feat: introduce EndpointHostname in BTP to set hostname field in Endpoint

api/v1alpha1/backendtrafficpolicy_types.go

@@ -151,6 +151,12 @@ type BackendTrafficPolicySpec struct {
 	//
 	// +optional
 	RoutingType *RoutingType `json:"routingType,omitempty"`
+
+	// EndpointHostname configures the hostname value attached to backend endpoints.
+	// If unset, no hostname is attached to Kubernetes Service endpoints.
+	//
+	// +optional
+	EndpointHostname *BackendEndpointHostname `json:"endpointHostname,omitempty"`
 }
 
 type BackendTelemetry struct {

api/v1alpha1/shared_types.go

@@ -693,6 +693,40 @@ type ClusterSettings struct {
 	HTTP2 *HTTP2Settings `json:"http2,omitempty"`
 }
 
+// BackendEndpointHostnameType defines how endpoint hostnames should be populated.
+//
+// +kubebuilder:validation:Enum=None;KubernetesService;Static
+type BackendEndpointHostnameType string
+
+const (
+	// BackendEndpointHostnameTypeNone does not attach hostnames to backend endpoints.
+	BackendEndpointHostnameTypeNone BackendEndpointHostnameType = "None"
+	// BackendEndpointHostnameTypeKubernetesService uses the Kubernetes Service FQDN.
+	BackendEndpointHostnameTypeKubernetesService BackendEndpointHostnameType = "KubernetesService"
+	// BackendEndpointHostnameTypeStatic uses a user-specified static hostname.
+	BackendEndpointHostnameTypeStatic BackendEndpointHostnameType = "Static"
+)
+
+// BackendEndpointHostname configures hostnames attached to backend endpoints.
+//
+// +kubebuilder:validation:XValidation:message="hostname must be set when type is Static",rule="self.type == 'Static' ? has(self.hostname) : true"
+// +kubebuilder:validation:XValidation:message="hostname must not be set when type is not Static",rule="self.type != 'Static' ? !has(self.hostname) : true"
+type BackendEndpointHostname struct {
+	// Type determines how endpoint hostnames should be populated.
+	//
+	// +kubebuilder:validation:Required
+	Type BackendEndpointHostnameType `json:"type"`
+
+	// Hostname is a custom static hostname to attach to backend endpoints.
+	// This field is required when type is "Static" and must not be set for other types.
+	//
+	// +optional
+	// +kubebuilder:validation:MinLength=1
+	// +kubebuilder:validation:MaxLength=253
+	// +kubebuilder:validation:Pattern=`^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$`
+	Hostname *string `json:"hostname,omitempty"`
+}
+
 // CIDR defines a CIDR Address range.
 // A CIDR can be an IPv4 address range such as "192.168.1.0/24" or an IPv6 address range such as "2001:0db8:11a3:09d7::/64".
 // +kubebuilder:validation:Pattern=`((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\/([0-9]+))|((([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))\/([0-9]+))`

charts/gateway-crds-helm/templates/generated/gateway.envoyproxy.io_backendtrafficpolicies.yaml

@@ -540,6 +540,35 @@ spec:
                       Defaults to true.
                     type: boolean
                 type: object
+              endpointHostname:
+                description: |-
+                  EndpointHostname configures the hostname value attached to backend endpoints.
+                  If unset, no hostname is attached to Kubernetes Service endpoints.
+                properties:
+                  hostname:
+                    description: |-
+                      Hostname is a custom static hostname to attach to backend endpoints.
+                      This field is required when type is "Static" and must not be set for other types.
+                    maxLength: 253
+                    minLength: 1
+                    pattern: ^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$
+                    type: string
+                  type:
+                    description: Type determines how endpoint hostnames should be
+                      populated.
+                    enum:
+                    - None
+                    - KubernetesService
+                    - Static
+                    type: string
+                required:
+                - type
+                type: object
+                x-kubernetes-validations:
+                - message: hostname must be set when type is Static
+                  rule: 'self.type == ''Static'' ? has(self.hostname) : true'
+                - message: hostname must not be set when type is not Static
+                  rule: 'self.type != ''Static'' ? !has(self.hostname) : true'
               faultInjection:
                 description: |-
                   FaultInjection defines the fault injection policy to be applied. This configuration can be used to

charts/gateway-helm/charts/crds/crds/generated/gateway.envoyproxy.io_backendtrafficpolicies.yaml

