code: func replyWithReset(s *segment) {
  	// Get the seqnum from the packet if the ack flag is set.
  	seq := seqnum.Value(0)
  	if s.flagIsSet(header.TCPFlagAck) {
  		seq = s.ackNumber
  	}
  
  	ack := s.sequenceNumber.Add(s.logicalLen())
  
  	sendTCP(&s.route, s.id, buffer.VectorisedView{}, s.route.DefaultTTL(), header.TCPFlagRst|header.TCPFlagAck, seq, ack, 0, nil /* options */, nil /* gso */)
  }
docs: // replyWithReset replies to the given segment with a reset segment.