Linux Wireless

Radiotap is a de facto standard for 802.11 frame injection and reception. Details of radiotap can be found on its new website.

http://www.radiotap.org/

Linux has started to embrace radiotap on its drivers and driver APIs. Relevant files:

XXX: move ieee80211_radiotap.h to kerneldoc

• include/net/ieee80211_radiotap.h - Our definitions for its support
• include/net/cfg80211.h (kerneldoc)- iterator support for possible radiotap arguments
• include/net/mac80211.h (kerneldoc) - mac80211 support for radiotap

mac80211 supports receiving radiotap headers before the actual 802.11 frame. The driver informs mac80211 when it adds a radiotap header by enabling the RX_FLAG_RADIOTAP flag on flag member of struct ieee80211_rx_status. When a driver is done with a frame it passes it to mac80211 via ieee80211_rx.

mac80211 informs drivers it wants radiotap headers in its received skbs during ieee80211_open(), the device's open routine (dev→open). It does this when the type of interface being opened is of type NL80211_IFTYPE_MONITIR, a monitor interface. It informs the driver by enabling IEEE80211_CONF_RADIOTAP on struct ieee80211_hws struct ieee80211_conf flags Sequentially, mac80211 will disable this flag during ieee80211_stop() (dev→stop) for NL80211_IFTYPE_MONITOR interface types.