|Kernel Developer's Manual
*, struct mbuf *, int
rssi, int noise);
ieee80211com *, struct mbuf *,
int rssi, int noise);
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_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 mbuf chain.
If a received frame must pass through the A-MPDU receive reorder
buffer then the mbuf must be marked with the
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
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
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
|August 4, 2009