linux-kernel - [PATCH 4.18 191/228] tcp_bbr: in restart from idle, see if we should exit PROBE

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Message-Id: <20181002132511.040897325@linuxfoundation.org>
Date:   Tue,  2 Oct 2018 06:24:48 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kevin Yang <yyd@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.18 191/228] tcp_bbr: in restart from idle, see if we should exit PROBE_RTT

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kevin Yang <yyd@...gle.com>

[ Upstream commit 5490b32dce6932ea7ee8e3b2f76db2957c92af6e ]

This patch fix the case where BBR does not exit PROBE_RTT mode when
it restarts from idle. When BBR restarts from idle and if BBR is in
PROBE_RTT mode, BBR should check if it's time to exit PROBE_RTT. If
yes, then BBR should exit PROBE_RTT mode and restore the cwnd to its
full value.

Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control")
Signed-off-by: Kevin Yang <yyd@...gle.com>
Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
Reviewed-by: Yuchung Cheng <ycheng@...gle.com>
Reviewed-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/tcp_bbr.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -174,6 +174,8 @@ static const u32 bbr_lt_bw_diff = 4000 /
 /* If we estimate we're policed, use lt_bw for this many round trips: */
 static const u32 bbr_lt_bw_max_rtts = 48;
 
+static void bbr_check_probe_rtt_done(struct sock *sk);
+
 /* Do we estimate that STARTUP filled the pipe? */
 static bool bbr_full_bw_reached(const struct sock *sk)
 {
@@ -304,6 +306,8 @@ static void bbr_cwnd_event(struct sock *
 		 */
 		if (bbr->mode == BBR_PROBE_BW)
 			bbr_set_pacing_rate(sk, bbr_bw(sk), BBR_UNIT);
+		else if (bbr->mode == BBR_PROBE_RTT)
+			bbr_check_probe_rtt_done(sk);
 	}
 }