netdev - Re: [PATCH net] tcp: grow window for OOO packets only for SACK flows

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Message-Id: <20200616.133903.1424216259218078379.davem@davemloft.net>
Date:   Tue, 16 Jun 2020 13:39:03 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        ncardwell@...gle.com, ycheng@...gle.com,
        venkat.x.venkatsubra@...cle.com
Subject: Re: [PATCH net] tcp: grow window for OOO packets only for SACK
 flows

From: Eric Dumazet <edumazet@...gle.com>
Date: Mon, 15 Jun 2020 20:37:07 -0700

> Back in 2013, we made a change that broke fast retransmit
> for non SACK flows.
> 
> Indeed, for these flows, a sender needs to receive three duplicate
> ACK before starting fast retransmit. Sending ACK with different
> receive window do not count.
> 
> Even if enabling SACK is strongly recommended these days,
> there still are some cases where it has to be disabled.
> 
> Not increasing the window seems better than having to
> rely on RTO.
> 
> After the fix, following packetdrill test gives :
 ...
> Fixes: 4e4f1fc22681 ("tcp: properly increase rcv_ssthresh for ofo packets")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>

Applied and queued up for -stable, thanks Eric.