linux-kernel - Re: [PATCH 3.17 023/319] drivers/net: Disable UFO through virtio

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Date:	Wed, 12 Nov 2014 21:03:59 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 3.17 023/319] drivers/net: Disable UFO through virtio

On Wed, 2014-11-12 at 10:12 +0900, Greg Kroah-Hartman wrote:
> 3.17-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Ben Hutchings <ben@...adent.org.uk>
> 
> [ Upstream commit 3d0ad09412ffe00c9afa201d01effdb6023d09b4 ]
> 
> IPv6 does not allow fragmentation by routers, so there is no
> fragmentation ID in the fixed header.  UFO for IPv6 requires the ID to
> be passed separately, but there is no provision for this in the virtio
> net protocol.
> 
> Until recently our software implementation of UFO/IPv6 generated a new
> ID, but this was a bug.  Now we will use ID=0 for any UFO/IPv6 packet
> passed through a tap, which is even worse.
> 
> Unfortunately there is no distinction between UFO/IPv4 and v6
> features, so disable UFO on taps and virtio_net completely until we
> have a proper solution.
[...]

Please drop this patch for 3.14 and 3.17.  It causes problems for
migration of VMs and we're probably going to revert part of this.  The
following patch ("drivers/net, ipv6: Select IPv6 fragment idents for
virtio UFO packets") might no longer apply, in which case you can drop
that as well until we have this sorted out upstream.

Ben.

-- 
Ben Hutchings
Experience is directly proportional to the value of equipment destroyed.
                                                         - Carolyn Scheppner

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