/*
   * 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.
   *

   */
  
  /* 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.
   */
  
  #include <linux/bitops.h>
  #include <linux/if_arp.h>
  #include <linux/netdevice.h>

  #include <net/6lowpan.h>

  #include <net/ipv6.h>

  #include "6lowpan_i.h"

  #include "nhc.h"

  /* Values of fields within the IPHC encoding first byte */
  #define LOWPAN_IPHC_TF_MASK	0x18
  #define LOWPAN_IPHC_TF_00	0x00
  #define LOWPAN_IPHC_TF_01	0x08
  #define LOWPAN_IPHC_TF_10	0x10
  #define LOWPAN_IPHC_TF_11	0x18
  
  #define LOWPAN_IPHC_NH		0x04

  #define LOWPAN_IPHC_HLIM_MASK	0x03
  #define LOWPAN_IPHC_HLIM_00	0x00
  #define LOWPAN_IPHC_HLIM_01	0x01
  #define LOWPAN_IPHC_HLIM_10	0x02
  #define LOWPAN_IPHC_HLIM_11	0x03

  
  /* Values of fields within the IPHC encoding second byte */
  #define LOWPAN_IPHC_CID		0x80

  #define LOWPAN_IPHC_SAC		0x40

  #define LOWPAN_IPHC_SAM_MASK	0x30
  #define LOWPAN_IPHC_SAM_00	0x00
  #define LOWPAN_IPHC_SAM_01	0x10
  #define LOWPAN_IPHC_SAM_10	0x20
  #define LOWPAN_IPHC_SAM_11	0x30

  
  #define LOWPAN_IPHC_M		0x08

  #define LOWPAN_IPHC_DAC		0x04

  
  #define LOWPAN_IPHC_DAM_MASK	0x03

  #define LOWPAN_IPHC_DAM_00	0x00
  #define LOWPAN_IPHC_DAM_01	0x01
  #define LOWPAN_IPHC_DAM_10	0x02
  #define LOWPAN_IPHC_DAM_11	0x03

  /* ipv6 address based on mac
   * second bit-flip (Universe/Local) is done according RFC2464
   */
  #define is_addr_mac_addr_based(a, m) \
  	((((a)->s6_addr[8])  == (((m)[0]) ^ 0x02)) &&	\
  	 (((a)->s6_addr[9])  == (m)[1]) &&		\
  	 (((a)->s6_addr[10]) == (m)[2]) &&		\
  	 (((a)->s6_addr[11]) == (m)[3]) &&		\
  	 (((a)->s6_addr[12]) == (m)[4]) &&		\
  	 (((a)->s6_addr[13]) == (m)[5]) &&		\
  	 (((a)->s6_addr[14]) == (m)[6]) &&		\
  	 (((a)->s6_addr[15]) == (m)[7]))
  
  /* check whether we can compress the IID to 16 bits,
   * it's possible for unicast addresses with first 49 bits are zero only.
   */
  #define lowpan_is_iid_16_bit_compressable(a)	\
  	((((a)->s6_addr16[4]) == 0) &&		\
  	 (((a)->s6_addr[10]) == 0) &&		\
  	 (((a)->s6_addr[11]) == 0xff) &&	\
  	 (((a)->s6_addr[12]) == 0xfe) &&	\
  	 (((a)->s6_addr[13]) == 0))
  
  /* check whether the 112-bit gid of the multicast address is mappable to: */
  
  /* 48 bits, FFXX::00XX:XXXX:XXXX */
  #define lowpan_is_mcast_addr_compressable48(a)	\
  	((((a)->s6_addr16[1]) == 0) &&		\
  	 (((a)->s6_addr16[2]) == 0) &&		\
  	 (((a)->s6_addr16[3]) == 0) &&		\
  	 (((a)->s6_addr16[4]) == 0) &&		\
  	 (((a)->s6_addr[10]) == 0))
  
  /* 32 bits, FFXX::00XX:XXXX */
  #define lowpan_is_mcast_addr_compressable32(a)	\
  	((((a)->s6_addr16[1]) == 0) &&		\
  	 (((a)->s6_addr16[2]) == 0) &&		\
  	 (((a)->s6_addr16[3]) == 0) &&		\
  	 (((a)->s6_addr16[4]) == 0) &&		\
  	 (((a)->s6_addr16[5]) == 0) &&		\
  	 (((a)->s6_addr[12]) == 0))
  
  /* 8 bits, FF02::00XX */
  #define lowpan_is_mcast_addr_compressable8(a)	\
  	((((a)->s6_addr[1])  == 2) &&		\
  	 (((a)->s6_addr16[1]) == 0) &&		\
  	 (((a)->s6_addr16[2]) == 0) &&		\
  	 (((a)->s6_addr16[3]) == 0) &&		\
  	 (((a)->s6_addr16[4]) == 0) &&		\
  	 (((a)->s6_addr16[5]) == 0) &&		\
  	 (((a)->s6_addr16[6]) == 0) &&		\
  	 (((a)->s6_addr[14]) == 0))

  #define lowpan_is_linklocal_zero_padded(a)	\
  	(!(hdr->saddr.s6_addr[1] & 0x3f) &&	\
  	 !hdr->saddr.s6_addr16[1] &&		\
  	 !hdr->saddr.s6_addr32[1])

  #define LOWPAN_IPHC_CID_DCI(cid)	(cid & 0x0f)
  #define LOWPAN_IPHC_CID_SCI(cid)	((cid & 0xf0) >> 4)

  static inline void
  lowpan_iphc_uncompress_802154_lladdr(struct in6_addr *ipaddr,
  				     const void *lladdr)

  {
  	const struct ieee802154_addr *addr = lladdr;

  	u8 eui64[EUI64_ADDR_LEN];

  
  	switch (addr->mode) {
  	case IEEE802154_ADDR_LONG:
  		ieee802154_le64_to_be64(eui64, &addr->extended_addr);

  		lowpan_iphc_uncompress_eui64_lladdr(ipaddr, eui64);

  		break;
  	case IEEE802154_ADDR_SHORT:
  		/* fe:80::ff:fe00:XXXX
  		 *                \__/
  		 *             short_addr
  		 *
  		 * Universe/Local bit is zero.
  		 */
  		ipaddr->s6_addr[0] = 0xFE;
  		ipaddr->s6_addr[1] = 0x80;
  		ipaddr->s6_addr[11] = 0xFF;
  		ipaddr->s6_addr[12] = 0xFE;
  		ieee802154_le16_to_be16(&ipaddr->s6_addr16[7],
  					&addr->short_addr);
  		break;
  	default:
  		/* should never handled and filtered by 802154 6lowpan */
  		WARN_ON_ONCE(1);
  		break;
  	}
  }

  static struct lowpan_iphc_ctx *
  lowpan_iphc_ctx_get_by_id(const struct net_device *dev, u8 id)
  {

  	struct lowpan_iphc_ctx *ret = &lowpan_dev(dev)->ctx.table[id];

  
  	if (!lowpan_iphc_ctx_is_active(ret))
  		return NULL;
  
  	return ret;
  }
  
  static struct lowpan_iphc_ctx *
  lowpan_iphc_ctx_get_by_addr(const struct net_device *dev,
  			    const struct in6_addr *addr)
  {

  	struct lowpan_iphc_ctx *table = lowpan_dev(dev)->ctx.table;

  	struct lowpan_iphc_ctx *ret = NULL;
  	struct in6_addr addr_pfx;
  	u8 addr_plen;
  	int i;
  
  	for (i = 0; i < LOWPAN_IPHC_CTX_TABLE_SIZE; i++) {
  		/* Check if context is valid. A context that is not valid
  		 * MUST NOT be used for compression.
  		 */
  		if (!lowpan_iphc_ctx_is_active(&table[i]) ||
  		    !lowpan_iphc_ctx_is_compression(&table[i]))
  			continue;
  
  		ipv6_addr_prefix(&addr_pfx, addr, table[i].plen);
  
  		/* if prefix len < 64, the remaining bits until 64th bit is
  		 * zero. Otherwise we use table[i]->plen.
  		 */
  		if (table[i].plen < 64)
  			addr_plen = 64;
  		else
  			addr_plen = table[i].plen;
  
  		if (ipv6_prefix_equal(&addr_pfx, &table[i].pfx, addr_plen)) {
  			/* remember first match */
  			if (!ret) {
  				ret = &table[i];
  				continue;
  			}
  
  			/* get the context with longest prefix len */
  			if (table[i].plen > ret->plen)
  				ret = &table[i];
  		}
  	}
  
  	return ret;
  }
  
  static struct lowpan_iphc_ctx *
  lowpan_iphc_ctx_get_by_mcast_addr(const struct net_device *dev,
  				  const struct in6_addr *addr)
  {

  	struct lowpan_iphc_ctx *table = lowpan_dev(dev)->ctx.table;

  	struct lowpan_iphc_ctx *ret = NULL;
  	struct in6_addr addr_mcast, network_pfx = {};
  	int i;
  
  	/* init mcast address with  */
  	memcpy(&addr_mcast, addr, sizeof(*addr));
  
  	for (i = 0; i < LOWPAN_IPHC_CTX_TABLE_SIZE; i++) {
  		/* Check if context is valid. A context that is not valid
  		 * MUST NOT be used for compression.
  		 */
  		if (!lowpan_iphc_ctx_is_active(&table[i]) ||
  		    !lowpan_iphc_ctx_is_compression(&table[i]))
  			continue;
  
  		/* setting plen */
  		addr_mcast.s6_addr[3] = table[i].plen;
  		/* get network prefix to copy into multicast address */
  		ipv6_addr_prefix(&network_pfx, &table[i].pfx,
  				 table[i].plen);
  		/* setting network prefix */
  		memcpy(&addr_mcast.s6_addr[4], &network_pfx, 8);
  
  		if (ipv6_addr_equal(addr, &addr_mcast)) {
  			ret = &table[i];
  			break;
  		}
  	}
  
  	return ret;
  }

  static void lowpan_iphc_uncompress_lladdr(const struct net_device *dev,
  					  struct in6_addr *ipaddr,
  					  const void *lladdr)
  {
  	switch (dev->addr_len) {
  	case ETH_ALEN:
  		lowpan_iphc_uncompress_eui48_lladdr(ipaddr, lladdr);
  		break;
  	case EUI64_ADDR_LEN:
  		lowpan_iphc_uncompress_eui64_lladdr(ipaddr, lladdr);
  		break;
  	default:
  		WARN_ON_ONCE(1);
  		break;
  	}
  }

  /* Uncompress address function for source and

   * destination address(non-multicast).
   *

   * address_mode is the masked value for sam or dam value

   */

  static int lowpan_iphc_uncompress_addr(struct sk_buff *skb,
  				       const struct net_device *dev,
  				       struct in6_addr *ipaddr,
  				       u8 address_mode, const void *lladdr)

  {
  	bool fail;
  
  	switch (address_mode) {

  	/* SAM and DAM are the same here */
  	case LOWPAN_IPHC_DAM_00:

  		/* for global link addresses */
  		fail = lowpan_fetch_skb(skb, ipaddr->s6_addr, 16);
  		break;

  	case LOWPAN_IPHC_SAM_01:
  	case LOWPAN_IPHC_DAM_01:

  		/* fe:80::XXXX:XXXX:XXXX:XXXX */
  		ipaddr->s6_addr[0] = 0xFE;
  		ipaddr->s6_addr[1] = 0x80;
  		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[8], 8);
  		break;

  	case LOWPAN_IPHC_SAM_10:
  	case LOWPAN_IPHC_DAM_10:

  		/* fe:80::ff:fe00:XXXX */
  		ipaddr->s6_addr[0] = 0xFE;
  		ipaddr->s6_addr[1] = 0x80;
  		ipaddr->s6_addr[11] = 0xFF;
  		ipaddr->s6_addr[12] = 0xFE;
  		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[14], 2);
  		break;

  	case LOWPAN_IPHC_SAM_11:
  	case LOWPAN_IPHC_DAM_11:

  		fail = false;

  		switch (lowpan_dev(dev)->lltype) {

  		case LOWPAN_LLTYPE_IEEE802154:

  			lowpan_iphc_uncompress_802154_lladdr(ipaddr, lladdr);

  			break;
  		default:

  			lowpan_iphc_uncompress_lladdr(dev, ipaddr, lladdr);

  			break;

  		}
  		break;
  	default:
  		pr_debug("Invalid address mode value: 0x%x
  ", address_mode);
  		return -EINVAL;
  	}
  
  	if (fail) {
  		pr_debug("Failed to fetch skb data
  ");
  		return -EIO;
  	}
  
  	raw_dump_inline(NULL, "Reconstructed ipv6 addr is",
  			ipaddr->s6_addr, 16);
  
  	return 0;
  }

  /* Uncompress address function for source context

   * based address(non-multicast).
   */

  static int lowpan_iphc_uncompress_ctx_addr(struct sk_buff *skb,
  					   const struct net_device *dev,
  					   const struct lowpan_iphc_ctx *ctx,
  					   struct in6_addr *ipaddr,
  					   u8 address_mode, const void *lladdr)

  {

  	bool fail;

  	switch (address_mode) {

  	/* SAM and DAM are the same here */
  	case LOWPAN_IPHC_DAM_00:
  		fail = false;
  		/* SAM_00 -> unspec address ::

  		 * Do nothing, address is already ::

  		 *
  		 * DAM 00 -> reserved should never occur.

