Generating traps

You may find it useful (or perhaps necessary) to have your SMUX peer generate traps based on the occurrence of certain types of events, such as specific errors. Implementing these enterpriseSpecific traps will involve the following steps:

1. Define the required enterpriseSpecific traps.

2. Make sure that all objects appearing in the VarBindList have been defined in the peer's MIB module. If they have not been, you will have to define them there now.

3. Write code that constructs a VarBindList and then issues a trap message.

1. First, the file smuxpeer.h must be edited to #define this enterpriseSpecific trap:

       #define    LINE_DEATH_ERROR_TRAP    1
   

2. When a serial line death occurs, this example trap will convey the board status and serial line number. Both of these values are already defined in the foo MIB under the object names boardStatus and serialLineNumber, so no further modification of the foo MIB module is necessary.

3. The following code should be put in the code path that is executed whenever the serial line dies:

   • Declare the variables used in constructing the trap message. In this example there are 2 VarBinds in the VarBind list, so the array size is set accordingly:

     OID             mibvar_oid_ptr[2];
     VarBindList    *constructed_varbindlist;
     

   • The statements below build the boardStatus VarBind. boardStatus is a single instance object, so its object name is appended with 0. The value of board status is held in the global variable boardStatus.

     mibvar_oid_ptr[0] = text2oid("boardStatus.0");
     trap_varbindlist = make_varbind(mibvar_oid_ptr[0], INTEGER_TYPE,
       0, (long) boardStatus, NULL, (OID) 0);
     

   • The statements below build the serialLineNumber VarBind and link it with the first VarBind; together, these 2 VarBinds make the VarBindList for this trap. In this example the serial line number is a multiple instance object so its object name is appended with the table index, which is the line number 2:

     mibvar_oid_ptr[1] = text2oid("serialLineNumber.2");
     trap_varbindlist->next = make_varbind(mibvar_oid_ptr[1],
       INTEGER_TYPE, 0, (long) 2, NULL, (OID) 0);
     

   • Finally, the statement below builds the trap message and forwards it to the agent. The agent then sends the trap message to the management station.

     if (smux_trap(trap_enterpriseSpecific, LINE_DEATH_ERROR_TRAP,
       (struct type_SNMP_VarBindList) trap_varbindlist) == NOTOK)
          LIB_ERROR2("smux_trap: %s [%s]", smux_error(smux_error),
            smux_info);