system-config-network & Zeroconf

[Dan Williams]

On Sat, 2008-03-08 at 00:36 -0600, Callum Lerwick wrote: 
> On Wed, 2008-03-05 at 18:06 -0500, Dan Williams wrote:
> > The problem is that some people want DHCP on their WLAN adhoc
> > networks... I still need to figure out how the Apple connection sharing
> > works; they use IPv4 LL addresses in the created Ad-Hoc network but I
> > don't know how other machines get the default route to the one sharing
> > its connection.  Possibly the router announces itself with Avahi or
> > something.
> 
> The connection sharing box provides DHCP.

You are correct, I've verified this on 10.3 & 10.4.  The Airport card
comes up in infrastructure mode, the bootpd process is running, and the
Airport card is assigned an address in the 10.x.x.x space.  I'm not
entirely sure why I thought they did Ad-Hoc in the past, but it might
have been that the iBook I was using to connect to the G4 that was
sharing the connection failed to connect (wrong WEP key perhaps) and
just got an autoip address instead.

In any case, this is good for Linux as a client of Apple's ICS, because
it just works.

But it's bad for Linux as the software base station itself, because so
many of the current drivers just suck really really hard for
infrastructure mode.  Beyond the hostap Prism 2/2.5/3 driver, I can't
think of a single driver that does master mode well at all, and even the
mac80211-based drivers, while they are quite capable of being APs, are
somewhat tied to the specific version of the hostapd since the interface
there is still evolving.

So for the time being, NetworkManager 0.7 will:

1) as the _originator_ of a wireless network, either by sharing a
connection or creating a new wireless network, use 802.11 Ad-Hoc and
provide a DHCP server (probably using dnsmasq)

2) require opt-in to get IPv4 LL on device types known to usually use
DHCP, requiring the user to pick between Auto-IP and DHCP (ie, Auto-IP
and DHCP will be mutually exclusive)

3) Perform DHCP by default on Ad-Hoc networks, unless the user has opted
into Auto-IP in the connection editor

Dan

> > There does need to be more thought here; but I'm leaning towards
> > defaulting connections created when the user explicitly shares an
> > existing connection (ie, you pick "Share this mobile broadband card over
> > wireless") to zeroconf.  In the end there will still be booleans in the
> > config to mark DHCP yes/no and zeroconf yes/no.  I'm wondering if the
> > zeroconf option should be mutually exclusive with any of the others; ie
> > would you ever want to have a secondary IPv4 LL address at the same time
> > as you have a non-LL address.
> 
> Has ANYONE here actually read rfc3927? Link local means just that, link
> local. Read the second paragraph of the abstract, and section 2.7 and
> 2.8, titled "Link-Local Packets Are Not Forwarded" and "Link-Local
> Packets are Local".
> 
> Therefore, any device providing routing of any kind, MUST use something
> else, namely DHCP.
> 
> This shit should Just Work, the only UI there should be is a checkbox to
> disable "auto configuration" and set fixed settings.
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