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Re: New ip-up (Was: Re: REQ ip-up: run-parts /etc/ppp/up )

Dear Manog Dibos,

I would like to know what else doesn't work besides the `talk' program?

I would venture a guess that what else doesn't work is the BSD rlogin,
rsh, rexec, etc. programs.  I would also guess that when these programs
were designed, there was no such thing as dynamic ip addresses.

IMO, `localhost' makes more sense than the name my isp has assigned to
the ppp interface that I am using.  In addition, there are these
problems that I can see.

1) If your X-server is using authentication (true for xdm, and those
that specify the `-auth' option in .xserverrc with xinit), when the
hostname is changed, if you try to launch any X client it will fail, due
to authentication.  If, and this is a big if, especially if you have
multiple .Xauthority files in use, you can locate the .Xauthority files,
then you can create valid authorization records for the dynamic hostname
from the original localhost record.

2) If you are compiling a kernel, it will be identified by whatever your
hostname of the moment is.  Perhaps, some would consider this to be a
valuable feature, rather than a problem.  Emacs currently uses the
hostname in its default name and icon name resources too.

Date: Tue, 21 Oct 1997 14:23:23 +0000 (   )
From: Manong Dibos <jwalther@citytel.net>
> Thanks Erv.  Good explanation.  One problem I see is, not a lot of ppp
> users have a static IP.  Our IP (and thus, hostname) is different every
> time we connect.
> Is there an easy way to check if the current hostname resolves to the IP
> of the first ppp interface that came up?

The first ppp interface to come up is ppp0.

> I think the correct behavior is to only modify the hostname when the first
> ppp interface comes up, and when the last ppp interface comes down.
> Anyone have any different thoughs?  Hints on implementation?

The first interface to come up may be the first to go down.  If the
interface that you use to contact a remote talkd is different from the
one associated with your hostname, then talk still doesn't work.

> I mean, how does one detect the presence of multiple ppp interfaces?
> Should be some simple way to abort ip-up and ip-down...

You could probably get this info from ifconfig or route commands.  I
don't understand what you mean by `abort' here?

> Also, can't a box have multiple FQND's ?  Perhaps an awk solution is
> needed so they all work?  But then what is the relationship of `hostname`
> to /etc/hosts ?

No.  A host can have multiple interfaces, this is called multi-homed,
but they must all give the same FQDN when reverse looked up.  Try the
host or nslookup commands to play with this, using gateway.tuc.noao.edu
[] e.g.

Take a look at hostname(1) and gethostbyname(3).  Also, the Network
Admin. Guide by Olaf Kirsch, Chapter 6, mentions this a bit.

Manog, I am far from an expert on these matters.  I was hoping that
there would be someone on debian-devel who is an expert that could help
clear this up for us.

Jeff Sheinberg  <jeffsh@erols.com>

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