net/netfilter/xt_state.c

/* Kernel module to match connection tracking information. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2005 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/netfilter/nf_conntrack_compat.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_state.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
MODULE_DESCRIPTION("ip[6]_tables connection tracking state match module");
MODULE_ALIAS("ipt_state");
MODULE_ALIAS("ip6t_state");

static int
match(const struct sk_buff *skb,
      const struct net_device *in,
      const struct net_device *out,
      const void *matchinfo,
      int offset,
      unsigned int protoff,
      int *hotdrop)
{
	const struct xt_state_info *sinfo = matchinfo;
	enum ip_conntrack_info ctinfo;
	unsigned int statebit;

	if (nf_ct_is_untracked(skb))
		statebit = XT_STATE_UNTRACKED;
	else if (!nf_ct_get_ctinfo(skb, &ctinfo))
		statebit = XT_STATE_INVALID;
	else
		statebit = XT_STATE_BIT(ctinfo);

	return (sinfo->statemask & statebit);
}

static int check(const char *tablename,
		 const void *ip,
		 void *matchinfo,
		 unsigned int matchsize,
		 unsigned int hook_mask)
{
	if (matchsize != XT_ALIGN(sizeof(struct xt_state_info)))
		return 0;

	return 1;
}

static struct xt_match state_match = {
	.name		= "state",
	.match		= &match,
	.checkentry	= &check,
	.me		= THIS_MODULE,
};

static struct xt_match state6_match = {
	.name		= "state",
	.match		= &match,
	.checkentry	= &check,
	.me		= THIS_MODULE,
};

static int __init init(void)
{
	int ret;

	need_conntrack();

	ret = xt_register_match(AF_INET, &state_match);
	if (ret < 0)
		return ret;

	ret = xt_register_match(AF_INET6, &state6_match);
	if (ret < 0)
		xt_unregister_match(AF_INET,&state_match);

	return ret;
}

static void __exit fini(void)
{
	xt_unregister_match(AF_INET, &state_match);
	xt_unregister_match(AF_INET6, &state6_match);
}

module_init(init);
module_exit(fini);