how to properly access varBinds returned in pysnmp traps

Question

I'm using python 2.7 and trying to capture SNMP traps using pysnmp. I am using the example from http://pysnmp.sourceforge.net/examples/current/v1arch/manager/ntfrcv/v2c-multiple-transports.html. I am having issues with getting the key/values from varBinds properly. The example code doesn't seem to work correctly for this.
Full code:

from pysnmp.carrier.asynsock.dispatch import AsynsockDispatcher
from pysnmp.carrier.asynsock.dgram import udp, udp6
from pyasn1.codec.ber import decoder
from pysnmp.proto import api

def cbFun(transportDispatcher, transportDomain, transportAddress, wholeMsg):
    while wholeMsg:
        msgVer = int(api.decodeMessageVersion(wholeMsg))
        if msgVer in api.protoModules:
            pMod = api.protoModules[msgVer]
        else:
            print('Unsupported SNMP version %s' % msgVer)
            return
        reqMsg, wholeMsg = decoder.decode(
            wholeMsg, asn1Spec=pMod.Message(),
            )
        print('Notification message from %s:%s: ' % (
            transportDomain, transportAddress
            )
        )
        reqPDU = pMod.apiMessage.getPDU(reqMsg)
        if reqPDU.isSameTypeWith(pMod.TrapPDU()):
            if msgVer == api.protoVersion1:
                j = pMod.apiTrapPDU.getEnterprise(reqPDU)
                print 'Enterprise: ({})'.format(str(j))

                print('Enterprise: %s' % (
                    pMod.apiTrapPDU.getEnterprise(reqPDU).prettyPrint()
                    )
                )
                print('Agent Address: %s' % (
                    pMod.apiTrapPDU.getAgentAddr(reqPDU).prettyPrint()
                    )
                )
                print('Generic Trap: %s' % (
                    pMod.apiTrapPDU.getGenericTrap(reqPDU).prettyPrint()
                    )
                )
                print('Specific Trap: %s' % (
                    pMod.apiTrapPDU.getSpecificTrap(reqPDU).prettyPrint()
                    )
                )
                print('Uptime: %s' % (
                    pMod.apiTrapPDU.getTimeStamp(reqPDU).prettyPrint()
                    )
                )
                varBinds = pMod.apiTrapPDU.getVarBindList(reqPDU)
            else:
                varBinds = pMod.apiPDU.getVarBindList(reqPDU)
            print("Var-binds List: ({})".format(str(varBinds)))

            print('Var-binds:')

            for oid, val in varBinds:
                #print('%s = %s' % (oid.prettyPrint(), val.prettyPrint()))
                print('  %s = %s' % (oid, val))


     return wholeMsg

transportDispatcher = AsynsockDispatcher()

transportDispatcher.registerRecvCbFun(cbFun)

# UDP/IPv4
# ip address changed for public posting
transportDispatcher.registerTransport(
    udp.domainName,     udp.UdpSocketTransport().openServerMode(('255.255.255.255', 162))
)

# UDP/IPv6
transportDispatcher.registerTransport(
udp6.domainName, udp6.Udp6SocketTransport().openServerMode(('::1', 162))
)

transportDispatcher.jobStarted(1)

try:
    # Dispatcher will never finish as job#1 never reaches zero
    transportDispatcher.runDispatcher()
except:
    transportDispatcher.closeDispatcher()
    raise

I do receive the trap, however, when it runs the code

print('Var-binds:')
for oid, val in varBinds:
    print('%s = %s' % (oid.prettyPrint(), val.prettyPrint()))

I receive AttributeError: 'str' object has not attribute 'prettyPrint'

Printing varBinds I get this:
(VarBindList().setComponents(VarBind().setComponents(ObjectName('1.3.6.1.2.1.1.3.0'), _BindValue().setComponents(ObjectSyntax().setComponents(None, ApplicationSyntax().setComponents(None, None, TimeTicks(86300650))))), VarBind().setComponents(ObjectName('1.3.6.1.6.3.1.1.4.1.0'), _BindValue().setComponents(ObjectSyntax().setComponents(SimpleSyntax().setComponents(None, None, ObjectIdentifier('1.3.6.1.4.1.1182.7386.1.1'))))), VarBind().setComponents(ObjectName('1.3.6.1.4.1.1182.7386.1.1.1.0'), _BindValue().setComponents(ObjectSyntax().setComponents(SimpleSyntax().setComponents(None, OctetString(hexValue='76616c207573622d636f6e6e2d73746174757320300a')))))))
If I change the code to

print('  %s = %s' % (oid, val))

I receive:

name =
name =
name =

How do I get the 3 names and values properly?

Ilya Etingof Ilya Etingof · Accepted Answer · 2017-08-31T21:59:31

You should use the .getVarBinds() method instead of the .getVarBindList() as noted in the latest documentation.

Alternatively, you can get the name-value pairs by requesting .items() of the varBinds e.g. varBinds.items().

Also note that there is a higher-level interface to the Notification Receiver application.

how to properly access varBinds returned in pysnmp traps

1 Answers