Comment 41 for bug 1480877

And more detail...

So looks like the double wpa_supplicant signals are harmless ( other than wasting bandwidth ) as the NM's supplicant manager uses the correct 'org.freedesktop.DBus.Properties' interface when it creates the proxy for each new BSS.

It looks like a change introduced by the patch '0002-wifi-cull-the-scan-list-before-signalling-ScanDone-b' may be the culprit at the NM level. The intention was to ensure that the 'last-seen' property was updated for all APs in the scan list before the 'ScanDone' signal is generated. So, in nm-device-wifi.c::scan_done_cb(), a schedule_scanlist_call() was turned into a direct call to cull_scan_list(). Also, the cull_scan_list() function was changed to update last_seen for every AP in the current list.

There are a few other places though that trigger update_last_seen() calls. Both bss_new_cb() and bss_updated_cb() call schedule_scanlist_cull() before returning. Also bss_updated_cb() also calls update_last_seen() directly!

schedule_scanlist_cull() guards against duplicate scheduling, and uses a 4s timer to schedule the next call to cull_scan_list().

Note, update_last_seen() was modified to guard against setting the property if the value hasn't changed.

So... the original code would get a scan_done_cb() and schedule a scan_list cull. Next it would get a series of new and/or updated bss callbacks which each would schedule their own cull. You see where I'm going with this... In theory, all of these would just result in a single scan_list cull which didn't even touch the last_seen ( it was only updated by bss_updated ). With the current code, at least two calls to scan_list_cull() occur after a scan. Also, it's possible that a direct modification of last-seen in bss_updated_cb () could also contribute some extra signals depending on timing...

I *think*, the correct thing to do is to leave scan_done_cb() as the sole place that updates last_seen. This will prevent duplicate signals for the time being.

It still remains to be seen whether we can get rid 'last-seen' altogether.