[PATCH 24/25] MBO: Always accept BTM request with disassociation imminent bit set

Jouni Malinen j at w1.fi
Sun Feb 21 02:36:45 PST 2016


On Sun, Feb 21, 2016 at 09:19:01AM +0000, Peer, Ilan wrote:
> > From: Jouni Malinen [mailto:j at w1.fi]
> > On Mon, Feb 15, 2016 at 04:53:59PM +0200, Ilan Peer wrote:
> > > According to Multiband Operation specification (r17, section 3.5.2), a
> > > BSS Transition Management Request with the disassociation imminent bit
> > > set should always be accepted.
> > 
> > The spec includes an exception for this: "another AP, if one [is] available".

> Could not find this in the version that I have (v17). What I have states that:
> 
> "On receipt of an unsolicited BTM Request frame with a Disassociation Imminent bit set to one, the MBO STA shall be capable of responding with a BTM Response frame that shall contain the Status Code field (§ 8.6.14.10 in [3]) indicating accept. The MBO STA may also include the Target BSSID field (§ 8.6.14.10 in [3]). When the Disassociation Imminent bit is set to one, the STA shall not reject the Transition Management Request"

I'm reviewing this based on the latest draft (r19). Anyway, that "shall
not reject" is there.. Interesting. IMHO, this looks pretty bad
requirement and as such, if it is needed, it will need to be made
conditional on CONFIG_MBO (if not even something stronger; I'm willing
to ignore pointless requirements in the spec in the default behavior).
I'd say the spec should really be modified to not say that, though,
since there is no such requirement in the IEEE 802.11 standard and it
does not make any sense to be forced to accept something that cannot be
done.

> We were also confused about this :) Maybe the reason for this is that as Disassociation Imminent is set the station does not have much choice and eventually
> would be disassociated so whether it initiated a transition to one of the candidates or not does not really matter.

Sure, but it should be valid behavior for a non-AP STA to wait for the
AP to disconnect it if there are no other options for the non-AP STA to
find alternative connection. Misusing BSS Transition Management frames
to cause disconnection is not really the best approach for something
like this since the AP can already use the standard Deauthentication
frame as notification.

-- 
Jouni Malinen                                            PGP id EFC895FA



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