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117 lines
4.0 KiB
Groff
117 lines
4.0 KiB
Groff
.\"
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.\" Copyright (c) 2004 Bruce M. Simpson <bms@spc.org>
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.\" Copyright (c) 2004 Darron Broad <darron@kewl.org>
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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_INPUT 9
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.Os
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.Sh NAME
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.Nm ieee80211_input
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.Nd software 802.11 stack input functions
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.Sh SYNOPSIS
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.In net80211/ieee80211_var.h
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.Ft void
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.Fo ieee80211_input
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.Fa "struct ieee80211_node *"
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.Fa "struct mbuf *"
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.Fa "int rssi"
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.Fa "int noise"
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.Fc
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.Ft void
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.Fo ieee80211_input_all
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.Fa "struct ieee80211com *"
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.Fa "struct mbuf *"
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.Fa "int rssi"
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.Fa "int noise"
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.Fc
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.Sh DESCRIPTION
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The
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.Nm net80211
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layer that supports 802.11 device drivers requires that
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receive processing be single-threaded.
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Typically this is done using a dedicated driver
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.Xr taskqueue 9
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thread.
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.Fn ieee80211_input
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and
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.Fn ieee80211_input_all
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process received 802.11 frames and are designed
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for use in that context; e.g. no driver locks may be held.
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.Pp
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The frame passed up in the
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.Vt mbuf
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must have the 802.11 protocol header at the front; all device-specific
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information and/or PLCP must be removed.
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Any CRC must be stripped from the end of the frame.
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The 802.11 protocol header should be 32-bit aligned for
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optimal performance but receive processing does not require it.
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If the frame holds a payload and that is not aligned to a 32-bit
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boundary then the payload will be re-aligned so that it is suitable
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for processing by protocols such as
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.Xr ip 4 .
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.Pp
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If a device (such as
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.Xr ath 4 )
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inserts padding after the 802.11 header to align
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the payload to a 32-bit boundary the
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.Dv IEEE80211_C_DATAPAD
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capability must be set.
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Otherwise header and payload are assumed contiguous in the mbuf chain.
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.Pp
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If a received frame must pass
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through the A-MPDU receive reorder buffer then the mbuf
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must be marked with the
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.Dv M_AMPDU
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flag.
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Note that for the moment this is required of all frames received from
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a station and TID where a Block ACK stream is active, not just A-MPDU
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aggregates.
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It is sufficient to check for
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.Dv IEEE80211_NODE_HT
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in the
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.Vt ni_flags
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of the station's node table entry, any frames that do not require reorder
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processing will be dispatched with only minimal overhead.
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.Pp
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The
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.Vt rssi
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parameter is the Receive Signal Strength Indication of the frame
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measured in 0.5dBm units relative to the noise floor.
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The
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.Vt noise
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parameter is the best approximation of the noise floor in
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dBm units at the time the frame was received.
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RSSI and noise are used by the
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.Nm net80211
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layer to make scanning and roaming decisions in station mode
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and to do auto channel selection for hostap and similar modes.
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Otherwise the values are made available to user applications
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(with the rssi presented as a filtered average over the last ten values
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and the noise floor the last reported value).
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.Sh SEE ALSO
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.Xr ieee80211 9
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