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Date:      Fri, 31 Jan 1997 08:55:35 +1100 (EST)
From:      "Daniel O'Callaghan" <danny@panda.hilink.com.au>
To:        Eivind Eklund <eivind@dimaga.com>
Cc:        Warner Losh <imp@village.org>, hackers@FreeBSD.ORG
Subject:   Transparent proxies (was Re: ipdivert & masqd) 
Message-ID:  <Pine.BSF.3.91.970131084015.263G-100000@panda.hilink.com.au>
In-Reply-To: <3.0.32.19970130190212.00b22780@dimaga.com>

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On Thu, 30 Jan 1997, Eivind Eklund wrote:

> At 08:04 AM 1/30/97 -0700, you wrote:

> I'm thinking about doing transparent proxying for the protocols, but I want
> to see how well the packet-patching version run first.  As it is, it is
> (hopefully) right in 99% of the cases, and it scales well.  If I get
> reports of real-life problems I'll make it a priority to make proxies, but
> not before.

Here's a problem which requires transparent proxies for a data stream, 
not packet-patching: Transparent capture of all HTTP requests on port 80 
and diversion to a www-proxy server.

e.g.

Client Sends                "NAT"        WWW-Proxy receives
10.2.3.4                   10.2.3.1        10.2.3.55

10.2.3.4-> 5.6.7.8:80  ================>   10.2.3.1->10.2.3.55  
GET / HTTP/1.0                             GET http://5.6.7.8:80/ HTTP/1.0

Darren Reed's ipfilter does this with the 'redirect' keyword and some 
trickery in the receiving process.  The example given is for the ftwk's 
ftp-gw program (from ftp.tis.com).  The userland process finds its true 
destination by calling an IOCTL for the kernel NAT code.

regards,

Danny



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