Wireless event: cmd=0x8c00 len=20

Jouni Malinen jkmaline at cc.hut.fi
Wed Jun 23 23:24:27 EDT 2004


On Wed, Jun 23, 2004 at 10:31:12PM -0400, Brian J. Murrell wrote:

> The link between my hostap (0.2.3) laptop and my SMC AP with WPA seems
> to go dead every now and then.  Seems like it's a timing issue of some
> kind but the time is long enough that it only usually happens during an
> extended absence from the unit.
> 
> When it happens I see the following on the wpa_supplicant:
> 
>         Wireless event: cmd=0x8c00 len=20

That is IWEVTXDROP, i.e., a packet was dropped because maximum number of
retries failed (did not receive an acknowledgement from the AP). Please
verify kernel log (e.g., 'dmesg') for ay possible errors when the
connection dies.

This may be an interoperability issue with the station firmware and the
currently used roaming mode. I think I can trigger similar problem by
manually triggering a scan (e.g., with 'iwlist wlan0 scan') and not
asking the to join the AP. The station firmware claims that the
connection is still up, but it drops all TX packets.. The connection can
be fixed by triggering join request ('iwconfig wlan0 ap <BSSID>'). If
nothing else, I could add a workaround for this so that wpa_supplicant
could trigger a join request if it detects that each TX packets gets
IWEVTXDROP status..

I'm in process of changing wpa_supplicant to use a different roaming
mode to avoid this issue. This works for many cases, but I still have
couple of open issues with the implementation, so I haven't committed it
yet to the CVS.

> It seems to have just rectified itself this most recent time for the
> first time (perhaps because this is the first time I have been patient
> enough for it to work itself out) and wpa_supplicant went through it's
> authentication business but in the log I also see that the interface
> went down and came back up so maybe the dhcp client prompted
> wpa_supplicant to do it's thing again.

If you think you are seeing something different than the issue I
described above, please send me debug log from wpa_supplicant
(wpa_supplicant -dd ..).

-- 
Jouni Malinen                                            PGP id EFC895FA



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