Skip site navigation (1)Skip section navigation (2)
Date:      Mon, 16 Apr 2007 13:56:13 -0700
From:      Bob Frazier <bobf@mrp3.com>
To:        freebsd-bugs@freebsd.org
Subject:   if_ath driver bug, causes hang with certain access points
Message-ID:  <4623E2ED.5040807@mrp3.com>

next in thread | raw e-mail | index | archive | help
[I attempted to submit this using the problem report form but it was not responding 
after I submitted it]

FreeBSD version (uname -a)
FreeBSD BSDLaptop 6.2-STABLE FreeBSD 6.2-STABLE #0: Fri Mar  9 20:19:08 PST 2007 
bobf@BSDLaptop:/usr/obj/usr/src/sys/GENERIC  i386


Problem description:

When running access points that use broadcom chipsets (such as the Linksys 300N or 
WRT54GS), the if_ath driver will occasionally hang when using an Airlink 101 cardbus 
device (Atheros 5212).  The problem typically occurs when a MIMO capable AP (Linksys 
300N) or speedboost capable AP (WRT54GS) is being used at close range and the 
Atheros-based card is NOT associated (only scanning or packet-sniffing via WireShark). 
I have speculated that it may be due to speedboost or the MIMO packets having a negative 
effect on the if_ath driver, since this problem does not occur with any other access 
points to my knowledge.  Anecdotally it may also happen if the access point is 
malfunctioning, sending bad or partial packets, or when there is a LOT of interference 
(aircraft radar, other access points), but I have only observed this happening with the 
speedboost-capable or MIMO access points running at close range.


Steps to reproduce problem:
a) activate a Linksys 300N (configured for MIMO g operation) or WRT54GS access point 
(with speedboost enabled), but do not associate with the AP.
b) enable the 'ath' device via ifconfig, choose a non-existent ssid (so it does
    not associate) and do a scan, similar to the following command
      ifconfig ath0 up ssid x scan
    repeat this several times, as needed



FYI - the probability of 'malformed packets' due to 'work in progress' code is very 
high, so that could be part of the problem.  However, even with a malformed packet, the 
if_ath driver shouldn't hang.




Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4623E2ED.5040807>