WPA anomalies in recent Joyride builds

[Jim Gettys]

Dave has just committed a pile of libertas driver fixes to clean up a
bunch of problems with command queueing; they should appear in joy ride
shortly.  It will be worth trying it out again once that has landed,
before jiggering NM's timeouts (which may need adjustment, but doing so
when we have other driver problems seems premature.
                       - Jim

On Tue, 2007-12-18 at 11:36 -0500, Dan Williams wrote: 
> On Tue, 2007-12-18 at 11:14 -0500, Marcus Leech wrote:
> > I use WPA-PSK (WPA personal) at home, and I've noticed anomalies.
> > 
> > One of the big ones is that it keeps re-prompting for the passphrase
> > (this is with Joyride 1438), and tearing-down the
> >   association.   I looked at /var/log/messages while this was going on,
> > and it seems like it starts the association logic,
> >   puts up the password prompt, and then times out the association
> > attempt after 8 seconds--which typically isn't enough
> >   time to type in the passphrase!   It turns out that NetworkManager has
> > a wired-in 8 second timer for
> >   re-association attempts, and 20 seconds for initial association attempts.
> 
> This only comes into play when there's an ongoing _connection_, it
> doesn't come into play when you're typing in the password.  When NM
> needs a password from you, it pauses the connection process until you
> enter the password or cancel.
> 
> When it has the secrets it needs to connect, it _then_ will start timers
> during the association.  There's an 8-second link timer, and an overall
> 20 second association timer.  The 8-second link timer only gets
> triggered if the driver sends a disconnection event after association
> has started, or when a successful association is established.  If the
> link isn't re-established after 8 seconds, NM will terminate the
> connection because the driver hasn't reassociated with the AP.  That
> time might be a little bit low, but it's pretty reasonable.  The 4-Way
> WPA handshake doesn't take that long, and if it does, you're most
> definitely so far near the margins of your network that you won't be
> able to pass frames anyway.
> 
> The 20 second overall association timer should probably get bumped up,
> and I've got a NetworkManager in the OLPC-2 collection queued up to
> build if required.  The problem here is that, due to driver issues, the
> spawned wpa_supplicant may not have had enough time to scan and find the
> AP you're looking for.  This is due mainly to driver issues, but is
> exacerbated by the fact that a new wpa_supplicant is spawned for each
> connection.  Later versions of NetworkManager use a long-running
> wpa_supplicant process so this isn't as much of a problem.
> 
> > I'm not sure how this seems to work OK on a regular Fedora system--which
> > is using almost the same version of
> 
> Because you're not using the libertas driver on the regular Fedora
> system, and because a regular system doesn't have the memory and speed
> constraints of the OLPC WRT to spawn time and memory pressure.  Things
> just run slower on the OLPC so timeouts like this must be adjusted
> upwards.
> 
> >   NetworkManager.  It's possible that the password-prompting happens
> > before we go into the timer-controlled
> >   region of the state machine--have we mucked with this at all?  Is the
> 
> Yes, the password prompting happens before either of the mentioned
> timeouts is started.
> 
> > password dialog one of our own, or
> >   just a standard one with Sugar decorations?
> 
> It's provided by Sugar, from sugar/hardware/*
> 
> Dan
> 
> 
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-- 
Jim Gettys
One Laptop Per Child