802.11 Wireless Networks: The Definitive Guide, 2nd Edition

Chapter 19. Using 802.11 on Linux

When the first edition of this book was written, 802.11 was only just coming to Linux. Cards had to be selected carefully because very few cards were supported with full open source drivers that evolved at the same pace as the Linux kernel. Linux support has now moved into the mainstream, with many vendors actively sponsoring driver development projects, or at the very least supporting efforts to target their hardware. Broadcom is a notable exception.

Most 802.11 devices are supported by the PCMCIA system. As with Windows drivers, installing wireless cards on Linux creates Ethernet interfaces. Many Linux drivers expose an Ethernet interface through the kernel, and most drivers even name the resulting interfaces with the eth prefix. Programs can use the Ethernet interface to send and receive data at the link layer, and the driver handles Ethernet-to-802.11 conversions.^[77] Many of the things you would expect to see with an Ethernet interface remain the same. ARP works identically, and the IP configuration is done with the same utilities provided by the operating-system distribution. ifconfig can even be used to monitor the interface status and see the data sent and received.

PCMCIA Support on Linux

Initially, most wireless networking adapters were add-on cards that were based on the PC Card specification.^[78] PC Cards attach to the system bus through a 16-bit controller interface that operates at 8 MHz. Even though performance was limited by the bus ...