From: Johannes Berg <johannes@sipsolutions.net>
To: Blaise Gassend <blaise@suitabletech.com>
Cc: linux-wireless@vger.kernel.org,
Catalin Drula <catalin@suitabletech.com>,
Alap Modi <amodi@arubanetworks.com>
Subject: Re: QoS Data packets causing massive packet loss in ieee80211_sta_manage_reorder_buf.
Date: Wed, 20 Nov 2013 09:48:48 +0100 [thread overview]
Message-ID: <1384937328.14295.3.camel@jlt4.sipsolutions.net> (raw)
In-Reply-To: <CAPvVjisu-xcZsqHgcTEKsCJFuESDFO-_0KwkgxffyejemHJZcA@mail.gmail.com> (sfid-20131120_094152_985311_4DCD3B9E)
Hi,
> I have been tracing the packets through the code, and it appears that
> the loss happens in ieee80211_sta_manage_reorder_buf. It appears that
> when there are broadcast QoS Data packets, their sequence numbers get
> mixed with non-broadcast QoS Data sequence numbers causing out-of-date
> sequence number conditions to get triggered spuriously.
>
> As far as I can tell broadcast QoS Data packets coming from the AP are
> pretty rare (the other networks I have access seem to use Data packets
> for broadcast traffic from the AP), but are legal. So I'm suspecting
> that the AP is behaving correctly, but is triggering a so-far rare bug
> in mac80211.
> But this problem is likely to become much more widespread if Aruba's
> 802.11ac firmware triggers it.
>
> I'm not a deep 802.11 expert or a mac80211 so I could certainly use
> some help here. I am putting the details I have gathered below, and
> would love any suggestions/advice. Currently, my impression is that we
> might need a special tid_rx for broadcast packets similar to the
> special handling of broadcast packets in ieee80211_parse_qos.
I think we just need to skip reorder processing for multicast, since
they won't be aggregated anyway?
http://p.sipsolutions.net/d00799dd2201676a.txt
Then again I'm not really sure why we didn't do this before??
johannes
next prev parent reply other threads:[~2013-11-20 8:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-20 8:41 QoS Data packets causing massive packet loss in ieee80211_sta_manage_reorder_buf Blaise Gassend
2013-11-20 8:48 ` Johannes Berg [this message]
2013-11-20 10:15 ` Blaise Gassend
2013-11-20 11:01 ` Karl Beldan
2013-11-20 11:06 ` Johannes Berg
2013-11-20 11:16 ` Karl Beldan
2013-11-20 11:25 ` Karl Beldan
2013-11-20 11:39 ` Johannes Berg
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