Micro-optimization and micro-style: use a `for (i = 0; i < interfaces_count; i++)` loop here.

Micro-optimization: CPU prefetchers are good at recognizing memory access patterns in ascending order but generally not when they're in descending order.

Micro-style: Prefer not mutating variables. It's a kind of future-proofing; if someone changes the code later on and assumes interfaces_count is factual, things will go badly wrong.