From 61c51da2b4bd8abb2920f4dec0861a6fe5b8b486 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 commit 2f6c498e4f15d27852c04ed46d804a39137ba364 upstream. 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 97f9cac98348..64ff4966aad6 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -843,6 +843,10 @@ 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; }