Message-ID: <44DDD83E.9010307@comcast.net>
Date: Sat, 12 Aug 2006 09:31:42 -0400
From: John Richard Moser <nigelenki@comcast.net>
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To: David Miller <davem@davemloft.net>
CC: linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: How does Linux do RTTM?
References: <44DACA22.6090701@comcast.net>	<20060809.231244.35509467.davem@davemloft.net>	<44DAF559.8010705@comcast.net> <20060810.020205.10245646.davem@davemloft.net>
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David Miller wrote:
> Please use netdev@vger.kernel.org for discussions about the linux
> networking implementation, not linux-kernel@vger.kernle.org
> 

Kay.

I'm told now that it uses Jiffies for TCP timestamps.  I've had thoughts
on this:

 - I figured a random timestamp with random microsecond skew would be
nice but this might expose internals of the RNG; amusingly I'm trying
not to expose internals of the RNG by exposing system time.

 - Someone recommended starting at zero.  This would work, really,
there's no attacks based on guessing the TCP timestamp value.  This is
nice since if I want to hax0rz then I might make a connection and see
how many jiffies there are to get a feel for the system's uptime; this
tells me how long since you upgraded your kernel, so I have an arsenal
of vulns I KNOW you haven't fixed ready ;)  Starting at 0 doesn't give
that information.

Comments?

> Thanks a lot.
> 

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