From: Michael Wu <flamingice@sourmilk.net>
To: Johannes Berg <johannes@sipsolutions.net>
Subject: Re: [PATCH 0/4] Try #5: Radiotap on Monitor Mode interfaces for rx and tx
Date: Thu, 22 Mar 2007 18:58:04 -0400
Cc: andy@warmcat.com, linux-wireless@vger.kernel.org,
	John Linville <linville@tuxdriver.com>
References: <20070320103955.600509703@warmcat.com> <1174500637.3944.9.camel@johannes.berg>
In-Reply-To: <1174500637.3944.9.camel@johannes.berg>
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On Wednesday 21 March 2007 14:10, Johannes Berg wrote:
> Ok so people don't want to have this in cfg80211, all the better for me
> since it's less work.
>
> I urge you to solve the issues with this injection interface, we've
> established that you can use packet filters to grab only management
> frames but monitor interfaces definitely still interact very badly with
> power management, and when the hardware has a BSS filter then this will
> also be disabled with a monitor interface (if monitor during operation
> is supported) which again puts more load on the host.
>
> I have previously suggested to use the IFF_PROMISC bit for this, but
> this will also need good driver/stack API since currently drivers that
> support monitor during operation will just turn off BSS filters and such
> when a monitor interface is added. That will have to be changed in
> drivers as well.
>
Note that my patch predates the suggestion that IFF_PROMISC be used to turn=
 on=20
monitor mode on the hardware. (2006-12-18) I merely updated it so that=20
monitor interfaces output radiotap whether or not the driver supports.

This patch series is not meant to replace the management interface. I just=
=20
gave Andy Green the radiotap RX patch so he could do some work in the right=
=20
direction, but that patch isn't complete by itself. (That's why I didn't si=
gn=20
off on it) In particular, patches doing these things in addition to what th=
is=20
current patch series does will be needed to finally remove the management=20
interface:

1. Make it easy to flip monitor mode on and off in drivers and support your=
=20
IFF_PROMISC suggestion.
2. Make the use of radiotap by drivers configurable independently of monito=
r=20
mode.
3. Report the result of a TX through monitor interfaces after=20
ieee80211_tx_status is called. This requires new radiotap definitions.
4. Move things like radar detection and the rest of ieee80211_msg_* to=20
cfg/nl80211 if they are necessary.
5. Port hostap and wpa_supplicant to the new interface. Will require some f=
un=20
with packet filtering..
6. Kill the mgmt interface once and for all.

We don't need to replace the mgmt interface at once however. Addressing the=
=20
first two issues should be sufficient to merge the radiotap RX/TX patches.=
=20
After that, 3-6 can be done one by one.

=2DMichael Wu

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