net/netfilter/xt_l2tp.c - linux - Git at Google

 /* Kernel module to match L2TP header parameters. */

 /* (C) 2013      James Chapman <jchapman@katalix.com>
  *
  * 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.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 #include <linux/module.h>
 #include <linux/skbuff.h>
 #include <linux/if_ether.h>
 #include <net/ip.h>
 #include <linux/ipv6.h>
 #include <net/ipv6.h>
 #include <net/udp.h>
 #include <linux/l2tp.h>

 #include <linux/netfilter_ipv4.h>
 #include <linux/netfilter_ipv6.h>
 #include <linux/netfilter_ipv4/ip_tables.h>
 #include <linux/netfilter_ipv6/ip6_tables.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_tcpudp.h>
 #include <linux/netfilter/xt_l2tp.h>

 /* L2TP header masks */
 #define L2TP_HDR_T_BIT	0x8000
 #define L2TP_HDR_L_BIT	0x4000
 #define L2TP_HDR_VER	0x000f

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
 MODULE_DESCRIPTION("Xtables: L2TP header match");
 MODULE_ALIAS("ipt_l2tp");
 MODULE_ALIAS("ip6t_l2tp");

 /* The L2TP fields that can be matched */
 struct l2tp_data {
 	u32 tid;
 	u32 sid;
 	u8 type;
 	u8 version;
 };

 union l2tp_val {
 	__be16 val16[2];
 	__be32 val32;
 };

 static bool l2tp_match(const struct xt_l2tp_info *info, struct l2tp_data *data)
 {
 	if ((info->flags & XT_L2TP_TYPE) && (info->type != data->type))
 		return false;

 	if ((info->flags & XT_L2TP_VERSION) && (info->version != data->version))
 		return false;

 	/* Check tid only for L2TPv3 control or any L2TPv2 packets */
 	if ((info->flags & XT_L2TP_TID) &&
 	    ((data->type == XT_L2TP_TYPE_CONTROL) || (data->version == 2)) &&
 	    (info->tid != data->tid))
 		return false;

 	/* Check sid only for L2TP data packets */
 	if ((info->flags & XT_L2TP_SID) && (data->type == XT_L2TP_TYPE_DATA) &&
 	    (info->sid != data->sid))
 		return false;

 	return true;
 }

 /* Parse L2TP header fields when UDP encapsulation is used. Handles
  * L2TPv2 and L2TPv3. Note the L2TPv3 control and data packets have a
  * different format. See
  * RFC2661, Section 3.1, L2TPv2 Header Format
  * RFC3931, Section 3.2.1, L2TPv3 Control Message Header
  * RFC3931, Section 3.2.2, L2TPv3 Data Message Header
  * RFC3931, Section 4.1.2.1, L2TPv3 Session Header over UDP
  */
 static bool l2tp_udp_mt(const struct sk_buff *skb, struct xt_action_param *par, u16 thoff)
 {
 	const struct xt_l2tp_info *info = par->matchinfo;
 	int uhlen = sizeof(struct udphdr);
 	int offs = thoff + uhlen;
 	union l2tp_val *lh;
 	union l2tp_val lhbuf;
 	u16 flags;
 	struct l2tp_data data = { 0, };

 	if (par->fragoff != 0)
 		return false;

 	/* Extract L2TP header fields. The flags in the first 16 bits
 	 * tell us where the other fields are.
 	 */
 	lh = skb_header_pointer(skb, offs, 2, &lhbuf);
 	if (lh == NULL)
 		return false;

 	flags = ntohs(lh->val16[0]);
 	if (flags & L2TP_HDR_T_BIT)
 		data.type = XT_L2TP_TYPE_CONTROL;
 	else
 		data.type = XT_L2TP_TYPE_DATA;
 	data.version = (u8) flags & L2TP_HDR_VER;

