Refactor the process to get ip address of loopback interface

Author: chendotjs

staging/src/k8s.io/apiserver/pkg/server/BUILD

@@ -40,6 +40,7 @@ go_test(
         "//vendor/github.com/go-openapi/spec:go_default_library",
         "//vendor/github.com/stretchr/testify/assert:go_default_library",
         "//vendor/k8s.io/kube-openapi/pkg/common:go_default_library",
+        "//vendor/k8s.io/utils/net:go_default_library",
     ],
 )
 
@@ -120,6 +121,7 @@ go_library(
         "//vendor/k8s.io/kube-openapi/pkg/handler:go_default_library",
         "//vendor/k8s.io/kube-openapi/pkg/util:go_default_library",
         "//vendor/k8s.io/kube-openapi/pkg/util/proto:go_default_library",
+        "//vendor/k8s.io/utils/net:go_default_library",
     ],
 )
 

staging/src/k8s.io/apiserver/pkg/server/config_selfclient.go

@@ -21,6 +21,7 @@ import (
 	"net"
 
 	restclient "k8s.io/client-go/rest"
+	netutils "k8s.io/utils/net"
 )
 
 // LoopbackClientServerNameOverride is passed to the apiserver from the loopback client in order to
@@ -70,23 +71,27 @@ func LoopbackHostPort(bindAddress string) (string, string, error) {
 		return "", "", fmt.Errorf("invalid server bind address: %q", bindAddress)
 	}
 
-	isIPv6 := net.ParseIP(host).To4() == nil
+	isIPv6 := netutils.IsIPv6String(host)
 
 	// Value is expected to be an IP or DNS name, not "0.0.0.0".
 	if host == "0.0.0.0" || host == "::" {
-		host = "localhost"
 		// Get ip of local interface, but fall back to "localhost".
 		// Note that "localhost" is resolved with the external nameserver first with Go's stdlib.
 		// So if localhost.<yoursearchdomain> resolves, we don't get a 127.0.0.1 as expected.
-		addrs, err := net.InterfaceAddrs()
-		if err == nil {
-			for _, address := range addrs {
-				if ipnet, ok := address.(*net.IPNet); ok && ipnet.IP.IsLoopback() && isIPv6 == (ipnet.IP.To4() == nil) {
-					host = ipnet.IP.String()
-					break
-				}
+		host = getLoopbackAddress(isIPv6)
+	}
+	return host, port, nil
+}
+
+// getLoopbackAddress returns the ip address of local loopback interface. If any error occurs or loopback interface is not found, will fall back to "localhost"
+func getLoopbackAddress(wantIPv6 bool) string {
+	addrs, err := net.InterfaceAddrs()
+	if err == nil {
+		for _, address := range addrs {
+			if ipnet, ok := address.(*net.IPNet); ok && ipnet.IP.IsLoopback() && wantIPv6 == netutils.IsIPv6(ipnet.IP) {
+				return ipnet.IP.String()
 			}
 		}
 	}
-	return host, port, nil
+	return "localhost"
 }

staging/src/k8s.io/apiserver/pkg/server/config_selfclient_test.go

@@ -19,6 +19,8 @@ package server
 import (
 	"net"
 	"testing"
+
+	netutils "k8s.io/utils/net"
 )
 
 func TestLoopbackHostPortIPv4(t *testing.T) {
@@ -95,7 +97,7 @@ func isIPv6LoopbackSupported() (ipv6 bool, ipv6only bool, err error) {
 		if !ok || !ipnet.IP.IsLoopback() {
 			continue
 		}
-		if ipnet.IP.To4() == nil {
+		if netutils.IsIPv6(ipnet.IP) {
 			ipv6 = true
 			continue
 		}