How to handle multiple SSIDs with the same BSS

Witold Sowa witold.sowa at gmail.com
Wed Dec 23 17:07:07 EST 2009


Marcel Holtmann pisze:
> Hi Jouni,
> 
>>> BSS 00:1a:a1:53:50:a0 (on wlan0)
>>> 	SSID: Private
>>> BSS 00:1a:a1:53:50:a0 (on wlan0)
>>> 	SSID: Public
>>> When using the wpa_supplicant D-Bus interface, every BSS can only be
>>> listed once and so we either see "Private" or "Public", but never
>>> actually both of them. How should this be handled.
>> I wasn't aware that there is this kind of limitation in the D-Bus
>> interface. It is clearly broken if it cannot include both of those
>> networks.
> 
> from what I have read so far while going through the code, it is not
> possible. The BSSID is used as unique path in D-Bus terms and because of
> that there is no way both networks could be listed at the same time.
> 
Precisely. Path of DBus object representing BSS is based on BSSID. Since
the path must be unique we can't have both networks listed.
I think that we can change a path format quite easy in the new DBus API,
but I'm afraid that changes in the old API may may brake it.
Actually, I was sure that BSSID is an unique identifier, but obviously
we need to think out something else. Is the pair of BSSID and SSID
unique? I'm not sure.

>>> Also looking into the register_bss callbacks, you only get the BSS
>>> address and not the set of IE.
>> I don't know how this mechanism is supposed to be used, but there needs
>> to be a way for fetching more information about the BSS and BSSID by
>> itself is not a sufficient key for identifying which BSS is being
>> queried for (need to have BSSID,SSID pair or some other internally
>> generated identifier which can be guaranteed to be unique).
> 
> Does wpa_supplicant already generate such unique BSS based identifier
> somewhere internally? If not, it might make sense to do so.

It doesn't AFAIK. We generate identifier for DBus usage only.

Witek.


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