Similar to doix said, consider reading the time as IO and then rewrite the code in sans-IO style so you can inject the time.
Then it's a unit test that looks too obvious to exist until you read the ticket mentioned in the comment above it
No need for monkey patching or hooking or preload
But before that you add a couple checkmarks to the manual pre-release test list: "1 hour soak test" and "check network transfer meters before and after, expect under 50 MB used in 1 hour (see bug #6969)"
Then it's a unit test that looks too obvious to exist until you read the ticket mentioned in the comment above it
No need for monkey patching or hooking or preload
But before that you add a couple checkmarks to the manual pre-release test list: "1 hour soak test" and "check network transfer meters before and after, expect under 50 MB used in 1 hour (see bug #6969)"
In Linux they're under /sys/class/net I think