Re: [pysnmp-users] Introspecting returned OID values from custom MIBs

[Ilya E. <il...@gl...>]

Hi Ian,

There's a TextualConvention class in pysnmp/smi/mibs/SNMPv2-TC.py which
is designed to be mixed into any standard SNMP type (Integer, OctetString 
etc) to customize value verification and interpretation in accordance with 
TEXTUAL-CONVENTION macro concent.

For example:

TruthValue ::= TEXTUAL-CONVENTION
     STATUS       current
     DESCRIPTION
             "Represents a boolean value."
     SYNTAX       INTEGER { true(1), false(2) }

gets converted into:

class TruthValue(Integer, TextualConvention):
     subtypeSpec = Integer.subtypeSpec + SingleValueConstraint(1, 2)
     namedValues = NamedValues(('true', 1), ('false', 2))

by libsmi2pysnmp or by hand.

You can see more examples on the above technique in 
pysnmp/smi/mibs/SNMPv2-TC.py.

If you convert custom manufacturer MIBs with pysnmp/build-pysnmp-mib 
script, the above magic would happen by its own.

Is that what you need?

-ilya

> I am working on a tool that consumes custom manufacturer MIBs with pysnmp.
>
> I am trying to find a way to return more useful python values from
> both the custom variable types defined in the MIBs provided by the
> manufacturer as well as the standard RFC 1902 SNMP variable types.
>
> A hypothetical example of what I have and what I need to get:
>
> Let there be a MIB file that defines a textual convention
> ManufacturerXInterfaceType that includes:
> - Integer(1) -> Ethernet
> - Integer(2) -> USB
> - Integer(3) -> Fibre
>
> Excerpt from the hypothetical MIB:
> ManufacturerXInterfaceType ::= TEXTUAL-CONVENTION
>  STATUS current
>  DESCRIPTION
>    " Define the hardware type of a given network interface. "
>  SYNTAX INTEGER
>    {
>    Ethernet(1)
>    USB(2)
>    Fibre(3)
>    }
>
> lanDeviceInterfaceType OBJECT-TYPE
>  SYNTAX        ManufacturerXInterfaceType
>  MAX-ACCESS    read-write
>  STATUS        current
>  DESCRIPTION
>    "The interface type of the current row "
>  ::= { lanDeviceTable 3}
>
> Here is a hypothetical class ManufacturerXInterfaceType that I can
> pass around my application that is more useful than just an rfc1902
> Integer.
>
> Pseudocode:
> class ManufacturerXInterfaceType:
>  def __str__(self):
>    if self.value == 1:
>      return 'Ethernet'
>    ellif self.value == 2:
>      return 'USB'
>    elif self.value == 3:
>      return 'Fibre'
>
> I would like to find a way of determining the textual
> convention/SYNTAX parameter type an OID is defined as using in the
> manufacturer MIBs.  In the following pseudocode example, I need some
> advice on writing the "magic_function_to_get_textual_convention"
> function.  Is there a method on the MibVariable to see what SYNTAX
> parameter used for an OID?
>
> cmdgen = rfc3413.oneliner.CommandGenerator()
> mibVar = cmdgen.MibVariable('modName', 'varName')
> errIndication, errStatus, errIndex, data =
> cmdgen.cmdGet(community_string, udp_transport, mibVar)
> textual_convention = magic_function_to_get_textual_convention(mibVar, data)
> if textual_convention == "ManufacturerXInterfaceType":
>  interface = ManufacturerXInterfaceType(data)
> elif textual_convention == "SomeOtherCustomType"
>  ...
>
> Pysnmp.entity.rfc3413.mibvar has a couple of convenience functions for
> determining additional information about an OID.  mibvar.mibNameToOid
> and mibvar.oidToMibName are quite useful, but I am looking for
> something similar that will give me additional information about the
> definition of the OID.