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Chapter 4 -

Software Systems

This chapter discusses software design decisions in terms of the Gentoo Linux operating system,

the Madwifi Driver for Atheros based devices, Orinoco Driver used for the wireless client

interface, and the system automation scripts.

4.1

Gentoo Linux

The operating system was required to support the Click Modular Router and allow our chosen

wireless cards to work. Since the Click Modular Router only runs on Linux and BSD variants,

we were limited to these operating systems. There also needed to be support in the form of a

driver to allow the D-Link DWL-AG530 wireless cards to function.

There are a number of different Linux distributions available. A distribution that was not overly

specialized was required. However, the distribution could not be too complex, as it would

overwhelm the systems being used. Distributions specific to routing applications, such as Clark

Connect and the Linux Router Project were researched. It was found that most of these

distributions were meant to be installed and configured based on the distributions specifications.

This would have limited the ability to use other software, and configure these distributions to

meet the projects specifications. Other distributions, such as Fedora and OpenSuse were also

considered. These are very popular and flexible distributions; however they are generally used on

systems ranging from modern desktops to servers, and require more computing power than the

machines for this project had.

Once the Gentoo operating system was installed, only the software needed to boot the machine

and some basic utilities were available. When any other software was needed, it was downloaded

as source code and compiled on the system itself using the Portage system. This allowed only the

software that was needed for this project to be installed, including support utilities for the router

software and diagnostic software to monitor and debug the system. The systems were therefore

configured with a minimum installation, while still remaining very flexible.

4.2

Madwifi Driver

As mentioned in Chapter 3, the wireless cards that were used were the D-Link DWL-AG530's

based on the Atheros chipset. Under Linux these devices are supported with a Kernel Driver

from the Madwifi project. There are two parts of this driver, the ath_pci and the ath_hal kernel

modules. Atheros devices are able to change their channels to ones not defined for the 802.11

protocols. To limit a user to the 802.11 standard channels, Atheros provides a hardware

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