void * muxBind
    (
    char * pName,             /* interface name, for example, ln, ei,... */
    int    unit,              /* unit number */
    BOOL (* stackRcvRtn) (void* , long, M_BLK_ID, LL_HDR_INFO * , void* ),
                              /* receive function to be called. */
    STATUS (* stackShutdownRtn) (void* , void* ),
                              /* routine to call to shutdown the stack */
    STATUS (* stackTxRestartRtn) (void* , void* ),
                              /* routine to tell the stack it can transmit */
    void (* stackErrorRtn) (END_OBJ* , END_ERR* , void* ),
                              /* routine to call on an error. */
    long   type,              /* protocol type from RFC1700 and many */
                              /* other sources (for example, 0x800 is IP) */ 
    char * pProtoName,        /* string name for protocol */
    void * pSpare             /* per protocol spare pointer */
    )
stackRcvRtn，stackShutdownRtn，stackTxRestartRtn，stackErrorRtn函数该怎样写啊？