func (s *server) PTRRecords(q dns.Question) (records []dns.RR, err error) {
	name := strings.ToLower(q.Name)
	path, star := msg.PathWithWildcard(name)
	if star {
		return nil, fmt.Errorf("reverse can not contain wildcards")
	}
	r, err := get(s.client, path, false)
	if err != nil {
		// if server has a forward, forward the query
		return nil, err
	}
	if r.Node.Dir {
		return nil, fmt.Errorf("reverse should not be a directory")
	}
	serv := new(msg.Service)
	if err := json.Unmarshal([]byte(r.Node.Value), serv); err != nil {
		s.config.log.Infof("failed to parse json: %s", err.Error())
		return nil, err
	}
	ttl := uint32(r.Node.TTL)
	if ttl == 0 {
		ttl = s.config.Ttl
	}
	serv.Key = r.Node.Key
	// If serv.Host is parseble as a IP address we should not return anything.
	// TODO(miek).
	records = append(records, serv.NewPTR(q.Name, ttl))
	return records, nil
}

func (g *Backend) Records(name string, exact bool) ([]msg.Service, error) {
	path, star := msg.PathWithWildcard(name)
	bits := strings.Split(path, "/")
	fmt.Println(bits, path, star)
	srv := msg.Service{}
	srv.Host = "192.168.5.1"
	l := make([]msg.Service, 0)
	l = append(l, srv)
	return l, nil // errors.New("FAIL")
}

// Handle API add service requests
func (s *Server) addServiceHTTPHandler(w http.ResponseWriter, req *http.Request) {
	addServiceCount.Inc(1)
	vars := mux.Vars(req)

	var uuid string
	var ok bool
	var secret string

	//read the authorization header to get the secret.
	secret = req.Header.Get("Authorization")

	if err := s.authenticate(secret); err != nil {
		http.Error(w, err.Error(), http.StatusForbidden)
		return
	}

	if uuid, ok = vars["uuid"]; !ok {
		http.Error(w, "UUID required", http.StatusBadRequest)
		return
	}

	var serv msg.Service

	if err := json.NewDecoder(req.Body).Decode(&serv); err != nil {
		log.Println("Error: ", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	if serv.Host == "" || serv.Port == 0 {
		http.Error(w, "Host and Port required", http.StatusBadRequest)
		return
	}

	serv.UUID = uuid

	if _, err := s.raftServer.Do(NewAddServiceCommand(serv)); err != nil {
		switch err {
		case registry.ErrExists:
			http.Error(w, err.Error(), http.StatusConflict)
		case raft.NotLeaderError:
			s.redirectToLeader(w, req)
		default:
			log.Println("Error: ", err)
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}

		return
	}

	w.WriteHeader(http.StatusCreated)
}

func (g *Backend) decode(n *etcd.Node) (*msg.Service, error) {
	serv := new(msg.Service)
	if err := json.Unmarshal([]byte(n.Value), serv); err != nil {
		return nil, err
	}

	serv.Key = n.Key
	serv.Ttl = g.calculateTtl(n, serv)
	if serv.Priority == 0 {
		serv.Priority = int(g.config.Priority)
	}

	return serv, nil
}

// loopNodes recursively loops through the nodes and returns all the values. The nodes' keyname
// will be match against any wildcards when star is true.
func (g *Backend) loopNodes(ns []*etcd.Node, nameParts []string, star bool, bx map[bareService]bool) (sx []msg.Service, err error) {
	if bx == nil {
		bx = make(map[bareService]bool)
	}
Nodes:
	for _, n := range ns {
		if n.Dir {
			nodes, err := g.loopNodes(n.Nodes, nameParts, star, bx)
			if err != nil {
				return nil, err
			}
			sx = append(sx, nodes...)
			continue
		}
		if star {
			keyParts := strings.Split(n.Key, "/")
			for i, n := range nameParts {
				if i > len(keyParts)-1 {
					// name is longer than key
					continue Nodes
				}
				if n == "*" || n == "any" {
					continue
				}
				if keyParts[i] != n {
					continue Nodes
				}
			}
		}
		serv := new(msg.Service)
		if err := json.Unmarshal([]byte(n.Value), serv); err != nil {
			return nil, err
		}
		b := bareService{serv.Host, serv.Port, serv.Priority, serv.Weight, serv.Text}
		if _, ok := bx[b]; ok {
			continue
		}
		bx[b] = true

