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#
# Notification Receiver
#
# Receive SNMP TRAP/INFORM messages with the following options:
#
# * SNMPv1/SNMPv2c
# * with any SNMP community matching regexp '.*love.*'
# * over IPv4/UDP, listening at 127.0.0.1:162
# * print received data on stdout
#
# Either of the following Net-SNMP's commands will send notifications to this
# receiver:
#
# $ snmptrap -v1 -c rollover 127.0.0.1 1.3.6.1.4.1.20408.4.1.1.2 127.0.0.1 1 1 123 1.3.6.1.2.1.1.1.0 s test
# $ snmpinform -v2c -c glove 127.0.0.1 123 1.3.6.1.6.3.1.1.5.1
#
# The Notification Receiver below taps on v1/v2c SNMP security module
# to deliver certains values, normally internal to SNMP Engine, up to
# the context of user application.
#
# This script examines the value of CommunityName, as it came from peer SNMP
# Engine, and may modify it to match the only locally configured CommunityName
# 'public'. This effectively makes NotificationReceiver accepting messages with
# CommunityName's, not explicitly configured to local SNMP Engine.
#
from pysnmp.entity import engine, config
from pysnmp.carrier.asynsock.dgram import udp
from pysnmp.entity.rfc3413 import ntfrcv
from pysnmp.proto.api import v2c
import re
# Create SNMP engine with autogenernated engineID and pre-bound
# to socket transport dispatcher
snmpEngine = engine.SnmpEngine()
# Register a callback to be invoked at specified execution point of
# SNMP Engine and passed local variables at execution point's local scope.
# If at this execution point passed variables are modified, their new
# values will be propagated back and used by SNMP Engine for securityName
# selection.
def requestObserver(snmpEngine, execpoint, variables, cbCtx):
if re.match('.*love.*', str(variables['communityName'])):
print('Rewriting communityName \'%s\' from %s into \'public\'' % (variables['communityName'], ':'.join([str(x) for x in variables['transportInformation'][1]])))
variables['communityName'] = variables['communityName'].clone('public')
snmpEngine.observer.registerObserver(
requestObserver,
'rfc2576.processIncomingMsg:writable'
)
# Transport setup
# UDP over IPv4
config.addTransport(
snmpEngine,
udp.domainName,
udp.UdpTransport().openServerMode(('127.0.0.1', 162))
)
# SNMPv1/2c setup
# SecurityName <-> CommunityName mapping
config.addV1System(snmpEngine, 'my-area', 'public')
# Callback function for receiving notifications
def cbFun(snmpEngine, stateReference, contextEngineId, contextName,
varBinds, cbCtx):
print('Notification from ContextEngineId "%s", ContextName "%s"' % (
contextEngineId.prettyPrint(),
contextName.prettyPrint()
)
)
for name, val in varBinds:
print('%s = %s' % (name.prettyPrint(), val.prettyPrint()))
# Register SNMP Application at the SNMP engine
ntfrcv.NotificationReceiver(snmpEngine, cbFun)
snmpEngine.transportDispatcher.jobStarted(1) # this job would never finish
# Run I/O dispatcher which would receive queries and send confirmations
try:
snmpEngine.transportDispatcher.runDispatcher()
except:
snmpEngine.transportDispatcher.closeDispatcher()
raise
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