  		 */
  		break;

  	case LOWPAN_IPHC_SAM_01:

  	case LOWPAN_IPHC_DAM_01:
  		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[8], 8);
  		ipv6_addr_prefix_copy(ipaddr, &ctx->pfx, ctx->plen);
  		break;

  	case LOWPAN_IPHC_SAM_10:

  	case LOWPAN_IPHC_DAM_10:
  		ipaddr->s6_addr[11] = 0xFF;
  		ipaddr->s6_addr[12] = 0xFE;
  		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[14], 2);
  		ipv6_addr_prefix_copy(ipaddr, &ctx->pfx, ctx->plen);
  		break;

  	case LOWPAN_IPHC_SAM_11:

  	case LOWPAN_IPHC_DAM_11:
  		fail = false;

  		switch (lowpan_dev(dev)->lltype) {

  		case LOWPAN_LLTYPE_IEEE802154:

  			lowpan_iphc_uncompress_802154_lladdr(ipaddr, lladdr);

  			break;
  		default:

  			lowpan_iphc_uncompress_lladdr(dev, ipaddr, lladdr);

  			break;
  		}
  		ipv6_addr_prefix_copy(ipaddr, &ctx->pfx, ctx->plen);
  		break;

  	default:

  		pr_debug("Invalid sam value: 0x%x
  ", address_mode);

  		return -EINVAL;
  	}

  	if (fail) {
  		pr_debug("Failed to fetch skb data
  ");
  		return -EIO;
  	}

  	raw_dump_inline(NULL,
  			"Reconstructed context based ipv6 src addr is",
  			ipaddr->s6_addr, 16);
  
  	return 0;
  }

  /* Uncompress function for multicast destination address,
   * when M bit is set.
   */

  static int lowpan_uncompress_multicast_daddr(struct sk_buff *skb,
  					     struct in6_addr *ipaddr,

  					     u8 address_mode)

  {
  	bool fail;

  	switch (address_mode) {

  	case LOWPAN_IPHC_DAM_00:
  		/* 00:  128 bits.  The full address
  		 * is carried in-line.
  		 */
  		fail = lowpan_fetch_skb(skb, ipaddr->s6_addr, 16);
  		break;
  	case LOWPAN_IPHC_DAM_01:
  		/* 01:  48 bits.  The address takes
  		 * the form ffXX::00XX:XXXX:XXXX.
  		 */
  		ipaddr->s6_addr[0] = 0xFF;
  		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 1);
  		fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[11], 5);
  		break;
  	case LOWPAN_IPHC_DAM_10:
  		/* 10:  32 bits.  The address takes
  		 * the form ffXX::00XX:XXXX.
  		 */
  		ipaddr->s6_addr[0] = 0xFF;
  		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 1);
  		fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[13], 3);
  		break;
  	case LOWPAN_IPHC_DAM_11:
  		/* 11:  8 bits.  The address takes
  		 * the form ff02::00XX.
  		 */
  		ipaddr->s6_addr[0] = 0xFF;
  		ipaddr->s6_addr[1] = 0x02;
  		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[15], 1);
  		break;
  	default:

  		pr_debug("DAM value has a wrong value: 0x%x
  ", address_mode);

  		return -EINVAL;
  	}
  
  	if (fail) {
  		pr_debug("Failed to fetch skb data
  ");
  		return -EIO;
  	}
  
  	raw_dump_inline(NULL, "Reconstructed ipv6 multicast addr is",

  			ipaddr->s6_addr, 16);

  
  	return 0;
  }

  static int lowpan_uncompress_multicast_ctx_daddr(struct sk_buff *skb,
  						 struct lowpan_iphc_ctx *ctx,
  						 struct in6_addr *ipaddr,
  						 u8 address_mode)
  {
  	struct in6_addr network_pfx = {};
  	bool fail;
  
  	ipaddr->s6_addr[0] = 0xFF;
  	fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 2);
  	fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[12], 4);

  	if (fail)

  		return -EIO;
  
  	/* take prefix_len and network prefix from the context */
  	ipaddr->s6_addr[3] = ctx->plen;
  	/* get network prefix to copy into multicast address */
  	ipv6_addr_prefix(&network_pfx, &ctx->pfx, ctx->plen);
  	/* setting network prefix */
  	memcpy(&ipaddr->s6_addr[4], &network_pfx, 8);
  
  	return 0;
  }

  /* get the ecn values from iphc tf format and set it to ipv6hdr */
  static inline void lowpan_iphc_tf_set_ecn(struct ipv6hdr *hdr, const u8 *tf)
  {
  	/* get the two higher bits which is ecn */
  	u8 ecn = tf[0] & 0xc0;
  
  	/* ECN takes 0x30 in hdr->flow_lbl[0] */
  	hdr->flow_lbl[0] |= (ecn >> 2);
  }
  
  /* get the dscp values from iphc tf format and set it to ipv6hdr */
  static inline void lowpan_iphc_tf_set_dscp(struct ipv6hdr *hdr, const u8 *tf)
  {
  	/* DSCP is at place after ECN */
  	u8 dscp = tf[0] & 0x3f;
  
  	/* The four highest bits need to be set at hdr->priority */
  	hdr->priority |= ((dscp & 0x3c) >> 2);
  	/* The two lower bits is part of hdr->flow_lbl[0] */
  	hdr->flow_lbl[0] |= ((dscp & 0x03) << 6);
  }
  
  /* get the flow label values from iphc tf format and set it to ipv6hdr */
  static inline void lowpan_iphc_tf_set_lbl(struct ipv6hdr *hdr, const u8 *lbl)
  {
  	/* flow label is always some array started with lower nibble of
  	 * flow_lbl[0] and followed with two bytes afterwards. Inside inline
  	 * data the flow_lbl position can be different, which will be handled
  	 * by lbl pointer. E.g. case "01" vs "00" the traffic class is 8 bit
  	 * shifted, the different lbl pointer will handle that.
  	 *
  	 * The flow label will started at lower nibble of flow_lbl[0], the
  	 * higher nibbles are part of DSCP + ECN.
  	 */
  	hdr->flow_lbl[0] |= lbl[0] & 0x0f;
  	memcpy(&hdr->flow_lbl[1], &lbl[1], 2);
  }
  
