Do not count packets though multicast loopback and simplex interfaces.

Do not count packets though multicast loopback and simplex interfaces.

Counting multicast packets sent to local stack or packets that are
reflected by simplex interfaces does not make much sense.  They are
neither received nor output by any ethernet device.  Counting these
packets at lo0 or the loopback interface of the routing domain would
be possible, but is not worth the effort.  Make if_input_local()
MP safe by deleting the if_opackets++ code.

OK mvs@