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Date: Mon, 3 Jan 2005 23:02:48 -0600 (CST)
From: Mike Silbersack <silby@silby.com>
To: Charles Swiger <cswiger@mac.com>
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cc: net@freebsd.org
Subject: Re: Fixing "Slipping in the window" before 4.11-release
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On Mon, 3 Jan 2005, Charles Swiger wrote:

> Are you relying on the IPID or the connection tuple of 
> srcIP+srcPort+destIP+destPort to identify the SYN packet as being associated 
> with an already established connection?

Connection tuple.

>> This means that SYN packets left of the window will no longer receive an 
>> ACK, and SYN packets in the window will no longer reset the connection.  In 
>> all states other than ESTABLISHED, SYN packets are handled as they were 
>> before, in case there's some edge case where that could happen.
>
> This seems to be a reasonable improvement: the stack shouldn't be ACK'ing 
> data outside of a valid connection window to begin with.

I spoke inaccurately above.  We trim the ACK to the left edge of our 
window, then ACK that value.  So, it *shouldn't* affect the state of the 
connection, but it will cause us to flood ACKs.

More comments coming, see upcoming reply to Don...

Mike "Silby" Silbersack