xt_state.c revision 4470bbc749e5551cce914529309456f631e25120 
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_compat.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 int
24match(const struct sk_buff *skb,
25      const struct net_device *in,
26      const struct net_device *out,
27      const struct xt_match *match,
28      const void *matchinfo,
29      int offset,
30      unsigned int protoff,
31      int *hotdrop)
32{
33	const struct xt_state_info *sinfo = matchinfo;
34	enum ip_conntrack_info ctinfo;
35	unsigned int statebit;
36
37	if (nf_ct_is_untracked(skb))
38		statebit = XT_STATE_UNTRACKED;
39	else if (!nf_ct_get_ctinfo(skb, &ctinfo))
40		statebit = XT_STATE_INVALID;
41	else
42		statebit = XT_STATE_BIT(ctinfo);
43
44	return (sinfo->statemask & statebit);
45}
46
47static int check(const char *tablename,
48		 const void *inf,
49		 const struct xt_match *match,
50		 void *matchinfo,
51		 unsigned int matchsize,
52		 unsigned int hook_mask)
53{
54#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
55	if (nf_ct_l3proto_try_module_get(match->family) < 0) {
56		printk(KERN_WARNING "can't load nf_conntrack support for "
57				    "proto=%d\n", match->family);
58		return 0;
59	}
60#endif
61	return 1;
62}
63
64static void
65destroy(const struct xt_match *match, void *matchinfo, unsigned int matchsize)
66{
67#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
68	nf_ct_l3proto_module_put(match->family);
69#endif
70}
71
72static struct xt_match xt_state_match[] = {
73	{
74		.name		= "state",
75		.family		= AF_INET,
76		.checkentry	= check,
77		.match		= match,
78		.destroy	= destroy,
79		.matchsize	= sizeof(struct xt_state_info),
80		.me		= THIS_MODULE,
81	},
82	{
83		.name		= "state",
84		.family		= AF_INET6,
85		.checkentry	= check,
86		.match		= match,
87		.destroy	= destroy,
88		.matchsize	= sizeof(struct xt_state_info),
89		.me		= THIS_MODULE,
90	},
91};
92
93static int __init xt_state_init(void)
94{
95	need_conntrack();
96	return xt_register_matches(xt_state_match, ARRAY_SIZE(xt_state_match));
97}
98
99static void __exit xt_state_fini(void)
100{
101	xt_unregister_matches(xt_state_match, ARRAY_SIZE(xt_state_match));
102}
103
104module_init(xt_state_init);
105module_exit(xt_state_fini);
106