libnm: verify value for connection.mdns

Also, keep the internal variable of type int. The only way to set the
field is via the GObject property setter. At that point, don't yet
cast the integer type to enum.

libnm-core/nm-setting-connection.c

@@ -81,7 +81,7 @@ typedef struct {
 	NMMetered metered;
 	NMSettingConnectionLldp lldp;
 	gint auth_retries;
-	NMSettingConnectionMdns mdns;
+	int mdns;
 } NMSettingConnectionPrivate;
 
 enum {
@@ -1076,6 +1076,17 @@ verify (NMSetting *setting, NMConnection *connection, GError **error)
 		return FALSE;
 	}
 
+	if (   priv->mdns < NM_SETTING_CONNECTION_MDNS_UNKNOWN
+	    || priv->mdns > NM_SETTING_CONNECTION_MDNS_RESOLVE) {
+		g_set_error (error,
+		             NM_CONNECTION_ERROR,
+		             NM_CONNECTION_ERROR_INVALID_PROPERTY,
+		             _("mdns value %d is not valid"), priv->mdns);
+		g_prefix_error (error, "%s.%s: ", NM_SETTING_CONNECTION_SETTING_NAME,
+		                NM_SETTING_CONNECTION_MDNS);
+		return FALSE;
+	}
+
 	/* *** errors above here should be always fatal, below NORMALIZABLE_ERROR *** */
 
 	if (!priv->uuid) {