pub extern "C" fn recvfrom(
fn_ptr: Option<&extern "C" fn(c_int, *mut c_void, size_t, c_int, *mut sockaddr, *mut socklen_t) -> ssize_t>,
fd: c_int,
buf: *mut c_void,
len: size_t,
flags: c_int,
addr: *mut sockaddr,
addrlen: *mut socklen_t,
) -> ssize_t