		serv.Key = n.Key
		serv.Ttl = g.calculateTtl(n, serv)
		if serv.Priority == 0 {
			serv.Priority = int(g.config.Priority)
		}
		sx = append(sx, *serv)
	}
	return sx, nil
}

func (g *Backendv3) loopNodes(kv []*mvccpb.KeyValue, nameParts []string, star bool, bx map[bareService]bool) (sx []msg.Service, err error) {
	if bx == nil {
		bx = make(map[bareService]bool)
	}
Nodes:
	for _, item := range kv {

		if star {
			s := string(item.Key[:])
			keyParts := strings.Split(s, "/")
			for i, n := range nameParts {
				if i > len(keyParts)-1 {
					continue Nodes
				}
				if n == "*" || n == "any" {
					continue
				}
				if keyParts[i] != n {
					continue Nodes
				}
			}
		}

		serv := new(msg.Service)
		if err := json.Unmarshal(item.Value, serv); err != nil {
			return nil, err
		}

		b := bareService{serv.Host,
			serv.Port,
			serv.Priority,
			serv.Weight,
			serv.Text}

		bx[b] = true
		serv.Key = string(item.Key)
		//TODO: another call (LeaseRequest) for TTL when RPC in etcdv3 is ready
		serv.Ttl = g.calculateTtl(item, serv)

		if serv.Priority == 0 {
			serv.Priority = int(g.config.Priority)
		}

		sx = append(sx, *serv)
	}
	return sx, nil
}

func writeService(c *cli.Context, service *msg.Service) {
	if c.GlobalBool("json") {
		if err := json.NewEncoder(os.Stdout).Encode(service); err != nil {
			writeError(err)
		}
	} else {
		fmt.Printf("UUID: %s\nName: %s\nHost: %s\nPort: %d\nEnvironment: %s\nRegion: %s\nVersion: %s\n\n",
			service.UUID,
			service.Name,
			service.Host,
			service.Port,
			service.Environment,
			service.Region,
			service.Version)

		fmt.Printf("TTL %d\nRemaining TTL: %d\n",
			service.TTL,
			service.RemainingTTL())
	}
}

func TestGetService(t *testing.T) {
	s := newTestServer("", 9570, 9571, "")
	defer s.Stop()

	m := msg.Service{
		UUID:        "123",
		Name:        "TestService",
		Version:     "1.0.0",
		Region:      "Test",
		Host:        "localhost",
		Environment: "Production",
		Port:        9000,
		TTL:         4,
		Expires:     getExpirationTime(4),
	}

	s.registry.Add(m)

	req, _ := http.NewRequest("GET", "/skydns/services/"+m.UUID, nil)
	resp := httptest.NewRecorder()

	s.router.ServeHTTP(resp, req)

	if resp.Code != http.StatusOK {
		t.Fatal("Failed to retrieve service")
	}

	m.TTL = 3 // TTL will be lower as time has passed
	expected, err := json.Marshal(m)

	if err != nil {
		t.Fatal(err)
	}

	// Newline is expected
	expected = append(expected, []byte("\n")...)

	if !bytes.Equal(resp.Body.Bytes(), expected) {
		t.Fatalf("Returned service is invalid. Expected %q but received %q", string(expected), resp.Body.String())
	}
}

func (s *server) CNAMERecords(q dns.Question, name string) (records []dns.RR, err error) {
	path, _ := msg.PathWithWildcard(name) // no wildcards here
	r, err := get(s.client, path, true)
	if err != nil {
		return nil, err
	}
	if !r.Node.Dir {
		serv := new(msg.Service)
		if err := json.Unmarshal([]byte(r.Node.Value), serv); err != nil {
			s.config.log.Infof("failed to parse json: %s", err.Error())
			return nil, err
		}
		ip := net.ParseIP(serv.Host)
		ttl := s.calculateTtl(r.Node, serv)
		serv.Key = r.Node.Key
		serv.Ttl = ttl
		if ip == nil {
			records = append(records, serv.NewCNAME(q.Name, dns.Fqdn(serv.Host)))
		}
	}
	return records, nil
}

