On Mon, Jul 18, 2016 at 7:35 AM, Jesse Gross <je...@kernel.org> wrote:
> On Mon, Jul 18, 2016 at 4:24 AM, Pravin B Shelar <pshe...@ovn.org> wrote:
>> Upstream commit:
>> commit fe3a5f6c795810edb1646a840fec3c8c350c2a4e
>> Author: Simon Horman <simon.hor...@netronome.com>
>>
>> openvswitch: allow output of MPLS packets on tunnel vports
>>
>> 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.hor...@netronome.com>
>> Reviewed-by: Jesse Gross <je...@kernel.org>
>> Signed-off-by: David S. Miller <da...@davemloft.net>
>>
>> Signed-off-by: Pravin B Shelar <pshe...@ovn.org>
>
> I'm still somewhat concerned about this since it makes
> USE_UPSTREAM_TUNNEL effectively a user-facing toggle - the effects of
> it will be visible all the way out to the OpenFlow layer since it will
> be change what flows can be installed (and work). If we need to
> continue to bump up the kernel version where we use our own tunneling
> then it will keep changing whether these flows work.
>
> I think the ideal thing to would be to actually run the offload code
> before transmitting to tunnels. The next best thing would be to enable
> actually using the device layer on tunnels for kernels that support
> lightweight tunnels.
>
I thought about running compat-dev-xmit function here, but it would
complicate code I am not sure if it is worth it.
we can revisit it later on if required.
> I guess both of these are probably disproportionally complicated to
> the actual use case here and this isn't a regression, so for the time
> being:
> Acked-by: Jesse Gross <je...@kernel.org>
Thanks for review. I pushed first four patches to master.
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