netdev - Re: [PATCH net-next repost] openvswitch: allow output of MPLS packets on tunnel vports

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Message-Id: <20160318.182756.572852383155549595.davem@davemloft.net>
Date:	Fri, 18 Mar 2016 18:27:56 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	simon.horman@...ronome.com
Cc:	pshelar@....org, jesse@...nel.org, netdev@...r.kernel.org,
	dev@...nvswitch.org
Subject: Re: [PATCH net-next repost] openvswitch: allow output of MPLS
 packets on tunnel vports

From: Simon Horman <simon.horman@...ronome.com>
Date: Tue, 15 Mar 2016 12:00:35 +0900

> Currently output of MPLS packets on tunnel vports is not allowed by Open
> vSwitch. This is because historically encapsulation was done in such a way
> that the inner_protocol field of the skb needed to hold the inner protocol
> for both MPLS and tunnel encapsulation in order for GSO segmentation to be
> performed correctly.
> 
> Since b2acd1dc3949 ("openvswitch: Use regular GRE net_device instead of
> vport") Open vSwitch makes use of lwt to output to tunnel netdevs which
> perform encapsulation. As no drivers expose support for MPLS offloads this
> means that GSO packets are segmented in software by validate_xmit_skb(),
> which is called from __dev_queue_xmit(), before tunnel encapsulation occurs.
> This means that the inner protocol of MPLS is no longer needed by the time
> encapsulation occurs and the contention on the inner_protocol field of the
> skb no longer occurs.
> 
> Thus it is now safe to output MPLS to tunnel vports.
> 
> Signed-off-by: Simon Horman <simon.horman@...ronome.com>

Applied, thanks.