From owner-freebsd-multimedia  Sat Sep  6 01:15:09 1997
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From: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
Message-Id: <199709060702.JAA13303@labinfo.iet.unipi.it>
Subject: intercepting vat (or other rtp) traffic
To: multimedia@freebsd.org
Date: Sat, 6 Sep 1997 09:02:31 +0200 (MET DST)
Cc: luigi@labinfo.iet.unipi.it (Luigi Rizzo)
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Hi,

I would like to write a program which sits underneath vat and other
conferencing apps (such as vic, rat,  etc.), intercepts both outgoing
and incoming traffic, and plays some tricks with it (tricks include
compressing packets, adding redundancy or retransmissions, forwarding
through a tunnel, etc.)

Basically I can think of two ways of achieving the result:

1) patch the network module of vat and intercept traffic there;
2) program vat to use 127.0.0.1 and let my program talk to vat
   using the same address. My program would basically do address
   translation in both directions.

I like better #2, except that I am not sure of how much of the IP
header is used by these apps. Also #1 is not an option when you do not
have sources available :)

Any suggestion on how to operate or pointers to documentation ?

	Thanks
	Luigi