libipt_SAME.c revision 7a236f4cc685a420c1a782a5db614a93baf37ccf 
1/* Shared library add-on to iptables to add simple non load-balancing SNAT 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/nf_nat.h>
10/* For 64bit kernel / 32bit userspace */
11#include "../include/linux/netfilter_ipv4/ipt_SAME.h"
12
13/* Function which prints out usage message. */
14static void SAME_help(void)
15{
16	printf(
17"SAME v%s options:\n"
18" --to <ipaddr>-<ipaddr>\n"
19"				Addresses to map source to.\n"
20"				 May be specified more than\n"
21"				  once for multiple ranges.\n"
22" --nodst\n"
23"				Don't use destination-ip in\n"
24"				           source selection\n"
25" --random\n"
26"				Randomize source port\n"
27,
28IPTABLES_VERSION);
29}
30
31static const struct option SAME_opts[] = {
32	{ "to", 1, NULL, '1' },
33	{ "nodst", 0, NULL, '2'},
34	{ "random", 0, NULL, '3' },
35	{ .name = NULL }
36};
37
38/* Initialize the target. */
39static void SAME_init(struct xt_entry_target *t)
40{
41	struct ipt_same_info *mr = (struct ipt_same_info *)t->data;
42
43	/* Set default to 0 */
44	mr->rangesize = 0;
45	mr->info = 0;
46	mr->ipnum = 0;
47
48}
49
50/* Parses range of IPs */
51static void
52parse_to(char *arg, struct ip_nat_range *range)
53{
54	char *dash;
55	const struct in_addr *ip;
56
57	range->flags |= IP_NAT_RANGE_MAP_IPS;
58	dash = strchr(arg, '-');
59
60	if (dash)
61		*dash = '\0';
62
63	ip = numeric_to_ipaddr(arg);
64	if (!ip)
65		exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
66			   arg);
67	range->min_ip = ip->s_addr;
68
69	if (dash) {
70		ip = numeric_to_ipaddr(dash+1);
71		if (!ip)
72			exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
73				   dash+1);
74	}
75	range->max_ip = ip->s_addr;
76	if (dash)
77		if (range->min_ip > range->max_ip)
78			exit_error(PARAMETER_PROBLEM, "Bad IP range `%s-%s'\n",
79				   arg, dash+1);
80}
81
82#define IPT_SAME_OPT_TO			0x01
83#define IPT_SAME_OPT_NODST		0x02
84#define IPT_SAME_OPT_RANDOM		0x04
85
86/* Function which parses command options; returns true if it
87   ate an option */
88static int SAME_parse(int c, char **argv, int invert, unsigned int *flags,
89                      const void *entry, struct xt_entry_target **target)
90{
91	struct ipt_same_info *mr
92		= (struct ipt_same_info *)(*target)->data;
93	unsigned int count;
94
95	switch (c) {
96	case '1':
97		if (mr->rangesize == IPT_SAME_MAX_RANGE)
98			exit_error(PARAMETER_PROBLEM,
99				   "Too many ranges specified, maximum "
100				   "is %i ranges.\n",
101				   IPT_SAME_MAX_RANGE);
102		if (check_inverse(optarg, &invert, NULL, 0))
103			exit_error(PARAMETER_PROBLEM,
104				   "Unexpected `!' after --to");
105
106		parse_to(optarg, &mr->range[mr->rangesize]);
107		/* WTF do we need this for? */
108		if (*flags & IPT_SAME_OPT_RANDOM)
109			mr->range[mr->rangesize].flags
110				|= IP_NAT_RANGE_PROTO_RANDOM;
111		mr->rangesize++;
112		*flags |= IPT_SAME_OPT_TO;
113		break;
114
115	case '2':
116		if (*flags & IPT_SAME_OPT_NODST)
117			exit_error(PARAMETER_PROBLEM,
118				   "Can't specify --nodst twice");
119
120		mr->info |= IPT_SAME_NODST;
121		*flags |= IPT_SAME_OPT_NODST;
122		break;
123
124	case '3':
125		*flags |= IPT_SAME_OPT_RANDOM;
126		for (count=0; count < mr->rangesize; count++)
127			mr->range[count].flags |= IP_NAT_RANGE_PROTO_RANDOM;
128		break;
129
130	default:
131		return 0;
132	}
133
134	return 1;
135}
136
137/* Final check; need --to. */
138static void SAME_check(unsigned int flags)
139{
140	if (!(flags & IPT_SAME_OPT_TO))
141		exit_error(PARAMETER_PROBLEM,
142			   "SAME needs --to");
143}
144
145/* Prints out the targinfo. */
146static void SAME_print(const void *ip, const struct xt_entry_target *target,
147                       int numeric)
148{
149	unsigned int count;
150	struct ipt_same_info *mr
151		= (struct ipt_same_info *)target->data;
152	int random = 0;
153
154	printf("same:");
155
156	for (count = 0; count < mr->rangesize; count++) {
157		struct ip_nat_range *r = &mr->range[count];
158		struct in_addr a;
159
160		a.s_addr = r->min_ip;
161
162		printf("%s", ipaddr_to_numeric(&a));
163		a.s_addr = r->max_ip;
164
165		if (r->min_ip == r->max_ip)
166			printf(" ");
167		else
168			printf("-%s ", ipaddr_to_numeric(&a));
169		if (r->flags & IP_NAT_RANGE_PROTO_RANDOM)
170			random = 1;
171	}
172
173	if (mr->info & IPT_SAME_NODST)
174		printf("nodst ");
175
176	if (random)
177		printf("random ");
178}
179
180/* Saves the union ipt_targinfo in parsable form to stdout. */
181static void SAME_save(const void *ip, const struct xt_entry_target *target)
182{
183	unsigned int count;
184	struct ipt_same_info *mr
185		= (struct ipt_same_info *)target->data;
186	int random = 0;
187
188	for (count = 0; count < mr->rangesize; count++) {
189		struct ip_nat_range *r = &mr->range[count];
190		struct in_addr a;
191
192		a.s_addr = r->min_ip;
193		printf("--to %s", ipaddr_to_numeric(&a));
194		a.s_addr = r->max_ip;
195
196		if (r->min_ip == r->max_ip)
197			printf(" ");
198		else
199			printf("-%s ", ipaddr_to_numeric(&a));
200		if (r->flags & IP_NAT_RANGE_PROTO_RANDOM)
201			random = 1;
202	}
203
204	if (mr->info & IPT_SAME_NODST)
205		printf("--nodst ");
206
207	if (random)
208		printf("--random ");
209}
210
211static struct iptables_target same_target = {
212	.name		= "SAME",
213	.version	= IPTABLES_VERSION,
214	.size		= IPT_ALIGN(sizeof(struct ipt_same_info)),
215	.userspacesize	= IPT_ALIGN(sizeof(struct ipt_same_info)),
216	.help		= SAME_help,
217	.init		= SAME_init,
218	.parse		= SAME_parse,
219	.final_check	= SAME_check,
220	.print		= SAME_print,
221	.save		= SAME_save,
222	.extra_opts	= SAME_opts,
223};
224
225void _init(void)
226{
227	register_target(&same_target);
228}
229