dns-handle-packat.go

func (d *DNSResolver) handlePacket(pc net.PacketConn, addr net.Addr, payload []byte) error {
	var parser dnsm.Parser
	log := d.log.Named("handlePacket")

	header, err := parser.Start(payload)
	if err != nil {
		return fmt.Errorf("start parsing payload: %w", err)
	}

	question, err := parser.Question()
	if err != nil {
		return fmt.Errorf("parse question: %w", err)
	}

	log.Debugw("handling", "question", fmt.Sprintf("%+v", question), "requester", addr.String())

	response, err := d.QueryRootServers(question)
	if err != nil {
		return fmt.Errorf("query root servers: %w", err)
	}

	response.ID = header.ID

	if len(response.Answers) > 0 {
		logResolved := log.With("question", question.Name.String())
		for _, a := range response.Answers {
			answer := ""
			switch m := a.Body.(type) {
			case *dnsm.AResource:
				answer = net.IP(m.A[:]).String()
			case *dnsm.CNAMEResource:
				answer = m.CNAME.String()
			case *dnsm.MXResource:
				answer = m.MX.String()
			}
			logResolved.Infow("resovled", "answer", answer)
		}
	}

	responsePayload, err := response.Pack()
	if err != nil {
		return fmt.Errorf("parse root server response: %w", err)
	}

	_, err = pc.WriteTo(responsePayload, addr)

	if err != nil {
		return fmt.Errorf("write response payload to address: %w", err)
	}

	return nil
}