802.1Q expanded the maximum ethernet frame size by 4 bytes for the
VLAN tag.  We're not taking this into account in virtio_net, which
means the buffers we provide to the backend in the virtqueue RX ring
aren't big enough to hold a full MTU VLAN packet.  For QEMU/KVM,
this results in the backend exiting with a packet truncation error.
Signed-off-by: NAlex Williamson <alex.williamson@hp.com>
Acked-by: NMark McLoughlin <markmc@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>