Functions to calculate distance between two locations, based on GeoIP data.
Returns the distance between two IP addresses using the haversine formula, based on GeoIP database locations. Requires Bro to be built with GeoIP.
A1: First IP address. A2: Second IP address. Returns: The distance between a1 and a2 in miles, or -1.0 if GeoIP data is not available for either of the IP addresses.