Re: force nm to use a connection

[Alexander Sack <asac ubuntu com>]

On Wed, Mar 11, 2009 at 06:40:31AM -0400, Dan Williams wrote:
> On Wed, 2009-03-11 at 11:34 +0100, Alexander Sack wrote:
> > On Wed, Mar 11, 2009 at 12:10:40AM +0100, Jérôme PRIOR wrote:
> > > hello,
> > > 
> > > I'm looking for info to force nm to use a connection instead of "Auto
> > > eth0". I explain :
> > > 
> > >   at home I need a static IP, with special DNS, ... So, I created a
> > >   connection called `home` with those parameters. Works fine when I
> > >   activated it manually.
> > > 
> > >   When I'm outside, I need `auto eth0`.
> > > 
> > > How can I tell nm "when I'm at home, connect me via `home`, even if
> > > connect me via `auto eth0` ?
> > > 
> > > I try to pla with "automatic connection" but of course, if I put `home`
> > > as auto, and `auto eth0` as no-auto, when I'm outside, `home` is up.
> > > And inversement.
> > > 
> > 
> > NetworkManager currently has no "smart" tie-break logic to decide
> > which auto connection to use. Not sure, but maybe it prefers the last
> > one that was active.
> 
> Yes, it uses the last connected Ethernet connection.  For wifi, it uses
> the last connected AP that's currently visible.
> 
> > Not sure if we could come up with something smarter for wired. Any ideas?
> 
> Not for plain wired, unless you want to try ARP sniffing or ARP-ing a
> known IP address to match a known MAC address or something.  Not that
> that is in any way secure, and it would also increase connection
> latency.  But maybe that's a worthwhile tradeoff to get the right wired
> connection; most people will only have one or two, so a few seconds to
> sniff which connection to use (if its been configured that way) might be
> worth it.
> 

I think it would be worth it and would be in line with NM's idea of
being as smart as possible :). I am not sure about the security
implications, but how does current autoconnect strategy not come with
the same risks?

Also related, how about probing for pppoe concentrators to add more
automagic on that front?

 - Alexander