func TestUpdateTTL(t *testing.T) {
	s := newTestServer("", 9540, 9541, "")
	defer s.Stop()

	m := msg.Service{
		UUID:        "123",
		Name:        "TestService",
		Version:     "1.0.0",
		Region:      "Test",
		Host:        "localhost",
		Environment: "Production",
		Port:        9000,
		TTL:         4,
	}

	s.registry.Add(m)

	m.TTL = 25
	b, err := json.Marshal(m)

	if err != nil {
		t.Fatal(err)
	}

	req, _ := http.NewRequest("PATCH", "/skydns/services/"+m.UUID, bytes.NewBuffer(b))
	resp := httptest.NewRecorder()

	s.router.ServeHTTP(resp, req)

	if resp.Code != http.StatusOK {
		t.Fatal("Failed to update TTL")
	}

	if serv, err := s.registry.GetUUID(m.UUID); err != nil || serv.TTL != 24 {
		t.Fatal("Failed to update TTL", err, serv.TTL)
	}
}

// setEntry creates the entire path if it doesn't already exist in the cache,
// then sets the given service record under the given key. The path this entry
// would have occupied in an etcd datastore is computed from the given fqdn and
// stored as the "Key" of the skydns service; this is only required because
// skydns expects the service record to contain a key in a specific format
// (presumably for legacy compatibility). Note that the fqnd string typically
// contains both the key and all elements in the path.
func (cache *TreeCache) setEntry(key string, val *skymsg.Service, fqdn string, path ...string) {
	// TODO: Consolidate setEntry and setSubCache into a single method with a
	// type switch.
	// TODO: Insted of passing the fqdn as an argument, we can reconstruct
	// it from the path, provided callers always pass the full path to the
	// object. This is currently *not* the case, since callers first create
	// a new, empty node, populate it, then parent it under the right path.
	// So we don't know the full key till the final parenting operation.
	node := cache.ensureChildNode(path...)

	// This key is used to construct the "target" for SRV record lookups.
	// For normal service/endpoint lookups, this will result in a key like:
	// /skydns/local/cluster/svc/svcNS/svcName/record-hash
	// but for headless services that govern pods requesting a specific
	// hostname (as used by petset), this will end up being:
	// /skydns/local/cluster/svc/svcNS/svcName/pod-hostname
	val.Key = skymsg.Path(fqdn)
	node.Entries[key] = val
}

// SRVRecords returns SRV records from etcd.
// If the Target is not an name but an IP address, an name is created .
func (s *server) SRVRecords(q dns.Question, name string, bufsize uint16, dnssec bool) (records []dns.RR, extra []dns.RR, err error) {
	path, star := msg.PathWithWildcard(name)
	r, err := get(s.client, path, true)
	if err != nil {
		return nil, nil, err
	}
	if !r.Node.Dir { // single element
		serv := new(msg.Service)
		if err := json.Unmarshal([]byte(r.Node.Value), serv); err != nil {
			s.config.log.Infof("failed to parse json: %s", err.Error())
			return nil, nil, err
		}
		ip := net.ParseIP(serv.Host)
		ttl := s.calculateTtl(r.Node, serv)
		if serv.Priority == 0 {
			serv.Priority = int(s.config.Priority)
		}
		serv.Key = r.Node.Key
		serv.Ttl = ttl
		switch {
		case ip == nil:
			srv := serv.NewSRV(q.Name, uint16(100))
			records = append(records, srv)
			if !dns.IsSubDomain(s.config.Domain, srv.Target) {
				m1, e1 := s.Lookup(srv.Target, dns.TypeA, bufsize, dnssec)
				if e1 == nil {
					extra = append(extra, m1.Answer...)
				}
				m1, e1 = s.Lookup(srv.Target, dns.TypeAAAA, bufsize, dnssec)
				if e1 == nil {
					// If we have seen CNAME's we *assume* that they already added.
					for _, a := range m1.Answer {
						if _, ok := a.(*dns.CNAME); !ok {
							extra = append(extra, a)
						}
					}
				}
			}
		case ip.To4() != nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewSRV(q.Name, uint16(100)))
			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
		case ip.To4() == nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewSRV(q.Name, uint16(100)))
			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
		}
		return records, extra, nil
	}

