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

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Message-ID: <CADVnQy=iurcb+Ce3MKaB_szq-JOPerrPFvTxdy556O90qg1gWg@mail.gmail.com>
Date:   Mon, 1 May 2017 20:31:35 -0400
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] tcp: fix wraparound issue in tcp_lp

On Mon, May 1, 2017 at 7:56 PM, Stephen Hemminger
<stephen@...workplumber.org> wrote:
> On Mon, 01 May 2017 15:29:48 -0700
> Agreed time wraparound would cause problems.
> But why not use existing time_after() macro here?
>

I suspect this is because time_after() asserts that it is being used
on unsigned long (64 bits), and tcp_time_stamp is 32 bits.

I suppose for tcp_time_stamp comparisons we could re-use the u32 TCP
sequence macros for before() and after()? Even the comment for
before()/after() is already generic enough to apply to tcp_time_stamp:
"The next routines deal with comparing 32 bit unsigned ints and worry
about wraparound (automatic with unsigned arithmetic)." That might be
nice.

neal