Config Methods in WSC IE on P2P GO

Jouni Malinen j
Sun Nov 11 09:11:50 PST 2012

On Tue, Sep 11, 2012 at 09:51:13PM +0900, Masashi Honma wrote:
> Currently the GO sends Probe Response frame which contains WSC IE with Config
> Methods. The Config Methods includes 0x2108 for instance.
> [2] says "Configuration Methods corresponds to the methods the AP supports as
> an Enrollee for adding external Registrars." at 8.2.5 Probe Response
> (D-AP/Registrar) Table 7 . Attributes in WSC IE in the Probe Response frame.

That "for adding external Registrars" should not really be there.. I
agree with the "as an Enrollee" part, but that case be used for learning
the current AP settings and this does not necessarily indicating anyting
about adding an ER.

> [1] says "P2P Group Owner role:Provides WSC Internal Registrar functionality."
> in 2.1 P2P components. And [1] says "P2P Group Owner shall not cross connect
> between the WLAN and P2P Group using layer 2 mechanisms." in 3.2.6
> Communication in a P2P Group.
> So I think these imply "GO could not use external registrar".

It does not say that. Cross connection at layer 2 would be a bridge
connecting the P2P group to another network. WPS ER connection is an IP
connection to another device through any network and it would not need
cross connection at layer 2.

> So I think the Config Methods could be zero.

In theory, this could be the case regardless of whether the GO supports
ERs or not.

> But I know there are confused devices such as using Config Methods in WSC IE
> even if it is a P2P Client. So even if my consideration is acceptable, the code
> should be enclosed by CONFIG_P2P_STRICT macro.

I agree that the Config Method value should not be set to zero by
default because of interop issues. wpa_supplicant could, at least in
theory, enable support for GO acting in WPS Enrollee role, so the Config
Methods values may be valid for use. If there is a good use case for
forcing this to be zero with CONFIG_P2P_STRICT when wpa_supplicant is
not configured with an AP PIN, I could accept a patch to do that.

Jouni Malinen                                            PGP id EFC895FA

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