xt_state.c revision 62fc8051083a334578c3f4b3488808f210b4565f 
1/* Kernel module to match connection tracking information. */
2
3/* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2005 Netfilter Core Team <coreteam@netfilter.org>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11#include <linux/module.h>
12#include <linux/skbuff.h>
13#include <net/netfilter/nf_conntrack.h>
14#include <linux/netfilter/x_tables.h>
15#include <linux/netfilter/xt_state.h>
16
17MODULE_LICENSE("GPL");
18MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
19MODULE_DESCRIPTION("ip[6]_tables connection tracking state match module");
20MODULE_ALIAS("ipt_state");
21MODULE_ALIAS("ip6t_state");
22
23static bool
24state_mt(const struct sk_buff *skb, struct xt_action_param *par)
25{
26	const struct xt_state_info *sinfo = par->matchinfo;
27	enum ip_conntrack_info ctinfo;
28	unsigned int statebit;
29
30	if (nf_ct_is_untracked(skb))
31		statebit = XT_STATE_UNTRACKED;
32	else if (!nf_ct_get(skb, &ctinfo))
33		statebit = XT_STATE_INVALID;
34	else
35		statebit = XT_STATE_BIT(ctinfo);
36
37	return (sinfo->statemask & statebit);
38}
39
40static int state_mt_check(const struct xt_mtchk_param *par)
41{
42	int ret;
43
44	ret = nf_ct_l3proto_try_module_get(par->family);
45	if (ret < 0)
46		pr_info("cannot load conntrack support for proto=%u\n",
47			par->family);
48	return ret;
49}
50
51static void state_mt_destroy(const struct xt_mtdtor_param *par)
52{
53	nf_ct_l3proto_module_put(par->family);
54}
55
56static struct xt_match state_mt_reg __read_mostly = {
57	.name       = "state",
58	.family     = NFPROTO_UNSPEC,
59	.checkentry = state_mt_check,
60	.match      = state_mt,
61	.destroy    = state_mt_destroy,
62	.matchsize  = sizeof(struct xt_state_info),
63	.me         = THIS_MODULE,
64};
65
66static int __init state_mt_init(void)
67{
68	return xt_register_match(&state_mt_reg);
69}
70
71static void __exit state_mt_exit(void)
72{
73	xt_unregister_match(&state_mt_reg);
74}
75
76module_init(state_mt_init);
77module_exit(state_mt_exit);
78