Add support for IngressClass and ingress.class annotation

internal/ingress/annotations/class/main.go

@@ -18,6 +18,7 @@ package class
 
 import (
 	networking "k8s.io/api/networking/v1beta1"
+	"k8s.io/ingress-nginx/internal/k8s"
 )
 
 const (
@@ -41,25 +42,25 @@ var (
 // the ingress.class annotation, or it's set to the configured in the
 // ingress controller.
 func IsValid(ing *networking.Ingress) bool {
-	className := ing.Spec.IngressClassName
+	ingress, ok := ing.GetAnnotations()[IngressKey]
+	if ok {
+		// we have 2 valid combinations
+		// 1 - ingress with default class | blank annotation on ingress
+		// 2 - ingress with specific class | same annotation on ingress
+		//
+		// and 2 invalid combinations
+		// 3 - ingress with default class | fixed annotation on ingress
+		// 4 - ingress with specific class | different annotation on ingress
+		if ingress == "" && IngressClass == DefaultClass {
+			return true
+		}
 
-	// we have 2 valid combinations
-	// 1 - ingress with default class | blank annotation on ingress
-	// 2 - ingress with specific class | same annotation on ingress
-	//
-	// and 2 invalid combinations
-	// 3 - ingress with default class | fixed annotation on ingress
-	// 4 - ingress with specific class | different annotation on ingress
-	if className != nil {
-		return *className == IngressClass
+		return ingress == IngressClass
 	}
 
-	if IngressClass == DefaultClass {
-		return true
-	}
-
-	if IngressClass == "" {
-		return true
+	// Not running k8s v1.18 or higher and not annotation
+	if !k8s.IsIngressV1Ready {
+		return IngressClass == DefaultClass
 	}
 
 	return false