veb interface

WARNING: The veb(4) man page says:
     The veb pseudo-device supports the creation of a single layer 2 Ethernet
     network between multiple ports.  Ethernet interfaces are added to the
     veb bridge to be used as ports.  Unlike bridge(4), veb takes over the
     operation of the interfaces that are added as ports.  They are then
     independent of the host network stack: the individual Ethernet ports no
     longer function as independent devices and cannot be configured with
     inet(4) or inet6(4) addresses or other layer-3 features themselves.