libipt_REJECT.c revision 4008138e2b5248940265b160fae001d8954fae21 
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()
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
71help(void)
72{
73	printf(
74"REJECT options:\n"
75"--reject-with type              drop input packet and send back\n"
76"                                a reply packet according to type:\n");
77
78	print_reject_types();
79
80	printf("(*) See man page or read the INCOMPATIBILITES file for compatibility issues.\n");
81}
82
83static struct option opts[] = {
84	{ "reject-with", 1, 0, '1' },
85	{ 0 }
86};
87
88/* Allocate and initialize the target. */
89static void
90init(struct ipt_entry_target *t, unsigned int *nfcache)
91{
92	struct ipt_reject_info *reject = (struct ipt_reject_info *)t->data;
93
94	/* default */
95	reject->with = IPT_ICMP_PORT_UNREACHABLE;
96
97}
98
99/* Function which parses command options; returns true if it
100   ate an option */
101static int
102parse(int c, char **argv, int invert, unsigned int *flags,
103      const struct ipt_entry *entry,
104      struct ipt_entry_target **target)
105{
106	struct ipt_reject_info *reject = (struct ipt_reject_info *)(*target)->data;
107	unsigned int limit = sizeof(reject_table)/sizeof(struct reject_names);
108	unsigned int i;
109
110	switch(c) {
111	case '1':
112		if (check_inverse(optarg, &invert, NULL, 0))
113			exit_error(PARAMETER_PROBLEM,
114				   "Unexpected `!' after --reject-with");
115		for (i = 0; i < limit; i++) {
116			if ((strncasecmp(reject_table[i].name, optarg, strlen(optarg)) == 0)
117			    || (strncasecmp(reject_table[i].alias, optarg, strlen(optarg)) == 0)) {
118				reject->with = reject_table[i].with;
119				return 1;
120			}
121		}
122		/* This due to be dropped late in 2.4 pre-release cycle --RR */
123		if (strncasecmp("echo-reply", optarg, strlen(optarg)) == 0
124		    || strncasecmp("echoreply", optarg, strlen(optarg)) == 0)
125			fprintf(stderr, "--reject-with echo-reply no longer"
126				" supported\n");
127		exit_error(PARAMETER_PROBLEM, "unknown reject type `%s'",optarg);
128	default:
129		/* Fall through */
130		break;
131	}
132	return 0;
133}
134
135/* Final check; nothing. */
136static void final_check(unsigned int flags)
137{
138}
139
140/* Prints out ipt_reject_info. */
141static void
142print(const struct ipt_ip *ip,
143      const struct ipt_entry_target *target,
144      int numeric)
145{
146	const struct ipt_reject_info *reject
147		= (const struct ipt_reject_info *)target->data;
148	unsigned int i;
149
150	for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++) {
151		if (reject_table[i].with == reject->with)
152			break;
153	}
154	printf("reject-with %s ", reject_table[i].name);
155}
156
157/* Saves ipt_reject in parsable form to stdout. */
158static void save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
159{
160	const struct ipt_reject_info *reject
161		= (const struct ipt_reject_info *)target->data;
162	unsigned int i;
163
164	for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++)
165		if (reject_table[i].with == reject->with)
166			break;
167
168	printf("--reject-with %s ", reject_table[i].name);
169}
170
171static struct iptables_target reject = {
172	.next		= NULL,
173	.name		= "REJECT",
174	.version	= IPTABLES_VERSION,
175	.size		= IPT_ALIGN(sizeof(struct ipt_reject_info)),
176	.userspacesize	= IPT_ALIGN(sizeof(struct ipt_reject_info)),
177	.help		= &help,
178	.init		= &init,
179	.parse		= &parse,
180	.final_check	= &final_check,
181	.print		= &print,
182	.save		= &save,
183	.extra_opts	= opts
184};
185
186void ipt_REJECT_init(void)
187{
188	register_target(&reject);
189}
190