  /* lowpan_iphc_tf_decompress - decompress the traffic class.
   *	This function will return zero on success, a value lower than zero if
   *	failed.
   */
  static int lowpan_iphc_tf_decompress(struct sk_buff *skb, struct ipv6hdr *hdr,
  				     u8 val)
  {
  	u8 tf[4];
  
  	/* Traffic Class and Flow Label */
  	switch (val) {
  	case LOWPAN_IPHC_TF_00:
  		/* ECN + DSCP + 4-bit Pad + Flow Label (4 bytes) */
  		if (lowpan_fetch_skb(skb, tf, 4))
  			return -EINVAL;
  
  		/*                      1                   2                   3
  		 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  		 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  		 * |ECN|   DSCP    |  rsv  |             Flow Label                |
  		 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  		 */
  		lowpan_iphc_tf_set_ecn(hdr, tf);
  		lowpan_iphc_tf_set_dscp(hdr, tf);
  		lowpan_iphc_tf_set_lbl(hdr, &tf[1]);
  		break;
  	case LOWPAN_IPHC_TF_01:
  		/* ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided. */
  		if (lowpan_fetch_skb(skb, tf, 3))
  			return -EINVAL;
  
  		/*                     1                   2
  		 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
  		 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  		 * |ECN|rsv|             Flow Label                |
  		 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  		 */
  		lowpan_iphc_tf_set_ecn(hdr, tf);
  		lowpan_iphc_tf_set_lbl(hdr, &tf[0]);
  		break;
  	case LOWPAN_IPHC_TF_10:
  		/* ECN + DSCP (1 byte), Flow Label is elided. */
  		if (lowpan_fetch_skb(skb, tf, 1))
  			return -EINVAL;
  
  		/*  0 1 2 3 4 5 6 7
  		 * +-+-+-+-+-+-+-+-+
  		 * |ECN|   DSCP    |
  		 * +-+-+-+-+-+-+-+-+
  		 */
  		lowpan_iphc_tf_set_ecn(hdr, tf);
  		lowpan_iphc_tf_set_dscp(hdr, tf);
  		break;
  	case LOWPAN_IPHC_TF_11:
  		/* Traffic Class and Flow Label are elided */
  		break;
  	default:
  		WARN_ON_ONCE(1);
  		return -EINVAL;
  	}
  
  	return 0;
  }

  /* TTL uncompression values */

  static const u8 lowpan_ttl_values[] = {
  	[LOWPAN_IPHC_HLIM_01] = 1,
  	[LOWPAN_IPHC_HLIM_10] = 64,
  	[LOWPAN_IPHC_HLIM_11] = 255,
  };

  int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
  			     const void *daddr, const void *saddr)

  {
  	struct ipv6hdr hdr = {};

  	struct lowpan_iphc_ctx *ci;
  	u8 iphc0, iphc1, cid = 0;

  	int err;
  
  	raw_dump_table(__func__, "raw skb data dump uncompressed",

  		       skb->data, skb->len);

  	if (lowpan_fetch_skb(skb, &iphc0, sizeof(iphc0)) ||
  	    lowpan_fetch_skb(skb, &iphc1, sizeof(iphc1)))

  		return -EINVAL;

  	hdr.version = 6;

  	/* default CID = 0, another if the CID flag is set */
  	if (iphc1 & LOWPAN_IPHC_CID) {
  		if (lowpan_fetch_skb(skb, &cid, sizeof(cid)))
  			return -EINVAL;
  	}

  	err = lowpan_iphc_tf_decompress(skb, &hdr,
  					iphc0 & LOWPAN_IPHC_TF_MASK);
  	if (err < 0)
  		return err;

  
  	/* Next Header */

  	if (!(iphc0 & LOWPAN_IPHC_NH)) {

  		/* Next header is carried inline */

  		if (lowpan_fetch_skb(skb, &hdr.nexthdr, sizeof(hdr.nexthdr)))

  			return -EINVAL;

  
  		pr_debug("NH flag is set, next header carried inline: %02x
  ",
  			 hdr.nexthdr);
  	}
  
  	/* Hop Limit */

  	if ((iphc0 & LOWPAN_IPHC_HLIM_MASK) != LOWPAN_IPHC_HLIM_00) {
  		hdr.hop_limit = lowpan_ttl_values[iphc0 & LOWPAN_IPHC_HLIM_MASK];

  	} else {

  		if (lowpan_fetch_skb(skb, &hdr.hop_limit,
  				     sizeof(hdr.hop_limit)))

  			return -EINVAL;

  	}

  	if (iphc1 & LOWPAN_IPHC_SAC) {

  		spin_lock_bh(&lowpan_dev(dev)->ctx.lock);

  		ci = lowpan_iphc_ctx_get_by_id(dev, LOWPAN_IPHC_CID_SCI(cid));
  		if (!ci) {

  			spin_unlock_bh(&lowpan_dev(dev)->ctx.lock);

  			return -EINVAL;
  		}

  		pr_debug("SAC bit is set. Handle context based source address.
  ");

  		err = lowpan_iphc_uncompress_ctx_addr(skb, dev, ci, &hdr.saddr,
  						      iphc1 & LOWPAN_IPHC_SAM_MASK,
  						      saddr);

  		spin_unlock_bh(&lowpan_dev(dev)->ctx.lock);

  	} else {
  		/* Source address uncompression */
  		pr_debug("source address stateless compression
  ");

  		err = lowpan_iphc_uncompress_addr(skb, dev, &hdr.saddr,
  						  iphc1 & LOWPAN_IPHC_SAM_MASK,
  						  saddr);

  	}
  
  	/* Check on error of previous branch */
  	if (err)

  		return -EINVAL;

  	switch (iphc1 & (LOWPAN_IPHC_M | LOWPAN_IPHC_DAC)) {
  	case LOWPAN_IPHC_M | LOWPAN_IPHC_DAC:

  		skb->pkt_type = PACKET_BROADCAST;

  		spin_lock_bh(&lowpan_dev(dev)->ctx.lock);

  		ci = lowpan_iphc_ctx_get_by_id(dev, LOWPAN_IPHC_CID_DCI(cid));
  		if (!ci) {

  			spin_unlock_bh(&lowpan_dev(dev)->ctx.lock);

  			return -EINVAL;
  		}

  		/* multicast with context */
  		pr_debug("dest: context-based mcast compression
  ");
  		err = lowpan_uncompress_multicast_ctx_daddr(skb, ci,
  							    &hdr.daddr,
  							    iphc1 & LOWPAN_IPHC_DAM_MASK);

  		spin_unlock_bh(&lowpan_dev(dev)->ctx.lock);

  		break;
  	case LOWPAN_IPHC_M:

  		skb->pkt_type = PACKET_BROADCAST;

