Migrating Your SNMP DPI Subagent to Version 2.0

The information presented in this section must be taken as guidelines and not exact procedures. Your specific implementation will vary from the guidelines presented.

When you want to change your DPI 1.x based subagent code to the DPI Version 2.0 level use these guidelines for the required actions and the recommended actions.

Required Actions

• Add a mkDPIopen() call and send the created packet to the agent. This opens your "DPI connection" with the agent. Wait for the response and ensure that the open is accepted. You need to pass a subagent ID (Object Identifier) which must be a unique ASN.1 OID.

  See The mkDPIopen() Function for more information.

• Change your mkDPIregister() calls and pass the parameters according to the new function prototype. You must also expect a RESPONSE to the REGISTER request.

  See The mkDPIregister() Function for more information.

• Change mkDPIset() and/or mkDPIlist() calls to the new mkDPIset() call. Basically all mkDPIset() calls are now of the DPI 1.1 mkDPIlist() form.

  See The mkDPIset() Function for more information.

• Change mkDPItrap() and mkDPItrape() calls to the new mkDPItrap() call. Basically all mkDPItrap() calls are now of the DPI 1.1 mkDPItrape() form.

  See The mkDPItrap() Function for more information.

• Add code to recognize DPI RESPONSE packets, which should be expected as a result of OPEN, REGISTER, UNREGISTER requests.

• Add code to expect and handle the DPI UNREGISTER packet from the agent. It may send such packets if an error occurs or if a higher priority subagent registers the same sub-tree as you have registered.

• Add code to unregister your sub-tree(s) and close the "DPI connection" when you want to terminate the subagent.

  See The mkDPIunregister() Function and The mkDPIclose() Function for more information.

• Change your code to use the new SNMP Version 2 error codes as defined in the snmp_dpi.h include file.

• Change your code that handles a GET request. It should return a varBind with SNMP_TYPE_noSuchObject value or SNMP_TYPE_noSuchInstance value instead of an error SNMP_ERROR_noSuchName if the object or the instance do not exist. This is not considered an error any more. Therefore, you should return an SNMP_ERROR_noError with an error index of zero.

• Change your code that handles a GETNEXT request. It should return a varBind with SNMP_TYPE_endOfMibView value instead of an error SNMP_ERROR_noSuchName if you reach the end of your MIB or sub-tree. This is not considered an error any more. Therefore, you should return an SNMP_ERROR_noError with an error index of zero.

• Change your code that handles SET requests to follow the two phase SET/COMMIT scheme as described in SET Processing.

  See the sample handling of SET/COMMIT/UNDO in Processing a SET/COMMIT/UNDO Request.

Recommended Actions

• Do not reference the object ID pointer (object_p) in the snmp_dpi_xxxx_packet structures anymore. Instead start using the group_p and instance_p pointers. The object_p pointer may be removed in a future version of the DPI API.

• Check Transport-Related DPI API Functions to see if you want to use those functions instead of using your own code for those functions.

• Consider using more than 1 varBind per DPI packet. You can specify this on the REGISTER request. You must then be prepared to handle multiple varBinds per DPI packet. The varBinds are chained via the various snmp_dpi_xxxx_packet structures.

  See The mkDPIregister() Function for more information.

• Consider specifying a time out when you issue a DPI OPEN or DPI REGISTER.

  See The mkDPIopen() Function and The mkDPIregister() Function for more information.