Hello, I doubt that this is original. Several reasons for that. First, the mark is Daoguang, two reigns after Qianlong, so it cannot be Qianlong. The crackling looks too regular, as if it were artificially made. I cannot see on these images whether the top side is also crackled, though. The foot rim also doesn't look quite right for the period, in my view. With monochrome items it is sometimes difficult to tell. If possible, I would recommend that you have someone do a hands on inspection. But my own view is that it is not original.