api: add experimental Gateway API flags (#7970)

* API for Experimental Gateway APIs

Signed-off-by: Huabing (Robin) Zhao <zhaohuabing@gmail.com>

* address comments

Signed-off-by: Huabing (Robin) Zhao <zhaohuabing@gmail.com>

* address comments

Signed-off-by: Huabing (Robin) Zhao <zhaohuabing@gmail.com>

* fix lint

Signed-off-by: Huabing (Robin) Zhao <zhaohuabing@gmail.com>

* address comments

Signed-off-by: Huabing (Robin) Zhao <zhaohuabing@gmail.com>

* polish

Signed-off-by: Huabing (Robin) Zhao <zhaohuabing@gmail.com>

* fix lint

Signed-off-by: Huabing (Robin) Zhao <zhaohuabing@gmail.com>

---------

Signed-off-by: Huabing (Robin) Zhao <zhaohuabing@gmail.com>

Author: zhaohuabing

api/v1alpha1/envoygateway_helpers.go

@@ -128,6 +128,19 @@ var defaultRuntimeFlags = map[RuntimeFlag]bool{
 	XDSNameSchemeV2: false,
 }
 
+// IsEnabled checks if an experimental Gateway API is enabled in the EnvoyGateway configuration.
+func (f *GatewayAPIs) IsEnabled(api GatewayAPI) bool {
+	if f != nil {
+		for _, enable := range f.Enabled {
+			if enable == api {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
 // IsEnabled checks if a runtime flag is enabled in the EnvoyGateway configuration.
 func (f *RuntimeFlags) IsEnabled(flag RuntimeFlag) bool {
 	if f != nil {

api/v1alpha1/envoygateway_types.go

@@ -100,11 +100,36 @@ type EnvoyGatewaySpec struct {
 	// +optional
 	ExtensionAPIs *ExtensionAPISettings `json:"extensionApis,omitempty"`
 
+	// GatewayAPIs defines feature flags for experimental Gateway API resources.
+	// These APIs live under the gateway.networking.x-k8s.io group and are opt-in.
+	//
+	// +optional
+	// +notImplementedHide
+	GatewayAPIs *GatewayAPIs `json:"gatewayAPIs,omitempty"`
+
 	// RuntimeFlags defines the runtime flags for Envoy Gateway.
 	// Unlike ExtensionAPIs, these flags are temporary and will be removed in future releases once the related features are stable.
 	RuntimeFlags *RuntimeFlags `json:"runtimeFlags,omitempty"`
 }
 
+// GatewayAPI defines an experimental Gateway API resource that can be enabled.
+// +enum
+// +kubebuilder:validation:Enum=XListenerSet;XBackendTrafficPolicy
+type GatewayAPI string
+
+const (
+// XListenerSet enables the Gateway API XListenerSet resource.
+// XListenerSet GatewayAPI = "XListenerSet"
+// XBackendTrafficPolicy enables the Gateway API XBackendTrafficPolicy resource.
+// XBackendTrafficPolicy GatewayAPI = "XBackendTrafficPolicy"
+)
+
+// GatewayAPIs provides a mechanism to opt into experimental Gateway API resources.
+// These APIs are experimental today and are subject to change or removal as they mature.
+type GatewayAPIs struct {
+	Enabled []GatewayAPI `json:"enabled,omitempty"`
+}
+
 // RuntimeFlag defines a runtime flag used to guard breaking changes or risky experimental features in new Envoy Gateway releases.
 // A runtime flag may be enabled or disabled by default and can be toggled through the EnvoyGateway resource.
 // +enum

api/v1alpha1/zz_generated.deepcopy.go

@@ -2273,6 +2273,33 @@ _Appears in:_
 | `controllerName` | _string_ |  false  |  | ControllerName defines the name of the Gateway API controller. If unspecified,<br />defaults to "gateway.envoyproxy.io/gatewayclass-controller". See the following<br />for additional details:<br />  https://gateway-api.sigs.k8s.io/reference/1.4/spec/#gatewayclass |
 
 
+#### GatewayAPI
+
+_Underlying type:_ _string_
+
+GatewayAPI defines an experimental Gateway API resource that can be enabled.
+
+_Appears in:_
+- [GatewayAPIs](#gatewayapis)
+
+
+
+#### GatewayAPIs
+
+
+
+GatewayAPIs provides a mechanism to opt into experimental Gateway API resources.
+These APIs are experimental today and are subject to change or removal as they mature.
+
+_Appears in:_
+- [EnvoyGateway](#envoygateway)
+- [EnvoyGatewaySpec](#envoygatewayspec)
+
+| Field | Type | Required | Default | Description |
+| ---   | ---  | ---      | ---     | ---         |
+| `enabled` | _[GatewayAPI](#gatewayapi) array_ |  true  |  |  |
+
+
 #### GlobalRateLimit