	sx, err := s.loopNodes(&r.Node.Nodes, strings.Split(msg.Path(name), "/"), star, nil)
	if err != nil || len(sx) == 0 {
		return nil, nil, err
	}
	// Looping twice to get the right weight vs priority
	w := make(map[int]int)
	for _, serv := range sx {
		weight := 100
		if serv.Weight != 0 {
			weight = serv.Weight
		}
		if _, ok := w[serv.Priority]; !ok {
			w[serv.Priority] = weight
			continue
		}
		w[serv.Priority] += weight
	}
	lookup := make(map[string]bool)
	for _, serv := range sx {
		w1 := 100.0 / float64(w[serv.Priority])
		if serv.Weight == 0 {
			w1 *= 100
		} else {
			w1 *= float64(serv.Weight)
		}
		weight := uint16(math.Floor(w1))
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			srv := serv.NewSRV(q.Name, weight)
			records = append(records, srv)
			if _, ok := lookup[srv.Target]; !ok {
				if !dns.IsSubDomain(s.config.Domain, srv.Target) {
					m1, e1 := s.Lookup(srv.Target, dns.TypeA, bufsize, dnssec)
					if e1 == nil {
						extra = append(extra, m1.Answer...)
					}
					m1, e1 = s.Lookup(srv.Target, dns.TypeAAAA, bufsize, dnssec)
					if e1 == nil {
						// If we have seen CNAME's we *assume* that they are already added.
						for _, a := range m1.Answer {
							if _, ok := a.(*dns.CNAME); !ok {
								extra = append(extra, a)
							}
						}
					}
				}
			}
//.........这里部分代码省略.........

// Records implements the SkyDNS Backend interface and returns standard records for
// a name.
//
// The standard pattern is <prefix>.<service_name>.<namespace>.(svc|endpoints|pod).<base>
//
// * prefix may be any series of prefix values
//   * _endpoints is a special prefix that returns the same as <service_name>.<namespace>.svc.<base>
// * service_name and namespace must locate a real service
//   * unless a fallback is defined, in which case the fallback name will be looked up
// * svc indicates standard service rules apply (clusterIP or endpoints as A records)
//   * reverse lookup of IP is only possible for clusterIP
//   * SRV records are returned for each host+port combination as:
//     _<port_name>._<port_protocol>.<dns>
//     _<port_name>.<endpoint_id>.<dns>
// * endpoints always returns each individual endpoint as A records
//   * SRV records for endpoints are similar to SVC, but are prefixed with a single label
//     that is a hash of the endpoint IP
// * pods is of the form <IP_with_dashes>.<namespace>.pod.<base> and resolves to <IP>
//
func (b *ServiceResolver) Records(dnsName string, exact bool) ([]msg.Service, error) {
	if !strings.HasSuffix(dnsName, b.base) {
		return nil, errNoSuchName
	}
	prefix := strings.Trim(strings.TrimSuffix(dnsName, b.base), ".")
	segments := strings.Split(prefix, ".")
	for i, j := 0, len(segments)-1; i < j; i, j = i+1, j-1 {
		segments[i], segments[j] = segments[j], segments[i]
	}
	if len(segments) == 0 {
		return nil, errNoSuchName
	}
	glog.V(4).Infof("Answering query %s:%t", dnsName, exact)
	switch base := segments[0]; base {
	case "pod":
		if len(segments) != 3 {
			return nil, errNoSuchName
		}
		namespace, encodedIP := segments[1], segments[2]
		ip := convertDashIPToIP(encodedIP)
		if net.ParseIP(ip) == nil {
			return nil, errNoSuchName
		}
		return []msg.Service{
			{
				Host: ip,
				Port: 0,

