Re: Can we ignore frames with invalid BSSID in IBSS mode?

From: Ben Greear <greearb@candelatech.com>
To: Johannes Berg <johannes@sipsolutions.net>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	ath10k <ath10k@lists.infradead.org>
Subject: Re: Can we ignore frames with invalid BSSID in IBSS mode?
Date: Wed, 30 Sep 2015 08:44:44 -0700	[thread overview]
Message-ID: <560C036C.7000401@candelatech.com> (raw)
In-Reply-To: <1443626224.1859.9.camel@sipsolutions.net>

On 09/30/2015 08:17 AM, Johannes Berg wrote:
> On Wed, 2015-09-30 at 08:07 -0700, Ben Greear wrote:
>>
>> On 09/29/2015 11:46 PM, Johannes Berg wrote:
>>> On Fri, 2015-09-25 at 16:00 -0700, Ben Greear wrote:
>>>> It seems that ath10k ar988X hardware has a bug where the BSSID
>>>> for IBSS AMSDU frames is all zeros.  The 'main' 636 ath10k firmware
>>>> does not seem to use AMSDUs for IBSS, and when I enable it in my CT
>>>> firmware, then I see the breakage.  So, I suspect it is not
>>>> just a simple software/firmware bug.
>>>>
>>>> If I simply ignore the bssid_match check in ieee80211_accept_frame,
>>>> then it seems everything runs fine.
>>>>
>>>> So, I'm curious if anyone knows what sorts of bad things could happen
>>>> if the bssid_match check is ignored?  Maybe bcast/mcast frames could
>>>> be accepted when they shouldn't be in certain cases?
>>>>
>>>
>>> You could end up accepting multicast frames from a different,
>>> overlapping, BSS? Seems like a bad idea.
>>
>> It's definitely not a great idea.
>>
>> In my testing, I always see the first frame of the AMPDU have
>> a proper IBSS BSSID.  Any idea if it would be OK (and even possible)
>> for the driver or stack to detect this and save the BSSID aside
>> for the subsequent frames?
>
> That seems reasonable.

Any idea how this could be done in the stack instead of the driver?

The problem is that this is a receiver-side issue, so even if I manage
to hack the ath10k firmware or driver rx logic, it would not fix any other
IBSS peer connected to ath10k peer.

Thanks,
Ben

>
>> Its not clear to me whether the rest of the AMPDU frames could
>> somehow be interleaved with frames from a different BSSID?
>>
>
> They can't be, at least not without some very strange hacks on the
> transmitter.
>
> johannes
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-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

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