Ceph

Create a new message type MMonSync, to dissociate it from the MMonProbe messages, and to allow us to use fields specific to the Synchronization process.

This new message shall have the following operation types:

 /**
  * Start synchronization request
  * (mon.X -> Leader)
  */
  OP_START        = 1,
  /**
   * Reply to an OP_START
   * (Leader -> mon.X)
   */
  OP_START_REPLY    = 2,
  /**
   * Let the Leader know we are still synchronizing
   * (mon.X -> Leader)
   */
  OP_HEARTBEAT    = 3,
  /**
   * Reply to a hearbeat
   * (Leader -> mon.X)
   */
  OP_HEARTBEAT_REPLY    = 4,
  /**
   * Let the Leader know we finished synchronizing
   * (mon.X -> Leader)
   */
  OP_FINISH        = 5,
  /**
   * Request a given monitor (mon.Y) to start synchronizing with us, hence
   * sending us chunks.
   * (mon.X -> mon.Y)
   */
  OP_START_CHUNKS    = 6,
  /**
   * Send a chunk to a given monitor (mon.X)
   * (mon.Y -> mon.X)
   */
  OP_CHUNK        = 7,
  /**
   * Acknowledge that we received the last chunk sent
   * (mon.X -> mon.Y)
   */
  OP_CHUNK_REPLY    = 8,
  /**
   * Reply to an OP_FINISH
   * (Leader -> mon.X)
   */
  OP_FINISH_REPLY    = 9,
  /**
   * Let the receiver know that he should abort whatever he is in the middle
   * of doing with the sender.
   */
  OP_ABORT        = 10

This message shall have the following flags:

  /**
   * Chunk is the last available
   */
  const static uint8_t FLAG_LAST      = 0x01;
  /**
   * Let the other monitor it should retry again its last operation.
   */
  const static uint8_t FLAG_RETRY     = 0x02;
  /**
   * This message contains a crc
   */
  const static uint8_t FLAG_CRC          = 0x04;
  /**
   * Do not reply to this message to the sender, but to @p reply_to.
   */
  const static uint8_t FLAG_REPLY_TO  = 0x08;

This message shall have the following fields:

  uint32_t op;
  uint8_t flags;
  version_t version;
  bufferlist chunk_bl;
  pair<string,string> last_key;
  __u32 crc;
  entity_inst_t reply_to;