netdev - Re: [PATCH v4 net-next] tcp: Change txhash on every SYN and RTO retransmit

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Message-Id: <20160928.075259.495409427572927438.davem@davemloft.net>
Date:   Wed, 28 Sep 2016 07:52:59 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     brakmo@...com
Cc:     netdev@...r.kernel.org, kernel-team@...com, eric.dumazet@...il.com,
        ycheng@...gle.com, ncardwell@...gle.com
Subject: Re: [PATCH v4 net-next] tcp: Change txhash on every SYN and RTO
 retransmit

From: Lawrence Brakmo <brakmo@...com>
Date: Tue, 27 Sep 2016 19:03:37 -0700

> The current code changes txhash (flowlables) on every retransmitted
> SYN/ACK, but only after the 2nd retransmitted SYN and only after
> tcp_retries1 RTO retransmits.
> 
> With this patch:
> 1) txhash is changed with every SYN retransmits
> 2) txhash is changed with every RTO.
> 
> The result is that we can start re-routing around failed (or very
> congested paths) as soon as possible. Otherwise application health
> checks may fail and the connection may be terminated before we start
> to change txhash.
> 
> v4: Removed sysctl, txhash is changed for all RTOs
> v3: Removed text saying default value of sysctl is 0 (it is 100)
> v2: Added sysctl documentation and cleaned code
> 
> Tested with packetdrill tests
> 
> Signed-off-by: Lawrence Brakmo <brakmo@...com>

Applied, thanks.