Wes: Created page with "{{MFDTutorial}} == MFD : ifXTable data access == The net-snmp access routine returns a container of ''netsnmp_interface_entry'' pointers that contain a snapshot of the ..."

2011-07-13T21:56:48Z

Created page with "{{MFDTutorial}} == MFD : ifXTable data access == The net-snmp access routine returns a container of ''netsnmp_interface_entry'' pointers that contain a snapshot of the ..."

New page

{{MFDTutorial}}

== MFD : ifXTable data access ==

The net-snmp access routine returns a container of
''netsnmp_interface_entry'' pointers that contain a snapshot
of the current data. However, as I mentioned before, this structure
does not contain all the data we need for ifXTable mib. For example,
the Linux kernel doesn't report the last time an interface was
changed. We have to periodically poll for the interfaces, and check
to see if each entry has changed. This polling has the added
benefit of always keeping our cache current.

=== Initialization ===

When the agent starts up and initializes, the
''ifXTable_init_data'' function will be called to allow us to
do any initilization for our data access functions. We don't have any,
so we'll just leave the function body empty.

The ''cached-container'' access method also has it's own
initilization routine, ''ifXTable_container_init''. This
allow you to use a custom container or tweak the cache parameters.
We'll cover both of these more advanced topic in a later tutorial.
For now, we'll leave the function body alone, using the default
container and default cache parameters.

=== Loading the cache ===

<table><tr><td width=20></td><td bgcolor=CCCCCC>
int
ifXTable_cache_load(netsnmp_container * container)
{<font color=blue>
netsnmp_container * ifcontainer;</font>
ifXTable_rowreq_ctx *rowreq_ctx;

DEBUGMSGTL(("verbose:ifXTable_cache_load", "called\n"));

/*
* TODO: update container
*
* loop over your data, allocate, set index, insert into the container
*/<font color=blue>
/*
* get a container of netsnmp_interface_entry pointers from
* the data access routine.
*/
ifcontainer =
netsnmp_access_interface_container_load(NULL,
NETSNMP_ACCESS_INTERFACE_INIT_NOFLAGS);

/*
* netsnmp_containers don't have efficient iterators yet, so use the
* foreach macro to get a callback for each interface.
*/
CONTAINER_FOR_EACH(ifcontainer,
(netsnmp_container_obj_func*)_check_interface_entry_for_updates,
container);

/*
* free the container. we've either claimed each ifentry, or released it,
* so the dal function doesn't need to clear the container.
*/
netsnmp_access_interface_container_free(ifcontainer,
NETSNMP_ACCESS_INTERFACE_FREE_DONT_CLEAR );
</font>
return MFD_SUCCESS;
}
while (1) {
/*
* TODO: check for end of data
*
* bail out if there is no more data
*/
if (ifXTable_OUT_OF_DATA())
break;

/*
* allocate an row context and set the index(es)
*/
rowreq_ctx = ifXTable_allocate_rowreq_ctx(NULL);
if (MFD_SUCCESS != ifXTable_indexes_set(rowreq_ctx, ifIndex)) {
snmp_log(LOG_ERR, "error setting index while loading "
"ifXTable cache.\n");
ifXTable_release_rowreq_ctx(rowreq_ctx);
continue;
}

/*
* TODO: populate data context
*/
/*
* TRANSIENT or semi-TRANSIENT data:
* can copy data in row_prep or here, depending on when you
* want to take the hit. Either copy the data now, or save
* any info needed and do it in row_prep.
*/

/*
* insert into table container
*/
CONTAINER_INSERT(container, rowreq_ctx);
}

return MFD_SUCCESS;
</td></tr>
</table>

MFD:ifXTable:Data Access - Revision history

Wes: Created page with "{{MFDTutorial}} == MFD : ifXTable data access == The net-snmp access routine returns a container of ''netsnmp_interface_entry'' pointers that contain a snapshot of the ..."