apis/nfd/validate: loosen validation of feature annotations

Don't require that the annotation value must conform to the (strict)
requirements of label values. In the Kubernetes API annotation values do
not have other restrictions than that the total size (keys and values)
of _all_ annotations combined of an object must not exceed 256kB.

This patch sets a maximum size limit of 1kB for the value of a single
feature annotation created by NFD. This limit is rather arbitrary but
should be enough for the NFD usage scenarios (until proven wrong).

api/nfd/v1alpha1/annotations_labels.go

@@ -74,4 +74,7 @@ const (
 
 	// FeatureAnnotationSubNsSuffix is the suffix for allowed feature annotation sub-namespaces.
 	FeatureAnnotationSubNsSuffix = "." + FeatureAnnotationNs
+
+	// FeatureAnnotationValueSizeLimit is the maximum allowed length for the value of a feature annotation.
+	FeatureAnnotationValueSizeLimit = 1 << 10
 )

pkg/apis/nfd/validate/validate.go

@@ -155,8 +155,8 @@ func Annotation(key, value string) error {
 	}
 
 	// Validate annotation value
-	if errs := k8svalidation.IsValidLabelValue(value); len(errs) > 0 {
+	if len(value) > nfdv1alpha1.FeatureAnnotationValueSizeLimit {
-		return fmt.Errorf("invalid value %q: %s", value, strings.Join(errs, "; "))
+		return fmt.Errorf("invalid value: too long: feature annotations must not be longer than %d characters", nfdv1alpha1.FeatureAnnotationValueSizeLimit)
 	}
 
 	return nil

pkg/apis/nfd/validate/validate_test.go

@@ -29,8 +29,8 @@ func TestAnnotation(t *testing.T) {
 		{
 			name:  "Invalid annotation value",
 			key:   "feature.node.kubernetes.io/feature",
-			value: "invalid value",
+			value: string(make([]byte, 1100)),
-			want:  "invalid value \"invalid value\": ",
+			want:  "invalid value: too long:",
 		},
 		{
 			name:  "Denied annotation key",