libipt_icmp.c revision ea146a982e26c42f9954f140276f8deeb2edbe98 
1/* Shared library add-on to iptables to add ICMP support. */
2#include <stdio.h>
3#include <netdb.h>
4#include <string.h>
5#include <stdlib.h>
6#include <getopt.h>
7#include <iptables.h>
8#include <linux/netfilter_ipv4/ip_tables.h>
9
10/* special hack for icmp-type 'any':
11 * Up to kernel <=2.4.20 the problem was:
12 * '-p icmp ' matches all icmp packets
13 * '-p icmp -m icmp' matches _only_ ICMP type 0 :(
14 * This is now fixed by initializing the field * to icmp type 0xFF
15 * See: https://bugzilla.netfilter.org/cgi-bin/bugzilla/show_bug.cgi?id=37
16 */
17
18struct icmp_names {
19	const char *name;
20	u_int8_t type;
21	u_int8_t code_min, code_max;
22};
23
24static const struct icmp_names icmp_codes[] = {
25	{ "any", 0xFF, 0, 0xFF },
26	{ "echo-reply", 0, 0, 0xFF },
27	/* Alias */ { "pong", 0, 0, 0xFF },
28
29	{ "destination-unreachable", 3, 0, 0xFF },
30	{   "network-unreachable", 3, 0, 0 },
31	{   "host-unreachable", 3, 1, 1 },
32	{   "protocol-unreachable", 3, 2, 2 },
33	{   "port-unreachable", 3, 3, 3 },
34	{   "fragmentation-needed", 3, 4, 4 },
35	{   "source-route-failed", 3, 5, 5 },
36	{   "network-unknown", 3, 6, 6 },
37	{   "host-unknown", 3, 7, 7 },
38	{   "network-prohibited", 3, 9, 9 },
39	{   "host-prohibited", 3, 10, 10 },
40	{   "TOS-network-unreachable", 3, 11, 11 },
41	{   "TOS-host-unreachable", 3, 12, 12 },
42	{   "communication-prohibited", 3, 13, 13 },
43	{   "host-precedence-violation", 3, 14, 14 },
44	{   "precedence-cutoff", 3, 15, 15 },
45
46	{ "source-quench", 4, 0, 0xFF },
47
48	{ "redirect", 5, 0, 0xFF },
49	{   "network-redirect", 5, 0, 0 },
50	{   "host-redirect", 5, 1, 1 },
51	{   "TOS-network-redirect", 5, 2, 2 },
52	{   "TOS-host-redirect", 5, 3, 3 },
53
54	{ "echo-request", 8, 0, 0xFF },
55	/* Alias */ { "ping", 8, 0, 0xFF },
56
57	{ "router-advertisement", 9, 0, 0xFF },
58
59	{ "router-solicitation", 10, 0, 0xFF },
60
61	{ "time-exceeded", 11, 0, 0xFF },
62	/* Alias */ { "ttl-exceeded", 11, 0, 0xFF },
63	{   "ttl-zero-during-transit", 11, 0, 0 },
64	{   "ttl-zero-during-reassembly", 11, 1, 1 },
65
66	{ "parameter-problem", 12, 0, 0xFF },
67	{   "ip-header-bad", 12, 0, 0 },
68	{   "required-option-missing", 12, 1, 1 },
69
70	{ "timestamp-request", 13, 0, 0xFF },
71
72	{ "timestamp-reply", 14, 0, 0xFF },
73
74	{ "address-mask-request", 17, 0, 0xFF },
75
76	{ "address-mask-reply", 18, 0, 0xFF }
77};
78
79static void
80print_icmptypes()
81{
82	unsigned int i;
83	printf("Valid ICMP Types:");
84
85	for (i = 0; i < sizeof(icmp_codes)/sizeof(struct icmp_names); i++) {
86		if (i && icmp_codes[i].type == icmp_codes[i-1].type) {
87			if (icmp_codes[i].code_min == icmp_codes[i-1].code_min
88			    && (icmp_codes[i].code_max
89				== icmp_codes[i-1].code_max))
90				printf(" (%s)", icmp_codes[i].name);
91			else
92				printf("\n   %s", icmp_codes[i].name);
93		}
94		else
95			printf("\n%s", icmp_codes[i].name);
96	}
97	printf("\n");
98}
99
100/* Function which prints out usage message. */
101static void
102help(void)
103{
104	printf(
105"ICMP v%s options:\n"
106" --icmp-type [!] typename	match icmp type\n"
107"				(or numeric type or type/code)\n"
108"\n", IPTABLES_VERSION);
109	print_icmptypes();
110}
111
112static const struct option opts[] = {
113	{ "icmp-type", 1, 0, '1' },
114	{0}
115};
116
117static void
118parse_icmp(const char *icmptype, u_int8_t *type, u_int8_t code[])
119{
120	unsigned int limit = sizeof(icmp_codes)/sizeof(struct icmp_names);
121	unsigned int match = limit;
122	unsigned int i;
123
124	for (i = 0; i < limit; i++) {
125		if (strncasecmp(icmp_codes[i].name, icmptype, strlen(icmptype))
126		    == 0) {
127			if (match != limit)
128				exit_error(PARAMETER_PROBLEM,
129					   "Ambiguous ICMP type `%s':"
130					   " `%s' or `%s'?",
131					   icmptype,
132					   icmp_codes[match].name,
133					   icmp_codes[i].name);
134			match = i;
135		}
136	}
137
138	if (match != limit) {
139		*type = icmp_codes[match].type;
140		code[0] = icmp_codes[match].code_min;
141		code[1] = icmp_codes[match].code_max;
142	} else {
