misc/146425: mwl dropping all packets during and after high usage on 802.11n

[Erik Fonnesbeck]

>Number:         146425
>Category:       misc
>Synopsis:       mwl dropping all packets during and after high usage on 802.11n
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun May 09 06:10:02 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Erik Fonnesbeck
>Release:        8.0
>Organization:
>Environment:
FreeBSD bsd.local 8.0-RELEASE FreeBSD 8.0-RELEASE #0: Sat Nov 21 15:48:17 UTC 2009 root at almeida.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
>Description:
When using the card in 802.11n in access point mode, testing with file copying to or from a Windows system with an 802.11n card (specifically an Atheros 5416-based card in this card) with the other endpoint being accessed over 100 Mbps ethernet, after a short time it started to drop all packets, even after the transfer was stopped.  Before the packet loss, the transfer is typically far below 802.11g's fastest rate.
>How-To-Repeat:
Use mwl as 802.11n access point and copy a file over the network without a speed cap set.
>Fix:
If ampdu is disabled, the packet loss does not occur.  After that it can also at least reach, but not exceed, 802.11g rates.

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