Merge pull request kubernetes#104028 from nilo19/automated-cherry-pic…

…k-of-#103794-upstream-release-1.21

Automated cherry pick of kubernetes#103794: feat: Provide IPv6 support for internal load balancer

staging/src/k8s.io/legacy-cloud-providers/azure/azure_loadbalancer.go

@@ -1258,13 +1258,6 @@ func (az *Cloud) reconcileLoadBalancer(clusterName string, service *v1.Service,
 			// construct FrontendIPConfigurationPropertiesFormat
 			var fipConfigurationProperties *network.FrontendIPConfigurationPropertiesFormat
 			if isInternal {
-				// azure does not support ILB for IPv6 yet.
-				// TODO: remove this check when ILB supports IPv6 *and* the SDK
-				// have been rev'ed to 2019* version
-				if utilnet.IsIPv6String(service.Spec.ClusterIP) {
-					return nil, fmt.Errorf("ensure(%s): lb(%s) - internal load balancers does not support IPv6", serviceName, lbName)
-				}
-
 				subnetName := subnet(service)
 				if subnetName == nil {
 					subnetName = &az.SubnetName
@@ -1282,6 +1275,10 @@ func (az *Cloud) reconcileLoadBalancer(clusterName string, service *v1.Service,
 					Subnet: &subnet,
 				}
 
+				if utilnet.IsIPv6String(service.Spec.ClusterIP) {
+					configProperties.PrivateIPAddressVersion = network.IPv6
+				}
+
 				loadBalancerIP := service.Spec.LoadBalancerIP
 				if loadBalancerIP != "" {
 					configProperties.PrivateIPAllocationMethod = network.Static