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/** @example delayed_instance.c
* This example implements the netSnmpExampleSleeper object.
*
* It demonstrates 2 things:
*
* - The instance helper, which is a way of registering an exact OID
* such that GENEXT requests are handled entirely by the helper.
*
* - how to implement objects which normally would block the agent as
* it waits for external events in such a way that the agent can
* continue responding to other requests while this implementation
* waits.
*
* - Added bonus: normally the nsTransactionTable is empty, since
* there aren't any outstanding requests generally. When accessed,
* this module will create some however. Try setting
* netSnmpExampleSleeper.0 to 10 and then accessing it (use
* "snmpget -t 15 ..." to access it), and then walk the
* nsTransactionTable from another shell to see that not only is
* the walk not blocked, but that the nsTransactionTable is not
* empty.
*
*/
#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>
#include <net-snmp/agent/net-snmp-agent-includes.h>
#include "delayed_instance.h"
static u_long delay_time = 1;
void
init_delayed_instance(void)
{
static oid my_delayed_oid[] =
{ 1, 3, 6, 1, 4, 1, 8072, 2, 1, 2, 0 };
/*
* delayed handler test
*/
netsnmp_handler_registration *my_test;
my_test =
netsnmp_create_handler_registration("delayed_instance_example",
delayed_instance_handler,
my_delayed_oid,
OID_LENGTH(my_delayed_oid),
HANDLER_CAN_RWRITE);
netsnmp_register_instance(my_test);
}
#define DELAYED_INSTANCE_SET_NAME "test_delayed"
int
delayed_instance_handler(netsnmp_mib_handler *handler,
netsnmp_handler_registration *reginfo,
netsnmp_agent_request_info *reqinfo,
netsnmp_request_info *requests)
{
DEBUGMSGTL(("delayed_instance", "Got request, mode = %d:\n",
reqinfo->mode));
switch (reqinfo->mode) {
/*
* here we merely mention that we'll answer this request
* later. we don't actually care about the mode type in this
* example, but for certain cases you may, so I'll leave in the
* otherwise useless switch and case statements
*/
default:
/*
* mark this variable as something that can't be handled now.
* We'll answer it later.
*/
requests->delegated = 1;
/*
* register an alarm to update the results at a later
* time. Normally, we might have to query something else
* (like an external request sent to a different network
* or system socket, etc), but for this example we'll do
* something really simply and just insert an alarm for a
* certain period of time
*/
snmp_alarm_register(delay_time, /* seconds */
0, /* dont repeat. */
return_delayed_response, /* the function
* to call */
/*
* here we create a "cache" of useful
* information that we'll want later
* on. This argument is passed back
* to us in the callback function for
* an alarm
*/
(void *)
netsnmp_create_delegated_cache(handler,
reginfo,
reqinfo,
requests,
NULL));
break;
}
return SNMP_ERR_NOERROR;
}
void
return_delayed_response(unsigned int clientreg, void *clientarg)
{
/*
* extract the cache from the passed argument
*/
netsnmp_delegated_cache *cache = (netsnmp_delegated_cache *) clientarg;
netsnmp_request_info *requests;
netsnmp_agent_request_info *reqinfo;
u_long *delay_time_cache = NULL;
/*
* here we double check that the cache we created earlier is still
* * valid. If not, the request timed out for some reason and we
* * don't need to keep processing things. Should never happen, but
* * this double checks.
*/
cache = netsnmp_handler_check_cache(cache);
if (!cache) {
snmp_log(LOG_ERR, "illegal call to return delayed response\n");
return;
}
/*
* re-establish the previous pointers we are used to having
*/
reqinfo = cache->reqinfo;
requests = cache->requests;
DEBUGMSGTL(("delayed_instance",
"continuing delayed request, mode = %d\n",
cache->reqinfo->mode));
/*
* mention that it's no longer delegated, and we've now answered
* the query (which we'll do down below).
*/
requests->delegated = 0;
switch (cache->reqinfo->mode) {
/*
* registering as an instance means we don't need to deal with
* getnext processing, so we don't handle it here at all.
*
* However, since the instance handler already reset the mode
* back to GETNEXT from the faked GET mode, we need to do the
* same thing in both cases. This should be fixed in future
* versions of net-snmp hopefully.
*/
case MODE_GET:
case MODE_GETNEXT:
/*
* return the currend delay time
*/
snmp_set_var_typed_value(cache->requests->requestvb,
ASN_INTEGER,
(u_char *) & delay_time,
sizeof(delay_time));
break;
case MODE_SET_RESERVE1:
/*
* check type
*/
if (requests->requestvb->type != ASN_INTEGER) {
/*
* not an integer. Bad dog, no bone.
*/
netsnmp_set_request_error(reqinfo, requests,
SNMP_ERR_WRONGTYPE);
/*
* we don't need the cache any longer
*/
netsnmp_free_delegated_cache(cache);
return;
}
break;
case MODE_SET_RESERVE2:
/*
* store old value for UNDO support in the future.
*/
memdup((u_char **) & delay_time_cache,
(u_char *) & delay_time, sizeof(delay_time));
/*
* malloc failed
*/
if (delay_time_cache == NULL) {
netsnmp_set_request_error(reqinfo, requests,
SNMP_ERR_RESOURCEUNAVAILABLE);
netsnmp_free_delegated_cache(cache);
return;
}
/*
* Add our temporary information to the request itself.
* This is then retrivable later. The free function
* passed auto-frees it when the request is later
* deleted.
*/
netsnmp_request_add_list_data(requests,
netsnmp_create_data_list
(DELAYED_INSTANCE_SET_NAME,
delay_time_cache, free));
break;
case MODE_SET_ACTION:
/*
* update current value
*/
delay_time = *(requests->requestvb->val.integer);
DEBUGMSGTL(("testhandler", "updated delay_time -> %d\n",
delay_time));
break;
case MODE_SET_UNDO:
/*
* ack, something somewhere failed. We reset back to the
* previously old value by extracting the previosuly
* stored information back out of the request
*/
delay_time =
*((u_long *) netsnmp_request_get_list_data(requests,
DELAYED_INSTANCE_SET_NAME));
break;
case MODE_SET_COMMIT:
case MODE_SET_FREE:
/*
* the only thing to do here is free the old memdup'ed
* value, but it's auto-freed by the datalist recovery, so
* we don't have anything to actually do here
*/
break;
}
/*
* free the information cache
*/
netsnmp_free_delegated_cache(cache);
}
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