On Fri, 2017-09-22 at 12:09 +0200, Richard Schütz wrote:

quoted

The way I see it, this would make us assume that all 2.4 GHz
clients support ERP in IBSS, which may not be true?

I disagree. On a HR/DSSS PHY this would still only return HR/DSSS
rates because there should not by any ERP rates present in sband-

quoted

bitrates in the first place.

Sure, but that means that if you're an ERP PHY (which all users of this
code are likely to be), you'd assume that *everyone else* you're
talking to also is - and that's not necessarily desired.

The reason for suggesting this change is that the basic rate set for
a mesh STA is initialized with this function if not explicitly
configured beforehand.

Exactly! So if you mark all the rates as basic that are mandatory for
you, you can never peer mesh with a HR/DSSS PHY. Now, that's probably
unlikely to happen - but for IBSS I'd argue it's reasonable, and the
same would happen there afaict.

IEEE Std 802.11-2016 (10.7.4 Basic rate set, basic HT-MCS set, and
basic VHT-MCS and NSS set for mesh STA) states: A mesh STA shall not
establish a mesh peering with a mesh STA using a different
BSSBasicRateSet (see 14.2.7 and 14.2.8). The SME of a Mesh STA should
use the mandatory PHY rates as the default BSSBasicRateSet in the
MLME-START.request primitive to reduce the risk that a candidate peer
mesh STA utilizes a different BSSBasicRateSet.

"Should" isn't "shall"

Selecting only HR/DSSS mandatory rates for a mesh STA default basic
rate set on an ERP PHY violates this requirement in my opinion. 

It does seem to violate the "should", but arguably that's just a
configuration choice.

wpa_supplicant explicitly configures all ERP mandatory rates for ERP 
mesh points in its default configuration, whereas iw relies on the 
kernel to do the selection. This currently leaves us with the 
unfortunate situation that you can not join such a mesh BSS created
by wpa_supplicant using iw without further configuration and the
other way round.

So now we've finally gotten to the bottom of why you're doing all this?

Anyway, I disagree with the patch. I can get behind a patch changing
the mesh code, but not in a way that affects the IBSS like this.

johannes