Re: Understanding snmpwalk

Hi Dave,
 
This is part of my MIB output using snmptranslate
 
 
MyTables
|-------- Table1
            |-------- Table1Entry
            |           |-------   Index:   RowIndex
            |           |           
            |           |----------------    Iteger32            RowIndex
            |           |------    CR       String               AlarmDateTime
            |           |------    CR       String               AlarmType
            |           |------    CR       String               AlarmDescription
            Table2  
            |-------- Table2Entry
                        |-------- Index:   RowIndex
                        |
                        |----------------    Integer32          RowIndex
                        |------    RW      String               IPAddress
                        |------    RW      Integer32          PortNumber
                        |------    RW      Integer32          Enabled
 
 
I have 3 modules;
 

agent.c agent.h
table.c table.h
conf.c conf.h
 
 
agent.c implements all the scalars oid on my mib, also, it implements the Table1 handler using net-snmp helper handler.  The initialization is called initialize_alarm_helper();
table.c contains my custom handlers for Table1.  If I include this module, I disable the net-snmp helper handler above (initialize_alarm_helper());
conf.c contains my custom handlers for Table2.
 
Table1 has 2 rows, RowIndex=1 to 2
Table2 has 4 rows, RowIndex=0 ~ 3
 
With snmpd compiled with agent, table, conf modules (no net-snmp helper handler)
snmpwalk –v1 –cprivate localhost IPAddress        // works OK
snmpwalk –v1 –cprivate localhost PortNumber      // works OK
snmpwalk –v1 –cprivate localhost Enabled           // works OK
 
snmpwalk –v1 –cprivate localhost AlarmDateTime // works OK
snmpwalk –v1 –cprivate localhost AlarmType        // works OK
snmpwalk –v1 –cprivate localhost AlarmDescription // hangs @ AlarmDescription.2
 
I used snmpd –Dagent, table, conf –d
And snmpd.log reveals that 
 
snmpwalk-v1 –cprivate localhost AlarmDescription
 
issue getnext and conf.c MODE_GET handler is called.  So you are right, the problem is in Table2.
 
I removed table.c module, and compile snmpd with agent.c (using net-snmp helper handler) and conf.c.  and I get the same results.
 
I further remove conf.c module and compile only with snmpd with agent.c (using net-snmp helper handler) only.  The problem is gone, snmpd does not hangs on AlarmDescription.2
This is what I got with snmpd (--with-mib-modules=”agent”) when invoking snmpgetnext
 
snmpgetnext –v1 –cprivate localhost AlarmDescription.2
UCD-SNMP-MIB::memIndex.0 = INTEGER: 0
 
Of course, this is with the net-snmp helper, I will try with my own module (snmpd –agent.c table.c) and see if there’s any errors.
 
Leo;

--- On Tue, 10/19/10, Dave Shield <[email protected]> wrote:


From: Dave Shield <[email protected]>
Subject: Re: Understanding snmpwalk
To: "Leo Lin" <[email protected]>
Cc: "Net-snmp-users" <[email protected]>
Date: Tuesday, October 19, 2010, 5:29 AM


On 19 October 2010 13:20, Leo Lin <[email protected]> wrote:
> Actually I have 2 tables, and on both it behaves differently.

What are the root OIDs of each table?
What other objects are defined between the two?


> On both tables, if I perform snmpgetnext, it works fine.

That's a bit vague.
What OIDs are you running "snmpgetnext" on?

Remember, I suggested you ran snmpgetnext on the *last*
instance of the table.   I.e. the final value returned by snmpwalk
before it hangs.


> I'm going to try to revert table 1 using the netsnmp helper handler
> instead, to check if this happens with the helper as well.

My suspicion is actually with table2, not table1.
But you haven't given enough detail to confirm this.

Dave

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