libipt_REDIRECT.c revision 4008138e2b5248940265b160fae001d8954fae21 
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_ipv4/ip_nat_rule.h>
10#include <netinet/in.h>
11
12/* Function which prints out usage message. */
13static void
14help(void)
15{
16	printf(
17"REDIRECT v%s options:\n"
18" --to-ports <port>[-<port>]\n"
19"				Port (range) to map to.\n\n",
20IPTABLES_VERSION);
21}
22
23static struct option opts[] = {
24	{ "to-ports", 1, 0, '1' },
25	{ 0 }
26};
27
28/* Initialize the target. */
29static void
30init(struct ipt_entry_target *t, unsigned int *nfcache)
31{
32	struct ip_nat_multi_range *mr = (struct ip_nat_multi_range *)t->data;
33
34	/* Actually, it's 0, but it's ignored at the moment. */
35	mr->rangesize = 1;
36
37}
38
39/* Parses ports */
40static void
41parse_ports(const char *arg, struct ip_nat_multi_range *mr)
42{
43	const char *dash;
44	int port;
45
46	mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
47
48	if (strchr(arg, '.'))
49		exit_error(PARAMETER_PROBLEM, "IP address not permitted\n");
50
51	port = atoi(arg);
52	if (port == 0 || port > 65535)
53		exit_error(PARAMETER_PROBLEM, "Port `%s' not valid\n", arg);
54
55	dash = strchr(arg, '-');
56	if (!dash) {
57		mr->range[0].min.tcp.port
58			= mr->range[0].max.tcp.port
59			= htons(port);
60	} else {
61		int maxport;
62
63		maxport = atoi(dash + 1);
64		if (maxport == 0 || maxport > 65535)
65			exit_error(PARAMETER_PROBLEM,
66				   "Port `%s' not valid\n", dash+1);
67		if (maxport < port)
68			/* People are stupid. */
69			exit_error(PARAMETER_PROBLEM,
70				   "Port range `%s' funky\n", arg);
71		mr->range[0].min.tcp.port = htons(port);
72		mr->range[0].max.tcp.port = htons(maxport);
73	}
74}
75
76/* Function which parses command options; returns true if it
77   ate an option */
78static int
79parse(int c, char **argv, int invert, unsigned int *flags,
80      const struct ipt_entry *entry,
81      struct ipt_entry_target **target)
82{
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		return 1;
106
107	default:
108		return 0;
109	}
110}
111
112/* Final check; don't care. */
113static void final_check(unsigned int flags)
114{
115}
116
117/* Prints out the targinfo. */
118static void
119print(const struct ipt_ip *ip,
120      const struct ipt_entry_target *target,
121      int numeric)
122{
123	struct ip_nat_multi_range *mr
124		= (struct ip_nat_multi_range *)target->data;
125	struct ip_nat_range *r = &mr->range[0];
126
127	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
128		printf("redir ports ");
129		printf("%hu", ntohs(r->min.tcp.port));
130		if (r->max.tcp.port != r->min.tcp.port)
131			printf("-%hu", ntohs(r->max.tcp.port));
132		printf(" ");
133	}
134}
135
136/* Saves the union ipt_targinfo in parsable form to stdout. */
137static void
138save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
139{
140	struct ip_nat_multi_range *mr
141		= (struct ip_nat_multi_range *)target->data;
142	struct ip_nat_range *r = &mr->range[0];
143
144	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
145		printf("--to-ports ");
146		printf("%hu", ntohs(r->min.tcp.port));
147		if (r->max.tcp.port != r->min.tcp.port)
148			printf("-%hu", ntohs(r->max.tcp.port));
149		printf(" ");
150	}
151}
152
153static struct iptables_target redir = {
154	.next		= NULL,
155	.name		= "REDIRECT",
156	.version	= IPTABLES_VERSION,
157	.size		= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
158	.userspacesize	= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
159	.help		= &help,
160	.init		= &init,
161 	.parse		= &parse,
162	.final_check	= &final_check,
163	.print		= &print,
164	.save		= &save,
165	.extra_opts	= opts
166};
167
168void ipt_REDIRECT_init(void)
169{
170	register_target(&redir);
171}
172