ipt_connmark.c

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/* This kernel module matches connection mark values set by the
 * CONNMARK target
 *
 * Copyright (C) 2002,2004 MARA Systems AB <http://www.marasystems.com>
 * by Henrik Nordstrom <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/module.h>
#include <linux/skbuff.h>

MODULE_AUTHOR("Henrik Nordstrom <[e-mail]>");
MODULE_DESCRIPTION("IP tables connmark match module");
MODULE_LICENSE("GPL");

#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_connmark.h>
#include <linux/netfilter_ipv4/ip_conntrack.h>

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_connmark_info *info = matchinfo;
	enum ip_conntrack_info ctinfo;
	struct ip_conntrack *ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
	if (!ct)
		return 0;

	return ((ct->mark & info->mask) == info->mark) ^ info->invert;
}

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

	return 1;
}

static struct ipt_match connmark_match = {
	.name = "connmark",
	.match = &match,
	.checkentry = &checkentry,
	.me = THIS_MODULE
};

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

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

module_init(init);
module_exit(fini);