Function nginx::BIO_callback_ctrl

pub unsafe extern "C" fn BIO_callback_ctrl(
    b: *mut BIO, 
    cmd: c_int, 
    fp: Option<unsafe extern "C" fn(arg1: *mut BIO, arg2: c_int, arg3: *const c_char, arg4: c_int, arg5: c_long, arg6: c_long)>
) -> c_long