Golang Msg.Answer方法代碼示例

func (manager *DnsManager) dnsHandler(w dns.ResponseWriter, req *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(req)

	name := req.Question[0].Name
	name = strings.TrimSuffix(name, "."+manager.BaseName)

	manager.dbMutex.Lock()
	entry, ok := manager.db[name]
	manager.dbMutex.Unlock()

	if ok {
		switch req.Question[0].Qtype {
		case dns.TypeSRV:
			m.Answer = manager.makeAllSRV(entry)
		case dns.TypeA:
			m.Answer = manager.makeAllA(entry)
			if manager.PushSRV {
				m.Extra = manager.makeAllSRV(entry)
			}
		}
	}

	w.WriteMsg(m)
}

func TestShuffleAnswers(t *testing.T) {
	var res Resolver

	m := new(dns.Msg)

	for i := 0; i < 10; i++ {
		name := "10.0.0." + strconv.Itoa(i)
		rr, err := res.formatA("blah.com", name)
		if err != nil {
			t.Error(err)
		}
		m.Answer = append(m.Answer, rr)
	}

	n := new(dns.Msg)
	c := make([]dns.RR, len(m.Answer))
	copy(c, m.Answer)
	n.Answer = c

	_ = shuffleAnswers(m.Answer)

	sflag := false
	// 10! chance of failing here
	for i := 0; i < 10; i++ {
		if n.Answer[i] != m.Answer[i] {
			sflag = true
			break
		}
	}

	if !sflag {
		t.Error("not shuffling")
	}
}

func handleSpecialNames(w dns.ResponseWriter, req *dns.Msg) bool {
	question := req.Question[0]
	nameLC := strings.ToLower(question.Name)
	for _, localRR := range localRRS {
		if nameLC == localRR.Name {
			m := new(dns.Msg)
			m.Id = req.Id
			m.Answer = []dns.RR{*localRR.RR}
			m.Response = true
			w.WriteMsg(m)
			return true
		}
	}
	if question.Qtype != dns.TypeANY {
		return false
	}
	m := new(dns.Msg)
	m.Id = req.Id
	hinfo := new(dns.HINFO)
	hinfo.Hdr = dns.RR_Header{Name: question.Name, Rrtype: dns.TypeHINFO,
		Class: dns.ClassINET, Ttl: 86400}
	hinfo.Cpu = "ANY is not supported any more"
	hinfo.Os = "See draft-jabley-dnsop-refuse-any"
	m.Answer = []dns.RR{hinfo}
	m.Response = true
	w.WriteMsg(m)
	return true
}

func (s *DNSServer) handleARequest(r *dns.Msg, m *dns.Msg) {
	m.Answer = make([]dns.RR, 0, 2)
	query := r.Question[0].Name

	if query[len(query)-1] == '.' {
		query = query[:len(query)-1]
	}

	for service := range s.queryServices(query) {
		rr := new(dns.A)

		var ttl int
		if service.Ttl != -1 {
			ttl = service.Ttl
		} else {
			ttl = s.config.ttl
		}

		rr.Hdr = dns.RR_Header{
			Name:   r.Question[0].Name,
			Rrtype: dns.TypeA,
			Class:  dns.ClassINET,
			Ttl:    uint32(ttl),
		}
		rr.A = service.Ip
		m.Answer = append(m.Answer, rr)
	}
}

func (s *DNSServer) handlePTRRequest(r *dns.Msg, m *dns.Msg) {
	m.Answer = make([]dns.RR, 0, 2)
	query := r.Question[0].Name

	if query[len(query)-1] == '.' {
		query = query[:len(query)-1]
	}

	for service := range s.queryIp(query) {
		var ttl int
		if service.Ttl != -1 {
			ttl = service.Ttl
		} else {
			ttl = s.config.ttl
		}

		for domain := range s.listDomains(service) {
			rr := new(dns.PTR)
			rr.Hdr = dns.RR_Header{
				Name:   r.Question[0].Name,
				Rrtype: dns.TypePTR,
				Class:  dns.ClassINET,
				Ttl:    uint32(ttl),
			}
			rr.Ptr = domain

			m.Answer = append(m.Answer, rr)
		}
	}
}

func (h dnsHandler) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
	if len(r.Question) != 1 {
		h.t.Fatalf("bad: %#v", r.Question)
	}

	name := "join.service.consul."
	question := r.Question[0]
	if question.Name != name || question.Qtype != dns.TypeANY {
		h.t.Fatalf("bad: %#v", question)
	}

