Re: [PATCH v2 0/3] Restore UFO support to virtio_net devices

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

On Fri, Jan 30, 2015 at 02:27:24PM -0500, Vladislav Yasevich wrote:
> commit 3d0ad09412ffe00c9afa201d01effdb6023d09b4
> Author: Ben Hutchings <ben@decadent.org.uk>
> Date:   Thu Oct 30 18:27:12 2014 +0000
> 
>     drivers/net: Disable UFO through virtio
> 
> Turned off UFO support to virtio-net based devices due to issues
> with IPv6 fragment id generation for UFO packets.  The issue
> was that IPv6 UFO/GSO implementation expects the fragment id
> to be supplied in skb_shinfo().  However, for packets generated
> by the VMs, the fragment id is not supplied which causes all
> IPv6 fragments to have the id of 0.
> 
> The problem is that turning off UFO support on tap/macvtap
> as well as virtio devices caused issues with migrations.  
> Migrations would fail when moving a vm from a kernel supporting
> expecting UFO to work to the newer kernels that disabled UFO.
> 
> This series provides a partial solution to address the migration
> issue.  The series allows us to track whether skb_shinfo()->ip6_frag_id
> has been set by treating value of 0 as unset.
> This lets GSO code to generate fragment ids if they are necessary
> (ex: packet was generated by VM or packet socket).
> 
> Since v1:
>   - Removed the skb bit and use value of 0 as tracker.
>   - Used Eric's suggestion to set fragment id as 0x80000000 if id
>     generation procedure yeilded a 0 result.
>   - Consolidated ipv6 id genration code.


Looks good to me
Acked-by: Michael S. Tsirkin <mst@redhat.com>

Seems appropriate for stable as well.

> Vladislav Yasevich (3):
>   ipv6: Select fragment id during UFO segmentation if not set.
>   Revert "drivers/net, ipv6: Select IPv6 fragment idents for virtio UFO
>     packets"
>   Revert "drivers/net: Disable UFO through virtio"
> 
>  drivers/net/macvtap.c    | 16 ++++++++--------
>  drivers/net/tun.c        | 25 +++++++++----------------
>  drivers/net/virtio_net.c | 24 ++++++++++--------------
>  include/net/ipv6.h       |  3 +++
>  net/ipv6/ip6_output.c    | 10 ++++------
>  net/ipv6/output_core.c   | 28 ++++++++++++++++++++++------
>  net/ipv6/udp_offload.c   | 10 +++++++++-
>  7 files changed, 65 insertions(+), 51 deletions(-)
> 
> -- 
> 1.9.3