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From: "Yang, Yi" <yi.y.yang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH net-next v6 3/3] openvswitch: enable NSH
	support
Date: Wed, 6 Sep 2017 19:03:54 +0800
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To: Hannes Frederic Sowa <hannes-tFNcAqjVMyqKXQKiL6tip0B+6BGkLq7r@public.gmane.org>
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On Wed, Sep 06, 2017 at 04:03:29PM +0800, Hannes Frederic Sowa wrote:
> "Yang, Yi" <yi.y.yang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> writes:
> >> 
> >> > If you check GENEVE implementation, tun_metadata* can be set or matched
> >> > as any other match field.
> >> 
> >> Yes, I wrote that in my previous mail. I wonder why NSH context metadata
> >> is not in tun_metadata as well?
> >
> > tun_metadata is tunnel metadata, GENEVE needs tunnel port, but NSH is
> > not so, NSH can't directly use tun_metadata, for MD type 2, we need to a
> > lot of rework on tun_metadata to make it shared between GENEVE and NSH,
> > I don't think this can happen in near term. So tun_metadata isn't option
> > for this now.
> 
> Sorry, I couldn't follow you. Why can't you store the context headers in
> tun_metadata exactly?

tun_metadata can work only if in_port and out_port are GENEVE tunnel
port, it is designed specially for GENEVE, Eth+NSH can work without
any tunnel port involved, context headers for NSH are not tunnel
metadata, they aren't tunnel-specific, you can't treat them as same
thing. In addtition, tun_metadata also can be matched and set, they have
the same issue as you concern.

> 
> [...]
> 
> Bye,
> Hannes