[SNMP4J] SNMP broadcasts, PDUv1 with Counter64 (in 1.9.1)

[Frank Fock]

Hi Christof,

Sorry, this seems to be indeed a regression.
Please try the fix below to fix broadcast
async request processing:

Index: Snmp.java
===================================================================
--- Snmp.java	(revision 402)
+++ Snmp.java	(working copy)
@@ -1117,17 +1117,7 @@
        synchronized (pendingRequests) {
          request = (PendingRequest) pendingRequests.get(handle);
          if (request != null) {
-          if (request.isResponseReceived()) {
-            pendingRequests.remove(handle);
-            request = null;
-            if (logger.isInfoEnabled()) {
-              logger.info("Received second response for request with 
handle "+
-                          handle);
-            }
-          }
-          else {
-            request.responseReceived();
-          }
+          request.responseReceived();
          }
        }
        if (request == null) {


I will consider isolating the Counter64 check into
a protected method.

Best regards,
Frank



Christof Meerwald wrote:
> Hi,
> 
> it appears that with 1.9.1 SNMP broadcasts don't work any more - to be
> more precise, you now only get the first response (with code that
> worked perfectly fine with previous snmp4j versions). I think this is
> related to the following "fix" in 1.9.1:
> 
> "Fixed: With async request processing and retry>0 there could have been
> a race condition where a response event had been generated twice for a
> request."
> 
> which appears to now only allow a single response event for each
> request (even if the request is not cancelled in the listener as
> mentioned in the JavaDoc: "Not canceling a request immediately can be
> useful when sending a request to a broadcast address.")
> 
> 
> I also noticed that 1.9.1 now contains a factory interface for creating
> the PDU class for incoming messages. While this allows one to provide a
> PDUv1 class that doesn't throw an exception when encountering a
> Counter64 value, it's still a bit of a hassle as it requires quite a
> bit of code duplication. I think, snmp4j could quite easily simplify
> that particular case further by moving the Counter64 check into a
> separate method. That way, a derived "PDUv1WithCounter64" could easily
> overwrite that method without having to duplicate any of the decodeBER
> code. So my proposal would be to add a new protected method to PDUv1:
> 
> protected void checkVariableBindingSyntax(VariableBinding vb)
>   throws IOException
> {
>   if (vb.getSyntax() == SMIConstants.SYNTAX_COUNTER64) {
>     throw new MessageException("Counter64 encountered in SNMPv1 PDU
> "+
>                                "(RFC 2576 §4.1.2.1)");
>   }
> }
> 
> and call checkVariableBindingSyntax(vb) in decodeBER (line 169).
> 
> Any thoughts on this?
> 
> 
> Christof
> 

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