mac80211 is the Linux API used to write SoftMAC wireless drivers. Right now the MLME is done in the kernel for station mode (STA) and userspace for AP mode (hostapd) but our goal is to eventually move it to userspace completely.
Here is a quick review of the features supported in mac80211.
- IEEE 802.11abgn
- IEEE 802.11d
- Integration of work for the emerging 802.11s standard
Roaming using wpa_supplicant (802.11r as well). See Roaming TODO section for more details
Different types of interfaces, see supported wireless modes for details.
- Vendor specific rate support
The mac80211 book
We are working on a mac80211 book which is generated from comments in the various mac80211 source files. You will find a more thorough review of mac80211 in it; the wiki pages can be used as a quick reference for mac80211 development. The book incorporates the kernel-doc docs below.
mac80211 driver API
The new mac80211 driver interface semantics gives an overview of the expected and suggested driver behavior.
The API page lists notes about using the driver API.
mac80211 drivers are listed on the drivers table
mac80211 802.11d support
mac80211 supports 802.11d by processing country information element on beacons after association with an AP. You should still be able to associate to the AP in your region as cfg80211 allows users to set the regulatory domain from userspace before country information elements are parsed, this is expected to be set via wpa_supplicant upon initialization. We let cfg80211 parse the country information element for us and deal with reviewing regulatory enforcement for us. To review that please see cfg80211's regulatory support.
mac80211 rate control algorithms
Here is a list of current mac80211 rate control algorithms:
PID - PID (proportional-integral-derivative) rate control algorithm
minstrel - a rate control algorithm making use of multi-rate retries
The master device wmaster0
mac80211 creates creates one master device and as many other secondary devices as requested to represent interfaces for the wireless card you have. mac80211 asks for the master device to appear as named as wmaster%d, and wlan%0 for the interfaces. udev may override the naming convention used though. wmaster%d is an internal master device used only by mac80211. It is currently visible only because it uses netdevice structure which we must allocate and use for for QoS. It also serves as a holder for all interfaces we have, and represent the underlying hardware. For example, when TXing your wlan0 STA interface will actually add IEEE-802.11 header data to a frame with just Ethernet headers, and then pass it down to the master device for actual transmission using the low level drivers.
The wlan%d devices (interfaces) are the devices you would use to configure your wireless settings.
mac80211 files and kernel docs
There are more files, these have kerneldocs available. The rest of the files are in net/mac80211/.
File location / kerneldoc (kernel-doc warnings)