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

[Jason Wang <jasowang@redhat.com>]

On Wed, Jun 4, 2025 at 10:17 PM Bui Quang Minh <minhquangbui99@gmail.com> wrote:
>
> On 6/4/25 07:37, Jason Wang wrote:
> > On Tue, Jun 3, 2025 at 11:07 PM Bui Quang Minh <minhquangbui99@gmail.com> 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. This commit instead returns
> >> XDP_DROP in that case.
> >>
> >> Fixes: 99c861b44eb1 ("virtio_net: xsk: rx: support recv merge mode")
> >> Cc: stable@vger.kernel.org
> >> Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
> >> ---
> >>   drivers/net/virtio_net.c | 11 ++++++++---
> >>   1 file changed, 8 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> >> index e53ba600605a..4c35324d6e5b 100644
> >> --- a/drivers/net/virtio_net.c
> >> +++ b/drivers/net/virtio_net.c
> >> @@ -1309,9 +1309,14 @@ static struct sk_buff *virtnet_receive_xsk_merge(struct net_device *dev, struct
> >>          ret = XDP_PASS;
> > It would be simpler to just assign XDP_DROP here?
> >
> > Or if you wish to stick to the way, we can simply remove this assignment.
>
> This XDP_PASS is returned for the case when there is no XDP program
> binding (!prog).

You're right.

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks

>
> >
> >>          rcu_read_lock();
> >>          prog = rcu_dereference(rq->xdp_prog);
> >> -       /* TODO: support multi buffer. */
> >> -       if (prog && num_buf == 1)
> >> -               ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit, stats);
> >> +       if (prog) {
> >> +               /* TODO: support multi buffer. */
> >> +               if (num_buf == 1)
> >> +                       ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit,
> >> +                                                 stats);
> >> +               else
> >> +                       ret = XDP_DROP;
> >> +       }
> >>          rcu_read_unlock();
> >>
> >>          switch (ret) {
> >> --
> >> 2.43.0
> >>
> > Thanks
> >
>
>
> Thanks,
> Quang Minh.
>
>