Re: Unable to Auto Connect with Hidden Wireless Network automatically first time.

[Dan Williams <dcbw redhat com>]

On Fri, 2009-07-10 at 10:10 +0530, sanjeev sharma wrote:
> Hi All,
> 
> I have problem in Auto connecting With my Hidden Wireless first time
> when I configured  through "Connect to Hidden Wireless Network" .
> 
> Step to Reproduce.
> 
> 1:Connect to Hidden SSID through "Connect to Hidden Wireless Network."
> first time after reboot.
> 
> 2:Unchecked Enable NetworkIng option.
> 
> 3:Hidden SSID which was connected earlier will not "Auto Connect".
> 
> 4:If i will repeat step 1 to 3 again it will start Auto Connecting.
> 
> So First time it doesn't get Best auto Connection and fails while Auto Connect.
> 
> One more thing What I observed that while trying First Connection It goes into
> nm_ap_check_compatible() function inside NetworkManagerAp.c and returning from
> these condition because ssid data is NULL.
> 
> if (!nm_utils_same_ssid (nm_setting_wireless_get_ssid (s_wireless), priv->ssid,
> TRUE))
>                 return FALSE;
> 
> and on subsequent operation it doesn't get SSID NULL  and above function
> doesn't return and connected successfully.
> 
> 
> So How we can resolve this issue and why first time it gets SSID NULL.

The real answer is "don't use hidden SSIDs".  Here's some Cisco stuff
that says you shouldn't too:

------------------------------------
http://supportwiki.cisco.com/ViewWiki/index.php/FAQ_on_Cisco_Aironet_Wireless_Security

Q. If I disable SSID broadcast, can I achieve enhanced security on a
WLAN network?

A. When you disable SSID broadcast, SSID is not sent in Beacon messages.
However, other frames such as, Probe Requests and Probe Responses still
have the SSID in clear text. So you do not achieve enhanced Wireless
security if you disable the SSID. The SSID is not designed, nor intended
for use, as a security mechanism. In addition, if you disable SSID
broadcasts, you can encounter problems with Wi-Fi interoperability for
mixed-client deployments. Therefore, Cisco does not recommend that you
use the SSID as a mode of security. 
------------------------------------

But if you are in a situation where hidden SSIDs are unavoidable, NM
should be able to handle connecting to a specific hidden AP if you've
manually requested that NM connect to it before.  NM caches the BSSID of
the AP after you've connected at least once and after that is able to
match that BSSID from the scan results up with the SSID and autoconnect.
This does mean that if you're in an enterprise network, you may need to
manually connect at least once in each distinct location.

Your wireless driver may also be at fault here; NM asks the driver to
probe-scan the access points after you're connected, which helps when
you move between APs, but if your driver doesn't support probe-scanning
(which some out-of-kernel drivers do not) then you won't get that
benefit.

With new improvements in the 2.6.31 and 2.6.32 kernels, the upstream
in-kernel wireless drivers can finally probe-scan up to 4 SSIDs, which
will help the hidden SSID situation quite a bit.

APs *must* respond with their SSID when probe-scanned by a client, which
pretty much defeats the purpose of hiding your AP anyway, since other
computers will pick up that probe-response from the AP and show your
network in their scan results.  So it's pretty much pointless to hide
your network, it's best to just ensure it's protected with WPA2
security.

Dan