@@ -539,6 +539,35 @@ spec:
                       Defaults to true.
                     type: boolean
                 type: object
+              endpointHostname:
+                description: |-
+                  EndpointHostname configures the hostname value attached to backend endpoints.
+                  If unset, no hostname is attached to Kubernetes Service endpoints.
+                properties:
+                  hostname:
+                    description: |-
+                      Hostname is a custom static hostname to attach to backend endpoints.
+                      This field is required when type is "Static" and must not be set for other types.
+                    maxLength: 253
+                    minLength: 1
+                    pattern: ^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$
+                    type: string
+                  type:
+                    description: Type determines how endpoint hostnames should be
+                      populated.
+                    enum:
+                    - None
+                    - KubernetesService
+                    - Static
+                    type: string
+                required:
+                - type
+                type: object
+                x-kubernetes-validations:
+                - message: hostname must be set when type is Static
+                  rule: 'self.type == ''Static'' ? has(self.hostname) : true'
+                - message: hostname must not be set when type is not Static
+                  rule: 'self.type != ''Static'' ? !has(self.hostname) : true'
               faultInjection:
                 description: |-
                   FaultInjection defines the fault injection policy to be applied. This configuration can be used to

internal/cmd/egctl/translate.go

@@ -25,6 +25,7 @@ import (
 
 	egv1a1 "github.com/envoyproxy/gateway/api/v1alpha1"
 	"github.com/envoyproxy/gateway/api/v1alpha1/validation"
+	"github.com/envoyproxy/gateway/internal/envoygateway/config"
 	"github.com/envoyproxy/gateway/internal/gatewayapi"
 	"github.com/envoyproxy/gateway/internal/gatewayapi/resource"
 	"github.com/envoyproxy/gateway/internal/gatewayapi/status"
@@ -292,6 +293,7 @@ func translateGatewayAPIToIR(resources *resource.Resources) (*gatewayapi.Transla
 		EndpointRoutingDisabled: true,
 		EnvoyPatchPolicyEnabled: true,
 		BackendEnabled:          true,
+		DNSDomain:               config.DefaultDNSDomain,
 		// Discard logs during translation for egctl command to avoid polluting output
 		Logger: logging.DefaultLogger(io.Discard, egv1a1.LogLevelInfo),
 	}
@@ -322,6 +324,7 @@ func translateGatewayAPIToGatewayAPI(resources *resource.Resources) (resource.Re
 		EndpointRoutingDisabled: true,
 		EnvoyPatchPolicyEnabled: true,
 		BackendEnabled:          true,
+		DNSDomain:               config.DefaultDNSDomain,
 		Logger:                  logging.DefaultLogger(io.Discard, egv1a1.LogLevelInfo),
 	}
 	gRes, _ := gTranslator.Translate(resources)
@@ -362,6 +365,7 @@ func TranslateGatewayAPIToXds(namespace, dnsDomain, resourceType string, resourc
 		EndpointRoutingDisabled: opts.EndpointRoutingDisabled,
 		EnvoyPatchPolicyEnabled: opts.EnvoyPatchPolicyEnabled,
 		BackendEnabled:          opts.BackendEnabled,
+		DNSDomain:               dnsDomain,
 		Logger:                  logging.DefaultLogger(io.Discard, egv1a1.LogLevelInfo),
 	}
 	gRes, _ := gTranslator.Translate(resources)

internal/gatewayapi/backendtrafficpolicy.go

@@ -53,6 +53,15 @@ type BTPRoutingTypeIndex struct {
 	gatewayLevel   map[btpRoutingKey]*egv1a1.RoutingType
 }
 
+// BTPEndpointHostnameIndex holds EndpointHostname values from BackendTrafficPolicies.
+// This avoids an O(BTPs) lookup for every iteration of processDestination.
+type BTPEndpointHostnameIndex struct {
+	routeRuleLevel map[btpRoutingKey]*egv1a1.BackendEndpointHostname
+	routeLevel     map[btpRoutingKey]*egv1a1.BackendEndpointHostname
+	listenerLevel  map[btpRoutingKey]*egv1a1.BackendEndpointHostname
+	gatewayLevel   map[btpRoutingKey]*egv1a1.BackendEndpointHostname
+}
+
 // BuildBTPRoutingTypeIndex builds a pre-computed index of RoutingType values
 // from BackendTrafficPolicies, organized by priority-level.
 // BTPs are pre-sorted by the provider layer, so first-write-wins respects priority.
@@ -66,6 +75,16 @@ func hasBTPRoutingType(btps []*egv1a1.BackendTrafficPolicy) bool {
 	return false
 }
 
+func hasBTPEndpointHostname(btps []*egv1a1.BackendTrafficPolicy) bool {
+	for _, btp := range btps {
+		if btp.Spec.EndpointHostname != nil {
+			return true
+		}
+	}
+
+	return false
+}
+
 func BuildBTPRoutingTypeIndex(
 	btps []*egv1a1.BackendTrafficPolicy,
 	routes []client.Object,
@@ -136,6 +155,66 @@ func BuildBTPRoutingTypeIndex(
 	return idx
 }
 
