include/net/6lowpan.h - arm/linux - Git at Google

 /*
  * Copyright 2011, Siemens AG
  * written by Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
  */

 /*
  * Based on patches from Jon Smirl <jonsmirl@gmail.com>
  * Copyright (c) 2011 Jon Smirl <jonsmirl@gmail.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.
  *
  * 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.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */

 /* Jon's code is based on 6lowpan implementation for Contiki which is:
  * Copyright (c) 2008, Swedish Institute of Computer Science.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the Institute nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */

 #ifndef __6LOWPAN_H__
 #define __6LOWPAN_H__

 #include <linux/debugfs.h>

 #include <net/ipv6.h>
 #include <net/net_namespace.h>

 /* special link-layer handling */
 #include <net/mac802154.h>

 #define EUI64_ADDR_LEN		8

 #define LOWPAN_NHC_MAX_ID_LEN	1
 /* Maximum next header compression length which we currently support inclusive
  * possible inline data.
  */
 #define LOWPAN_NHC_MAX_HDR_LEN	(sizeof(struct udphdr))
 /* Max IPHC Header len without IPv6 hdr specific inline data.
  * Useful for getting the "extra" bytes we need at worst case compression.
  *
  * LOWPAN_IPHC + CID + LOWPAN_NHC_MAX_ID_LEN
  */
 #define LOWPAN_IPHC_MAX_HEADER_LEN	(2 + 1 + LOWPAN_NHC_MAX_ID_LEN)
 /* Maximum worst case IPHC header buffer size */
 #define LOWPAN_IPHC_MAX_HC_BUF_LEN	(sizeof(struct ipv6hdr) +	\
 					 LOWPAN_IPHC_MAX_HEADER_LEN +	\
 					 LOWPAN_NHC_MAX_HDR_LEN)
 /* SCI/DCI is 4 bit width, so we have maximum 16 entries */
 #define LOWPAN_IPHC_CTX_TABLE_SIZE	(1 << 4)

 #define LOWPAN_DISPATCH_IPV6		0x41 /* 01000001 = 65 */
 #define LOWPAN_DISPATCH_IPHC		0x60 /* 011xxxxx = ... */
 #define LOWPAN_DISPATCH_IPHC_MASK	0xe0

 static inline bool lowpan_is_ipv6(u8 dispatch)
 {
 	return dispatch == LOWPAN_DISPATCH_IPV6;
 }

 static inline bool lowpan_is_iphc(u8 dispatch)
 {
 	return (dispatch & LOWPAN_DISPATCH_IPHC_MASK) == LOWPAN_DISPATCH_IPHC;
 }

 #define LOWPAN_PRIV_SIZE(llpriv_size)	\
 	(sizeof(struct lowpan_dev) + llpriv_size)

 enum lowpan_lltypes {
 	LOWPAN_LLTYPE_BTLE,
 	LOWPAN_LLTYPE_IEEE802154,
 };

 enum lowpan_iphc_ctx_flags {
 	LOWPAN_IPHC_CTX_FLAG_ACTIVE,
 	LOWPAN_IPHC_CTX_FLAG_COMPRESSION,
 };

 struct lowpan_iphc_ctx {
 	u8 id;
 	struct in6_addr pfx;
 	u8 plen;
 	unsigned long flags;
 };

 struct lowpan_iphc_ctx_table {
 	spinlock_t lock;
 	const struct lowpan_iphc_ctx_ops *ops;
 	struct lowpan_iphc_ctx table[LOWPAN_IPHC_CTX_TABLE_SIZE];
 };

 static inline bool lowpan_iphc_ctx_is_active(const struct lowpan_iphc_ctx *ctx)
 {
 	return test_bit(LOWPAN_IPHC_CTX_FLAG_ACTIVE, &ctx->flags);
 }

 static inline bool
 lowpan_iphc_ctx_is_compression(const struct lowpan_iphc_ctx *ctx)
 {
 	return test_bit(LOWPAN_IPHC_CTX_FLAG_COMPRESSION, &ctx->flags);
 }

 struct lowpan_dev {
 	enum lowpan_lltypes lltype;
 	struct dentry *iface_debugfs;
 	struct lowpan_iphc_ctx_table ctx;

