Re: [SNMP4J] SNMP4J Digest, Vol 93, Issue 1

Frank Fock Wed, 15 Oct 2014 10:31:17 -0700

Hello Matyas,

I am afraid, that you need to choose another caching key.
Requests can get lost (it's UDP) and then request IDs can
increase randomly. In addition, senders are not required
to increase the ID at all. Some managers reuse the same
request ID when a previous request has been successfully
received (which is legal and works perfectly with a
standard conform agent, although logfiles are hard to read
then ;-))


Best regards,
Frank

Am 15.10.2014 10:20, schrieb Mátyás Kuti:

Hello,

Thanks for your answer Frank!
The goal of the whole thing was to create an SNMP agent that accepts
GETNEXT requests from multiple clients. We built a response cache on the
first request for each client and based on the request ID of an incoming
request the proper response was sent. The response itself was determined by
the request ID. We expected that each ID would be in the range of (First
ID, First ID+Number of fields to send) but since the IDs are not always
incremented by 1 this solution would mess things up a bit... It works
perfectly when tested by hand using the snmpwalk command on Linux but when
we wrote the automatic tests in Java using SNMP4J the tests failed. Do you
have any idea how to solve the problem of concurrent GETNEXT requests?

Thanks,
Matyas

2014-10-14 12:00 GMT+02:00 <[email protected]>:

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Today's Topics:

    1. Question regarding request id when doing getnext (Mátyás Kuti)
    2. Re: Question regarding request id when doing getnext (Frank Fock)


----------------------------------------------------------------------

Message: 1
Date: Mon, 13 Oct 2014 13:23:01 +0200
From: Mátyás Kuti <[email protected]>
To: [email protected]
Subject: [SNMP4J] Question regarding request id when doing getnext
Message-ID:
         <
cap-cjjb0g4ssy+teyvgcyukcnzgjf8csmqk+f0aluypu1mt...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

Hello,

We are doing the following:

List<VariableBinding> snmpTable = new ArrayList<VariableBinding>();
         for (TreeEvent event : events) {
             if (event != null) {
                 if (event.isError()) {
                     logger.info
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2flogger.info

("oid

[" + oid + "] " + event.getErrorMessage());
                 }
                 VariableBinding[] varBindings =
event.getVariableBindings();
                 if (varBindings == null || varBindings.length == 0) {
                     continue;
                 }
                 for (VariableBinding varBinding : varBindings) {
                     snmpTable.add(varBinding);
                 }
             }
         }
...

And we have enforced the GETNEXT behavior by setting:
mTarget.setVersion(SnmpConstants.version1);

We experience, that the request IDs increase by 2 instead of the expected
1:

Java-log output:

2014-09-30 15:05:05,888 [DEBUG] Received message from /192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 58:

30:38:02:01:00:04:05:74:72:61:70:73:a2:2c:02:04:1b:b0:d2:2d:02:01:00:02:01:00:30:1e:30:1c:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:30:04:08:07:de:09:1e:0d:02:27:1e
2014-09-30 15:05:05,888 [DEBUG] Looking up pending request with handle
PduHandle[464572973]
2014-09-30 15:05:05,888 [DEBUG] Cancelling pending request with handle
PduHandle[464572973]
2014-09-30 15:05:05,888 [DEBUG] Running pending async request with handle
PduHandle[464572975] and retry count left 1
2014-09-30 15:05:05,888 [DEBUG] Sending message to 192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a1:24:02:04:1b:b0:d2:2f:02:01:00:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:30:05:00
2014-09-30 15:05:05,941 [DEBUG] Received message from /192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 58:

30:38:02:01:00:04:05:74:72:61:70:73:a2:2c:02:04:1b:b0:d2:2f:02:01:00:02:01:00:30:1e:30:1c:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:31:04:08:07:de:09:1e:0d:02:27:50
2014-09-30 15:05:05,941 [DEBUG] Looking up pending request with handle
PduHandle[464572975]
2014-09-30 15:05:05,941 [DEBUG] Cancelling pending request with handle
PduHandle[464572975]
2014-09-30 15:05:05,941 [DEBUG] Running pending async request with handle
PduHandle[464572977] and retry count left 1
2014-09-30 15:05:05,941 [DEBUG] Sending message to 192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a1:24:02:04:1b:b0:d2:31:02:01:00:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:31:05:00
2014-09-30 15:05:05,978 [DEBUG] Received message from /192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 58:

