def _read_mptcp_fastclose(self, bits, size):
        """Read Fast Close option.

        Positional arguments:
            * bits - str, 4-bit data
            * size - int, length of option

        Returns:
            * dict -- extracted Fast Close (MP_FASTCLOSE) option

        Structure of MP_FASTCLOSE [RFC 6824]:
                                 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
            +---------------+---------------+-------+-----------------------+
            |     Kind      |    Length     |Subtype|      (reserved)       |
            +---------------+---------------+-------+-----------------------+
            |                      Option Receiver's Key                    |
            |                            (64 bits)                          |
            |                                                               |
            +---------------------------------------------------------------+

            Octets      Bits        Name                        Description
              0           0     tcp.opt.kind                Kind (30)
              1           8     tcp.opt.length              Length (12)
              2          16     tcp.opt.mp.subtype          Subtype (7)
              2          23     -                           Reserved (must be zero)
              4          32     tcp.opt.mp.fastclose.rkey   Option Receiver's Key

        """
        ____ = self._read_fileng(1)
        rkey = self._read_fileng(8)

        data = dict(
            subtype='MP_FASTCLOSE',
            fastclose=dict(
                rkey=rkey,
            ),
        )

        return data
Read Fast Close option.

        Positional arguments:
            * bits - str, 4-bit data
            * size - int, length of option

        Returns:
            * dict -- extracted Fast Close (MP_FASTCLOSE) option

        Structure of MP_FASTCLOSE [RFC 6824]:
                                 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
            +---------------+---------------+-------+-----------------------+
            |     Kind      |    Length     |Subtype|      (reserved)       |
            +---------------+---------------+-------+-----------------------+
            |                      Option Receiver's Key                    |
            |                            (64 bits)                          |
            |                                                               |
            +---------------------------------------------------------------+

            Octets      Bits        Name                        Description
              0           0     tcp.opt.kind                Kind (30)
              1           8     tcp.opt.length              Length (12)
              2          16     tcp.opt.mp.subtype          Subtype (7)
              2          23     -                           Reserved (must be zero)
              4          32     tcp.opt.mp.fastclose.rkey   Option Receiver's Key