to interfaces) so that we return the MAC of the virtual interface not
the physical interface.  I do not much like this arrangement.  We
store veth interfaces in another dynamic table, so must join with both
interfaces and veth_interfaces to see which iface each linkdelay
corresponds to. If there is a veth entry use that, else use the normal
interfaces entry. Maybe we should use the regular interfaces table,
with type veth, entries added/deleted on the fly. I avoided that cause
I view the interfaces table as static and pertaining to physical
interfaces only, but the current arrangement does not scale well
(although if it only ever has to scale to veth_interfaces, so be it).