PMK cache sync with driver

Gautam Kotekoppa Ravikrishna Gautam.Ravikrishna at csr.com
Mon Jul 5 13:08:31 EDT 2010


Hi,

 

If my understanding is correct, for drivers that use their own RSN IEs
during association, a PMKID list is kept in the driver. This list is
kept in sync with its own list by the supplicant using add_pmkid,
remove_pmkid calls. Browsing through the supplicant code I cant find
where the driver's PMKID entry is removed when a PMK cache entry is
removed in the supplicant.

One of the problems due to this is when a cache entry expires on the
station, the supplicant removes its own entry. Unaware, driver sends the
corresponding PMKID during reassociation and the AP jumps to 4 way
handshake. Handshake fails as supplicant is unable to find the entry.
This loss of sync leads to endless failed association attempts and stops
only when the AP does a full authentication. Understandably, some APs
never do a full authentication if a valid PMKID is found during
association.

Am I missing something or is this really a problem?

 

Thanks
Gautam



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