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"""

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    Requirements:

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        memoized-property

     4

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    Setup:

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        ./opt/bin/build-pysnmp-mib -o usr/mibs/Q-BRIDGE-MIB.py etc/mibs/rfc2674_q.mib

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     8

    Run:

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        PYSNMP_MIB_DIRS=usr/mibs/ ./opt/bin/python ...

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    SNMP:

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        Q-BRIDGE-MIB::dot1qVlanCurrentTable

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"""

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from pvl.snmp import snmp

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from pvl.snmp.snmp import pysnmp

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from memoized_property import memoized_property

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

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DOT1Q_NUM_VLANS = pysnmp.MibVariable('Q-BRIDGE-MIB', 'dot1qNumVlans')

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DOT1Q_VLAN_CURRENT_EGRESS_PORTS = pysnmp.MibVariable('Q-BRIDGE-MIB', 'dot1qVlanCurrentEgressPorts')

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DOT1Q_VLAN_CURRENT_UNTAGGED_PORTS = pysnmp.MibVariable('Q-BRIDGE-MIB', 'dot1qVlanCurrentUntaggedPorts')

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DOT1Q_VLAN_STATIC_NAME = pysnmp.MibVariable('Q-BRIDGE-MIB', 'dot1qVlanStaticName')

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def portlist (value) :

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    r"""

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        Unpack a OctetString bitmask into bit offsets.

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        >>> list(portlist('\x80'))

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        [1]

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        >>> list(portlist('\x01'))

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        [8]

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    """

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    for octet_idx, byte in enumerate(value) :

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        octet = ord(byte)

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        for bit_idx in xrange(0, 8) :

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            if octet & (1 << (7 - bit_idx)) :

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                yield octet_idx * 8 + bit_idx + 1

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class VLANAgent (snmp.SNMPAgent) :

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    """

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        Query VLAN configuration.

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    """

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    @memoized_property

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    def count (self) :

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        for name, value in self.get(DOT1Q_NUM_VLANS) :

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            # XXX: ????

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            if value.tagSet == pysnmp.rfc1905.NoSuchInstance.tagSet :

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                continue

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            return int(value)

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    def names (self) :

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        """

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                (vlan, name)

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        """

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        for idx, data in self.table(DOT1Q_VLAN_STATIC_NAME) :

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            vlan, = idx

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            yield int(vlan), str(data[DOT1Q_VLAN_STATIC_NAME])

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    def vlan_ports (self) :

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        """

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            Get per-vlan port configs.

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                (vlan, (tagged, untagged))

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        """

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        for idx, data in self.table(DOT1Q_VLAN_CURRENT_EGRESS_PORTS, DOT1Q_VLAN_CURRENT_UNTAGGED_PORTS) :

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            time, vlan = idx

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            egress = set(portlist(data[DOT1Q_VLAN_CURRENT_EGRESS_PORTS]))

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            untagged = set(portlist(data[DOT1Q_VLAN_CURRENT_UNTAGGED_PORTS]))

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            tagged = egress - untagged

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            yield int(vlan), (tagged, untagged)

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if __name__ == '__main__':

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    import doctest

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    doctest.testmod()