  		/* multicast */
  		err = lowpan_uncompress_multicast_daddr(skb, &hdr.daddr,
  							iphc1 & LOWPAN_IPHC_DAM_MASK);
  		break;
  	case LOWPAN_IPHC_DAC:

  		skb->pkt_type = PACKET_HOST;

  		spin_lock_bh(&lowpan_dev(dev)->ctx.lock);

  		ci = lowpan_iphc_ctx_get_by_id(dev, LOWPAN_IPHC_CID_DCI(cid));
  		if (!ci) {

  			spin_unlock_bh(&lowpan_dev(dev)->ctx.lock);

  			return -EINVAL;

  		}

  
  		/* Destination address context based uncompression */
  		pr_debug("DAC bit is set. Handle context based destination address.
  ");

  		err = lowpan_iphc_uncompress_ctx_addr(skb, dev, ci, &hdr.daddr,
  						      iphc1 & LOWPAN_IPHC_DAM_MASK,
  						      daddr);

  		spin_unlock_bh(&lowpan_dev(dev)->ctx.lock);

  		break;
  	default:

  		skb->pkt_type = PACKET_HOST;

  		err = lowpan_iphc_uncompress_addr(skb, dev, &hdr.daddr,
  						  iphc1 & LOWPAN_IPHC_DAM_MASK,
  						  daddr);

  		pr_debug("dest: stateless compression mode %d dest %pI6c
  ",

  			 iphc1 & LOWPAN_IPHC_DAM_MASK, &hdr.daddr);

  		break;

  	}

  	if (err)
  		return -EINVAL;

  	/* Next header data uncompression */

  	if (iphc0 & LOWPAN_IPHC_NH) {

  		err = lowpan_nhc_do_uncompression(skb, dev, &hdr);
  		if (err < 0)

  			return err;

  	} else {
  		err = skb_cow(skb, sizeof(hdr));

  		if (unlikely(err))

  			return err;

  	}

  	switch (lowpan_dev(dev)->lltype) {

  	case LOWPAN_LLTYPE_IEEE802154:
  		if (lowpan_802154_cb(skb)->d_size)
  			hdr.payload_len = htons(lowpan_802154_cb(skb)->d_size -
  						sizeof(struct ipv6hdr));
  		else
  			hdr.payload_len = htons(skb->len);
  		break;
  	default:
  		hdr.payload_len = htons(skb->len);
  		break;
  	}

  
  	pr_debug("skb headroom size = %d, data length = %d
  ",
  		 skb_headroom(skb), skb->len);
  
  	pr_debug("IPv6 header dump:
  \tversion = %d
  \tlength  = %d
  \t"
  		 "nexthdr = 0x%02x
  \thop_lim = %d
  \tdest    = %pI6c
  ",
  		hdr.version, ntohs(hdr.payload_len), hdr.nexthdr,
  		hdr.hop_limit, &hdr.daddr);

  	skb_push(skb, sizeof(hdr));

  	skb_reset_mac_header(skb);

  	skb_reset_network_header(skb);
  	skb_copy_to_linear_data(skb, &hdr, sizeof(hdr));

  	raw_dump_table(__func__, "raw header dump", (u8 *)&hdr, sizeof(hdr));

  	return 0;

  }

  EXPORT_SYMBOL_GPL(lowpan_header_decompress);

  static const u8 lowpan_iphc_dam_to_sam_value[] = {
  	[LOWPAN_IPHC_DAM_00] = LOWPAN_IPHC_SAM_00,
  	[LOWPAN_IPHC_DAM_01] = LOWPAN_IPHC_SAM_01,
  	[LOWPAN_IPHC_DAM_10] = LOWPAN_IPHC_SAM_10,
  	[LOWPAN_IPHC_DAM_11] = LOWPAN_IPHC_SAM_11,
  };

  static inline bool
  lowpan_iphc_compress_ctx_802154_lladdr(const struct in6_addr *ipaddr,
  				       const struct lowpan_iphc_ctx *ctx,
  				       const void *lladdr)
  {
  	const struct ieee802154_addr *addr = lladdr;
  	unsigned char extended_addr[EUI64_ADDR_LEN];
  	bool lladdr_compress = false;
  	struct in6_addr tmp = {};
  
  	switch (addr->mode) {
  	case IEEE802154_ADDR_LONG:
  		ieee802154_le64_to_be64(&extended_addr, &addr->extended_addr);
  		/* check for SAM/DAM = 11 */
  		memcpy(&tmp.s6_addr[8], &extended_addr, EUI64_ADDR_LEN);
  		/* second bit-flip (Universe/Local) is done according RFC2464 */
  		tmp.s6_addr[8] ^= 0x02;
  		/* context information are always used */
  		ipv6_addr_prefix_copy(&tmp, &ctx->pfx, ctx->plen);
  		if (ipv6_addr_equal(&tmp, ipaddr))
  			lladdr_compress = true;
  		break;
  	case IEEE802154_ADDR_SHORT:
  		tmp.s6_addr[11] = 0xFF;
  		tmp.s6_addr[12] = 0xFE;
  		ieee802154_le16_to_be16(&tmp.s6_addr16[7],
  					&addr->short_addr);
  		/* context information are always used */
  		ipv6_addr_prefix_copy(&tmp, &ctx->pfx, ctx->plen);
  		if (ipv6_addr_equal(&tmp, ipaddr))
  			lladdr_compress = true;
  		break;
  	default:
  		/* should never handled and filtered by 802154 6lowpan */
  		WARN_ON_ONCE(1);
  		break;
  	}
  
  	return lladdr_compress;
  }

  static bool lowpan_iphc_addr_equal(const struct net_device *dev,
  				   const struct lowpan_iphc_ctx *ctx,
  				   const struct in6_addr *ipaddr,
  				   const void *lladdr)
  {
  	struct in6_addr tmp = {};
  
  	lowpan_iphc_uncompress_lladdr(dev, &tmp, lladdr);
  
