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 
monitor mode on the hardware. (2006-12-18) I merely updated it so that 
monitor interfaces output radiotap whether or not the driver supports.

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

1. Make it easy to flip monitor mode on and off in drivers and support your 
IFF_PROMISC suggestion.
2. Make the use of radiotap by drivers configurable independently of monitor 
mode.
3. Report the result of a TX through monitor interfaces after 
ieee80211_tx_status is called. This requires new radiotap definitions.
4. Move things like radar detection and the rest of ieee80211_msg_* to 
cfg/nl80211 if they are necessary.
5. Port hostap and wpa_supplicant to the new interface. Will require some fun 
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 
first two issues should be sufficient to merge the radiotap RX/TX patches. 
After that, 3-6 can be done one by one.

-Michael Wu