Association and Disassociation info

Jouni Malinen jkmaline
Thu Jan 2 18:27:21 PST 2003

On Thu, Jan 02, 2003 at 06:33:12PM -0500, Andr? Corr?a wrote:

> I need to know, as quickly as possible, when a station disassociates from
> the AP. Looking at /var/log/debug I've found that it takes 5 minutes for
> the AP to realize that the station disassociated.

If the station indeed disassociates (i.e., sends a disassociation
frame), you should get information about this immediately. However, in
many cases, station does not disassociate (e.g., it re-associates with
another AP or it just goes out of range). In these cases, the timeout in
the AP is used to disassociate the station eventually.

> Is there a way for me to know quickly that a STA disassociated? I've
> thought that I may be able to change hostap's code to decrease association
> timeout to 1 minute or less. Are there any implications in doing this?

Station-initiated disassociation ends up in hostap_disassoc() which will
print a log message about this and will send IWEVEXPIRED wireless event.
If you need to also know quickly that a station has moved away (without
disassociating), you could decrease timeout limit. Host AP driver uses
an empty data frame to poll the station when this limit is reached, so
you should only get few more frames and connection should be maintained.
Disassociation is completed only if this data frame is not ACKed.

> Is there a better way to know an station disassociated then looking at
> /var/log/debug or to files created at the /proc/net/hostap/wlan0
> directory?

Yes, if you are using Linux wireless extensions version 15 or newer.
Host AP code will send IWEVEXPIRED wireless event when a station is
disassociated (check, e.g., iwevent for how to receive these events).

Jouni Malinen                                            PGP id EFC895FA

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