text: /*
   *  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/non_copyable.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 implements MPL message processing.
   *
   */
  class Mpl : public InstanceLocator, private NonCopyable
  {
  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 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; }
  
  #if OPENTHREAD_FTD
      /**
       * 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 returns a reference to the buffered message set.
       *
       * @returns A reference to the buffered message set.
       *
       */
      const MessageQueue &GetBufferedMessageSet(void) const { return mBufferedMessageSet; }
  #endif // OPENTHREAD_FTD
  
  private:
      enum
      {
          kNumSeedEntries      = OPENTHREAD_CONFIG_MPL_SEED_SET_ENTRIES,
          kSeedEntryLifetime   = OPENTHREAD_CONFIG_MPL_SEED_SET_ENTRY_LIFETIME,
          kSeedEntryLifetimeDt = 1000,
          kDataMessageInterval = 64
      };
  
      struct SeedEntry
      {
          uint16_t mSeedId;
          uint8_t  mSequence;
          uint8_t  mLifetime;
      };
  
      static void HandleSeedSetTimer(Timer &aTimer);
      void        HandleSeedSetTimer(void);
  
      otError UpdateSeedSet(uint16_t aSeedId, uint8_t aSequence);
  
      SeedEntry      mSeedSet[kNumSeedEntries];
      const Address *mMatchingAddress;
      TimerMilli     mSeedSetTimer;
      uint16_t       mSeedId;
      uint8_t        mSequence;
  
  #if OPENTHREAD_FTD
      struct Metadata
      {
          otError AppendTo(Message &aMessage) const { return aMessage.Append(*this); }
          void    ReadFrom(const Message &aMessage);
          void    RemoveFrom(Message &aMessage) const;
          void    UpdateIn(Message &aMessage) const;
          void    GenerateNextTransmissionTime(TimeMilli aCurrentTime, uint8_t aInterval);
  
          TimeMilli mTransmissionTime;
          uint16_t  mSeedId;
          uint8_t   mSequence;
          uint8_t   mTransmissionCount;
          uint8_t   mIntervalOffset;
      };
  
      static void HandleRetransmissionTimer(Timer &aTimer);
      void        HandleRetransmissionTimer(void);
  
      void AddBufferedMessage(Message &aMessage, uint16_t aSeedId, uint8_t aSequence, bool aIsOutbound);
  
      MessageQueue mBufferedMessageSet;
      TimerMilli   mRetransmissionTimer;
      uint8_t      mTimerExpirations;
  #endif // OPENTHREAD_FTD
  };
  
  /**
   * @}
   *
   */
  
  } // namespace Ip6
  } // namespace ot
  
  #endif // IP6_MPL_HPP_
  