143		char *slash;
144		char buffer[strlen(icmptype) + 1];
145		unsigned int number;
146
147		strcpy(buffer, icmptype);
148		slash = strchr(buffer, '/');
149
150		if (slash)
151			*slash = '\0';
152
153		if (string_to_number(buffer, 0, 255, &number) == -1)
154			exit_error(PARAMETER_PROBLEM,
155				   "Invalid ICMP type `%s'\n", buffer);
156		*type = number;
157		if (slash) {
158			if (string_to_number(slash+1, 0, 255, &number) == -1)
159				exit_error(PARAMETER_PROBLEM,
160					   "Invalid ICMP code `%s'\n",
161					   slash+1);
162			code[0] = code[1] = number;
163		} else {
164			code[0] = 0;
165			code[1] = 0xFF;
166		}
167	}
168}
169
170/* Initialize the match. */
171static void
172init(struct xt_entry_match *m)
173{
174	struct ipt_icmp *icmpinfo = (struct ipt_icmp *)m->data;
175
176	icmpinfo->type = 0xFF;
177	icmpinfo->code[1] = 0xFF;
178}
179
180/* Function which parses command options; returns true if it
181   ate an option */
182static int
183parse(int c, char **argv, int invert, unsigned int *flags,
184      const void *entry,
185      struct xt_entry_match **match)
186{
187	struct ipt_icmp *icmpinfo = (struct ipt_icmp *)(*match)->data;
188
189	switch (c) {
190	case '1':
191		if (*flags == 1)
192			exit_error(PARAMETER_PROBLEM,
193				   "icmp match: only use --icmp-type once!");
194		check_inverse(optarg, &invert, &optind, 0);
195		parse_icmp(argv[optind-1], &icmpinfo->type,
196			   icmpinfo->code);
197		if (invert)
198			icmpinfo->invflags |= IPT_ICMP_INV;
199		*flags = 1;
200		break;
201
202	default:
203		return 0;
204	}
205
206	return 1;
207}
208
209static void print_icmptype(u_int8_t type,
210			   u_int8_t code_min, u_int8_t code_max,
211			   int invert,
212			   int numeric)
213{
214	if (!numeric) {
215		unsigned int i;
216
217		for (i = 0;
218		     i < sizeof(icmp_codes)/sizeof(struct icmp_names);
219		     i++) {
220			if (icmp_codes[i].type == type
221			    && icmp_codes[i].code_min == code_min
222			    && icmp_codes[i].code_max == code_max)
223				break;
224		}
225
226		if (i != sizeof(icmp_codes)/sizeof(struct icmp_names)) {
227			printf("%s%s ",
228			       invert ? "!" : "",
229			       icmp_codes[i].name);
230			return;
231		}
232	}
233
234	if (invert)
235		printf("!");
236
237	printf("type %u", type);
238	if (code_min == 0 && code_max == 0xFF)
239		printf(" ");
240	else if (code_min == code_max)
241		printf(" code %u ", code_min);
242	else
243		printf(" codes %u-%u ", code_min, code_max);
244}
245
246/* Prints out the union ipt_matchinfo. */
247static void
248print(const void *ip,
249      const struct xt_entry_match *match,
250      int numeric)
251{
252	const struct ipt_icmp *icmp = (struct ipt_icmp *)match->data;
253
254	printf("icmp ");
255	print_icmptype(icmp->type, icmp->code[0], icmp->code[1],
256		       icmp->invflags & IPT_ICMP_INV,
257		       numeric);
258
259	if (icmp->invflags & ~IPT_ICMP_INV)
260		printf("Unknown invflags: 0x%X ",
261		       icmp->invflags & ~IPT_ICMP_INV);
262}
263
264/* Saves the match in parsable form to stdout. */
265static void save(const void *ip, const struct xt_entry_match *match)
266{
267	const struct ipt_icmp *icmp = (struct ipt_icmp *)match->data;
268
269	if (icmp->invflags & IPT_ICMP_INV)
270		printf("! ");
271
272	/* special hack for 'any' case */
273	if (icmp->type == 0xFF) {
274		printf("--icmp-type any ");
275	} else {
276		printf("--icmp-type %u", icmp->type);
277		if (icmp->code[0] != 0 || icmp->code[1] != 0xFF)
278			printf("/%u", icmp->code[0]);
279		printf(" ");
280	}
281}
282
283/* Final check; we don't care. We can pass 0xFF to match any type */
284static void final_check(unsigned int flags)
285{
286}
287
288static struct iptables_match icmp = {
289	.name		= "icmp",
290	.version	= IPTABLES_VERSION,
291	.size		= IPT_ALIGN(sizeof(struct ipt_icmp)),
292	.userspacesize	= IPT_ALIGN(sizeof(struct ipt_icmp)),
293	.help		= &help,
294	.init		= &init,
295	.parse		= &parse,
296	.final_check	= &final_check,
297	.print		= &print,
298	.save		= &save,
299	.extra_opts	= opts
300};
301
302void _init(void)
303{
304	register_match(&icmp);
305}
306