code: def _read_mode_mptcp(self, size, kind):
          
          bins = self._read_binary(1)
          subt = int(bins[:4], base=2)    # subtype number
          bits = bins[4:]                 # 4-bit data
          dlen = size - 1                 # length of remaining data
  
          # fetch subtype-specific data
          func = mptcp_opt.get(subt)
          if func is None:    # if subtype not exist, directly read all data
              temp = self._read_fileng(dlen)
              data = dict(
                  kind=kind,
                  length=size,
                  subtype='Unknown',
                  data=bytes(chr(int(bits[:4], base=2)), encoding='utf-8') + temp,
              )
          else:               # fetch corresponding subtype data dict
              data = func(self, bits, dlen, kind)
          return data
docs: Read Multipath TCP option.
  
          Positional arguments:
              * size - int, length of option
              * kind - int, 30 (Multipath TCP)
  
          Returns:
              * dict -- extracted Multipath TCP (MP-TCP) option
  
          Structure of MP-TCP [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|                       |
              +---------------+---------------+-------+                       |
              |                     Subtype-specific data                     |
              |                       (variable length)                       |
              +---------------------------------------------------------------+
  
              Octets      Bits        Name                    Description
                0           0     tcp.mp.kind             Kind (30)
                1           8     tcp.mp.length           Length
                2          16     tcp.mp.subtype          Subtype
                2          20     tcp.mp.data             Subtype-specific Data