Windows Net-SNMP Handle leak (pass persist extensions ) ???

All,

Not sure if this belongs in coders or here but we think we've found another handle leak in the windows net-snmp 5.4.1.2 and 5.4.2.1 clients when walking pass persist extensions.  It does not appear that Net-SNMP is closing the handle properly and is still leaving some zombie processes around.

We have confirmed this is happening outside of our extensions and is happening within every request we send when we are requesting an oid serviced by a pass persist extension.


[cid:[email protected]]

The following is from Microsoft:


Commit: 988896K        Pool N: 83,768K  P: 91,016K      SystemUpTime(hours)=21.61   4/16/2009 5:20:46 PM



Performance monitor does show the Handle leak in Snmpd  47,651 open handles


‎‎
 !PROCESS fffffadfe7281c20
    SessionId: 0  Cid: 050c    Peb: 7efdf000  ParentCid: 0198
    DirBase: 3335e000  ObjectTable: fffffa8002de4650  HandleCount: 48289.
    Image: snmpd.exe
 kd> !handle
processor number 0, process fffffadfe7281c20
PROCESS fffffadfe7281c20
    SessionId: 0  Cid: 050c    Peb: 7efdf000  ParentCid: 0198
    DirBase: 3335e000  ObjectTable: fffffa8002de4650  HandleCount: 48289.
    Image: snmpd.exe


Handle table at fffffa80040c6000 with 48289 Entries in use
fffffa80040c6000: Unable to read handle table middle level







Process objects and thread objects in the perfmon directly correlate with the Snmpd handle leak both growing at the same rate as the handle count in Snmpd explaining the 2 high Non paged pool system tags Thre and Proc.



The memory dump provided to Microsoft shows there are 9956 Zombie extension processes this is causing the Proc Npp Pool tag to increase to its current size of 23.89 MB



The Thre non paged pool tag is high (25.40 MB) due to the zombie processes not being able to dereference memory allocations because of the open handles in Snmpd.



If you would like to confirm this



Please run perfmon at a 5 second interval, kill the snmpd Process, continue to let the perfmon run for15-20 minutes and we should see the Threads and Process Objects come down.



We have confirmed that this issue still exists in the 5.4.2.1 version of the agent.



Steps to replicate:



1. start net-snmp ( ensure there is a pass persist line in the snmpd.conf -> can point to a functional or non-functional extension.

2. start perfmon

3. select the "Process" performance object.

4. select "Handle Count" and then select the "snmpd" instance.

5. start polling the oid serviced by your pass persist extension.

6. watch the handle count climb.


Any thoughts on next steps?

Jayson Robinson
DSS Instrumentation - Performance and Hardware Monitoring Engineering
Global Technology Infrastructure
Office:  614-217-7521

[cid:[email protected]]



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