+func BuildBTPEndpointHostnameIndex(
+	btps []*egv1a1.BackendTrafficPolicy,
+	routes []client.Object,
+	gateways []*GatewayContext,
+) *BTPEndpointHostnameIndex {
+	idx := &BTPEndpointHostnameIndex{
+		routeRuleLevel: make(map[btpRoutingKey]*egv1a1.BackendEndpointHostname),
+		routeLevel:     make(map[btpRoutingKey]*egv1a1.BackendEndpointHostname),
+		listenerLevel:  make(map[btpRoutingKey]*egv1a1.BackendEndpointHostname),
+		gatewayLevel:   make(map[btpRoutingKey]*egv1a1.BackendEndpointHostname),
+	}
+
+	allTargets := make([]client.Object, 0, len(routes)+len(gateways))
+	allTargets = append(allTargets, routes...)
+	for _, gw := range gateways {
+		allTargets = append(allTargets, gw)
+	}
+
+	for _, btp := range btps {
+		if btp.Spec.EndpointHostname == nil {
+			continue
+		}
+
+		refs := getPolicyTargetRefs(btp.Spec.PolicyTargetReferences, allTargets, btp.Namespace)
+		for _, ref := range refs {
+			kind := string(ref.Kind)
+			key := btpRoutingKey{
+				Kind:        kind,
+				Namespace:   btp.Namespace,
+				Name:        string(ref.Name),
+				SectionName: string(ptr.Deref(ref.SectionName, "")),
+			}
+
+			if kind == resource.KindGateway {
+				if ref.SectionName != nil {
+					if _, exists := idx.listenerLevel[key]; !exists {
+						idx.listenerLevel[key] = btp.Spec.EndpointHostname
+					}
+				} else {
+					if _, exists := idx.gatewayLevel[key]; !exists {
+						idx.gatewayLevel[key] = btp.Spec.EndpointHostname
+					}
+				}
+			} else {
+				if ref.SectionName != nil {
+					if _, exists := idx.routeRuleLevel[key]; !exists {
+						idx.routeRuleLevel[key] = btp.Spec.EndpointHostname
+					}
+				} else {
+					if _, exists := idx.routeLevel[key]; !exists {
+						idx.routeLevel[key] = btp.Spec.EndpointHostname
+					}
+				}
+			}
+		}
+	}
+
+	return idx
+}
+
 // LookupBTPRoutingType resolves the RoutingType for a specific route rule
 // and gateway/listener combination by checking the index in
 // priority order: routeRule > route > listener > gateway.
@@ -200,6 +279,65 @@ func (idx *BTPRoutingTypeIndex) LookupBTPRoutingType(
 	return nil
 }
 
+// LookupBTPEndpointHostname resolves the EndpointHostname for a specific route rule
+// and gateway/listener combination by checking the index in
+// priority order: routeRule > route > listener > gateway.
+func (idx *BTPEndpointHostnameIndex) LookupBTPEndpointHostname(
+	routeKind gwapiv1.Kind,
+	routeNN types.NamespacedName,
+	gatewayNN types.NamespacedName,
+	listenerName *gwapiv1.SectionName,
+	routeRuleName *gwapiv1.SectionName,
+) *egv1a1.BackendEndpointHostname {
+	if idx == nil {
+		return nil
+	}
+
+	if routeRuleName != nil {
+		key := btpRoutingKey{
+			Kind:        string(routeKind),
+			Namespace:   routeNN.Namespace,
+			Name:        routeNN.Name,
+			SectionName: string(*routeRuleName),
+		}
+		if eh, ok := idx.routeRuleLevel[key]; ok {
+			return eh
+		}
+	}
+
+	routeKey := btpRoutingKey{
+		Kind:      string(routeKind),
+		Namespace: routeNN.Namespace,
+		Name:      routeNN.Name,
+	}
+	if eh, ok := idx.routeLevel[routeKey]; ok {
+		return eh
+	}
+
+	if listenerName != nil {
+		listenerKey := btpRoutingKey{
+			Kind:        resource.KindGateway,
+			Namespace:   gatewayNN.Namespace,
+			Name:        gatewayNN.Name,
+			SectionName: string(*listenerName),
+		}
+		if eh, ok := idx.listenerLevel[listenerKey]; ok {
+			return eh
+		}
+	}
+
+	gwKey := btpRoutingKey{
+		Kind:      resource.KindGateway,
+		Namespace: gatewayNN.Namespace,
+		Name:      gatewayNN.Name,
+	}
+	if eh, ok := idx.gatewayLevel[gwKey]; ok {
+		return eh
+	}
+
+	return nil
+}
+
 // deprecatedFieldsUsedInBackendTrafficPolicy returns a map of deprecated field paths to their alternatives.
 func deprecatedFieldsUsedInBackendTrafficPolicy(policy *egv1a1.BackendTrafficPolicy) map[string]string {
 	deprecatedFields := make(map[string]string)