Hostapd to Wpa_supplicant 4 way Handshake Problem

Jouni Malinen j
Wed Aug 27 06:56:51 PDT 2008

On Wed, Aug 27, 2008 at 01:14:08PM +0100, Damon Southworth wrote:

> In this case the AP was a Cisco 1200 series and the EAPOL messages
> containing the key exchange were sent with a QoS header highest priority
> 7 (management) and were very precise in their transmssion times and
> retries. Packets from the station didn't have a QoS header and timings
> varied with the amount of traffic. Has any thought or work been done to
> allow wpa_supplicant to use the 802.11 QoS extensions and improve the
> delivery of the key exchange. I can see there is support in the Madwifi
> driver for QoS but I am unclear as to the correct kernel interface to
> utilise these extensions. Does information on this exist?

There is no easy mechanism for wpa_supplicant to request highest
priority for EAPOL frames. However, d80211 (now net/mac80211) in Linux
kernel started with code that used AC_VO for EAPOL frames in AP mode. I
don't think it was extended to be used in client mode and even the AP
mode case may have disappeared in one of the cleanups from mac80211.
Anyway, it would be reasonable to re-introduce that functionality in
mac80211 to provide better changes of being able to complete re-keying
handshakes when there is lot of low priority traffic in the network.

As far as madwifi driver is concerned, similar change could be done
there (in net80211) since it does not use net/mac80211. The EAPOL frames
can easily be recognized based on ethertype, so there would only need to
be a simple mapping from a specific ethertype to a suitable access
category for WMM.

Jouni Malinen                                            PGP id EFC895FA

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