Unfortunately, we are not the developers of the dd-wrt firmware and we don’t know how the firewall rules were programmed on that firmware. In order to get support for the firmware we advise you to post a question on the forum of the dd-wrt site (http://www.dd-wrt.com/site/community). A developer of this firmware may give you the necessary explanations you require. Another solution would be to connect your hotspot router to another router and set the firewall rules on the secondary router, this is just an advise though.