Same as JGRP-2535, but in TUNNEL instead of TCPPING. The problem is that this is not a discovery protocol, where discovery is triggered preiodically by MERGE2, so we have a chance of resolving previously unresolved hostnames: in TUNNEL, the hostnames are only resolved at connect time.
So we probably need a timer task, running every N seconds, until all unresolved hostname have been resolved and the stubs created.