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tcp: fix RTO calculated from cached RTT 

Commit 1b7fdd2ab5 ("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 <ncardwell@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-By: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Neal Cardwell 2013-09-16 21:44:20 -04:00 committed by David S. Miller
parent 4bdf259763
commit 269aa759b4
1 changed files with 3 additions and 1 deletions
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4
net/ipv4/tcp_metrics.c
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@ -502,7 +502,9 @@ void tcp_init_metrics(struct sock *sk)
* ACKs, wait for troubles. * ACKs, wait for troubles.
*/ */
if (crtt > tp->srtt) { 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) { } else if (tp->srtt == 0) {
/* RFC6298: 5.7 We've failed to get a valid RTT sample from /* RFC6298: 5.7 We've failed to get a valid RTT sample from
* 3WHS. This is most likely due to retransmission, * 3WHS. This is most likely due to retransmission,