From: Eric Dumazet <[email protected]>
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 <[email protected]>
> Reported-by: Venkat Venkatsubra <[email protected]>
Applied and queued up for -stable, thanks Eric.
