kern/111744: if_ath occasionally hangs system with certain broadcom AP chipsets

[bob frazier]

>Number:         111744
>Category:       kern
>Synopsis:       if_ath occasionally hangs system with certain broadcom AP chipsets
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Apr 16 20:50:03 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     bob frazier
>Release:        6.2 STABLE
>Organization:
SFT Inc.
>Environment:
FreeBSD BSDLaptop 6.2-STABLE FreeBSD 6.2-STABLE #0: Fri Mar  9 20:19:08 PST 2007     bobf at BSDLaptop:/usr/obj/usr/src/sys/GENERIC  i386


>Description:
When testing 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.


>How-To-Repeat:
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

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: