source/system: advertise major and minor OS version

README.md

@@ -299,10 +299,12 @@ for more information on NFD config.
 
 ### System Features
 
-| Feature     | Attribute  | Description                                       |
-| ----------- | ---------- | --------------------------------------------------|
-| os_release  | ID         | Operating system identifier
-| <br>        | VERSION_ID | Operating system version identifier
+| Feature     | Attribute        | Description                                 |
+| ----------- | ---------------- | --------------------------------------------|
+| os_release  | ID               | Operating system identifier
+| <br>        | VERSION_ID       | Operating system version identifier (e.g. '6.7')
+| <br>        | VERSION_ID.major | First component of the OS version id (e.g. '6')
+| <br>        | VERSION_ID.minor | Second component of the OS version id (e.g. '7')
 
 ## Getting started
 ### System requirements

source/system/system.go

@@ -45,7 +45,15 @@ func (s Source) Discover() (source.Features, error) {
 	} else {
 		for _, key := range osReleaseFields {
 			if value, exists := release[key]; exists {
-				features["os_release."+key] = value
+				feature := "os_release." + key
+				features[feature] = value
+
+				if key == "VERSION_ID" {
+					versionComponents := splitVersion(value)
+					for subKey, subValue := range versionComponents {
+						features[feature+"."+subKey] = subValue
+					}
+				}
 			}
 		}
 	}
@@ -74,3 +82,19 @@ func parseOSRelease() (map[string]string, error) {
 
 	return release, nil
 }
+
+// Split version number into sub-components. Verifies that they are numerical
+// so that they can be fully utilized in k8s nodeAffinity
+func splitVersion(version string) map[string]string {
+	components := map[string]string{}
+	// Currently, split out just major and minor version
+	re := regexp.MustCompile(`^(?P<major>\d+)(\.(?P<minor>\d+))?(\..*)?$`)
+	if m := re.FindStringSubmatch(version); m != nil {
+		for i, name := range re.SubexpNames() {
+			if i != 0 && name != "" {
+				components[name] = m[i]
+			}
+		}
+	}
+	return components
+}