Unicast packets stop being transmitted to a particular station, under load, when WPA2 is enabled

Adrian Chadd adrian at freebsd.org
Wed May 14 13:20:40 PDT 2014


Hi,

When you quote frame offsets in a pcap, can you next time use the frame number?

I think your'e referring to 20253, right? That looks like the right frame.



-a


On 12 May 2014 01:21, Avery Pennarun <apenwarr at gmail.com> wrote:
> On Mon, May 12, 2014 at 3:07 AM, Avery Pennarun <apenwarr at gmail.com> wrote:
>> On Mon, May 12, 2014 at 1:05 AM, Ben Greear <greearb at candelatech.com> wrote:
>>> If it's getting on the air, then I think the only way to figure out
>>> what is wrong is to decode the packets and see if they are encrypted
>>> properly or not.  I think there is a way to get wireshark to decode
>>> pkts by feeding it the proper keys, but I have not ever actually tried
>>> doing that.
>>
>> Okay, here is a fairly reduced capture of my wireshark trace:
>> http://apenwarr.ca/tmp/ath10k-utorrent-dropout-v2-reduced.pcapng.gz
>> [...]
>
> From what I can see, the most suspicious part of this trace is an
> 802.11 Action - Add Block Ack Request at time 181.1456.  In a longer
> version of this trace, I can see these occurring sporadically.  Each
> one has a different TI field:
>
> Time 8.367: TID=0
> Time 9.609: TID=6
> Time 156.188: TID=1
> Time 178.076: TID=2
> Time 181.145: TID=3  <-- almost exactly the time of the failure
> Time 190.127: TID=5
>
> I don't know how 802.11 QoS works, but I don't think it makes sense to
> keep negotiating block ack policies with different TIDs.  Also, the
> Block Ack Starting Sequence Number field is always zero; I don't know
> what that does, but it seems weird to me.
>
> Nevertheless, I can certainly see things being ACKed in my wifi
> traces.  I think maybe some incorrect Add Block Ack Request packets
> may be triggering a bug in the wifi driver on my macbook?
>
> IEEE 802.11 wireless LAN management frame
>     Fixed parameters
>         Category code: Block Ack (3)
>         Action code: Add Block Ack Request (0x00)
>         Dialog token: 0x01
>         Block Ack Parameters: 0x1017, A-MSDUs, Block Ack Policy
>             .... .... .... ...1 = A-MSDUs: Permitted in QoS Data MPDUs
>             .... .... .... ..1. = Block Ack Policy: Immediate Block Ack
>             .... .... ..01 01.. = Traffic Identifier: 0x0005
>             0001 0000 00.. .... = Number of Buffers (1 Buffer = 2304 Bytes): 64
>         Block Ack Timeout: 0x0000
>         Block Ack Starting Sequence Control (SSC): 0x0000
>             .... .... .... 0000 = Fragment: 0
>             0000 0000 0000 .... = Starting Sequence Number: 0
>
>
> Thanks,
>
> Avery
>
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