Re: [PATCH net v4 3/4] virtio-net: correct hdr_len handling for VIRTIO_NET_F_GUEST_HDRLEN

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Nov 10, 2025 at 03:16:08PM +0800, Jason Wang wrote:
> On Mon, Nov 10, 2025 at 5:41 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Thu, Oct 30, 2025 at 10:53:01AM +0800, Jason Wang wrote:
> > > On Wed, Oct 29, 2025 at 11:09 AM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> > > >
> > > > The commit be50da3e9d4a ("net: virtio_net: implement exact header length
> > > > guest feature") introduces support for the VIRTIO_NET_F_GUEST_HDRLEN
> > > > feature in virtio-net.
> > > >
> > > > This feature requires virtio-net to set hdr_len to the actual header
> > > > length of the packet when transmitting, the number of
> > > > bytes from the start of the packet to the beginning of the
> > > > transport-layer payload.
> > > >
> > > > However, in practice, hdr_len was being set using skb_headlen(skb),
> > > > which is clearly incorrect. This commit fixes that issue.
> > >
> > > I still think it would be more safe to check the feature
> >
> > which feature VIRTIO_NET_F_GUEST_HDRLEN ?
> >
> 
> Yes.
> 
> Thanks

Seems more conservative for sure, though an extra mode to maintain isn't
great. Hmm?

-- 
MST