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Date: Sun, 27 Nov 2005 21:10:14 +0000
From: Brian Candler <B.Candler@pobox.com>
To: Julian Elischer <julian@elischer.org>
Message-ID: <20051127211014.GA31851@uk.tiscali.com>
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Cc: net@freebsd.org
Subject: Re: proposal:  TCP rendevous
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On Sat, Nov 26, 2005 at 10:18:49PM -0800, Julian Elischer wrote:
> In this world of P2P apps it would be neat to have a way that two P2P apps
> could attach to each other even though each is through a firewall. Most 
> firewalls only allow
> "outgoing" connections.
> 
> It would of course be possible via a 3rd party relaying but that is 
> inneffieient and the throughput
> would be limited by throughput limits on the 3rd party link.
> 
> It must be possible, with the connivance of a 3rd party both parties 
> could be able
> to make suitable 'OUTGOING' connections.
> The 3rd party would spoof needed packets using information supplied
> by the two parties.

See this: http://samy.pl/chownat/

(Haven't tried it myself, but came across it on Freshmeat a while ago. I
imagine it must rely on the NAT firewalls not changing the source UDP port
unless they have to)