Patch "tcp_bbr: reset long-term bandwidth sampling on loss recovery undo" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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

    tcp_bbr: reset long-term bandwidth sampling on loss recovery undo

to the 4.9-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-long-term-bandwidth-sampling-on-loss-recovery-undo.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 600647d467c6d04b3954b41a6ee1795b5ae00550 Mon Sep 17 00:00:00 2001
From: Neal Cardwell <ncardwell@google.com>
Date: Thu, 7 Dec 2017 12:43:32 -0500
Subject: tcp_bbr: reset long-term bandwidth sampling on loss recovery undo

From: Neal Cardwell <ncardwell@google.com>

commit 600647d467c6d04b3954b41a6ee1795b5ae00550 upstream.

Fix BBR so that upon notification of a loss recovery undo BBR resets
long-term bandwidth sampling.

Under high reordering, reordering events can be interpreted as loss.
If the reordering and spurious loss estimates are high enough, this
can cause BBR to spuriously estimate that we are seeing loss rates
high enough to trigger long-term bandwidth estimation. To avoid that
problem, this commit resets long-term bandwidth sampling on loss
recovery undo events.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -847,6 +847,7 @@ static u32 bbr_undo_cwnd(struct sock *sk
 
 	bbr->full_bw = 0;   /* spurious slow-down; reset full pipe detection */
 	bbr->full_bw_cnt = 0;
+	bbr_reset_lt_bw_sampling(sk);
 	return tcp_sk(sk)->snd_cwnd;
 }
 


Patches currently in stable-queue which might be from ncardwell@google.com are

queue-4.9/tcp_bbr-reset-full-pipe-detection-on-loss-recovery-undo.patch
queue-4.9/tcp_bbr-reset-long-term-bandwidth-sampling-on-loss-recovery-undo.patch