Simulating time for a different linux process.

From: Bernd M?ller-Zimmermann (Bernd.temporary1_at_gmx.de)
Date: 08/18/04 

Date: 18 Aug 2004 06:21:02 -0700

How can one user process change the perception of system time of
another user process?

I'm writing a test controller TC to test the functionality of a given
executable process 'X'. The functionality of X depends on X's
perception of time.

     TC <------> X

Example: The test controller will send a series of 2 messages to X
using a pipe. X is supposed to behave differently if the time delta
between the messages is 5, 10 or 15 milliseconds of real time.

How can the test controller check the correct behaviour of X? How can
the test controller enforce, that X perceives the second message to
have been received 10 ms after the first?

(The test controller could just send the second message 10 ms after
the first. But this is a simulation on a slow multi-user system. Under
higher system load, it may take some real time until X really receives
the message.)

The executable X shall not be modified.
Any simulation systems with simulated time?
Intercepting the 'gettimeofday()' call of X with some sort of
debugging?

Thanks a lot
Bernd