netdev - Re: [PATCH net] tcp: fix cwnd undo on DSACK in F-RTO

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Date:	Mon, 02 Jun 2014 16:51:08 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ycheng@...gle.com
Cc:	ncardwell@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] tcp: fix cwnd undo on DSACK in F-RTO

From: Yuchung Cheng <ycheng@...gle.com>
Date: Fri, 30 May 2014 15:25:59 -0700

> This bug is discovered by an recent F-RTO issue on tcpm list
> https://www.ietf.org/mail-archive/web/tcpm/current/msg08794.html
> 
> The bug is that currently F-RTO does not use DSACK to undo cwnd in
> certain cases: upon receiving an ACK after the RTO retransmission in
> F-RTO, and the ACK has DSACK indicating the retransmission is spurious,
> the sender only calls tcp_try_undo_loss() if some never retransmisted
> data is sacked (FLAG_ORIG_DATA_SACKED).
> 
> The correct behavior is to unconditionally call tcp_try_undo_loss so
> the DSACK information is used properly to undo the cwnd reduction.
> 
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>

Applied and queued up for -stable, thanks.
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