src/core/net/ip6_mpl.hpp - third_party/openthread - Git at Google

 /*
  *  Copyright (c) 2016, The OpenThread Authors.
  *  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 copyright holder 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 COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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 IP6_MPL_HPP_
 #define IP6_MPL_HPP_

 /**
  * @file
  *   This file includes definitions for MPL.
  */

 #include "openthread-core-config.h"

 #include "common/locator.hpp"
 #include "common/message.hpp"
 #include "common/timer.hpp"
 #include "net/ip6_headers.hpp"

 namespace ot {
 namespace Ip6 {

 /**
  * @addtogroup core-ip6-mpl
  *
  * @brief
  *   This module includes definitions for MPL.
  *
  * @{
  *
  */

 /**
  * This class implements MPL header generation and parsing.
  *
  */
 OT_TOOL_PACKED_BEGIN
 class OptionMpl : public OptionHeader
 {
 public:
     enum
     {
         kType      = 0x6d, /* 01 1 01101 */
         kMinLength = 2
     };

     /**
      * This method initializes the MPL header.
      *
      */
     void Init(void)
     {
         OptionHeader::SetType(kType);
         OptionHeader::SetLength(sizeof(*this) - sizeof(OptionHeader));
         mControl = 0;
     }

     /**
      * This method returns the total MPL Option length value including option
      * header.
      *
      * @returns The total IPv6 Option Length.
      *
      */
     uint8_t GetTotalLength(void) const { return OptionHeader::GetLength() + sizeof(OptionHeader); }

     /**
      * MPL Seed Id lengths.
      */
     enum SeedIdLength
     {
         kSeedIdLength0  = 0 << 6, ///< 0-byte MPL Seed Id Length.
         kSeedIdLength2  = 1 << 6, ///< 2-byte MPL Seed Id Length.
         kSeedIdLength8  = 2 << 6, ///< 8-byte MPL Seed Id Length.
         kSeedIdLength16 = 3 << 6, ///< 16-byte MPL Seed Id Length.
     };

     /**
      * This method returns the MPL Seed Id Length value.
      *
      * @returns The MPL Seed Id Length value.
      *
      */
     SeedIdLength GetSeedIdLength(void) { return static_cast<SeedIdLength>(mControl & kSeedIdLengthMask); }

     /**
      * This method sets the MPL Seed Id Length value.
      *
      * @param[in]  aSeedIdLength  The MPL Seed Length.
      *
      */
     void SetSeedIdLength(SeedIdLength aSeedIdLength)
     {
         mControl = static_cast<uint8_t>((mControl & ~kSeedIdLengthMask) | aSeedIdLength);
     }

     /**
      * This method indicates whether or not the MPL M flag is set.
      *
      * @retval TRUE   If the MPL M flag is set.
      * @retval FALSE  If the MPL M flag is not set.
      *
      */
     bool IsMaxFlagSet(void) const { return (mControl & kMaxFlag) != 0; }

     /**
      * This method clears the MPL M flag.
      *
      */
     void ClearMaxFlag(void) { mControl &= ~kMaxFlag; }

     /**
      * This method sets the MPL M flag.
      *
      */
     void SetMaxFlag(void) { mControl |= kMaxFlag; }

     /**
      * This method returns the MPL Sequence value.
      *
      * @returns The MPL Sequence value.
      *
      */
     uint8_t GetSequence(void) const { return mSequence; }

     /**
      * This method sets the MPL Sequence value.
      *
      * @param[in]  aSequence  The MPL Sequence value.
      *
      */
     void SetSequence(uint8_t aSequence) { mSequence = aSequence; }

     /**
      * This method returns the MPL Seed Id value.
      *
      * @returns The MPL Seed Id value.
      *
      */
     uint16_t GetSeedId(void) const { return HostSwap16(mSeedId); }

     /**
      * This method sets the MPL Seed Id value.
      *
      * @param[in]  aSeedId  The MPL Seed Id value.
      *
      */
     void SetSeedId(uint16_t aSeedId) { mSeedId = HostSwap16(aSeedId); }

 private:
     enum
     {
         kSeedIdLengthMask = 3 << 6,
         kMaxFlag          = 1 << 5
     };
     uint8_t  mControl;
     uint8_t  mSequence;
     uint16_t mSeedId;
 } OT_TOOL_PACKED_END;

