net/netfilter/xt_CONNMARK.c

/*
 *	xt_CONNMARK - Netfilter module to modify the connection mark values
 *
 *	Copyright (C) 2002,2004 MARA Systems AB <http://www.marasystems.com>
 *	by Henrik Nordstrom <hno@marasystems.com>
 *	Copyright © CC Computer Consultants GmbH, 2007 - 2008
 *	Jan Engelhardt <jengelh@computergmbh.de>
 *
 * 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>
#include <linux/ip.h>
#include <net/checksum.h>

MODULE_AUTHOR("Henrik Nordstrom <hno@marasystems.com>");
MODULE_DESCRIPTION("Xtables: connection mark modification");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_CONNMARK");
MODULE_ALIAS("ip6t_CONNMARK");

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_CONNMARK.h>
#include <net/netfilter/nf_conntrack_ecache.h>

static unsigned int
connmark_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
	const struct xt_connmark_tginfo1 *info = par->targinfo;
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct;
	u_int32_t newmark;

	ct = nf_ct_get(skb, &ctinfo);
	if (ct == NULL)
		return XT_CONTINUE;

	switch (info->mode) {
	case XT_CONNMARK_SET:
		newmark = (ct->mark & ~info->ctmask) ^ info->ctmark;
		if (ct->mark != newmark) {
			ct->mark = newmark;
			nf_conntrack_event_cache(IPCT_MARK, ct);
		}
		break;
	case XT_CONNMARK_SAVE:
		newmark = (ct->mark & ~info->ctmask) ^
		          (skb->mark & info->nfmask);
		if (ct->mark != newmark) {
			ct->mark = newmark;
			nf_conntrack_event_cache(IPCT_MARK, ct);
		}
		break;
	case XT_CONNMARK_RESTORE:
		newmark = (skb->mark & ~info->nfmask) ^
		          (ct->mark & info->ctmask);
		skb->mark = newmark;
		break;
	}

	return XT_CONTINUE;
}

static bool connmark_tg_check(const struct xt_tgchk_param *par)
{
	if (nf_ct_l3proto_try_module_get(par->family) < 0) {
		printk(KERN_WARNING "cannot load conntrack support for "
		       "proto=%u\n", par->family);
		return false;
	}
	return true;
}

static void connmark_tg_destroy(const struct xt_tgdtor_param *par)
{
	nf_ct_l3proto_module_put(par->family);
}

static struct xt_target connmark_tg_reg __read_mostly = {
	.name           = "CONNMARK",
	.revision       = 1,
	.family         = NFPROTO_UNSPEC,
	.checkentry     = connmark_tg_check,
	.target         = connmark_tg,
	.targetsize     = sizeof(struct xt_connmark_tginfo1),
	.destroy        = connmark_tg_destroy,
	.me             = THIS_MODULE,
};

static int __init connmark_tg_init(void)
{
	return xt_register_target(&connmark_tg_reg);
}

static void __exit connmark_tg_exit(void)
{
	xt_unregister_target(&connmark_tg_reg);
}

module_init(connmark_tg_init);
module_exit(connmark_tg_exit);