Backport of NET-4638: when multiple listeners have the same port, only add to K8s Service once into release/1.2.x

.changelog/2413.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+api-gateway: Fix creation of invalid Kubernetes Service when multiple Gateway listeners have the same port.
+```

control-plane/api-gateway/gatekeeper/gatekeeper_test.go

@@ -40,12 +40,19 @@ var (
 			Name:     "Listener 1",
 			Port:     8080,
 			Protocol: "TCP",
+			Hostname: common.PointerTo(gwv1beta1.Hostname("example.com")),
 		},
 		{
 			Name:     "Listener 2",
 			Port:     8081,
 			Protocol: "TCP",
 		},
+		{
+			Name:     "Listener 3",
+			Port:     8080,
+			Protocol: "TCP",
+			Hostname: common.PointerTo(gwv1beta1.Hostname("example.net")),
+		},
 	}
 )
 

control-plane/api-gateway/gatekeeper/service.go

@@ -65,14 +65,22 @@ func (g *Gatekeeper) deleteService(ctx context.Context, gwName types.NamespacedN
 }
 
 func (g *Gatekeeper) service(gateway gwv1beta1.Gateway, gcc v1alpha1.GatewayClassConfig) *corev1.Service {
+	seenPorts := map[gwv1beta1.PortNumber]struct{}{}
 	ports := []corev1.ServicePort{}
 	for _, listener := range gateway.Spec.Listeners {
+		if _, seen := seenPorts[listener.Port]; seen {
+			// We've already added this listener's port to the Service
+			continue
+		}
+
 		ports = append(ports, corev1.ServicePort{
 			Name: string(listener.Name),
 			// only TCP-based services are supported for now
 			Protocol: corev1.ProtocolTCP,
 			Port:     int32(listener.Port),
 		})
+
+		seenPorts[listener.Port] = struct{}{}
 	}
 
 	// Copy annotations from the Gateway, filtered by those allowed by the GatewayClassConfig.