netdev - [PATH net 2/4] tcp: always evaluate losses in RACK upon undo

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Message-Id: <20171207193333.59039-3-ycheng@google.com>
Date:   Thu,  7 Dec 2017 11:33:31 -0800
From:   Yuchung Cheng <ycheng@...gle.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, ncardwell@...gle.com,
        priyarjha@...gle.com, Yuchung Cheng <ycheng@...gle.com>
Subject: [PATH net 2/4] tcp: always evaluate losses in RACK upon undo

When sender detects spurious retransmission, all packets
marked lost are remarked to be in-flight. However some may
be considered lost based on its timestamps in RACK. This patch
forces RACK to re-evaluate, which may be skipped previously if
the ACK does not advance RACK timestamp.

Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
Reviewed-by: Neal Cardwell <ncardwell@...gle.com>
Reviewed-by: Priyaranjan Jha <priyarjha@...gle.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp_input.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 734cfc8ff76e..5a240f9d208b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2326,6 +2326,7 @@ static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss)
 	}
 	tp->snd_cwnd_stamp = tcp_jiffies32;
 	tp->undo_marker = 0;
+	tp->rack.advanced = 1; /* Force RACK to re-exam losses */
 }
 
 static inline bool tcp_may_undo(const struct tcp_sock *tp)
-- 
2.15.1.424.g9478a66081-goog