  	if (ctx)
  		ipv6_addr_prefix_copy(&tmp, &ctx->pfx, ctx->plen);
  
  	return ipv6_addr_equal(&tmp, ipaddr);
  }

  static u8 lowpan_compress_ctx_addr(u8 **hc_ptr, const struct net_device *dev,
  				   const struct in6_addr *ipaddr,

  				   const struct lowpan_iphc_ctx *ctx,
  				   const unsigned char *lladdr, bool sam)
  {
  	struct in6_addr tmp = {};
  	u8 dam;

  	switch (lowpan_dev(dev)->lltype) {
  	case LOWPAN_LLTYPE_IEEE802154:
  		if (lowpan_iphc_compress_ctx_802154_lladdr(ipaddr, ctx,
  							   lladdr)) {
  			dam = LOWPAN_IPHC_DAM_11;
  			goto out;
  		}
  		break;
  	default:

  		if (lowpan_iphc_addr_equal(dev, ctx, ipaddr, lladdr)) {

  			dam = LOWPAN_IPHC_DAM_11;
  			goto out;
  		}
  		break;

  	}
  
  	memset(&tmp, 0, sizeof(tmp));

  	/* check for SAM/DAM = 10 */

  	tmp.s6_addr[11] = 0xFF;
  	tmp.s6_addr[12] = 0xFE;
  	memcpy(&tmp.s6_addr[14], &ipaddr->s6_addr[14], 2);
  	/* context information are always used */
  	ipv6_addr_prefix_copy(&tmp, &ctx->pfx, ctx->plen);
  	if (ipv6_addr_equal(&tmp, ipaddr)) {
  		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[14], 2);
  		dam = LOWPAN_IPHC_DAM_10;
  		goto out;
  	}
  
  	memset(&tmp, 0, sizeof(tmp));

  	/* check for SAM/DAM = 01, should always match */

  	memcpy(&tmp.s6_addr[8], &ipaddr->s6_addr[8], 8);
  	/* context information are always used */
  	ipv6_addr_prefix_copy(&tmp, &ctx->pfx, ctx->plen);
  	if (ipv6_addr_equal(&tmp, ipaddr)) {
  		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[8], 8);
  		dam = LOWPAN_IPHC_DAM_01;
  		goto out;
  	}

  	WARN_ONCE(1, "context found but no address mode matched
  ");
  	return LOWPAN_IPHC_DAM_00;

  out:
  
  	if (sam)
  		return lowpan_iphc_dam_to_sam_value[dam];
  	else
  		return dam;
  }

  static inline bool
  lowpan_iphc_compress_802154_lladdr(const struct in6_addr *ipaddr,
  				   const void *lladdr)
  {
  	const struct ieee802154_addr *addr = lladdr;
  	unsigned char extended_addr[EUI64_ADDR_LEN];
  	bool lladdr_compress = false;
  	struct in6_addr tmp = {};
  
  	switch (addr->mode) {
  	case IEEE802154_ADDR_LONG:
  		ieee802154_le64_to_be64(&extended_addr, &addr->extended_addr);
  		if (is_addr_mac_addr_based(ipaddr, extended_addr))
  			lladdr_compress = true;
  		break;
  	case IEEE802154_ADDR_SHORT:
  		/* fe:80::ff:fe00:XXXX
  		 *                \__/
  		 *             short_addr
  		 *
  		 * Universe/Local bit is zero.
  		 */
  		tmp.s6_addr[0] = 0xFE;
  		tmp.s6_addr[1] = 0x80;
  		tmp.s6_addr[11] = 0xFF;
  		tmp.s6_addr[12] = 0xFE;
  		ieee802154_le16_to_be16(&tmp.s6_addr16[7],
  					&addr->short_addr);
  		if (ipv6_addr_equal(&tmp, ipaddr))
  			lladdr_compress = true;
  		break;
  	default:
  		/* should never handled and filtered by 802154 6lowpan */
  		WARN_ON_ONCE(1);
  		break;
  	}
  
  	return lladdr_compress;
  }
  
  static u8 lowpan_compress_addr_64(u8 **hc_ptr, const struct net_device *dev,
  				  const struct in6_addr *ipaddr,

  				  const unsigned char *lladdr, bool sam)

  {

  	u8 dam = LOWPAN_IPHC_DAM_01;

  	switch (lowpan_dev(dev)->lltype) {
  	case LOWPAN_LLTYPE_IEEE802154:
  		if (lowpan_iphc_compress_802154_lladdr(ipaddr, lladdr)) {
  			dam = LOWPAN_IPHC_DAM_11; /* 0-bits */
  			pr_debug("address compression 0 bits
  ");
  			goto out;
  		}
  		break;
  	default:

  		if (lowpan_iphc_addr_equal(dev, NULL, ipaddr, lladdr)) {
  			dam = LOWPAN_IPHC_DAM_11;

  			pr_debug("address compression 0 bits
  ");
  			goto out;
  		}

  		break;
  	}
  
  	if (lowpan_is_iid_16_bit_compressable(ipaddr)) {

  		/* compress IID to 16 bits xxxx::XXXX */

  		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr16[7], 2);

  		dam = LOWPAN_IPHC_DAM_10; /* 16-bits */

  		raw_dump_inline(NULL, "Compressed ipv6 addr is (16 bits)",

  				*hc_ptr - 2, 2);

  		goto out;

  	}

  	/* do not compress IID => xxxx::IID */
  	lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr16[4], 8);
  	raw_dump_inline(NULL, "Compressed ipv6 addr is (64 bits)",
  			*hc_ptr - 8, 8);
  
  out:

  	if (sam)
  		return lowpan_iphc_dam_to_sam_value[dam];
  	else
  		return dam;

  }

  /* lowpan_iphc_get_tc - get the ECN + DCSP fields in hc format */
  static inline u8 lowpan_iphc_get_tc(const struct ipv6hdr *hdr)
  {
  	u8 dscp, ecn;
  
  	/* hdr->priority contains the higher bits of dscp, lower are part of
  	 * flow_lbl[0]. Note ECN, DCSP is swapped in ipv6 hdr.
  	 */
  	dscp = (hdr->priority << 2) | ((hdr->flow_lbl[0] & 0xc0) >> 6);
  	/* ECN is at the two lower bits from first nibble of flow_lbl[0] */
  	ecn = (hdr->flow_lbl[0] & 0x30);
  	/* for pretty debug output, also shift ecn to get the ecn value */
  	pr_debug("ecn 0x%02x dscp 0x%02x
  ", ecn >> 4, dscp);
  	/* ECN is at 0x30 now, shift it to have ECN + DCSP */
  	return (ecn << 2) | dscp;
  }
  
