Re: [GNUnet-developers] [Battlemesh] wifibroadcast

[Daniel Golle]

Hi Simon,

On Fri, Apr 21, 2017 at 08:24:22PM +0200, Simon Wunderlich wrote:
> On Friday, April 21, 2017 6:45:17 PM CEST Daniel Golle wrote:
> > Hi!
> > 
> > On Fri, Apr 21, 2017 at 04:54:39PM +0200, Benjamin Henrion wrote:
> > > Hi,
> > > 
> > > Just found this project, interesting ideas on using monitor mode:
> > > 
> > > https://befinitiv.wordpress.com/wifibroadcast-analog-like-transmission-of->
> > >  > live-video-data/
> > > 
> > > I think in the past I used adhoc inside monitor mode with aircrack-ng
> > > if I remember.
> > 
> > Promissing indeed, because this might draw some attention to the need
> > to provide the now missing TX rate control for injection.
> > Hence this wifibroadcast project uses patched firmware and/or drivers
> > to force transmission at a fixed bitrate -- it'd be much better if
> > injection mode had a proper way for the transmitter to drive
> > rate-control in software. Other projects (such as GNUnet...) would
> > also greatly benefit from that...
> > Having more wild groth (and even ugly things like firmware patches)
> > does provide a good argument for having support for RADIOTAP_MCS,
> > RADIOTAP_VHT, RADIOTAP_XChannel... in mac80211 also for TX injection.
> > Previously setting the legacy bitrate (up to 54MBit/s single-stream
> > with 20MHz channel width) was supported via the RADIOTAP_RATE header,
> > but even that was dropped a long time ago...
> 
> Huh? I believe both RADIOTAP_MCS and RADIOTAP_RATE are supported fine, at 
> least 
> for ath9k. Not sure about other drivers, but I'm using it extensively on 
> ath9k.

Cool! This is very good news which I wasn't aware of until now!
What are you using it for, if I may ask?

> 
> http://lxr.free-electrons.com/source/net/mac80211/tx.c#L1925

>From what I see it mostly happened in
commit dfdfc2beb0dd7e3a067d2eeacb4623cb48e77658
Author: Sven Eckelmann <address@hidden>
Date:   Tue Jan 26 17:11:13 2016 +0100

    mac80211: Parse legacy and HT rate in injected frames
    
    Drivers/devices without their own rate control algorithm can get the
    information what rates they should use from either the radiotap header of
    injected frames or from the rate control algorithm. But the parsing of the
    legacy rate information from the radiotap header was removed in commit
    e6a9854b05c1 ("mac80211/drivers: rewrite the rate control API").
    
    The removal of this feature heavily reduced the usefulness of frame
    injection when wanting to simulate specific transmission behavior. Having
    rate parsing together with MCS rates and retry support allows a fine
    grained selection of the tx behavior of injected frames for these kind of
    tests.
    
    Signed-off-by: Sven Eckelmann <address@hidden>
    Cc: Simon Wunderlich <address@hidden>
    Signed-off-by: Johannes Berg <address@hidden>


I'll be working on
https://gnunet.org/bugs/view.php?id=3867
in case anyone is looking for me, tell'em I'm busy :)


Cheers


Daniel


> 
> Cheers,
>     Simon