libipt_MASQUERADE.c revision 4008138e2b5248940265b160fae001d8954fae21 
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#include <netinet/in.h>
11
12/* Function which prints out usage message. */
13static void
14help(void)
15{
16	printf(
17"MASQUERADE 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	port = atoi(arg);
49	if (port <= 0 || port > 65535)
50		exit_error(PARAMETER_PROBLEM, "Port `%s' not valid\n", arg);
51
52	dash = strchr(arg, '-');
53	if (!dash) {
54		mr->range[0].min.tcp.port
55			= mr->range[0].max.tcp.port
56			= htons(port);
57	} else {
58		int maxport;
59
60		maxport = atoi(dash + 1);
61		if (maxport == 0 || maxport > 65535)
62			exit_error(PARAMETER_PROBLEM,
63				   "Port `%s' not valid\n", dash+1);
64		if (maxport < port)
65			/* People are stupid.  Present reader excepted. */
66			exit_error(PARAMETER_PROBLEM,
67				   "Port range `%s' funky\n", arg);
68		mr->range[0].min.tcp.port = htons(port);
69		mr->range[0].max.tcp.port = htons(maxport);
70	}
71}
72
73/* Function which parses command options; returns true if it
74   ate an option */
75static int
76parse(int c, char **argv, int invert, unsigned int *flags,
77      const struct ipt_entry *entry,
78      struct ipt_entry_target **target)
79{
80	int portok;
81	struct ip_nat_multi_range *mr
82		= (struct ip_nat_multi_range *)(*target)->data;
83
84	if (entry->ip.proto == IPPROTO_TCP
85	    || entry->ip.proto == IPPROTO_UDP
86	    || entry->ip.proto == IPPROTO_ICMP)
87		portok = 1;
88	else
89		portok = 0;
90
91	switch (c) {
92	case '1':
93		if (!portok)
94			exit_error(PARAMETER_PROBLEM,
95				   "Need TCP or UDP with port specification");
96
97		if (check_inverse(optarg, &invert, NULL, 0))
98			exit_error(PARAMETER_PROBLEM,
99				   "Unexpected `!' after --to-ports");
100
101		parse_ports(optarg, mr);
102		return 1;
103
104	default:
105		return 0;
106	}
107}
108
109/* Final check; don't care. */
110static void final_check(unsigned int flags)
111{
112}
113
114/* Prints out the targinfo. */
115static void
116print(const struct ipt_ip *ip,
117      const struct ipt_entry_target *target,
118      int numeric)
119{
120	struct ip_nat_multi_range *mr
121		= (struct ip_nat_multi_range *)target->data;
122	struct ip_nat_range *r = &mr->range[0];
123
124	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
125		printf("masq ports: ");
126		printf("%hu", ntohs(r->min.tcp.port));
127		if (r->max.tcp.port != r->min.tcp.port)
128			printf("-%hu", ntohs(r->max.tcp.port));
129		printf(" ");
130	}
131}
132
133/* Saves the union ipt_targinfo in parsable form to stdout. */
134static void
135save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
136{
137	struct ip_nat_multi_range *mr
138		= (struct ip_nat_multi_range *)target->data;
139	struct ip_nat_range *r = &mr->range[0];
140
141	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
142		printf("--to-ports %hu", ntohs(r->min.tcp.port));
143		if (r->max.tcp.port != r->min.tcp.port)
144			printf("-%hu", ntohs(r->max.tcp.port));
145		printf(" ");
146	}
147}
148
149static struct iptables_target masq = { NULL,
150	.name		= "MASQUERADE",
151	.version	= IPTABLES_VERSION,
152	.size		= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
153	.userspacesize	= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
154	.help		= &help,
155	.init		= &init,
156	.parse		= &parse,
157	.final_check	= &final_check,
158	.print		= &print,
159	.save		= &save,
160	.extra_opts	= opts
161};
162
163void ipt_MASQUERADE_init(void)
164{
165	register_target(&masq);
166}
167