 	/* Now extract the L2TP tid/sid. These are in different places
 	 * for L2TPv2 (rfc2661) and L2TPv3 (rfc3931). For L2TPv2, we
 	 * must also check to see if the length field is present,
 	 * since this affects the offsets into the packet of the
 	 * tid/sid fields.
 	 */
 	if (data.version == 3) {
 		lh = skb_header_pointer(skb, offs + 4, 4, &lhbuf);
 		if (lh == NULL)
 			return false;
 		if (data.type == XT_L2TP_TYPE_CONTROL)
 			data.tid = ntohl(lh->val32);
 		else
 			data.sid = ntohl(lh->val32);
 	} else if (data.version == 2) {
 		if (flags & L2TP_HDR_L_BIT)
 			offs += 2;
 		lh = skb_header_pointer(skb, offs + 2, 4, &lhbuf);
 		if (lh == NULL)
 			return false;
 		data.tid = (u32) ntohs(lh->val16[0]);
 		data.sid = (u32) ntohs(lh->val16[1]);
 	} else
 		return false;

 	return l2tp_match(info, &data);
 }

 /* Parse L2TP header fields for IP encapsulation (no UDP header).
  * L2TPv3 data packets have a different form with IP encap. See
  * RC3931, Section 4.1.1.1, L2TPv3 Session Header over IP.
  * RC3931, Section 4.1.1.2, L2TPv3 Control and Data Traffic over IP.
  */
 static bool l2tp_ip_mt(const struct sk_buff *skb, struct xt_action_param *par, u16 thoff)
 {
 	const struct xt_l2tp_info *info = par->matchinfo;
 	union l2tp_val *lh;
 	union l2tp_val lhbuf;
 	struct l2tp_data data = { 0, };

 	/* For IP encap, the L2TP sid is the first 32-bits. */
 	lh = skb_header_pointer(skb, thoff, sizeof(lhbuf), &lhbuf);
 	if (lh == NULL)
 		return false;
 	if (lh->val32 == 0) {
 		/* Must be a control packet. The L2TP tid is further
 		 * into the packet.
 		 */
 		data.type = XT_L2TP_TYPE_CONTROL;
 		lh = skb_header_pointer(skb, thoff + 8, sizeof(lhbuf),
 					&lhbuf);
 		if (lh == NULL)
 			return false;
 		data.tid = ntohl(lh->val32);
 	} else {
 		data.sid = ntohl(lh->val32);
 		data.type = XT_L2TP_TYPE_DATA;
 	}

 	data.version = 3;

 	return l2tp_match(info, &data);
 }

 static bool l2tp_mt4(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	struct iphdr *iph = ip_hdr(skb);
 	u8 ipproto = iph->protocol;

 	/* l2tp_mt_check4 already restricts the transport protocol */
 	switch (ipproto) {
 	case IPPROTO_UDP:
 		return l2tp_udp_mt(skb, par, par->thoff);
 	case IPPROTO_L2TP:
 		return l2tp_ip_mt(skb, par, par->thoff);
 	}

 	return false;
 }

 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 static bool l2tp_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	unsigned int thoff = 0;
 	unsigned short fragoff = 0;
 	int ipproto;

 	ipproto = ipv6_find_hdr(skb, &thoff, -1, &fragoff, NULL);
 	if (fragoff != 0)
 		return false;

 	/* l2tp_mt_check6 already restricts the transport protocol */
 	switch (ipproto) {
 	case IPPROTO_UDP:
 		return l2tp_udp_mt(skb, par, thoff);
 	case IPPROTO_L2TP:
 		return l2tp_ip_mt(skb, par, thoff);
 	}

 	return false;
 }
 #endif

 static int l2tp_mt_check(const struct xt_mtchk_param *par)
 {
 	const struct xt_l2tp_info *info = par->matchinfo;

 	/* Check for invalid flags */
 	if (info->flags & ~(XT_L2TP_TID | XT_L2TP_SID | XT_L2TP_VERSION |
 			    XT_L2TP_TYPE)) {
 		pr_info("unknown flags: %x\n", info->flags);
 		return -EINVAL;
 	}

 	/* At least one of tid, sid or type=control must be specified */
 	if ((!(info->flags & XT_L2TP_TID)) &&
 	    (!(info->flags & XT_L2TP_SID)) &&
 	    ((!(info->flags & XT_L2TP_TYPE)) ||
 	     (info->type != XT_L2TP_TYPE_CONTROL))) {
 		pr_info("invalid flags combination: %x\n", info->flags);
 		return -EINVAL;
 	}

