On Thu, Dec 25, 2014 at 3:14 PM, Michael S. Tsirkin <mst@xxxxxxxxxx>
wrote:
On Thu, Dec 25, 2014 at 03:10:01AM +0008, Jason Wang wrote:
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?
But then we'll need to then change it again in step 5,
probably by setting some flag?
The idea is if no segmentation (either software or hardware), no need
for an id.
So looks like dodgy is sufficient since we are sure kernel should set
id in all other cases. And we can add the id only when we see it was
not set for the ufo packet(legacy guest). This seems not conflict with
step 5.
Might as well do it directly.
>
>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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