libipt_SAME.c revision 8b7c64d6ba156a99008fcd810cba874c73294333 
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 target 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}
28
29static const struct option SAME_opts[] = {
30	{ "to", 1, NULL, '1' },
31	{ "nodst", 0, NULL, '2'},
32	{ "random", 0, NULL, '3' },
33	{ .name = NULL }
34};
35
36/* Initialize the target. */
37static void SAME_init(struct xt_entry_target *t)
38{
39	struct ipt_same_info *mr = (struct ipt_same_info *)t->data;
40
41	/* Set default to 0 */
42	mr->rangesize = 0;
43	mr->info = 0;
44	mr->ipnum = 0;
45
46}
47
48/* Parses range of IPs */
49static void
50parse_to(char *arg, struct ip_nat_range *range)
51{
52	char *dash;
53	const struct in_addr *ip;
54
55	range->flags |= IP_NAT_RANGE_MAP_IPS;
56	dash = strchr(arg, '-');
57
58	if (dash)
59		*dash = '\0';
60
61	ip = numeric_to_ipaddr(arg);
62	if (!ip)
63		exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
64			   arg);
65	range->min_ip = ip->s_addr;
66
67	if (dash) {
68		ip = numeric_to_ipaddr(dash+1);
69		if (!ip)
70			exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
71				   dash+1);
72	}
73	range->max_ip = ip->s_addr;
74	if (dash)
75		if (range->min_ip > range->max_ip)
76			exit_error(PARAMETER_PROBLEM, "Bad IP range `%s-%s'\n",
77				   arg, dash+1);
78}
79
80#define IPT_SAME_OPT_TO			0x01
81#define IPT_SAME_OPT_NODST		0x02
82#define IPT_SAME_OPT_RANDOM		0x04
83
84/* Function which parses command options; returns true if it
85   ate an option */
86static int SAME_parse(int c, char **argv, int invert, unsigned int *flags,
87                      const void *entry, struct xt_entry_target **target)
88{
89	struct ipt_same_info *mr
90		= (struct ipt_same_info *)(*target)->data;
91	unsigned int count;
92
93	switch (c) {
94	case '1':
95		if (mr->rangesize == IPT_SAME_MAX_RANGE)
96			exit_error(PARAMETER_PROBLEM,
97				   "Too many ranges specified, maximum "
98				   "is %i ranges.\n",
99				   IPT_SAME_MAX_RANGE);
100		if (check_inverse(optarg, &invert, NULL, 0))
101			exit_error(PARAMETER_PROBLEM,
102				   "Unexpected `!' after --to");
103
104		parse_to(optarg, &mr->range[mr->rangesize]);
105		/* WTF do we need this for? */
106		if (*flags & IPT_SAME_OPT_RANDOM)
107			mr->range[mr->rangesize].flags
108				|= IP_NAT_RANGE_PROTO_RANDOM;
109		mr->rangesize++;
110		*flags |= IPT_SAME_OPT_TO;
111		break;
112
113	case '2':
114		if (*flags & IPT_SAME_OPT_NODST)
115			exit_error(PARAMETER_PROBLEM,
116				   "Can't specify --nodst twice");
117
118		mr->info |= IPT_SAME_NODST;
119		*flags |= IPT_SAME_OPT_NODST;
120		break;
121
122	case '3':
123		*flags |= IPT_SAME_OPT_RANDOM;
124		for (count=0; count < mr->rangesize; count++)
125			mr->range[count].flags |= IP_NAT_RANGE_PROTO_RANDOM;
126		break;
127
128	default:
129		return 0;
130	}
131
132	return 1;
133}
134
135/* Final check; need --to. */
136static void SAME_check(unsigned int flags)
137{
138	if (!(flags & IPT_SAME_OPT_TO))
139		exit_error(PARAMETER_PROBLEM,
140			   "SAME needs --to");
141}
142
143/* Prints out the targinfo. */
144static void SAME_print(const void *ip, const struct xt_entry_target *target,
145                       int numeric)
146{
147	unsigned int count;
148	struct ipt_same_info *mr
149		= (struct ipt_same_info *)target->data;
150	int random_selection = 0;
151
152	printf("same:");
153
154	for (count = 0; count < mr->rangesize; count++) {
155		struct ip_nat_range *r = &mr->range[count];
156		struct in_addr a;
157
158		a.s_addr = r->min_ip;
159
160		printf("%s", ipaddr_to_numeric(&a));
161		a.s_addr = r->max_ip;
162
163		if (r->min_ip == r->max_ip)
164			printf(" ");
165		else
166			printf("-%s ", ipaddr_to_numeric(&a));
167		if (r->flags & IP_NAT_RANGE_PROTO_RANDOM)
168			random_selection = 1;
169	}
170
171	if (mr->info & IPT_SAME_NODST)
172		printf("nodst ");
173
174	if (random_selection)
175		printf("random ");
176}
177
178/* Saves the union ipt_targinfo in parsable form to stdout. */
179static void SAME_save(const void *ip, const struct xt_entry_target *target)
180{
181	unsigned int count;
182	struct ipt_same_info *mr
183		= (struct ipt_same_info *)target->data;
184	int random_selection = 0;
185
186	for (count = 0; count < mr->rangesize; count++) {
187		struct ip_nat_range *r = &mr->range[count];
188		struct in_addr a;
189
190		a.s_addr = r->min_ip;
191		printf("--to %s", ipaddr_to_numeric(&a));
192		a.s_addr = r->max_ip;
193
194		if (r->min_ip == r->max_ip)
195			printf(" ");
196		else
197			printf("-%s ", ipaddr_to_numeric(&a));
198		if (r->flags & IP_NAT_RANGE_PROTO_RANDOM)
199			random_selection = 1;
200	}
201
202	if (mr->info & IPT_SAME_NODST)
203		printf("--nodst ");
204
205	if (random_selection)
206		printf("--random ");
207}
208
209static struct xtables_target same_tg_reg = {
210	.name		= "SAME",
211	.version	= XTABLES_VERSION,
212	.family		= PF_INET,
213	.size		= XT_ALIGN(sizeof(struct ipt_same_info)),
214	.userspacesize	= XT_ALIGN(sizeof(struct ipt_same_info)),
215	.help		= SAME_help,
216	.init		= SAME_init,
217	.parse		= SAME_parse,
218	.final_check	= SAME_check,
219	.print		= SAME_print,
220	.save		= SAME_save,
221	.extra_opts	= SAME_opts,
222};
223
224void _init(void)
225{
226	xtables_register_target(&same_tg_reg);
227}
228