30:38:02:01:00:04:05:74:72:61:70:73:a2:2c:02:04:1b:b0:d2:31:02:01:00:02:01:00:30:1e:30:1c:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:32:04:08:07:de:09:1e:0d:02:28:1a
2014-09-30 15:05:05,978 [DEBUG] Looking up pending request with handle
PduHandle[464572977]
2014-09-30 15:05:05,978 [DEBUG] Cancelling pending request with handle
PduHandle[464572977]
2014-09-30 15:05:05,978 [DEBUG] Running pending async request with handle
PduHandle[464572979] and retry count left 1
2014-09-30 15:05:05,978 [DEBUG] Sending message to 192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a1:24:02:04:1b:b0:d2:33:02:01:00:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:32:05:00
2014-09-30 15:05:06,026 [DEBUG] Received message from /192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 58:

30:38:02:01:00:04:05:74:72:61:70:73:a2:2c:02:04:1b:b0:d2:33:02:01:00:02:01:00:30:1e:30:1c:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:33:04:08:07:de:09:1e:0d:02:28:3d
2014-09-30 15:05:06,026 [DEBUG] Looking up pending request with handle
PduHandle[464572979]
2014-09-30 15:05:06,026 [DEBUG] Cancelling pending request with handle
PduHandle[464572979]
2014-09-30 15:05:06,027 [DEBUG] Running pending async request with handle
PduHandle[464572981] and retry count left 1
2014-09-30 15:05:06,027 [DEBUG] Sending message to 192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a1:24:02:04:1b:b0:d2:35:02:01:00:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:33:05:00
2014-09-30 15:05:06,077 [DEBUG] Received message from /192.168.210.1/30165
<
https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165
with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a2:24:02:04:1b:b0:d2:35:02:01:05:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:33:05:00
2014-09-30 15:05:06,077 [DEBUG] Looking up pending request with handle
PduHandle[464572981]
2014-09-30 15:05:06,077 [DEBUG] Cancelling pending request with handle
PduHandle[464572981]

We expect on the agent side that the request IDs increase by 1 just as with
netsnmp's snmpwalk. This behaviour (the request ID increasing by 2) was
verified with a TCP dump also.
What could cause this behaviour? Any idea how to fix it?

Thanks a lot,
Matyas


------------------------------

Message: 2
Date: Mon, 13 Oct 2014 23:04:00 +0200
From: Frank Fock <[email protected]>
To: [email protected]
Subject: Re: [SNMP4J] Question regarding request id when doing getnext
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8; format=flowed

Hi,

You cannot expect anything from a request ID other than it is unique
as long as the agent is running (and the range of available numbers
is not exhausted).

SNMP4J (currently) also generates an ID for each response which has the
advantage, that even if the response cannot be fully parsed, it cannot
accidentially related to an existing request.

I will check, if I can remove that ID generation safely. Meanwhile
you have two options:

1. Ignore that fact (according to the SNMP standard, it should not be
relevant
in practice).
2. Generate your own request ID and set it in the PDU before providing it
to the Snmp class for sending.

Hope this helps.

Best regards,
Frank


Am 13.10.2014 13:23, schrieb Mátyás Kuti:

Hello,

We are doing the following:

List<VariableBinding> snmpTable = new ArrayList<VariableBinding>();
          for (TreeEvent event : events) {
              if (event != null) {
                  if (event.isError()) {
                      logger.info
<

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2flogger.info

("oid
[" + oid + "] " + event.getErrorMessage());
                  }
                  VariableBinding[] varBindings =

event.getVariableBindings();

                  if (varBindings == null || varBindings.length == 0) {
                      continue;
                  }
                  for (VariableBinding varBinding : varBindings) {
                      snmpTable.add(varBinding);
                  }
              }
          }
...

And we have enforced the GETNEXT behavior by setting:
mTarget.setVersion(SnmpConstants.version1);

We experience, that the request IDs increase by 2 instead of the

expected 1:

Java-log output:

2014-09-30 15:05:05,888 [DEBUG] Received message from /

192.168.210.1/30165

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 58:

30:38:02:01:00:04:05:74:72:61:70:73:a2:2c:02:04:1b:b0:d2:2d:02:01:00:02:01:00:30:1e:30:1c:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:30:04:08:07:de:09:1e:0d:02:27:1e

2014-09-30 15:05:05,888 [DEBUG] Looking up pending request with handle
PduHandle[464572973]
2014-09-30 15:05:05,888 [DEBUG] Cancelling pending request with handle
PduHandle[464572973]
2014-09-30 15:05:05,888 [DEBUG] Running pending async request with handle
PduHandle[464572975] and retry count left 1
2014-09-30 15:05:05,888 [DEBUG] Sending message to 192.168.210.1/30165
<

