ceiling fixture wires
Looks like a typical switch loop, where you have a power cable coming into the box, and another cable acts as an out and back in, though the switch, for the hot leg. 



Connect the black and white of your fixture to the two whites in either configuration. (Technically, the white coming back from the switch is your "hot", so connect that to black if you know which is which. It should've been labelled by the installer.)