When he is coming in toward you, take your coiled rope, and fling it in the direction of his neck; that will stop his advance and get him to go back out on to the circle. Control the front end in this instance, and the attack stops. When he gets back out on the circle I would then stop him, and do some exercises that will remind him that 'you control his feet'; disengage his hindend, and front end. Back him up, and then ask for a few more circles, and make sure you change directions often, so he doesn't get 'bored'. If he's bored on the line, you may just be doing too much on each side; I will generally do alot of stopping, and direction changes, and with the Appy I recently sold, this helped him realize he wasn't in charge, I was. If you have too, shorten your line for a bit, as that will give you better control of his motion.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."