Merge pull request #33379 from grosskur/kube-dns-bind-address

Automatic merge from submit-queue

kube-dns: Add --dns-bind-address flag

Currently, `kube-dns` always binds to `0.0.0.0` when starting the SkyDNS server. Sometimes it's useful to have it bind to a different address for testing. So add a new `--dns-bind-address` flag that can be used to configure this (default is `0.0.0.0`).

cmd/kube-dns/app/options/options.go

@@ -34,6 +34,7 @@ type KubeDNSConfig struct {
 	KubeConfigFile string
 	KubeMasterURL  string
 	HealthzPort    int
+	DNSBindAddress string
 	DNSPort        int
 	// Federations maps federation names to their registered domain names.
 	Federations map[string]string
@@ -45,6 +46,7 @@ func NewKubeDNSConfig() *KubeDNSConfig {
 		KubeConfigFile: "",
 		KubeMasterURL:  "",
 		HealthzPort:    8081,
+		DNSBindAddress: "0.0.0.0",
 		DNSPort:        53,
 		Federations:    make(map[string]string),
 	}
@@ -143,6 +145,7 @@ func (s *KubeDNSConfig) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&s.KubeConfigFile, "kubecfg-file", s.KubeConfigFile, "Location of kubecfg file for access to kubernetes master service; --kube-master-url overrides the URL part of this; if neither this nor --kube-master-url are provided, defaults to service account tokens")
 	fs.Var(kubeMasterURLVar{&s.KubeMasterURL}, "kube-master-url", "URL to reach kubernetes master. Env variables in this flag will be expanded.")
 	fs.IntVar(&s.HealthzPort, "healthz-port", s.HealthzPort, "port on which to serve a kube-dns HTTP readiness probe.")
+	fs.StringVar(&s.DNSBindAddress, "dns-bind-address", s.DNSBindAddress, "address on which to serve DNS requests.")
 	fs.IntVar(&s.DNSPort, "dns-port", s.DNSPort, "port on which to serve DNS requests.")
 	fs.Var(federationsVar{s.Federations}, "federations", "a comma separated list of the federation names and their corresponding domain names to which this cluster belongs. Example: \"myfederation1=example.com,myfederation2=example2.com,myfederation3=example.com\"")
 }

cmd/kube-dns/app/server.go

@@ -41,6 +41,7 @@ type KubeDNSServer struct {
 	// DNS domain name.
 	domain         string
 	healthzPort    int
+	dnsBindAddress string
 	dnsPort        int
 	kd             *kdns.KubeDNS
 }
@@ -55,6 +56,7 @@ func NewKubeDNSServerDefault(config *options.KubeDNSConfig) *KubeDNSServer {
 		glog.Fatalf("Failed to create a kubernetes client: %v", err)
 	}
 	ks.healthzPort = config.HealthzPort
+	ks.dnsBindAddress = config.DNSBindAddress
 	ks.dnsPort = config.DNSPort
 	ks.kd, err = kdns.NewKubeDNS(kubeClient, config.ClusterDomain, config.Federations)
 	if err != nil {
@@ -135,8 +137,8 @@ func setupSignalHandlers() {
 }
 
 func (d *KubeDNSServer) startSkyDNSServer() {
-	glog.Infof("Starting SkyDNS server. Listening on port:%d", d.dnsPort)
+	glog.Infof("Starting SkyDNS server. Listening on %s:%d", d.dnsBindAddress, d.dnsPort)
-	skydnsConfig := &server.Config{Domain: d.domain, DnsAddr: fmt.Sprintf("0.0.0.0:%d", d.dnsPort)}
+	skydnsConfig := &server.Config{Domain: d.domain, DnsAddr: fmt.Sprintf("%s:%d", d.dnsBindAddress, d.dnsPort)}
 	server.SetDefaults(skydnsConfig)
 	s := server.New(d.kd, skydnsConfig)
 	if err := metrics.Metrics(); err != nil {

hack/verify-flags/known-flags.txt

@@ -128,6 +128,7 @@ deserialization-cache-size
 dest-file
 disable-filter
 disable-kubenet
+dns-bind-address
 dns-port
 dns-provider
 dns-provider-config