 	/* If version 2 is specified, check that incompatible params
 	 * are not supplied
 	 */
 	if (info->flags & XT_L2TP_VERSION) {
 		if ((info->version < 2) || (info->version > 3)) {
 			pr_info("wrong L2TP version: %u\n", info->version);
 			return -EINVAL;
 		}

 		if (info->version == 2) {
 			if ((info->flags & XT_L2TP_TID) &&
 			    (info->tid > 0xffff)) {
 				pr_info("v2 tid > 0xffff: %u\n", info->tid);
 				return -EINVAL;
 			}
 			if ((info->flags & XT_L2TP_SID) &&
 			    (info->sid > 0xffff)) {
 				pr_info("v2 sid > 0xffff: %u\n", info->sid);
 				return -EINVAL;
 			}
 		}
 	}

 	return 0;
 }

 static int l2tp_mt_check4(const struct xt_mtchk_param *par)
 {
 	const struct xt_l2tp_info *info = par->matchinfo;
 	const struct ipt_entry *e = par->entryinfo;
 	const struct ipt_ip *ip = &e->ip;
 	int ret;

 	ret = l2tp_mt_check(par);
 	if (ret != 0)
 		return ret;

 	if ((ip->proto != IPPROTO_UDP) &&
 	    (ip->proto != IPPROTO_L2TP)) {
 		pr_info("missing protocol rule (udp|l2tpip)\n");
 		return -EINVAL;
 	}

 	if ((ip->proto == IPPROTO_L2TP) &&
 	    (info->version == 2)) {
 		pr_info("v2 doesn't support IP mode\n");
 		return -EINVAL;
 	}

 	return 0;
 }

 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 static int l2tp_mt_check6(const struct xt_mtchk_param *par)
 {
 	const struct xt_l2tp_info *info = par->matchinfo;
 	const struct ip6t_entry *e = par->entryinfo;
 	const struct ip6t_ip6 *ip = &e->ipv6;
 	int ret;

 	ret = l2tp_mt_check(par);
 	if (ret != 0)
 		return ret;

 	if ((ip->proto != IPPROTO_UDP) &&
 	    (ip->proto != IPPROTO_L2TP)) {
 		pr_info("missing protocol rule (udp|l2tpip)\n");
 		return -EINVAL;
 	}

 	if ((ip->proto == IPPROTO_L2TP) &&
 	    (info->version == 2)) {
 		pr_info("v2 doesn't support IP mode\n");
 		return -EINVAL;
 	}

 	return 0;
 }
 #endif

 static struct xt_match l2tp_mt_reg[] __read_mostly = {
 	{
 		.name      = "l2tp",
 		.revision  = 0,
 		.family    = NFPROTO_IPV4,
 		.match     = l2tp_mt4,
 		.matchsize = XT_ALIGN(sizeof(struct xt_l2tp_info)),
 		.checkentry = l2tp_mt_check4,
 		.hooks     = ((1 << NF_INET_PRE_ROUTING) |
 			      (1 << NF_INET_LOCAL_IN) |
 			      (1 << NF_INET_LOCAL_OUT) |
 			      (1 << NF_INET_FORWARD)),
 		.me        = THIS_MODULE,
 	},
 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 	{
 		.name      = "l2tp",
 		.revision  = 0,
 		.family    = NFPROTO_IPV6,
 		.match     = l2tp_mt6,
 		.matchsize = XT_ALIGN(sizeof(struct xt_l2tp_info)),
 		.checkentry = l2tp_mt_check6,
 		.hooks     = ((1 << NF_INET_PRE_ROUTING) |
 			      (1 << NF_INET_LOCAL_IN) |
 			      (1 << NF_INET_LOCAL_OUT) |
 			      (1 << NF_INET_FORWARD)),
 		.me        = THIS_MODULE,
 	},
 #endif
 };

 static int __init l2tp_mt_init(void)
 {
 	return xt_register_matches(&l2tp_mt_reg[0], ARRAY_SIZE(l2tp_mt_reg));
 }

 static void __exit l2tp_mt_exit(void)
 {
 	xt_unregister_matches(&l2tp_mt_reg[0], ARRAY_SIZE(l2tp_mt_reg));
 }

 module_init(l2tp_mt_init);
 module_exit(l2tp_mt_exit);
	/* Kernel module to match L2TP header parameters. */

