How to handle multiple SSIDs with the same BSS

Dan Williams dcbw at redhat.com
Fri Dec 25 14:20:55 EST 2009


On Wed, 2009-12-23 at 14:27 -0800, Marcel Holtmann wrote:
> Hi Alan,
> 
> > > >>> 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.
> > 
> > I missed the beginning of this, but the BSSID *should* be unique unless
> > someone is spoofing their mac.  If it is two separate APs each
> > providing the same SSID, the BSSID should be the mac and that should be
> > unique.  If it is virtual APs providing the same SSID, the BSSID should
> > be unique.  I apologize for missing the beginning of this, but
> > something seems strange with the AP setup.
> 
> the BSSID is unique, but an access point can broadcast two different
> SSIDs via the same BSSID.
> 
> This is not about the same SSID. We are talking about different SSIDs
> from the same access point.

This used to be used for Cisco APs where the main broadcasted SSID was
the "public" SSID (Guest SSID) and there was a second non-broadcast SSID
using the same BSSID.  Of course, the public SSID shows up in the scan
results unless you probe-scan for the hidden one.  Yay.

Dan




More information about the HostAP mailing list