Received-SPF: pass (google.com: best guess record for domain of linux-wireless-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH 1/3] nl80211: add monitor mode scan feature
To:     Steve deRosier <derosier@gmail.com>,
        Johannes Berg <johannes@sipsolutions.net>
Cc:     linux-wireless <linux-wireless@vger.kernel.org>, nbd@nbd.name,
        lorenzo@kernel.org
References: <20200303115017.9845-1-markus.theil@tu-ilmenau.de>
 <8445336f5d71533acf17b6c53fcc88e7faeab3bf.camel@sipsolutions.net>
 <CALLGbRKPCSZW8PFQXat+_=+iD_ED81j16vNtTbF=KW-B-tTWPQ@mail.gmail.com>
From:   Markus Theil <markus.theil@tu-ilmenau.de>
Autocrypt: addr=markus.theil@tu-ilmenau.de; keydata=
 mQINBFcopAYBEADBcwd5L8+T0zgqq4kYY4nQt6CYh5sOalHdI3zNE6fWbRbzQwViIlC9Q0q/
 ys+nMmQajMWHalsgcdeVSQ2GJ/06qhtogCpmL3d2/GdlvVROh33zeqwqevscKvPH5i7oiBhh
 dMs8/5g89q4aTYtyaausy8qQbv3Q8BCVkwFW2pEcqfxNKgWi/8nM2A3powNA9gzCR2rmoGyd
 nvQNkk0MCwT8JSGnUkiEYEkWF4aIr3XToavpn+OMIIIizcDzRwU5NBmC3Q07PQTn8Srr+rJQ
 DF65vgaoI8G7wlNLQYavL1uFX1LVMP1jVr6GMOczeURqiF/QSuHCdyT3R8P3Qknc74tGT2Ow
 EbxllMnk1gvSfGQq47EYIvuXFyMUWOjjtgP+NxryXVAvQBmuqWWjRjfqMSx9URhvB/ZMQLbZ
 LUPNW0Whl/vOQdxVbEMQOSKhKYoWKeCDe7567sEi02bMScvr6ybKBvRMs71hT1T+HFcBE/IJ
 g3ZX+6qRzs+XKLTFGipRbRiLYKKNR+UM/sNc/w+3BTowB9g/cQukrITvb792T4/IPBJzpEry
 9eZFhFTlIqggy/fGrpZkEpEsOyOWYlRyseETvNdrdeVG7dRGPj68jKUWTVcAaAAiu8WhgnvG
 4tvpaORUhjdg4DfkbE9b9lvYkeesFsE0bUAd5z2DeVbtR0QBUwARAQABtClNYXJrdXMgVGhl
 aWwgPG1hcmt1cy50aGVpbEB0dS1pbG1lbmF1LmRlPokCPQQTAQoAJwUCVyikBgIbAwUJB4Yf
 gAULCQgHAwUVCgkICwUWAgMBAAIeAQIXgAAKCRBt3CLaT/oEE5bzD/94Ezfl7mm57PXniW3m
 yIcjofJXw7YCJOprUon36W2Na2xrH3j8QH/sqkfTyCoj1LWxxDGQs+CQGkZ47cX+H1KqKKSS
 iGoNRV/cvoozWe7cn9bAvR3JkqLxjIi0vp68rs/f6ZI49N7zuZAsSBrXN2/2xIgH+mRoAPyw
 mgzaIXZL87vajXol4TlbMaC7blRs6Q4kzOP7ZjvfM/yxwUsifQltNY4wAEWKXLk67ij9akGO
 FG+y3sHF1HYH3w0sB+mIIN3x4BjYqXSH3XDx4xvCQXWkHmFl1RoQbJDvMjxP5/HXLR3omPjF
 ZpV657Grh/PgonwZ/U6sigaA11pjcPfkYNYkcGyb0OMqSKb3Ke52/bhxv4pPWrKRS7btMhj7
 4zuMDk9V+De3YFXvKGllXBMAA6J8TlY71rlcOWKyBQNLLkUZ7/uAA949GTNzM0fPTRqry5qn
 WCR/ekzm3VyFgjWSun39L1W13bJW8aUu8k5x2KWq4YrdB0TOYZpKSAconOHVxhkEMxLwRUfZ
 B9kEPqlfQY5YYE6ZoZQF38Kvx3VFuAnhf+82PjMMrkQ3g07D3xJlq7xWdq1jrwG1QxmVFS64
 g+oWM9IIFisvVspNrJAEgSGmYgTw+VT3PDP3Gj8sqD32mWb18bVE9I5FyagOewKdLpqcljIi
 Bz8WAuz+RbwX4i/mMrkCDQRXKKQGARAAzTGnHyUtTBcGHMKArcGiVnCB6knTFgU7I1gsoBrc
 J1bo0JRJj1lduYkdm12kC49c4dZtv1CciQIN9UEpalZsB2TXaC/xaDJ2IsZuHLOOaqSSwVg/
 Bs41vMeFYmmwRRN1y6MQRCBobCC6KNuCpgtEmS/v4hurISt+MoPIppjK6E7tJQ0lgtfRHq/M
 HW+Wabw5Nq3OFSaLYC3nRJkoB1Vej8XGO8X6URWnZmL3xcnkIkoH13y2WTO0lJz9tF47t5U2
 +xWrFMR+a6ow/QPL4Wi53IqhXDqa6OUzDAUuplZOm71VhwsEkk6u0YjzNRbgAYMBh7iye2j/
 4Lf2+YUB8+uKimpsEwW0nR85sKCQm102Zb9+1bYXPuIIP9HbVNy77X4aM9V0W48zBTqWZzh8
 2i0oq8z1xN3qeuZbAXnzelKZvE1wM9cLQ3YHA629J2OGe3dkv2+untuyj6KMCEU3+vp6j7TX
 hKf+jy3PIrQcQmzMTs7xnkEm5LvbAtaZLrg4OGYjSpvH4bKsLA3sNGt5Xqsuqh5dsO7ccX1G
 nfY7Ug8UyNT5/0gZVkOileTQl0KtgwO9VBXAdrmMPHFldRn3dGNiGlCbxnsaNQDfQwTFmDu0
 1TjzwC4byWLQT+C7yCTk8h9q0NwmCJ5yG7Fe7VUUpA+ZVLyMSt+tSpH8v3n+3I2AKoMAEQEA
 AYkCJQQYAQoADwUCVyikBgIbDAUJB4YfgAAKCRBt3CLaT/oEE7lZEACgrOxRaCQ7D5Rc4BOA
 N4VDIQqVch8X3pBE/k/v3UopkgmYnP4RlhegWr4wp2E6Vuyt8nwnZs3WhxQENfMjd5rV3WhG
 k5ib+pmLvtAht5j8jfP5+UKUTvX1a6oMi98PT8PuQ70oKM7T/KN+RpXIHoz/2Dgde1RQpwKC
 XWtkU9tBF87fE8FfwuqS6myOfd8zc6fOVV/fxmTXVC8qA7tB+0tOSDHB80GRYwnlumChOtOB
 Np8ABFWryE2e6mZZnp9Tpd1A74B45z6l445f5BixGLExAOoTJNA2k0JWx79/2Yi+pwTnQMzW
 QBLa48MnL3DUlVlahz1FZfGbA2U5NARS8iRdUhCaHL0Lph8HxWJwYA5w2afyCCwRD7xFo44V
 jsCNbqtZ6TrFARJdrbeWQl3RZ4Y+uuvN9mgvttVenAbx5d68IariYtXashucQeIMoqIloHTN
 sJDaupNm6+A9T3Re5yXmZsrWSxEEEGv1Bh+5DH6vauP0Ng0ebZ4c6jXfgLpPnAUWlV0rnmrJ
 q9141nbyLRYAhUXxiqajb+Zocp2Am4BF19rBUa1C78ooye9XShhuQvDTB6tZuiYWc24tiyqb
 IjR1hmG/zg8APhURAv/zUubaf4IA7v5YHVQqAbpUfb6ePlPVJBtVw2CwXFrGwnqDFh82La8D
 sGZPq8zmOtvOyZtafA==
Message-ID: <fe471ae5-bebf-a673-48ee-f06c47f3721d@tu-ilmenau.de>
Date:   Wed, 4 Mar 2020 10:34:07 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.5.0
MIME-Version: 1.0
In-Reply-To: <CALLGbRKPCSZW8PFQXat+_=+iD_ED81j16vNtTbF=KW-B-tTWPQ@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk


