libipt_SAME.c revision e656e265bc67a55f6e51aa07118f96c058a97798 
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
15help(void)
16{
17	printf(
18"SAME v%s options:\n"
19" --to <ipaddr>-<ipaddr>\n"
20"				Addresses to map source to.\n"
21"				 May be specified more than\n"
22"				  once for multiple ranges.\n"
23" --nodst\n"
24"				Don't use destination-ip in\n"
25"				           source selection\n"
26" --random\n"
27"				Randomize source port\n"
28,
29IPTABLES_VERSION);
30}
31
32static struct option opts[] = {
33	{ "to", 1, 0, '1' },
34	{ "nodst", 0, 0, '2'},
35	{ "random", 0, 0, '3' },
36	{ 0 }
37};
38
39/* Initialize the target. */
40static void
41init(struct ipt_entry_target *t, unsigned int *nfcache)
42{
43	struct ipt_same_info *mr = (struct ipt_same_info *)t->data;
44
45	/* Set default to 0 */
46	mr->rangesize = 0;
47	mr->info = 0;
48	mr->ipnum = 0;
49
50}
51
52/* Parses range of IPs */
53static void
54parse_to(char *arg, struct ip_nat_range *range)
55{
56	char *dash;
57	struct in_addr *ip;
58
59	range->flags |= IP_NAT_RANGE_MAP_IPS;
60	dash = strchr(arg, '-');
61
62	if (dash)
63		*dash = '\0';
64
65	ip = dotted_to_addr(arg);
66	if (!ip)
67		exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
68			   arg);
69	range->min_ip = ip->s_addr;
70
71	if (dash) {
72		ip = dotted_to_addr(dash+1);
73		if (!ip)
74			exit_error(PARAMETER_PROBLEM, "Bad IP address `%s'\n",
75				   dash+1);
76	}
77	range->max_ip = ip->s_addr;
78	if (dash)
79		if (range->min_ip > range->max_ip)
80			exit_error(PARAMETER_PROBLEM, "Bad IP range `%s-%s'\n",
81				   arg, dash+1);
82}
83
84#define IPT_SAME_OPT_TO			0x01
85#define IPT_SAME_OPT_NODST		0x02
86#define IPT_SAME_OPT_RANDOM		0x04
87
88/* Function which parses command options; returns true if it
89   ate an option */
90static int
91parse(int c, char **argv, int invert, unsigned int *flags,
92      const struct ipt_entry *entry,
93      struct ipt_entry_target **target)
94{
95	struct ipt_same_info *mr
96		= (struct ipt_same_info *)(*target)->data;
97	int count;
98
99	switch (c) {
100	case '1':
101		if (mr->rangesize == IPT_SAME_MAX_RANGE)
102			exit_error(PARAMETER_PROBLEM,
103				   "Too many ranges specified, maximum "
104				   "is %i ranges.\n",
105				   IPT_SAME_MAX_RANGE);
106		if (check_inverse(optarg, &invert, NULL, 0))
107			exit_error(PARAMETER_PROBLEM,
108				   "Unexpected `!' after --to");
109
110		parse_to(optarg, &mr->range[mr->rangesize]);
111		/* WTF do we need this for? */
112		if (*flags & IPT_SAME_OPT_RANDOM)
113			mr->range[mr->rangesize].flags
114				|= IP_NAT_RANGE_PROTO_RANDOM;
115		mr->rangesize++;
116		*flags |= IPT_SAME_OPT_TO;
117		break;
118
119	case '2':
120		if (*flags & IPT_SAME_OPT_NODST)
121			exit_error(PARAMETER_PROBLEM,
122				   "Can't specify --nodst twice");
123
124		mr->info |= IPT_SAME_NODST;
125		*flags |= IPT_SAME_OPT_NODST;
126		break;
127
128	case '3':
129		*flags |= IPT_SAME_OPT_RANDOM;
130		for (count=0; count < mr->rangesize; count++)
131			mr->range[count].flags |= IP_NAT_RANGE_PROTO_RANDOM;
132		break;
133
134	default:
135		return 0;
136	}
137
138	return 1;
139}
140
141/* Final check; need --to. */
142static void final_check(unsigned int flags)
143{
144	if (!(flags & IPT_SAME_OPT_TO))
145		exit_error(PARAMETER_PROBLEM,
146			   "SAME needs --to");
147}
148
149/* Prints out the targinfo. */
150static void
151print(const struct ipt_ip *ip,
152      const struct ipt_entry_target *target,
153      int numeric)
154{
155	int count;
156	struct ipt_same_info *mr
157		= (struct ipt_same_info *)target->data;
158	int random = 0;
159
160	printf("same:");
161
162	for (count = 0; count < mr->rangesize; count++) {
163		struct ip_nat_range *r = &mr->range[count];
164		struct in_addr a;
165
166		a.s_addr = r->min_ip;
167
168		printf("%s", addr_to_dotted(&a));
169		a.s_addr = r->max_ip;
170
171		if (r->min_ip == r->max_ip)
172			printf(" ");
173		else
174			printf("-%s ", addr_to_dotted(&a));
175		if (r->flags & IP_NAT_RANGE_PROTO_RANDOM)
176			random = 1;
177	}
178
179	if (mr->info & IPT_SAME_NODST)
180		printf("nodst ");
181
182	if (random)
183		printf("random ");
184}
185
186/* Saves the union ipt_targinfo in parsable form to stdout. */
187static void
188save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
189{
190	int count;
191	struct ipt_same_info *mr
192		= (struct ipt_same_info *)target->data;
193
194	for (count = 0; count < mr->rangesize; count++) {
195		struct ip_nat_range *r = &mr->range[count];
196		struct in_addr a;
197
198		a.s_addr = r->min_ip;
199		printf("--to %s", addr_to_dotted(&a));
200		a.s_addr = r->max_ip;
201
202		if (r->min_ip == r->max_ip)
203			printf(" ");
204		else
205			printf("-%s ", addr_to_dotted(&a));
206	}
207
208	if (mr->info & IPT_SAME_NODST)
209		printf("--nodst ");
210}
211
212static struct iptables_target same = {
213	.next		= NULL,
214	.name		= "SAME",
215	.version	= IPTABLES_VERSION,
216	.size		= IPT_ALIGN(sizeof(struct ipt_same_info)),
217	.userspacesize	= IPT_ALIGN(sizeof(struct ipt_same_info)),
218	.help		= &help,
219	.init		= &init,
220	.parse		= &parse,
221	.final_check	= &final_check,
222	.print		= &print,
223	.save		= &save,
224	.extra_opts	= opts
225};
226
227void _init(void)
228{
229	register_target(&same);
230}
231