code: func (s *Stack) SetTransportProtocolOption(transport tcpip.TransportProtocolNumber, option interface{}) *tcpip.Error {
  	transProtoState, ok := s.transportProtocols[transport]
  	if !ok {
  		return tcpip.ErrUnknownProtocol
  	}
  	return transProtoState.proto.SetOption(option)
  }
docs: // SetTransportProtocolOption allows configuring individual protocol level
  // options. This method returns an error if the protocol is not supported or
  // option is not supported by the protocol implementation or the provided value
  // is incorrect.