 /**
  * This class represents an MPL's Seed Set entry.
  *
  */
 class MplSeedEntry
 {
 public:
     /**
      * This method returns the MPL Seed Id value.
      *
      * @returns The MPL Seed Id value.
      *
      */
     uint16_t GetSeedId(void) const { return mSeedId; }

     /**
      * This method sets the MPL Seed Id value.
      *
      * @param[in]  aSeedId  The MPL Seed Id value.
      *
      */
     void SetSeedId(uint16_t aSeedId) { mSeedId = aSeedId; }

     /**
      * This method returns the MPL Sequence value.
      *
      * @returns The MPL Sequence value.
      *
      */
     uint8_t GetSequence(void) const { return mSequence; }

     /**
      * This method sets the MPL Sequence value.
      *
      * @param[in]  aSequence  The MPL Sequence value.
      *
      */
     void SetSequence(uint8_t aSequence) { mSequence = aSequence; }

     /**
      * This method returns the MPL Seed Set entry's remaining lifetime.
      *
      * @returns The MPL Seed Set entry's remaining lifetime.
      *
      */
     uint8_t GetLifetime(void) const { return mLifetime; }

     /**
      * This method sets the remaining lifetime of the Seed Set entry.
      *
      * @param[in]  aLifetime  The remaining lifetime of the Seed Set entry.
      *
      */
     void SetLifetime(uint8_t aLifetime) { mLifetime = aLifetime; }

 private:
     uint16_t mSeedId;
     uint8_t  mSequence;
     uint8_t  mLifetime;
 };

 /**
  * This class represents metadata required for MPL retransmissions.
  *
  */
 class MplBufferedMessageMetadata
 {
 public:
     /**
      * Default constructor for the object.
      *
      */
     MplBufferedMessageMetadata(void)
         : mSeedId(0)
         , mSequence(0)
         , mTransmissionCount(0)
         , mTransmissionTime(0)
         , mIntervalOffset(0){};

     /**
      * This method appends MPL Buffered Message metadata to the message.
      *
      * @param[in]  aMessage  A reference to the message.
      *
      * @retval OT_ERROR_NONE     Successfully appended the bytes.
      * @retval OT_ERROR_NO_BUFS  Insufficient available buffers to grow the message.
      *
      */
     otError AppendTo(Message &aMessage) const { return aMessage.Append(this, sizeof(*this)); }

     /**
      * This method reads request data from the message.
      *
      * @param[in]  aMessage  A reference to the message.
      *
      */
     void ReadFrom(const Message &aMessage)
     {
         uint16_t length = aMessage.Read(aMessage.GetLength() - sizeof(*this), sizeof(*this), this);
         assert(length == sizeof(*this));
         OT_UNUSED_VARIABLE(length);
     }

     /**
      * This method removes MPL Buffered Message metadata from the message.
      *
      * @param[in]  aMessage  A reference to the message.
      *
      */
     static void RemoveFrom(Message &aMessage)
     {
         otError error = aMessage.SetLength(aMessage.GetLength() - sizeof(MplBufferedMessageMetadata));
         assert(error == OT_ERROR_NONE);
         OT_UNUSED_VARIABLE(error);
     }

     /**
      * This method updates MPL Buffered Message metadata in the message.
      *
      * @param[in]  aMessage  A reference to the message.
      *
      * @returns The number of bytes that have been updated.
      *
      */
     int UpdateIn(Message &aMessage) const
     {
         return aMessage.Write(aMessage.GetLength() - sizeof(*this), sizeof(*this), this);
     }

     /**
      * This method returns the MPL Seed Id value.
      *
      * @returns The MPL Seed Id value.
      *
      */
     uint16_t GetSeedId(void) const { return mSeedId; }

     /**
      * This method sets the MPL Seed Id value.
      *
      * @param[in]  aSeedId  The MPL Seed Id value.
      *
      */
     void SetSeedId(uint16_t aSeedId) { mSeedId = aSeedId; }

     /**
      * This method returns the MPL Sequence value.
      *
      * @returns The MPL Sequence value.
      *
      */
     uint8_t GetSequence(void) const { return mSequence; }

     /**
      * This method sets the MPL Sequence value.
      *
      * @param[in]  aSequence  The MPL Sequence value.
      *
      */
     void SetSequence(uint8_t aSequence) { mSequence = aSequence; }

