add MTUCustomizer feature gate and wire it into config and webhooks

axel7born · axel7born · commit 6838e2f5b902 · 2026-03-11T14:58:17.000+01:00
diff --git a/charts/gardener-extension-provider-aws/templates/configmap-custom-mtu.yaml b/charts/gardener-extension-provider-aws/templates/configmap-custom-mtu.yaml
@@ -1,3 +1,4 @@
+{{ if and (eq (include "seed.provider" .) "aws") (index .Values.config.featureGates "MTUCustomizer") }}
 apiVersion: v1
 kind: ConfigMap
 metadata:
@@ -21,3 +22,4 @@ data:
         echo changing mtu of non-virtual interface: ${interface}
         ip link set dev ${interface} mtu 1460
     done
+{{ end }}
diff --git a/charts/gardener-extension-provider-aws/templates/configmap.yaml b/charts/gardener-extension-provider-aws/templates/configmap.yaml
@@ -23,3 +23,9 @@ data:
 {{- if .Values.config.etcd.backup }}
       backup: {{- toYaml .Values.config.etcd.backup | nindent 8 }}
 {{- end }}
+{{- if .Values.config.featureGates }}
+    featureGates:
+  {{- range $feature, $enabled := .Values.config.featureGates }}
+      {{ $feature }}: {{ $enabled }}
+  {{- end }}
+{{- end }}
diff --git a/charts/gardener-extension-provider-aws/templates/daemonset-custom-mtu.yaml b/charts/gardener-extension-provider-aws/templates/daemonset-custom-mtu.yaml
@@ -1,4 +1,4 @@
-{{ if eq (include "seed.provider" .) "aws" }}
+{{ if and (eq (include "seed.provider" .) "aws") (index .Values.config.featureGates "MTUCustomizer") }}
 kind: DaemonSet
 apiVersion: apps/v1
 metadata:
diff --git a/charts/gardener-extension-provider-aws/values.yaml b/charts/gardener-extension-provider-aws/values.yaml
@@ -88,6 +88,8 @@ config:
       encrypted: true
 #     backup:
 #       schedule: "0 */1 * * *"
+  featureGates:
+    MTUCustomizer: true
 
 gardener:
   version: ""
diff --git a/cmd/gardener-extension-provider-aws/app/app.go b/cmd/gardener-extension-provider-aws/app/app.go
@@ -47,6 +47,7 @@ import (
 	"github.com/gardener/gardener-extension-provider-aws/pkg/controller/healthcheck"
 	awsinfrastructure "github.com/gardener/gardener-extension-provider-aws/pkg/controller/infrastructure"
 	awsworker "github.com/gardener/gardener-extension-provider-aws/pkg/controller/worker"
+	"github.com/gardener/gardener-extension-provider-aws/pkg/features"
 	awsseedprovider "github.com/gardener/gardener-extension-provider-aws/pkg/webhook/seedprovider"
 )
 
@@ -165,6 +166,10 @@ func NewControllerManagerCommand(ctx context.Context) *cobra.Command {
 				return fmt.Errorf("error completing options: %w", err)
 			}
 
+			if err := features.FeatureGate.SetFromMap(configFileOpts.Completed().Config.FeatureGates); err != nil {
+				return fmt.Errorf("error setting feature gates: %w", err)
+			}
+
 			if err := heartbeatCtrlOpts.Validate(); err != nil {
 				return err
 			}
diff --git a/cmd/gardener-extension-provider-aws/main.go b/cmd/gardener-extension-provider-aws/main.go
@@ -12,9 +12,11 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/manager/signals"
 
 	"github.com/gardener/gardener-extension-provider-aws/cmd/gardener-extension-provider-aws/app"
+	"github.com/gardener/gardener-extension-provider-aws/pkg/features"
 )
 
 func main() {
+	features.RegisterFeatureGates()
 	logf.SetLogger(logger.MustNewZapLogger(logger.InfoLevel, logger.FormatJSON))
 	cmd := app.NewControllerManagerCommand(signals.SetupSignalHandler())
 
diff --git a/example/controller-registration.yaml b/example/controller-registration.yaml
diff --git a/hack/api-reference/config.md b/hack/api-reference/config.md
@@ -84,6 +84,18 @@ github.com/gardener/gardener/extensions/pkg/apis/config/v1alpha1.HealthCheckConf
 <p>HealthCheckConfig is the config for the health check controller</p>
 </td>
 </tr>
+<tr>
+<td>
+<code>featureGates</code></br>
+<em>
+map[string]bool
+</em>
+</td>
+<td>
+<em>(Optional)</em>
+<p>FeatureGates contains information about enabled feature gates.</p>
+</td>
+</tr>
 </tbody>
 </table>
 <h3 id="aws.provider.extensions.config.gardener.cloud/v1alpha1.ETCD">ETCD
diff --git a/pkg/apis/config/types.go b/pkg/apis/config/types.go
@@ -24,6 +24,9 @@ type ControllerConfiguration struct {
 	ETCD ETCD
 	// HealthCheckConfig is the config for the health check controller
 	HealthCheckConfig *apisconfigv1alpha1.HealthCheckConfig
+	// FeatureGates contains information about enabled feature gates.
+	// +optional
+	FeatureGates map[string]bool
 }
 