				Priority: 10,
				Weight:   10,
				Ttl:      30,

				Key: msg.Path(buildDNSName(b.base, "pod", namespace, getHash(ip))),
			},
		}, nil

	case "svc", "endpoints":
		if len(segments) < 3 {
			return nil, errNoSuchName
		}
		namespace, name := segments[1], segments[2]
		svc, err := b.accessor.Services(namespace).Get(name)
		if err != nil {
			if errors.IsNotFound(err) && b.fallback != nil {
				if fallback, ok := b.fallback(prefix, exact); ok {
					return b.Records(fallback+b.base, exact)
				}
				return nil, errNoSuchName
			}
			return nil, errNoSuchName
		}

		// no clusterIP and not headless, no DNS
		if len(svc.Spec.ClusterIP) == 0 && svc.Spec.Type != kapi.ServiceTypeExternalName {
			return nil, errNoSuchName
		}

		subdomain := buildDNSName(b.base, base, namespace, name)
		endpointPrefix := base == "endpoints"
		retrieveEndpoints := endpointPrefix || (len(segments) > 3 && segments[3] == "_endpoints")

		includePorts := len(segments) > 3 && hasAllPrefixedSegments(segments[3:], "_") && segments[3] != "_endpoints"

		// if has a portal IP and looking at svc
		if svc.Spec.ClusterIP != kapi.ClusterIPNone && !retrieveEndpoints {
			hostValue := svc.Spec.ClusterIP
			if svc.Spec.Type == kapi.ServiceTypeExternalName {
				hostValue = svc.Spec.ExternalName
			}

			defaultService := msg.Service{
				Host: hostValue,
				Port: 0,

				Priority: 10,
				Weight:   10,
				Ttl:      30,
			}
			defaultHash := getHash(defaultService.Host)
			defaultName := buildDNSName(subdomain, defaultHash)
			defaultService.Key = msg.Path(defaultName)
//.........这里部分代码省略.........

// Creates a new AddServiceCommand
func NewAddServiceCommand(s msg.Service) *AddServiceCommand {
	s.Expires = getExpirationTime(s.TTL)

	return &AddServiceCommand{s}
}

// Records implements the SkyDNS Backend interface and returns standard records for
// a name.
//
// The standard pattern is <prefix>.<service_name>.<namespace>.(svc|endpoints|pod).<base>
//
// * prefix may be any series of prefix values
//   * _endpoints is a special prefix that returns the same as <service_name>.<namespace>.svc.<base>
// * service_name and namespace must locate a real service
//   * unless a fallback is defined, in which case the fallback name will be looked up
// * svc indicates standard service rules apply (portalIP or endpoints as A records)
//   * reverse lookup of IP is only possible for portalIP
//   * SRV records are returned for each host+port combination as:
//     _<port_name>._<port_protocol>.<dns>
//     _<port_name>.<endpoint_id>.<dns>
// * endpoints always returns each individual endpoint as A records
//   * SRV records for endpoints are similar to SVC, but are prefixed with a single label
//     that is a hash of the endpoint IP
// * pods is of the form <IP_with_dashes>.<namespace>.pod.<base> and resolves to <IP>
//
func (b *ServiceResolver) Records(dnsName string, exact bool) ([]msg.Service, error) {
	if !strings.HasSuffix(dnsName, b.base) {
		return nil, nil
	}
	prefix := strings.Trim(strings.TrimSuffix(dnsName, b.base), ".")
	segments := strings.Split(prefix, ".")
	for i, j := 0, len(segments)-1; i < j; i, j = i+1, j-1 {
		segments[i], segments[j] = segments[j], segments[i]
	}
	if len(segments) == 0 {
		return nil, nil
	}
	glog.V(4).Infof("Answering query %s:%t", dnsName, exact)
	switch base := segments[0]; base {
	case "pod":
		if len(segments) != 3 {
			return nil, nil
		}
		namespace, encodedIP := segments[1], segments[2]
		ip := convertDashIPToIP(encodedIP)
		if net.ParseIP(ip) == nil {
			return nil, nil
		}
		return []msg.Service{
			{
				Host: ip,
				Port: 0,