     /**
      * This method returns the number of already preformed transmissions.
      *
      * @returns The number of already preformed transmissions.
      *
      */
     uint8_t GetTransmissionCount(void) const { return mTransmissionCount; }

     /**
      * This method sets the number of already performed transmissions.
      *
      * @param[in]  aTransmissionCount  The number of already performed transmissions.
      *
      */
     void SetTransmissionCount(uint8_t aTransmissionCount) { mTransmissionCount = aTransmissionCount; }

     /**
      * This method returns the transmission timestamp of the message.
      *
      * @returns The transmission timestamp of the message.
      *
      */
     TimeMilli GetTransmissionTime(void) const { return mTransmissionTime; }

     /**
      * This method sets the transmission timestamp of the message.
      *
      * @param[in]  aTransmissionTime  The transmission timestamp of the message.
      *
      */
     void SetTransmissionTime(TimeMilli aTransmissionTime) { mTransmissionTime = aTransmissionTime; }

     /**
      * This method returns the offset from the transmission time to the end of trickle interval.
      *
      * @returns The offset from the transmission time to the end of trickle interval.
      *
      */
     uint8_t GetIntervalOffset(void) const { return mIntervalOffset; }

     /**
      * This method sets the offset from the transmission time to the end of trickle interval.
      *
      * @param[in]  aIntervalOffset  The offset from the transmission time to the end of trickle interval.
      *
      */
     void SetIntervalOffset(uint8_t aIntervalOffset) { mIntervalOffset = aIntervalOffset; }

     /**
      * This method generates the next transmission time for the MPL Data Message.
      *
      * @param[in] aCurrentTime Current time (in milliseconds).
      * @param[in] aInterval    The current interval size (in milliseconds).
      */
     void GenerateNextTransmissionTime(TimeMilli aCurrentTime, uint8_t aInterval);

 private:
     uint16_t  mSeedId;
     uint8_t   mSequence;
     uint8_t   mTransmissionCount;
     TimeMilli mTransmissionTime;
     uint8_t   mIntervalOffset;
 };

 /**
  * This class implements MPL message processing.
  *
  */
 class Mpl : public InstanceLocator
 {
 public:
     /**
      * This constructor initializes the MPL object.
      *
      * @param[in]  aInstance  A reference to the OpenThread instance.
      *
      */
     explicit Mpl(Instance &aInstance);

     /**
      * This method initializes the MPL option.
      *
      * @param[in]  aOption   A reference to the MPL header to initialize.
      * @param[in]  aAddress  A reference to the IPv6 Source Address.
      *
      */
     void InitOption(OptionMpl &aOption, const Address &aAddress);

     /**
      * This method processes an MPL option. When the MPL module acts as an MPL Forwarder
      * it disseminates MPL Data Message using Trickle timer expirations. When acts as an
      * MPL Seed it allows to send the first MPL Data Message directly, then sets up Trickle
      * timer expirations for subsequent retransmissions.
      *
      * @param[in]  aMessage    A reference to the message.
      * @param[in]  aAddress    A reference to the IPv6 Source Address.
      * @param[in]  aIsOutbound TRUE if this message was locally generated, FALSE otherwise.
      *
      * @retval OT_ERROR_NONE  Successfully processed the MPL option.
      * @retval OT_ERROR_DROP  The MPL message is a duplicate and should be dropped.
      *
      */
     otError ProcessOption(Message &aMessage, const Address &aAddress, bool aIsOutbound);

     /**
      * This method returns the MPL Seed Id value.
      *
      * @returns The MPL Seed Id value.
      *
      */
     uint16_t GetSeedId(void) const { return mSeedId; }

     /**
      * This method sets the MPL Seed Id value.
      *
      * @param[in]  aSeedId  The MPL Seed Id value.
      *
      */
     void SetSeedId(uint16_t aSeedId) { mSeedId = aSeedId; }

     /**
      * This method gets the MPL number of Trickle timer expirations that occur before
      * terminating the Trickle algorithm's retransmission of a given MPL Data Message.
      *
      * @returns The MPL number of Trickle timer expirations.
      *
      */
     uint8_t GetTimerExpirations(void) const { return mTimerExpirations; }

