Patch "tcp_bbr: reset full pipe detection on loss recovery undo" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

tcp_bbr: reset full pipe detection on loss recovery undo

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tcp_bbr-reset-full-pipe-detection-on-loss-recovery-undo.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Neal Cardwell <[email protected]>
Date: Thu, 7 Dec 2017 12:43:31 -0500
Subject: tcp_bbr: reset full pipe detection on loss recovery undo

From: Neal Cardwell <[email protected]>

[ Upstream commit 2f6c498e4f15d27852c04ed46d804a39137ba364 ]

Fix BBR so that upon notification of a loss recovery undo BBR resets the full pipe detection (STARTUP exit) state machine.

Under high reordering, reordering events can be interpreted as loss. If the reordering and spurious loss estimates are high enough, this could previously cause BBR to spuriously estimate that the pipe is full.

Since spurious loss recovery means that our overall sending will have slowed down spuriously, this commit gives a flow more time to probe robustly for bandwidth and decide the pipe is really full.

---
 net/ipv4/tcp_bbr.c |    4 ++++
 1 file changed, 4 insertions(+)

@@ -874,6 +874,10 @@ static u32 bbr_sndbuf_expand(struct sock
  */
 static u32 bbr_undo_cwnd(struct sock *sk)
 {
+	struct bbr *bbr = inet_csk_ca(sk);
+
+	bbr->full_bw = 0;   /* spurious slow-down; reset full pipe detection */
+	bbr->full_bw_cnt = 0;
 	return tcp_sk(sk)->snd_cwnd;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/tcp-refresh-tcp_mstamp-from-timers-callbacks.patch queue-4.14/tcp_bbr-reset-full-pipe-detection-on-loss-recovery-undo.patch queue-4.14/tcp_bbr-reset-long-term-bandwidth-sampling-on-loss-recovery-undo.patch queue-4.14/tcp-invalidate-rate-samples-during-sack-reneging.patch queue-4.14/tcp-fix-potential-underestimation-on-rcv_rtt.patch queue-4.14/tcp_bbr-record-full-bw-reached-decision-in-new-full_bw_reached-bit.patch