libipt_MASQUERADE.c revision 36d870c76621b94d51816d09eb8fd05e0fb0a0ab 
1/* Shared library add-on to iptables to add masquerade 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
11/* Function which prints out usage message. */
12static void
13help(void)
14{
15	printf(
16"MASQUERADE v%s options:\n"
17" --to-ports <port>[-<port>]\n"
18"				Port (range) to map to.\n\n",
19IPTABLES_VERSION);
20}
21
22static struct option opts[] = {
23	{ "to-ports", 1, 0, '1' },
24	{ 0 }
25};
26
27/* Initialize the target. */
28static void
29init(struct ipt_entry_target *t, unsigned int *nfcache)
30{
31	struct ip_nat_multi_range *mr = (struct ip_nat_multi_range *)t->data;
32
33	/* Actually, it's 0, but it's ignored at the moment. */
34	mr->rangesize = 1;
35
36}
37
38/* Parses ports */
39static void
40parse_ports(const char *arg, struct ip_nat_multi_range *mr)
41{
42	const char *dash;
43	int port;
44
45	mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
46
47	port = atoi(arg);
48	if (port <= 0 || port > 65535)
49		exit_error(PARAMETER_PROBLEM, "Port `%s' not valid\n", arg);
50
51	dash = strchr(arg, '-');
52	if (!dash) {
53		mr->range[0].min.tcp.port
54			= mr->range[0].max.tcp.port
55			= htons(port);
56	} else {
57		int maxport;
58
59		maxport = atoi(dash + 1);
60		if (maxport == 0 || maxport > 65535)
61			exit_error(PARAMETER_PROBLEM,
62				   "Port `%s' not valid\n", dash+1);
63		if (maxport < port)
64			/* People are stupid.  Present reader excepted. */
65			exit_error(PARAMETER_PROBLEM,
66				   "Port range `%s' funky\n", arg);
67		mr->range[0].min.tcp.port = htons(port);
68		mr->range[0].max.tcp.port = htons(maxport);
69	}
70}
71
72/* Function which parses command options; returns true if it
73   ate an option */
74static int
75parse(int c, char **argv, int invert, unsigned int *flags,
76      const struct ipt_entry *entry,
77      struct ipt_entry_target **target)
78{
79	int portok;
80	struct ip_nat_multi_range *mr
81		= (struct ip_nat_multi_range *)(*target)->data;
82
83	if (entry->ip.proto == IPPROTO_TCP
84	    || entry->ip.proto == IPPROTO_UDP
85	    || entry->ip.proto == IPPROTO_ICMP)
86		portok = 1;
87	else
88		portok = 0;
89
90	switch (c) {
91	case '1':
92		if (!portok)
93			exit_error(PARAMETER_PROBLEM,
94				   "Need TCP or UDP with port specification");
95
96		if (check_inverse(optarg, &invert, NULL, 0))
97			exit_error(PARAMETER_PROBLEM,
98				   "Unexpected `!' after --to-ports");
99
100		parse_ports(optarg, mr);
101		return 1;
102
103	default:
104		return 0;
105	}
106}
107
108/* Final check; don't care. */
109static void final_check(unsigned int flags)
110{
111}
112
113/* Prints out the targinfo. */
114static void
115print(const struct ipt_ip *ip,
116      const struct ipt_entry_target *target,
117      int numeric)
118{
119	struct ip_nat_multi_range *mr
120		= (struct ip_nat_multi_range *)target->data;
121	struct ip_nat_range *r = &mr->range[0];
122
123	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
124		printf("masq ports: ");
125		printf("%hu", ntohs(r->min.tcp.port));
126		if (r->max.tcp.port != r->min.tcp.port)
127			printf("-%hu", ntohs(r->max.tcp.port));
128		printf(" ");
129	}
130}
131
132/* Saves the union ipt_targinfo in parsable form to stdout. */
133static void
134save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
135{
136	struct ip_nat_multi_range *mr
137		= (struct ip_nat_multi_range *)target->data;
138	struct ip_nat_range *r = &mr->range[0];
139
140	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
141		printf("--to-ports %hu", ntohs(r->min.tcp.port));
142		if (r->max.tcp.port != r->min.tcp.port)
143			printf("-%hu", ntohs(r->max.tcp.port));
144		printf(" ");
145	}
146}
147
148static struct iptables_target masq = { NULL,
149	.name		= "MASQUERADE",
150	.version	= IPTABLES_VERSION,
151	.size		= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
152	.userspacesize	= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
153	.help		= &help,
154	.init		= &init,
155	.parse		= &parse,
156	.final_check	= &final_check,
157	.print		= &print,
158	.save		= &save,
159	.extra_opts	= opts
160};
161
162void _init(void)
163{
164	register_target(&masq);
165}
166