92 lines
3.5 KiB
Groff
92 lines
3.5 KiB
Groff
.\"
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.\" Copyright (c) 2009 Sam Leffler, Errno Consulting
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 4, 2009
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.Dt IEEE80211_BMISS 9
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.Os
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.Sh NAME
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.Nm ieee80211_bmiss
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.Nd 802.11 beacon miss support
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.Sh SYNOPSIS
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.In net80211/ieee80211_var.h
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.Pp
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.Ft void
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.Fn ieee80211_beacon_miss "struct ieee80211com *"
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.Sh DESCRIPTION
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The
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.Nm net80211
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software layer provides a support framework for drivers that includes
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handling beacon miss events in station mode.
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Drivers can dispatch beacon miss events that are recognized in hardware or
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.Nm net80211
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can detect beacon miss if the driver dispatches received beacon frames
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through the normal receive path.
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Software beacon miss support is especially useful when multiple vaps
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are operating and any hardware beacon miss support is not available
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(e.g. operating as an access point together with one or more station
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mode vaps).
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.Pp
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Drivers should dispatch beacon miss events recognized in the driver with
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.Fn ieee80211_beacon_miss .
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This causes some number of ProbeRequest frames to be sent to the
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access point to check if the association is still alive.
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If no response is received and roaming mode is set to
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.Dv IEEE80211_ROAMING_AUTO
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then
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.Nm net80211
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will try to re-associate and if that fails
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trigger a scan to look for the access point or another suitable AP.
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When the
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.Nm net80211
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state machine is being operated manually, e.g. by
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.Xr wpa_supplicant 8 ,
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then applications are notified of the state change and are responsible
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for handling the work of scanning for a new access point.
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The number of beacon miss events (without a ProbeResponse) is user
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settable with the
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.Dv IEEE80211_IOC_BMISSTHRESHOLD
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request.
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.Pp
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Software beacon miss detection is enabled per-vap by setting the
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.Dv IEEE80211_FEXT_SWBMISS
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flag.
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Typically this is done when a vap is setup
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when the
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.Dv IEEE80211_CLONE_NOBEACONS
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option is supplied to the clone operation.
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But drivers may also force this when they know they need help detecting
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beacon miss.
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When beacon miss is detected in software the event is dispatched without
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driver involvement.
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Note that software beacon miss handling is not limited to station mode;
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it can be used in any operating mode where beacons from a peer station
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are received.
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.Sh SEE ALSO
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.Xr wpa_supplicant 8 ,
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.Xr ieee80211 9 ,
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.Xr ieee80211_vap 9
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