_HL_INC:
124			printf("increment by ");
125			break;
126	}
127	printf("%u ", info->hop_limit);
128}
129
130static const struct option HL_opts[] = {
131	{.name = "hl-set", .has_arg = true, .val = '1'},
132	{.name = "hl-dec", .has_arg = true, .val = '2'},
133	{.name = "hl-inc", .has_arg = true, .val = '3'},
134	XT_GETOPT_TABLEEND,
135};
136
137static struct xtables_target hl_tg6_reg = {
138	.name 		= "HL",
139	.version	= XTABLES_VERSION,
140	.family		= NFPROTO_IPV6,
141	.size		= XT_ALIGN(sizeof(struct ip6t_HL_info)),
142	.userspacesize	= XT_ALIGN(sizeof(struct ip6t_HL_info)),
143	.help		= HL_help,
144	.parse		= HL_parse,
145	.final_check	= HL_check,
146	.print		= HL_print,
147	.save		= HL_save,
148	.extra_opts	= HL_opts,
149};
150
151void _init(void)
152{
153	xtables_register_target(&hl_tg6_reg);
154}
155