Added docs and fix for ref grant in service import case

docs/latest/user/multicluster-service.md

@@ -0,0 +1,84 @@
+# Multicluster Service Routing
+
+The Multicluster Service API ServiceImport object can be used as part of the GatewayAPI backendRef for configuring routes. For more information about multicluster service API follow [sig documentation](https://multicluster.sigs.k8s.io/concepts/multicluster-services-api/).
+
+We will use [Submariner project](https://github.com/submariner-io/submariner) for setting up the multicluster environment for exporting the service to be routed from peer clusters.
+
+# Setting KIND clusters and installing Submariner.
+
+- We will be using KIND clusters to demonstrate this example.
+
+```shell
+git clone https://github.com/submariner-io/submariner-operator
+cd submariner-operator
+make clusters
+```
+
+Note: remain in submariner-operator directory for the rest of the steps in this section
+
+- Install subctl:
+
+```shell
+curl -Ls https://get.submariner.io  | VERSION=v0.14.6 bash
+```
+
+- Set up multicluster service API and submariner for cross cluster traffic using ServiceImport
+
+```shell
+subctl deploy-broker --kubeconfig output/kubeconfigs/kind-config-cluster1 --globalnet
+subctl join --kubeconfig output/kubeconfigs/kind-config-cluster1 broker-info.subm --clusterid cluster1 --natt=false
+subctl join --kubeconfig output/kubeconfigs/kind-config-cluster2 broker-info.subm --clusterid cluster2 --natt=false
+```
+
+Once the above steps are done and all the pods are up in both the clusters. We are ready for installing envoy gateway.
+
+# Install EnvoyGateway
+
+Install the Gateway API CRDs and Envoy Gateway in cluster1:
+
+```shell
+helm install eg oci://docker.io/envoyproxy/gateway-helm --version v0.0.0-latest -n envoy-gateway-system --create-namespace --kubeconfig output/kubeconfigs/kind-config-cluster1
+```
+
+Wait for Envoy Gateway to become available:
+
+```shell
+kubectl wait --timeout=5m -n envoy-gateway-system deployment/envoy-gateway --for=condition=Available --kubeconfig output/kubeconfigs/kind-config-cluster1
+```
+
+# Install Application
+
+Install the backend application in cluster2 and export it through subctl command.
+
+```shell
+kubectl apply -f https://raw.githubusercontent.com/envoyproxy/gateway/latest/examples/kubernetes/application.yaml --kubeconfig output/kubeconfigs/kind-config-cluster2
+subctl export service backend --namespace default --kubeconfig output/kubeconfigs/kind-config-cluster2
+```
+
+# Create GatewayAPI Objects
+
+Create the GatewayAPI objects GatewayClass, Gateway and HTTPRoute in cluster1 to set up the routing.
+
+```shell
+kubectl apply -f https://raw.githubusercontent.com/envoyproxy/gateway/latest/examples/kubernetes/multicluster-service.yaml --kubeconfig output/kubeconfigs/kind-config-cluster1
+```
+
+## Testing the Configuration
+
+Get the name of the Envoy service created the by the example Gateway:
+
+```shell
+export ENVOY_SERVICE=$(kubectl get svc -n envoy-gateway-system --selector=gateway.envoyproxy.io/owning-gateway-namespace=default,gateway.envoyproxy.io/owning-gateway-name=eg -o jsonpath='{.items[0].metadata.name}')
+```
+
+Port forward to the Envoy service:
+
+```shell
+kubectl -n envoy-gateway-system port-forward service/${ENVOY_SERVICE} 8888:80 &
+```
+
+Curl the example app through Envoy proxy:
+
+```shell
+curl --verbose --header "Host: www.example.com" http://localhost:8888/get
+```

examples/kubernetes/application.yaml

@@ -0,0 +1,53 @@
+---
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: backend
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: backend
+  labels:
+    app: backend
+    service: backend
+spec:
+  ports:
+    - name: http
+      port: 3000
+      targetPort: 3000
+  selector:
+    app: backend
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: backend
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: backend
+      version: v1
+  template:
+    metadata:
+      labels:
+        app: backend
+        version: v1
+    spec:
+      serviceAccountName: backend
+      containers:
+        - image: gcr.io/k8s-staging-ingressconformance/echoserver:v20221109-7ee2f3e
+          imagePullPolicy: IfNotPresent
+          name: backend
+          ports:
+            - containerPort: 3000
+          env:
+            - name: POD_NAME
+              valueFrom:
+                fieldRef:
+                  fieldPath: metadata.name
+            - name: NAMESPACE
+              valueFrom:
+                fieldRef:
+                  fieldPath: metadata.namespace

