Just to provide a heads up to others thinking of using the rpi model B as an access point gateway: DON'T
The bottom line is that the built-in ethernet usmsc(4) on this board does not seem to support bridging - I find this utterly mindboggling so I think it's worth outlining what I did to come to this conclusion. I tried the original set up but used a Dlink DWL-6122 supported by the rum(4) driver which does hostap. I still couldn't get the bridge to pass packets and so I added a usb-ethernet adaptor cdce(4) to the bridge and hooked a laptop to it. No packets were seen to pass. To check that it wasn't duff I put the above adaptor in my amd64 desktop system, configured a bridge and added it and the re(4) interface (which connects to the router). Everything just worked as expected... I then tested the Dlink usb-wifi dongle in the desktop, adding that to the bridge rather than to ethernet dongle and configured hostapd. It worked OK and I could connect over wireless to the 'new' access point with a mobile phone. Subsequent attempts using the Dlink wifi dongle with the rpi B produced a load of error messages so I wonder if the usb hardware is flaky. If I get a chance next month I will try with another rpi model B to decide one way or the other, but for now would not recommend them... Dave