a8e8d22c31
Found here at ESS:
(all in one line)
EPICS_CA_ADDR_LIST=averylonghostname.mylabnetwork.technicalnetwork.example.com
EPICS_CA_AUTO_ADDR_LIST=NO
caget somePVnam
leads to something like this:
CA.Client.Exception...............................................
Warning: "Empty PV search address list"
Source File: ../udpiiu.cpp line 403
Current Time: Thu Jun 09 2022 10:10:47.804161447
Problem desription:
addAddrToChannelAccessAddressList() will collect what ever we specify in
EPICS_CA_ADDR_LIST for channel access.
That function will add IP-addresses to the search list.
hostnames are possible, but are ignored if longer than 32 bytes,
because buf is too short.
If a hostname can be resolved into an IP, that is fine,
if not that is "fine as well" (better say: silently ignored):
If, and only if, EPICS_CA_AUTO_ADDR_LIST=NO is given then the one
and only too long hostname will be ignored and lead to an
"Empty PV search address list".
If EPICS_CA_AUTO_ADDR_LIST=YES (or nothing) is specified, the search list
is not empty, and EPICS will search all broadcast addresses.
This will eventually lead into a timout.
Solution:
Increase the buf size in addAddrToChannelAccessAddressList() from 32 to 256
The maximum length for a hostname is 255:
https://www.ietf.org/rfc/rfc1034.txt
If we add one byte for the string terminating '\0', we need 256 bytes.
And yes, this patch neglets the fact that a user can specify HOSTNAME:PORT,
which may need another 6 bytes. To put it the other way around:
In this case the hostname length is limited to 250 bytes,
which is still long enough in practice.
--------------------------------------------------------- EPICS Base - the central core of a control system toolkit --------------------------------------------------------- Copyright UChicago Argonne LLC, as Operator of Argonne National Laboratory. Copyright (c) 1991-2003 The Regents of the University of California, as Operator of Los Alamos National Laboratory. EPICS Base is distributed subject to a Software License Agreement found in the file LICENSE that is included with this distribution. --------------------------------------------------------- Installation and release information can be found in the various files in the documentation subdirectory. Additional information about EPICS including mailing list archives and subscription instructions, documentation and training materials, additional components, links to other websites etc. is available on the EPICS home page at https://epics.anl.gov/ $Format:%cD$ $Format:%H$ https://code.launchpad.net/epics-base