Do not validate ingresses with unknown ingress class in admission webhook endpoint

internal/ingress/controller/controller.go

@@ -233,6 +233,12 @@ func (n *NGINXController) CheckIngress(ing *networking.Ingress) error {
 		return nil
 	}
 
+	// Do not attempt to validate an ingress that's not meant to be controlled by the current instance of the controller.
+	if ingressClass, err := n.store.GetIngressClass(ing, n.cfg.IngressClassConfiguration); ingressClass == "" {
+		klog.Warningf("ignoring ingress %v in %v based on annotation %v: %v", ing.Name, ing.ObjectMeta.Namespace, ingressClass, err)
+		return nil
+	}
+
 	if n.cfg.Namespace != "" && ing.ObjectMeta.Namespace != n.cfg.Namespace {
 		klog.Warningf("ignoring ingress %v in namespace %v different from the namespace watched %s", ing.Name, ing.ObjectMeta.Namespace, n.cfg.Namespace)
 		return nil

internal/ingress/controller/controller_test.go

@@ -63,6 +63,10 @@ type fakeIngressStore struct {
 	configuration ngx_config.Configuration
 }
 
+func (fakeIngressStore) GetIngressClass(ing *networking.Ingress, icConfig *ingressclass.IngressClassConfiguration) (string, error) {
+	return "nginx", nil
+}
+
 func (fis fakeIngressStore) GetBackendConfiguration() ngx_config.Configuration {
 	return fis.configuration
 }

internal/ingress/controller/store/store.go

@@ -98,6 +98,9 @@ type Storer interface {
 
 	// Run initiates the synchronization of the controllers
 	Run(stopCh chan struct{})
+
+	// GetIngressClass validates given ingress against ingress class configuration and returns the ingress class.
+	GetIngressClass(ing *networkingv1.Ingress, icConfig *ingressclass.IngressClassConfiguration) (string, error)
 }
 
 // EventType type of event associated with an informer

test/e2e/admission/admission.go

@@ -191,6 +191,12 @@ var _ = framework.IngressNginxDescribe("[Serial] admission controller", func() {
 			assert.NotNil(ginkgo.GinkgoT(), err, "creating an ingress with invalid configuration should return an error")
 		}
 	})
+
+	ginkgo.It("should not return an error for an invalid Ingress when it has unknown class", func() {
+		out, err := createIngress(f.Namespace, invalidV1IngressWithOtherClass)
+		assert.Equal(ginkgo.GinkgoT(), "ingress.networking.k8s.io/extensions-invalid-other created\n", out)
+		assert.Nil(ginkgo.GinkgoT(), err, "creating an invalid ingress with unknown class using kubectl")
+	})
 })
 
 func uninstallChart(f *framework.Framework) error {
@@ -270,6 +276,29 @@ spec:
             port:
               number: 80
 ---
+`
+	invalidV1IngressWithOtherClass = `
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: extensions-invalid-other
+  annotations:
+    nginx.ingress.kubernetes.io/configuration-snippet: |
+      invalid directive
+spec:
+  ingressClassName: nginx-other
+  rules:
+  - host: extensions-invalid
+    http:
+      paths:
+      - path: /
+        pathType: Prefix
+        backend:
+          service:
+            name: echo
+            port:
+              number: 80
+---
 `
 )