xt_state.c revision d3c5ee6d545b5372fd525ebe16988a5b6efeceb0 
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, const struct net_device *in,
25         const struct net_device *out, const struct xt_match *match,
26         const void *matchinfo, int offset, unsigned int protoff,
27         bool *hotdrop)
28{
29	const struct xt_state_info *sinfo = matchinfo;
30	enum ip_conntrack_info ctinfo;
31	unsigned int statebit;
32
33	if (nf_ct_is_untracked(skb))
34		statebit = XT_STATE_UNTRACKED;
35	else if (!nf_ct_get(skb, &ctinfo))
36		statebit = XT_STATE_INVALID;
37	else
38		statebit = XT_STATE_BIT(ctinfo);
39
40	return (sinfo->statemask & statebit);
41}
42
43static bool
44state_mt_check(const char *tablename, const void *inf,
45               const struct xt_match *match, void *matchinfo,
46               unsigned int hook_mask)
47{
48	if (nf_ct_l3proto_try_module_get(match->family) < 0) {
49		printk(KERN_WARNING "can't load conntrack support for "
50				    "proto=%d\n", match->family);
51		return false;
52	}
53	return true;
54}
55
56static void state_mt_destroy(const struct xt_match *match, void *matchinfo)
57{
58	nf_ct_l3proto_module_put(match->family);
59}
60
61static struct xt_match state_mt_reg[] __read_mostly = {
62	{
63		.name		= "state",
64		.family		= AF_INET,
65		.checkentry	= state_mt_check,
66		.match		= state_mt,
67		.destroy	= state_mt_destroy,
68		.matchsize	= sizeof(struct xt_state_info),
69		.me		= THIS_MODULE,
70	},
71	{
72		.name		= "state",
73		.family		= AF_INET6,
74		.checkentry	= state_mt_check,
75		.match		= state_mt,
76		.destroy	= state_mt_destroy,
77		.matchsize	= sizeof(struct xt_state_info),
78		.me		= THIS_MODULE,
79	},
80};
81
82static int __init state_mt_init(void)
83{
84	return xt_register_matches(state_mt_reg, ARRAY_SIZE(state_mt_reg));
85}
86
87static void __exit state_mt_exit(void)
88{
89	xt_unregister_matches(state_mt_reg, ARRAY_SIZE(state_mt_reg));
90}
91
92module_init(state_mt_init);
93module_exit(state_mt_exit);
94