[AGENT++] Authoritative EngineID Cached by Snmp++ ??

[Jochen Katz]

Hi,

> I noticed that the autoritative engineID is being cached by snmp++

yes, these are chached, as otherwise full discovery (three requests) has
to be made for each auth/priv request.

> due to which snmpv3 queries are failing ?

Caching only has problems if the eingineID of the agent changes. And
this SHOULD NOT happen all the time.

> Is there a way to clear the cache ?

Yes v3MP:reset_engine_id_table(), but the USM still has tables with
users and engine boot times (but these don't prevent discovery of the
new engine id).

> Now lets say the engineID and the user on the agent changes and the manager
> sets up another user with no engineID should not the snmp++ discover the
> newEngineID.

As written above, the authoritative engine ids should not change every
few hours.

I don't think that snmp++ should remove cached engine ids automatically,
but I could add a method like v3MP::remove_from_engine_id_table(OctetStr
&engineID, const OctetStr &host, int port). So after the application
receives a unknown engine id report, it can either decide to display a
warning message to the user or to remove the engine id and try the
request again. New functions to remove engine ids from USM will also be
added to snmp++.

Regards,
  Jochen