DLCETHER Programming Interfaces

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The Standard Ethernet data link control (DLCETHER) conforms to the generic data link control (GDLC) guidelines except where noted below.

Note: The dlc prefix is replaced with the edl prefix for the DLCETHER device manager.
Item Description
edlclose DLCETHER is fully compatible with the dlcclose GDLC interface.
edlconfig DLCETHER is fully compatible with the dlcconfig GDLC interface. No initialization parameters are required.
edlmpx DLCETHER is fully compatible with the dlcmpx GDLC interface.
edlopen DLCETHER is fully compatible with the dlcopen GDLC interface.
edlread DLCETHER is compatible with the dlcread GDLC interface with the following conditions:
  • The readx subroutines can have DLCETHER data link header information prefixed to the 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, DLCETHER 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 DLCETHER Frame Encapsulation figure (Figure 1) for more details.

The following kernel receive packet subroutines always have the DLCETHER 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.

Item Description
edlselect DLCETHER is fully compatible with the dlcselect GDLC interface.
edlwrite DLCETHER is 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. DLCETHER verifies that the local (source) service access point (SAP) is enabled and that the control byte is UI (0x03). See the DLCETHER Frame Encapsulation figure (Figure 1).
edlioctl DLCETHER is compatible with the dlcioctl GDLC interface with conditions on these operations (described in the following sections):