Improve DNS documentation (#6479)

test/examples_test.go

@@ -32,6 +32,7 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/validation/field"
 	"k8s.io/apimachinery/pkg/util/yaml"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/kubernetes/pkg/api/testapi"
 	"k8s.io/kubernetes/pkg/apis/apps"
 	apps_validation "k8s.io/kubernetes/pkg/apis/apps/validation"
@@ -53,6 +54,8 @@ import (
 )
 
 func validateObject(obj runtime.Object) (errors field.ErrorList) {
+	// Enable CustomPodDNS for testing
+	utilfeature.DefaultFeatureGate.Set("CustomPodDNS=true")
 	switch t := obj.(type) {
 	case *api.ReplicationController:
 		if t.Namespace == "" {
@@ -285,6 +288,7 @@ func TestExampleObjectSchemas(t *testing.T) {
 		},
 		"../docs/concepts/services-networking": {
 			"curlpod":          {&extensions.Deployment{}},
+			"custom-dns":		{&api.Pod{}},
 			"hostaliases-pod":  {&api.Pod{}},
 			"ingress":          {&extensions.Ingress{}},
 			"nginx-secure-app": {&api.Service{}, &extensions.Deployment{}},