wpa_supplicant ad-hoc settings

Per-Henrik Lundblom per-henrik.lundblom
Thu Nov 18 05:50:40 PST 2010

On 2010-11-18 14:35, Jouni Malinen wrote:

> Yes.. It was originally designed to only work in ap_scan=2 mode i.e.,
> when wpa_supplicant does not request scanning. In other words, you would
> configure just one network and set ap_scan=2. The scanning part in
> ap_scan=1 is only for BSS networks.

That part is familiar. I have always been using ap_scan=2 until I tested 
the latest 0.7.3 version.

The problem with this is that I don't think a WLAN driver should need to 
have any information about what surrounding networks. Unfortunately that 
is necessary if the wpa_supplicant doesn't provide provide information 
about BSSID, ESSID, mode and channel to the driver. Especially the 
channel is interesting. Of course, one could add the frequency directive 
to the network configuration but that makes the whole scenario less 

> It would be possible to extend the ap_scan=1 case to handle discovered
> IBSS, i.e., select to use the IBSS network block in such a case.
> However, if there are multiple enabled network blocks, it is unclear
> what should be done if one or more of them are IBSS networks and there
> are no matching scan results. Only the case of having a single enabled
> network block would be clear in such a case.

Yes and no, looking at the current source (0.7.3), after 
wpa_supplicant_pick_network() didn't find a network wpa_supplicant tries 
to create a new network. In the function 
wpa_supplicant_pick_new_network() the list of configured networks are 
traversed for the highest prio network. This should be valid for ad-hoc 
networks too.

Or is it just me who thinks it is wrong that it is up to every WLAN 
driver to handle the ad-hoc case? I know it can be hard to avoid two 
nodes ending up in their own ad-hoc networks instead of joining each 
other. Still, I think better support in wpa_supplicant is a key feature.


Per-Henrik Lundblom
System engineer

connectBlue AB
Norra Vallgatan 64 3V, SE-211 22 Malm?, Sweden
Tel. +46 40 6307100, Direct tel. +46 40 6307126
Cellular +46 733 207126, Fax +46 40 237137
per-henrik.lundblom at connectblue.com

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