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

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.

    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