Message-ID: <4FABCECC.30709@01019freenet.de> (sfid-20120510_162348_978703_67E5BF76)
Date: Thu, 10 May 2012 16:21:00 +0200
From: Andreas Hartmann <andihartmann@01019freenet.de>
MIME-Version: 1.0
To: Ivo Van Doorn <ivdoorn@gmail.com>
CC: "users@rt2x00.serialmonkey.com" <users@rt2x00.serialmonkey.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: Re: [rt2x00-users] [PATCH][RFC/RFT] rt2800: Implement selectable
 support for 802.11w (MFP)
References: <201205100719.q4A7JwVl003140@mail.maya.org> <CAOZOX0VfLrqBwfcqf5qsSnA4EH00-6tmG8te3M-WVAR8NqcFSw@mail.gmail.com> <4FAB9EAE.9090403@01019freenet.de> <CAOZOX0Vax7HTsND=vi+c6vamtvWaWW9omWu1CM-=vWsrAf4fgQ@mail.gmail.com>
In-Reply-To: <CAOZOX0Vax7HTsND=vi+c6vamtvWaWW9omWu1CM-=vWsrAf4fgQ@mail.gmail.com>
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Sender: linux-wireless-owner@vger.kernel.org

Hi Ivo,

Ivo Van Doorn wrote:
> Hi,
> 
> On Thu, May 10, 2012 at 12:55 PM, Andreas Hartmann
> <andihartmann@01019freenet.de> wrote:
>> Hello!
>>
>> Ivo Van Doorn schrieb:
>>> Hi,
>>>
>>> On Thu, May 10, 2012 at 9:19 AM, Andreas Hartmann
>>> <andihartmann@01019freenet.de> wrote:
>>>> This patch adds support for 802.11w for rt2800. This is achieved by
>>>> using the 802.11w implementation in mac80211.
>>>>
>>>> To get this working, it is necessary to disable hw encryption of
>>>> rt2800pci / rt2800usb, because I don't know of any support in hardware
>>>> for 802.11w and therefore let mac80211 do the whole job.
>>>>
>>>> The user can enable 802.11w with the new mod parameter enablemfp.
>>>> Enabling MFP disables hw encryption.
>>>>
>>>> 802.11w is deactivated per default.
>>>>
>>>> Tested with rt2860 and rt3572.
>>>>
>>>> This is a workaround as long as there isn't hardware support implemented
>>>> in the driver.
>>>>
>>>> Signed-off-by: Andreas Hartmann <andihartmann@01019freenet.de>
>>>> ---
>>>> diff -ur compat-wireless-2012-04-26.orig/drivers/net/wireless/rt2x00/rt2800lib.c compat-wireless-2012-04-26/drivers/net/wireless/rt2x00/rt2800lib.c
>>>> --- compat-wireless-2012-04-26.orig/drivers/net/wireless/rt2x00/rt2800lib.c     2012-04-26 22:10:30.000000000 +0200
>>>> +++ compat-wireless-2012-04-26/drivers/net/wireless/rt2x00/rt2800lib.c  2012-05-09 11:37:48.463278177 +0200
>>>> @@ -4519,6 +4519,15 @@
>>>>            IEEE80211_HW_AMPDU_AGGREGATION |
>>>>            IEEE80211_HW_REPORTS_TX_ACK_STATUS;
>>>>
>>>> +       /*
>>>> +        * Enable support for 802.11w in mac80211. hwencryption must be disabled
>>>> +        */
>>>> +       if (!test_bit(CAPABILITY_HW_CRYPTO, &rt2x00dev->cap_flags) && rt2x00dev->mfprequested) {
>>>> +               INFO(rt2x00dev, "802.11w support (MFP) enabled.\n");
>>>> +               rt2x00dev->hw->flags |=
>>>> +                       IEEE80211_HW_MFP_CAPABLE;
>>>> +       }
>>>
>>> Can't the whole patch be simplified into
>>>
>>> if (!test_bit(CAPABILITY_HW_CRYPTO, &rt2x00dev->cap_flags)) {
>>>                INFO(rt2x00dev, "802.11w support (MFP) enabled.\n");
>>>                rt2x00dev->hw->flags |=
>>>                        IEEE80211_HW_MFP_CAPABLE;
>>> }
>>
>> This would surely be possible, but it wouldn't be possible any more to
>> run the driver w/o MFP support as long as hw encryption is disabled.
>>
>> Additionally, I would like to have an additional comment added to
>> nohwcrypt, which mentions, that activating nohwcrypt enables MFP, like:
>> "Disable hardware encryption, enable MFP." to let the user know, how to
>> enable MFP.
> 
> I am wondering what the usecase would be for having an option to disable MFP?
> Isn't that a feature which technically should be enabled by default and in the
> userspace you have the configuration to use it or not?

It's the same idea as behind the nohwcrypt switch. If there are problems
with the feature in a special case, you have the possibility to disable it.
My understanding of nohwcrypt is to have a fallback mode, which I didn't
want to touch. That's all.


Regards,
Andreas