Experimental Physics and
Industrial Control System

Michael Davidsaver via Core-talk <core-talk at aps.anl.gov> · Wed, 16 Nov 2022 20:38:15 -0800

On 11/16/22 16:30, Bellister, ,Jesse wrote:

Hi all,

One further update. The specific commit which fixed the issue was this one here:

https://github.com/epics-base/epicsCoreJava/pull/93 <https://github.com/epics-base/epicsCoreJava/pull/93>

This was confirmed by undoing that one change while leaving everything else the same, which resulted in seeing the incorrect multicast traffic again.

Based on the date of the change, it appears that versions of epicsCoreJava prior to 7.0.7 would exhibit the behavior we were seeing, and anything from that commit onward should be fine (including 7.0.7 and 7.0.8).

I suspect there were other variables at play.
Perhaps the formerly ubiquitous preferIPv4Stack
property effected the default ProtocolFamily?

-Djava.net.preferIPv4Stack=true

Also, did you be chance see this message being logged?

Failed to initialize local multicast, funcionality disabled

https://github.com/epics-base/epicsCoreJava/issues/129

Thanks!
Jesse

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*From:* Core-talk <core-talk-bounces at aps.anl.gov> on behalf of Bellister, ,Jesse via Core-talk <core-talk at aps.anl.gov>
*Sent:* Wednesday, November 16, 2022 12:23 AM
*To:* Williams Jr., Ernest L. <ernesto at slac.stanford.edu>; Michael Davidsaver <mdavidsaver at gmail.com>
*Cc:* EPICS core-talk <core-talk at aps.anl.gov>; Zelazny, Michael Stanley <zelazny at slac.stanford.edu>
*Subject:* Re: Question PVA environment variable
We were using the 7.0.2 build of epicsCoreJava, which included version 5.1.2 of the epics-pvaccess jar.

This version was causing pv name query re-transmits to go out on the physical network interface, instead of just being confined to the local loopback as expected. This resulted in flooding the network with multicast traffic for erroneous name queries. Multicast traffic is expected as per the pvAccess specification

When a client or server receives a packet containing a Search message with flagged "sent as unicast" it may resend this as a multicast to "224.0.0.128"
through the loopback interface ("127.0.0.1").

But it should always be confined to the loopback.

After updating to 7.0.8 which includes version 5.1.7 of the epics-pvaccess  jar, the issue appears to be resolved. What specifically changed to resolve the issue between the versions is still being investigated.

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*From:* Williams Jr., Ernest L. <ernesto at slac.stanford.edu>
*Sent:* Wednesday, November 16, 2022 12:14 AM
*To:* Michael Davidsaver <mdavidsaver at gmail.com>
*Cc:* Kim, Kukhee <khkim at slac.stanford.edu>; Zelazny, Michael Stanley <zelazny at slac.stanford.edu>; EPICS core-talk <core-talk at aps.anl.gov>; Bellister, ,Jesse <jesseb at slac.stanford.edu>; Williams Jr., Ernest L. <ernesto at slac.stanford.edu>
*Subject:* Re: Question PVA environment variable
This issue is only happening with epicsCoreJava package we were using

Jesse, please copy in the details here
Jesse is also in contact with Kunal and Kay

Sent from my iPhone

On Nov 15, 2022, at 11:11, Michael Davidsaver <mdavidsaver at gmail.com> wrote:

I realize I forgot to CC the core-talk list.

On 11/9/22 06:51, Michael Davidsaver wrote:

On 11/8/22 22:37, Kim, Kukhee wrote:
Hi  Michael,

Thank you so much for your advice.
The multicast address is:  224.0.0.128

Ah, right...  This address is used by PVA instead of something like caRepeater.
It should only be sent via the loopback interface through.
You can run "ip maddr" to see that 224.0.0.128 appears for the "lo" interface,
but not for any others.

$ ip maddr
1:      lo
         inet  224.0.0.128 users 2
         inet  224.0.0.1
         inet6 ff02::1
         inet6 ff01::1

...
Are you seeing packets with this destination address actually going out on a wire?

We have PVA address setup as the followings:

EPICS_PVA_ADDR_LIST='<broadcast addr for subnet>  255.255.255.255'
EPICS_PVA_AUTO_ADDR_LIST=NO
EPICS_PVA_BROADCAST_PORT=5076
EPICS_PVA_SERVER_PORT=507

Hi Ernest and Mike,

Can we capture the packet which goes to the multicast address to recognize searching or beacon?

Thank you for your help.  I will update you.

Thank you.
Best regards,
Kukhee

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*From:* Michael Davidsaver <mdavidsaver at gmail.com>
*Sent:* Tuesday, November 8, 2022 9:14 PM
*To:* Kim, Kukhee <khkim at slac.stanford.edu>
*Cc:* Zelazny, Michael Stanley <zelazny at slac.stanford.edu>; core-talk at aps.anl.gov <core-talk at aps.anl.gov>
*Subject:* Re: Question PVA environment variable
On 11/8/22 13:00, Kim, Kukhee via Core-talk wrote:

Hi Everyone,

We just realized that some of our servers send out packets to port 5076 in multicasting address.

What multicast address(es) are you seeing?

Can you look (with packet capture) to see if these are
search or beacon messages?

Since, the multicasting address is used for some of specific services, we would like to prevent the PVA, PVXS traffic to the multicasting address.

PVXS should not send any multicast traffic by default.
(we have no assigned addresses to use for PVA)

Is there any PVA environment variables to control it?

https://mdavidsaver.github.io/pvxs/netconfig.html <https://mdavidsaver.github.io/pvxs/netconfig.html> <https://mdavidsaver.github.io/pvxs/netconfig.html <https://mdavidsaver.github.io/pvxs/netconfig.html>>

There are a couple, all of the form EPICS_PVA*_ADDR_LIST

Thank you so much for your help and support!

Best regards,
Kukhee

Kukhee Kim | *Engineering Physicist *

Advanced Controls Department

SLAC National Accelerator Laboratory | Menlo Park, CA

p: 650.926.4912 | m: 669.300.8192 | email: khkim at slac.stanford.edu

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System