DLC FDDI Programming Interfaces

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The data link control (DLC) fiber distributed data interface (FDDI) conforms to generic data link control (GDLC) guidelines except where noted below.

Additional structures and definitions for DLC FDDI are found in the /usr/include/sys/fdlextcb.h file.

The following entry points are supported by DLC FDDI:

Note: The dlc prefix is replaced with the fdl prefix for the DLC FDDI device manager.
Item Description
fdlclose Fully compatible with the dlcclose GDLC interface.
fdlconfig Fully compatible with the dlcconfig GDLC interface. No initialization parameters are required.
fdlmpx Fully compatible with the dlcmpx GDLC interface.
fdlopen Fully compatible with the dlcopen GDLC interface.
fdlread Compatible with the dlcread GDLC interface with the following conditions:
  • The readx subroutines may have DLC FDDI data link header information prefixed to the information field (I-field) being passed to the application. This is optional based on the readx subroutine data link header length extension parameter in the gdl_io_ext structure.
  • If this field is nonzero, DLC FDDI copies the data link header and the I-field to user space, and sets the actual length of the data link header into the length field.
  • If the field is 0, no data link header information is copied to user space. See the DLC FDDI Frame Encapsulation (Figure 1) figure for more details.

Kernel receive packet function handlers always have the DLC FDDI data link header information within the communications memory buffer (mbuf), and can locate it by subtracting the length passed (in the gdl_io_ext structure) from the data offset field of the mbuf structure.
fdlselect Fully compatible with the dlcselect GDLC interface.
fdlwrite Compatible with the dlcwrite GDLC interface, with the exception that network data can only be written as an unnumbered information (UI) packet and must have the complete data link header prefixed to the data. DLC FDDI verifies that the local (source) service access point (SAP) is enabled and that the control byte is UI (0x03). See the DLC FDDI Frame Encapsulation figure (Figure 1) for more details.
fdlioctl Compatible with the dlcioctl GDLC interface. The following ioctl operations contain FDDI-specific conditions on GDLC operations: