pysnmp 陷阱接收器中的 ValueConstraintError

Question

我正在使用此示例（取自 here）通过 pysnmp 接收 SNMP 陷阱：

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

transportDispatcher = AsynsockDispatcher()

transportDispatcher.registerRecvCbFun(cbFun)

# UDP/IPv4
transportDispatcher.registerTransport(
    udp.domainName, udp.UdpSocketTransport().openServerMode(('localhost', 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

并且对于某些陷阱，存在以下范围限制错误：

ValueConstraintError: ConstraintsIntersection(ConstraintsIntersection(), ValueRangeConstraint(0, 4294967295L)) failed at: "ValueRangeConstraint(0, 4294967295L) failed at: "-8249051"" at TimeTicks

有办法处理吗？

Answer 1

我在写这个问题时找到了答案 - FAQ 中描述了类似的情况。它似乎是供应商编码中的错误。对于 Counter 类型，有一个解决方案可以将负值转换为正值：

from pysnmp.proto import rfc1155, rfc1902, api
from pyasn1.codec.ber import encoder, decoder

# --- hack Counter type

def counterCloneHack(self, *args):
    if args and args[0] < 0:
        args = (0xffffffff+args[0]-1,) + args[1:]

    return self.__class__(*args)

rfc1155.Counter.clone = counterCloneHack
rfc1902.Counter32.clone = counterCloneHack

此 hack 也可以应用于 TimeTicks：

rfc1155.TimeTicks.clone = counterCloneHack

pysnmp 陷阱接收器中的 ValueConstraintError

ValueConstraintError in pysnmp trap receiver

python

pysnmp