netdev - Re: [PATCH net] tcp: fix wraparound issue in tcp

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Message-ID: <1493690312.31837.35.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 01 May 2017 18:58:32 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] tcp: fix wraparound issue in tcp_lp

On Mon, 2017-05-01 at 18:04 -0700, Eric Dumazet wrote:

> 
> Simply to not perform (tcp_time_stamp - tp->rx_opt.rcv_tsecr) twice.
> 
> jiffies being volatile, this can not be optimized by the compiler.
> 
> I have a patch series (for linux-4.13) that will switch TCP stack to 1ms
> TS options, regardless of CONFIG_HZ value, and when cooking it I found
> this bug.

I forgot to say that after this upcoming patch series, tcp_time_stamp
will become a more expensive function, no longer a plain (u32)jiffies.