Re: [RFA] HE support

[Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>]

On Tue, 2018-01-30 at 09:25 +0100, Johannes Berg wrote:
> 
> http://www.radiotap.org/fields/HE-MU

Ugh, this yet again turned out to be incomplete - I missed that the RU
stuff is duplicated for 160 MHz transmissions, so this can only capture
one of the 80 MHz parts.

Probably the best way to solve this would be just change the field to
the structure

u16 flags1
u16 flags2
u8  RU[8]

and then use up all the reserved bits for the needed known/center 26-
tone bits (need an additional 6 bits, which we _just_ have).

However, this means that the wireshark that has parsing for this this
will be incompatible with the field generated by future sniffers, in
particular if we also have the HE-MU-other-user field included things
will get completely messed up.


Another way to solve this would be to include the HE-MU field twice in
the capture, but that's awkward to do in radiotap (extended presence
bitmaps etc.) and also it would duplicate some information and it
wouldn't be clear what to generate - so I don't think this is feasible.

The best way may be to declare this failed and just use a new bitmap
index, and have bit 24 just be empty in the future?


What do you think? Could wireshark do a point release of 2.6.x and 2.5.x
to include the changes? Or perhaps we could just say that 2.5.x would
just be broken for this, and people should upgrade for HE?

johannes