 	/* must be last */
 	u8 priv[0] __aligned(sizeof(void *));
 };

 struct lowpan_802154_neigh {
 	__le16 short_addr;
 };

 static inline
 struct lowpan_802154_neigh *lowpan_802154_neigh(void *neigh_priv)
 {
 	return neigh_priv;
 }

 static inline
 struct lowpan_dev *lowpan_dev(const struct net_device *dev)
 {
 	return netdev_priv(dev);
 }

 /* private device info */
 struct lowpan_802154_dev {
 	struct net_device	*wdev; /* wpan device ptr */
 	u16			fragment_tag;
 };

 static inline struct
 lowpan_802154_dev *lowpan_802154_dev(const struct net_device *dev)
 {
 	return (struct lowpan_802154_dev *)lowpan_dev(dev)->priv;
 }

 struct lowpan_802154_cb {
 	u16 d_tag;
 	unsigned int d_size;
 	u8 d_offset;
 };

 static inline
 struct lowpan_802154_cb *lowpan_802154_cb(const struct sk_buff *skb)
 {
 	BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(skb->cb));
 	return (struct lowpan_802154_cb *)skb->cb;
 }

 static inline void lowpan_iphc_uncompress_eui64_lladdr(struct in6_addr *ipaddr,
 						       const void *lladdr)
 {
 	/* fe:80::XXXX:XXXX:XXXX:XXXX
 	 *        \_________________/
 	 *              hwaddr
 	 */
 	ipaddr->s6_addr[0] = 0xFE;
 	ipaddr->s6_addr[1] = 0x80;
 	memcpy(&ipaddr->s6_addr[8], lladdr, EUI64_ADDR_LEN);
 	/* second bit-flip (Universe/Local)
 	 * is done according RFC2464
 	 */
 	ipaddr->s6_addr[8] ^= 0x02;
 }

 static inline void lowpan_iphc_uncompress_eui48_lladdr(struct in6_addr *ipaddr,
 						       const void *lladdr)
 {
 	/* fe:80::XXXX:XXff:feXX:XXXX
 	 *        \_________________/
 	 *              hwaddr
 	 */
 	ipaddr->s6_addr[0] = 0xFE;
 	ipaddr->s6_addr[1] = 0x80;
 	memcpy(&ipaddr->s6_addr[8], lladdr, 3);
 	ipaddr->s6_addr[11] = 0xFF;
 	ipaddr->s6_addr[12] = 0xFE;
 	memcpy(&ipaddr->s6_addr[13], lladdr + 3, 3);
 }

 #ifdef DEBUG
 /* print data in line */
 static inline void raw_dump_inline(const char *caller, char *msg,
 				   const unsigned char *buf, int len)
 {
 	if (msg)
 		pr_debug("%s():%s: ", caller, msg);

 	print_hex_dump_debug("", DUMP_PREFIX_NONE, 16, 1, buf, len, false);
 }

 /* print data in a table format:
  *
  * addr: xx xx xx xx xx xx
  * addr: xx xx xx xx xx xx
  * ...
  */
 static inline void raw_dump_table(const char *caller, char *msg,
 				  const unsigned char *buf, int len)
 {
 	if (msg)
 		pr_debug("%s():%s:\n", caller, msg);

 	print_hex_dump_debug("\t", DUMP_PREFIX_OFFSET, 16, 1, buf, len, false);
 }
 #else
 static inline void raw_dump_table(const char *caller, char *msg,
 				  const unsigned char *buf, int len) { }
 static inline void raw_dump_inline(const char *caller, char *msg,
 				   const unsigned char *buf, int len) { }
 #endif

 /**
  * lowpan_fetch_skb - getting inline data from 6LoWPAN header
  *
  * This function will pull data from sk buffer and put it into data to
  * remove the 6LoWPAN inline data. This function returns true if the
  * sk buffer is too small to pull the amount of data which is specified
  * by len.
  *
  * @skb: the buffer where the inline data should be pulled from.
  * @data: destination buffer for the inline data.
  * @len: amount of data which should be pulled in bytes.
  */
 static inline bool lowpan_fetch_skb(struct sk_buff *skb, void *data,
 				    unsigned int len)
 {
 	if (unlikely(!pskb_may_pull(skb, len)))
 		return true;

 	skb_copy_from_linear_data(skb, data, len);
 	skb_pull(skb, len);

