From febf081987ec445f071ed10b73e9707a88cc5cc4 Mon Sep 17 00:00:00 2001 From: stephen hemminger Date: Mon, 14 Mar 2011 07:52:12 +0000 Subject: [PATCH] tcp: fix RTT for quick packets in congestion control In the congestion control interface, the callback for each ACK includes an estimated round trip time in microseconds. Some algorithms need high resolution (Vegas style) but most only need jiffie resolution. If RTT is not accurate (like a retransmission) -1 is used as a flag value. When doing coarse resolution if RTT is less than a a jiffie then 0 should be returned rather than no estimate. Otherwise algorithms that expect good ack's to trigger slow start (like CUBIC Hystart) will be confused. Signed-off-by: Stephen Hemminger Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 65f6c0406245..e16b17efcf57 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3350,7 +3350,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, net_invalid_timestamp())) rtt_us = ktime_us_delta(ktime_get_real(), last_ackt); - else if (ca_seq_rtt > 0) + else if (ca_seq_rtt >= 0) rtt_us = jiffies_to_usecs(ca_seq_rtt); } -- GitLab