hostap passive scanning.

Andrea G Forte andreaf
Thu Feb 10 08:08:22 PST 2005

>Exactly what do you mean with passive scanning?
Passive scanning as opposed to active scanning. The STA listens for 
beacons on each channel periodically in order to decide which AP is the 
best one to connect to. No probe messages are issued at all.

>What is this based on? I wrote that ap_scan functionality is not
>supported in managed mode, not passive scanning in general.. Firmware
>takes care of scanning in managed mode. I don't remember whether there
>was separate options for active vs. passive scanning, but then again, I
>don't really know what functionality you were looking for.
In manual mode "host_roaming  2" we have "more" control on the scanning 
In particular (as you know), in the driver there are two commands for 
forcing the firmware to start the probing part of the scanning 
(_RID_HOSTSCAN) and for forcing the Auth./Ass. part of the scanning 
(_RID_JOINREQUEST). However, the first one is for active scanning only 
(i.e. probes are sent to force APs to answer).
Does the ap_scan functionality send probes on each channel (in which 
case it is active scanning)? Or does it use passive scanning (listens 
for beacons and records the results)?
To be more clear, I would like to know if instead of triggering active 
scanning (sending probes with _RID_HOSTSCAN), I can use the 
hostap_passive_scan function in hostAP to change channel and then use 
(or write if not already there) some other code to listen for beacons on 
each channel and record the APs found with the signal strenght (measured 
from the beacon). All of this while being in Managed mode.

Thank you,

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