From: Neal Cardwell <ncardwell@google.com>
Date: Thu, 2 Apr 2015 00:26:46 +0000 (-0400)
Subject: tcp: fix FRTO undo on cumulative ACK of SACKed range
X-Git-Tag: omap-for-v4.1/fixes-rc1~225^2~10
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=666b805150efd62f05810ff0db08f44a2370c937;p=pandora-kernel.git

tcp: fix FRTO undo on cumulative ACK of SACKed range

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@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Fixes: e33099f96d99c ("tcp: implement RFC5682 F-RTO")
Signed-off-by: David S. Miller <davem@davemloft.net>
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