libipt_REJECT.c revision 1d5b63d12984d12c8d87242179855e17657be16d 
1/* Shared library add-on to iptables to add customized REJECT support.
2 *
3 * (C) 2000 Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
4 */
5#include <stdio.h>
6#include <string.h>
7#include <stdlib.h>
8#include <getopt.h>
9#include <iptables.h>
10#include <linux/netfilter_ipv4/ip_tables.h>
11#include <linux/netfilter_ipv4/ipt_REJECT.h>
12#include <linux/version.h>
13
14/* If we are compiling against a kernel that does not support
15 * IPT_ICMP_ADMIN_PROHIBITED, we are emulating it.
16 * The result will be a plain DROP of the packet instead of
17 * reject. -- Maciej Soltysiak <solt@dns.toxicfilms.tv>
18 */
19#ifndef IPT_ICMP_ADMIN_PROHIBITED
20#define IPT_ICMP_ADMIN_PROHIBITED	IPT_TCP_RESET + 1
21#endif
22
23struct reject_names {
24	const char *name;
25	const char *alias;
26	enum ipt_reject_with with;
27	const char *desc;
28};
29
30static const struct reject_names reject_table[] = {
31	{"icmp-net-unreachable", "net-unreach",
32		IPT_ICMP_NET_UNREACHABLE, "ICMP network unreachable"},
33	{"icmp-host-unreachable", "host-unreach",
34		IPT_ICMP_HOST_UNREACHABLE, "ICMP host unreachable"},
35	{"icmp-proto-unreachable", "proto-unreach",
36		IPT_ICMP_PROT_UNREACHABLE, "ICMP protocol unreachable"},
37	{"icmp-port-unreachable", "port-unreach",
38		IPT_ICMP_PORT_UNREACHABLE, "ICMP port unreachable (default)"},
39#if 0
40	{"echo-reply", "echoreply",
41	 IPT_ICMP_ECHOREPLY, "for ICMP echo only: faked ICMP echo reply"},
42#endif
43	{"icmp-net-prohibited", "net-prohib",
44	 IPT_ICMP_NET_PROHIBITED, "ICMP network prohibited"},
45	{"icmp-host-prohibited", "host-prohib",
46	 IPT_ICMP_HOST_PROHIBITED, "ICMP host prohibited"},
47	{"tcp-reset", "tcp-rst",
48	 IPT_TCP_RESET, "TCP RST packet"},
49	{"icmp-admin-prohibited", "admin-prohib",
50	 IPT_ICMP_ADMIN_PROHIBITED, "ICMP administratively prohibited (*)"}
51};
52
53static void
54print_reject_types(void)
55{
56	unsigned int i;
57
58	printf("Valid reject types:\n");
59
60	for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++) {
61		printf("    %-25s\t%s\n", reject_table[i].name, reject_table[i].desc);
62		printf("    %-25s\talias\n", reject_table[i].alias);
63	}
64	printf("\n");
65}
66
67/* Saves the union ipt_targinfo in parsable form to stdout. */
68
69/* Function which prints out usage message. */
70static void REJECT_help(void)
71{
72	printf(
73"REJECT options:\n"
74"--reject-with type              drop input packet and send back\n"
75"                                a reply packet according to type:\n");
76
77	print_reject_types();
78
79	printf("(*) See man page or read the INCOMPATIBILITES file for compatibility issues.\n");
80}
81
82static const struct option REJECT_opts[] = {
83	{ "reject-with", 1, NULL, '1' },
84	{ }
85};
86
87/* Allocate and initialize the target. */
88static void REJECT_init(struct xt_entry_target *t)
89{
90	struct ipt_reject_info *reject = (struct ipt_reject_info *)t->data;
91
92	/* default */
93	reject->with = IPT_ICMP_PORT_UNREACHABLE;
94
95}
96
97/* Function which parses command options; returns true if it
98   ate an option */
99static int REJECT_parse(int c, char **argv, int invert, unsigned int *flags,
100                        const void *entry, struct xt_entry_target **target)
101{
102	struct ipt_reject_info *reject = (struct ipt_reject_info *)(*target)->data;
103	unsigned int limit = sizeof(reject_table)/sizeof(struct reject_names);
104	unsigned int i;
105
106	switch(c) {
107	case '1':
108		if (check_inverse(optarg, &invert, NULL, 0))
109			exit_error(PARAMETER_PROBLEM,
110				   "Unexpected `!' after --reject-with");
111		for (i = 0; i < limit; i++) {
112			if ((strncasecmp(reject_table[i].name, optarg, strlen(optarg)) == 0)
113			    || (strncasecmp(reject_table[i].alias, optarg, strlen(optarg)) == 0)) {
114				reject->with = reject_table[i].with;
115				return 1;
116			}
117		}
118		/* This due to be dropped late in 2.4 pre-release cycle --RR */
119		if (strncasecmp("echo-reply", optarg, strlen(optarg)) == 0
120		    || strncasecmp("echoreply", optarg, strlen(optarg)) == 0)
121			fprintf(stderr, "--reject-with echo-reply no longer"
122				" supported\n");
123		exit_error(PARAMETER_PROBLEM, "unknown reject type `%s'",optarg);
124	default:
125		/* Fall through */
126		break;
127	}
128	return 0;
129}
130
131/* Prints out ipt_reject_info. */
132static void REJECT_print(const void *ip, const struct xt_entry_target *target,
133                         int numeric)
134{
135	const struct ipt_reject_info *reject
136		= (const struct ipt_reject_info *)target->data;
137	unsigned int i;
138
139	for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++) {
140		if (reject_table[i].with == reject->with)
141			break;
142	}
143	printf("reject-with %s ", reject_table[i].name);
144}
145
146/* Saves ipt_reject in parsable form to stdout. */
147static void REJECT_save(const void *ip, const struct xt_entry_target *target)
148{
149	const struct ipt_reject_info *reject
150		= (const struct ipt_reject_info *)target->data;
151	unsigned int i;
152
153	for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++)
154		if (reject_table[i].with == reject->with)
155			break;
156
157	printf("--reject-with %s ", reject_table[i].name);
158}
159
160static struct iptables_target reject_target = {
161	.name		= "REJECT",
162	.version	= IPTABLES_VERSION,
163	.size		= IPT_ALIGN(sizeof(struct ipt_reject_info)),
164	.userspacesize	= IPT_ALIGN(sizeof(struct ipt_reject_info)),
165	.help		= REJECT_help,
166	.init		= REJECT_init,
167	.parse		= REJECT_parse,
168	.print		= REJECT_print,
169	.save		= REJECT_save,
170	.extra_opts	= REJECT_opts,
171};
172
173void _init(void)
174{
175	register_target(&reject_target);
176}
177