How to handle multiple SSIDs with the same BSS

Jouni Malinen j at w1.fi
Wed Dec 23 17:23:29 EST 2009


On Wed, Dec 23, 2009 at 11:07:07PM +0100, Witold Sowa wrote:
> 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.

I would assume the new DBus API is more important at this point and
since no one has complained about the old one, I would just leave it
as-is..

> 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.

In theory, BSSID should be unique, but well, in practice it isn't. Many
APs use multi-SSID configuration where they share the same Beacon frame
for multiple networks. Similarly, hidden SSID may show up as two
different networks in scan results. At least for the time being, I would
be fine assuming that (BSSID,SSID) would be unique identifier.

> Marcel Holtmann pisze:
> > 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.

The only unique identifier for a BSS is very short lived, i.e., the
index to the scan result which is used as an iterator in fetching the
scan results over ctrl_iface. It is unique within each scan, but will
obviously change whenever new scan results are received from the driver.
There is no longer term identifier used for BSSes in wpa_supplicant
outside the DBus use at this point.

-- 
Jouni Malinen                                            PGP id EFC895FA


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