Re: network discovery interval in network manager?

[Dan Williams <dcbw redhat com>]

On Tue, 2010-06-01 at 19:11 +0200, pink wrote:
> Hi,
> 
> does anybody know the interval of the network search that is internally 
> used by
> the network manager and where it is implemented. So far i know there is
> no dbus interface where such an interval can be changed.

It currently starts at 0 seconds from when the device is found, and
increases by 20 seconds every scan until 2 minutes, after which scans
are done every 2 minutes.

> Is there an other possibility to change these value or
> is it planned to make such parameter available for the user?

It's something we're investigating, but likely it'll take the form of an
additional D-Bus method which clients can use to request a scan.  This
D-Bus method may rate-limit scan requests or otherwise require
privileges to call since scan requests are effectively a DoS against the
wifi card.  Recent improvements to the kernels' mac80211 stack have
mitigated that effect (with background scanning) but drivers that do not
use mac80211 don't get that and thus may interrupt traffic during the
scan.  So you can guess what happens if something in userspace
continually requested scans...

But yeah, I'd take a patch for something like that.  I know Ubuntu is
carrying on in their Netbook remixes which isn't acceptable as-is, but
could be cleaned up.  Ground rules are:

1) a method called RequestScan(aay: ssids) on the wifi device object
2) if a scan is in progress, the method simply returns success
3) resets the scan interval to 20 seconds after the requested scan is
done
4) is PolicyKit protected, which is easy to do using some of the
infrastructure I'm working on in the 'perm' branch upstream right now

Dan