[ovs-dev] [PATCH 3/3] datapath: Add basic MPLS support to kernel

[Jesse Gross]

On Tue, Mar 5, 2013 at 10:03 PM, Simon Horman <horms at verge.net.au> wrote:
> On Tue, Mar 05, 2013 at 11:35:41AM -0800, Jesse Gross wrote:
>> On Tue, Mar 5, 2013 at 10:23 AM, Ben Pfaff <blp at nicira.com> wrote:
>> > On Thu, Feb 28, 2013 at 06:15:09PM +0900, Simon Horman wrote:
>> >> Allow datapath to recognize and extract MPLS labels into flow keys
>> >> and execute actions which push, pop, and set labels on packets.
>> >>
>> >> Based heavily on work by Leo Alterman and Ravi K.
>> >>
>> >> Cc: Ravi K <rkerur at gmail.com>
>> >> Cc: Leo Alterman <lalterman at nicira.com>
>> >> Reviewed-by: Isaku Yamahata <yamahata at valinux.co.jp>
>> >> Signed-off-by: Simon Horman <horms at verge.net.au>
>> >
>> > Jesse needs to review this.
>>
>> I was hoping that Simon would update the patch based on the discussion
>> in the thread before I take another look at it.
>
> Hi Jesse,
>
> I'm not quite sure which issues you would like me to look at.
>
> There are number of changes in v2.20 (this version) of the patch
> which address the very helpful review you supplied.
>
> On my todo list I have the following:
>
> * Exercise checksum code in pop_mpls(), push_mpls() and set_mpls()
>   I am unsure how to pass through or simulate skbs with CHECKSUM_COMPLETE.
> * Enhance core kernel code to handle GSO for MPLS or
>   otherwise deal with accelerations. (Linux network core)
> * Add ETH_TYPE_MIN or similar to Linux network core
> * Enhance ovs-vswitchd to output actions in order to
>   allow use of network_header in the datapath to track the top
>   of the MPLS stack.
>
> I'd appreciate some guidance on how to achieve the first item on the list.

I wouldn't worry that much about it.  There are a few NICs that will
generate packets like this but they are fairly rare at this point and
simulating it seems like more trouble than it is worth.  I'll review
it and that should be good enough.

> And the rest of the items seem like future work to me.
>
> Am I missing some items on my list?

The main one that I was referring to is the last one on the list since
I think that it will allow us to simplify things somewhat.  GSO and
other offloads are also somewhat problematic since it means that until
we have that core kernel support OVS will create invalid packets in
some situations.  The exact same situation happened previously with
vlans, so there is some GSO emulation code in vport-netdev.c.