	m := new(dns.Msg)
	m.SetReply(r)
	m.Authoritative = true
	m.RecursionAvailable = false
	m.Answer = append(m.Answer, &dns.A{
		Hdr: dns.RR_Header{
			Name:   name,
			Rrtype: dns.TypeA,
			Class:  dns.ClassINET},
		A: net.ParseIP("127.0.0.1"),
	})
	m.Answer = append(m.Answer, &dns.AAAA{
		Hdr: dns.RR_Header{
			Name:   name,
			Rrtype: dns.TypeAAAA,
			Class:  dns.ClassINET},
		AAAA: net.ParseIP("2001:db8:a0b:12f0::1"),
	})
	if err := w.WriteMsg(m); err != nil {
		h.t.Fatalf("err: %v", err)
	}
}

func (r *resolver) handleIPQuery(name string, query *dns.Msg, ipType int) (*dns.Msg, error) {
	addr := r.sb.ResolveName(name, ipType)
	if addr == nil {
		return nil, nil
	}

	log.Debugf("Lookup for %s: IP %v", name, addr)

	resp := new(dns.Msg)
	resp.SetReply(query)
	setCommonFlags(resp)

	if len(addr) > 1 {
		addr = shuffleAddr(addr)
	}
	if ipType == netutils.IPv4 {
		for _, ip := range addr {
			rr := new(dns.A)
			rr.Hdr = dns.RR_Header{Name: name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: respTTL}
			rr.A = ip
			resp.Answer = append(resp.Answer, rr)
		}
	} else {
		for _, ip := range addr {
			rr := new(dns.AAAA)
			rr.Hdr = dns.RR_Header{Name: name, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: respTTL}
			rr.AAAA = ip
			resp.Answer = append(resp.Answer, rr)
		}
	}
	return resp, nil
}

// handlerFunc receives requests, looks up the result and returns what is found.
func handlerFunc(res dns.ResponseWriter, req *dns.Msg) {
	message := new(dns.Msg)
	switch req.Opcode {
	case dns.OpcodeQuery:
		message.SetReply(req)
		message.Compress = false
		message.Answer = make([]dns.RR, 0)

		for _, question := range message.Question {
			answers := answerQuestion(strings.ToLower(question.Name), question.Qtype)
			if len(answers) > 0 {
				for i := range answers {
					message.Answer = append(message.Answer, answers[i])
				}
			} else {
				// If there are no records, go back through and search for SOA records
				for _, question := range message.Question {
					answers := answerQuestion(strings.ToLower(question.Name), dns.TypeSOA)
					for i := range answers {
						message.Ns = append(message.Ns, answers[i])
					}
				}
			}
		}
		if len(message.Answer) == 0 && len(message.Ns) == 0 {
			message.Rcode = dns.RcodeNameError
		}
	default:
		message = message.SetRcode(req, dns.RcodeNotImplemented)
	}
	res.WriteMsg(message)
}

func (c Chaos) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
	state := middleware.State{W: w, Req: r}
	if state.QClass() != dns.ClassCHAOS || state.QType() != dns.TypeTXT {
		return c.Next.ServeDNS(ctx, w, r)
	}

	m := new(dns.Msg)
	m.SetReply(r)

	hdr := dns.RR_Header{Name: state.QName(), Rrtype: dns.TypeTXT, Class: dns.ClassCHAOS, Ttl: 0}
	switch state.Name() {
	default:
		return c.Next.ServeDNS(ctx, w, r)
	case "authors.bind.":
		for a, _ := range c.Authors {
			m.Answer = append(m.Answer, &dns.TXT{Hdr: hdr, Txt: []string{trim(a)}})
		}
	case "version.bind.", "version.server.":
		m.Answer = []dns.RR{&dns.TXT{Hdr: hdr, Txt: []string{trim(c.Version)}}}
	case "hostname.bind.", "id.server.":
		hostname, err := os.Hostname()
		if err != nil {
			hostname = "localhost"
		}
		m.Answer = []dns.RR{&dns.TXT{Hdr: hdr, Txt: []string{trim(hostname)}}}
	}
	state.SizeAndDo(m)
	w.WriteMsg(m)
	return 0, nil
}

func (s HelixServer) Handler(w dns.ResponseWriter, req *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(req)

	qType := req.Question[0].Qtype
	qClass := req.Question[0].Qclass

	header := dns.RR_Header{Name: m.Question[0].Name, Rrtype: qType, Class: qClass, Ttl: 5}
	resp, err := s.getResponse(req.Question[0])

