SNMP v3 Not Thread Safe even using Single Session API

[John McCaskey]

Hey,

We've got a enterprise app with a net-snmp library based backend monitoring engine.  It's highly multi-threaded (ie about 100-200 worker threads doing snmp get/getnexts's at any given time.  I was under the impression from reading http://www.net-snmp.org/docs/README.thread.html that as long as I stuck to the Single Session API for forming and sending requests I would be ok.  However, it appears that while this is true for v1 and v2c requests it does not apply to v3.  The base of the problem seems to be that ./snmplib/snmpusm.c defines a global linked list (userList) to track users generated in the usm security model.  This list gets modified (indirectly through several other calls) when one calls snmp_sess_open (maybe snmp_sess_close as well?).  This is causing me a major headache and random segfaults in my application and we're going to have to pull v3 support for the moment.

Is this a known issue?  Is there work towards making v3 thread safe when using the single session API?  My first ignorant thought it just put the userList in the session object... but maybe its not that simple.  I do notice at the end of README.thread it does list restrictions but nothing about v3.  The closest thing seems to be a mention of SNMPv2p but that doesn't appear to be one and the same to v3 and the usm issue.  At the very least someone should update the README.thread to warn of this issue.  If I don't get feedback telling me I'm crazy or this is known I'll post a bug and try to work up a simple c program to reproduce the issue in the next couple days.

John