ether_demux does not handle frames with embedded vlan tags

[rozhuk.im at gmail.com]

> > In what cases vlan-tagged packet can be received by
> ng_ether_rcv_upper ?
> 
> If another node attaches to an ng_ether node's upper hook and sends a
> vlan tagged packet to the hook.

This may be a wrong configuration or QinQ: packet may have M_VLAN tag is
set and still vlan-tagged (ether_type = VLAN)

--
Rozhuk Ivan