Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cmcl2!adm!xadmx!bzs@bu-cs.bu.edu
From: bzs@bu-cs.bu.edu (Barry Shein)
Newsgroups: comp.unix.wizards
Subject: Symbolic links and RFS
Message-ID: <19733@adm.BRL.MIL>
Date: 23 May 89 20:42:48 GMT
Sender: news@adm.BRL.MIL
Lines: 50


>? Accessing the inode fires up the program and waits for the resultant
>? string which specifies the rest of the path to use.
>
>Interesting, but this just repackages the problem. On which machine
>do you execute the program. It would seem to have to be the target
>machine, or else you'd need multiple versions of that program.

Nah, I'm cagier than that, the program could decide to do an rsh (or
moral equivalent.) It was no accident that my suggestion was Turing
complete (in a manner of speaking.) How would the program *know* which
machine it should execute on? Well, heck, whatever other solution you
might suggest is open to this one, at that point it's the typical
namespace games, somewhere there must be some info or else there is no
solution possible (eg. namei passes the program the entire path via
argv and the program decides if that's interesting.)

>Another solution would be to allow the pathname to contain a host
>as part of its name: foo -> bar:/path/name.

But I think there was more to this whole symlink thing than just
reaching over to another machine. The point is that this sort of thing
(choosing a host) is just one of zillions of things you could do once
you've decided to fire up a program to complete the path name (eg.
look in the person's environment, look at the rest of the path, look
in a data base which tells it where this guy's mumfle files are
stored, decide it's after 5PM so this is an unauthorized access anyhow
so kick him/her/it out and send mail to someone about the attempt etc
etc.)

My guess is that thinking in broader terms like this is more what's
troubling folks about symlinks, it's a significant facility that only
solves a few problems. The nagging feeling remains that a much broader
solution which encompasses symlinks as one possible use is possible.

The watchdog paper comes pretty close (I think it was the last SF
USENIX, last few USENIXI anyhow) but puts the process somewhere else
(which has its merits as a solution.) I was also under the impression
that some of the original Streams thinking (and file switch stuff) was
attacking a similar problem.)

>So Barry, what happened with Encore?

They're alive and well and still house many friends, I've done a
context switch.

	-Barry Shein

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