Experimental Physics and
Industrial Control System

Ralph Lange <[email protected]> · Wed, 02 Apr 2014 10:28:21 +0200

On 31.03.2014 18:17, Andrew Johnson wrote:

This looks very interesting, probably worthy of a HowTo in the Wiki if
you can find time.

Note though that the /etc/network/if-{up,down}.d/ directories appear to
be Debian-specific; on RHEL and Fedora systems running NetworkManager
the equivalent script would go in /etc/NetworkManager/dispatcher.d/ and
gets given 2 arguments, the interface name ("eth0", "eth1" etc.)
followed by either "up" or "down".

Good idea.

I have created an EPICSWIKI page [1] that has updated scripts for Debian

and RHEL/Fedora (and their derivatives).

Cheers,
~Ralph

[1]

https://wiki-ext.aps.anl.gov/epics/index.php/How_to_Make_Channel_Access_Reach_Multiple_Soft_IOCs_on_a_Linux_Host

On 03/31/2014 10:15 AM, Ralph Lange wrote:

All,

As probably many of you know, running multiple IOCs on one host has an
annoying side effect: Clients that are using that host's IP address in
their EPICS_CA_ADDR_LIST with EPICS_CA_AUTO_ADDR_LIST=NO will only reach
one of the IOCs - usually the one that was started last. All clients
have to use broadcasts to reach all IOCs.
The same is true for CA Gateway machines that are set up in a way that
makes multiple Gateway processes serve channels into the same network.

Here's a little helper (for Linux hosts) that I recently was playing
around with - based on an idea by Rodrigo Bongers (CNPEM, Brazil).

If you drop the attached script into /etc/network/if-up.d *and*
/etc/network/if-down.d, it will automatically create/delete an iptables
rule that replaces the destination address of all incoming CA UDP
traffic on each interface with the broadcast address of that interface.
Simple and effective: the kernel will see all incoming name resolution
requests as broadcasts, and delivers them to all IOCs instead of one.

Note: This will not work for clients on the same host. (Adding that
feature makes things a lot more complicated, and I like things to be
simple.)
If you need connections between IOCs on one host, I would suggest adding
the broadcast address of the loopback interface (usually
127.255.255.255) to each IOC's EPICS_CA_ADDR_LIST setting.

Enjoy!
~Ralph

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System