It uses a hardware clock, one that pauses during sleep. There is no tick.
If you wanted to see how time impacts the program, you'd prob change fns like calculate_tcp_clock to take uptime as an argument so that you could sanity check it.
If you wanted to see how time impacts the program, you'd prob change fns like calculate_tcp_clock to take uptime as an argument so that you could sanity check it.
The code that uses that value can be run in an environment where that value can be controlled.
I have written code that does this same thing and built a test harness for it.