Building Wireless Community Networks, Second Edition

NoCatAuth Captive Portal

While some node owners are perfectly happy opening their networks to whomever happens to be in range, most of us hesitate at the thought of paying for our neighbors to use our bandwidth. After all, apart from using up resources that we’re paying for, anonymous users could potentially abuse other networks and have their shenanigans traced back to our network! If we want to provide responsible wireless access, we need a way to securely identify users when they connect and then allocate only the resources that the node owner is willing to contribute. After the Portland Summit, it was obvious that one key component was missing from the community network idea: a freely available captive portal implementation.

The idea behind a captive portal is fairly straightforward. Rather than relying on the built-in security features of 802.11b to control who can associate with an AP, we configure the access point with no WEP and as an open network. The AP is also in bridged mode and connected via a crossover cable to an Ethernet card on a Linux router. It is then up to the router to issue DHCP leases, throttle bandwidth, and permit access to other networks. When a user attempts to browse any web page, they are redirected to a page that presents the user with a login prompt and information about the node they are connected to. If the wireless gateway has a method of contacting a central authority to determine the identity of the connected wireless user, then it can relax ...