netdev - Re: [PATCH net] tcp: fix FRTO undo on cumulative ACK of SACKed range

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Date:	Thu, 02 Apr 2015 16:36:57 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	ncardwell@...gle.com
Cc:	netdev@...r.kernel.org, ycheng@...gle.com
Subject: Re: [PATCH net] tcp: fix FRTO undo on cumulative ACK of SACKed
 range

From: Neal Cardwell <ncardwell@...gle.com>
Date: Wed,  1 Apr 2015 20:26:46 -0400

> On processing cumulative ACKs, the FRTO code was not checking the
> SACKed bit, meaning that there could be a spurious FRTO undo on a
> cumulative ACK of a previously SACKed skb.
> 
> The FRTO code should only consider a cumulative ACK to indicate that
> an original/unretransmitted skb is newly ACKed if the skb was not yet
> SACKed.
> 
> The effect of the spurious FRTO undo would typically be to make the
> connection think that all previously-sent packets were in flight when
> they really weren't, leading to a stall and an RTO.
> 
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Fixes: e33099f96d99c ("tcp: implement RFC5682 F-RTO")

Applied and queued up for -stable, thanks Neal.
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