Hi again,
Should I have posted this on the net-snmp-users list instead? I pondered that
originally but thought that the extra code locus information (in
ifTable_data_access.c) in the original note justified its inclusion here.
I'm still looking for a way to use the override mechanism for setting specific
ifXEntry trap enable values and to have this work for actual generation of
linkUp/linkDown traps when enabled. Is there anyone reading this list that
might be able to help me with this?
I forgot to mention originally that I'm using NetSNMP v5.7.3 on Linux.
Thanks,
-David
On Wednesday, August 07, 2019 11:15 AM, David Hauck <dav...@netacquire.com>
wrote:
> Hi,
>
> I'm trying to understand the difference between using an "override" for
> setting the IF-
> MIB::ifLinkUpDownTrapEnable.<x> object vs. a traditional set. I find that
> when these columns are set
> for an ifXEntry via the override mechanism in the agent's configuration file
> I do not ever see the
> corresponding effect (wrt linkUp/linkDown traps being issued):
>
> override -rw IF-MIB::ifLinkUpDownTrapEnable.4 integer 1
>
> However, if I remove the override and instead set the MIB object via a
> traditional set the
> corresponding effect (linkUp/linkDown traps being issued) does indeed occur:
>
> snmpset -v2c -c private -m ALL localhost IF-MIB::ifLinkUpDownTrapEnable.4 i 1
>
> Indeed, when I step through the agent in the debugger I see the key
> conditional where this behaviour
> changes. This is in _check_interface_entry_for_updates() in
> ifTable_data_access.c:
>
> ...
> if (oper_changed) {
> rowreq_ctx->data.ifLastChange = netsnmp_get_agent_uptime();
> #ifdef USING_IF_MIB_IFXTABLE_IFXTABLE_MODULE if
> (rowreq_ctx->data.ifLinkUpDownTrapEnable == 1) {
> if (rowreq_ctx->data.ifOperStatus == IFOPERSTATUS_UP) { ...
> The 'data.ifLinkUpDownTrapEnable' data member is always 0 in the override
> case, however, it is
> always the correct value (1 in the 'snmpset' case above) when 'snmpset' is
> used. Oddly, in the override
> case I do see an associated get ('snmpget') return the proper override
> (enable) value:
>
> snmpget -v2c -c private -m ALL localhost IF-MIB::ifLinkUpDownTrapEnable.4
> IF-MIB::ifLinkUpDownTrapEnable.4 = INTEGER: enabled(1)
>
> Moreover, whenever the override is used (note the use of the '-rw' token) I
> do not see any of the
> normal table access methods in ifXTable.c get called (i.e., no breaks in
> ifLinkUpDownTrapEnable_{get|set}). Why is this? And why does this have an
> effect on the ultimately
> relevant conditional in _check_interface_entry_for_updates()?
>
> My preference is to use the override mechanism so that I can persist (and
> ultimately prevent sets by
> removing the '-rw' token) the enable/disable state.
>
> Thanks for any insight anyone might be able to provide.
>
> Regards,
> -David
>
>
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