Xref: utzoo comp.unix.ultrix:987 comp.sys.dec:1316
Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cbmvax!grr
From: grr@cbmvax.UUCP (George Robbins)
Newsgroups: comp.unix.ultrix,comp.sys.dec
Subject: Re: chained packet panic on DEQNA (uvaxII) ?
Message-ID: <7004@cbmvax.UUCP>
Date: 28 May 89 19:24:39 GMT
References: <8147@boring.cwi.nl> <2717@helios.ee.lbl.gov> <2734@helios.ee.lbl.gov>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 41

In article <2734@helios.ee.lbl.gov> envbvs@epb2.lbl.gov (Brian V. Smith) writes:
> In article <8147@boring.cwi.nl>, jack@cwi.nl (Jack Jansen) writes:
> > In article <2717@helios.ee.lbl.gov> envbvs@epb2.lbl.gov (Brian V. Smith) writes:
> > >We are crashing on our Microvax II with a DEQNA with the panic message
> > >"qe: chained packet".
> 
> > Anyway, the problem is probably that there are packets coming in
> > that are longer than one receive buffer (and, thus, get chained into
> > the next buffer) and your software can't handle this. Depending on
> > your OS, you might be able to extend the size of the recieve buffers.

> I suspect that some other host is sending large packets that is making
> our machine panic.  Do you know how to extend the size of the receive 
> buffers on Ultrix 2.x or Ultrix 3.0 (which we will be installing anyway)?

This is not so easy.  The DEQNA seems to be an attempt by DEC to emulate
a DELNI using a Fujitsu ethernet controller chip instead of a LANCE.  It
has a grand total of 8K onboard memory, which doesn't allow from very
many normal packets, let alone mega packets.
 
It's fairly easy to patch the driver to ignore the error condition instead
of panic'ing, however, I suspect the result would be to hang the interface
if you simply noop'ed out the panic().  Making it do the "right" thing or
even toss the "bad" packet(s) would be non-trivial.

> > Another (hacky) solution is to set the 'mtu' of all systems on
> > the net to a value lower than your uVax-II buffer size.
> 
> You're not serious!  There are several hundered machines on the LBL net.

In which case hoepfully you have a competent network administrator/wizard?
If so take the problem to him.  It's probably only one or two bad guys
and might be correctable.  You might want to take the problem up with DEC
software support.  While you'll get little sympathy for the oversize
packets, you should be able to make a very reasonable case that typical
network problems should *never* cause a panic.

-- 
George Robbins - now working for,	uucp: {uunet|pyramid|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@uunet.uu.net
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)