From owner-freebsd-transport@freebsd.org  Wed Oct 31 14:12:03 2018
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From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>
To: freebsd-transport@freebsd.org
Cc: "Hackers freeBSD" <freebsd-hackers@freebsd.org>
Subject: Re: TCP RTT estimate for connections not using timestamps
Date: Wed, 31 Oct 2018 14:11:58 +0000
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On 31 Oct 2018, at 14:04, Jacques Fourie wrote:

Copying to transport@  please respect Reply-To to there.


> Hi,
>
>
> While testing with traffic generators that don’t enable the TCP timestamp
> option I noticed a couple of cases where tcp_xmit_timer() was called with a
> 0 value for rtt with the current smoothed rtt (t_srtt) non zero. This leads
> to a left shift of -1 which is undefined. Looking at the code for the case
> where timestamps are enabled I see that tcp_xmit_timer() is always called
> with TCP_TS_TO_TICKS(t) + 1 for the rtt. Do we need a +1 in the non
> timestamp case as well?
>
>
> Thanks,
>
> Jacques
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