+ def IsMacInUse(self, mac):
+ """Predicate: check if the specified MAC is in use in the Ganeti cluster.
+
+ This only checks instances managed by this cluster, it does not
+ check for potential collisions elsewhere.
+
+ """
+ self._OpenConfig()
+ self._ReleaseLock()
+ all_macs = self._AllMACs()
+ return mac in all_macs
+