netdev - Re: [PATCH net-next] tcp: fix tcp_probe_timer() for TCP_USER

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Message-ID: <1495389653.6465.53.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Sun, 21 May 2017 11:00:53 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, soheil@...gle.com
Subject: Re: [PATCH net-next] tcp: fix tcp_probe_timer() for TCP_USER_TIMEOUT

On Sun, 2017-05-21 at 13:51 -0400, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Sun, 21 May 2017 10:39:00 -0700
> 
> > From: Eric Dumazet <edumazet@...gle.com>
> > 
> > TCP_USER_TIMEOUT is still converted to jiffies value in
> > icsk_user_timeout
> > 
> > So we need to make a conversion for the cases HZ != 1000 
> > 
> > Fixes: 9a568de4818d ("tcp: switch TCP TS option (RFC 7323) to 1ms clock")
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> 
> Applied, thank Eric.
> 
> I kinda expected a few pieces of fallout from the 1ms changes :)

Absolutely ;)

One last piece is in TCP_SYNCNT support.

I saw that retransmits_timed_out() could have a rounding error :

tcp_time_stamp(tcp_sk(sk)) - start_ts) ends up to 999 ms,
while the timeout is/was 1000 ms (And timer _was_ progammed with 1000
jiffies for HZ=1000 kernel)

So if user setup TCP_SYNCNT = 1 socket option, we sometime sends one
extra SYN packet.

I will send a fix later.