Re: [pysnmp-users] Getting extra blank elements in 4.3.2

[Ilya E. <il...@gl...>]

That was a change in pysnmp 4.3 caused by the introduction of NotificationType object. Now all MIB objects implicitly required for a given notification (through NOTIFICATION-TYPE macro) will be added blank to TRAP PDU. I believe you should be able to pass actual variables either through ‘objects’ dict or by passing them to .addVarBinds():

    NotificationType(
        ObjectIdentity('DISMAN-EVENT-MIB', 'mteTriggerFired'),
        instanceIndex=(0,),
        objects={('DISMAN-EVENT-MIB', 'mteHotTrigger'): 'trigger',
                       ('DISMAN-EVENT-MIB', 'mteHotTargetName'): 'target',
                       ('DISMAN-EVENT-MIB', 'mteHotContextName'): 'context',
                       ('DISMAN-EVENT-MIB', 'mteHotOID'): '1.3.6.1.1.1',
                       ('DISMAN-EVENT-MIB', 'mteHotValue'): 1234}
    )

or

    NotificationType(
        ObjectIdentity('DISMAN-EVENT-MIB', 'mteTriggerFired'),
        instanceIndex=(0,)
    ).addVarBinds(
        ObjectType(ObjectIdentity('DISMAN-EVENT-MIB', 'mteHotContextName', 0), 'test’),
        ...
    )

Please, try the latest pysnmp from github:

    https://github.com/etingof/pysnmp

Also make sure to use NotificationType for initializing TRAPs rather than MibVariable objects. 

> On 17 Feb 2016, at 02:27, evi...@em... wrote:
> 
> Basically, the code that was working in 4.2.5 broke in 4.3.0. If I look at
> it in wireshark, in 4.3.2 I have 2 repeated elements, with Null as the
> value. I'm not sure if I'm using pysnmp correctly or if a bug got
> introduced.
> 
> Rest of message is Python code and MIB file for a minimal reproduction.
> 
> -----
> 
> from pysnmp.smi import builder
> from pysnmp.entity import engine
> from pysnmp.entity.rfc3413.oneliner import ntforg
> import os.path
> class SNMPSender(object):
>    """Will send a SNMP trap to a specific ip address, based on an event's
> data"""
>    def __init__(self, ip, port=162):
>        self.ip = ip
>        self.port = int(port)
>        snmp_engine = engine.SnmpEngine()
>        mib_builder =
> snmp_engine.msgAndPduDsp.mibInstrumController.mibBuilder
>        mib_builder.setMibSources(builder.DirMibSource(os.path.join(os.path.dirname(__file__),
> "pysnmp_mibs")),
>                                  *mib_builder.getMibSources())
>        self.ntf_org = ntforg.NotificationOriginator(snmp_engine)
>    def send_event(self, event_name, event_category):
>        self.ntf_org.sendNotification(
>            ntforg.CommunityData('public'),  # Login data; might need to
> be replaced.
>            ntforg.UdpTransportTarget((self.ip, self.port)),  # actual
> connection info
>            'trap',  # type of data we're sending
>            ntforg.MibVariable('EVENTS-MIB', 'eventNotice'),  # actual
> data we're sending
>            (ntforg.MibVariable('EVENTS-MIB', 'eventName'), event_name),
>            (ntforg.MibVariable('EVENTS-MIB', 'eventCategory'),
> event_category)
>        )
> SNMPSender("4.3.2.1").send_event("event_name", "event_category")
> 
> -----
> 
> EVENTS-MIB DEFINITIONS ::= BEGIN
> -- If you edit this file, you also need to regenerate the .py file
> associated with this:
> -- Use the page at https://www.ibr.cs.tu-bs.de/bin/smitools.cgi to convert
> to Python format (smidump, target format Python). Save the result to a
> file.
> -- On a Linux-like system (cygwin will work), run "cat result_file |
> python libsmi2pysnmp", sending the result to a file. libsmi2pysnmp is
> located in Python27/Scripts if pysnmp is installed.
> 
> IMPORTS
>    MODULE-IDENTITY, NOTIFICATION-TYPE,
>    OBJECT-TYPE, enterprises
>        FROM SNMPv2-SMI
>    MODULE-COMPLIANCE, NOTIFICATION-GROUP, OBJECT-GROUP
>        FROM SNMPv2-CONF;
> 
> -- Most of this is just for human consumption. If you edit this, I suggest
> editing LAST-UPDATED and adding a new REVISION/DESCRIPTION set.
> eventMIB MODULE-IDENTITY
>    LAST-UPDATED "201507010000Z"
>    ORGANIZATION "---"
>    CONTACT-INFO
>            "---"
>    DESCRIPTION
>            "MIB file. Currently just holds event information for
> generation of SNMP traps."
>    REVISION      "201507010000Z"
>    DESCRIPTION
>            "Initial revision"
>    ::= { enterprises 37033 }
> 
> -- information for notifications
> 
> eventTraps      OBJECT IDENTIFIER ::= { eventMIB 0 }
> eventObjects      OBJECT IDENTIFIER ::= { eventMIB 1 }
> 
> -- These are basically from the event object.
> eventName OBJECT-TYPE
>  SYNTAX OCTET STRING  -- max length 65536
>  MAX-ACCESS  read-only
>  STATUS current
>  DESCRIPTION
>    "A string indicating the type of notification. Corresponds with event
> name."
> ::= { eventObjects 1 }
> 
> eventCategory OBJECT-TYPE
>  SYNTAX OCTET STRING
>  MAX-ACCESS  read-only
>  STATUS current
>  DESCRIPTION
>    "The name of the module/app sending the notification. Corresponds with
> event category."
> ::= { eventObjects 2 }
> 
> -- This is the actual trap. There is no special significance to 2.
> eventNotice NOTIFICATION-TYPE
>    OBJECTS     { eventName, eventCategory }
>    STATUS  current
>    DESCRIPTION
>            "An event trap."
>    ::= { eventTraps 2 }
> 
> 
> -- Conformance information. It's needed, but you don't need to understand
> it too much. Just add new objects to one of the 2 groups.
> eventMIBCompliances
>               OBJECT IDENTIFIER ::= { eventMIB 3 }
> eventMIBGroups  OBJECT IDENTIFIER ::= { eventMIB 4 }
> 
> eventComplianceGroups MODULE-COMPLIANCE
>    STATUS  current
>    DESCRIPTION
>            "The compliance statement for this MIB module."
>    MODULE  -- this module
>        MANDATORY-GROUPS { trapGroup, objectGroup }
> 
>    ::= { eventMIBCompliances 1 }
> 
> -- If you add extra traps, they need to go in here.
> trapGroup NOTIFICATION-GROUP
>    NOTIFICATIONS { eventNotice }
>    STATUS        current
>    DESCRIPTION
>       "Basic event notifications."
>    ::= { eventMIBGroups 1 }
> 
> 
> -- If you add extra objects, they need to go in here.
> objectGroup OBJECT-GROUP
>        OBJECTS {eventName, eventCategory}
>           STATUS current
>           DESCRIPTION
>               "Grouped event parameters."
>           ::= { eventMIBGroups 2 }
> 
> END
>