netdev - Re: [PATCH v2.62] datapath: Add basic MPLS support to kernel

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Date:	Wed, 25 Jun 2014 10:51:52 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	Jesse Gross <jesse@...ira.com>
Cc:	"dev@...nvswitch.org" <dev@...nvswitch.org>,
	netdev <netdev@...r.kernel.org>, Ravi K <rkerur@...il.com>,
	Joe Stringer <joe@...d.net.nz>, Thomas Graf <tgraf@...g.ch>
Subject: Re: [PATCH v2.62] datapath: Add basic MPLS support to kernel

On Tue, Jun 24, 2014 at 04:24:37PM -0700, Jesse Gross wrote:
> On Tue, Jun 24, 2014 at 4:56 AM, Simon Horman <horms@...ge.net.au> 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, Ravi K, Isaku Yamahata and Joe Stringer.
> >
> > Cc: Ravi K <rkerur@...il.com>
> > Cc: Leo Alterman <lalterman@...ira.com>
> > Cc: Isaku Yamahata <yamahata@...inux.co.jp>
> > Cc: Joe Stringer <joe@...d.net.nz>
> > Signed-off-by: Simon Horman <horms@...ge.net.au>
> 
> Applied, thanks for all your work. Time to break out the champagne :)

Thanks, a moment for many to savour.

> That being said, I do have a couple of comments for follow up discussion:
>  * I removed the addition of MPLS to key_attr_size. This is trying to
> calculate the maximum key size and since MPLS will never show up in
> conjunction with IPv6 (the current longest key) and isn't longer than
> it, MPLS shouldn't increase the maximum size.

Thanks, sorry for messing that up.

>  * I think there is a potential for MPLS packets to be incorrectly
> offloaded on kernels 3.12-3.15 when encapsulated inside a tunnel. This
> is because it won't hit either the OVS GSO code or your enhanced MPLS
> feature check. I don't want to lose GSO for tunnels on those kernels
> but maybe there is a way to avoid this potential problem without too
> much work.

I'll take a look into this unless someone else wants to jump in.

>  * Maybe you can refresh my memory - in the case of a push_mpls after
> pop_vlan, why can't we do this check correctly for at least one level
> of vlan? It seems like we could use the inner EtherType to tell
> whether an additional vlan tag is present.

That seems likely. I'll do some analysis and get back to you.
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