libipt_REJECT.c revision 5a52c517ebb2c7421f57b0f00f2de6697cdd7a9c 
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-reset",
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	/* Can't cache this */
98	*nfcache |= NFC_UNKNOWN;
99}
100
101/* Function which parses command options; returns true if it
102   ate an option */
103static int
104parse(int c, char **argv, int invert, unsigned int *flags,
105      const struct ipt_entry *entry,
106      struct ipt_entry_target **target)
107{
108	struct ipt_reject_info *reject = (struct ipt_reject_info *)(*target)->data;
109	unsigned int limit = sizeof(reject_table)/sizeof(struct reject_names);
110	unsigned int i;
111
112	switch(c) {
113	case '1':
114		if (check_inverse(optarg, &invert, NULL, 0))
115			exit_error(PARAMETER_PROBLEM,
116				   "Unexpected `!' after --reject-with");
117		for (i = 0; i < limit; i++) {
118			if ((strncasecmp(reject_table[i].name, optarg, strlen(optarg)) == 0)
119			    || (strncasecmp(reject_table[i].alias, optarg, strlen(optarg)) == 0)) {
120				reject->with = reject_table[i].with;
121				return 1;
122			}
123		}
124		/* This due to be dropped late in 2.4 pre-release cycle --RR */
125		if (strncasecmp("echo-reply", optarg, strlen(optarg)) == 0
126		    || strncasecmp("echoreply", optarg, strlen(optarg)) == 0)
127			fprintf(stderr, "--reject-with echo-reply no longer"
128				" supported\n");
129		exit_error(PARAMETER_PROBLEM, "unknown reject type `%s'",optarg);
130	default:
131		/* Fall through */
132		break;
133	}
134	return 0;
135}
136
137/* Final check; nothing. */
138static void final_check(unsigned int flags)
139{
140}
141
142/* Prints out ipt_reject_info. */
143static void
144print(const struct ipt_ip *ip,
145      const struct ipt_entry_target *target,
146      int numeric)
147{
148	const struct ipt_reject_info *reject
149		= (const struct ipt_reject_info *)target->data;
150	unsigned int i;
151
152	for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++) {
153		if (reject_table[i].with == reject->with)
154			break;
155	}
156	printf("reject-with %s ", reject_table[i].name);
157}
158
159/* Saves ipt_reject in parsable form to stdout. */
160static void save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
161{
162	const struct ipt_reject_info *reject
163		= (const struct ipt_reject_info *)target->data;
164	unsigned int i;
165
166	for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++)
167		if (reject_table[i].with == reject->with)
168			break;
169
170	printf("--reject-with %s ", reject_table[i].name);
171}
172
173static
174struct iptables_target reject
175= { NULL,
176    "REJECT",
177    IPTABLES_VERSION,
178    IPT_ALIGN(sizeof(struct ipt_reject_info)),
179    IPT_ALIGN(sizeof(struct ipt_reject_info)),
180    &help,
181    &init,
182    &parse,
183    &final_check,
184    &print,
185    &save,
186    opts
187};
188
189void _init(void)
190{
191	register_target(&reject);
192}
193