[PATCH] hostapd: Don't force HT Mixed Mode for non-GF STAs

Helmut Schaa helmut.schaa
Tue Mar 15 08:41:34 PDT 2011

On Tue, Mar 15, 2011 at 4:27 PM, Jouni Malinen <j at w1.fi> wrote:
> On Wed, Mar 02, 2011 at 09:37:11AM +0100, Helmut Schaa wrote:
>> Currently hostapd will force HT Mixed Mode if at least one non-GF STA is
>> associated. This will force _all_ HT transmissions to be protected.
>> 802.11n-2009 doesn't require HT Mixed Mode to be used in case of non-GF
>> STAs but instead the HT information element contains a flag if non-GF
>> STAs are present. All STAs are required to protect GF transmissions in
>> that case. Hence, setting HT Mixed mode if non-GF STAs are present is
>> superfluous.
> I think that this change itself would be fine with the assumption that
> the drivers are able to handle GF protection properly.


> Or well, would
> be even better, if the comment about the function were to be fixed to
> match the implementation.

Could you elaborate please?

> However, while trying to review what exactly
> this function is trying to do, it does not look correct or I'm missing
> something... Where does it verify the capabilities of the local radio
> (i.e., the AP) itself? For example, if the AP does not support GF,
> surely this needs to be indicated somehow..

Hmm, good point.

However, since we mask out the STA HT caps with our own HT
caps during association every GF capable STA would appear as non-GF
capable STA and as such would force the non-GF-STAs-present flag
to be set.


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