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Date:	Mon, 2 Jun 2008 09:40:15 +1000 (EST)
From:	James Morris <>
To:	Adam Langley <>
Subject: Re: [PATCH] Fix corrupt TCP packets when options space overflows
 with MD5SIG enabled

On Sat, 31 May 2008, Adam Langley wrote:

> When MD5 signatures are turned on we can end up with syntactically invalid
> packets with a header length < 20 bytes. This is because tcp_header_size
> overflows with 12 bytes of timestamp, 20 bytes of signature and > 8 bytes of
> SACK option.
> Since we can't fit any SACK blocks in the final 8 bytes of options space, and
> the MD5 signature is more important, we disable including SACK, or even
> advertising it, when MD5 is enabled.
> Signed-off-by: Adam Langley <>

Reviewed-by: James Morris <>

(FYI, the upcoming replacement for this, TCP-AO, is designed to be SACK 

James Morris
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