Hi Chris,
It's not a bug, it's a feature. The SNMP standard(s) have
caused that. The nonRepeaters field is the same as
the errorStatus field on the wire (repeaters = error index).
That works, because when you send a GETBULK request,
an error condition does not make sense (for the agent).
The repsonse then contains the error status and index
which is "overwritten" by the agent.
Best regards,
Frank
Am 17.09.2011 09:40, schrieb Chris Richmond:
> We have been using the Snmp4j v2.0 library for a while now in testing
> and have begun to do some error condition handling when I came across
> something which seems either wrong or confusing to me
>
> I noticed that when performing a bulk request and setting the
> PDU.setNonRepeaters() method that no matter what, the PDU always had an
> error code that made no sense even though the call worked just fine.
>
> I narrowed the error state change down to this granularity, where the
> pdu is the snmp4j PDU instance
>
> System.err.println("pdu error string: " + getErrorString());
> pdu.setNonRepeaters(nonRepeaters);
> System.err.println("pdu error string: " + pdu.getErrorStatusText());
>
>
> And this would always return
>
> Success
> <Some error message based on the number of repeaters I set>
>
>
> The API documentation states that:
>
>
> setNonRepeaters
>
> public void*setNonRepeaters*(int nonRepeaters)
>
> Sets the number of non repeater variable bindings in a GETBULK PDU.
>
> *Parameters:*
> |nonRepeaters| - an integer value>= 0 and<= |size()|
> <http://www.snmp4j.org/doc/org/snmp4j/PDU.html#size%28%29>
>
> I ensured there was no variable list size problem, and I downloaded the
> source to see what was happening inside the PDU class.
>
> Here is the method inside the PDU class from source
>
> /**
> * Sets the number of non repeater variable bindings in a GETBULK PDU.
> * @param nonRepeaters
> * an integer value>= 0 and<= {@link #size()}
> */
> public void setNonRepeaters(int nonRepeaters) {
> this.errorStatus.setValue(nonRepeaters);
> }
>
>
> Now I am confused. It simply takes the number of repeaters and sets it
> directly to the error status, with no @link #size() logical check of any
> kind. This integer for the number of non repeaters is then used
> directly by the method:
>
> /**
> * Gets a textual description of the error status.
> * @return
> * a String containing an element of the
> * {@link SnmpConstants#SNMP_ERROR_MESSAGES} array for a valid
> error status.
> * "Unknown error:<errorStatusNumber>" is returned for any other
> value.
> */
> public String getErrorStatusText() {
> return toErrorStatusText(errorStatus.getValue());
> }
>
> with the internal method toErrorStatusText simply mapping whatever
> integer to the SnmpConstants.SNMP_ERROR_MESSAGES index
>
> public static final String toErrorStatusText(int errorStatus) {
> try {
> return SnmpConstants.SNMP_ERROR_MESSAGES[errorStatus];
> }
> catch (ArrayIndexOutOfBoundsException iobex) {
> return "Unknown error: "+errorStatus;
> }
> }
>
> public static final String[] SNMP_ERROR_MESSAGES = {
> "Success",
> "PDU encoding too big",
> "No such name",
> "Bad value",
> "Variable is read-only",
> "General variable binding error",
> "No access",
> "Wrong type",
> "Variable binding data with incorrect length",
> "Variable binding data with wrong encoding",
> "Wrong value",
> "Unable to create object",
> "Inconsistent value",
> "Resource unavailable",
> "Commit failed",
> "Undo failed",
> "Authorization error",
> "Not writable",
> "Inconsistent naming used"
>
>
> So I ran another test, and sure enough whatever value I pass in for the
> number of non-repeaters, simply equates directly to some error status on
> the PDU object with no other mitigating logic.
>
> I also downloaded the latest snapshot 2.3 and this code is the same.
>
> This seems like a pretty straightforward bug, but am I missing something?
>
> Thanks,
> Chris
>
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