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IEEE80211_BMISS(9)	 BSD Kernel Developer's	Manual	    IEEE80211_BMISS(9)

     ieee80211_bmiss --	802.11 beacon miss support

     #include <net80211/ieee80211_var.h>

     ieee80211_beacon_miss(struct ieee80211com *);

     The net80211 software layer provides a support framework for drivers that
     includes handling beacon miss events in station mode.  Drivers can	dis-
     patch beacon miss events that are recognized in hardware or net80211 can
     detect beacon miss	if the driver dispatches received beacon frames
     through the normal	receive	path.  Software	beacon miss support is espe-
     cially useful when	multiple vaps are operating and	any hardware beacon
     miss support is not available (e.g. operating as an access	point together
     with one or more station mode vaps).

     Drivers should dispatch beacon miss events	recognized in the driver with
     ieee80211_beacon_miss().  This causes some	number of ProbeRequest frames
     to	be sent	to the access point to check if	the association	is still
     alive.  If	no response is received	and roaming mode is set	to
     IEEE80211_ROAMING_AUTO then net80211 will try to re-associate and if that
     fails trigger a scan to look for the access point or another suitable AP.
     When the net80211 state machine is	being operated manually, e.g. by
     wpa_supplicant(8),	then applications are notified of the state change and
     are responsible for handling the work of scanning for a new access	point.
     The number	of beacon miss events (without a ProbeResponse)	is user	set-
     table with	the IEEE80211_IOC_BMISSTHRESHOLD request.

     Software beacon miss detection is enabled per-vap by setting the
     IEEE80211_FEXT_SWBMISS flag.  Typically this is done when a vap is	setup
     when the IEEE80211_CLONE_NOBEACONS	option is supplied to the clone	opera-
     tion.  But	drivers	may also force this when they know they	need help de-
     tecting beacon miss.  When	beacon miss is detected	in software the	event
     is	dispatched without driver involvement.	Note that software beacon miss
     handling is not limited to	station	mode; it can be	used in	any operating
     mode where	beacons	from a peer station are	received.

     wpa_supplicant(8),	ieee80211(9), ieee80211_vap(9)

BSD				August 4, 2009				   BSD


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