[AGENT++] NULL values in a successful Get response

[Marek Malowidzki]

Hi,

we are getting NULL values returned by an Agent++ agent in a successful
response to a Get request. Trace is as follows:

D:\SN\snmp_ppnet\VS.NET\SnmpManager\bin\Debug>snmpmanager get
10.1.0.158 -o1.3.6
.1.2.1.2.2.1.2.1 -o 1.3.6.1.2.1.2.2.1.3.1 -p5161
Initialized request_id to 9181.
Initializing AuthPriv
Initialized salt to 0xB83E.
Added Auth object with id (3).
Added Auth object with id (2).
Added Priv object with id (2).
Added default Auth and Priv protocols.
[0]: Sending PDU to target 10.1.0.158/5161,SNMPv1,public,public
oid [0]: 1.3.6.1.2.1.2.2.1.2.1
val [0]:  (Null)
oid [1]: 1.3.6.1.2.1.2.2.1.3.1
val [1]:  (Null)
snmp_engine called with CTarget
SnmpMsg: return status of snmpBuild (0)
++ SNMP++: sending to 10.1.0.158/5161:
30 39 02 01  00 04 06 70  75 62 6C 69  63 A0 2C 02
02 23 DE 02  01 00 02 01  00 30 20 30  0E 06 0A 2B
06 01 02 01  02 02 01 02  01 05 00 30  0E 06 0A 2B
06 01 02 01  02 02 01 03  01 05 00
++ SNMP++: something received...
Length received 61 from socket 1736; fromlen 16
++ SNMP++: data received from 10.1.0.158/5161.
30 3B 02 01  00 04 06 70  75 62 6C 69  63 A2 2E 02
02 23 DE 02  01 00 02 01  00 30 22 30  10 06 0A 2B
06 01 02 01  02 02 01 02  01 04 02 6C  6F 30 0E 06
0A 2B 06 01  02 01 02 02  01 03 01 05  00
receive_snmp_response requestID = 9182, returning SUCCESS.
[0]: Received PDU:
oid [0]: 1.3.6.1.2.1.2.2.1.2.1
val [0]: lo (OctetString)
oid [1]: 1.3.6.1.2.1.2.2.1.3.1
val [1]:  (Null)
1 synchronous SNMP request(s) in 109 msec. (9,14285714285714 req./sec.)

The question is: How this is possible? This could be our bug, of course, but
I believe that NULLs in values should never be observed for a response with
error-status equal to 0 (Success). This happens for table entries when there
are more VBs than one. Of course, all variables, for which NULLs are
returned, are available (when we Get using a single VB, everything is ok).

Agent++ version is 3.5.20a, SNMP++: 3.2.13.

Best regards,

Marek