net/ipv4/netfilter/ipt_state.c

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

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 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 <linux/netfilter_ipv4/ip_conntrack.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_state.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
MODULE_DESCRIPTION("iptables connection tracking state match module");

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

	if (skb->nfct == &ip_conntrack_untracked.ct_general)
		statebit = IPT_STATE_UNTRACKED;
	else if (!ip_conntrack_get(skb, &ctinfo))
		statebit = IPT_STATE_INVALID;
	else
		statebit = IPT_STATE_BIT(ctinfo);

	return (sinfo->statemask & statebit);
}

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

	return 1;
}

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

static int __init init(void)
{
	need_ip_conntrack();
	return ipt_register_match(&state_match);
}

static void __exit fini(void)
{
	ipt_unregister_match(&state_match);
}

module_init(init);
module_exit(fini);