netdev - Re: [PATCH] Fix corrupt TCP packets when options space overflows with MD5SIG enabled (v2)

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Message-Id: <20080618.015206.22767411.davem@davemloft.net>
Date:	Wed, 18 Jun 2008 01:52:06 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	billfink@...dspring.com
Cc:	agl@...erialviolet.org, netdev@...r.kernel.org
Subject: Re: [PATCH] Fix corrupt TCP packets when options space overflows
 with MD5SIG enabled (v2)

From: Bill Fink <billfink@...dspring.com>
Date: Wed, 18 Jun 2008 02:34:46 -0400

> I am not particularly familiar with the TCP MD5 option, but in googling
> around I found the following at the end of Section 2.2 Transmission,
> of RFC 4808, "TCP-MD5 Key Change", dated March 2007:
> 
>     "Note that there is an ambiguity when an acknowledgment is received
>     for a segment transmitted with two different keys.  The TCP Timestamp
>     option [RFC1323] can be used for disambiguation."
> 
> This would seem to imply, that at least in some scenarios, it would be
> advisable to have TS enabled in conjunction with MD5.

That does change the situation a bit, yes.

It's pretty easy, depending upon the timestamp resolution, to
end up with the original transmit and the retransmit having
the same timetsamp value.  So this suggestion in the RFC is
I think not a complete solution.
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