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.\"
.\" Copyright (c) 2009 Sam Leffler, Errno Consulting
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd August 4, 2009
.Dt IEEE80211_BMISS 9
.Os
.Sh NAME
.Nm ieee80211_bmiss
.Nd 802.11 beacon miss support
.Sh SYNOPSIS
.In net80211/ieee80211_var.h
.Pp
.Ft void
.Fn ieee80211_beacon_miss "struct ieee80211com *"
.Sh DESCRIPTION
The
.Nm net80211
software layer provides a support framework for drivers that includes
handling beacon miss events in station mode.
Drivers can dispatch beacon miss events that are recognized in hardware or
.Nm net80211
can detect beacon miss if the driver dispatches received beacon frames
through the normal receive path.
Software beacon miss support is especially 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).
.Pp
Drivers should dispatch beacon miss events recognized in the driver with
.Fn 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
.Dv IEEE80211_ROAMING_AUTO
then
.Nm 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
.Nm net80211
state machine is being operated manually, e.g. by
.Xr 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
settable with the
.Dv IEEE80211_IOC_BMISSTHRESHOLD
request.
.Pp
Software beacon miss detection is enabled per-vap by setting the
.Dv IEEE80211_FEXT_SWBMISS
flag.
Typically this is done when a vap is setup
when the
.Dv IEEE80211_CLONE_NOBEACONS
option is supplied to the clone operation.
But drivers may also force this when they know they need help detecting
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.
.Sh SEE ALSO
.Xr wpa_supplicant 8 ,
.Xr ieee80211 9 ,
.Xr ieee80211_vap 9
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