pub type buffer_tx_error_fn = Option<unsafe extern "C" fn(unsent: *mut *mut rte_mbuf, count: u16, userdata: *mut c_void)>;
pub enum buffer_tx_error_fn { None, Some(unsafe extern "C" fn(*mut *mut rte_mbuf, u16, *mut c_void)), }
No value.
Some value of type T.
T