On 3/3/20 10:59 PM, Steve deRosier wrote:
> On Tue, Mar 3, 2020 at 1:28 PM Johannes Berg <johannes@sipsolutions.net> wrote:
>> On Tue, 2020-03-03 at 12:50 +0100, Markus Theil wrote:
>>> Back in 2007 "mac80211: don't allow scanning in monitor mode"
>>> (f27b62d3e7ec) disabled scanning in monitor mode, because hw
>>> controlled by the zd1211rw driver got confused during this operation.
>>>
>>> Nevertheless, it can be useful to scan in monitor mode, e.g.
>>> when building a tool which processes scans, channel surveys and
>>> monitors the channel passively in monitor mode.
>> Hmm. I'm not really sure that this makes sense.
>>
>> You're in monitor mode, so you won't get any scan processing as such
>> (you will not be able to use nl80211 to retrieve the results!), and
>> there will be a lot of confusion over sending probe requests (the code
>> now looks like it would in fact attempt to do so ... but how?).
>>
> Additionally, I don't see what this solves for sure.  At least on an
> ath10k device I've been using, I can have two interfaces on one phy
> (phy0), wlan0 and mon0, and I can issue a `iw wlan0 scan` and it works
> famously and then capture fine on mon0. Granted, I haven't tried doing
> a scan while at the same time am actively capturing, but I wonder of
> the meaning of that anyway as the capturing radio would have to then
> go off channel and issue probe requests etc., sort of screwing up my
> capture for that time period.  But anyway, can you not do this on your
> radio?
>
> - Steve

I was not able to use this combination of interfaces, when only interested in monitoring networks.
The STA VIF can only scan when its put up, but then I cannot choose the operating frequency of the
monitor interface freely. Sure, I can build workarounds, like changing the interface type when I need
an active scan and chaning it back to monitor mode afterwards, but this also seems not very clean.

Markus