				Priority: 10,
				Weight:   10,
				Ttl:      30,

				Key: msg.Path(buildDNSName(b.base, "pod", namespace, getHash(ip))),
			},
		}, nil

	case "svc", "endpoints":
		if len(segments) < 3 {
			return nil, nil
		}
		namespace, name := segments[1], segments[2]
		svc, err := b.accessor.Services(namespace).Get(name)
		if err != nil {
			if errors.IsNotFound(err) && b.fallback != nil {
				if fallback, ok := b.fallback(prefix, exact); ok {
					return b.Records(fallback+b.base, exact)
				}
			}
			return nil, err
		}

		// no portalIP and not headless, no DNS
		if len(svc.Spec.ClusterIP) == 0 {
			return nil, nil
		}

		subdomain := buildDNSName(b.base, base, namespace, name)
		endpointPrefix := base == "endpoints"
		retrieveEndpoints := endpointPrefix || (len(segments) > 3 && segments[3] == "_endpoints")

		// if has a portal IP and looking at svc
		if svc.Spec.ClusterIP != kapi.ClusterIPNone && !retrieveEndpoints {
			defaultService := msg.Service{
				Host: svc.Spec.ClusterIP,
				Port: 0,

				Priority: 10,
				Weight:   10,
				Ttl:      30,
			}
			defaultHash := getHash(defaultService.Host)
			defaultName := buildDNSName(subdomain, defaultHash)
			defaultService.Key = msg.Path(defaultName)

			if len(svc.Spec.Ports) == 0 {
				return []msg.Service{defaultService}, nil
			}

			services := []msg.Service{}
			if len(segments) == 3 {
				for _, p := range svc.Spec.Ports {
//.........这里部分代码省略.........

// NSRecords returns NS records from etcd.
func (s *server) NSRecords(q dns.Question, name string) (records []dns.RR, extra []dns.RR, err error) {
	path, star := msg.PathWithWildcard(name)
	r, err := get(s.client, path, true)
	if err != nil {
		return nil, nil, err
	}
	if !r.Node.Dir { // single element
		serv := new(msg.Service)
		if err := json.Unmarshal([]byte(r.Node.Value), serv); err != nil {
			s.config.log.Infof("failed to parse json: %s", err.Error())
			return nil, nil, err
		}
		ip := net.ParseIP(serv.Host)
		ttl := s.calculateTtl(r.Node, serv)
		serv.Key = r.Node.Key
		serv.Ttl = ttl
		switch {
		case ip == nil:
			return nil, nil, fmt.Errorf("NS record must be an IP address")
		case ip.To4() != nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(q.Name, serv.Host))
			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
		case ip.To4() == nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(q.Name, serv.Host))
			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
		}
		return records, extra, nil
	}

	sx, err := s.loopNodes(&r.Node.Nodes, strings.Split(msg.Path(name), "/"), star, nil)
	if err != nil || len(sx) == 0 {
		return nil, nil, err
	}
	for _, serv := range sx {
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			return nil, nil, fmt.Errorf("NS record must be an IP address")
		case ip.To4() != nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(q.Name, serv.Host))
			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
		case ip.To4() == nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(q.Name, serv.Host))
			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
		}
	}
	return records, extra, nil
}

