libipt_DNAT.c revision 4008138e2b5248940265b160fae001d8954fae21 
1/* Shared library add-on to iptables to add destination-NAT 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/* Dest NAT data consists of a multi-range, indicating where to map
13   to. */
14struct ipt_natinfo
15{
16	struct ipt_entry_target t;
17	struct ip_nat_multi_range mr;
18};
19
20/* Function which prints out usage message. */
21static void
22help(void)
23{
24	printf(
25"DNAT v%s options:\n"
26" --to-destination <ipaddr>[-<ipaddr>][:port-port]\n"
27"				Address to map destination to.\n"
28"				(You can use this more than once)\n\n",
29IPTABLES_VERSION);
30}
31
32static struct option opts[] = {
33	{ "to-destination", 1, 0, '1' },
34	{ 0 }
35};
36
37static struct ipt_natinfo *
38append_range(struct ipt_natinfo *info, const struct ip_nat_range *range)
39{
40	unsigned int size;
41
42	/* One rangesize already in struct ipt_natinfo */
43	size = IPT_ALIGN(sizeof(*info) + info->mr.rangesize * sizeof(*range));
44
45	info = realloc(info, size);
46	if (!info)
47		exit_error(OTHER_PROBLEM, "Out of memory\n");
48
49	info->t.u.target_size = size;
50	info->mr.range[info->mr.rangesize] = *range;
51	info->mr.rangesize++;
52
53	return info;
54}
55
56/* Ranges expected in network order. */
57static struct ipt_entry_target *
58parse_to(char *arg, int portok, struct ipt_natinfo *info)
59{
60	struct ip_nat_range range;
61	char *colon, *dash, *error;
62	struct in_addr *ip;
63
64	memset(&range, 0, sizeof(range));
65	colon = strchr(arg, ':');
66
67	if (colon) {
68		int port;
69
70		if (!portok)
71			exit_error(PARAMETER_PROBLEM,
72				   "Need TCP or UDP with port specification");
73
74		range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
75
76		port = atoi(colon+1);
77		if (port <= 0 || port > 65535)
78			exit_error(PARAMETER_PROBLEM,
79				   "Port `%s' not valid\n", colon+1);
80
81		error = strchr(colon+1, ':');
82		if (error)
83			exit_error(PARAMETER_PROBLEM,
84				   "Invalid port:port syntax - use dash\n");
85
86		dash = strchr(colon, '-');
87		if (!dash) {
88			range.min.tcp.port
89				= range.max.tcp.port
90				= htons(port);
91		} else {
92			int maxport;
93
94			maxport = atoi(dash + 1);
95			if (maxport <= 0 || maxport > 65535)
96				exit_error(PARAMETER_PROBLEM,
97					   "Port `%s' not valid\n", dash+1);
98			if (maxport < port)
99				/* People are stupid. */
100				exit_error(PARAMETER_PROBLEM,
101					   "Port range `%s' funky\n", colon+1);
102			range.min.tcp.port = htons(port);
103			range.max.tcp.port = htons(maxport);
104		}
105		/* Starts with a colon? No IP info...*/
106		if (colon == arg)
107			return &(append_range(info, &range)->t);
108		*colon = '\0';
109	}
110
111	range.flags |= IP_NAT_RANGE_MAP_IPS;
112	dash = strchr(arg, '-');
113	if (colon && dash && dash > colon)
114		dash = NULL;
115
116	if (dash)
117		*dash = '\0';
118
119	ip = dotted_to_addr(arg);
120	if (!ip)
121		exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
122			   arg);
123	range.min_ip = ip->s_addr;
124	if (dash) {
125		ip = dotted_to_addr(dash+1);
126		if (!ip)
127			exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
128				   dash+1);
129		range.max_ip = ip->s_addr;
130	} else
131		range.max_ip = range.min_ip;
132
133	return &(append_range(info, &range)->t);
134}
135
136/* Function which parses command options; returns true if it
137   ate an option */
138static int
139parse(int c, char **argv, int invert, unsigned int *flags,
140      const struct ipt_entry *entry,
141      struct ipt_entry_target **target)
142{
143	struct ipt_natinfo *info = (void *)*target;
144	int portok;
145
146	if (entry->ip.proto == IPPROTO_TCP
147	    || entry->ip.proto == IPPROTO_UDP
148	    || entry->ip.proto == IPPROTO_ICMP)
149		portok = 1;
150	else
151		portok = 0;
152
153	switch (c) {
154	case '1':
155		if (check_inverse(optarg, &invert, NULL, 0))
156			exit_error(PARAMETER_PROBLEM,
157				   "Unexpected `!' after --to-destination");
158
159		if (*flags) {
160			if (!kernel_version)
161				get_kernel_version();
162			if (kernel_version > LINUX_VERSION(2, 6, 10))
163				exit_error(PARAMETER_PROBLEM,
164					   "Multiple --to-destination not supported");
165		}
166		*target = parse_to(optarg, portok, info);
167		*flags = 1;
168		return 1;
169
170	default:
171		return 0;
172	}
173}
174
175/* Final check; must have specfied --to-source. */
176static void final_check(unsigned int flags)
177{
178	if (!flags)
179		exit_error(PARAMETER_PROBLEM,
180			   "You must specify --to-destination");
181}
182
183static void print_range(const struct ip_nat_range *r)
184{
185	if (r->flags & IP_NAT_RANGE_MAP_IPS) {
186		struct in_addr a;
187
188		a.s_addr = r->min_ip;
189		printf("%s", addr_to_dotted(&a));
190		if (r->max_ip != r->min_ip) {
191			a.s_addr = r->max_ip;
192			printf("-%s", addr_to_dotted(&a));
193		}
194	}
195	if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) {
196		printf(":");
197		printf("%hu", ntohs(r->min.tcp.port));
198		if (r->max.tcp.port != r->min.tcp.port)
199			printf("-%hu", ntohs(r->max.tcp.port));
200	}
201}
202
203/* Prints out the targinfo. */
204static void
205print(const struct ipt_ip *ip,
206      const struct ipt_entry_target *target,
207      int numeric)
208{
209	struct ipt_natinfo *info = (void *)target;
210	unsigned int i = 0;
211
212	printf("to:");
213	for (i = 0; i < info->mr.rangesize; i++) {
214		print_range(&info->mr.range[i]);
215		printf(" ");
216	}
217}
218
219/* Saves the union ipt_targinfo in parsable form to stdout. */
220static void
221save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
222{
223	struct ipt_natinfo *info = (void *)target;
224	unsigned int i = 0;
225
226	for (i = 0; i < info->mr.rangesize; i++) {
227		printf("--to-destination ");
228		print_range(&info->mr.range[i]);
229		printf(" ");
230	}
231}
232
233static struct iptables_target dnat = {
234	.next		= NULL,
235	.name		= "DNAT",
236	.version	= IPTABLES_VERSION,
237	.size		= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
238	.userspacesize	= IPT_ALIGN(sizeof(struct ip_nat_multi_range)),
239	.help		= &help,
240	.parse		= &parse,
241	.final_check	= &final_check,
242	.print		= &print,
243	.save		= &save,
244	.extra_opts	= opts
245};
246
247void ipt_DNAT_init(void)
248{
249	register_target(&dnat);
250}
251