Function accept_error_is_transient 

pub fn accept_error_is_transient(err: &Error) -> bool

Is this accept failure the kind the loop must outlive?

The resource ones — no descriptor left in the process (EMFILE) or in the system (ENFILE), no buffer or memory for the socket — and the one the client causes, ECONNABORTED (it hung up between SYN and accept). Everything else (EBADF, EINVAL, a closed listener) is the listener itself being gone, and the loop must return that.