firmware

I hope that most of you have already seen the upside-downternet. This hack has been around for a while, but that doesn't make it any less brilliant: thanks to some Linux trickery, every user connected to your network gets served their images upside down. It's pretty clever.

It's also similar to a related but not-quite-identical application I've had in mind. So how does it work? The magic arrives in the form of transparent proxying, a technique whereby a router sends its traffic through a proxy server without the user responsible for that traffic noticing anything (or having to change their configuration). This is called "transparent proxying". In the case of the upside-downternet the Proxy server was Squid, an awesomely powerful, sprawling application. In this case Squid runs on its own machine; the router is configured to reroute its traffic through the Squid server before letting it out onto the net. The Squid server keeps an eye on the URLs being requested and uses a custom script to rewrite any that look like images. The replacement URLs point at a web-accessible script on the Squid server that knows to fetch the original image, flip it upside down, then serve it back.

As I said, I wanted to do approximately the same thing. But I wanted to do it all on the router. And I don't mean router in the systems engineer sense of "router". I don't mean a box sitting in a datacenter with fiber channel running into the back. I mean a box sitting on a shelf in Best Buy with a peel-off coupon on the front.

All of us at EchoDitto are big fans of the FON project — we run a FON access point here at the office, and I run one at home even though my primary router is a much-more-capable WRT54G running an old version of the Sveasoft Linux firmware. I got my Fonera router from Phil, so I assume he's running a FON AP, too. We're trying to support the project — honest!

I say all this out of guilt. Last night I hacked a Fonera. I know, I know — they sell these things for next to nothing only so that they'll get distributed and the project will grow. But I don't have any more WAN pipes available to share! So I hope the project's sponsors will forgive me for succumbing to the siren song of $10 Fonera routers on eBay. I couldn't help myself from checking out what a spare unit can do.

"Kind of a lot" turns out to be the answer. The La Fonera is based on the Atheros chipset, which is found in a number of other commercial routers and supported by both the DD-WRT and OpenWRT firmware projects.

Sveasoft kicked off the custom router firmware scene, but the author's controversial attitude toward the GPL made them fall out of favor rather quickly. Besides, truly open efforts quickly outpaced the project. OpenWRT is the king of functionality, but also the most intimidating — they seem to have a general "GUIs are for chumps" sort of attitude. While I aspire to similar levels of snobbery, I'm more comfortable sticking with projects that have support forums filled with posts that are comprehensible to someone just getting started with the project.

Besides, I've had great luck with DD-WRT in the past, using it to successfully repeat a neighbor's faint wifi signal through my girlfriend's apartment (with permission, of course — but without having to do anything to his router, i.e. no WDS).