Re: Help tracing NL80211_CMD_AUTHENTICATE as event in IBSS mode

[Antonio Quartulli <ordex@autistici.org>]

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On Tue, Jun 26, 2012 at 07:03:30PM +0200, Johannes Berg wrote:
> On Tue, 2012-06-26 at 12:44 -0400, Will Hawkins wrote:
> 
> > > Huh, now I'm confused, why would it need the authenticate frames for
> > > IBSS? As far as I can tell, it looks at CMD_NEW_STA, which calls
> > > nl80211_new_station_event(), 
> > 
> > This is what I understand as well.
> > 
> > which in IBSS sends EVENT_IBSS_RSN_START to
> > > the supplicant core -- that will trigger the 4-way-handshake. No? Hence
> > > it doesn't need to register for auth frames, it never needs them, since
> > > RSN uses open auth, if any is even used in IBSS at all.
> > 
> > This is where I am still trying to figure out exactly how it works.
> 
> I believe that when the new station is added (NEW_STA event), it will
> simply send out a 1/4 EAPOL frame. Since both do that, I guess it does
> some kind of de-duplication? Whoever sends it first wins or something,
> but I don't really know. Maybe we should take the discussion to the
> hostap list at this point :-)

Yeah, Johannes is right when saying that NEW_STA simply makes wpa_s trigger a
EVENT_IBSS_RSN_START that will start a 4-way handshake.

Auth frames are not used at all in wpa_s for IBSS/RSN. Auth frames are only used
in the kernel to remove and then add again a station from the neighbour list. In
this way wpa_s will first purge that station and then will add it again thanks
to another NEW_STA event.

@johannes: de-duplication? IBSS/RSN assumes that each node runs an authenticator
and a supplicant. Does this mean that we need exactly two 4-way handshakes? Why
should we have a "winner"?

Cheers,



-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara

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