netdev - Re: [PATCH net] tcp: do not rearm RTO when future data are sacked

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Date:	Sun, 27 Oct 2013 16:52:05 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	ycheng@...gle.com
Cc:	ncardwell@...gle.com, edumazet@...gle.com, brakmo@...gle.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH net] tcp: do not rearm RTO when future data are sacked

From: Yuchung Cheng <ycheng@...gle.com>
Date: Thu, 24 Oct 2013 08:59:27 -0700

> Patch ed08495c3 "tcp: use RTT from SACK for RTO" always re-arms RTO upon
> obtaining a RTT sample from newly sacked data.
> 
> But technically RTO should only be re-armed when the data sent before
> the last (re)transmission of write queue head are (s)acked. Otherwise
> the RTO may continue to extend during loss recovery on data sent
> in the future.
> 
> Note that RTTs from ACK or timestamps do not have this problem, as the RTT
> source must be from data sent before.
> 
> The new RTO re-arm policy is
> 1) Always re-arm RTO if SND.UNA is advanced
> 2) Re-arm RTO if sack RTT is available, provided the sacked data was
>    sent before the last time write_queue_head was sent.
> 
> Signed-off-by: Larry Brakmo <brakmo@...gle.com>
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>

Also applied and queued up for -stable, thanks!
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