remove the kubeadm feature gate.

cmd/kubeadm/app/componentconfigs/kubeproxy.go

@@ -94,7 +94,7 @@ func (kp *kubeProxyConfig) Default(cfg *kubeadmapi.ClusterConfiguration, localAP
 
 	// The below code is necessary because while KubeProxy may be defined, the user may not
 	// have defined any feature-gates, thus FeatureGates will be nil and the later insertion
-	// of any feature-gates (e.g. IPv6DualStack) will cause a panic.
+	// of any feature-gates will cause a panic.
 	if kp.config.FeatureGates == nil {
 		kp.config.FeatureGates = map[string]bool{}
 	}

cmd/kubeadm/app/features/features.go

@@ -29,8 +29,6 @@ import (
 )
 
 const (
-	// IPv6DualStack is expected to be beta in v1.21
-	IPv6DualStack = "IPv6DualStack"
 	// PublicKeysECDSA is expected to be alpha in v1.19
 	PublicKeysECDSA = "PublicKeysECDSA"
 	// RootlessControlPlane is expected to be in alpha in v1.22
@@ -41,7 +39,6 @@ const (
 
 // InitFeatureGates are the default feature gates for the init command
 var InitFeatureGates = FeatureList{
-	IPv6DualStack:               {FeatureSpec: featuregate.FeatureSpec{Default: true, LockToDefault: true, PreRelease: featuregate.GA}, HiddenInHelpText: true},
 	PublicKeysECDSA:             {FeatureSpec: featuregate.FeatureSpec{Default: false, PreRelease: featuregate.Alpha}},
 	RootlessControlPlane:        {FeatureSpec: featuregate.FeatureSpec{Default: false, PreRelease: featuregate.Alpha}},
 	UnversionedKubeletConfigMap: {FeatureSpec: featuregate.FeatureSpec{Default: false, PreRelease: featuregate.Alpha}},

cmd/kubeadm/test/cmd/init_test.go

@@ -264,10 +264,6 @@ func TestCmdInitFeatureGates(t *testing.T) {
 			name: "no feature gates passed",
 			args: "",
 		},
-		{
-			name: "feature gate IPv6DualStack=true",
-			args: "--feature-gates=IPv6DualStack=true",
-		},
 		{
 			name: "feature gate PublicKeysECDSA=true",
 			args: "--feature-gates=PublicKeysECDSA=true",

test/e2e_kubeadm/networking_test.go

@@ -122,7 +122,7 @@ var _ = Describe("networking [setup-networking]", func() {
 			})
 		})
 	})
-	ginkgo.Context("dual-stack [Feature:IPv6DualStack]", func() {
+	ginkgo.Context("dual-stack", func() {
 		ginkgo.Context("podSubnet", func() {
 			ginkgo.It("should be properly configured if specified in kubeadm-config", func() {
 				if !dualStack {