Windows Net-SNMP Handle leak ( more information )

All,

As you know we have found what appears to be a handle leak with pass_persist extensions.  We are able to see this leak in action on every windows system we have instrumented with net-snmp.  Microsoft has repeatedly verified the leak within the snmpd.exe process (two separate engineering teams within the company found it at roughly the same time).  We have tried both net-snmp 5.4.1.2 and 5.4.2.1 with the same results.

It appears that Net-SNMP isn't handling the unexpected shutdown of any pass_persist extension properly. It's re-starting the extension in question but any handles that were in use by that extension originally never get freed up.

We have verified that the handle count does not increase but remains the same if the extension stays running.  This is quite easy to replicate.

steps to replicate:

1. configure snmpd.conf to run a bad pass_persist extension (anything that doesn't stay running ) - Could be a batch file for sake of the test, it doesn't even have to respond to a PING / PONG conversation properly.

2. add the appropriate line to the snmpd.conf

3. poll the oid that exercises your bad agent extension.

4. Open up perfmon -> select Add Counters , under the performance object select Process and then select Handle Count.  Under the instances select snmpd.exe

5. Watch the handle count climb with every poll.


Let me know if there's anything further testing that I can do to further assist in troubleshooting this.

Jayson Robinson
DSS Instrumentation - Performance and Hardware Monitoring Engineering
Global Technology Infrastructure




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