>Number: 170302
>Category: misc
>Synopsis: [ath] 802.11n frames are not being transmitted with multiple
>rates
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Jul 31 23:50:09 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator: Adrian Chadd
>Release: 9.0-STABLE i386, with -HEAD net80211/ath
>Organization:
>Environment:
FreeBSD marilyn 9.0-STABLE FreeBSD 9.0-STABLE #6 r238210M: Sat Jul 21 16:59:42
PDT 2012
adrian@marilyn:/home/adrian/work/freebsd/stable/9/sys/i386/compile/MARILYN-9-STABLE
i386
>Description:
When doing some debugging, I noticed that the rate control code is not
transmitting frames with multiple rate retries.
For example, with 'sysctl dev.ath.0.debug=2' set (TX descriptor debugging):
Q1[ 0] (DS.V:0xea739000 DS.P:0x1d29c000) L:00000000 D:3958d82c F:0005
Seq: 1904 swtry: 0 ADDBAW?: 0 DOBAW?: 0
417f0242 00008240 00048000 0000008f 0000803a 00000000
00000000 0090000f 00000000 3f000000 3f000000 3f000000 0080292c 00000101
4ccfdabf ffffffff ffffffff 2d80282a 80808080 80808080 80808080 0000056b
[end]
Q1[ 0] (DS.V:0xea739000 DS.P:0x1d29c000) L:00000000 D:3958d82c F:0005 *
Seq: 1904 swtry: 0 ADDBAW?: 0 DOBAW?: 0
417f0242 00008240 00048000 0000008f 0000803a 00000000
00000000 0090000f 00000000 3f000000 3f000000 3f000000 0080292c 00000101
4ccfdabf ffffffff ffffffff 2d80282a 80808080 80808080 80808080 0000056b
[end]
. descriptor field 3 is 0x8f, which shows only one 11n rate (rate attempt #0)
is set.
>How-To-Repeat:
associate to an 802.11n AP.
>Fix:
The TX and rate control paths assume that if RTS/CTS is enabled, multi-rate
retry should be disabled.
This is because of a limitation with the pre-11n chips - the AR5212 supports
multi-rate retry but not with RTS/CTS enabled.
>Release-Note:
>Audit-Trail:
>Unformatted:
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