 // ETCD is an etcd configuration.
diff --git a/pkg/apis/config/v1alpha1/types.go b/pkg/apis/config/v1alpha1/types.go
@@ -27,6 +27,9 @@ type ControllerConfiguration struct {
 	// HealthCheckConfig is the config for the health check controller
 	// +optional
 	HealthCheckConfig *healthcheckconfigv1alpha1.HealthCheckConfig `json:"healthCheckConfig,omitempty"`
+	// FeatureGates contains information about enabled feature gates.
+	// +optional
+	FeatureGates map[string]bool `json:"featureGates,omitempty"`
 }
 
 // ETCD is an etcd configuration.
diff --git a/pkg/apis/config/v1alpha1/zz_generated.conversion.go b/pkg/apis/config/v1alpha1/zz_generated.conversion.go
diff --git a/pkg/apis/config/v1alpha1/zz_generated.deepcopy.go b/pkg/apis/config/v1alpha1/zz_generated.deepcopy.go
diff --git a/pkg/apis/config/zz_generated.deepcopy.go b/pkg/apis/config/zz_generated.deepcopy.go
diff --git a/pkg/features/features.go b/pkg/features/features.go
@@ -0,0 +1,30 @@
+// SPDX-FileCopyrightText: SAP SE or an SAP affiliate company and Gardener contributors
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package features
+
+import (
+	"k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/component-base/featuregate"
+)
+
+const (
+	// MTUCustomizer enables the deployment of the mtu-customizer DaemonSet on AWS seed
+	// nodes to set network interface MTU to 1460.
+	// This feature gate is used to phase out MTU customization. It will be switched to
+	// default false in a future version and eventually removed along with all related code.
+	// alpha: v1.69 (default=true)
+	MTUCustomizer featuregate.Feature = "MTUCustomizer"
+)
+
+var FeatureGate featuregate.MutableFeatureGate = featuregate.NewFeatureGate()
+
+var featureGates = map[featuregate.Feature]featuregate.FeatureSpec{
+	MTUCustomizer: {Default: true, PreRelease: featuregate.Alpha},
+}
+
+// RegisterFeatureGates registers the feature gates of the provider-aws extension.
+func RegisterFeatureGates() {
+	runtime.Must(FeatureGate.Add(featureGates))
+}
diff --git a/pkg/webhook/controlplane/ensurer.go b/pkg/webhook/controlplane/ensurer.go
@@ -40,6 +40,7 @@ import (
 	"github.com/gardener/gardener-extension-provider-aws/imagevector"
 	"github.com/gardener/gardener-extension-provider-aws/pkg/apis/aws/helper"
 	"github.com/gardener/gardener-extension-provider-aws/pkg/aws"
+	"github.com/gardener/gardener-extension-provider-aws/pkg/features"
 	"github.com/gardener/gardener-extension-provider-aws/pkg/utils"
 )
 
@@ -476,6 +477,10 @@ func (e *ensurer) EnsureKubernetesGeneralConfiguration(_ context.Context, _ gcon
 
 // EnsureAdditionalUnits ensures that additional required system units are added.
 func (e *ensurer) EnsureAdditionalUnits(_ context.Context, _ gcontext.GardenContext, newObj, _ *[]extensionsv1alpha1.Unit) error {
+	if !features.FeatureGate.Enabled(features.MTUCustomizer) {
+		return nil
+	}
+
 	var (
 		customMTUUnitContent = `[Unit]
 Description=Apply a custom MTU to network interfaces
@@ -602,7 +607,9 @@ done
 
 // EnsureAdditionalFiles ensures that additional required system files are added.
 func (e *ensurer) EnsureAdditionalFiles(ctx context.Context, gctx gcontext.GardenContext, newObj, _ *[]extensionsv1alpha1.File) error {
-	*newObj = extensionswebhook.EnsureFileWithPath(*newObj, e.ensureMTUFiles())
+	if features.FeatureGate.Enabled(features.MTUCustomizer) {
+		*newObj = extensionswebhook.EnsureFileWithPath(*newObj, e.ensureMTUFiles())
+	}
 
 	cluster, err := gctx.GetCluster(ctx)
 	if err != nil {
diff --git a/pkg/webhook/controlplane/ensurer_test.go b/pkg/webhook/controlplane/ensurer_test.go
@@ -39,6 +39,7 @@ import (
 	"github.com/gardener/gardener-extension-provider-aws/imagevector"
 	"github.com/gardener/gardener-extension-provider-aws/pkg/apis/aws/v1alpha1"
 	"github.com/gardener/gardener-extension-provider-aws/pkg/aws"
+	"github.com/gardener/gardener-extension-provider-aws/pkg/features"
 )
 
 const namespace = "test"
@@ -48,6 +49,10 @@ func TestController(t *testing.T) {
 	RunSpecs(t, "ControlPlane Webhook Suite")
 }
 
