networkd(vlan): remove the interface in addition to config (#468)

By only removing the configuration file and reloading it will not
remove the actual interface, for that we need to ask networkd to
actively remove the interface for us.

In order to maintain consistency of what's presend on disk and the
MDS representation + guest agent state we are forcing the removal
of the interface first and then removing the config, in case of
error during networkctl call we keep using the on disk state to
determine what to remove/keep.

google_guest_agent/network/manager/systemd_networkd_linux.go

@@ -337,7 +337,7 @@ func (n *systemdNetworkd) SetupVlanInterface(ctx context.Context, config *cfg.Se
 
 	// Attempt to remove vlan interface configurations that are not known - i.e. they were previously
 	// added by users but are no longer present on their mds configuration.
-	requiresRestart, err := n.removeVlanInterfaces(keepMe)
+	requiresRestart, err := n.removeVlanInterfaces(ctx, keepMe)
 	if err != nil {
 		return fmt.Errorf("failed to remove vlan interface configuration: %+v", err)
 	}
@@ -356,7 +356,7 @@ func (n *systemdNetworkd) SetupVlanInterface(ctx context.Context, config *cfg.Se
 }
 
 // removeVlanInterfaces removes vlan interfaces that are not present in keepMe slice.
-func (n *systemdNetworkd) removeVlanInterfaces(keepMe []string) (bool, error) {
+func (n *systemdNetworkd) removeVlanInterfaces(ctx context.Context, keepMe []string) (bool, error) {
 	files, err := os.ReadDir(n.configDir)
 	if err != nil {
 		return false, fmt.Errorf("failed to read content from %s: %+v", n.configDir, err)
@@ -366,6 +366,9 @@ func (n *systemdNetworkd) removeVlanInterfaces(keepMe []string) (bool, error) {
 	configRegex := regexp.MustCompile(configExp)
 	requiresRestart := false
 
+	var ifacesDeleteMe []string
+	var filesDeleteMe []string
+
 	for _, file := range files {
 		var (
 			currIface, extension string
@@ -414,13 +417,29 @@ func (n *systemdNetworkd) removeVlanInterfaces(keepMe []string) (bool, error) {
 			continue
 		}
 
-		if err := os.Remove(filepath.Join(n.configDir, file.Name())); err != nil {
-			return requiresRestart, fmt.Errorf("failed to remove vlan interface config(%s): %+v", file.Name(), err)
+		if extension == "network" {
+			network := ptr.(*systemdConfig)
+			ifacesDeleteMe = append(ifacesDeleteMe, network.Match.Name)
 		}
 
+		filesDeleteMe = append(filesDeleteMe, filePath)
 		requiresRestart = true
 	}
 
+	if len(ifacesDeleteMe) > 0 {
+		args := []string{"delete"}
+		args = append(args, ifacesDeleteMe...)
+		if err := run.Quiet(ctx, "networkctl", args...); err != nil {
+			return false, fmt.Errorf("networkctl %v failed with error: %w", args, err)
+		}
+	}
+
+	for _, filePath := range filesDeleteMe {
+		if err := os.Remove(filePath); err != nil {
+			return requiresRestart, fmt.Errorf("failed to remove vlan interface config(%s): %+v", filePath, err)
+		}
+	}
+
 	return requiresRestart, nil
 }
 
@@ -590,7 +609,7 @@ func (n *systemdNetworkd) rollbackConfigs(ctx context.Context, nics *Interfaces,
 	vlanRequiresRestart := false
 	// Rollback vlan interfaces.
 	if removeVlan {
-		vlanRequiresRestart, err = n.removeVlanInterfaces(nil)
+		vlanRequiresRestart, err = n.removeVlanInterfaces(ctx, nil)
 		if err != nil {
 			logger.Warningf("Failed to rollback vlan interfaces: %v", err)
 		}