nl80211, wext, dhclient

Simon Kitching simon at
Fri Sep 4 16:33:40 EDT 2015

On 09/04/2015 08:54 PM, Dan Williams wrote:
> On Fri, 2015-09-04 at 20:47 +0200, Simon Kitching wrote:
>> On 09/04/2015 06:26 PM, Dan Williams wrote:
>> Ok, found the triggering factor. The nl80211 driver doesn't work with a
>> hidden SSID. As soon as I switched my router to broadcast the id (and
>> updated wpa_supplicant config to match), that driver works fine. Is that
>> expected?
> Does it work if you remove ap_scan=2 from the config file?  That's
> typically not needed when you have "scan_ssid=1" and a non-broken
> driver.
You are right: using ap_scan=1 and removing ap_scan completely both work.

I added ap_scan=2 due to various advice on the internet, and due to 
comments in the wpa_supplicant sourcecode.

 From wpa_supplicant/config_ssid.h:
      * scan_ssid can be used to scan for APs using hidden SSIDs.
      * Note: Many drivers do not support this. ap_mode=2 can be used with
      * such drivers to use hidden SSIDs.

 From wpa_supplicant/config.h:
      * 2: like 0, but associate with APs using security policy and SSID
      * (but not BSSID); this can be used, e.g., with ndiswrapper and NDIS
      * drivers to enable operation with hidden SSIDs and optimized roaming;
      * in this mode, the network blocks in the configuration are tried
      * one by one until the driver reports successful association; each

The bits about "can be used with such drivers to use hidden SSIDs", 
"enable operation with hidden SSIDs" and "tried one by one until the 
driver reports success" seemed to apply.

I guess I misinterpreted the comments :-(

So the only outstanding issue is a minor one: that wext works with 
"ap_scan=2" but nl80211 does not (and fails without error-message).

Many thanks for your help.


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