[AGENT++] SNMPv3_MP_UNKNOWN_PDU_HANDLERS error

[Jochen Katz]

Hello,

> I am not sure we are gettng a TIMEOUT , we are actually being returned
> the status - SNMPv3_MP_UNKNOWN_PDU_HANDLERS,

yes, I could verify this. There is a race condition in
Snmp::snmp_engine() function. First the request is sent and afterwards
the message is added to the list of outstanding requests. Therefore the
following can happen:

Thread 1: send request
Thread 2: process response
          v3MP deletes its state information
          no entry in msg queue -> discard
Thread 1: add request to msg queue
Thread  : resend message because of timeout
Thread  : process response
          no state information in v3MP -> unknown pdu handlers
Thread 1: returns unknown pdu handlers

I'm attaching the patch for uxsnmp.cpp/h, but as it won't go through
mailman, list members have to wait for the next snapshot at
http://oosnmp.com/~katz/snapshot/

Regards,
  Jochen
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