netdev - Re: [PATCH 00/10] Split UFO into v4 and v6 versions.

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Message-Id: <1419476521.27992.1@smtp.corp.redhat.com>
Date:	Thu, 25 Dec 2014 03:10:01 +0008
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Ben Hutchings <ben@...adent.org.uk>,
	Vladislav Yasevich <vyasevich@...il.com>,
	netdev@...r.kernel.org, stefanha@...hat.com,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 00/10] Split UFO into v4 and v6 versions.



On Thu, Dec 25, 2014 at 2:59 AM, Michael S. Tsirkin <mst@...hat.com> 
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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