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%3Ba=su...

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