Re: [GNUnet-developers] [Battlemesh] wifibroadcast

[Simon Wunderlich]

Hi Daniel,

On Friday, April 21, 2017 8:52:28 PM CEST Daniel Golle wrote:
> 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

Yup, Sven was so kind and helped with this. :D

I'm experimenting with some opportunistic routing ideas ...

> 
>     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 :)

Excellent! Good luck!

Cheers,
      Simon

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