Subject: Re: [RFC PATCH v3 07/12] iwlwifi: Extended Key ID support (NATIVE)
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     linux-wireless@vger.kernel.org
References: <20190210210620.31181-1-alexander@wetzel-home.de>
 <20190210210620.31181-8-alexander@wetzel-home.de>
 <1a3b6e515c73a2c185e8dad84ab2ebfd8982a6ce.camel@sipsolutions.net>
From:   Alexander Wetzel <alexander@wetzel-home.de>
Message-ID: <e84c30de-28d6-7d1b-0fa3-d1ca466e257b@wetzel-home.de>
Date:   Fri, 22 Feb 2019 21:50:45 +0100
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Am 15.02.19 um 12:52 schrieb Johannes Berg:
> On Sun, 2019-02-10 at 22:06 +0100, Alexander Wetzel wrote:
>> This is not ready for merge and has known issues.
>> The patch is only for discussions to sort out how to handle it correctly!
>>
>> Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
>> ---
>>
>> iwlwifi intel cards had two big surprises:
>>
>> Assuming I did not make some stupid errors it looks like my old
>> "Intel Corporation Centrino Ultimate-N 6300 (rev 3e)" using ucode
>> 9.221.4.1 build 25532 is perfectly fine with two keys uploaded to
>> harware and honoring the keyid in the MPDUs. For a card launched 2011
>> that's a pleasant surprise:-)
> 
> :-)
> 
>> A much shorter test with a modern "Intel Corporation Wireless 8265 /
>> 8175 (rev 78)" using ucode version 36.e91976c0.0 shows what seems to be
>> MPDUs decoded with the wrong key at each rekey and therefore a candidate
>> for the COMPAT support only..
>> So the bad news seems to be, that the modern card dropped the support.
> 
> Probably just a firmware bug.
> 
>> It also seems to force us to add some per-card or per-firmware depending
>> check to decide which card can use the Native Extended Key ID support
>> and use the Compat mode for the rest.
>> Is there any way to find out which cards/firmware can be used with
>> Extended Key ID?
> 
> No, but if you have a good test case we can check out what the firmware
> bug is and fix it. Perhaps not for all, but for the future at least.
> Maybe we can still figure out where it was introduced and thus see where
> it's good to use native mode.

I'll verify if can reproduce the scrambled packets and will provide a 
capture if so. Assuming that confirms the initial finding I'll be able 
to reproduce that at will within minutes with access to a test system 
having a mvm card. (I have some plans which will improve access, but 
looks like that will take some time and efforts.)

For now I handle that as low prio till we have generic Extended Key ID 
support merged and I've had some time to improve my test setup and 
hopefully have better access to a mvm card for testing.

> 
>> I also have tested patch for iwldvm using the Compat mode and I think
>> mvm cards will also work with that.
> 
> No they don't, no firmware is available for that.

So far I only looked at the dvm part of iwlwifi with only minutes spend 
on mvm to port the NATIVE solution from dvm.

Are you saying that mvm cards can't seamless switch a RX/TX key to TX 
only one? mvm seems to support SW crypto as needed and switching RX/TX 
to TX keys is the only other requirement for COMPAT mode.

Alexander