func (s *server) AddressRecords(q dns.Question, name string, previousRecords []dns.RR) (records []dns.RR, err error) {
	path, star := msg.PathWithWildcard(name)
	r, err := get(s.client, path, true)
	if err != nil {
		return nil, err
	}
	if !r.Node.Dir { // single element
		serv := new(msg.Service)
		if err := json.Unmarshal([]byte(r.Node.Value), serv); err != nil {
			s.config.log.Infof("failed to parse json: %s", err.Error())
			return nil, err
		}
		ip := net.ParseIP(serv.Host)
		ttl := s.calculateTtl(r.Node, serv)
		serv.Ttl = ttl
		serv.Key = r.Node.Key
		switch {
		case ip == nil:
			// Try to resolve as CNAME if it's not an IP.
			newRecord := serv.NewCNAME(q.Name, dns.Fqdn(serv.Host))
			if len(previousRecords) > 7 {
				s.config.log.Errorf("CNAME lookup limit of 8 exceeded for %s", newRecord)
				return nil, fmt.Errorf("exceeded CNAME lookup limit")
			}
			if s.isDuplicateCNAME(newRecord, previousRecords) {
				s.config.log.Errorf("CNAME loop detected for record %s", newRecord)
				return nil, fmt.Errorf("detected CNAME loop")
			}

			records = append(records, newRecord)
			nextRecords, err := s.AddressRecords(dns.Question{Name: dns.Fqdn(serv.Host), Qtype: q.Qtype, Qclass: q.Qclass}, strings.ToLower(dns.Fqdn(serv.Host)), append(previousRecords, newRecord))
			if err != nil {
				// This means we can not complete the CNAME, this is OK, but
				// if we return an error this will trigger an NXDOMAIN.
				// We also don't want to return the CNAME, because of the
				// no other data rule. So return nothing and let NODATA
				// kick in (via a hack).
				return records, fmt.Errorf("incomplete CNAME chain")
			}
			records = append(records, nextRecords...)
		case ip.To4() != nil && q.Qtype == dns.TypeA:
			records = append(records, serv.NewA(q.Name, ip.To4()))
		case ip.To4() == nil && q.Qtype == dns.TypeAAAA:
			records = append(records, serv.NewAAAA(q.Name, ip.To16()))
		}
		return records, nil
	}
	nodes, err := s.loopNodes(&r.Node.Nodes, strings.Split(msg.Path(name), "/"), star, nil)
	if err != nil {
		s.config.log.Infof("failed to parse json: %s", err.Error())
		return nil, err
	}
	for _, serv := range nodes {
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			// TODO: deduplicate with above code
			// Try to resolve as CNAME if it's not an IP.
			newRecord := serv.NewCNAME(q.Name, dns.Fqdn(serv.Host))
			if len(previousRecords) > 7 {
				s.config.log.Errorf("CNAME lookup limit of 8 exceeded for %s", newRecord)
				return nil, fmt.Errorf("exceeded CNAME lookup limit")
			}
			if s.isDuplicateCNAME(newRecord, previousRecords) {
				s.config.log.Errorf("CNAME loop detected for record %s", newRecord)
				return nil, fmt.Errorf("detected CNAME loop")
			}

			records = append(records, newRecord)
			nextRecords, err := s.AddressRecords(dns.Question{Name: dns.Fqdn(serv.Host), Qtype: q.Qtype, Qclass: q.Qclass}, strings.ToLower(dns.Fqdn(serv.Host)), append(previousRecords, newRecord))
			if err != nil {
				// This means we can not complete the CNAME, this is OK, but
				// if we return an error this will trigger an NXDOMAIN.
				// We also don't want to return the CNAME, because of the
				// no other data rule. So return nothing and let NODATA
				// kick in (via a hack).
				return records, fmt.Errorf("incomplete CNAME chain")
			}
			records = append(records, nextRecords...)
		case ip.To4() != nil && q.Qtype == dns.TypeA:
			records = append(records, serv.NewA(q.Name, ip.To4()))
		case ip.To4() == nil && q.Qtype == dns.TypeAAAA:
			records = append(records, serv.NewAAAA(q.Name, ip.To16()))
		}
	}
	if s.config.RoundRobin {
		switch l := len(records); l {
		case 2:
			if dns.Id()%2 == 0 {
				records[0], records[1] = records[1], records[0]
			}
		default:
			// Do a minimum of l swap, maximum of 4l swaps
			for j := 0; j < l*(int(dns.Id())%4+1); j++ {
				q := int(dns.Id()) % l
				p := int(dns.Id()) % l
				if q == p {
					p = (p + 1) % l
				}
				records[q], records[p] = records[p], records[q]
//.........这里部分代码省略.........