netdev - Re: [RFC] tcp: allow timestamps even if SYN packet has tsval=0

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Message-Id: <20090311.064710.255854254.davem@davemloft.net>
Date:	Wed, 11 Mar 2009 06:47:10 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	dada1@...mosbay.com
Cc:	netdev@...r.kernel.org, ilpo.jarvinen@...sinki.fi
Subject: Re: [RFC] tcp: allow timestamps even if SYN packet has tsval=0

From: Eric Dumazet <dada1@...mosbay.com>
Date: Wed, 11 Mar 2009 13:17:54 +0100

> So apparently WindowsXP sends a NULL tsval in SYN packet, then
> subsequent packets get a real value (60498) in this case.
> 
> This seems to work on other OS as well, so is the following patch
> considered evil ?  Do we have security concerns or only risking
> windows client to have slightly wrong rtt estimation at the begining
> of the tcp session ?

I think we'll have to accept this.

I don't see other systems blocking initial ts_ecn values of
zero like we do.
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