Re: [patch] Support Debian's resolvconf

On Sun, 2005-07-31 at 15:15 +0200, Olivier Blin wrote:

> Ok, but you could have enhanced the current system to have this kind
> of status reporting. Currently, I guess you have lost the ability to
> manage ppp connections, dsl connections and isdn connections in
> NetworkManager.

I think a big component of the design thought behind NetworkManager is
to make the "common" case work really, really well, even if that comes
at the expense of some of the less-common cases.  

For example, making 802.11 work really well, and not including ppp and
idsn.  I know ppp/isdn are probably very important to some people, but
in good design you have to make some trade-offs.  I don't think it's
impossible to "support" these things in NetworkManager, be that some
basic integration with and awareness of existing distro tools for these
connection types, or implementing it all in NetworkManager if that
proves necessary.

> Right, the network scripts can't handle that currently, but it's quite
> easy to add this feature. In Mandriva, I plan to use wpa_supplicant as
> default roaming daemon for wireless interfaces. So the wireless
> settings would be configured in wpa_supplicant.conf. Then, the network
> level parameters (IP settings, DHCP) could be configured in
> per-wireless-network configuration files. We could use files named by
> the ESSID or BSSID to store this settings, in for example
> /etc/sysconfig/network-scripts/wireless

So there's a lot of implementation details here; what are you getting
over NetworkManager (as it stands today)?  As far as I can see, you get:

o Support for static IP addresses on 802.11b etc
o Backwards compatibility 

Now the first item, I guess my thought would be - there's probably about
50 networking nerds out there who have hardcoded static IP addresses for
their wireless networks; are they really important?  It's really weird
to use static IP for wifi in general anyways since you have to also do
things like hardcode the MAC address of the access point etc, or you
don't support roaming basically.  Maybe in specialized situations the
static IP makes sense, but we should sit down and talk about what those
situations are and think about the problem rather than just deciding
that since it was supported before, it has to be in the future.

The second item has some importance I understand - but we could discuss
how to get some basic integration of NM and the existing ppp/isdn
configuration; this might be basically just sending NetworkManager a
dbus signal from the isdn script to say "i'm on isdn, don't do
wired/wireless".  Maybe it's harder than that, I don't know, but again
we should discuss it.

> To have a dynamic behaviour, the network scripts only miss ifplugd and
> wpa_supplicant support. We already have both in Mandriva, we just have
> to allow to use the two daemons for the same interface.

No offense but this feels pretty handwavy to me :)  Sure, you have
ifplugd and wpa_supplicant and some network scripts...but do they all
really form a coherent whole when you put them all together?  For
example if you are on wireless through wpa_supplicant and then plug into
a static IP network, does ifplugd activate the static IP address in
addition to the wireless?  Who owns the routing table?  What if both
want to do DHCP, and write out resolv.conf?  How does VPN interact with
both of these?  How does the user control and configure the VPN?

A lot of thought has gone into these issues in NetworkManager, and I
think they've been solved pretty well.

> To me, current network scripts are a good starting point, and I don't
> find it really difficult to make them mobility-aware.

I would like to convince you otherwise - we really want to see
NetworkManager become the core of Linux networking, because this is an
area that is hugely fragmented and having the NetworkManager API always
available means applications can adjust their programs to dynamically
respond to network availability via the dbus signals.

> Fair enough.
> So, you're currently using network scripts for corporate servers and
> NetworkManager for desktop. Do you have some migration scripts to
> handle the transition in the future?

The answer is that right now there is basic backwards compatibility with
ethernet static addressing in the form of simply doing nothing if an
interface already has an IP address (presumably configured via distro
scripts).  There isn't compatibility with existing ppp/isdn, but that
may not be too hard to do as I said above.

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