Re: [tkined] NetworkAddress problems

From: Juergen Schoenwaelder (
Date: Wed Jan 12 2000 - 12:03:11 MET

>>>>> Pete Flugstad writes:

Pete> I'm trying to run the scotty 2.1.10 as an snmp agent, and I'm
Pete> having problems with it responding to a GetNext in the atTable
Pete> of RFC1213. I've instantiated a number of rows in the table,
Pete> but when I try and walk the table, scotty spits out "unknown
Pete> asn1 type 0x15" when it tries to send out the NetworkAddress
Pete> field that is part of this table.
Pete> I see in EncodePDU that it doesn't handle the case of a
Pete> NetworkAddress encoding. From my reading of RFC 1155, this
Pete> should be a CHOICE encoding, right, with "internet(1).a.b.c.d".
Pete> I looked in the latest scotty 3.0.0 snapshot, and it looks like
Pete> the mapping for NetworkAddress was changed to IpAddress. This
Pete> doesn't seem right either?

Correct. The handling of NetworkAddress is broken. However,
NetworkAddress is only used in the atTable as far as the IETF is
concerned and the atTable is deprecated since 1991 so I am not sure
whether it really pays off to fix it.

The scotty 3.0.0 version allows you to implement the atTable by simply
changing the indexing structure to INDEX { atIfIndex, atDummy,
atNetAddress } where atDummy is a variable which always returns 1.
(Sure, this is still an ugly hack.)

Pete> Any suggestions on what the best way to fix this in 2.1.10 is?
Pete> Can I change the mapping from NetworkAddress to IpAddress, like
Pete> scotty 3.0.0 did? Or do I need to add a new case lable and
Pete> encode it properly (whatever that might be)? I'm still learning
Pete> ASN.1 and BER, so I'm at a loss.

The correct encoding would be the IPaddress encoding preceded by the
constant 1. (It is pretty straight forward to add this encoding to the
ASN.1/BER module but you also need to change things in other places.
Furthermore, the same problem will show up again if we switch to a new
SMI parser. So trying to avoid this rathole looks attractive. ;-)


Juergen Schoenwaelder      Technical University Braunschweig
<>  Dept. Operating Systems & Computer Networks
Phone: +49 531 391 3289    Bueltenweg 74/75, 38106 Braunschweig, Germany
Fax:   +49 531 391 5936    <URL:>

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