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a1:24:02:04:1b:b0:d2:2f:02:01:00:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:30:05:00

2014-09-30 15:05:05,941 [DEBUG] Received message from /

192.168.210.1/30165

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 58:

30:38:02:01:00:04:05:74:72:61:70:73:a2:2c:02:04:1b:b0:d2:2f:02:01:00:02:01:00:30:1e:30:1c:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:31:04:08:07:de:09:1e:0d:02:27:50

2014-09-30 15:05:05,941 [DEBUG] Looking up pending request with handle
PduHandle[464572975]
2014-09-30 15:05:05,941 [DEBUG] Cancelling pending request with handle
PduHandle[464572975]
2014-09-30 15:05:05,941 [DEBUG] Running pending async request with handle
PduHandle[464572977] and retry count left 1
2014-09-30 15:05:05,941 [DEBUG] Sending message to 192.168.210.1/30165
<

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a1:24:02:04:1b:b0:d2:31:02:01:00:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:31:05:00

2014-09-30 15:05:05,978 [DEBUG] Received message from /

192.168.210.1/30165

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 58:

30:38:02:01:00:04:05:74:72:61:70:73:a2:2c:02:04:1b:b0:d2:31:02:01:00:02:01:00:30:1e:30:1c:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:32:04:08:07:de:09:1e:0d:02:28:1a

2014-09-30 15:05:05,978 [DEBUG] Looking up pending request with handle
PduHandle[464572977]
2014-09-30 15:05:05,978 [DEBUG] Cancelling pending request with handle
PduHandle[464572977]
2014-09-30 15:05:05,978 [DEBUG] Running pending async request with handle
PduHandle[464572979] and retry count left 1
2014-09-30 15:05:05,978 [DEBUG] Sending message to 192.168.210.1/30165
<

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a1:24:02:04:1b:b0:d2:33:02:01:00:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:32:05:00

2014-09-30 15:05:06,026 [DEBUG] Received message from /

192.168.210.1/30165

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 58:

30:38:02:01:00:04:05:74:72:61:70:73:a2:2c:02:04:1b:b0:d2:33:02:01:00:02:01:00:30:1e:30:1c:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:33:04:08:07:de:09:1e:0d:02:28:3d

2014-09-30 15:05:06,026 [DEBUG] Looking up pending request with handle
PduHandle[464572979]
2014-09-30 15:05:06,026 [DEBUG] Cancelling pending request with handle
PduHandle[464572979]
2014-09-30 15:05:06,027 [DEBUG] Running pending async request with handle
PduHandle[464572981] and retry count left 1
2014-09-30 15:05:06,027 [DEBUG] Sending message to 192.168.210.1/30165
<

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a1:24:02:04:1b:b0:d2:35:02:01:00:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:33:05:00

2014-09-30 15:05:06,077 [DEBUG] Received message from /

192.168.210.1/30165

https://mail.internal.ericsson.com/owa/redir.aspx?C=2ipCqKJBBEyRoKqLqlcn5EPTOE5putEI6g7WPUCTE6ZOVwcy2_JaQ_aA843rf0UcX-2b_mw8x5E.&URL=http%3a%2f%2f192.168.210.1%2f30165

with length 50:

30:30:02:01:00:04:05:74:72:61:70:73:a2:24:02:04:1b:b0:d2:35:02:01:05:02:01:00:30:16:30:14:06:10:2b:06:01:04:01:81:41:81:37:04:01:03:05:01:08:33:05:00

2014-09-30 15:05:06,077 [DEBUG] Looking up pending request with handle
PduHandle[464572981]
2014-09-30 15:05:06,077 [DEBUG] Cancelling pending request with handle
PduHandle[464572981]

We expect on the agent side that the request IDs increase by 1 just as

with

netsnmp's snmpwalk. This behaviour (the request ID increasing by 2) was
verified with a TCP dump also.
What could cause this behaviour? Any idea how to fix it?

Thanks a lot,
Matyas
_______________________________________________
SNMP4J mailing list
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https://oosnmp.net/mailman/listinfo/snmp4j

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------------------------------

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------------------------------

End of SNMP4J Digest, Vol 93, Issue 1
*************************************

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Re: [SNMP4J] SNMP4J Digest, Vol 93, Issue 1

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