Developing SMUX peers for SNMP agents

Initialization of global data

Next, your peer will initialize the values of the MIB objects and the MIB database used by the peer. You will need to make more modifications to foomib.c to accomplish this.

The initializing routine init_foo() is executed when the peer first starts running. It is only for the foo MIB module. init_foo() has two primary functions: it initializes the values of the MIB objects and it initializes the MIB data structures used by the SMUX peer.

For each MIB module, make one of the following functions of name init_foo(), replacing the string ``foo'' with the identifying string you chose for your peer. The following example is for the foo MIB module:

    int
    init_foo()
    {

Next, initialize the values of the MIB objects. Initialize the value of each single instance leaf object and each instance of variables in tables.

NOTE: This initialization is application dependent. In this example SMUX peer the data is artificial and hard-coded; in a ``real life'' peer these variables will be collected from a device or file upon initialization, or dynamically on an ``as needed'' basis.

For each single instance variable initialize the value. If the object has an access of read-write set the ``new_name'' variable to a null value.

    productName = "Foo Serial I/O Board";
    boardStatus = ENABLED;
    new_boardStatus = 0;
    exampleIpAddr.s_addr = 0;
    newflag_exampleIpAddr = 0;
    exampleObjectID = make_obj_id_from_dot(DEFAULT_EXAMPLEOBJECTID);
    new_exampleObjectID = NULLOID;
    numberLines = 32;

Now, for each table in the MIB module, add a for() loop. This example is for the serialLineTable, which has numberLines rows:

   for (i = 0; i < numberLines; i++) {

For every object in the table, add an assignment statement to the for() loop that initializes the variable to a legal value. A ``real world'' SMUX peer would probably read these start-up or default values from the device being managed or from a configuration file.

        serialLineTable[i].serialLineNumber = i + 1;

You should also add an assignment statement to set the new pending value to null.

        serialLineTable[i].new_serialLineBaudRate = 0;

Next, initialize the MIB database used by the SMUX peer. For every leaf object in the MIB module, add an ``if'' statement as in the following examples. The ot_getfnx pointer points to the function used to process the GetRequest operation for this object. The ot_setfnx pointer points to the function used to process the SetRequest operation for this object. Objects that have an access of read-only have an ot_setfnx pointer that points to null. The ot_info is the last octet in the object ID as specified in the #define above.

NOTE: Throughout the following source code examples, many functions are referred to. The main ones are:

text2obj() - returns a pointer to the object's textual name (see smux_util(SLIB)).
o_string() - binds the name and the value of an object with syntax OctetString (see octetstring(SLIB)).
o_specific() - binds the name and the value of an object with syntax OID (see oid(SLIB)).
o_integer() - binds the name and the value of an object with syntax Integer (see smux_util(SLIB)).
the variable os - object syntax.
the variable ot - object type.

For more information on these or any other functions referenced in this chapter, please refer to that function's reference manual page, or smux_util(SLIB).

       if (ot = text2obj("productName")) {
           ot->ot_getfnx = get_single_instance;
           ot->ot_info = (caddr_t) PRODUCTNAME;
       }
       if (ot = text2obj("boardStatus")) {
           ot->ot_getfnx = get_single_instance;
           ot->ot_setfnx = set_single_instance;
           ot->ot_info = (caddr_t) BOARDSTATUS;
       }
       if (ot = text2obj("exampleIpAddr")) {
           ot->ot_getfnx = get_single_instance;
           ot->ot_setfnx = set_single_instance;
           ot->ot_info = (caddr_t) EXAMPLEIPADDR;
       }
       if (ot = text2obj("exampleObjectID")) {
           ot->ot_getfnx = get_single_instance;
           ot->ot_setfnx = set_single_instance;
           ot->ot_info = (caddr_t) EXAMPLEOBJECTID;
       }
       if (ot = text2obj("numberLines")) {
           ot->ot_getfnx = get_single_instance;
           ot->ot_info = (caddr_t) NUMBERLINES;
       }
       if (ot = text2obj("serialLineNumber")) {
           ot->ot_getfnx = get_serialLineTable;
           ot->ot_info = (caddr_t) SERIALLINENUMBER;
       }
       if (ot = text2obj("serialLineBaudRate")) {
           ot->ot_getfnx = get_serialLineTable;
           ot->ot_setfnx = set_serialLineTable;
           ot->ot_info = (caddr_t) SERIALLINEBAUDRATE;
       }
       if (ot = text2obj("serialLineTermLocation")) {
           ot->ot_getfnx = get_serialLineTable;
           ot->ot_setfnx = set_serialLineTable;
           ot->ot_info = (caddr_t) SERIALLINETERMLOCATION;
       }