wpa_supplicant can't find hidden SSID

Chuck Tuffli Chuck.Tuffli at dspg.com
Mon Mar 23 10:04:52 EDT 2009


I ran into a problem that sounds similar to this with our driver which
was ultimately caused by the Linux Wireless Extensions.

Some AP implement hidden SSID by setting the SSID to 32 NULL characters.
The wireless extensions code in the kernel (ioctl_standard_iw_point() in
net/wireless/wext.c) determines if a WEXT client is using compatibility
mode (i.e. adds an extra terminating NULL character on SSID - the
behavior before version 21) by checking if the last character is NULL,
and strips off this byte if present. The problem then becomes that when
using WE versions 21 and later, the SSID supplied to the driver (31 NULL
characters) doesn't match the SSID seen on air (32 NULL characters) and
our driver wouldn't associate. Note that if you use a version of WE
prior to 20, this isn't an issue because the supplicant (and all the
wireless tools for that matter) will add a sacrificial 33'rd NULL
character to the string prior to passing it to the kernel.

I sent out a question about this behavior and patch fixing it to some of
the maintainers, but never received a response. Can you try compiling
the supplicant with an earlier version of WE to see if this fixes your
problem?

---chuck

> -----Original Message-----
> From: hostap-bounces at lists.shmoo.com 
> [mailto:hostap-bounces at lists.shmoo.com] On Behalf Of Jouni Malinen
> Sent: Thursday, March 19, 2009 11:10 AM
> To: hostap at lists.shmoo.com
> Subject: Re: wpa_supplicant can't find hidden SSID
> 
> On Thu, Mar 19, 2009 at 05:05:01PM +0000, planetf1 wrote:
> 
> > So driver issue likely? (in the context of a nasty AP anyway)
> 
> Sounds like a driver issue to me. Which driver version are 
> you using? If the driver does not send out a Probe Request 
> with the specific SSID you are trying to use, it won't be 
> able to use this network.
> 
> -- 
> Jouni Malinen                                            PGP 
> id EFC895FA
> _______________________________________________
> HostAP mailing list
> HostAP at lists.shmoo.com
> http://lists.shmoo.com/mailman/listinfo/hostap
> 
> ______________________________________________________________________
> DSP Group, Inc. automatically scans all emails and 
> attachments using MessageLabs Email Security System.
> _____________________________________________________________________
> 

______________________________________________________________________
DSP Group, Inc. automatically scans all emails and attachments using MessageLabs Email Security System.
_____________________________________________________________________


More information about the HostAP mailing list