Lack of randomness in rand()

rand() has a dozen issues even when you seed it with a RNG, most of which are not relevant here, but there's still at least one issue with it that is still relevant to proxychains.

If different instances of proxychains get the same result from time() or clock_gettime() and call srand(current_time) at the same time, then as long as their rand()s use the same algorithm, they will get the same result. This could be on the same machine or across different machines.

The easiest solution is to use a proper RNG.
arc4random_uniform() is present on all the BSDs, macOS, Illumos, musl, dietlibc, recent glibc, Android, recent Haiku, but not Windows. On Windows, there's the equivalent BCryptGenRandom(). On Haiku, it's tucked inside a BSD compat library that is part of the system (you still have to link to it manually because it's not libc): https://review.haiku-os.org/c/haiku/+/32/3

Start by locating the rand() and srand(current_time) call sites and reviewing how proxychains handles platform-specific builds. Check the available RNG APIs and linking requirements for each supported platform, then verify that simultaneous instances no longer produce identical results.