On Thu, Dec 25, 2014 at 2:59 AM, Michael S. Tsirkin <mst@xxxxxxxxxx>
wrote:
On Wed, Dec 24, 2014 at 07:11:20PM +0100, Ben Hutchings wrote:
On Thu, 2014-12-18 at 00:28 -0500, Jason Wang wrote:
>
> ----- Original Message -----
> > UFO support in the kernel applies to both IPv4 and IPv6
protocols
> > with the same device feature. However some devices may not be
able
> > to support one of the offloads. For this we split the UFO
offload
> > feature into 2 pieces. NETIF_F_UFO now controlls the IPv4 part
and
> > this series introduces NETIF_F_UFO6.
> >
> > As a result of this work, we can now re-enable NETIF_F_UFO on
> > virtio_net devices and restore UDP over IPv4 performance for
guests.
> > We also continue to support legacy guests that assume that UFO6
> > support included into UFO(4).
> >
> > Without this work, migrating a guest to a 3.18 kernel fails.
> >
>
> This series eliminate the ambiguous NETIF_F_UFO.
>
> But VIRTIO_NET_F_{HOST|GUEST}_UFO and VIRTIO_NET_F_HDR_GSO_UDP is
still
> ambigious. I know it was used to keep compatibility for legacy
guest. But
> what's the future plan? Differentiate UFOv4 and UFOv6 in virtio
features and
> gso type in vnet header looks sufficient?
[...]
The IPv6 fragmentation ID needs to be added to the vnet header, to
do
UFOv6 properly. If it wasn't for that lack, we wouldn't have to
split
the feature flag.
Ben.
Right.
I think a good plan is as follows:
1. add code generating IDs on rx path for virtio,
and re-enable UFO (4+6).
2. Ben's patch doing similar things for tun/macvtap
I wonder whether or not we can do this lazily.
E.g during UFO6 software segment for dodgy packets?
And this can eliminate the effort of duplicating it in all untrusted
sources?
3. similarly for packet sockets
above seem appropriate for stable
4. 4+6 split, to make it easier for drivers
to identify when fragment ID is needed
5. extend vnet header, and add ways to enable it,
when enabled, use that to pass
fragment ID for tun/virtio/vhost/macvtap/packet socket
4 is what this patchset does.
--
Ben Hutchings
If more than one person is responsible for a bug, no one is at
fault.
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