Multiple SSIDs and hardware limitations

Nicolas Calderon nicolas.calderon.asselin at gmail.com
Thu Mar 20 10:06:37 EDT 2014


Hi,

I was trying to set up hostap for multiple ssids. The example
hostapd.conf file was a great resource, as well this wiki page:
http://wiki.stocksy.co.uk/wiki/Multiple_SSIDs_with_hostapd.

I could get the card to broadcast multiple ssids (test, test2), but
was unable to connect to it. In the debug output, I could see the
interface was created but then generated errors:

nl80211: Create interface iftype 3 (AP)
nl80211: New interface wlan0_0 created: ifindex=22
nl80211: Add own interface ifindex 22
Could not set interface wlan0_0 flags: Device or resource busy

I think this is due to the fact that my interface doesn't support
multiple AP, which I didn't know how to verify until I found this
email: http://readlist.com/lists/shmoo.com/hostap/3/15248.html.
Basically, the "valid interface combinations" section of "iw list"
reports the capabilities of the card.

Sample output for an AR9330: http://patchwork.openwrt.org/patch/3778/

Sample output for my Intel Wireless-N 2230:
* #{ managed } <= 1, #{ AP, P2P-GO } <=1,
  total <= 2, #channels <= 1, STA/AP BI must match
* #{ managed } <= 2, #{ P2P-Client } <=1,
  total <= 2, #channels <= 1

I didn't look into the source, and the output is a bit cryptic, but I
think "#{ AP, P2P-GO } <=1" means that I can't do multiple APs.

With all that being said, I though it might be interesting to either
add checks for device capabilities at hostapd startup or tell people
to check the output of "iw list" for device capabilities in the
"Multiple BSSID support" section of the sample hostapd.conf.

Thanks,

--
Nicolas Calderon


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