netdev - Re: [PATCH net] tcp: use signed arithmetic in tcp_rtx_probe0_timed

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Date: Sat, 8 Jun 2024 09:19:45 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	Neal Cardwell <ncardwell@...gle.com>, eric.dumazet@...il.com, 
	Menglong Dong <imagedong@...cent.com>
Subject: Re: [PATCH net] tcp: use signed arithmetic in tcp_rtx_probe0_timed_out()

On Fri, Jun 7, 2024 at 8:58 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> Due to timer wheel implementation, a timer will usually fire
> after its schedule.
>
> For instance, for HZ=1000, a timeout between 512ms and 4s
> has a granularity of 64ms.
> For this range of values, the extra delay could be up to 63ms.
>
> For TCP, this means that tp->rcv_tstamp may be after
> inet_csk(sk)->icsk_timeout whenever the timer interrupt
> finally triggers, if one packet came during the extra delay.
>
> We need to make sure tcp_rtx_probe0_timed_out() handles this case.
>
> Fixes: e89688e3e978 ("net: tcp: fix unexcepted socket die when snd_wnd is 0")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Menglong Dong <imagedong@...cent.com>

Reviewed-by: Jason Xing <kerneljasonxing@...il.com>

Thanks!