netdev - Re: [PATCH net v2] gso: Update tunnel segmentation to support Tx checksum offload

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Date:	Wed, 10 Jul 2013 18:43:57 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>,
	Dmitry Kravkov <dmitry@...adcom.com>
Cc:	netdev@...r.kernel.org, stephen@...workplumber.org,
	pshelar@...ira.com, joseph.gasparakis@...el.com, jesse@...ira.com,
	Eilon Greenstein <eilong@...adcom.com>
Subject: Re: [PATCH net v2] gso: Update tunnel segmentation to support Tx
 checksum offload

On Wed, 2013-07-10 at 17:42 -0700, Eric Dumazet wrote:
> On Wed, 2013-07-10 at 17:05 -0700, Alexander Duyck wrote:
> > This change makes it so that the GRE and VXLAN tunnels can make use of Tx
> > checksum offload support provided by some drivers via the hw_enc_features.
> > Without this fix enabling GSO means sacrificing Tx checksum offload and
> > this actually leads to a performance regression as shown below:
> > 
> >             Utilization
> >             Send
> > Throughput  local         GSO
> > 10^6bits/s  % S           state
> >   6276.51   8.39          enabled
> >   7123.52   8.42          disabled
> 
> While testing your patch, I discovered TSO support is completely broken
> on GRE, using bnx2x testbed.
> 
> Oh well.
> 
> It seems Nicira guys do not test a lot their patches.
> 

Receiver receives corrupted frames : IpExtInCsumErrors is increasing

The outer checksum is not correct.

Maybe Dmitry has an idea of what is going on ?

18:36:06.085164 IP (tos 0x0, ttl  64, id 48051, offset 0, flags [DF],
proto: GRE (47), length: 1500, bad cksum 3fad (->40ad)!) 10.246.17.83 >
10.246.17.84: GREv0, Flags [none], length 1480
	IP (tos 0x0, ttl  64, id 48051, offset 0, flags [DF], proto: TCP (6),
length: 1476) 7.7.8.83.52523 > 7.7.8.84.48165: ., cksum 0x88b9
(correct), 1:1425(1424) ack 1 win 449 <nop,nop,timestamp 1901210
83620016>

18:36:06.085165 IP (tos 0x0, ttl  64, id 48051, offset 0, flags [DF],
proto: GRE (47), length: 1500, bad cksum 3fad (->40ad)!) 10.246.17.83 >
10.246.17.84: GREv0, Flags [none], length 1480
	IP (tos 0x0, ttl  64, id 48052, offset 0, flags [DF], proto: TCP (6),
length: 1476) 7.7.8.83.52523 > 7.7.8.84.48165: ., cksum 0x8329
(correct), 1425:2849(1424) ack 1 win 449 <nop,nop,timestamp 1901210
83620016>

18:36:06.085166 IP (tos 0x0, ttl  64, id 48051, offset 0, flags [DF],
proto: GRE (47), length: 1500, bad cksum 3fad (->40ad)!) 10.246.17.83 >
10.246.17.84: GREv0, Flags [none], length 1480
	IP (tos 0x0, ttl  64, id 48053, offset 0, flags [DF], proto: TCP (6),
length: 1476) 7.7.8.83.52523 > 7.7.8.84.48165: ., cksum 0x7d99
(correct), 2849:4273(1424) ack 1 win 449 <nop,nop,timestamp 1901210
83620016>






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