Re: [virtio-dev] Re: [virtio-comment] Re: [PATCH v5] virtio-net: device does not deliver partially checksummed packet and may validate the checksum

[Jason Wang <jasowang@redhat.com>]

On Wed, Dec 20, 2023 at 3:35âPM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Wed, Dec 20, 2023 at 02:30:01PM +0800, Heng Qi wrote:
> > But why are we discussing this?
>
> I think basically at this point everyone is confused about what
> the feature does. right now we have packets
> with
> #define VIRTIO_NET_HDR_F_NEEDS_CSUM     1       -> partial
> #define VIRTIO_NET_HDR_F_DATA_VALID     2       -> unnecessary
> and packets without either                      -> none
>
> if both 1 and 2 are set then linux uses VIRTIO_NET_HDR_F_NEEDS_CSUM but
> I am not sure it's not a mistake. Maybe it does not matter.
>
> What does this new thing do? So far all we have is "XDP will turn it on"
> which is not really sufficient. I assumed it somehow replaces
> partial with complete.

It looks not? CHECKSUM_COMPLETE is less optimal than
CHECKSUM_UNNCESSARY as validation is still needed.

If I understand correctly, this new thing wants DATA_VALID only.

Thanks



> That would make sense for many reasons,
> for example the checksum fields in the header can be reused
> for other purposes. But maybe not?
>
>
> --
> MST
>