     /**
      * This method sets the MPL number of Trickle timer expirations that occur before
      * terminating the Trickle algorithm's retransmission of a given MPL Data Message.
      *
      * @param[in]  aTimerExpirations  The number of Trickle timer expirations.
      *
      */
     void SetTimerExpirations(uint8_t aTimerExpirations) { mTimerExpirations = aTimerExpirations; }

     /**
      * This method sets the IPv6 matching address, that allows to elide MPL Seed Id.
      *
      * @param[in] aAddress The reference to the IPv6 matching address.
      *
      */
     void SetMatchingAddress(const Address &aAddress) { mMatchingAddress = &aAddress; }

     /**
      * This method returns a reference to the buffered message set.
      *
      * @returns A reference to the buffered message set.
      *
      */
     const MessageQueue &GetBufferedMessageSet(void) const { return mBufferedMessageSet; }

 private:
     enum
     {
         kNumSeedEntries      = OPENTHREAD_CONFIG_MPL_SEED_SET_ENTRIES,
         kSeedEntryLifetime   = OPENTHREAD_CONFIG_MPL_SEED_SET_ENTRY_LIFETIME,
         kSeedEntryLifetimeDt = 1000,
         kDataMessageInterval = 64
     };

     otError UpdateSeedSet(uint16_t aSeedId, uint8_t aSequence);
     void    UpdateBufferedSet(uint16_t aSeedId, uint8_t aSequence);
     void    AddBufferedMessage(Message &aMessage, uint16_t aSeedId, uint8_t aSequence, bool aIsOutbound);

     static void HandleSeedSetTimer(Timer &aTimer);
     void        HandleSeedSetTimer(void);

     static void HandleRetransmissionTimer(Timer &aTimer);
     void        HandleRetransmissionTimer(void);

     uint8_t  mTimerExpirations;
     uint8_t  mSequence;
     uint16_t mSeedId;

     TimerMilli mSeedSetTimer;
     TimerMilli mRetransmissionTimer;

     const Address *mMatchingAddress;

     MplSeedEntry mSeedSet[kNumSeedEntries];
     MessageQueue mBufferedMessageSet;
 };

 /**
  * @}
  *
  */

 } // namespace Ip6
 } // namespace ot

 #endif // IP6_MPL_HPP_
	/*
	* Copyright (c) 2016, The OpenThread Authors.
	* 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 copyright holder 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 COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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 IP6_MPL_HPP_
	#define IP6_MPL_HPP_

	/**
	* @file
	* This file includes definitions for MPL.
	*/

	#include "openthread-core-config.h"

	#include "common/locator.hpp"
	#include "common/message.hpp"
	#include "common/timer.hpp"
	#include "net/ip6_headers.hpp"

	namespace ot {
	namespace Ip6 {

	/**
	* @addtogroup core-ip6-mpl
	*
	* @brief
	* This module includes definitions for MPL.
	*
	* @{
	*
	*/

	/**
	* This class implements MPL header generation and parsing.
	*
	*/
	OT_TOOL_PACKED_BEGIN
	class OptionMpl : public OptionHeader
	{
	public:
	enum
	{
	kType = 0x6d, /* 01 1 01101 */
	kMinLength = 2
	};

	/**
	* This method initializes the MPL header.
	*
	*/
	void Init(void)
	{
	OptionHeader::SetType(kType);
	OptionHeader::SetLength(sizeof(*this) - sizeof(OptionHeader));
	mControl = 0;
	}

	/**
	* This method returns the total MPL Option length value including option
	* header.
	*
	* @returns The total IPv6 Option Length.
	*
	*/
	uint8_t GetTotalLength(void) const { return OptionHeader::GetLength() + sizeof(OptionHeader); }

	/**
	* MPL Seed Id lengths.
	*/
	enum SeedIdLength
	{
	kSeedIdLength0 = 0 << 6, ///< 0-byte MPL Seed Id Length.
	kSeedIdLength2 = 1 << 6, ///< 2-byte MPL Seed Id Length.
	kSeedIdLength8 = 2 << 6, ///< 8-byte MPL Seed Id Length.
	kSeedIdLength16 = 3 << 6, ///< 16-byte MPL Seed Id Length.
	};

	/**
	* This method returns the MPL Seed Id Length value.
	*
	* @returns The MPL Seed Id Length value.
	*
	*/
	SeedIdLength GetSeedIdLength(void) { return static_cast<SeedIdLength>(mControl & kSeedIdLengthMask); }