+var _ = BeforeSuite(func() {
+	features.RegisterFeatureGates()
+})
+
 var _ = Describe("Ensurer", func() {
 	var (
 		ctrl *gomock.Controller

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-{{ if eq (include "seed.provider" .) "aws" }}`
	`1`	`+{{ if and (eq (include "seed.provider" .) "aws") (index .Values.config.featureGates "MTUCustomizer") }}`
`2`	`2`	`kind: DaemonSet`
`3`	`3`	`apiVersion: apps/v1`
`4`	`4`	`metadata:`
Original file line number	Diff line number	Diff line change
`@@ -47,6 +47,7 @@ import (`
`47`	`47`	`"github.com/gardener/gardener-extension-provider-aws/pkg/controller/healthcheck"`
`48`	`48`	`awsinfrastructure "github.com/gardener/gardener-extension-provider-aws/pkg/controller/infrastructure"`
`49`	`49`	`awsworker "github.com/gardener/gardener-extension-provider-aws/pkg/controller/worker"`
	`50`	`+ "github.com/gardener/gardener-extension-provider-aws/pkg/features"`
`50`	`51`	`awsseedprovider "github.com/gardener/gardener-extension-provider-aws/pkg/webhook/seedprovider"`
`51`	`52`	`)`
`52`	`53`
`@@ -165,6 +166,10 @@ func NewControllerManagerCommand(ctx context.Context) *cobra.Command {`
`165`	`166`	`return fmt.Errorf("error completing options: %w", err)`
`166`	`167`	`}`
`167`	`168`
	`169`	`+ if err := features.FeatureGate.SetFromMap(configFileOpts.Completed().Config.FeatureGates); err != nil {`
	`170`	`+ return fmt.Errorf("error setting feature gates: %w", err)`
	`171`	`+ }`
	`172`	`+`
`168`	`173`	`if err := heartbeatCtrlOpts.Validate(); err != nil {`
`169`	`174`	`return err`
`170`	`175`	`}`
Original file line number	Diff line number	Diff line change
`@@ -12,9 +12,11 @@ import (`
`12`	`12`	`"sigs.k8s.io/controller-runtime/pkg/manager/signals"`
`13`	`13`
`14`	`14`	`"github.com/gardener/gardener-extension-provider-aws/cmd/gardener-extension-provider-aws/app"`
	`15`	`+ "github.com/gardener/gardener-extension-provider-aws/pkg/features"`
`15`	`16`	`)`
`16`	`17`
`17`	`18`	`func main() {`
	`19`	`+ features.RegisterFeatureGates()`
`18`	`20`	`logf.SetLogger(logger.MustNewZapLogger(logger.InfoLevel, logger.FormatJSON))`
`19`	`21`	`cmd := app.NewControllerManagerCommand(signals.SetupSignalHandler())`
`20`	`22`
Original file line number	Diff line number	Diff line change
`@@ -24,6 +24,9 @@ type ControllerConfiguration struct {`
`24`	`24`	`ETCD ETCD`
`25`	`25`	`// HealthCheckConfig is the config for the health check controller`
`26`	`26`	`HealthCheckConfig *apisconfigv1alpha1.HealthCheckConfig`
	`27`	`+ // FeatureGates contains information about enabled feature gates.`
	`28`	`+ // +optional`
	`29`	`+ FeatureGates map[string]bool`
`27`	`30`	`}`
`28`	`31`
`29`	`32`	`// ETCD is an etcd configuration.`
Original file line number	Diff line number	Diff line change
`@@ -27,6 +27,9 @@ type ControllerConfiguration struct {`
`27`	`27`	`// HealthCheckConfig is the config for the health check controller`
`28`	`28`	`// +optional`
`29`	`29`	HealthCheckConfig *healthcheckconfigv1alpha1.HealthCheckConfig `json:"healthCheckConfig,omitempty"`
	`30`	`+ // FeatureGates contains information about enabled feature gates.`
	`31`	`+ // +optional`
	`32`	+ FeatureGates map[string]bool `json:"featureGates,omitempty"`
`30`	`33`	`}`
`31`	`34`
`32`	`35`	`// ETCD is an etcd configuration.`