examples/kubernetes/multicluster-service.yaml

@@ -0,0 +1,54 @@
+apiVersion: gateway.networking.k8s.io/v1beta1
+kind: GatewayClass
+metadata:
+  name: eg
+spec:
+  controllerName: gateway.envoyproxy.io/gatewayclass-controller
+---
+apiVersion: gateway.networking.k8s.io/v1beta1
+kind: Gateway
+metadata:
+  name: eg
+  namespace: default
+spec:
+  gatewayClassName: eg
+  listeners:
+    - name: http
+      protocol: HTTP
+      port: 80
+---
+apiVersion: gateway.networking.k8s.io/v1beta1
+kind: HTTPRoute
+metadata:
+  name: backend
+  namespace: default
+spec:
+  parentRefs:
+    - name: eg
+  hostnames:
+    - "www.example.com"
+  rules:
+    - backendRefs:
+        - group: multicluster.x-k8s.io
+          kind: ServiceImport
+          name: backend-default-cluster2
+          namespace: submariner-operator
+          port: 3000
+      matches:
+        - path:
+            type: PathPrefix
+            value: /
+---
+apiVersion: gateway.networking.k8s.io/v1alpha2
+kind: ReferenceGrant
+metadata:
+  namespace: submariner-operator
+  name: referencegrant-1
+spec:
+  from:
+    - group: gateway.networking.k8s.io
+      kind: HTTPRoute
+      namespace: default
+  to:
+    - group: multicluster.x-k8s.io
+      kind: ServiceImport

internal/provider/kubernetes/routes.go

@@ -56,7 +56,7 @@ func (r *gatewayAPIReconciler) processTLSRoutes(ctx context.Context, gatewayName
 
 				if backendNamespace != tlsRoute.Namespace {
 					from := ObjectKindNamespacedName{kind: gatewayapi.KindTLSRoute, namespace: tlsRoute.Namespace, name: tlsRoute.Name}
-					to := ObjectKindNamespacedName{kind: gatewayapi.KindService, namespace: backendNamespace, name: string(backendRef.Name)}
+					to := ObjectKindNamespacedName{kind: gatewayapi.KindDerefOr(backendRef.Kind, gatewayapi.KindService), namespace: backendNamespace, name: string(backendRef.Name)}
 					refGrant, err := r.findReferenceGrant(ctx, from, to)
 					switch {
 					case err != nil:
@@ -142,7 +142,7 @@ func (r *gatewayAPIReconciler) processGRPCRoutes(ctx context.Context, gatewayNam
 						name:      grpcRoute.Name,
 					}
 					to := ObjectKindNamespacedName{
-						kind:      gatewayapi.KindService,
+						kind:      gatewayapi.KindDerefOr(backendRef.Kind, gatewayapi.KindService),
 						namespace: backendNamespace,
 						name:      string(backendRef.Name),
 					}
@@ -293,7 +293,7 @@ func (r *gatewayAPIReconciler) processHTTPRoutes(ctx context.Context, gatewayNam
 						name:      httpRoute.Name,
 					}
 					to := ObjectKindNamespacedName{
-						kind:      gatewayapi.KindService,
+						kind:      gatewayapi.KindDerefOr(backendRef.Kind, gatewayapi.KindService),
 						namespace: backendNamespace,
 						name:      string(backendRef.Name),
 					}
@@ -360,7 +360,7 @@ func (r *gatewayAPIReconciler) processHTTPRoutes(ctx context.Context, gatewayNam
 							name:      httpRoute.Name,
 						}
 						to := ObjectKindNamespacedName{
-							kind:      gatewayapi.KindService,
+							kind:      gatewayapi.KindDerefOr(mirrorBackendRef.Kind, gatewayapi.KindService),
 							namespace: backendNamespace,
 							name:      string(mirrorBackendRef.Name),
 						}
@@ -468,7 +468,7 @@ func (r *gatewayAPIReconciler) processTCPRoutes(ctx context.Context, gatewayName
 
 				if backendNamespace != tcpRoute.Namespace {
 					from := ObjectKindNamespacedName{kind: gatewayapi.KindTCPRoute, namespace: tcpRoute.Namespace, name: tcpRoute.Name}
-					to := ObjectKindNamespacedName{kind: gatewayapi.KindService, namespace: backendNamespace, name: string(backendRef.Name)}
+					to := ObjectKindNamespacedName{kind: gatewayapi.KindDerefOr(backendRef.Kind, gatewayapi.KindService), namespace: backendNamespace, name: string(backendRef.Name)}
 					refGrant, err := r.findReferenceGrant(ctx, from, to)
 					switch {
 					case err != nil:
@@ -530,7 +530,7 @@ func (r *gatewayAPIReconciler) processUDPRoutes(ctx context.Context, gatewayName
 
 				if backendNamespace != udpRoute.Namespace {
 					from := ObjectKindNamespacedName{kind: gatewayapi.KindUDPRoute, namespace: udpRoute.Namespace, name: udpRoute.Name}
-					to := ObjectKindNamespacedName{kind: gatewayapi.KindService, namespace: backendNamespace, name: string(backendRef.Name)}
+					to := ObjectKindNamespacedName{kind: gatewayapi.KindDerefOr(backendRef.Kind, gatewayapi.KindService), namespace: backendNamespace, name: string(backendRef.Name)}
 					refGrant, err := r.findReferenceGrant(ctx, from, to)
 					switch {
 					case err != nil: