Subject: Re: [PATCH] virtio_net: Fix MAX_PACKET_LEN to support 802.1Q VLANs

From: Mark McLoughlin <[email-masked]>
Date: Tue, 20 Jan 2009 16:59:26 +0000

On Tue, 2009-01-20 at 09:48 -0700, Alex Williamson wrote:

> 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: Alex Williamson <[email-masked]>

Acked-by: Mark McLoughlin <[email-masked]>

Note 1: this only matters if the guest isn't using mergeable receive
buffers or GSO

Note 2: IMHO, this should go in 2.6.29 and stable

Cheers,
Mark.