libipt_REDIRECT.c revision 1d5b63d12984d12c8d87242179855e17657be16d 
1/* Shared library add-on to iptables to add redirect 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#include <linux/netfilter/nf_nat.h>
10
11#define IPT_REDIRECT_OPT_DEST	0x01
12#define IPT_REDIRECT_OPT_RANDOM	0x02
13
14/* Function which prints out usage message. */
15static void REDIRECT_help(void)
16{
17	printf(
18"REDIRECT v%s options:\n"
19" --to-ports <port>[-<port>]\n"
20"				Port (range) to map to.\n\n",
21IPTABLES_VERSION);
22}
23
24static const struct option REDIRECT_opts[] = {
25	{ "to-ports", 1, NULL, '1' },
26	{ "random", 1, NULL, '2' },
27	{ }
28};
29
30/* Initialize the target. */
31static void REDIRECT_init(struct xt_entry_target *t)
32{
33	struct ip_nat_multi_range *mr = (struct ip_nat_multi_range *)t->data;
34
35	/* Actually, it's 0, but it's ignored at the moment. */
36	mr->rangesize = 1;
37
38}
39
40/* Parses ports */
41static void
42parse_ports(const char *arg, struct ip_nat_multi_range *mr)
43{
44	const char *dash;
45	int port;
46
47	mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
48
49	if (strchr(arg, '.'))
50		exit_error(PARAMETER_PROBLEM, "IP address not permitted\n");
51
52	port = atoi(arg);
53	if (port == 0 || port > 65535)
54		exit_error(PARAMETER_PROBLEM, "Port `%s' not valid\n", arg);
55
56	dash = strchr(arg, '-');
57	if (!dash) {
58		mr->range[0].min.tcp.port
59			= mr->range[0].max.tcp.port
60			= htons(port);
61	} else {
62		int maxport;
63
64		maxport = atoi(dash + 1);
65		if (maxport == 0 || maxport > 65535)
66			exit_error(PARAMETER_PROBLEM,
67				   "Port `%s' not valid\n", dash+1);
68		if (maxport < port)
69			/* People are stupid. */
70			exit_error(PARAMETER_PROBLEM,
71				   "Port range `%s' funky\n", arg);
72		mr->range[0].min.tcp.port = htons(port);
73		mr->range[0].max.tcp.port = htons(maxport);
74	}
75}
76
77/* Function which parses command options; returns true if it
78   ate an option */
79static int REDIRECT_parse(int c, char **argv, int invert, unsigned int *flags,
80                          const void *e, struct xt_entry_target **target)
81{
82	const struct ipt_entry *entry = e;
83	struct ip_nat_multi_range *mr
84		= (struct ip_nat_multi_range *)(*target)->data;
85	int portok;
86
87	if (entry->ip.proto == IPPROTO_TCP
88	    || entry->ip.proto == IPPROTO_UDP
89	    || entry->ip.proto == IPPROTO_ICMP)
90		portok = 1;
91	else
92		portok = 0;
93
94	switch (c) {
95	case '1':
96		if (!portok)
97			exit_error(PARAMETER_PROBLEM,
98				   "Need TCP or UDP with port specification");
99
100		if (check_inverse(optarg, &invert, NULL, 0))
101			exit_error(PARAMETER_PROBLEM,
102				   "Unexpected `!' after --to-ports");
103
104		parse_ports(optarg, mr);
105		if (*flags & IPT_REDIRECT_OPT_RANDOM)
106			mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM;
107		*flags |= IPT_REDIRECT_OPT_DEST;
108		return 1;
109
110	case '2':
111		if (*flags & IPT_REDIRECT_OPT_DEST) {
112			mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM;
113			*flags |= IPT_REDIRECT_OPT_RANDOM;
114		} else
115			*flags |= IPT_REDIRECT_OPT_RANDOM;
116		return 1;
117
118	default:
119		return 0;
120	}
121}
122
123/* Prints out the targinfo. */
124static void REDIRECT_print(const void *ip, const struct xt_entry_target *target,
125                           int numeric)
126{
127	struct ip_nat_multi_range *mr
128		= (struct ip_nat_multi_range *)target->data;
129	struct ip_nat_range *r = &mr->range[0];
130
131	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
132		printf("redir ports ");
133		printf("%hu", ntohs(r->min.tcp.port));
134		if (r->max.tcp.port != r->min.tcp.port)
135			printf("-%hu", ntohs(r->max.tcp.port));
136		printf(" ");
137		if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM)
138			printf("random ");
139	}
140}
141
142/* Saves the union ipt_targinfo in parsable form to stdout. */
143static void REDIRECT_save(const void *ip, const struct xt_entry_target *target)
144{
145	struct ip_nat_multi_range *mr
146		= (struct ip_nat_multi_range *)target->data;
147	struct ip_nat_range *r = &mr->range[0];
148
149	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
150		printf("--to-ports ");
151		printf("%hu", ntohs(r->min.tcp.port));
152		if (r->max.tcp.port != r->min.tcp.port)
153			printf("-%hu", ntohs(r->max.tcp.port));
154		printf(" ");
155		if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM)
156			printf("--random ");
157	}
158}
159
160static struct iptables_target redirect_target = {
161	.name		= "REDIRECT",
162	.version	= IPTABLES_VERSION,
163	.size		= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
164	.userspacesize	= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
165	.help		= REDIRECT_help,
166	.init		= REDIRECT_init,
167 	.parse		= REDIRECT_parse,
168	.print		= REDIRECT_print,
169	.save		= REDIRECT_save,
170	.extra_opts	= REDIRECT_opts,
171};
172
173void _init(void)
174{
175	register_target(&redirect_target);
176}
177