	/* (C) 2013 James Chapman <jchapman@katalix.com>
	*
	* 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.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
	#include <linux/module.h>
	#include <linux/skbuff.h>
	#include <linux/if_ether.h>
	#include <net/ip.h>
	#include <linux/ipv6.h>
	#include <net/ipv6.h>
	#include <net/udp.h>
	#include <linux/l2tp.h>

	#include <linux/netfilter_ipv4.h>
	#include <linux/netfilter_ipv6.h>
	#include <linux/netfilter_ipv4/ip_tables.h>
	#include <linux/netfilter_ipv6/ip6_tables.h>
	#include <linux/netfilter/x_tables.h>
	#include <linux/netfilter/xt_tcpudp.h>
	#include <linux/netfilter/xt_l2tp.h>

	/* L2TP header masks */
	#define L2TP_HDR_T_BIT 0x8000
	#define L2TP_HDR_L_BIT 0x4000
	#define L2TP_HDR_VER 0x000f

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
	MODULE_DESCRIPTION("Xtables: L2TP header match");
	MODULE_ALIAS("ipt_l2tp");
	MODULE_ALIAS("ip6t_l2tp");

	/* The L2TP fields that can be matched */
	struct l2tp_data {
	u32 tid;
	u32 sid;
	u8 type;
	u8 version;
	};

	union l2tp_val {
	__be16 val16[2];
	__be32 val32;
	};

	static bool l2tp_match(const struct xt_l2tp_info info, struct l2tp_data data)
	{
	if ((info->flags & XT_L2TP_TYPE) && (info->type != data->type))
	return false;

	if ((info->flags & XT_L2TP_VERSION) && (info->version != data->version))
	return false;

	/* Check tid only for L2TPv3 control or any L2TPv2 packets */
	if ((info->flags & XT_L2TP_TID) &&
	((data->type == XT_L2TP_TYPE_CONTROL) \|\| (data->version == 2)) &&
	(info->tid != data->tid))
	return false;

	/* Check sid only for L2TP data packets */
	if ((info->flags & XT_L2TP_SID) && (data->type == XT_L2TP_TYPE_DATA) &&
	(info->sid != data->sid))
	return false;

	return true;
	}

	/* Parse L2TP header fields when UDP encapsulation is used. Handles
	* L2TPv2 and L2TPv3. Note the L2TPv3 control and data packets have a
	* different format. See
	* RFC2661, Section 3.1, L2TPv2 Header Format
	* RFC3931, Section 3.2.1, L2TPv3 Control Message Header
	* RFC3931, Section 3.2.2, L2TPv3 Data Message Header
	* RFC3931, Section 4.1.2.1, L2TPv3 Session Header over UDP
	*/
	static bool l2tp_udp_mt(const struct sk_buff skb, struct xt_action_param par, u16 thoff)
	{
	const struct xt_l2tp_info *info = par->matchinfo;
	int uhlen = sizeof(struct udphdr);
	int offs = thoff + uhlen;
	union l2tp_val *lh;
	union l2tp_val lhbuf;
	u16 flags;
	struct l2tp_data data = { 0, };

	if (par->fragoff != 0)
	return false;

	/* Extract L2TP header fields. The flags in the first 16 bits
	* tell us where the other fields are.
	*/
	lh = skb_header_pointer(skb, offs, 2, &lhbuf);
	if (lh == NULL)
	return false;

	flags = ntohs(lh->val16[0]);
	if (flags & L2TP_HDR_T_BIT)
	data.type = XT_L2TP_TYPE_CONTROL;
	else
	data.type = XT_L2TP_TYPE_DATA;
	data.version = (u8) flags & L2TP_HDR_VER;

