From 269aa759b474570fa642452742741525cfc226a9 Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Mon, 16 Sep 2013 21:44:20 -0400 Subject: [PATCH] tcp: fix RTO calculated from cached RTT Commit 1b7fdd2ab5852 ("tcp: do not use cached RTT for RTT estimation") did not correctly account for the fact that crtt is the RTT shifted left 3 bits. Fix the calculation to consistently reflect this fact. Signed-off-by: Neal Cardwell Cc: Eric Dumazet Cc: Yuchung Cheng Acked-by: Eric Dumazet Acked-By: Yuchung Cheng Signed-off-by: David S. Miller --- net/ipv4/tcp_metrics.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c index 4a22f3e715df..52f3c6b971d2 100644 --- a/net/ipv4/tcp_metrics.c +++ b/net/ipv4/tcp_metrics.c @@ -502,7 +502,9 @@ reset: * ACKs, wait for troubles. */ if (crtt > tp->srtt) { - inet_csk(sk)->icsk_rto = crtt + max(crtt >> 2, tcp_rto_min(sk)); + /* Set RTO like tcp_rtt_estimator(), but from cached RTT. */ + crtt >>= 3; + inet_csk(sk)->icsk_rto = crtt + max(2 * crtt, tcp_rto_min(sk)); } else if (tp->srtt == 0) { /* RFC6298: 5.7 We've failed to get a valid RTT sample from * 3WHS. This is most likely due to retransmission,