I use Canvas to administer "attendance quizzes" in my classroom. The current IP filter can prevent students from taking the attendance quiz from off-campus, but does not prevent students from being counted as present when they are actually in the Library instead of class.
I propose a new type of IP Filter: after a quiz has been submitted the IP address of each submission is checked against the most common IP address of all submissions for that particular assignment (which can be assumed to be the IP address of the classroom). A notification appears in the grade book next to any submission that was made from a different IP address than the most common (classroom) IP address.
In this way it won't prevent any submissions, but will make note of any submissions that were likely not made from the classroom. ....Or, it could go ahead and block submissions from being made if they are well outside of the established "classroom" IP address.