netdev - Re: [PATCH net-next] ipv6: gro: support sit protocol

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Date:	Wed, 04 Nov 2015 13:19:43 +0100
From:	Wolfgang Walter <linux@...m.de>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, Jerry Chu <hkchu@...gle.com>,
	JesseGross <jesse@...ira.com>, Tom Herbert <tom@...bertland.com>,
	netdev <netdev@...r.kernel.org>, kernel-team@...com,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH net-next] ipv6: gro: support sit protocol

Am Dienstag, 3. November 2015, 05:07:33 schrieb Eric Dumazet:
> On Tue, 2015-11-03 at 13:57 +0100, Wolfgang Walter wrote:
> > Am Montag, 19. Oktober 2015, 20:40:17 schrieb Eric Dumazet:
> > > From: Eric Dumazet <edumazet@...gle.com>
> > > 
> > > Tom Herbert added SIT support to GRO with commit
> > > 19424e052fb4 ("sit: Add gro callbacks to sit_offload"),
> > > later reverted by Herbert Xu.
> > > 
> > > The problem came because Tom patch was building GRO
> > > packets without proper meta data : If packets were locally
> > > delivered, we would not care.
> > > 
> > > But if packets needed to be forwarded, GSO engine was not
> > > able to segment individual segments.
> > > 
> > > With the following patch, we correctly set skb->encapsulation
> > > and inner network header. We also update gso_type.
> > 
> > I'm running 4.1.11 / 4.1.12 with this patch on top now since over a week.
> > ISATAP works fine.
> 
> Perfect ! thanks a lot for testing !

Today I found a problem: on a router forwarding GRE-packets (ipv4) (it is not 
the endpount) the interface (intel igb) stops sending packets after some time. 
I think this happens when an ISATAP packet is inside the GRE-packet.

	gre packets arrives on eth0
	eth1 stops sending (receiving still works)
	ethtool -r eth1
	eth1 works again for some time

Switching GRO off on eth0 "fixes" the problem.

I didn't test vanilla 4.1.12 yet, though. Until today 4.1.11 has been running 
on the router. What I tested was your patch
	"gre_gso_segment() chokes if SIT frames were aggregated by GRO engine."
but did not solve the problem.

So I would not recommend to backport it to longterm 4.1.

My plans are:

* test vanilla 4.1.12
* test 4.3

I want to test 4.3 on another router first, though.

Regards,
-- 
Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts
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