	if err != nil {
		if s.DNSClient != nil {
			log.Printf("Could not get record for %s, forwarding to %s", req.Question[0].Name, s.DNSClient.GetAddress())
			in, _ := s.DNSClient.Lookup(req)
			w.WriteMsg(in)
		} else {
			log.Printf("Could not get record for %s", req.Question[0].Name)
			w.WriteMsg(m)
		}
		return
	}

	switch qType {
	case dns.TypeA:
		m.Answer = make([]dns.RR, 1)
		m.Answer[0] = &dns.A{Hdr: header, A: net.ParseIP(resp.Value())}
	case dns.TypeAAAA:
		m.Answer = make([]dns.RR, 1)
		m.Answer[0] = &dns.AAAA{Hdr: header, AAAA: net.ParseIP(resp.Value())}
	case dns.TypeSRV:
		var records []SrvRecord
		err := json.Unmarshal([]byte(resp.Value()), &records)
		if err != nil {
			log.Printf("Could not unmarshal SRV record from etcd: %s", resp.Value())
		} else {
			m.Answer = make([]dns.RR, len(records))
			for i := range records {
				m.Answer[i] = &dns.SRV{
					Hdr:      header,
					Priority: records[i].Priority,
					Weight:   records[i].Weight,
					Port:     records[i].Port,
					Target:   records[i].Target,
				}
			}
		}
	case dns.TypePTR:
		m.Answer = make([]dns.RR, 1)
		m.Answer[0] = &dns.PTR{Hdr: header, Ptr: resp.Value()}
	case dns.TypeCNAME:
		m.Answer = make([]dns.RR, 1)
		m.Answer[0] = &dns.CNAME{Hdr: header, Target: resp.Value()}
	default:
		log.Printf("Unrecognised record type: %d", qType)
	}

	w.WriteMsg(m)
}

func (s *DNSServer) handleReverseRequest(w dns.ResponseWriter, r *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(r)

	// Send empty response for empty requests
	if len(r.Question) == 0 {
		m.Ns = s.createSOA()
		w.WriteMsg(m)
		return
	}

	m.Answer = make([]dns.RR, 0, 2)
	query := r.Question[0].Name

	// trim off any trailing dot
	if query[len(query)-1] == '.' {
		query = query[:len(query)-1]
	}

	for service := range s.queryIp(query) {
		if r.Question[0].Qtype != dns.TypePTR {
			m.Ns = s.createSOA()
			w.WriteMsg(m)
			return
		}

		var ttl int
		if service.Ttl != -1 {
			ttl = service.Ttl
		} else {
			ttl = s.config.ttl
		}

		for domain := range s.listDomains(service) {
			rr := new(dns.PTR)
			rr.Hdr = dns.RR_Header{
				Name:   r.Question[0].Name,
				Rrtype: dns.TypePTR,
				Class:  dns.ClassINET,
				Ttl:    uint32(ttl),
			}
			rr.Ptr = domain

			m.Answer = append(m.Answer, rr)
		}
	}

	if len(m.Answer) != 0 {
		w.WriteMsg(m)
	} else {
		// We didn't find a record corresponding to the query,
		// try forwarding
		s.handleForward(w, r)
	}
}

func (s *DNSServer) handleRequest(w dns.ResponseWriter, r *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(r)

	// Send empty response for empty requests
	if len(r.Question) == 0 {
		m.Ns = s.createSOA()
		w.WriteMsg(m)
		return
	}

	// respond to SOA requests
	if r.Question[0].Qtype == dns.TypeSOA {
		m.Answer = s.createSOA()
		w.WriteMsg(m)
		return
	}

	m.Answer = make([]dns.RR, 0, 2)
	query := r.Question[0].Name

	// trim off any trailing dot
	if query[len(query)-1] == '.' {
		query = query[:len(query)-1]
	}

	for service := range s.queryServices(query) {
		var rr dns.RR
		switch r.Question[0].Qtype {
		case dns.TypeA:
			rr = s.makeServiceA(r.Question[0].Name, service)
		case dns.TypeMX:
			rr = s.makeServiceMX(r.Question[0].Name, service)
		default:
			// this query type isn't supported, but we do have
			// a record with this name. Per RFC 4074 sec. 3, we
			// immediately return an empty NOERROR reply.
			m.Ns = s.createSOA()
			m.MsgHdr.Authoritative = true
			w.WriteMsg(m)
			return
		}

