Re: [tkined] SNMPv3 support

From: Juergen Schoenwaelder (
Date: Fri Dec 08 2000 - 23:15:06 MET

>>>>> Dunford, Martin writes:

Martin> I had one other question re. SNMPv3. Does it do auto
Martin> discovery of engineID, engineBoots, engineTime, contextID
Martin> etc.? The tnmnSnmp structure holds all that info and I did
Martin> notice the 'session' recording it in tnmSnmpRecv.c. But using
Martin> a sniffer (the GNU 'Ethereal' sniffer decodes SNMPv3 pretty
Martin> well) subsequent packets don't seem to contain the correct
Martin> info. I realize all these are configurable from the command
Martin> line but sometimes it's a big advanatge to be able to auto
Martin> discove them from the agent.

The answer is yes and no. Tnm records the values but does not use it
in a retry since it stores the BER encoded message for retries and has
currently not all information available to reencode it. So if you do a
second get or getnext, then the discovered values should be used.

Martin> I think engineID is best a hex number. I tried using
Martin> 0x80000... style input. Code does do a

Martin> engineID = Tcl_GetStringFromObj(session->engineID,
Martin> &engineIDLength);

Martin> and then proceeds to insert this as ASCII string into the
Martin> packet. I am a relative Tcl API novice so maybe there is easy
Martin> solution to this I missed. But thanks for all your help.

You can use the "binary" command to construct any binary value and
pass it as part of the engineID option. Again, my design decision to
pass this in binary might be wrong. If we agree that this should be
changed, then I would propose to use the OctetString notation (such
as 80:00:...


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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