Hi,
For various reasons I have been looking into the handling of virtual
monitor interfaces in drivers that link with the mac80211 module.
It is my understanding that monitor interfaces per se. are not "passed
down" to the driver module, and that driver modules should handle the
IEEE80211_CONF_CHANGE_MONITOR flag passed down by the config callback
whenever the set of virtual interfaces changes between having zero and
one monitor member.
Firstly is this assumption correct?
Looking at the drivers in the current mainline kernel that link the
mac80211 modules only a small minority of them hook this event. They are :-
ath/ath10k
ath/ath9k (both ath9k and ath9k_htc)
cw1200
brcm80211/brcmsmac
All the others seem to be doing things with NL80211_IFTYPE_MONITOR in
the vif structure. Is this something to do with the somewhat opaque
comment in mac80211.h?
* @IEEE80211_CONF_MONITOR: there's a monitor interface present -- use this
* to determine for example whether to calculate timestamps for packets
* or not, do not use instead of filter flags!
If my assumptions are true I would expect drivers to do whatever private
interaction with the hardware to enable monitoring at this point. For
example setting up the right frame headers. I also assume that hw
filters are handled separately so that different monitor vifs can have
different flags.
Please feel free to tear this to shreds! I am on a steep learning curve
on this.
I have read most of the docs I could find and studied the code, but
please let me have any suggestions you have for further research.
Thanks
Roger
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