Re: Strange CAS error

[Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>]

I think this happened when he installed a new EPICS IOC at an APS beamline.  Perhaps it is a port scanner on the CA ports, rather than a real CA client?


Mark



________________________________
From: Johnson, Andrew N. <anj at anl.gov>
Sent: Thursday, January 21, 2021 11:16 PM
To: Mark Rivers
Cc: tech-talk at aps.anl.gov
Subject: Re: Strange CAS error

Hi Mark,

This is from the release notes for 3.16.1, from about 5 years ago:
Channel Access "modernization"

Drop support for CA clients advertising protocol versions less than 4.

This effects clients from Base older than 3.12.0-beta1. Newer clients will continue to be able to connect to older servers. Older clients will be ignored by newer servers.

This allows removal of UDP echo and similar protocol features which are not compatible with secure protocol design practice.

Another possibility is that some other non-EPICS device may be opening a TCP socket and sending data to the IOC server that it thinks might be the start of a legitimate connection.

If your colleague has a client built against a CA client library that predates 3.12.0-beta1 which can’t be recompiled, it should be possible to put a CA gateway between it and the newer IOC to do the appropriate protocol translation.

- Andrew

--
Complicity is easy, Simplexity takes real work

On Jan 21, 2021, at 6:37 PM, Mark Rivers via Tech-talk <tech-talk at aps.anl.gov> wrote:

A colleague is running an IOC on which he is seeing these messages:


CAS: request from 146.137.70.29:47932<http://146.137.70.29:47932/> => CAS: Client version too old
CAS: Request from 146.137.70.29:47932<http://146.137.70.29:47932/> => cmmd=18245 cid=0x54502f31 type=12064 count=18516 postsize=21536
CAS: Request from 146.137.70.29:47932<http://146.137.70.29:47932/> =>   available=0x2e310d0a         N=0 paddr=0000000000000000


I have never seen those before.  What cause cause a "Client version too old" error?


Thanks,

Mark