	/* Now extract the L2TP tid/sid. These are in different places
	* for L2TPv2 (rfc2661) and L2TPv3 (rfc3931). For L2TPv2, we
	* must also check to see if the length field is present,
	* since this affects the offsets into the packet of the
	* tid/sid fields.
	*/
	if (data.version == 3) {
	lh = skb_header_pointer(skb, offs + 4, 4, &lhbuf);
	if (lh == NULL)
	return false;
	if (data.type == XT_L2TP_TYPE_CONTROL)
	data.tid = ntohl(lh->val32);
	else
	data.sid = ntohl(lh->val32);
	} else if (data.version == 2) {
	if (flags & L2TP_HDR_L_BIT)
	offs += 2;
	lh = skb_header_pointer(skb, offs + 2, 4, &lhbuf);
	if (lh == NULL)
	return false;
	data.tid = (u32) ntohs(lh->val16[0]);
	data.sid = (u32) ntohs(lh->val16[1]);
	} else
	return false;

	return l2tp_match(info, &data);
	}

	/* Parse L2TP header fields for IP encapsulation (no UDP header).
	* L2TPv3 data packets have a different form with IP encap. See
	* RC3931, Section 4.1.1.1, L2TPv3 Session Header over IP.
	* RC3931, Section 4.1.1.2, L2TPv3 Control and Data Traffic over IP.
	*/
	static bool l2tp_ip_mt(const struct sk_buff skb, struct xt_action_param par, u16 thoff)
	{
	const struct xt_l2tp_info *info = par->matchinfo;
	union l2tp_val *lh;
	union l2tp_val lhbuf;
	struct l2tp_data data = { 0, };

	/* For IP encap, the L2TP sid is the first 32-bits. */
	lh = skb_header_pointer(skb, thoff, sizeof(lhbuf), &lhbuf);
	if (lh == NULL)
	return false;
	if (lh->val32 == 0) {
	/* Must be a control packet. The L2TP tid is further
	* into the packet.
	*/
	data.type = XT_L2TP_TYPE_CONTROL;
	lh = skb_header_pointer(skb, thoff + 8, sizeof(lhbuf),
	&lhbuf);
	if (lh == NULL)
	return false;
	data.tid = ntohl(lh->val32);
	} else {
	data.sid = ntohl(lh->val32);
	data.type = XT_L2TP_TYPE_DATA;
	}

	data.version = 3;

	return l2tp_match(info, &data);
	}

	static bool l2tp_mt4(const struct sk_buff skb, struct xt_action_param par)
	{
	struct iphdr *iph = ip_hdr(skb);
	u8 ipproto = iph->protocol;

	/* l2tp_mt_check4 already restricts the transport protocol */
	switch (ipproto) {
	case IPPROTO_UDP:
	return l2tp_udp_mt(skb, par, par->thoff);
	case IPPROTO_L2TP:
	return l2tp_ip_mt(skb, par, par->thoff);
	}

	return false;
	}

	#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
	static bool l2tp_mt6(const struct sk_buff skb, struct xt_action_param par)
	{
	unsigned int thoff = 0;
	unsigned short fragoff = 0;
	int ipproto;

	ipproto = ipv6_find_hdr(skb, &thoff, -1, &fragoff, NULL);
	if (fragoff != 0)
	return false;

	/* l2tp_mt_check6 already restricts the transport protocol */
	switch (ipproto) {
	case IPPROTO_UDP:
	return l2tp_udp_mt(skb, par, thoff);
	case IPPROTO_L2TP:
	return l2tp_ip_mt(skb, par, thoff);
	}

	return false;
	}
	#endif

	static int l2tp_mt_check(const struct xt_mtchk_param *par)
	{
	const struct xt_l2tp_info *info = par->matchinfo;

	/* Check for invalid flags */
	if (info->flags & ~(XT_L2TP_TID \| XT_L2TP_SID \| XT_L2TP_VERSION \|
	XT_L2TP_TYPE)) {
	pr_info("unknown flags: %x\n", info->flags);
	return -EINVAL;
	}

	/* At least one of tid, sid or type=control must be specified */
	if ((!(info->flags & XT_L2TP_TID)) &&
	(!(info->flags & XT_L2TP_SID)) &&
	((!(info->flags & XT_L2TP_TYPE)) \|\|
	(info->type != XT_L2TP_TYPE_CONTROL))) {
	pr_info("invalid flags combination: %x\n", info->flags);
	return -EINVAL;
	}

