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Date: Sun, 20 Feb 2005 16:38:16 -0800
From: Julian Elischer <julian@elischer.org>
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Subject: ABI suggestions?
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I'm looking at implementing a kernel module that implelemnts an ABI that allows 
a particular tcp session to be followed.
I'm not terribly intereted in the data sent/received bas in the actual session
behaviour itself..

In other words I want to watch the tcp stack making decisions.
Obviously this would require adding trace points (not normally compiled in)
into the tcp stack. I'd consider that possibly KTR would be good for that except
that I need to do this on 4.x machines so possibly another mechanism will be 
needed (or I back port KTR).

I'm looking to see trace messages such as
"Congestion window changed to %d",
and
"process reads %d bytes, %d bytes now available in receive window"


using tcptrace and other tools okn the data flow across the network "simulates"
or "guesses" about some of these things, but there is no real authoratative
information about how the stack is thinking..

parts of the ABI I'm thinking about include:

how to get the events out (if not KTR) and
how to specifiy a session to trace (assuming you want to watch sessions that
may not exist yet)

if anyone has any ideas on this, let me know :-)

regards julian

p.s. would this be generally useful (assuming it can be achieve without
any overhead when compiled out)?