		m.Answer = append(m.Answer, rr)
	}

	// We didn't find a record corresponding to the query
	if len(m.Answer) == 0 {
		m.Ns = s.createSOA()
		m.SetRcode(r, dns.RcodeNameError) // NXDOMAIN
	}

	w.WriteMsg(m)
}

func (z *zone) zoneHandler(c *config, w dns.ResponseWriter, req *dns.Msg) {
	c.stats.Incr("query.request", 1)
	m := new(dns.Msg)
	m.SetReply(req)
	m.Authoritative = true
	m.Answer = []dns.RR{}
	questions := []string{}
	answers := []string{}
	if len(req.Question) != 1 {
		c.stats.Incr("query.error", 1)
		log.Printf("Warning: len(req.Question) != 1")
		return
	}
	q := req.Question[0]
	questions = append(questions, fmt.Sprintf("%s[%s]", q.Name, dns.TypeToString[q.Qtype]))
	if q.Qclass != uint16(dns.ClassINET) {
		c.stats.Incr("query.error", 1)
		log.Printf("Warning: skipping unhandled class: %s", dns.ClassToString[q.Qclass])
		return
	}
	for _, record := range z.rrs {
		h := record.Header()
		if q.Name != h.Name {
			continue
		}
		txt := record.String()
		if q.Qtype == dns.TypeA && h.Rrtype == dns.TypeCNAME { // special handling for A queries w/CNAME results
			if q.Name == dns.Fqdn(z.name) { // flatten root CNAME
				flat, err := c.flattenCNAME(record.(*dns.CNAME))
				if err != nil || flat == nil {
					log.Printf("flattenCNAME error: %s", err.Error())
				} else {
					for _, record := range flat {
						m.Answer = append(m.Answer, record)
						answers = append(answers, "(FLAT)"+record.String())
					}
				}
				continue
			} // don't flatten other CNAMEs for now
		} else if q.Qtype != h.Rrtype && q.Qtype != dns.TypeANY { // skip RRs that don't match
			continue
		}
		m.Answer = append(m.Answer, record)
		answers = append(answers, txt)
	}
	//m.Extra = []dns.RR{}
	//m.Extra = append(m.Extra, &dns.TXT{Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{"DNS rocks"}})
	c.debug(fmt.Sprintf("Query [%s] %s -> %s ", w.RemoteAddr().String(), strings.Join(questions, ","), strings.Join(answers, ",")))
	c.stats.Incr("query.answer", 1)

	w.WriteMsg(m)
}

func (c *config) registerVersionHandler() { // special handler for reporting version: dig . @host TXT
	dns.HandleFunc(".", func(w dns.ResponseWriter, req *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(req)
		if req.Question[0].Name == "." && req.Question[0].Qtype == dns.TypeTXT {
			m.Authoritative = true
			m.Answer = []dns.RR{}
			m.Answer = append(m.Answer, &dns.TXT{Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{"v" + version}})
			m.Extra = []dns.RR{}
			m.Extra = append(m.Extra, &dns.TXT{Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{"NedDNS"}})
		}
		w.WriteMsg(m)
	})
}

func Respond(w dns.ResponseWriter, req *dns.Msg, records []dns.RR) {
	m := new(dns.Msg)
	m.SetReply(req)
	m.Authoritative = true
	m.RecursionAvailable = true
	m.Compress = true
	m.Answer = records

	// Figure out the max response size
	bufsize := uint16(512)
	tcp := isTcp(w)

	if o := req.IsEdns0(); o != nil {
		bufsize = o.UDPSize()
	}

	if tcp {
		bufsize = dns.MaxMsgSize - 1
	} else if bufsize < 512 {
		bufsize = 512
	}

	if m.Len() > dns.MaxMsgSize {
		fqdn := dns.Fqdn(req.Question[0].Name)
		log.WithFields(log.Fields{"fqdn": fqdn}).Debug("Response too big, dropping Extra")
		m.Extra = nil
		if m.Len() > dns.MaxMsgSize {
			log.WithFields(log.Fields{"fqdn": fqdn}).Debug("Response still too big")
			m := new(dns.Msg)
			m.SetRcode(m, dns.RcodeServerFailure)
		}
	}

	if m.Len() > int(bufsize) && !tcp {
		log.Debug("Too big 1")
		m.Extra = nil
		if m.Len() > int(bufsize) {
			log.Debug("Too big 2")
			m.Answer = nil
			m.Truncated = true
		}
	}

	err := w.WriteMsg(m)
	if err != nil {
		log.Warn("Failed to return reply: ", err, m.Len())
	}

}