initiator                                                    listener
    |                                                           |
    |    S  0(20) <MP_CAPABLE>, <TFO cookie>                    |
    | --------------------------------------------------------> |
    |                                                           |
    |    S. 0(0) ack 1 <MP_CAPABLE>                             |
    | <-------------------------------------------------------- |
    |                                                           |
    |    .  1(0) ack 1 <MP_CAPABLE>                             |
    | --------------------------------------------------------> |
    |                                                           |
    |    .  1(20) ack 1 <DSS ack=1 seq=1 ssn=1 dlen=20>         |
    | --------------------------------------------------------> |
    |                                                           |
    |    .  0(0) ack 21 <DSS ack=21 seq=1 ssn=1 dlen=0>         |
    | <-------------------------------------------------------- |
    |                                                           |