Re: [PATCH net 1/2] virtio-net: disable guest csum during XDP set

[David Miller]

From: Jason Wang <jasowang@xxxxxxxxxx>
Date: Thu, 22 Nov 2018 14:36:30 +0800

> We don't disable VIRTIO_NET_F_GUEST_CSUM if XDP was set. This means we
> can receive partial csumed packets with metadata kept in the
> vnet_hdr. This may have several side effects:
> 
> - It could be overridden by header adjustment, thus is might be not
>   correct after XDP processing.
> - There's no way to pass such metadata information through
>   XDP_REDIRECT to another driver.
> - XDP does not support checksum offload right now.
> 
> So simply disable guest csum if possible in this the case of XDP.
> 
> Fixes: 3f93522ffab2d ("virtio-net: switch off offloads on demand if possible on XDP set")
> Reported-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
> Cc: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
> Cc: Pavel Popa <pashinho1990@xxxxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>

Applied and queued up for -stable.

We really should have a way to use the checksum provided if the XDP
program returns XDP_PASS and does not modify the packet contents
or size.