Coding the UCOM and UMIB user exits

For an SNMP request to be accepted and processed by the z/TPF system, the SNMP manager must be verified. You must decide which SNMP managers are allowed to submit requests to your z/TPF system. The UCOM user exit validates the SNMP manager. You must add the necessary code to the UCOM user exit to determine which SNMP manager is allowed to view information in the z/TPF MIB database. The default system action is to reject all SNMP requests if the UCOM user exit is not coded.

The UMIB user exit is required for users who want to provide their own enterprise-specific MIB variables. For this, logic has to be added to the UMIB user exit to retrieve and then BER-encode enterprise-specific MIB variables. Input to the UMIB user exit is the unique object identifier of the variable being queried. The UMIB user exit returns the encoded object identifier of the variable returned, followed by the encoded value. Use the tpf_snmp_BER_encode C⁄C++ function to do this. See the z/TPF C/C++ Language Support User's Guide for more information about the tpf_snmp_BER_encode C⁄C++ function. See ISO 8825 Part 1: Basic Encoding Rules for more information about BER encoding. Go to https://www.iso.org/ to view ISO 8825.

For example, if object ID 1.3.6.1.4.1.20 is passed to the UMIB user exit and the value of the user MIB variable is found to be an integer of 20, the following must be returned:

06062B0601040114        020114

Encoded Object ID	   Encoded Value

The default coding for the UMIB user exit is to not acknowledge any MIB variable it is asked about. See z/TPF and z/TPFDF System Installation Support Reference for more information about the UCOM and UMIB user exits.