From eb710b5f62ad3a18742bae70f91e8664ee23cbe3 Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Thu, 7 Dec 2017 12:43:31 -0500 Subject: [PATCH] tcp_bbr: reset full pipe detection on loss recovery undo [ 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. Signed-off-by: Neal Cardwell Reviewed-by: Yuchung Cheng Acked-by: Soheil Hassas Yeganeh Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_bbr.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 3089c956b9f9..ab3ff14ea7f7 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -874,6 +874,10 @@ static u32 bbr_sndbuf_expand(struct sock *sk) */ 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; } -- 2.20.1