SGI/Sun mountd errors (was Re: Power Series Iris as NFS file server?)

[Jack P. Weldon]

There is a problem with Sun's backoff algorithm in 4.1 mountd, and Sun has 
announced patches available for bugs #1035513 and #1035515 in Sun's database 
that fix the problem. The gory details follow from a previous posting to this
newsgroup:

From: dana at tread.wpd.sgi.com (Dana Treadwell)
Newsgroups: comp.sys.sgi
Subject: Bug in SunOS4.1 mountd
Organization: Silicon Graphics, Inc., Mountain View, CA


Please take heed if you are contemplating installing SunOS4.1. There
is a bug in Sun's 4.1 mountd which will prevent you from mounting an
SGI filesystem on a SunOS4.1 client. Here's the scoop:

Sun incremented the version number of mountd in 4.1 from 1 to 2. SGI
supports its own version so that showmount(1M) can report on the additional
export options provided by SGI. We chose version number 99 in order not to
collide with Sun's version numbers.

The problem is that Sun's back-off algorithm assumes a continous range of
version numbers, though such a restriction is not documented in the protocol
specification. If
    1) the server's highest version number is greater than the Sun
                client's highest version number and
    2) the Sun client's highest version number is not supported on the server,

the mount request will fail, even though the client and server might both
support a lower version number.


In the case with SGI, the Sun client sees that the SGI server supports #99
(which the Sun client doesn't), tries its highest version number which is #2
(which the SGI server doesn't currently support) and then the Sun client
gives up, failing to back-off and try version #1.

*********************************************************************
The result is that SunOS4.1 clients cannot NFS mount SGI filesystems.
*********************************************************************

We plan to fix this from our side in our next software release. This appears
as bugs #1035513 and #1035515 in Sun's database, if you want to talk to them
about it in the meantime.


Cheers, 

Jack P. Weldon (jweldon at sgi.com)     
SGI Product Support Engineering