Raspberry Pi Weekend project

So finally took the time to try out a Raspberry Pi. For this weekend project wanted to do something relatively simple. Essentially, I wanted to recreate/enhance the functionality of a TL-WR702N.

The TL-WR702N Nano Router is a neat device but being closed, can not be customized to what I wanted. It can be used in the following modes:

• AP
• Client
• Repeater
• Router
• Bridge

Specifically I was interested in the bridge mode. However, rather than bridging from one SSID to another SSID, I wanted to route/nat between the two. So in theory, should be simple to implement (as the hardware should have all the necessary components) but not allowed by the software.

Enter the Raspberry Pi.

So the Pi, is a mini computer that can be loaded with any software you want. The B-model, has a built-in Ethernet and USB ports to plug-in two WIFI adaptors. For this functionality I am using the following:

• Raspberry-Pi Model-B
• WIFI stick (2 units)

For the software I am using:

• Raspberry Pi buildroot
• hostapd-rtl8192cu from Realtek You need to get the RTL8188CUS package for Linux.

So you need two WIFI adaptors, as one will not work as master and slave at the same time. Essentially, one WIFI interface will act as the client WIFI station. The other WIFI interface acts as a WIFI hotspot. I chose to use buildroot instead of a normal Linux distro like Raspbian or Arch Linux Arm because I wanted to run it as an embedded system. Normal Linux distro's are supposed to be properly shutdown and would complain when you simply yank the power cord. The buildroot image I have is customized so that the file system is always mounted read-only. It will switch to read-write only to write persistent data and then switch back to read-only. The normal hostapd that comes with buildroot is the normal open source project and does not come with the rtl8192cu driver. You need to download and build the Realtek version. For this to work, I did the following:

1. Create a start-up scripts that set the whole thing up.

   • sets-up the filesystem
   • starts syslog, sshd, rngd
   • sets-up eth0 and wlan0 to be configured by ifplugd
   • starts wpa_supplicant on wlan0
   • starts httpd
   • start and configure wlan1 as an Access Point.
   • start and configure dnsmasq for DNS and DHCP.
2. Wrote a small web UI to configure the WIFI client.

All this stuff can be found in github.