WPA-PSK won't exchange keys using interface - wifi0

Jouni Malinen jkmaline
Tue Jul 5 23:41:36 PDT 2005

On Tue, Jul 05, 2005 at 06:50:42PM -0400, Tony Espy wrote:
> Jouni Malinen wrote:
> > On Tue, Jul 05, 2005 at 01:20:17PM -0400, Tony Espy wrote:
> >>i've run into a problem where i can't seem to get wpa_supplicant to 
> >>complete it's key exchange with an AP using WPA-PSK over the wifi0 
> >>interface.  it works just fine if i specify wlan0 as the interface.
> > 
> > Using wifi0 interface for this is not supported, nor expected to work.
> Is there anyway around this?  I posted a question on 03/28 re: using 
> this sort of configuration, and from your response, it sounded like this 
> wouldn't be a problem ( note -- I've attached your original reply ).

No you did not, your earlier question was completely different..

> In my email, I didn't explicitly call out the fact that we were using 
> wpa_supplicant, so that may have been my bad.

.. indeed.. wpa_supplicant with this configuration is indeed the
completely diffenret part. wpa_supplicant needs to receive and send
EAPOL frames and this is not supported through wifi0.

Sure, this could be worked around somehow, but I'm not interested in
using time with this unless someone can first convince me that this is
really something that should be done instead of changing the DHCP client
to behave otherwise.

> My assumption was that the UP/DOWN flag could be used to indicate to the 
> rest of the system that an interface was "online/offline" ( ie. 
> available for IP traffic ).  Apparently the authors of pump made this 
> same assumption.

UP/DOWN for me means whether the device is enabled or disabled. This
seems to match with number of network device drivers in Linux. In case
of wireless devices, this would mean that one will need to complete
reauthentication after setting the interface DOWN and then UP.

In my opinion, DHCP client should not set interface down if it was
already up when the client was started.

> Note -- however that the ethernet driver doesn't behave that way. 
> 'eth0' can be marked down, but will still allow DHCP messages to be 
> broadcast.


What is _the_ ethernet driver? Many Ethernet drivers in Linux 2.6.x
disable interrupts when the interface is set down..

> Would it be possible to modify the driver to allow key exchange to occur 
> even though the interface was marked down?

That does not match with the expected behavior (at least the way I see
it). No packets should be transmitted if the interface is down.

Jouni Malinen                                            PGP id EFC895FA

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