From owner-freebsd-ipfw@FreeBSD.ORG  Wed Mar  7 22:04:41 2007
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From: Chuck Swiger <cswiger@mac.com>
Date: Wed, 7 Mar 2007 13:27:19 -0800
To: Justin Robertson <justin@sk1llz.net>
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Cc: freebsd-ipfw@freebsd.org
Subject: Re: IPFW SACK options
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On Mar 7, 2007, at 12:54 PM, Justin Robertson wrote:
[ ... ]
>   Due to the nature of the current performance disparity between  
> 6.x (I
> assume this is due to the work on making processes thread  
> friendly?) and
> 4.11 (still kicking arse) I'm sticking with the 4.11 branch - and  
> here comes
> my question. If someone is interested, could you work up an option  
> to allow
> removal of the sackOK (sack permitted negotiation) on SYN packets,  
> and then
> pass the SYN packet on with the tcpoption for sack stripped?

Perhaps trying:

   sysctl net.inet.tcp.sack.enable=0

...will do what you are looking for?

-- 
-Chuck