control_iface join with node_types, since new nodes have more
       than just expt and ctrl interfaces (ixps). The control_net slot
       is bogus anyway. Note that 'jail' is a placeholder for later.
       A 'fake' interface is not to be confused with veth interfaces; it
       is a psuedo interface like that found between an ixp and the host.

       alter table interfaces add \
		role enum('ctrl', 'expt', 'jail', 'fake', 'other') \
		NOT NULL default 'other' after iface;