netdev - [PATCH 0/3] Restore UFO support to virtio

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Date:	Mon, 26 Jan 2015 09:37:03 -0500
From:	Vladislav Yasevich <vyasevich@...il.com>
To:	netdev@...r.kernel.org
Cc:	virtualization@...ts.linux-foundation.org, mst@...hat.com,
	ben@...adent.org.uk, edumazet@...gle.com,
	Vladislav Yasevich <vyasevic@...hat.com>
Subject: [PATCH 0/3] Restore UFO support to virtio_net devices

commit 3d0ad09412ffe00c9afa201d01effdb6023d09b4
Author: Ben Hutchings <ben@...adent.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 reserves a bit in the skb and sets the bit
with the ipv6 fragment id has been generated for the packet.
UFO/GSO code then checks the bit to see if the fragment id
is already present or if a new fragment id needs to be generated.
This solution allows host-originated UFO packets to keep a
better randomized fragment id, as well as generating a randomized
id for VM generated traffic (solving the fragment id 0 issue).

Vladislav Yasevich (3):
  ipv6: Select fragment id during UFO/GSO 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/linux/skbuff.h   |  3 ++-
 include/net/ipv6.h       |  2 ++
 net/ipv6/ip6_output.c    |  4 ++--
 net/ipv6/output_core.c   |  9 ++++++++-
 net/ipv6/udp_offload.c   | 10 +++++++++-
 8 files changed, 50 insertions(+), 43 deletions(-)

-- 
1.9.3

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