ieee80211_input (9)

Leading comments

Copyright (c) 2004 Bruce M. Simpson <bms@spc.org>
Copyright (c) 2004 Darron Broad <darron@kewl.org>
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 conditio...

(The comments found at the beginning of the groff file "man9/ieee80211_input.9freebsd".)

NAME

ieee80211_input - software 802.11 stack input functions

SYNOPSIS

In net80211/ieee80211_var.h Ft void Fo ieee80211_input Fa struct ieee80211_node * Fa struct mbuf * Fa int rssi Fa int noise Fc Ft void Fo ieee80211_input_all Fa struct ieee80211com * Fa struct mbuf * Fa int rssi Fa int noise Fc

DESCRIPTION

The net80211 layer that supports 802.11 device drivers requires that receive processing be single-threaded. Typically this is done using a dedicated driver taskqueue(9) thread. Fn ieee80211_input and Fn ieee80211_input_all process received 802.11 frames and are designed for use in that context; e.g. no driver locks may be held.

The frame passed up in the Vt mbuf must have the 802.11 protocol header at the front; all device-specific information and/or PLCP must be removed. Any CRC must be stripped from the end of the frame. The 802.11 protocol header should be 32-bit aligned for optimal performance but receive processing does not require it. If the frame holds a payload and that is not aligned to a 32-bit boundary then the payload will be re-aligned so that it is suitable for processing by protocols such as ip(4).

If a device (such as ath(4)) inserts padding after the 802.11 header to align the payload to a 32-bit boundary the IEEE80211_C_DATAPAD capability must be set. Otherwise header and payload are assumed contiguous in the mbuf chain.

If a received frame must pass through the A-MPDU receive reorder buffer then the mbuf must be marked with the M_AMPDU flag. Note that for the moment this is required of all frames received from a station and TID where a Block ACK stream is active, not just A-MPDU aggregates. It is sufficient to check for IEEE80211_NODE_HT in the Vt ni_flags of the station's node table entry, any frames that do not require reorder processing will be dispatched with only minimal overhead.

The Vt rssi parameter is the Receive Signal Strength Indication of the frame measured in 0.5dBm units relative to the noise floor. The Vt noise parameter is the best approximation of the noise floor in dBm units at the time the frame was received. RSSI and noise are used by the net80211 layer to make scanning and roaming decisions in station mode and to do auto channel selection for hostap and similar modes. Otherwise the values are made available to user applications (with the rssi presented as a filtered average over the last ten values and the noise floor the last reported value).

SEE ALSO

ieee80211(9)