 	return false;
 }

 static inline bool lowpan_802154_is_valid_src_short_addr(__le16 addr)
 {
 	/* First bit of addr is multicast, reserved or 802.15.4 specific */
 	return !(addr & cpu_to_le16(0x8000));
 }

 static inline void lowpan_push_hc_data(u8 **hc_ptr, const void *data,
 				       const size_t len)
 {
 	memcpy(*hc_ptr, data, len);
 	*hc_ptr += len;
 }

 int lowpan_register_netdevice(struct net_device *dev,
 			      enum lowpan_lltypes lltype);
 int lowpan_register_netdev(struct net_device *dev,
 			   enum lowpan_lltypes lltype);
 void lowpan_unregister_netdevice(struct net_device *dev);
 void lowpan_unregister_netdev(struct net_device *dev);

 /**
  * lowpan_header_decompress - replace 6LoWPAN header with IPv6 header
  *
  * This function replaces the IPHC 6LoWPAN header which should be pointed at
  * skb->data and skb_network_header, with the IPv6 header.
  * It would be nice that the caller have the necessary headroom of IPv6 header
  * and greatest Transport layer header, this would reduce the overhead for
  * reallocate headroom.
  *
  * @skb: the buffer which should be manipulate.
  * @dev: the lowpan net device pointer.
  * @daddr: destination lladdr of mac header which is used for compression
  *	methods.
  * @saddr: source lladdr of mac header which is used for compression
  *	methods.
  */
 int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
 			     const void *daddr, const void *saddr);

 /**
  * lowpan_header_compress - replace IPv6 header with 6LoWPAN header
  *
  * This function replaces the IPv6 header which should be pointed at
  * skb->data and skb_network_header, with the IPHC 6LoWPAN header.
  * The caller need to be sure that the sk buffer is not shared and at have
  * at least a headroom which is smaller or equal LOWPAN_IPHC_MAX_HEADER_LEN,
  * which is the IPHC "more bytes than IPv6 header" at worst case.
  *
  * @skb: the buffer which should be manipulate.
  * @dev: the lowpan net device pointer.
  * @daddr: destination lladdr of mac header which is used for compression
  *	methods.
  * @saddr: source lladdr of mac header which is used for compression
  *	methods.
  */
 int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
 			   const void *daddr, const void *saddr);

 #endif /* __6LOWPAN_H__ */
	/*
	* Copyright 2011, Siemens AG
	* written by Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
	*/

	/*
	* Based on patches from Jon Smirl <jonsmirl@gmail.com>
	* Copyright (c) 2011 Jon Smirl <jonsmirl@gmail.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.
	*
	* 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.,
	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
	*/

	/* Jon's code is based on 6lowpan implementation for Contiki which is:
	* Copyright (c) 2008, Swedish Institute of Computer Science.
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. Neither the name of the Institute nor the names of its contributors
	* may be used to endorse or promote products derived from this software
	* without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*/

	#ifndef __6LOWPAN_H__
	#define __6LOWPAN_H__

	#include <linux/debugfs.h>

	#include <net/ipv6.h>
	#include <net/net_namespace.h>

	/* special link-layer handling */
	#include <net/mac802154.h>

	#define EUI64_ADDR_LEN 8

	#define LOWPAN_NHC_MAX_ID_LEN 1
	/* Maximum next header compression length which we currently support inclusive
	* possible inline data.
	*/
	#define LOWPAN_NHC_MAX_HDR_LEN (sizeof(struct udphdr))
	/* Max IPHC Header len without IPv6 hdr specific inline data.
	* Useful for getting the "extra" bytes we need at worst case compression.
	*
	* LOWPAN_IPHC + CID + LOWPAN_NHC_MAX_ID_LEN
	*/
	#define LOWPAN_IPHC_MAX_HEADER_LEN (2 + 1 + LOWPAN_NHC_MAX_ID_LEN)
	/* Maximum worst case IPHC header buffer size */
	#define LOWPAN_IPHC_MAX_HC_BUF_LEN (sizeof(struct ipv6hdr) + \
	LOWPAN_IPHC_MAX_HEADER_LEN + \
	LOWPAN_NHC_MAX_HDR_LEN)
	/* SCI/DCI is 4 bit width, so we have maximum 16 entries */
	#define LOWPAN_IPHC_CTX_TABLE_SIZE (1 << 4)

