[OLPC Networking] Setting up the mesh device

[Dan Williams]

On Tue, 2008-06-24 at 18:09 -0400, Polychronis Ypodimatopoulos wrote:
> Sjoerd Simons wrote:
> > I'm setting the ESSID on the msh0 interface indeed. But i never get an
> > association event on it.. While i even get an association event on eth0 when
> > it's not up (but with msh0 being up obviously) :) Seems i've got some more bugs
> > to file
> >   
> 
> Why would you set an ESSID on the mshX interface in the first place? I 
> understand that, from a solid layering perspective, you should be able 
> to set essids on mshX since it's treated as a wireless interface, but it 
> would logically separate network users. It's hard enough as it is to 
> discover nodes in different channels (although different channels do 
> have a radio scaling advantage).

You need a way to tell the firmware that you'd like to apply the
configuration.  And once you tell the firmware that, the firmware
somehow needs to notify you that it's completed the requested
operations.  There is a small but noticeable amount of time between when
you send the request, and when the firmware has completed the channel
change and set up the state.  If you don't wait for the notification,
you'll assume you can send traffic when you actually cannot, and things
like mDNS announcements and such will be lost.

With WEXT, setting either the SSID or the BSSID are those triggers, and
the SIOCGIWAP event is the notification.  Unfortunately, because WEXT
doesn't have a direct link between requests and replies, we have to
enforce stricter semantics on behavior.

Dan