netdev - Re: [PATCH] tcp: fixing TLP's FIN recovery

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Message-ID: <1402330502.3645.378.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 09 Jun 2014 09:15:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Per Hurtig <per.hurtig@....se>
Cc:	Nandita Dukkipati <nanditad@...gle.com>,
	Netdev <netdev@...r.kernel.org>,
	Anna Brunström <anna.brunstrom@....se>,
	mohammad.rajiullah@....se, Neal Cardwell <ncardwell@...gle.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Subject: Re: [PATCH] tcp: fixing TLP's FIN recovery

On Mon, 2014-06-09 at 17:56 +0200, Per Hurtig wrote:

> 
> Ok, I guess you mean that the retransmission was not fast enough? But 
> will the same not happen if the original FIN is not lost and triggers a 
> SACK (i.e., if the two last data segments are still lost)?

Yes, I'd like to understand why Nandita specifically added the original
test. In her tests, fast retransmit was not really effective.

Running packetdrill in a separate container gives me these interesting
counters :

# nstat
#kernel
IpInReceives                    4                  0.0
IpInDelivers                    4                  0.0
IpOutRequests                   5                  0.0
TcpPassiveOpens                 1                  0.0
TcpInSegs                       4                  0.0
TcpOutSegs                      10                 0.0
TcpRetransSegs                  2                  0.0
TcpExtTCPPureAcks               3                  0.0
TcpExtTCPSackRecovery           1                  0.0
TcpExtTCPFastRetrans            1                  0.0
TcpExtTCPLossProbes             1                  0.0
TcpExtTCPSackRecoveryFail       1                  0.0
TcpExtTCPSackShiftFallback      1                  0.0
TcpExtTCPRetransFail            4                  0.0   <<<< HERE >>>
TcpExtTCPOrigDataSent           9                  0.0
IpExtInOctets                   184                0.0
IpExtOutOctets                  9212               0.0
IpExtInNoECTPkts                4                  0.0

I guess we need to understand why the retransmit is in error.

I am investigating.


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