	#define LOWPAN_DISPATCH_IPV6 0x41 /* 01000001 = 65 */
	#define LOWPAN_DISPATCH_IPHC 0x60 /* 011xxxxx = ... */
	#define LOWPAN_DISPATCH_IPHC_MASK 0xe0

	static inline bool lowpan_is_ipv6(u8 dispatch)
	{
	return dispatch == LOWPAN_DISPATCH_IPV6;
	}

	static inline bool lowpan_is_iphc(u8 dispatch)
	{
	return (dispatch & LOWPAN_DISPATCH_IPHC_MASK) == LOWPAN_DISPATCH_IPHC;
	}

	#define LOWPAN_PRIV_SIZE(llpriv_size) \
	(sizeof(struct lowpan_dev) + llpriv_size)

	enum lowpan_lltypes {
	LOWPAN_LLTYPE_BTLE,
	LOWPAN_LLTYPE_IEEE802154,
	};

	enum lowpan_iphc_ctx_flags {
	LOWPAN_IPHC_CTX_FLAG_ACTIVE,
	LOWPAN_IPHC_CTX_FLAG_COMPRESSION,
	};

	struct lowpan_iphc_ctx {
	u8 id;
	struct in6_addr pfx;
	u8 plen;
	unsigned long flags;
	};

	struct lowpan_iphc_ctx_table {
	spinlock_t lock;
	const struct lowpan_iphc_ctx_ops *ops;
	struct lowpan_iphc_ctx table[LOWPAN_IPHC_CTX_TABLE_SIZE];
	};

	static inline bool lowpan_iphc_ctx_is_active(const struct lowpan_iphc_ctx *ctx)
	{
	return test_bit(LOWPAN_IPHC_CTX_FLAG_ACTIVE, &ctx->flags);
	}

	static inline bool
	lowpan_iphc_ctx_is_compression(const struct lowpan_iphc_ctx *ctx)
	{
	return test_bit(LOWPAN_IPHC_CTX_FLAG_COMPRESSION, &ctx->flags);
	}

	struct lowpan_dev {
	enum lowpan_lltypes lltype;
	struct dentry *iface_debugfs;
	struct lowpan_iphc_ctx_table ctx;

	/* must be last */
	u8 priv[0] __aligned(sizeof(void *));
	};

	struct lowpan_802154_neigh {
	__le16 short_addr;
	};

	static inline
	struct lowpan_802154_neigh lowpan_802154_neigh(void neigh_priv)
	{
	return neigh_priv;
	}

	static inline
	struct lowpan_dev lowpan_dev(const struct net_device dev)
	{
	return netdev_priv(dev);
	}

	/* private device info */
	struct lowpan_802154_dev {
	struct net_device wdev; / wpan device ptr */
	u16 fragment_tag;
	};

	static inline struct
	lowpan_802154_dev lowpan_802154_dev(const struct net_device dev)
	{
	return (struct lowpan_802154_dev *)lowpan_dev(dev)->priv;
	}

	struct lowpan_802154_cb {
	u16 d_tag;
	unsigned int d_size;
	u8 d_offset;
	};

	static inline
	struct lowpan_802154_cb lowpan_802154_cb(const struct sk_buff skb)
	{
	BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(skb->cb));
	return (struct lowpan_802154_cb *)skb->cb;
	}

	static inline void lowpan_iphc_uncompress_eui64_lladdr(struct in6_addr *ipaddr,
	const void *lladdr)
	{
	/* fe:80::XXXX:XXXX:XXXX:XXXX
	* \_________________/
	* hwaddr
	*/
	ipaddr->s6_addr[0] = 0xFE;
	ipaddr->s6_addr[1] = 0x80;
	memcpy(&ipaddr->s6_addr[8], lladdr, EUI64_ADDR_LEN);
	/* second bit-flip (Universe/Local)
	* is done according RFC2464
	*/
	ipaddr->s6_addr[8] ^= 0x02;
	}

	static inline void lowpan_iphc_uncompress_eui48_lladdr(struct in6_addr *ipaddr,
	const void *lladdr)
	{
	/* fe:80::XXXX:XXff:feXX:XXXX
	* \_________________/
	* hwaddr
	*/
	ipaddr->s6_addr[0] = 0xFE;
	ipaddr->s6_addr[1] = 0x80;
	memcpy(&ipaddr->s6_addr[8], lladdr, 3);
	ipaddr->s6_addr[11] = 0xFF;
	ipaddr->s6_addr[12] = 0xFE;
	memcpy(&ipaddr->s6_addr[13], lladdr + 3, 3);
	}

