[backport release/3.0.x] fix: Ingress with default backend targeting the same Service (#5188) (#5219)

Author: programmer04

internal/dataplane/parser/translate_ingress.go

@@ -64,6 +64,11 @@ func (p *Parser) ingressRulesFromIngressV1() ingressRules {
 	// Add a default backend if it exists.
 	defaultBackendService, ok := getDefaultBackendService(allDefaultBackends, p.featureFlags.ExpressionRoutes)
 	if ok {
+		// When such service would overwrite an existing service, merge the routes.
+		if svc, ok := result.ServiceNameToServices[*defaultBackendService.Name]; ok {
+			svc.Routes = append(svc.Routes, defaultBackendService.Routes...)
+			defaultBackendService = svc
+		}
 		result.ServiceNameToServices[*defaultBackendService.Name] = defaultBackendService
 		result.ServiceNameToParent[*defaultBackendService.Name] = defaultBackendService.Parent
 	}

test/integration/ingress_test.go

@@ -151,6 +151,48 @@ func TestIngressEssentials(t *testing.T) {
 	helpers.EventuallyExpectHTTP404WithNoRoute(t, proxyURL, proxyURL.Host, "/test_ingress_essentials", ingressWait, waitTick, nil)
 }
 
+func TestIngressDefaultBackend(t *testing.T) {
+	ctx := context.Background()
+	ns, cleaner := helpers.Setup(ctx, t, env)
+
+	t.Log("deploying a minimal HTTP container deployment to test Ingress routes")
+	container := generators.NewContainer("httpbin", test.HTTPBinImage, test.HTTPBinPort)
+	deployment := generators.NewDeploymentForContainer(container)
+	deployment, err := env.Cluster().Client().AppsV1().Deployments(ns.Name).Create(ctx, deployment, metav1.CreateOptions{})
+	require.NoError(t, err)
+	cleaner.Add(deployment)
+
+	t.Logf("exposing deployment %s via service", deployment.Name)
+	service := generators.NewServiceForDeployment(deployment, corev1.ServiceTypeLoadBalancer)
+	_, err = env.Cluster().Client().CoreV1().Services(ns.Name).Create(ctx, service, metav1.CreateOptions{})
+	require.NoError(t, err)
+	cleaner.Add(service)
+
+	t.Logf("creating an ingress for service %s with ingress.class %s", service.Name, consts.IngressClass)
+	ingress := generators.NewIngressForService("/foo", map[string]string{
+		"konghq.com/strip-path": "true",
+	}, service)
+	ingress.Spec.IngressClassName = kong.String(consts.IngressClass)
+	ingress.Spec.DefaultBackend = &netv1.IngressBackend{
+		Service: &netv1.IngressServiceBackend{
+			Name: service.Name,
+			Port: netv1.ServiceBackendPort{
+				Number: service.Spec.Ports[0].Port,
+			},
+		},
+	}
+	require.NoError(t, clusters.DeployIngress(ctx, env.Cluster(), ns.Name, ingress))
+	cleaner.Add(ingress)
+
+	t.Log("matching path")
+	helpers.EventuallyGETPath(t, nil, proxyURL.String(), "/foo", http.StatusOK, "<title>httpbin.org</title>", nil, ingressWait, waitTick)
+
+	t.Log("non matching path - use default backend")
+	helpers.EventuallyGETPath(
+		t, nil, proxyURL.String(), fmt.Sprintf("/status/%d", http.StatusTeapot), http.StatusTeapot, "", nil, ingressWait, waitTick,
+	)
+}
+
 func TestGRPCIngressEssentials(t *testing.T) {
 	t.Parallel()