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ieee80211_input - software 802.11 stack input functions
ieee80211_input(struct ieee80211_node *, struct mbuf *, int rssi,
ieee80211_input_all(struct ieee80211com *, struct mbuf *, int rssi,
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. ieee80211_input() and
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 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
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 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 rssi parameter is the Receive Signal Strength Indication of the frame
measured in 0.5dBm units relative to the noise floor. The 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).