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Feature/dns-server (#537)
Adding DNS server for client Updated the API with new fields Added custom zone object for peer's DNS resolution
This commit is contained in:
Maycon Santos
GitHub
270
client/internal/dns/server.go
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270
client/internal/dns/server.go
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@ -0,0 +1,270 @@
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package dns
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import (
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"context"
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"fmt"
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"github.com/miekg/dns"
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nbdns "github.com/netbirdio/netbird/dns"
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log "github.com/sirupsen/logrus"
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"sync"
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"time"
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)
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const (
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port = 5053
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defaultIP = "0.0.0.0"
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)
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// Server dns server object
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type Server struct {
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ctx context.Context
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stop context.CancelFunc
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mux sync.Mutex
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server *dns.Server
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dnsMux *dns.ServeMux
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dnsMuxMap registrationMap
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localResolver *localResolver
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updateSerial uint64
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listenerIsRunning bool
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}
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type registrationMap map[string]struct{}
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type muxUpdate struct {
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domain string
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handler dns.Handler
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}
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// NewServer returns a new dns server
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func NewServer(ctx context.Context) *Server {
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mux := dns.NewServeMux()
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dnsServer := &dns.Server{
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Addr: fmt.Sprintf("%s:%d", defaultIP, port),
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Net: "udp",
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Handler: mux,
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UDPSize: 65535,
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}
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ctx, stop := context.WithCancel(ctx)
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return &Server{
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ctx: ctx,
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stop: stop,
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server: dnsServer,
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dnsMux: mux,
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dnsMuxMap: make(registrationMap),
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localResolver: &localResolver{
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registeredMap: make(registrationMap),
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},
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}
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}
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// Start runs the listener in a go routine
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func (s *Server) Start() {
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log.Debugf("starting dns on %s:%d", defaultIP, port)
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go func() {
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s.setListenerStatus(true)
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defer s.setListenerStatus(false)
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err := s.server.ListenAndServe()
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if err != nil {
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log.Errorf("dns server returned an error: %v", err)
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}
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}()
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}
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func (s *Server) setListenerStatus(running bool) {
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s.listenerIsRunning = running
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}
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// Stop stops the server
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func (s *Server) Stop() {
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s.stop()
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err := s.stopListener()
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if err != nil {
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log.Error(err)
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}
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}
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func (s *Server) stopListener() error {
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if !s.listenerIsRunning {
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return nil
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}
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ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
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defer cancel()
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err := s.server.ShutdownContext(ctx)
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if err != nil {
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return fmt.Errorf("stopping dns server listener returned an error: %v", err)
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}
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return nil
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}
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// UpdateDNSServer processes an update received from the management service
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func (s *Server) UpdateDNSServer(serial uint64, update nbdns.Update) error {
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select {
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case <-s.ctx.Done():
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log.Infof("not updating DNS server as context is closed")
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return s.ctx.Err()
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default:
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if serial < s.updateSerial {
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return fmt.Errorf("not applying dns update, error: "+
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"network update is %d behind the last applied update", s.updateSerial-serial)
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}
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s.mux.Lock()
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defer s.mux.Unlock()
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// is the service should be disabled, we stop the listener
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// and proceed with a regular update to clean up the handlers and records
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if !update.ServiceEnable {
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err := s.stopListener()
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if err != nil {
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log.Error(err)
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}
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} else if !s.listenerIsRunning {
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s.Start()
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}
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localMuxUpdates, localRecords, err := s.buildLocalHandlerUpdate(update.CustomZones)
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if err != nil {
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return fmt.Errorf("not applying dns update, error: %v", err)
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}
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upstreamMuxUpdates, err := s.buildUpstreamHandlerUpdate(update.NameServerGroups)
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if err != nil {
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return fmt.Errorf("not applying dns update, error: %v", err)
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}
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muxUpdates := append(localMuxUpdates, upstreamMuxUpdates...)
