libxt_udp.c revision 7ac405297ec38449b30e3b05fd6bf2082fd3d803 
1/* Shared library add-on to iptables to add UDP support. */
2#include <stdbool.h>
3#include <stdio.h>
4#include <netdb.h>
5#include <string.h>
6#include <stdlib.h>
7#include <getopt.h>
8#include <netinet/in.h>
9#include <xtables.h>
10#include <linux/netfilter/xt_tcpudp.h>
11
12static void udp_help(void)
13{
14	printf(
15"udp match options:\n"
16"[!] --source-port port[:port]\n"
17" --sport ...\n"
18"				match source port(s)\n"
19"[!] --destination-port port[:port]\n"
20" --dport ...\n"
21"				match destination port(s)\n");
22}
23
24static const struct option udp_opts[] = {
25	{.name = "source-port",      .has_arg = true, .val = '1'},
26	{.name = "sport",            .has_arg = true, .val = '1'}, /* synonym */
27	{.name = "destination-port", .has_arg = true, .val = '2'},
28	{.name = "dport",            .has_arg = true, .val = '2'}, /* synonym */
29	XT_GETOPT_TABLEEND,
30};
31
32static void
33parse_udp_ports(const char *portstring, uint16_t *ports)
34{
35	char *buffer;
36	char *cp;
37
38	buffer = strdup(portstring);
39	if ((cp = strchr(buffer, ':')) == NULL)
40		ports[0] = ports[1] = xtables_parse_port(buffer, "udp");
41	else {
42		*cp = '\0';
43		cp++;
44
45		ports[0] = buffer[0] ? xtables_parse_port(buffer, "udp") : 0;
46		ports[1] = cp[0] ? xtables_parse_port(cp, "udp") : 0xFFFF;
47
48		if (ports[0] > ports[1])
49			xtables_error(PARAMETER_PROBLEM,
50				   "invalid portrange (min > max)");
51	}
52	free(buffer);
53}
54
55static void udp_init(struct xt_entry_match *m)
56{
57	struct xt_udp *udpinfo = (struct xt_udp *)m->data;
58
59	udpinfo->spts[1] = udpinfo->dpts[1] = 0xFFFF;
60}
61
62#define UDP_SRC_PORTS 0x01
63#define UDP_DST_PORTS 0x02
64
65static int
66udp_parse(int c, char **argv, int invert, unsigned int *flags,
67          const void *entry, struct xt_entry_match **match)
68{
69	struct xt_udp *udpinfo = (struct xt_udp *)(*match)->data;
70
71	switch (c) {
72	case '1':
73		if (*flags & UDP_SRC_PORTS)
74			xtables_error(PARAMETER_PROBLEM,
75				   "Only one `--source-port' allowed");
76		xtables_check_inverse(optarg, &invert, &optind, 0, argv);
77		parse_udp_ports(optarg, udpinfo->spts);
78		if (invert)
79			udpinfo->invflags |= XT_UDP_INV_SRCPT;
80		*flags |= UDP_SRC_PORTS;
81		break;
82
83	case '2':
84		if (*flags & UDP_DST_PORTS)
85			xtables_error(PARAMETER_PROBLEM,
86				   "Only one `--destination-port' allowed");
87		xtables_check_inverse(optarg, &invert, &optind, 0, argv);
88		parse_udp_ports(optarg, udpinfo->dpts);
89		if (invert)
90			udpinfo->invflags |= XT_UDP_INV_DSTPT;
91		*flags |= UDP_DST_PORTS;
92		break;
93
94	default:
95		return 0;
96	}
97
98	return 1;
99}
100
101static char *
102port_to_service(int port)
103{
104	struct servent *service;
105
106	if ((service = getservbyport(htons(port), "udp")))
107		return service->s_name;
108
109	return NULL;
110}
111
112static void
113print_port(uint16_t port, int numeric)
114{
115	char *service;
116
117	if (numeric || (service = port_to_service(port)) == NULL)
118		printf("%u", port);
119	else
120		printf("%s", service);
121}
122
123static void
124print_ports(const char *name, uint16_t min, uint16_t max,
125	    int invert, int numeric)
126{
127	const char *inv = invert ? "!" : "";
128
129	if (min != 0 || max != 0xFFFF || invert) {
130		printf("%s", name);
131		if (min == max) {
132			printf(":%s", inv);
133			print_port(min, numeric);
134		} else {
135			printf("s:%s", inv);
136			print_port(min, numeric);
137			printf(":");
138			print_port(max, numeric);
139		}
140		printf(" ");
141	}
142}
143
144static void
145udp_print(const void *ip, const struct xt_entry_match *match, int numeric)
146{
147	const struct xt_udp *udp = (struct xt_udp *)match->data;
148
149	printf("udp ");
150	print_ports("spt", udp->spts[0], udp->spts[1],
151		    udp->invflags & XT_UDP_INV_SRCPT,
152		    numeric);
153	print_ports("dpt", udp->dpts[0], udp->dpts[1],
154		    udp->invflags & XT_UDP_INV_DSTPT,
155		    numeric);
156	if (udp->invflags & ~XT_UDP_INV_MASK)
157		printf("Unknown invflags: 0x%X ",
158		       udp->invflags & ~XT_UDP_INV_MASK);
159}
160
161static void udp_save(const void *ip, const struct xt_entry_match *match)
162{
163	const struct xt_udp *udpinfo = (struct xt_udp *)match->data;
164
165	if (udpinfo->spts[0] != 0
166	    || udpinfo->spts[1] != 0xFFFF) {
167		if (udpinfo->invflags & XT_UDP_INV_SRCPT)
168			printf("! ");
169		if (udpinfo->spts[0]
170		    != udpinfo->spts[1])
171			printf("--sport %u:%u ",
172			       udpinfo->spts[0],
173			       udpinfo->spts[1]);
174		else
175			printf("--sport %u ",
176			       udpinfo->spts[0]);
177	}
178
179	if (udpinfo->dpts[0] != 0
180	    || udpinfo->dpts[1] != 0xFFFF) {
181		if (udpinfo->invflags & XT_UDP_INV_DSTPT)
182			printf("! ");
183		if (udpinfo->dpts[0]
184		    != udpinfo->dpts[1])
185			printf("--dport %u:%u ",
186			       udpinfo->dpts[0],
187			       udpinfo->dpts[1]);
188		else
189			printf("--dport %u ",
190			       udpinfo->dpts[0]);
191	}
192}
193
194static struct xtables_match udp_match = {
195	.family		= NFPROTO_UNSPEC,
196	.name		= "udp",
197	.version	= XTABLES_VERSION,
198	.size		= XT_ALIGN(sizeof(struct xt_udp)),
199	.userspacesize	= XT_ALIGN(sizeof(struct xt_udp)),
200	.help		= udp_help,
201	.init		= udp_init,
202	.parse		= udp_parse,
203	.print		= udp_print,
204	.save		= udp_save,
205	.extra_opts	= udp_opts,
206};
207
208void
209_init(void)
210{
211	xtables_register_match(&udp_match);
212}
213