	/**
	* This method sets the MPL Seed Id Length value.
	*
	* @param[in] aSeedIdLength The MPL Seed Length.
	*
	*/
	void SetSeedIdLength(SeedIdLength aSeedIdLength)
	{
	mControl = static_cast<uint8_t>((mControl & ~kSeedIdLengthMask) \| aSeedIdLength);
	}

	/**
	* This method indicates whether or not the MPL M flag is set.
	*
	* @retval TRUE If the MPL M flag is set.
	* @retval FALSE If the MPL M flag is not set.
	*
	*/
	bool IsMaxFlagSet(void) const { return (mControl & kMaxFlag) != 0; }

	/**
	* This method clears the MPL M flag.
	*
	*/
	void ClearMaxFlag(void) { mControl &= ~kMaxFlag; }

	/**
	* This method sets the MPL M flag.
	*
	*/
	void SetMaxFlag(void) { mControl \|= kMaxFlag; }

	/**
	* This method returns the MPL Sequence value.
	*
	* @returns The MPL Sequence value.
	*
	*/
	uint8_t GetSequence(void) const { return mSequence; }

	/**
	* This method sets the MPL Sequence value.
	*
	* @param[in] aSequence The MPL Sequence value.
	*
	*/
	void SetSequence(uint8_t aSequence) { mSequence = aSequence; }

	/**
	* This method returns the MPL Seed Id value.
	*
	* @returns The MPL Seed Id value.
	*
	*/
	uint16_t GetSeedId(void) const { return HostSwap16(mSeedId); }

	/**
	* This method sets the MPL Seed Id value.
	*
	* @param[in] aSeedId The MPL Seed Id value.
	*
	*/
	void SetSeedId(uint16_t aSeedId) { mSeedId = HostSwap16(aSeedId); }

	private:
	enum
	{
	kSeedIdLengthMask = 3 << 6,
	kMaxFlag = 1 << 5
	};
	uint8_t mControl;
	uint8_t mSequence;
	uint16_t mSeedId;
	} OT_TOOL_PACKED_END;

	/**
	* This class represents an MPL's Seed Set entry.
	*
	*/
	class MplSeedEntry
	{
	public:
	/**
	* This method returns the MPL Seed Id value.
	*
	* @returns The MPL Seed Id value.
	*
	*/
	uint16_t GetSeedId(void) const { return mSeedId; }

	/**
	* This method sets the MPL Seed Id value.
	*
	* @param[in] aSeedId The MPL Seed Id value.
	*
	*/
	void SetSeedId(uint16_t aSeedId) { mSeedId = aSeedId; }

	/**
	* This method returns the MPL Sequence value.
	*
	* @returns The MPL Sequence value.
	*
	*/
	uint8_t GetSequence(void) const { return mSequence; }

	/**
	* This method sets the MPL Sequence value.
	*
	* @param[in] aSequence The MPL Sequence value.
	*
	*/
	void SetSequence(uint8_t aSequence) { mSequence = aSequence; }

	/**
	* This method returns the MPL Seed Set entry's remaining lifetime.
	*
	* @returns The MPL Seed Set entry's remaining lifetime.
	*
	*/
	uint8_t GetLifetime(void) const { return mLifetime; }

	/**
	* This method sets the remaining lifetime of the Seed Set entry.
	*
	* @param[in] aLifetime The remaining lifetime of the Seed Set entry.
	*
	*/
	void SetLifetime(uint8_t aLifetime) { mLifetime = aLifetime; }

	private:
	uint16_t mSeedId;
	uint8_t mSequence;
	uint8_t mLifetime;
	};

	/**
	* This class represents metadata required for MPL retransmissions.
	*
	*/
	class MplBufferedMessageMetadata
	{
	public:
	/**
	* Default constructor for the object.
	*
	*/
	MplBufferedMessageMetadata(void)
	: mSeedId(0)
	, mSequence(0)
	, mTransmissionCount(0)
	, mTransmissionTime(0)
	, mIntervalOffset(0){};

