Function massa_bootstrap::listener::drain_accept

fn drain_accept<S>(accept: impl FnMut() -> Result<S>, out: &mut Vec<S>)

Drain all currently-ready connections from accept into out.

The drain ends on the first error, whether it is WouldBlock (no more pending connections) or any other error such as a persistent EMFILE / ENFILE. Ending the drain on a non-WouldBlock error (instead of continue-ing) is what prevents a sticky listener-level failure from spinning poll() forever and starving the STOP_LISTENER token.