[Simh] OpenVMS 7.2 VAX telnet failure

Wed Apr 30 20:58:17 EDT 2014

You can do BOTH (rule out the variables you have planned), and AT THE SAME TIME, collect traffic with WireShark.  You can start Wireshark Data collection any time BEFORE (and through) when you start to see the problem.  So, even if you’ve already setup the next step in your plans, you can still turn on WireShark to collect the relevant data…

From: simh-bounces at trailing-edge.com [mailto:simh-bounces at trailing-edge.com] On Behalf Of Lorenzo
Sent: Wednesday, April 30, 2014 2:52 PM
To: Mark Pizzolato - Info Comm
Cc: simh at trailing-edge.com; Rick Murphy
Subject: Re: [Simh] OpenVMS 7.2 VAX telnet failure

As I stated in comp.os.vms too, I came up with this testbed:

 * OpenVMS 7.2, attached to a newer Realtek network card
 * OpenVMS 7.3, fresh setup temporarily running on the integrated network card

Albeit seeming messy, this should allow me to rule out a few more variables in ~24 hours.
In case of failure I'm ready to dump traffic with Wireshark and post it here.

Thanks

2014-04-30 17:45 GMT+02:00 Mark Pizzolato - Info Comm <Mark at infocomm.com<mailto:Mark at infocomm.com>>:
Of course, you are free to try to work around the issue, but traffic captures will explain what is really happening and then determine what the simplest workaround might be.  Traffic analysis will either point to or eliminate the need or desire to swap cards.

I’d suggest that you try using the MultiNet IP stack.  I’ve had experience with MultiNet  for 20+ years and even now, leave telnet sessions connected for many days and never see a problem.  Switching to MultiNet will avoid the need to migrate users or configure a new OS from scratch or perform an upgrade.  I strongly suspect that both MultiNet and the HP TCP stack can be installed on the same system at the same time as long as you only start one OR the other in your systartup configuration.

From: simh-bounces at trailing-edge.com<mailto:simh-bounces at trailing-edge.com> [mailto:simh-bounces at trailing-edge.com<mailto:simh-bounces at trailing-edge.com>] On Behalf Of Lorenzo
Sent: Wednesday, April 30, 2014 8:30 AM
To: Mark Pizzolato - Info Comm
Cc: simh at trailing-edge.com<mailto:simh at trailing-edge.com>; Rick Murphy

Subject: Re: [Simh] OpenVMS 7.2 VAX telnet failure

Before starting to dig into traffic captures I'd like to try two more things:

* a OpenVMS 7.3 setup on a new SIMH machine - if that works then I can think about migrating users and data from 7.2
* using a different ethernet card to rule out layer 1 problems

This problem is not easily reproducible, "it just happens", so I can only report back after a certain amount of time.
Thanks for now

2014-04-30 16:59 GMT+02:00 Mark Pizzolato - Info Comm <Mark at infocomm.com<mailto:Mark at infocomm.com>>:
As Rick suggested, you should capture traffic in both directions.  Wireshark is an excellent tool for that.  Additionally, Wireshark has built-in protocol decoders which can interpret what is happening in the TCP telnet session.  If you aren’t familiar with, or don’t want to dig into the details of the packet innards, you can save the capture contents, make it available, and let me or someone else can interpret the details and offer analysis.

From: simh-bounces at trailing-edge.com<mailto:simh-bounces at trailing-edge.com> [mailto:simh-bounces at trailing-edge.com<mailto:simh-bounces at trailing-edge.com>] On Behalf Of Lorenzo
Sent: Wednesday, April 30, 2014 7:25 AM
To: Rick Murphy
Cc: simh at trailing-edge.com<mailto:simh at trailing-edge.com>
Subject: Re: [Simh] OpenVMS 7.2 VAX telnet failure

What nmap is reporting should be the traffic from the VAX to the client.
No matter the client I use (e.g. telnet.exe, PuTTY...), all I get is an endless stream of chars, which matches what appears in the traffic dump.
Upgrading to SIMH 4.0 beta had no effect - after 14 hours I experienced the same exact problem.
During the telnet outage, which happened after ~14 hours of SIMH running, FTP was still working fine.

2014-04-30 2:50 GMT+02:00 Rick Murphy <rick at rickmurphy.net<mailto:rick at rickmurphy.net>>:
At 06:21 PM 4/29/2014, Lorenzo wrote:
Hi!
I'm running OpenVMS 7.2 VAX on a simh emulator, latest release
(V3.9-0 from <http://simh.trailing-edge.com>simh.trailing-edge.com<http://simh.trailing-edge.com>) and compiled with networking (libpcap, no vde).

The emulator has got its own network card to which it's attached.
The host operating system is Linux, kernel 3.11.
My issue is that after an apparently random amount of time (usually a few hours) the telnet server stops working.
I can't get any client to log in remotely - as soon as I connect to the OpenVMS machine,
all I get is a blank character sequence, as follows (dumped by nmap):

SF:NULL,1138,"\xff\xfb\x01\xff\xfb\x03\xff\xff\xff\xff\0\0\0\0\0\0\0\0\0\0

There's a beginning of some TELNET options negotiation going on there.

That's the following:
255 (IAC)
251 (WILL)
1   (ECHO)
255 (IAC)
251 (WILL)
3   (SGA) [Suppress go-ahead)

That's pretty standard.
The series of 0xff (IACs) and nulls that follow aren't.

You really need to capture the traffic to-and-from. Is this coming from the VAX to your client, or vice versa?
        -Rick

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