Subagent contexts and SNMP-COMMUNITY-MIB

[Frank Fock]

Mike,

Thanks again for the perfect and detailed bug report. In both
AgentXNode::get_request and AgentXNode::set_request
#ifdef _SNMPv3
  if (req->get_snmp_version() == version3) {
   req->get_pdu()->get_context_name(context);
  }
#endif

should be replaced by:

#ifdef _SNMPv3
   req->get_pdu()->get_context_name(context);
#endif

This should work, however I have to test it. I will upload an updated
AgentX++ version when I have verified this.

Best regards,
Frank

Mike Carr wrote:

> Frank,
>
> Thanks for putting me back on the right track for this but I think I've
> found another bug in the code...
>
> With an entry in the SNMP-COIMMUNITY-MIB for converting a community name
> into the appropriate context it appears that when the 'translation' is
> performed the version from the original request (v1 in my case) is being
> carried over into the request that is then added into the list of requests
> to be processed - see RequestList::receive where a new 'Request' object is
> created and then add_request is called.
>
> The consequence of this is that when the version of the request is checked
> to see if it's a v3 one and it's found not to be, then the context used to
> add the request to the pending list is empty because the actual context
> isn't copied over - see AgentXNode::get_request where the comparison
> req->get_snmp_version() == version3 is made and fails.
>
> Subsequently this empty context is used to create a pending AgentXPdu in the
> list of queued requests - see MasterAgentXMib::add_get_subrequest - and is
> then sent to the subagent - see MasterAgentXMib::send_pending_ax and then
> AgentX::send_agentx.
>
> When this gets received by the subagent it then fails since the context used
> in the comparison (which is empty) doesn't match the subagents context
> (which is 'subagent').
>
> Hopefully this makes sense and I've understood things correctly.  My only
> problem is that it's not clear how this should be corrected.  Should the
> version from the original request be translated into a v3 one in the first
> place so that the later comparison works?  If not have you any ideas?
>
> Thanks,
> Mike
>
> >From: Frank.Fock____t-online.de (Frank Fock)
> >To: Mike Carr <everythingsfree____hotmail.com>
> >CC: agentpp-dl at fock.de
> >Subject: Re: Subagent contexts and SNMP-COMMUNITY-MIB
> >Date: Tue, 19 Mar 2002 01:34:43 +0100
> >
> >Mike,
> >
> >You would query an agent configured with the SNMP-COMMUNITY-MIB
> >as you would query any SNMPv1/v2c agent. No special options! For each
> >context you want to query you will have to specify a different community.
> >Which communities are mapped to which contexts is configured in the
> >  SNMP-COMMUNITY-MIB. That's what it is for.
> >
> >Hope this helps.
> >
> >Best regards,
> >Frank