	#ifdef DEBUG
	/* print data in line */
	static inline void raw_dump_inline(const char caller, char msg,
	const unsigned char *buf, int len)
	{
	if (msg)
	pr_debug("%s():%s: ", caller, msg);

	print_hex_dump_debug("", DUMP_PREFIX_NONE, 16, 1, buf, len, false);
	}

	/* print data in a table format:
	*
	* addr: xx xx xx xx xx xx
	* addr: xx xx xx xx xx xx
	* ...
	*/
	static inline void raw_dump_table(const char caller, char msg,
	const unsigned char *buf, int len)
	{
	if (msg)
	pr_debug("%s():%s:\n", caller, msg);

	print_hex_dump_debug("\t", DUMP_PREFIX_OFFSET, 16, 1, buf, len, false);
	}
	#else
	static inline void raw_dump_table(const char caller, char msg,
	const unsigned char *buf, int len) { }
	static inline void raw_dump_inline(const char caller, char msg,
	const unsigned char *buf, int len) { }
	#endif

	/**
	* lowpan_fetch_skb - getting inline data from 6LoWPAN header
	*
	* This function will pull data from sk buffer and put it into data to
	* remove the 6LoWPAN inline data. This function returns true if the
	* sk buffer is too small to pull the amount of data which is specified
	* by len.
	*
	* @skb: the buffer where the inline data should be pulled from.
	* @data: destination buffer for the inline data.
	* @len: amount of data which should be pulled in bytes.
	*/
	static inline bool lowpan_fetch_skb(struct sk_buff skb, void data,
	unsigned int len)
	{
	if (unlikely(!pskb_may_pull(skb, len)))
	return true;

	skb_copy_from_linear_data(skb, data, len);
	skb_pull(skb, len);

	return false;
	}

	static inline bool lowpan_802154_is_valid_src_short_addr(__le16 addr)
	{
	/* First bit of addr is multicast, reserved or 802.15.4 specific */
	return !(addr & cpu_to_le16(0x8000));
	}

	static inline void lowpan_push_hc_data(u8 *hc_ptr, const void data,
	const size_t len)
	{
	memcpy(*hc_ptr, data, len);
	*hc_ptr += len;
	}

	int lowpan_register_netdevice(struct net_device *dev,
	enum lowpan_lltypes lltype);
	int lowpan_register_netdev(struct net_device *dev,
	enum lowpan_lltypes lltype);
	void lowpan_unregister_netdevice(struct net_device *dev);
	void lowpan_unregister_netdev(struct net_device *dev);

	/**
	* lowpan_header_decompress - replace 6LoWPAN header with IPv6 header
	*
	* This function replaces the IPHC 6LoWPAN header which should be pointed at
	* skb->data and skb_network_header, with the IPv6 header.
	* It would be nice that the caller have the necessary headroom of IPv6 header
	* and greatest Transport layer header, this would reduce the overhead for
	* reallocate headroom.
	*
	* @skb: the buffer which should be manipulate.
	* @dev: the lowpan net device pointer.
	* @daddr: destination lladdr of mac header which is used for compression
	* methods.
	* @saddr: source lladdr of mac header which is used for compression
	* methods.
	*/
	int lowpan_header_decompress(struct sk_buff skb, const struct net_device dev,
	const void daddr, const void saddr);

	/**
	* lowpan_header_compress - replace IPv6 header with 6LoWPAN header
	*
	* This function replaces the IPv6 header which should be pointed at
	* skb->data and skb_network_header, with the IPHC 6LoWPAN header.
	* The caller need to be sure that the sk buffer is not shared and at have
	* at least a headroom which is smaller or equal LOWPAN_IPHC_MAX_HEADER_LEN,
	* which is the IPHC "more bytes than IPv6 header" at worst case.
	*
	* @skb: the buffer which should be manipulate.
	* @dev: the lowpan net device pointer.
	* @daddr: destination lladdr of mac header which is used for compression
	* methods.
	* @saddr: source lladdr of mac header which is used for compression
	* methods.
	*/
	int lowpan_header_compress(struct sk_buff skb, const struct net_device dev,
	const void daddr, const void saddr);

	#endif /* __6LOWPAN_H__ */