So the bounds check is:

    queue.bufs_in_use[rx_index]

If so the bounds check could possibly be safely eliminated by the programmer because I think `wrap_ring` ensures that rx_index will always be in bounds?

Yes. It wouldn't be too unidiomatic to use get_unchecked in those two places, perhaps with a debug_assert! in place.

It would be really nice if this wasn't needed, but it's a valid use of unsafe code.