From: Yuchung Cheng <ycheng@google.com>
Date: Fri, 30 May 2014 22:25:59 +0000 (-0700)
Subject: tcp: fix cwnd undo on DSACK in F-RTO
X-Git-Tag: omap-for-v3.16/fixes-against-rc1~107^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0cfa5c07d6d1d7f8e710fc671c5ba1ce85e09fa4;p=pandora-kernel.git

tcp: fix cwnd undo on DSACK in F-RTO

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@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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