Re: [PATCH net] virtio-net: drop the multi-buffer XDP packet in zerocopy

[Bui Quang Minh <minhquangbui99@gmail.com>]

On 6/5/25 18:03, Paolo Abeni wrote:
> On 6/3/25 5:06 PM, Bui Quang Minh wrote:
>> In virtio-net, we have not yet supported multi-buffer XDP packet in
>> zerocopy mode when there is a binding XDP program. However, in that
>> case, when receiving multi-buffer XDP packet, we skip the XDP program
>> and return XDP_PASS. As a result, the packet is passed to normal network
>> stack which is an incorrect behavior.
> Why? AFAICS the multi-buffer mode depends on features negotiation, which
> is not controlled by the VM user.
>
> Let's suppose the user wants to attach an XDP program to do some per
> packet stats accounting. That suddenly would cause drop packets
> depending on conditions not controlled by the (guest) user. It looks
> wrong to me.

But currently, if a multi-buffer packet arrives, it will not go through 
XDP program so it doesn't increase the stats but still goes to network 
stack. So I think it's not a correct behavior.

>
> XDP_ABORTED looks like a better choice.
>
> /P
>

Thanks,
Quang Minh.