  /* lowpan_iphc_is_flow_lbl_zero - check if flow label is zero */
  static inline bool lowpan_iphc_is_flow_lbl_zero(const struct ipv6hdr *hdr)
  {
  	return ((!(hdr->flow_lbl[0] & 0x0f)) &&
  		!hdr->flow_lbl[1] && !hdr->flow_lbl[2]);
  }
  
  /* lowpan_iphc_tf_compress - compress the traffic class which is set by
   *	ipv6hdr. Return the corresponding format identifier which is used.
   */
  static u8 lowpan_iphc_tf_compress(u8 **hc_ptr, const struct ipv6hdr *hdr)
  {
  	/* get ecn dscp data in a byteformat as: ECN(hi) + DSCP(lo) */
  	u8 tc = lowpan_iphc_get_tc(hdr), tf[4], val;
  
  	/* printout the traffic class in hc format */
  	pr_debug("tc 0x%02x
  ", tc);
  
  	if (lowpan_iphc_is_flow_lbl_zero(hdr)) {
  		if (!tc) {
  			/* 11:  Traffic Class and Flow Label are elided. */
  			val = LOWPAN_IPHC_TF_11;
  		} else {
  			/* 10:  ECN + DSCP (1 byte), Flow Label is elided.
  			 *
  			 *  0 1 2 3 4 5 6 7
  			 * +-+-+-+-+-+-+-+-+
  			 * |ECN|   DSCP    |
  			 * +-+-+-+-+-+-+-+-+
  			 */
  			lowpan_push_hc_data(hc_ptr, &tc, sizeof(tc));
  			val = LOWPAN_IPHC_TF_10;
  		}
  	} else {
  		/* check if dscp is zero, it's after the first two bit */
  		if (!(tc & 0x3f)) {
  			/* 01:  ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
  			 *
  			 *                     1                   2
  			 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
  			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  			 * |ECN|rsv|             Flow Label                |
  			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  			 */
  			memcpy(&tf[0], &hdr->flow_lbl[0], 3);
  			/* zero the highest 4-bits, contains DCSP + ECN */
  			tf[0] &= ~0xf0;
  			/* set ECN */
  			tf[0] |= (tc & 0xc0);
  
  			lowpan_push_hc_data(hc_ptr, tf, 3);
  			val = LOWPAN_IPHC_TF_01;
  		} else {
  			/* 00:  ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
  			 *
  			 *                      1                   2                   3
  			 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  			 * |ECN|   DSCP    |  rsv  |             Flow Label                |
  			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  			 */
  			memcpy(&tf[0], &tc, sizeof(tc));
  			/* highest nibble of flow_lbl[0] is part of DSCP + ECN
  			 * which will be the 4-bit pad and will be filled with
  			 * zeros afterwards.
  			 */
  			memcpy(&tf[1], &hdr->flow_lbl[0], 3);
  			/* zero the 4-bit pad, which is reserved */
  			tf[1] &= ~0xf0;
  
  			lowpan_push_hc_data(hc_ptr, tf, 4);
  			val = LOWPAN_IPHC_TF_00;
  		}
  	}
  
  	return val;
  }

  static u8 lowpan_iphc_mcast_ctx_addr_compress(u8 **hc_ptr,
  					      const struct lowpan_iphc_ctx *ctx,
  					      const struct in6_addr *ipaddr)
  {
  	u8 data[6];
  
  	/* flags/scope, reserved (RIID) */
  	memcpy(data, &ipaddr->s6_addr[1], 2);
  	/* group ID */
  	memcpy(&data[1], &ipaddr->s6_addr[11], 4);
  	lowpan_push_hc_data(hc_ptr, data, 6);
  
  	return LOWPAN_IPHC_DAM_00;
  }

  static u8 lowpan_iphc_mcast_addr_compress(u8 **hc_ptr,
  					  const struct in6_addr *ipaddr)
  {
  	u8 val;
  
  	if (lowpan_is_mcast_addr_compressable8(ipaddr)) {
  		pr_debug("compressed to 1 octet
  ");
  		/* use last byte */
  		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[15], 1);
  		val = LOWPAN_IPHC_DAM_11;
  	} else if (lowpan_is_mcast_addr_compressable32(ipaddr)) {
  		pr_debug("compressed to 4 octets
  ");
  		/* second byte + the last three */
  		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[1], 1);
  		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[13], 3);
  		val = LOWPAN_IPHC_DAM_10;
  	} else if (lowpan_is_mcast_addr_compressable48(ipaddr)) {
  		pr_debug("compressed to 6 octets
  ");
  		/* second byte + the last five */
  		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[1], 1);
  		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[11], 5);
  		val = LOWPAN_IPHC_DAM_01;
  	} else {
  		pr_debug("using full address
  ");
  		lowpan_push_hc_data(hc_ptr, ipaddr->s6_addr, 16);
  		val = LOWPAN_IPHC_DAM_00;
  	}
  
  	return val;
  }

  int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
  			   const void *daddr, const void *saddr)

  {

  	u8 iphc0, iphc1, *hc_ptr, cid = 0;

  	struct ipv6hdr *hdr;

  	u8 head[LOWPAN_IPHC_MAX_HC_BUF_LEN] = {};

  	struct lowpan_iphc_ctx *dci, *sci, dci_entry, sci_entry;
  	int ret, ipv6_daddr_type, ipv6_saddr_type;

  	if (skb->protocol != htons(ETH_P_IPV6))

  		return -EINVAL;
  
  	hdr = ipv6_hdr(skb);

  	hc_ptr = head + 2;

  
  	pr_debug("IPv6 header dump:
  \tversion = %d
  \tlength  = %d
  "
  		 "\tnexthdr = 0x%02x
  \thop_lim = %d
  \tdest    = %pI6c
  ",

  		 hdr->version, ntohs(hdr->payload_len), hdr->nexthdr,
  		 hdr->hop_limit, &hdr->daddr);

  
  	raw_dump_table(__func__, "raw skb network header dump",

  		       skb_network_header(skb), sizeof(struct ipv6hdr));

