libipt_REDIRECT.c revision 0f16c725aadaac7e670d632ecbaea3661ff00827 
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 <xtables.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
14static void REDIRECT_help(void)
15{
16	printf(
17"REDIRECT target options:\n"
18" --to-ports <port>[-<port>]\n"
19"				Port (range) to map to.\n");
20}
21
22static const struct option REDIRECT_opts[] = {
23	{ "to-ports", 1, NULL, '1' },
24	{ "random", 0, NULL, '2' },
25	{ .name = NULL }
26};
27
28static void REDIRECT_init(struct xt_entry_target *t)
29{
30	struct ip_nat_multi_range *mr = (struct ip_nat_multi_range *)t->data;
31
32	/* Actually, it's 0, but it's ignored at the moment. */
33	mr->rangesize = 1;
34
35}
36
37/* Parses ports */
38static void
39parse_ports(const char *arg, struct ip_nat_multi_range *mr)
40{
41	const char *dash;
42	int port;
43
44	mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
45
46	if (strchr(arg, '.'))
47		exit_error(PARAMETER_PROBLEM, "IP address not permitted\n");
48
49	port = atoi(arg);
50	if (port == 0)
51		port = xtables_service_to_port(arg, NULL);
52
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
77static int REDIRECT_parse(int c, char **argv, int invert, unsigned int *flags,
78                          const void *e, struct xt_entry_target **target)
79{
80	const struct ipt_entry *entry = e;
81	struct ip_nat_multi_range *mr
82		= (struct ip_nat_multi_range *)(*target)->data;
83	int portok;
84
85	if (entry->ip.proto == IPPROTO_TCP
86	    || entry->ip.proto == IPPROTO_UDP
87	    || entry->ip.proto == IPPROTO_SCTP
88	    || entry->ip.proto == IPPROTO_DCCP
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, UDP, SCTP or DCCP with port specification");
99
100		if (xtables_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
123static void REDIRECT_print(const void *ip, const struct xt_entry_target *target,
124                           int numeric)
125{
126	struct ip_nat_multi_range *mr
127		= (struct ip_nat_multi_range *)target->data;
128	struct ip_nat_range *r = &mr->range[0];
129
130	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
131		printf("redir ports ");
132		printf("%hu", ntohs(r->min.tcp.port));
133		if (r->max.tcp.port != r->min.tcp.port)
134			printf("-%hu", ntohs(r->max.tcp.port));
135		printf(" ");
136		if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM)
137			printf("random ");
138	}
139}
140
141static void REDIRECT_save(const void *ip, const struct xt_entry_target *target)
142{
143	struct ip_nat_multi_range *mr
144		= (struct ip_nat_multi_range *)target->data;
145	struct ip_nat_range *r = &mr->range[0];
146
147	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
148		printf("--to-ports ");
149		printf("%hu", ntohs(r->min.tcp.port));
150		if (r->max.tcp.port != r->min.tcp.port)
151			printf("-%hu", ntohs(r->max.tcp.port));
152		printf(" ");
153		if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM)
154			printf("--random ");
155	}
156}
157
158static struct xtables_target redirect_tg_reg = {
159	.name		= "REDIRECT",
160	.version	= XTABLES_VERSION,
161	.family		= NFPROTO_IPV4,
162	.size		= XT_ALIGN(sizeof(struct ip_nat_multi_range)),
163	.userspacesize	= XT_ALIGN(sizeof(struct ip_nat_multi_range)),
164	.help		= REDIRECT_help,
165	.init		= REDIRECT_init,
166 	.parse		= REDIRECT_parse,
167	.print		= REDIRECT_print,
168	.save		= REDIRECT_save,
169	.extra_opts	= REDIRECT_opts,
170};
171
172void _init(void)
173{
174	xtables_register_target(&redirect_tg_reg);
175}
176