[libsmi] Why don't BASETYPE values match RFC 2578?

14 May 2001


      I'm trying to map libsmi BASETYPE values to SNMP base types. RFC 2578
defines the base types as:
Integer32 <=> INTEGER
OctetString <=> OCTET STRING
ObjectIdentifier <=> OBJECT IDENTIFIER
IpAddress
Counter32
Gauge32
Unsigned32
TimeTicks
Opaque
Counter64
And that's it. These all map to unique BER encodings, and are thus the
only real types that can be conveyed across the wire. Yet, the libsmi
constants are these:
typedef enum SmiBasetype {
    SMI_BASETYPE_UNKNOWN                = 0,   
    SMI_BASETYPE_INTEGER32              = 1,   
    SMI_BASETYPE_OCTETSTRING            = 2,
    SMI_BASETYPE_OBJECTIDENTIFIER       = 3,
    SMI_BASETYPE_UNSIGNED32             = 4,
    SMI_BASETYPE_INTEGER64              = 5,   
    SMI_BASETYPE_UNSIGNED64             = 6,   
    SMI_BASETYPE_FLOAT32                = 7,   
    SMI_BASETYPE_FLOAT64                = 8,   
    SMI_BASETYPE_FLOAT128               = 9,   
    SMI_BASETYPE_ENUM                   = 10,
    SMI_BASETYPE_BITS                   = 11   
} SmiBasetype;
Libsmi adds some extra ones, and omits others. Here's my problem (by
way of example).
In RFC1271 (RMON MIB) there is a node like so:
bufferControlTurnOnTime OBJECT-TYPE
              SYNTAX TimeTicks
              ACCESS read-only
              STATUS mandatory
              DESCRIPTION
                  "The value of sysUpTime when this capture buffer was
                  first turned on."
              ::= { bufferControlEntry 11 }
Note that the SYNTAX clause is TimeTicks, which is an SNMP base type
with encoding [APPLICATION 3].
But libsmi returns this (using my Python wrapper):
Python> import SMI
Python> m =SMI.getModule("RFC1271-MIB")
Python> n = m.getNode("bufferControlTurnOnTime")
Python> print n.syntax 
Type:
           namednumbers = []
                   name = TimeTicks
                  units = None
            enumeration = None
                 ranges = None
                  value = <unknown>
               basetype = 4
                 format = None
              reference = None
            description = None
                   decl = 2
                 status = 0
The name is correctly shown as "TimeTicks", but the basetype is 4,
which means SMI_BASETYPE_UNSIGNED32, which implies a basetype of
Unsigned32 which has an encoding of [APPLICATION 2] (different from
the canonical TimeTicks). But then, the SmiBasetype C enumeration does
not even list TIMETICKS at all.
Or am I not using this libsmi correctly?
Could someone please explain this to me, and possibly give me a clue
as to how to map libsmi SYNTAX/SmiType values to canonical
SNMP/RFC2578 types? Thank you.
\|//
                           (O O)
-- --------------------oOOo~(_)~oOOo----------------------------------------
Keith Dart
mailto:kdart@kdart.com
http://www.kdart.com/
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