	/**
	* This method appends MPL Buffered Message metadata to the message.
	*
	* @param[in] aMessage A reference to the message.
	*
	* @retval OT_ERROR_NONE Successfully appended the bytes.
	* @retval OT_ERROR_NO_BUFS Insufficient available buffers to grow the message.
	*
	*/
	otError AppendTo(Message &aMessage) const { return aMessage.Append(this, sizeof(*this)); }

	/**
	* This method reads request data from the message.
	*
	* @param[in] aMessage A reference to the message.
	*
	*/
	void ReadFrom(const Message &aMessage)
	{
	uint16_t length = aMessage.Read(aMessage.GetLength() - sizeof(this), sizeof(this), this);
	assert(length == sizeof(*this));
	OT_UNUSED_VARIABLE(length);
	}

	/**
	* This method removes MPL Buffered Message metadata from the message.
	*
	* @param[in] aMessage A reference to the message.
	*
	*/
	static void RemoveFrom(Message &aMessage)
	{
	otError error = aMessage.SetLength(aMessage.GetLength() - sizeof(MplBufferedMessageMetadata));
	assert(error == OT_ERROR_NONE);
	OT_UNUSED_VARIABLE(error);
	}

	/**
	* This method updates MPL Buffered Message metadata in the message.
	*
	* @param[in] aMessage A reference to the message.
	*
	* @returns The number of bytes that have been updated.
	*
	*/
	int UpdateIn(Message &aMessage) const
	{
	return aMessage.Write(aMessage.GetLength() - sizeof(this), sizeof(this), this);
	}

	/**
	* This method returns the MPL Seed Id value.
	*
	* @returns The MPL Seed Id value.
	*
	*/
	uint16_t GetSeedId(void) const { return mSeedId; }

	/**
	* This method sets the MPL Seed Id value.
	*
	* @param[in] aSeedId The MPL Seed Id value.
	*
	*/
	void SetSeedId(uint16_t aSeedId) { mSeedId = aSeedId; }

	/**
	* This method returns the MPL Sequence value.
	*
	* @returns The MPL Sequence value.
	*
	*/
	uint8_t GetSequence(void) const { return mSequence; }

	/**
	* This method sets the MPL Sequence value.
	*
	* @param[in] aSequence The MPL Sequence value.
	*
	*/
	void SetSequence(uint8_t aSequence) { mSequence = aSequence; }

	/**
	* This method returns the number of already preformed transmissions.
	*
	* @returns The number of already preformed transmissions.
	*
	*/
	uint8_t GetTransmissionCount(void) const { return mTransmissionCount; }

	/**
	* This method sets the number of already performed transmissions.
	*
	* @param[in] aTransmissionCount The number of already performed transmissions.
	*
	*/
	void SetTransmissionCount(uint8_t aTransmissionCount) { mTransmissionCount = aTransmissionCount; }

	/**
	* This method returns the transmission timestamp of the message.
	*
	* @returns The transmission timestamp of the message.
	*
	*/
	TimeMilli GetTransmissionTime(void) const { return mTransmissionTime; }

	/**
	* This method sets the transmission timestamp of the message.
	*
	* @param[in] aTransmissionTime The transmission timestamp of the message.
	*
	*/
	void SetTransmissionTime(TimeMilli aTransmissionTime) { mTransmissionTime = aTransmissionTime; }

	/**
	* This method returns the offset from the transmission time to the end of trickle interval.
	*
	* @returns The offset from the transmission time to the end of trickle interval.
	*
	*/
	uint8_t GetIntervalOffset(void) const { return mIntervalOffset; }

	/**
	* This method sets the offset from the transmission time to the end of trickle interval.
	*
	* @param[in] aIntervalOffset The offset from the transmission time to the end of trickle interval.
	*
	*/
	void SetIntervalOffset(uint8_t aIntervalOffset) { mIntervalOffset = aIntervalOffset; }

	/**
	* This method generates the next transmission time for the MPL Data Message.
	*
	* @param[in] aCurrentTime Current time (in milliseconds).
	* @param[in] aInterval The current interval size (in milliseconds).
	*/
	void GenerateNextTransmissionTime(TimeMilli aCurrentTime, uint8_t aInterval);

	private:
	uint16_t mSeedId;
	uint8_t mSequence;
	uint8_t mTransmissionCount;
	TimeMilli mTransmissionTime;
	uint8_t mIntervalOffset;
	};

