Problem with acx111

Jouni Malinen j
Sun Mar 30 01:58:54 PDT 2008

On Sat, Mar 29, 2008 at 05:59:32PM -0400, Dan Williams wrote:
> On Sat, 2008-03-29 at 15:43 +0100, Henning Moll wrote:
> > The log is available on (about 450K).
> It almost looks like your AP is rekeying you every second.  Can you
> check what the rekey interval is on the AP?  The logs look normal except
> for the constant AP-induced rekey.

That's not rekeying. It looks like the AP does not receive or accept
message 4/4 for some reason and then re-transmits message 3/4 after a
timeout. Every four or so retries, the client is disconnected and this
starts from scratch (i.e., association and message 1 and 2 of 4-way
handshake). This would be consistent with a WPA2 AP that does not
receive message 4/4.

Taking into account the comment about timing causing differences here, I
would assume this is related to the race condition between sending out
message 4/4 and configuring pairwise keys. Maybe the driver does not
send out msg 3/4 before setting the keys. It would be interesting to see
a wireless capture log showing what exactly was transmitted.

A quick test for confirming the issue (and to provide a workaround for
this) would be to modify wpa_supplicant_process_3_of_4() function in
wpa.c and add some extra delay between sending of message 4/4 and
setting of the PTK. For example, add the os_sleep() call here:

	if (key_info & WPA_KEY_INFO_INSTALL) {
		os_sleep(0, 500000); /* add this line here */
		wpa_supplicant_install_ptk(sm, key);

Jouni Malinen                                            PGP id EFC895FA

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