Re: wpi(4) driver in -current

[Matthias Drochner <M.Drochner%fz-juelich.de@localhost>]

smb%cs.columbia.edu@localhost said:
> > Guys, maybe anybody using wpi with netbsd?  
> It's working well for me with WEP on my Thinkpad T61.  I haven't tried
> WPA.

My experience is that it drops out often with WPA.
I've done some tcpdumps and found that there is always a
"deauthenticate" packet sent by the access point. I've
done this with 3 different APs so far:
-a "Fritzbox" DSL modem which sends "unspecified" as reason
 within that packet,
-a german telecom branded "Speedport" which is likely similar
 to the Fritzbox because it has the same ethernet addr prefix,
 also sending "unspecified",
-and a Dlink box which sends a "Michael mic error" or so
 at this point.

There were reports that similar problems occur with other
intel chipset wireless adapters, and it was said that the "ath"
doesn't have these problems.

So my theory, unless proven otherwise, is that the NetBSD
"Michael MIC" code (which is used for WPA/TKIP) has a bug
which makes it deliver incorrect packets in some situations.
The access points detect this and send the "deauthenticate",
where the Dlink firmware seems to do a better job.
"ath" does the MIC in hardware, so it works.
Plain WEP doesn't use Michael MIC, so the theory still holds.

I have to admit that I'm mostly clueless about wireless
encryption schemes - this is all based on observations.

best regards
Matthias




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