libipt_NETMAP.c revision 8caee8b9e34fed4562fcff553197c161fc9d9979 
1/* Shared library add-on to iptables to add static NAT support.
2   Author: Svenning Soerensen <svenning@post5.tele.dk>
3*/
4
5#include <stdio.h>
6#include <netdb.h>
7#include <string.h>
8#include <stdlib.h>
9#include <getopt.h>
10#include <iptables.h>
11#include <linux/netfilter_ipv4/ip_tables.h>
12#include <linux/netfilter_ipv4/ip_nat_rule.h>
13
14#define MODULENAME "NETMAP"
15
16static struct option opts[] = {
17	{ "to", 1, 0, '1' },
18	{ 0 }
19};
20
21/* Function which prints out usage message. */
22static void
23help(void)
24{
25	printf(MODULENAME" v%s options:\n"
26	       "  --%s address[/mask]\n"
27	       "				Network address to map to.\n\n",
28	       IPTABLES_VERSION, opts[0].name);
29}
30
31static u_int32_t
32bits2netmask(int bits)
33{
34	u_int32_t netmask, bm;
35
36	if (bits >= 32 || bits < 0)
37		return(~0);
38	for (netmask = 0, bm = 0x80000000; bits; bits--, bm >>= 1)
39		netmask |= bm;
40	return htonl(netmask);
41}
42
43static int
44netmask2bits(u_int32_t netmask)
45{
46	u_int32_t bm;
47	int bits;
48
49	netmask = ntohl(netmask);
50	for (bits = 0, bm = 0x80000000; netmask & bm; netmask <<= 1)
51		bits++;
52	if (netmask)
53		return -1; /* holes in netmask */
54	return bits;
55}
56
57/* Initialize the target. */
58static void
59init(struct ipt_entry_target *t, unsigned int *nfcache)
60{
61	struct ip_nat_multi_range *mr = (struct ip_nat_multi_range *)t->data;
62
63	/* Actually, it's 0, but it's ignored at the moment. */
64	mr->rangesize = 1;
65
66	/* Can't cache this */
67	*nfcache |= NFC_UNKNOWN;
68}
69
70/* Parses network address */
71static void
72parse_to(char *arg, struct ip_nat_range *range)
73{
74	char *slash;
75	struct in_addr *ip;
76	u_int32_t netmask;
77	unsigned int bits;
78
79	range->flags |= IP_NAT_RANGE_MAP_IPS;
80	slash = strchr(arg, '/');
81	if (slash)
82		*slash = '\0';
83
84	ip = dotted_to_addr(arg);
85	if (!ip)
86		exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
87			   arg);
88	range->min_ip = ip->s_addr;
89	if (slash) {
90		if (strchr(slash+1, '.')) {
91			ip = dotted_to_addr(slash+1);
92			if (!ip)
93				exit_error(PARAMETER_PROBLEM, "Bad netmask `%s'\n",
94					   slash+1);
95			netmask = ip->s_addr;
96		}
97		else {
98			if (string_to_number(slash+1, 0, 32, &bits) == -1)
99				exit_error(PARAMETER_PROBLEM, "Bad netmask `%s'\n",
100					   slash+1);
101			netmask = bits2netmask(bits);
102		}
103		/* Don't allow /0 (/1 is probably insane, too) */
104		if (netmask == 0)
105			exit_error(PARAMETER_PROBLEM, "Netmask needed\n");
106	}
107	else
108		netmask = ~0;
109
110	if (range->min_ip & ~netmask) {
111		if (slash)
112			*slash = '/';
113		exit_error(PARAMETER_PROBLEM, "Bad network address `%s'\n",
114			   arg);
115	}
116	range->max_ip = range->min_ip | ~netmask;
117}
118
119/* Function which parses command options; returns true if it
120   ate an option */
121static int
122parse(int c, char **argv, int invert, unsigned int *flags,
123      const struct ipt_entry *entry,
124      struct ipt_entry_target **target)
125{
126	struct ip_nat_multi_range *mr
127		= (struct ip_nat_multi_range *)(*target)->data;
128
129	switch (c) {
130	case '1':
131		if (check_inverse(optarg, &invert, NULL, 0))
132			exit_error(PARAMETER_PROBLEM,
133				   "Unexpected `!' after --%s", opts[0].name);
134
135		parse_to(optarg, &mr->range[0]);
136		*flags = 1;
137		return 1;
138
139	default:
140		return 0;
141	}
142}
143
144/* Final check; need --to */
145static void final_check(unsigned int flags)
146{
147	if (!flags)
148		exit_error(PARAMETER_PROBLEM,
149			   MODULENAME" needs --%s", opts[0].name);
150}
151
152/* Prints out the targinfo. */
153static void
154print(const struct ipt_ip *ip,
155      const struct ipt_entry_target *target,
156      int numeric)
157{
158	struct ip_nat_multi_range *mr
159		= (struct ip_nat_multi_range *)target->data;
160	struct ip_nat_range *r = &mr->range[0];
161	struct in_addr a;
162	int bits;
163
164	a.s_addr = r->min_ip;
165	printf("%s", addr_to_dotted(&a));
166	a.s_addr = ~(r->min_ip ^ r->max_ip);
167	bits = netmask2bits(a.s_addr);
168	if (bits < 0)
169		printf("/%s", addr_to_dotted(&a));
170	else
171		printf("/%d", bits);
172}
173
174/* Saves the targinfo in parsable form to stdout. */
175static void
176save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
177{
178	printf("--%s ", opts[0].name);
179	print(ip, target, 0);
180}
181
182static struct iptables_target target_module = {
183	.next		= NULL,
184	.name		= MODULENAME,
185	.version	= IPTABLES_VERSION,
186	.size		= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
187	.userspacesize	= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
188	.help		= &help,
189	.init		= &init,
190	.parse		= &parse,
191	.final_check	= &final_check,
192	.print		= &print,
193	.save		= &save,
194	.extra_opts	= opts
195};
196
197void _init(void)
198{
199	register_target(&target_module);
200}
201
202