netdev - Re: [PATCH v1 1/6] net: Generalize udp based tunnel offload

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Message-Id: <1449161021.20955.457151201.71B15FA7@webmail.messagingengine.com>
Date:	Thu, 03 Dec 2015 17:43:41 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Andreas Schultz <aschultz@...p.net>,
	Tom Herbert <tom@...bertland.com>
Cc:	"John W. Linville" <linville@...driver.com>,
	Jesse Gross <jesse@...nel.org>,
	David Miller <davem@...emloft.net>,
	Anjali Singhai Jain <anjali.singhai@...el.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Kiran Patil <kiran.patil@...el.com>
Subject: Re: [PATCH v1 1/6] net: Generalize udp based tunnel offload

On Thu, Dec 3, 2015, at 17:35, Andreas Schultz wrote:
> On 12/03/2015 04:59 PM, Hannes Frederic Sowa wrote:
> > Hi Tom,
> >
> > On Wed, Dec 2, 2015, at 20:15, Tom Herbert wrote:
> >> On Wed, Dec 2, 2015 at 8:35 AM, Hannes Frederic Sowa
> >> <hannes@...essinduktion.org> wrote:
> >>> On Wed, Dec 2, 2015, at 04:50, Tom Herbert wrote:
> >>>> That completely misses the whole point of the rest of this thread.
> >>>> Protocol specific offloads are what we are trying to discourage not
> >>>> encourage. Adding any more ndo functions for this purpose should be an
> >>>> exception, not the norm. The bar should be naturally high considering
> >>>> the cost of exposing this to ndo.
> >>>
> >>> Why?
> >>>
> >>> I wonder why we need protocol generic offloads? I know there are
> >>> currently a lot of overlay encapsulation protocols. Are there many more
> >>> coming?
> >>>
> >> Yes, and assume that there are more coming with an unbounded limit
> >> (for instance I just noticed today that there is a netdev1.1 talk on
> >> supporting GTP in the kernel). Besides, this problem space not just
> >> limited to offload of encapsulation protocols, but how to generalize
> >> offload of any transport, IPv[46], application protocols, protocol
> >> implemented in user space, security protocols, etc.
> >
> > GTP seems to be a tunneling protocol also based on TCP, I hope the same
> > standards apply to it as STT at that time (depending on the
> > implementation, of course). There are some other protocols on its way, I
> > see but they can just be realized as kernel modules and that's it.
> 
> GTP is UDP based. The standard permits a variable length header (one can
> add extensions after a fixed header), but that is seldom (or even never)
> used. Tunnel are identified by a 32bit tunnel endpoint id for GTPv1 and
> a 64bit flow id for GTPv0. UDP destination ports differ for v1 and v0,
> so it's easy to distinguish.

Ok, thanks for letting me know. Browsing in Wikipedia first mentioned
both TCP and UDP. But I see that v1 only uses UDP.

Bye,
Hannes
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