Experimental Physics and
Industrial Control System

Claude Saunders <[email protected]> · Tue, 17 May 2011 09:02:08 -0500

Hi Bruce,

From your first sentence, I see "IOC's" (plural) and "linux". I

recently had what I believe is the same problem, which Andrew Johnson

kindly helped me understand. If you are running two iocs on one linux

host, using default ports, you wind up with two processes listening on

the same udp port. I gather with linux, the network stack will only

deliver an incoming (pv search) broadcast UDP packet to one of those

processes. If it happens to be the one without the PV you're looking

for, then the ca_search fails, even though the other IOC process

contains the PV.

   - Claude

On 05/17/2011 12:12 AM, Bruce Hill wrote:

I've been having trouble with one linux machine where my IOC's appear
to be running correctly, dbgf works from iocsh, but caget from another

window on the same machine fails to connect. I suspect it has

something

to do with how the multiple interfaces on this machine are configured,

but

so far have been unable to find a solution.

# ifconfig

eth0 Link encap:Ethernet HWaddr 00:1E:68:79:5C:4E inet

addr:134.79.32.161 Bcast:134.79.35.255 Mask:255.255.252.0

         inet6 addr: fe80::21e:68ff:fe79:5c4e/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:190759 errors:0 dropped:0 overruns:0 frame:0
         TX packets:43567 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:18427912 (17.5 MiB)  TX bytes:9772031 (9.3 MiB)
         Interrupt:19

eth2 Link encap:Ethernet HWaddr 00:1E:68:79:5C:50 inet

addr:192.168.254.2 Bcast:192.168.254.255 Mask:255.255.255.0

         inet6 addr: fe80::21e:68ff:fe79:5c50/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:1238443 errors:0 dropped:0 overruns:0 frame:0
         TX packets:879202 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:80539799 (76.8 MiB)  TX bytes:64420869 (61.4 MiB)
         Interrupt:20 Base address:0x4000

Gateway is 134.79.35.1

I'm running with defaults for the EPICS_CA* and EPICS_CAS* env variables,
but have also played with EPICS_CA_ADDR_LIST, EPICS_CA_AUTO_ADDR_LIST,
and EPICS_CA_INTF_ADDR_LIST with no success.

See attached files for casr, epicsEnvShow, ifconfig, and netstat output

for more configuration details. We're running base 3.14.9

everywhere, but this

is the only machine showing this problem.

The casr output includes:
UDP Server:
UDP 0.0.0.0:0(): User="", V4.0, 0 Channels, Priority=0

This looks wrong to me, as my working IOC's show a valid UDP addr, but

I'm

not sure how to fix this, or even if this is the root problem.

Any suggestions would be appreciated.
Thanks,
- Bruce

P.S.  When I run caget, tcpdump shows:
# /usr/sbin/tcpdump -i eth0  -n -nn udp dst portrange 5064-5065

tcpdump: verbose output suppressed, use -v or -vv for full protocol

decode

listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

21:46:55.934345 IP 192.168.254.2.54260 > 134.79.35.255.5065: UDP,

length 16

21:46:57.179960 IP 134.79.32.161.43268 > 134.79.35.255.5064: UDP,

length 48

21:46:57.211939 IP 134.79.32.161.43268 > 134.79.35.255.5064: UDP,

length 48

21:46:57.275932 IP 134.79.32.161.43268 > 134.79.35.255.5064: UDP,

length 48

21:46:57.403935 IP 134.79.32.161.43268 > 134.79.35.255.5064: UDP,

length 48

--
----------------------------------------------------------
 Claude Saunders<[email protected]>
 Software Services Group Leader
 Advanced Photon Source,   Argonne National Laboratory
 Argonne, IL  60439                   630 - 252 - 6619
----------------------------------------------------------
    We write suggestions, suggesting fading to silence
    And that must please you
    My mirror's tarnished with 'no help'
                      - Gary Numan
----------------------------------------------------------

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System