	/* If version 2 is specified, check that incompatible params
	* are not supplied
	*/
	if (info->flags & XT_L2TP_VERSION) {
	if ((info->version < 2) \|\| (info->version > 3)) {
	pr_info("wrong L2TP version: %u\n", info->version);
	return -EINVAL;
	}

	if (info->version == 2) {
	if ((info->flags & XT_L2TP_TID) &&
	(info->tid > 0xffff)) {
	pr_info("v2 tid > 0xffff: %u\n", info->tid);
	return -EINVAL;
	}
	if ((info->flags & XT_L2TP_SID) &&
	(info->sid > 0xffff)) {
	pr_info("v2 sid > 0xffff: %u\n", info->sid);
	return -EINVAL;
	}
	}
	}

	return 0;
	}

	static int l2tp_mt_check4(const struct xt_mtchk_param *par)
	{
	const struct xt_l2tp_info *info = par->matchinfo;
	const struct ipt_entry *e = par->entryinfo;
	const struct ipt_ip *ip = &e->ip;
	int ret;

	ret = l2tp_mt_check(par);
	if (ret != 0)
	return ret;

	if ((ip->proto != IPPROTO_UDP) &&
	(ip->proto != IPPROTO_L2TP)) {
	pr_info("missing protocol rule (udp\|l2tpip)\n");
	return -EINVAL;
	}

	if ((ip->proto == IPPROTO_L2TP) &&
	(info->version == 2)) {
	pr_info("v2 doesn't support IP mode\n");
	return -EINVAL;
	}

	return 0;
	}

	#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
	static int l2tp_mt_check6(const struct xt_mtchk_param *par)
	{
	const struct xt_l2tp_info *info = par->matchinfo;
	const struct ip6t_entry *e = par->entryinfo;
	const struct ip6t_ip6 *ip = &e->ipv6;
	int ret;

	ret = l2tp_mt_check(par);
	if (ret != 0)
	return ret;

	if ((ip->proto != IPPROTO_UDP) &&
	(ip->proto != IPPROTO_L2TP)) {
	pr_info("missing protocol rule (udp\|l2tpip)\n");
	return -EINVAL;
	}

	if ((ip->proto == IPPROTO_L2TP) &&
	(info->version == 2)) {
	pr_info("v2 doesn't support IP mode\n");
	return -EINVAL;
	}

	return 0;
	}
	#endif

	static struct xt_match l2tp_mt_reg[] __read_mostly = {
	{
	.name = "l2tp",
	.revision = 0,
	.family = NFPROTO_IPV4,
	.match = l2tp_mt4,
	.matchsize = XT_ALIGN(sizeof(struct xt_l2tp_info)),
	.checkentry = l2tp_mt_check4,
	.hooks = ((1 << NF_INET_PRE_ROUTING) \|
	(1 << NF_INET_LOCAL_IN) \|
	(1 << NF_INET_LOCAL_OUT) \|
	(1 << NF_INET_FORWARD)),
	.me = THIS_MODULE,
	},
	#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
	{
	.name = "l2tp",
	.revision = 0,
	.family = NFPROTO_IPV6,
	.match = l2tp_mt6,
	.matchsize = XT_ALIGN(sizeof(struct xt_l2tp_info)),
	.checkentry = l2tp_mt_check6,
	.hooks = ((1 << NF_INET_PRE_ROUTING) \|
	(1 << NF_INET_LOCAL_IN) \|
	(1 << NF_INET_LOCAL_OUT) \|
	(1 << NF_INET_FORWARD)),
	.me = THIS_MODULE,
	},
	#endif
	};

	static int __init l2tp_mt_init(void)
	{
	return xt_register_matches(&l2tp_mt_reg[0], ARRAY_SIZE(l2tp_mt_reg));
	}

	static void __exit l2tp_mt_exit(void)
	{
	xt_unregister_matches(&l2tp_mt_reg[0], ARRAY_SIZE(l2tp_mt_reg));
	}

	module_init(l2tp_mt_init);
	module_exit(l2tp_mt_exit);