v4.4.5 fails to parse a BIT value

[muxout]

Upgrading from 4.4.4 to 4.4.5 has introduced a bug for us. For example this BITS value in CISCO-WAN-3G-MIB has now become an OctetString instead of Bits:

c3gConnectionStatusChangedNotifFlag OBJECT-TYPE
    SYNTAX          BITS {
                        unknown(0),
                        error(1),
                        connecting(2),
                        dormant(3),
                        connected(4),
                        disconnected(5),
                        idle(6),
                        active(7),
                        inactive(8)
                    }
    MAX-ACCESS      read-write
    STATUS          current
    DESCRIPTION
        "This object is the flag bitmap to control the generation of
        notification c3gConnectionStatusChangedNotif.  e.g. setting bit
        0 (error(0)) to 1 and bit 4 (disconnected(4)) to 1 will cause
        the notification c3gConnectionStatusChangedNotif to be
        generated when object c3gConnetionStatus changes the status to
        error or disconnected.  The default value of this object is
        '00'H."
    ::= { c3gWanCommonEntry 24 }

Rolling back to 4.4.4 resolved the problem

[etingof]

Thank you for raising this! And sorry for the regression!

If you got a simple reproducer handy, that would be awesome. If not - no worries, I will try to come up with one.

[muxout]

Sorry, our code was masking an error.

This will reproduce the error with a compatible Cisco device:

import pysnmp
import pysnmp.hlapi

target = pysnmp.hlapi.UdpTransportTarget(('cisco-router.lab', 161), timeout=10)
community_data = pysnmp.hlapi.CommunityData('public')
engine = pysnmp.hlapi.SnmpEngine()
context = pysnmp.hlapi.ContextData()

mib_builder = engine.getMibBuilder()
pysnmp.smi.compiler.addMibCompiler(mib_builder, sources=['file:///usr/share/snmp/mibs/'])
mib_builder.loadModule('CISCO-WAN-3G-MIB')
mib_view = pysnmp.smi.view.MibViewController(mib_builder)

oi = pysnmp.hlapi.ObjectIdentity('CISCO-WAN-3G-MIB', 'c3gConnectionStatusChangedNotifFlag', 10)
ot = pysnmp.hlapi.ObjectType(oi).resolveWithMib(mib_view)

results = pysnmp.hlapi.getCmd(engine, community_data, target, context, lookupMib=False, *[ot])

for (errindic, errstat, errindex, binds) in results:
    for bind in binds:
        oid = bind[0]
        value = bind[1]
        oid, value = pysnmp.hlapi.ObjectType(pysnmp.hlapi.ObjectIdentity(oid), value).resolveWithMib(mib_view)
        print(oid, type(value))

In 4.4.5 the above produces this error pysnmp.smi.error.SmiError: MIB object 'CISCO-WAN-3G-MIB::c3gConnectionStatusChangedNotifFlag.10' having type 'Bits' failed to cast value <OctetString value object at 0x7f0490de8210 subtypeSpec <ConstraintsIntersection object at 0x7f04959a7710 consts <ValueSizeConstraint object at 0x7f04959a76d0 consts 0, 65535>> tagSet <TagSet object at 0x7f049730efd0 tags 0:0:4> encoding iso-8859-1 payload [0xff80]>: Duplicate name dormantcaused by <class 'pyasn1.error.PyAsn1Error'>: Duplicate name dormant

In 4.4.4 it works as expected:

(ObjectIdentity(<ObjectName value object at 0x7f3ff35b4250 tagSet <TagSet object at 0x7f3ff7dd5510 tags 0:0:6> payload [1.3.6.1.4.1.9.9.661.1.1.1.24.10]>), <class 'pysnmp.proto.rfc1902.Bits'>)

[etingof]

Both master and release-4.4.6 branches should have this issue fixed.

[thomasgoirand]

Hi etingof,

Coud you please release 4.4.6, so that we have a new release with the fix?

Cheers,
Thomas Goirand (zigo)

[etingof]

Before I release, just wanted to double-check - does it work for you?

[vincentbernat]

Applying patch 74434d7 on top of 4.4.5 fixes the issue.

[etingof]

jfyi: pysnmp 4.4.6 with this fix has been released