12.7.2.19 Determining Which Facilities are Present

Since facilities can be read only one at a time, the user needs a way to determine which facilities are present. Solstice X.25 provides the following mechanism for doing this.

The user can read a bit mask that has one bit reserved for each of the facilities described above. This is read as:

u_int     fmask;
 f.type = T_FACILITIES;
 error = ioctl(s, X25_GET_FACILITY, &f);
 fmask = f.f_facilities; 

The following mask bits are defined:

F_REVERSE_CHARGE    /* reverse charging */
 F_FAST_SELECT_TYPE  /* fast select */
 F_PACKET_SIZE       /* packet size */
 F_WINDOW_SIZE       /* window size */
 F_THROUGHPUT        /* throughput */
 F_MIN_THRU_CLASS    /* minimum throughput class */
 F_CUG               /* closed user group selection */
 F_RPOA              /* ROPA transit network */
 F_TR_DELAY          /* network transit delay */
 F_ETE_TR_DELAY      /* end to end transit delay */
 F_NUI               /* network user identification */
 F_CHARGE_REQ        /* charging information request */
 F_CHARGE_MU         /* charging information, monetary unit */
 F_CHARGE_SEG        /* charging information, segment */
 F_CHARGE_DUR        /* charging information, call duration */
 F_LINE_ADDR_MOD     /* called line address modified notification */
 F_CALL_REDIR        /* call redirection notification */
 F_EXPEDITED         /* expedited data negotiation */
 F_CALLED_AEF        /* called AEF */
 F_CALLING_AEF       /* calling AEF */
 F_PRIVATE           /* non-X.25 facilities */ 

For example, to determine if the Call Redirection facility has been received, the following segment of code could be used:

if ((fmask & F_CALL_REDIR) != 0) {
 /*
  * Read its value.
  */
 CALL_REDIR call_redir;
 f.type = T_CALL_REDIR;
 error = ioctl(s, X25_GET_FACILITY, &f);
 call_redir = f.f_call_redir;
 }