Function splice_loop 

pub fn splice_loop(
    do_flush: Arc<AtomicBool>,
    flush_event: Option<Sender<()>>,
    fd_in: RawFd,
    fd_out: RawFd,
)

Loop while reading and writing from one file descriptor to another using splice(2). The loop stop when do_flush is set to true. At the end, a flush event is send to flush_event if any.

This function should be used in a dedicated thread, e.g. thread::spawn(move || splice_loop(do_flush, None, rx.as_raw_fd(), tx.as_raw_fd())).

You should ensure that there is no append flag to the fd_out file descriptor. You can use unset_append_flag() if needed and set_flags() to restore to the initial state.