[AGENT++] SNMPV3 - Data size problem

[Shrikanth D]

Hi Frank,
 
With reference to the mail below, I find this problem recurring with the new version of SNMP++ too. I am using 3.2.9a, but the agent still does not send a response if the requested number of rows in getBulk is high and it timesout displaying the below given error!
 
////////////////////////////////////////////////////////////////////////
> usmBuildWholeMsg error: msgDataLength = 2068
> maxLength = 2028, encoded = 85
> usm: could not generate wholeMsg
> v3MP finished NOT OK: errorcode 1401.
> 
////////////////////////////////////////////////////////////////////////

With respect to increasing the message size, I have the following queries,
 
1. Is it sufficient if only the sender's maxMessageSize is modified?
2. Should both the below macros be modified as either could be a limiting factor?
 
config_snmp_pp.h(36):#define PDU_MAX_VBS 50
config_snmp_pp.h(39):#define MAX_SNMP_PACKET 4096
 
3. What is the maximum value that i can set both the macros to?
4. Is anything else required to be done?
 
Thanks and regards,
Shrikanth
 
================================================================

================================================================
Frank Fock wrote:
 
Hi Shrikanth,
The debugging output shows the sender of request
(the management app) does not allow the response
to be longer then 2028 bytes. AGENT++ has encoded
a response with 2068 bytes which is > 2028. That's
why the response could not be send. The latest
version of AGENT++ should be able to precisly forecast
the length of a PDU and return a smaller one if the
request is a GETBULK.
If you are using the latest version, then this might
be a bug in AGENT++. As a workaround you could increase
the maxMessageSize of the sending application.
Best regards,
Frank Fock
Shrikanth D wrote:
> Hi,
>  
> I am developing a snmp V3 agent.
> I have a Mib table with more than 20 columns in it - many of them 
strings.
>  
> When a snmp manager requests just 1 row from this table using getBulk 
> everything works fine.
> But when the manager requests more rows in its getBulk request - say 
10 
> rows, then I see the following error message on the console and no 
> response is sent back to the manager.
>  
> 
////////////////////////////////////////////////////////////////////////
> usmBuildWholeMsg error: msgDataLength = 2068
> maxLength = 2028, encoded = 85
> usm: could not generate wholeMsg
> v3MP finished NOT OK: errorcode 1401.
> 
////////////////////////////////////////////////////////////////////////
>  
> As I understand, irrespective of the number of rows the manager 
> requests, the agent must fill the maximum possible complete rows and 
> return. But this error is perplexing.
> Should the manager then only request one row by row?
>  
> I have another related query, presently the size of a snmp pdu is 
being 
> limited to around 1k. What happens, if a single row of a table 
exceeds 
> this limit? This is quite possible in my case!
>  
> Thanks and regards,
> Shrikanth




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