Function send_to 

fn send_to(
    socket: &UnixDatagram,
    path: &Path,
    data: &[u8],
    retry_until: Option<Instant>,
) -> Result<()>

Send the data as one datagram, or as a memfd if it does not fit. A signal, like the SIGCHLD of every exited child, interrupts a send which waits, the kernel does not restart one with a timeout, so it gets retried until retry_until, if any.