[SNMP4J] IOException in DefaultUDPTransportMapping

[Frank Fock]

Hi Shenaz,

The AdventNet browser does not handle this correctly.
It should not process an incorrectly encoded SNMP
packet although it may be valid BER (where length > 32bit
are allowed).

If the client cannot be convinced that the agent bug
needs to be fixed you could implement a workaround
by changing the BER decoding of SNMP4J. However, if you
do that, you can run into DoS issues when SNMP4J tries
to process such long lengths.

Regards,
Frank

shenaz.assu at wipro.com wrote:
> Hi Frank,
> 
> Thanks a ton for such a quick reply. So you mean its game over? :(
> 
> Do you have any suggestions how I should handle this situation? The
> client does not want me to show SnmpTimeOut. Because when he checks from
> the Adventnet MibBrowser, he can see the value. Although it is an SNMP
> agent issue, I have been asked to handle it my application. 
> 
> Regards
> Shenaz
> 
> -----Original Message-----
> From: Frank Fock [mailto:fock at agentpp.com] 
> Sent: Friday, December 19, 2008 9:59 PM
> To: Shenaz Mohamed assu (WT01 - Telecom Equipment)
> Cc: snmp4j at agentpp.org
> Subject: Re: [SNMP4J] IOException in DefaultUDPTransportMapping
> 
> Hi Shenaz,
> 
> You cannot report that error back, because when you cannot decode the
> response (because of an BER encoding error), you cannot match the
> response with the request. Game over ;-)
> 
> Regards,
> Frank
> 
> shenaz.assu at wipro.com wrote:
>> Hi All,
>>  
>> I'm facing an issue with SNMP GET. While sending the PDU to the SNMP
> agent with public ResponseEvent send(PDU pdu, Target target,
> TransportMapping transport) throws IOException method, i'm getting the
> following exception. 
>>  
>> java.io.IOException: Length greater than 32bit are not supported  for 
>> integers:  at position 49 at 
>> org.snmp4j.asn1.BER.decodeInteger(BER.java:627)
>>  at org.snmp4j.smi.Integer32.decodeBER(Integer32.java:62)
>>  at org.snmp4j.smi.Variable.createFromBER(Variable.java:170)
>>  at org.snmp4j.smi.VariableBinding.decodeBER(VariableBinding.java:164)
>>  at org.snmp4j.PDUv1.decodeBER(PDUv1.java:169)
>>  at org.snmp4j.mp.MPv1.prepareDataElements(MPv1.java:170)
>>  at 
>> org.snmp4j.MessageDispatcherImpl.dispatchMessage(MessageDispatcherImpl
>> .java:241)  at 
>> org.snmp4j.MessageDispatcherImpl.processMessage(MessageDispatcherImpl.
>> java:313)  at 
>> org.snmp4j.MessageDispatcherImpl.processMessage(MessageDispatcherImpl.
>> java:276)  at 
>> org.snmp4j.transport.AbstractTransportMapping.fireProcessMessage(Abstr
>> actTransportMapping.java:81)  at 
>> org.snmp4j.transport.DefaultUdpTransportMapping$ListenThread.run(Defau
>> ltUdpTransportMapping.java:282)
>>  
>> From this what I've understood is that, the SNMP agent is returning a
> value larger than integer for the attribute that is expected to return
> an integer value. This IOException is caught and logged in
> DefaultUdpTransportMapping. So in my application I'll get ResponseEvent
> with a null PDU and i'll throw an SnmpTimeOutError as the response is
> null.
>>  
>> The problem is that I do not want to show the error as an SnmpTimeOut.
> 
>> I want to show the exact reason in my application. So I tried 
>> modifying the code and I threw a RunTimeException from the 
>> MessageDispatcherImpl after catching the IOException. Then I got the 
>> below log
>>  
>> Exception in thread "DefaultUDPTransportMapping_192.168.234.72/0" 
>> java.lang.RuntimeException: Length greater than 32bit are not 
>> supported  for integers:  at position 49  at 
>> org.snmp4j.MessageDispatcherImpl.processMessage(MessageDispatcherImpl.
>> java:324)  at 
>> org.snmp4j.MessageDispatcherImpl.processMessage(MessageDispatcherImpl.
>> java:276)  at 
>> org.snmp4j.transport.AbstractTransportMapping.fireProcessMessage(Abstr
>> actTransportMapping.java:81)  at 
>> org.snmp4j.transport.DefaultUdpTransportMapping$ListenThread.run(Defau
>> ltUdpTransportMapping.java:282)
>>  
>> My requirement is that if i get an IOException like above I want to
> throw that exception and catch it in my code so that i can give a
> clearer message. Is it possible to do that? Can anyone of you help me
> out with this? Its really urgent.
>>  
>> Thanks a lot!!
>>  
>> Best regards
>> Shenaz
>>  
>>
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