Allow override of kubeconfig dialer

cmd/kube-apiserver/app/server.go

@@ -91,6 +91,10 @@ const (
 	etcdRetryInterval = 1 * time.Second
 )
 
+var (
+	DefaultProxyDialerFn utilnet.DialFunc
+)
+
 // NewAPIServerCommand creates a *cobra.Command object with default parameters
 func NewAPIServerCommand(stopCh <-chan struct{}) *cobra.Command {
 	s := options.NewServerRunOptions()
@@ -163,7 +167,12 @@ func CreateServerChain(completedOptions completedServerRunOptions, stopCh <-chan
 		return nil, err
 	}
 
+	if DefaultProxyDialerFn != nil {
+		completedOptions.KubeletConfig.Dial = DefaultProxyDialerFn
+	}
+
 	kubeAPIServerConfig, insecureServingInfo, serviceResolver, pluginInitializer, admissionPostStartHook, err := CreateKubeAPIServerConfig(completedOptions, nodeTunneler, proxyTransport)
+
 	if err != nil {
 		return nil, err
 	}