Fwd: Rapid DHCP

[Dan Williams]

On Wed, 2011-08-03 at 13:43 -0400, Nathaniel McCallum wrote:
> On Wed, Aug 3, 2011 at 1:38 PM, Bill McGonigle <bill at bfccomputing.com> wrote:
> > On 08/03/2011 01:19 PM, Dan Williams wrote:
> >> The Ubuntu NM maintainer has posted a WIP patch that makes NM say it's
> >> connected immediately if at least one of IPv4 or IPv6 completes.
> >> Currently if both are enabled, NM won't say it's connected until both
> >> are done (and result in either success or failure).  That at least
> >> speeds up the perceived connection speed, which isn't a bad thing.
> >
> > Nice, that will help almost everybody, but possibly it could break
> > somebody who's depending explicitly on IPv6 (or IPv4 in the other case)
> > for an app and now thinks the network is up.
> >
> > How do apps, e.g. Thunderbird, know when they're online?  dbus, /sys?
> >
> > If this change happens, there ought to be a way for that small slice of
> > apps to check to see that the stack they demand is really up, if they're
> > depending on it (more directly than parsing text output of userland
> > tools).  Probably this already exists, right?
> 
> It seems like NM's state transitions need to become more explicit.
> 1. IPv4 connected
> 2. IPv6 connected
> 3. "internet" connected (including proxy discovery)

I wrote a blog post about this:

http://blogs.gnome.org/dcbw/2011/06/14/networkmanager-and-dual-stack-addressing/

And we could do this.  But it's unlikely that app authors would actually
are about this en masse since it's more than just a single yes/no sort
of thing.  Next, you've got DNS lookups which can be either IPv4 or IPv6
depending on what the DNS server returns; if you do an IPv4 request and
the site's DNS server returns an AAAA record, what do you do with that
if you don't have IPv6 connectivity yet?  Basically it just gets more
complicated, and I'm not optimistic that app authors will really hook
into the additional information.  But it may still be worth trying.

Dan