Re: suggestion for static ip

[Dan Williams <dcbw redhat com>]

On Mon, 2006-03-27 at 18:58 +0200, Kasper Peeters wrote:
> While I know that there has been a lot of debate about static IP
> support, could you please consider the following situation?
> 
> I have a laptop which I take between various wired network connections
> for which I have been given a static IP (all beyond my control, I
> would like to use DHCP or at least static DHCP but I cannot). Right
> now, I use "arping" to figure out where I am (by pinging a known host
> on the network and checking that the MAC address matches), and then
> setting the IP address appropriately.
> 
> If I come up with a way to add such static, wired network preferences
> to networkmanager, without disturbing the default "connect with DHCP"
> behaviour, would this be considered for inclusion?  Or am I barking up
> the wrong tree? Suggestions welcome.

We've thought about this before, and it would probably make a good
addition.  Given that we have to have some sort of UI (whether custom,
or a distro's current UI like s-c-n or yast) to configure static IP,
that's a good place to add options for a MAC address to arping.

Ideally we'd like to do the arping work ourselves without running the
actual arping executable, but that's up for debate since adding the code
to NM itself is an additional attack vector.  However, having arping
exec()-ed means tracking one or more child processes, which means more
state to keep track of and clean up.

One question though...  how would this work with, say, 20 static IP
configs?  We'd have to be intelligent enough here to fire off 3 or 4
arpings concurrently and then listen for responses, but not do all 20 at
once.  Need to strike a balance here between spamming the network and
speed at which we're able to connect.  Think of 30 machines running NM
all arpinging 20 hosts.

Also, this seems to be applicable only to wired networks, right?  Since
for a wireless network you already have to have some sort of
authentication information based on SSID or BSSID to even join it, you
might as well put in some static IP at the same time.

So in short, yes it's a good idea and I'd like to take a look at a patch
if you make one, but we need to be careful about how it's done.  What do
network admins think about arping?

Dan