Allow override of kubeconfig dialer

cmd/kube-apiserver/app/server.go

@@ -32,6 +32,7 @@ import (
 	"github.com/spf13/cobra"
 
 	utilerrors "k8s.io/apimachinery/pkg/util/errors"
+	utilnet "k8s.io/apimachinery/pkg/util/net"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apiserver/pkg/admission"
 	"k8s.io/apiserver/pkg/authentication/authenticator"
@@ -74,6 +75,10 @@ import (
 const etcdRetryLimit = 60
 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()
@@ -153,6 +158,9 @@ func Run(completeOptions completedServerRunOptions, stopCh <-chan struct{}) erro
 
 // CreateServerChain creates the apiservers connected via delegation.
 func CreateServerChain(completedOptions completedServerRunOptions, stopCh <-chan struct{}) (*master.Config, *genericapiserver.GenericAPIServer, error) {
+	if DefaultProxyDialerFn != nil {
+		completedOptions.KubeletConfig.Dial = DefaultProxyDialerFn
+	}
 
 	kubeAPIServerConfig, insecureServingInfo, serviceResolver, pluginInitializer, admissionPostStartHook, err := CreateKubeAPIServerConfig(completedOptions)
 	if err != nil {