  	/* As we copy some bit-length fields, in the IPHC encoding bytes,

  	 * we sometimes use |=
  	 * If the field is 0, and the current bit value in memory is 1,
  	 * this does not work. We therefore reset the IPHC encoding here
  	 */
  	iphc0 = LOWPAN_DISPATCH_IPHC;
  	iphc1 = 0;

  	raw_dump_table(__func__, "sending raw skb network uncompressed packet",

  		       skb->data, skb->len);

  	ipv6_daddr_type = ipv6_addr_type(&hdr->daddr);

  	spin_lock_bh(&lowpan_dev(dev)->ctx.lock);

  	if (ipv6_daddr_type & IPV6_ADDR_MULTICAST)
  		dci = lowpan_iphc_ctx_get_by_mcast_addr(dev, &hdr->daddr);
  	else
  		dci = lowpan_iphc_ctx_get_by_addr(dev, &hdr->daddr);
  	if (dci) {
  		memcpy(&dci_entry, dci, sizeof(*dci));
  		cid |= dci->id;
  	}

  	spin_unlock_bh(&lowpan_dev(dev)->ctx.lock);

  	spin_lock_bh(&lowpan_dev(dev)->ctx.lock);

  	sci = lowpan_iphc_ctx_get_by_addr(dev, &hdr->saddr);
  	if (sci) {
  		memcpy(&sci_entry, sci, sizeof(*sci));
  		cid |= (sci->id << 4);
  	}

  	spin_unlock_bh(&lowpan_dev(dev)->ctx.lock);

  
  	/* if cid is zero it will be compressed */
  	if (cid) {
  		iphc1 |= LOWPAN_IPHC_CID;
  		lowpan_push_hc_data(&hc_ptr, &cid, sizeof(cid));
  	}

  	/* Traffic Class, Flow Label compression */
  	iphc0 |= lowpan_iphc_tf_compress(&hc_ptr, hdr);

  
  	/* NOTE: payload length is always compressed */

  	/* Check if we provide the nhc format for nexthdr and compression
  	 * functionality. If not nexthdr is handled inline and not compressed.
  	 */

  	ret = lowpan_nhc_check_compression(skb, hdr, &hc_ptr);
  	if (ret == -ENOENT)
  		lowpan_push_hc_data(&hc_ptr, &hdr->nexthdr,
  				    sizeof(hdr->nexthdr));
  	else

  		iphc0 |= LOWPAN_IPHC_NH;

  	/* Hop limit

  	 * if 1:   compress, encoding is 01
  	 * if 64:  compress, encoding is 10
  	 * if 255: compress, encoding is 11
  	 * else do not compress
  	 */
  	switch (hdr->hop_limit) {
  	case 1:

  		iphc0 |= LOWPAN_IPHC_HLIM_01;

  		break;
  	case 64:

  		iphc0 |= LOWPAN_IPHC_HLIM_10;

  		break;
  	case 255:

  		iphc0 |= LOWPAN_IPHC_HLIM_11;

  		break;
  	default:

  		lowpan_push_hc_data(&hc_ptr, &hdr->hop_limit,
  				    sizeof(hdr->hop_limit));

  	}

  	ipv6_saddr_type = ipv6_addr_type(&hdr->saddr);

  	/* source address compression */

  	if (ipv6_saddr_type == IPV6_ADDR_ANY) {

  		pr_debug("source address is unspecified, setting SAC
  ");
  		iphc1 |= LOWPAN_IPHC_SAC;

  	} else {

  		if (sci) {

  			iphc1 |= lowpan_compress_ctx_addr(&hc_ptr, dev,
  							  &hdr->saddr,

  							  &sci_entry, saddr,
  							  true);
  			iphc1 |= LOWPAN_IPHC_SAC;

  		} else {

  			if (ipv6_saddr_type & IPV6_ADDR_LINKLOCAL &&
  			    lowpan_is_linklocal_zero_padded(hdr->saddr)) {

  				iphc1 |= lowpan_compress_addr_64(&hc_ptr, dev,

  								 &hdr->saddr,
  								 saddr, true);
  				pr_debug("source address unicast link-local %pI6c iphc1 0x%02x
  ",
  					 &hdr->saddr, iphc1);
  			} else {
  				pr_debug("send the full source address
  ");
  				lowpan_push_hc_data(&hc_ptr,
  						    hdr->saddr.s6_addr, 16);
  			}

  		}

  	}
  
  	/* destination address compression */

  	if (ipv6_daddr_type & IPV6_ADDR_MULTICAST) {

  		pr_debug("destination address is multicast: ");

  		iphc1 |= LOWPAN_IPHC_M;

  		if (dci) {
  			iphc1 |= lowpan_iphc_mcast_ctx_addr_compress(&hc_ptr,
  								     &dci_entry,
  								     &hdr->daddr);

  			iphc1 |= LOWPAN_IPHC_DAC;

  		} else {

  			iphc1 |= lowpan_iphc_mcast_addr_compress(&hc_ptr,
  								 &hdr->daddr);
  		}

  	} else {

  		if (dci) {

  			iphc1 |= lowpan_compress_ctx_addr(&hc_ptr, dev,
  							  &hdr->daddr,

  							  &dci_entry, daddr,
  							  false);
  			iphc1 |= LOWPAN_IPHC_DAC;

  		} else {

  			if (ipv6_daddr_type & IPV6_ADDR_LINKLOCAL &&
  			    lowpan_is_linklocal_zero_padded(hdr->daddr)) {

  				iphc1 |= lowpan_compress_addr_64(&hc_ptr, dev,

  								 &hdr->daddr,
  								 daddr, false);
  				pr_debug("dest address unicast link-local %pI6c iphc1 0x%02x
  ",
  					 &hdr->daddr, iphc1);
  			} else {
  				pr_debug("dest address unicast %pI6c
  ",
  					 &hdr->daddr);
  				lowpan_push_hc_data(&hc_ptr,
  						    hdr->daddr.s6_addr, 16);
  			}

  		}
  	}

  	/* next header compression */

  	if (iphc0 & LOWPAN_IPHC_NH) {

  		ret = lowpan_nhc_do_compression(skb, hdr, &hc_ptr);
  		if (ret < 0)
  			return ret;
  	}

  
  	head[0] = iphc0;
  	head[1] = iphc1;
  
  	skb_pull(skb, sizeof(struct ipv6hdr));
  	skb_reset_transport_header(skb);

  	memcpy(skb_push(skb, hc_ptr - head), head, hc_ptr - head);

  	skb_reset_network_header(skb);

  	pr_debug("header len %d skb %u
  ", (int)(hc_ptr - head), skb->len);

  
  	raw_dump_table(__func__, "raw skb data dump compressed",

  		       skb->data, skb->len);

  	return 0;
  }
  EXPORT_SYMBOL_GPL(lowpan_header_compress);