code: func (h *handshake) resetToSynRcvd(iss seqnum.Value, irs seqnum.Value, opts *header.TCPSynOptions) {
  	h.active = false
  	h.state = handshakeSynRcvd
  	h.flags = header.TCPFlagSyn | header.TCPFlagAck
  	h.iss = iss
  	h.ackNum = irs + 1
  	h.mss = opts.MSS
  	h.sndWndScale = opts.WS
  }
docs: // resetToSynRcvd resets the state of the handshake object to the SYN-RCVD
  // state.