SnmpExtensionTrap

The Microsoft SNMP service calls the SnmpExtensionTrap function to retrieve information the service needs to generate traps for the SNMP extension agent. The service calls this function only after the extension agent sets the trap event handle to the signaled state during a call to the SnmpExtensionInit function. The SnmpExtensionTrap function is an element of the SNMP Extension Agent API.

BOOL SnmpExtensionTrap(
  AsnObjectIdentifier *pEnterpriseOid,  // generating enterprise
  AsnInteger32 *pGenericTrapId,         // generating trap type
  AsnInteger32 *pSpecificTrapId,        // enterprise-specific type
  AsnTimeticks *pTimeStamp,             // time stamp
  SnmpVarBindList *pVarBindList         // variable bindings
);

Parameters

pEnterpriseOid

[out] Pointer to an AsnObjectIdentifier structure to receive the object identifier of the enterprise that generated the trap. The SNMP service does not free the memory for this variable.

pGenericTrapId

[out] Pointer to a variable to receive an indication of the generic trap. This parameter can be one of the following values.

Value	Meaning
SNMP_GENERICTRAP_COLDSTART	The agent is initializing protocol entities on the managed mode. It may alter objects in its view.
SNMP_GENERICTRAP_WARMSTART	The agent is re-initializing itself but will not alter objects within its view.
SNMP_GENERICTRAP_LINKDOWN	An attached interface has changed from the up state to the down state. The first variable identifies the interface.
SNMP_GENERICTRAP_LINKUP	An attached interface has changed from the down state to the up state. The first variable identifies the interface.
SNMP_GENERICTRAP_AUTHFAILURE	An SNMP entity has sent an SNMP message, but has falsely claimed to belong to a known community.
SNMP_GENERICTRAP_EGPNEIGHLOSS	An EGP peer has changed to the down state. The first variable identifies the IP address of the EGP peer.
SNMP_GENERICTRAP_ENTERSPECIFIC	Signals an extraordinary event that is identified in the pSpecificTrapId parameter.

pSpecificTrapId

[out] Pointer to a variable to receive an indication of the specific trap generated.

pTimeStamp

[out] Pointer to a variable to receive the time stamp. It is recommended that you initialize this parameter with the value returned by a call to the SnmpSvcGetUptime function.

pVarBindList

[out] Pointer to the variable bindings list. The extension agent must allocate the memory for this parameter. The SNMP service frees the memory with a call to the SnmpUtilVarBindListFree function.

Return Values

If the SnmpExtensionTrap function returns a trap, the return value is TRUE. The SNMP service repeatedly calls the function until it returns a value of FALSE. For additional information, see the following Remarks section.

Remarks

The SNMP service repeatedly calls the SnmpExtensionTrap function when the phSubagentTrapEvent event handle is set to the signaled state. This handle is passed back during the call to the SnmpExtensionInit entry point function. The SnmpExtensionTrap function must return TRUE to indicate that the parameters contain valid data for a single trap. The function must return FALSE to indicate that the parameters do not represent valid trap data, and to stop the service's repeated calls.

Note that after the SNMP service sends a trap, it frees the memory associated with the variable binding list.

It is important to note that earlier documentation stated that the extension agent should dynamically allocate memory for the enterprise object identifier because the SNMP service would attempt to release the memory after sending a trap. The service will not release the memory associated with the enterprise object identifier. It is recommended that you return a pointer to a static AsnObjectIdentifier structure instead.

Requirements

  Windows NT/2000: Requires Windows NT 3.1 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Declared in Snmp.h.

See Also

Simple Network Management Protocol (SNMP) Overview, SNMP Functions, SetEvent, SnmpUtilMemAlloc, SnmpUtilVarBindListFree, SnmpVarBindList, SnmpSvcGetUptime, SnmpExtensionInit