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"""

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    Requirements:

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        pysnmp

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        pysnmp-mibs

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"""

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import logging; log = logging.getLogger('pvl.snmp.snmp')

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import optparse

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from pysnmp.entity.rfc3413.oneliner import cmdgen as pysnmp

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import collections

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def options (parser) :

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    parser = optparse.OptionGroup(parser, "SNMP Agent")

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    parser.add_option('--snmp-community',

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            help="SNMPv2 read community")

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    return parser

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class SNMPError (Exception) :

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    pass

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class SNMPEngineError (SNMPError) :

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    """

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        Internal SNMP Engine error (?)

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    """

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class SNMPAgent (object) :

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    """

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        GET SNMP shit from a remote host.

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    """

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    SNMP_PORT = 161

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    snmp_cmdgen = pysnmp.CommandGenerator()

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    @classmethod

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    def apply (cls, options, host, community=None) :

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        port = cls.SNMP_PORT

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        if community is None :

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            community = options.snmp_community

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        if '@' in host :

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            community, host = host.split('@', 1)

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        if ':' in host :

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            host, port = host.rsplit(':', 1)

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        return cls(

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                pysnmp.CommunityData(community),

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                pysnmp.UdpTransportTarget((host, port))

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        )

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    def __init__ (self, security, transport) :

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        self.security = security

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        self.transport = transport

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    def get (self, *request) :

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        """

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            request = (

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                pysnmp.MibVariable('IF-MIB', 'ifInOctets', 1),

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            )

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        """

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        opts = dict(

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                lookupNames     = True,

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                lookupValues    = True,

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        )

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        try :

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            error, error_status, error_index, response = self.snmp_cmdgen.getCmd(self.security, self.transport,  *request, **opts)

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        except pysnmp.error.PySnmpError as ex :

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            raise SNMPEngineError(ex)

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        if error :

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            raise SNMPEngineError(error)

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        if error_status :

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            raise SNMPError(errorStatus.prettyPrint())

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        return response

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        #for name, value in response :

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        #    yield name.getMibSymbol(), value.prettyPrint()

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    def walk (self, *request) :

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        """

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            request = (

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                    pysnmp.MibVariable('IF-MIB', 'ifInOctets'),

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            )

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        """

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        opts = dict(

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                lookupNames     = True,

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                lookupValues    = True,

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        )

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        try :

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            error, error_status, error_index, responses = self.snmp_cmdgen.nextCmd(self.security, self.transport, *request, **opts)

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        except pysnmp.error.PySnmpError as ex :

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            raise SNMPEngineError(ex)

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        if error :

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            raise SNMPEngineError(error)

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        if error_status :

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            raise SNMPError(errorStatus.prettyPrint())

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        return responses

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        #for response in responses:

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        #    for name, value in response :

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        #        yield name.getMibSymbol(), value.prettyPrint()

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    def table (self, *columns) :

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        """

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            Given [oid] returns { idx: { oid: value } }

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        """

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        data = collections.defaultdict(dict)

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        for row in self.walk(*columns) :

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            log.debug("%s", row)

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            for column, (field, value) in zip(columns, row) :

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                mib, sym, idx = field.getMibSymbol()

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                log.debug("%s::%s[%s]: %s: %s", mib, sym, ', '.join(str(x) for x in idx), column, value)

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                data[idx][column] = value

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        return data.items()

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