Hi,
I am using net-snmp 5.4 and in agentX framework with 1 Master and 5
subagents. Subagents report there capabilities periodically(every 5
seconds) using AgentX AddAgentCaps PDU.
I have an automated test suite which runs for 5 hours and have tests
consisting of various snmpwalks/snmpgets on various mibs Sometimes
when i run this suite i observe that some of the subagents gets stuck.
The problem is quite random and doesn't consistently or for a given
subagent only. Sometimes i have to run this suite multiple times to
reproduce this behavior
Following is the backtrace of a stuck subagent.
#0 0x0fac1b40 in ___newselect_nocancel () from /lib/libc.so.6
#1 0x0ff666d8 in snmp_synch_response_cb () from /usr/lib/libnetsnmp.so.15
#2 0x0fe90a20 in agentx_synch_response () from /usr/lib/libnetsnmpagent.so.15
#3 0x0fe90c60 in agentx_add_agentcaps () from /usr/lib/libnetsnmpagent.so.15
#4 0x0fe8dd10 in agentx_sysOR_callback () from /usr/lib/libnetsnmpagent.so.15
The back trace suggests that the subagents are waiting for the
response of AGENTX_MSG_ADD_AGENT_CAPS request. Now ideally even if the
master agent doesn't sends back the response, subagent should timeout
using the values of agentXTimeout, agentXRetries which i have defined
in my snmpd.conf as 5 and 1 respectively on subagents but its not
happening and subagents are stuck forever.
I was looking at the code of snmp_synch_response_cb() which the
function being called eventually from agentx_add_agentcaps () and i
can see that the function has changed in netsnmp 5.4.3.pre1.
There has been an additional check introduced snmp_synch_response_cb()
function towards the end -
if ( ss->flags & SNMP_FLAGS_RESP_CALLBACK ) {
void (*cb)(void);
cb = ss->myvoid;
cb(); /* Used to invoke
'netsnmp_check_outstanding_agent_requests();'
on internal AgentX queries. */
}
Can anyone please explain the reason for this additional code and
could this be related to the issue that i am facing?
Thanks,
Manu
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