[SNMP4J] V3 traps failing when multiple senders exist.

[Frank Fock]

Hi David,

If you read the SNMPv3 RFCs carefully you will see that
it cannot work what you are trying.
SNMP4J handles the different situations correctly.
The .0 is the suffix of a scalar. It will never be incremented.
The value of the counter increments, though.

There are two possible solutions:

(1) Add the user (can be same security name/password)
for each trap sender's engine ID. How you get that uniqe(!)
engine ID is implementation/scenario dependent.

(2) Use INFORM PDUs instead TRAPs/NOTIFICATIONs. With
INFORM, the PDU receiver is authoritative. Thus, you can
use a single username/password with all inform senders.

Best regards,
Frank

Am 06.03.2012 22:37, schrieb david jones:
> I was trying to test code that receives traps from 2 different senders
> using the same security name, but different passwords.  One senders PDUs
> are parsed correctly, the others are not (mostly  1.3.6.1.6.3.15.1.1.5.0 =
> 0 (wrong digest)).   I assume i have to do an addUser() for each different
> password, what else is needed? do i also need to set the engineID for each
> addUser?
>
> I tried some scaffolding code that created a UserTarget for each sender's
> IP and then did " discoverAuthoritativeEngineID(userTarget.getAddress(),
> 5000)", with intent of adding the found engineID to the addUser but the
> results were empty, but is that on the right track? Or is there something
> (unique engineIDs?) senders aren't generating correctly?
>
> I then tried getting rid of the multiple users and try it with just one
> addUser and all senders using the same password: Still only one of the
> senders PDUs are successfully read, the others are rejected, now
> with 1.3.6.1.6.3.15.1.1.5.2.0 = 0 (not in time window). Is this still the
> same underlying cause, or do i need to reboot the receivers and senders to
> resynch or ??
>
> I also noticed the warnings messages that indicate errors all have *oid = *0.
> Isn't the = n value supposed to be incrementing, not always 0?
>
> Below is a code snipet:
>
> transport = new DefaultUdpTransportMapping(new
> UdpAddress(ServerProperties.getSnmpTrapPort()));  // using private port,
> not 161/162
>   MessageDispatcher mtDispatcher = new MessageDispatcherImpl();
>   // add message processing models
>   mtDispatcher.addMessageProcessingModel(new MPv1());
>   mtDispatcher.addMessageProcessingModel(new MPv2c());
>   mtDispatcher.addMessageProcessingModel(new MPv3());
>   // add all security protocols
>   SecurityProtocols.getInstance().addDefaultProtocols();
>
>   snmp = new Snmp(mtDispatcher, transport);
>
>
>   if (version == SnmpConstants.version3) {
>       usm = new USM(SecurityProtocols.getInstance(), engineID, 0);
>       SecurityModels.getInstance().addSecurityModel(usm);
>
>
>       snmp.setLocalEngine(engineID.getValue(), 0, 0);
>
>       // Add some predefined users
>
>       snmp.getUSM ().addUser (
> new OctetString ("mytrap"),
> new UsmUser (
> new OctetString ("mytrap"), AuthMD5.ID,
>          new OctetString ("AAAAAAAA"),null,null);
>
>       snmp.getUSM ().addUser (
> new OctetString ("mytrap"),
>     new UsmUser (
> new OctetString ("mytrap"), AuthMD5.ID,
> new OctetString ("BBBBBBBB"),null,null);
>
>   }
> snmp.addCommandResponder(this);
> transport.listen();
>

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