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s.updateMux(muxUpdates)
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s.updateLocalResolver(localRecords)
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s.updateSerial = serial
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return nil
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}
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}
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func (s *Server) buildLocalHandlerUpdate(customZones []nbdns.CustomZone) ([]muxUpdate, map[string]nbdns.SimpleRecord, error) {
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var muxUpdates []muxUpdate
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localRecords := make(map[string]nbdns.SimpleRecord, 0)
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for _, customZone := range customZones {
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if len(customZone.Records) == 0 {
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return nil, nil, fmt.Errorf("received an empty list of records")
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}
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muxUpdates = append(muxUpdates, muxUpdate{
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domain: customZone.Domain,
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handler: s.localResolver,
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})
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for _, record := range customZone.Records {
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localRecords[record.Name] = record
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}
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}
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return muxUpdates, localRecords, nil
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}
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func (s *Server) buildUpstreamHandlerUpdate(nameServerGroups []nbdns.NameServerGroup) ([]muxUpdate, error) {
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var muxUpdates []muxUpdate
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for _, nsGroup := range nameServerGroups {
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if len(nsGroup.NameServers) == 0 {
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return nil, fmt.Errorf("received a nameserver group with empty nameserver list")
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}
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handler := &upstreamResolver{
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parentCTX: s.ctx,
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upstreamClient: &dns.Client{},
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upstreamTimeout: defaultUpstreamTimeout,
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}
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for _, ns := range nsGroup.NameServers {
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if ns.NSType != nbdns.UDPNameServerType {
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log.Warnf("skiping nameserver %s with type %s, this peer supports only %s",
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ns.IP.String(), ns.NSType.String(), nbdns.UDPNameServerType.String())
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continue
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}
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handler.upstreamServers = append(handler.upstreamServers, getNSHostPort(ns))
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}
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if len(handler.upstreamServers) == 0 {
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log.Errorf("received a nameserver group with an invalid nameserver list")
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continue
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}
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if nsGroup.Primary {
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muxUpdates = append(muxUpdates, muxUpdate{
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domain: nbdns.RootZone,
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handler: handler,
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})
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continue
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}
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if len(nsGroup.Domains) == 0 {
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return nil, fmt.Errorf("received a non primary nameserver group with an empty domain list")
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}
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for _, domain := range nsGroup.Domains {
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if domain == "" {
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return nil, fmt.Errorf("received a nameserver group with an empty domain element")
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}
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muxUpdates = append(muxUpdates, muxUpdate{
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domain: domain,
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handler: handler,
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})
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}
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}
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return muxUpdates, nil
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}
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func (s *Server) updateMux(muxUpdates []muxUpdate) {
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muxUpdateMap := make(registrationMap)
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for _, update := range muxUpdates {
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s.registerMux(update.domain, update.handler)
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muxUpdateMap[update.domain] = struct{}{}
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}
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for key := range s.dnsMuxMap {
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_, found := muxUpdateMap[key]
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if !found {
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s.deregisterMux(key)
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}
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}
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s.dnsMuxMap = muxUpdateMap
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}
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func (s *Server) updateLocalResolver(update map[string]nbdns.SimpleRecord) {
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for key := range s.localResolver.registeredMap {
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_, found := update[key]
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if !found {
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s.localResolver.deleteRecord(key)
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}
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}
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updatedMap := make(registrationMap)
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for key, record := range update {
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err := s.localResolver.registerRecord(record)
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if err != nil {
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log.Warnf("got an error while registering the record (%s), error: %v", record.String(), err)
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}
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updatedMap[key] = struct{}{}
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}
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s.localResolver.registeredMap = updatedMap
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}
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func getNSHostPort(ns nbdns.NameServer) string {
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return fmt.Sprintf("%s:%d", ns.IP.String(), ns.Port)
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}
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func (s *Server) registerMux(pattern string, handler dns.Handler) {
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s.dnsMux.Handle(pattern, handler)
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}
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func (s *Server) deregisterMux(pattern string) {
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s.dnsMux.HandleRemove(pattern)
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}
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