	/**
	* This class implements MPL message processing.
	*
	*/
	class Mpl : public InstanceLocator
	{
	public:
	/**
	* This constructor initializes the MPL object.
	*
	* @param[in] aInstance A reference to the OpenThread instance.
	*
	*/
	explicit Mpl(Instance &aInstance);

	/**
	* This method initializes the MPL option.
	*
	* @param[in] aOption A reference to the MPL header to initialize.
	* @param[in] aAddress A reference to the IPv6 Source Address.
	*
	*/
	void InitOption(OptionMpl &aOption, const Address &aAddress);

	/**
	* This method processes an MPL option. When the MPL module acts as an MPL Forwarder
	* it disseminates MPL Data Message using Trickle timer expirations. When acts as an
	* MPL Seed it allows to send the first MPL Data Message directly, then sets up Trickle
	* timer expirations for subsequent retransmissions.
	*
	* @param[in] aMessage A reference to the message.
	* @param[in] aAddress A reference to the IPv6 Source Address.
	* @param[in] aIsOutbound TRUE if this message was locally generated, FALSE otherwise.
	*
	* @retval OT_ERROR_NONE Successfully processed the MPL option.
	* @retval OT_ERROR_DROP The MPL message is a duplicate and should be dropped.
	*
	*/
	otError ProcessOption(Message &aMessage, const Address &aAddress, bool aIsOutbound);

	/**
	* This method returns the MPL Seed Id value.
	*
	* @returns The MPL Seed Id value.
	*
	*/
	uint16_t GetSeedId(void) const { return mSeedId; }

	/**
	* This method sets the MPL Seed Id value.
	*
	* @param[in] aSeedId The MPL Seed Id value.
	*
	*/
	void SetSeedId(uint16_t aSeedId) { mSeedId = aSeedId; }

	/**
	* This method gets the MPL number of Trickle timer expirations that occur before
	* terminating the Trickle algorithm's retransmission of a given MPL Data Message.
	*
	* @returns The MPL number of Trickle timer expirations.
	*
	*/
	uint8_t GetTimerExpirations(void) const { return mTimerExpirations; }

	/**
	* This method sets the MPL number of Trickle timer expirations that occur before
	* terminating the Trickle algorithm's retransmission of a given MPL Data Message.
	*
	* @param[in] aTimerExpirations The number of Trickle timer expirations.
	*
	*/
	void SetTimerExpirations(uint8_t aTimerExpirations) { mTimerExpirations = aTimerExpirations; }

	/**
	* This method sets the IPv6 matching address, that allows to elide MPL Seed Id.
	*
	* @param[in] aAddress The reference to the IPv6 matching address.
	*
	*/
	void SetMatchingAddress(const Address &aAddress) { mMatchingAddress = &aAddress; }

	/**
	* This method returns a reference to the buffered message set.
	*
	* @returns A reference to the buffered message set.
	*
	*/
	const MessageQueue &GetBufferedMessageSet(void) const { return mBufferedMessageSet; }

	private:
	enum
	{
	kNumSeedEntries = OPENTHREAD_CONFIG_MPL_SEED_SET_ENTRIES,
	kSeedEntryLifetime = OPENTHREAD_CONFIG_MPL_SEED_SET_ENTRY_LIFETIME,
	kSeedEntryLifetimeDt = 1000,
	kDataMessageInterval = 64
	};

	otError UpdateSeedSet(uint16_t aSeedId, uint8_t aSequence);
	void UpdateBufferedSet(uint16_t aSeedId, uint8_t aSequence);
	void AddBufferedMessage(Message &aMessage, uint16_t aSeedId, uint8_t aSequence, bool aIsOutbound);

	static void HandleSeedSetTimer(Timer &aTimer);
	void HandleSeedSetTimer(void);

	static void HandleRetransmissionTimer(Timer &aTimer);
	void HandleRetransmissionTimer(void);

	uint8_t mTimerExpirations;
	uint8_t mSequence;
	uint16_t mSeedId;

	TimerMilli mSeedSetTimer;
	TimerMilli mRetransmissionTimer;

	const Address *mMatchingAddress;

	MplSeedEntry mSeedSet[kNumSeedEntries];
	MessageQueue mBufferedMessageSet;
	};

	/**
	* @}
	*
	*/

	} // namespace Ip6
	} // namespace ot

	#endif // IP6_MPL_HPP_