如何在MIB树中添加变量？

Question

这是我从http://snmplabs.com/pysnmp/examples/v3arch/asyncore/agent/cmdrsp/agent-side-mib-implementations.html获得的示例代码在这里，他们给出了“不同上下文名称下的多个MIB树”的示例程序。

from pysnmp.entity import engine, config
from pysnmp.entity.rfc3413 import cmdrsp, context
from pysnmp.carrier.asyncore.dgram import udp
from pysnmp.smi import instrum, builder
from pysnmp.proto.api import v2c

# Create SNMP engine
snmpEngine = engine.SnmpEngine()

# Transport setup

# UDP over IPv4
config.addTransport(
    snmpEngine,
    udp.domainName,
    udp.UdpTransport().openServerMode(('127.0.0.1', 161))
)

# SNMPv3/USM setup

# user: usr-md5-none, auth: MD5, priv NONE
config.addV3User(
    snmpEngine, 'usr-md5-none',
    config.usmHMACMD5AuthProtocol, 'authkey1'
)

# Allow full MIB access for each user at VACM
config.addVacmUser(snmpEngine, 3, 'usr-md5-none', 'authNoPriv', (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1))

# Create an SNMP context with default ContextEngineId (same as SNMP engine ID)
snmpContext = context.SnmpContext(snmpEngine)

# Create multiple independent trees of MIB managed objects (empty so far)
mibTreeA = instrum.MibInstrumController(builder.MibBuilder())
mibTreeB = instrum.MibInstrumController(builder.MibBuilder())

# Register MIB trees at distinct SNMP Context names
snmpContext.registerContextName(v2c.OctetString('context-a'), mibTreeA)
snmpContext.registerContextName(v2c.OctetString('context-b'), mibTreeB)

# Register SNMP Applications at the SNMP engine for particular SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.SetCommandResponder(snmpEngine, snmpContext)
cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

# Register an imaginary never-ending job to keep I/O dispatcher running forever
snmpEngine.transportDispatcher.jobStarted(1)

# Run I/O dispatcher which would receive queries and send responses
try:
    snmpEngine.transportDispatcher.runDispatcher()

except:
    snmpEngine.transportDispatcher.closeDispatcher()
    raise

我在下面的snmp walk中尝试了它

snmpwalk -v3 -u usr-md5-none -l authNoPriv -A authkey1 -n context-a 127.0.0.1 .1.3.6

我正在得到

SNMPv2-SMI::dod = No more variables left in this MIB View (It is past the end of the MIB tree)

我知道这是由于MIB树为空而发生的。但是如何向其中添加数据？

Answer 1

要添加或覆盖正常运行的MIB树的OID，您可以将以下代码添加到您提供的代码示例中：

...
mibBuilder = snmpContext.getMibInstrum().getMibBuilder()

MibScalar, MibScalarInstance = mibBuilder.importSymbols(
    'SNMPv2-SMI', 'MibScalar', 'MibScalarInstance'
)

class MyStaticMibScalarInstance(MibScalarInstance):
    def getValue(self, name, idx):
        currentDT = datetime.datetime.now()
        return self.getSyntax().clone(
            'Hello World! It\'s currently: ' + str(currentDT)
        )

mibBuilder.exportSymbols(
    '__MY_MIB', MibScalar((1, 3, 6, 1, 2, 1, 1, 1), v2c.OctetString()),
    MyStaticMibScalarInstance((1, 3, 6, 1, 2, 1, 1, 1), (0,), v2c.OctetString())
)

# Register SNMP Applications at the SNMP engine for particular SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
...

# snmpwalk -v3 -u usr-md5-none -l authNoPriv -A authkey1 127.0.0.1 .1.3.6
iso.3.6.1.2.1.1.1.0 = STRING: "Hello World! It's currently: 2019-11-18 16:02:43.796005"
iso.3.6.1.2.1.1.2.0 = OID: iso.3.6.1.4.1.20408
iso.3.6.1.2.1.1.3.0 = Timeticks: (494) 0:00:04.94
iso.3.6.1.2.1.1.4.0 = ""
iso.3.6.1.2.1.1.5.0 = ""
iso.3.6.1.2.1.1.6.0 = ""
iso.3.6.1.2.1.1.7.0 = INTEGER: 0
iso.3.6.1.2.1.1.8.0 = Timeticks: (0) 0:00:00.00
iso.3.6.1.2.1.11.1.0 = Counter32: 13
iso.3.6.1.2.1.11.2.0 = Counter32: 0
iso.3.6.1.2.1.11.3.0 = Counter32: 0
iso.3.6.1.2.1.11.4.0 = Counter32: 0
iso.3.6.1.2.1.11.5.0 = Counter32: 0
iso.3.6.1.2.1.11.6.0 = Counter32: 0
iso.3.6.1.2.1.11.8.0 = Counter32: 0
iso.3.6.1.2.1.11.9.0 = Counter32: 0

如果确实需要第二个上下文和独立的树，则可以创建一个通用控制器来检查并发送您想要的任何东西。

# Create an SNMP context with default ContextEngineId (same as SNMP engine ID)
snmpContext = context.SnmpContext(snmpEngine)

# Very basic Management Instrumentation Controller without
# any Managed Objects attached. It supports only GET's and
# modded to react to a target OID, otherwise
# always echos request var-binds in response.
class EchoMibInstrumController(instrum.AbstractMibInstrumController):
    def readVars(self, varBinds, acInfo=(None, None)):
        retItem = []
        for ov in varBinds:
            if str(ov[0]) == '1.3.6.1.2.1.1.1.0':
                currentDT = datetime.datetime.now()
                retItem.extend([(ov[0], v2c.OctetString('Hello World! It\'s currently: %s' % str(currentDT)))])
            else:
                retItem.extend([(ov[0], v2c.OctetString('You queried OID %s' % ov[0]))])
        return retItem


# Create multiple independent trees of MIB managed objects (empty so far)
mibTreeA = EchoMibInstrumController()
mibTreeB = instrum.MibInstrumController(builder.MibBuilder())

# Register MIB trees at distinct SNMP Context names
snmpContext.registerContextName(v2c.OctetString('context-a'), mibTreeA)
snmpContext.registerContextName(v2c.OctetString('context-b'), mibTreeB)

snmpget -v3 -u usr-md5-none -l authNoPriv -A authkey1 -n context-a 127.0.0.1 .1.3.6.1.2.1.1.1.0

# snmpget -v3 -u usr-md5-none -l authNoPriv -A authkey1 127.0.0.1 .1.3.6.1.2.1.1.1.0
iso.3.6.1.2.1.1.1.0 = STRING: "PySNMP engine version 4.4.12, Python 3.5.2 (default, Jul  5 2016, 12:43:10)  [GCC 5.4.0 20160609]"

# snmpget -v3 -u usr-md5-none -l authNoPriv -A authkey1 -n context-a 127.0.0.1 .1.3.6.1.2.1.1.1.0
iso.3.6.1.2.1.1.1.0 = STRING: "Hello World! It's currently: 2019-11-18 15:56:26.598242"

# snmpget -v3 -u usr-md5-none -l authNoPriv -A authkey1 -n context-a 127.0.0.1 .1.3.6.1.2.1.1.2.0
iso.3.6.1.2.1.1.2.0 = STRING: "You queried OID 1.3.6.1.2.1.1.2.0"