Selective scanning

Ajeet Nankani fromkth+hostap
Mon Mar 21 09:31:22 PST 2005

I think it does not matter which command invokes the host scan 
functionality. The problem is if you leave scanning on firmware, it 
scans all allowed(RID-FD10 or rather PDR 0x0303) channels and does not 
give option to the host to specify channels, one must use host scan 
functionality to scan selected channels only.

I think there are 2 ways to do it.
One way is to build another program and run it as daemon, this daemon 
would take control of roaming/handoff, hence can do selective scanning also.
Another way could be to insert this handoff/roaming code in hostap 
module, so that if STA is in host roaming mode 2 then this code takes 
over the roaming, scanning, and selection of new AP.

Marcin and Jouni any comments on above ideas?

Jouni can you point out where would be the appropriate place to 
implement the later option, that is inserting code in hostap to handle 
host roaming mode 2.



Marcin Dabrowski wrote:
> Unfortunately prism2_request_hostscan is invoked only by "iwlist ...
> scanning" command :( So i think it's useless :(
> I'm afraid that the only way is to send probe request and process probe
> responses :(
> Marcin
> I am currently involved more or less into same kind of thing that is
> selective scanning, but only in STA mode.
> My task is to do selective active scanning, can you help me a little bit
> where and what to change in scanning functions and or structures to
> accomplish this scanning of particular channel.
> Do i have to write separate program for that?
> After reading the code, it seems that in file "hostap_ioctl.c" function
> static int prism2_request_hostscan(struct net_device *dev,
>                    u8 *ssid, u8 ssid_len
> is called when the host requests a scan(RID FCE5).
> In that function, channels to be scanned are copied from
> local->channel_mask
>>From inspecting RID-FCE5, it seems that this channel_mask gets channel
> list from RID-FD10, but exactly where in the code this channel_mask gets
> populated with the channel list. Can you point out this?
> Also as this host scan (RID-FCE5) gives option to specify the subset of
> channels to be scanned, so to implement that, only particular different
> channels be scanned every time when it is called, should not be that much
> hard.
> Thanks,
> -ajeet.

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