block not allowed node labels on kubelet

cmd/kubelet/app/options/options.go

@@ -30,7 +30,6 @@ import (
 	"k8s.io/apimachinery/pkg/util/sets"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	cliflag "k8s.io/component-base/cli/flag"
-	"k8s.io/klog"
 	"k8s.io/kubelet/config/v1beta1"
 	"k8s.io/kubernetes/pkg/apis/core"
 	"k8s.io/kubernetes/pkg/features"
@@ -247,9 +246,7 @@ func ValidateKubeletFlags(f *KubeletFlags) error {
 		}
 	}
 	if len(unknownLabels) > 0 {
-		// TODO(liggitt): in 1.16, return an error
+		return fmt.Errorf("unknown 'kubernetes.io' or 'k8s.io' labels specified with --node-labels: %v\n--node-labels in the 'kubernetes.io' namespace must begin with an allowed prefix (%s) or be in the specifically allowed set (%s)", unknownLabels.List(), strings.Join(kubeletapis.KubeletLabelNamespaces(), ", "), strings.Join(kubeletapis.KubeletLabels(), ", "))
-		klog.Warningf("unknown 'kubernetes.io' or 'k8s.io' labels specified with --node-labels: %v", unknownLabels.List())
-		klog.Warningf("in 1.16, --node-labels in the 'kubernetes.io' namespace must begin with an allowed prefix (%s) or be in the specifically allowed set (%s)", strings.Join(kubeletapis.KubeletLabelNamespaces(), ", "), strings.Join(kubeletapis.KubeletLabels(), ", "))
 	}
 
 	return nil

cmd/kubelet/app/options/options_test.go

@@ -145,3 +145,48 @@ func asArgs(fn, defaultFn func(*pflag.FlagSet)) []string {
 	})
 	return args
 }
+
+func TestValidateKubeletFlags(t *testing.T) {
+	tests := []struct {
+		name   string
+		error  bool
+		labels map[string]string
+	}{
+		{
+			name:  "Invalid kubernetes.io label",
+			error: true,
+			labels: map[string]string{
+				"beta.kubernetes.io/metadata-proxy-ready": "true",
+			},
+		},
+		{
+			name:  "Valid label outside of kubernetes.io and k8s.io",
+			error: false,
+			labels: map[string]string{
+				"cloud.google.com/metadata-proxy-ready": "true",
+			},
+		},
+		{
+			name:   "Empty label list",
+			error:  false,
+			labels: map[string]string{},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := ValidateKubeletFlags(&KubeletFlags{
+				NodeLabels: tt.labels,
+			})
+
+			if tt.error && err == nil {
+				t.Errorf("ValidateKubeletFlags should have failed with labels: %+v", tt.labels)
+			}
+
+			if !tt.error && err != nil {
+				t.Errorf("ValidateKubeletFlags should not have failed with labels: %+v", tt.labels)
+			}
+		})
+	}
+
+}