DLC8023 Programming Interfaces

AIX Version 4.3 Communications Programming Concepts

DLC8023 Programming Interfaces

The IEEE 802.3 Ethernet data link control (DLC8023) device manager conforms to generic data link control (GDLC) guidelines, except as follows:

Note: The dlc prefix is replaced with the e3l prefix for the DLC8023 device manager.

e3lclose	DLC8023 is fully compatible with the dlcclose GDLC interface.
e3lconfig	DLC8023 is fully compatible with the dlcconfig GDLC interface. No initialization parameters are required.
e3lmpx	DLC8023 is fully compatible with the dlcmpx GDLC interface.
e3lopen	DLC8023 is fully compatible with the dlcopen GDLC interface.
e3lread	DLC8023 is compatible with the dlcread GDLC interface, under the following conditions: The readx subroutines can have DLC8023 data link header information prefixed to the I-field. The data can be passed to the application in the user-defined readx subroutine data link header length extension parameter in the gdl_io_ext structure. If this field has a nonzero value, DLC8023 copies the data link header and the I-field to user space and sets the actual length of the data link header in the length field. If the field has a value of 0, no data link header information is copied. See the DLC8023 Frame Encapsulation figure for more details.

The following kernel receive packet function handlers always have the DLC8023 data link header information in the communications memory buffer (mbuf), and can locate this information by subtracting the length passed in the gdl_io_ext structure from the data offset field.

e3lselect

DLC8023 is fully compatible with the dlcselect GDLC interface.

e3lwrite

DLC8023 is compatible with the dlcwrite GDLC interface. The exceptions are that network data can only be written as an unnumbered information (UI) packet and must have the complete data link header prefixed. DLC8023 verifies that the local, or source, service access point (SAP) is enabled and that the control byte is UI (0x03). See the DLC8023 Frame Encapsulation for more details.

e3lioctl

DLC8023 is compatible with the dlcioctl GDLC interface, with conditions on the following operations:

The following sections describe these conditions.

DLC_ENABLE_SAP

The ioctl subroutine argument structure to enable a SAP (dlc_esap_arg) has the following specifics:

The grp_addr field is a 6-byte value as specified in the draft IEEE Standard 802.3 specifications. Octet grp_addr[0] specifies the most significant byte and octet grp_addr[5] specifies the least significant byte. Each octet of the address field is transmitted, least significant bit first. Group addresses sometimes are called multicast addresses.
An example of a group address follows:
```
0x0900_2B00_0004
```
Note: The DLC8023 device manager does not check whether a received packet was accepted by the adapter due to a preset network address or group address.
The max_ls (maximum link station) field cannot exceed 255 bytes.

The following common SAP flags are not supported:

ENCD	Indicates synchronous data link control (SDLC) serial encoding.
NTWK	Indicates a teleprocessing network type.
LINK	Indicates teleprocessing link type.
PHYC	Indicates a physical network call (teleprocessing).
ANSW	Indicates a teleprocessing autocall and autoanswer.

Group SAPs are not supported. Therefore the num_grp_saps (number of group SAPs) field must be set to 0.
The laddr_name (local address name) field and its associated length are used for name-discovery when the common SAP flag ADDR is set to 0. When resolve procedures are used (that is, the ADDR flag is set to 1), the DLC8023 device manager obtains the local network address from the device handler and not from the dlc_esap_arg structure.
The local_sap (local service access point) field can be set to any value except null SAP (0x00) or the name-discovery SAP (0xFC). Also, the low-order bit must be set to 0 (B`nnnnnnn0') to indicate an individual address.
No protocol-specific data area is required for the DLC8023 device manager to enable a SAP.

DLC_START_LS

The ioctl subroutine argument structure specifics to start a link station (dlc_sls_arg) are as follows:

These common link station flags are not supported:
STAT Indicates a station type for an SDLC.

NEGO Indicates a negotiable station type for an SDLC.
The raddr_name (remote address and name) field is used for outgoing calls when the DLC_SLS_LSVC common link station flag is active.
The maxif (maximum information field length) field can be set to any value greater than 0. See the DLC8023 frame encapsulation figure for the supported byte lengths. If a byte is set too large, DLC8023 adjusts it to a maximum of 1496 bytes.
The rcv_wind (receive window) field can be set to any value between 1 and 127 inclusive. The recommended value is 127.
The xmit_wind (transmit window) field can be set to any value between 1 and 127 inclusive. The recommended value is 26.
The rsap (remote SAP) field can be set to any value except null SAP (0x00) or the name-discovery SAP (0xFC). The low-order bit must be set to 0 (B`nnnnnnn0') to indicate an individual address.
The max_repoll field can be set to any value between 1 and 255 inclusive. The recommended value is 8.
The repoll_time field is defined in increments of 0.5 seconds and can be set to any value between 1 and 255, inclusive. The recommended value is 2, giving a time-out duration of 1 to 1.5 seconds.
The ack_time (acknowledgment time) field is defined in increments of 0.5 seconds and can be set to any value between 1 and 255, inclusive. The recommended value is 1, giving a time-out duration of 0.5 to 1 second.
The inact_time (inactivity time) field is defined in increments of 1 second and can be set to any value between 1 and 255, inclusive. The recommended value is 48, giving a time-out duration of 48 to 48.5 seconds.
The force_time (force halt time) field is defined in increments of 1 second and can be set to any value between 1 and 16383, inclusive. The recommended value is 120, giving a time-out duration of approximately 2 minutes.
No protocol-specific data area is required for the DLC8023 device manager to start a link station.

DLC_ALTER

The ioctl subroutine argument structure for altering a link station (dlc_alter_arg) has the following specifics:

These alter flags are not supported:
RTE Alter routing.

SM1, SM2 Set SDLC control mode.
A protocol-specific data area is not required for DLC8023 to alter a link station.

DLC_QUERY_SAP

The device driver-dependent data returned from DLC8023 for this ioctl operation is the ent_ndd_stats_t structure defined in the /usr/include/sys/cdli_entuser.h file.

DLC_QUERY_LS

No protocol-specific data area is supported by DLC8023 for this ioctl operation.

DLC_ENTER_SHOLD

The enter_short_hold option is not supported by the DLC8023 device manager.

DLC_EXIT_SHOLD

The exit_short_hold option is not supported by the DLC8023 device manager.

DLC_ADD_GROUP

The add_group, or multicast address, option is supported by the DLC8023 device manager. It is a six-byte value as described previously in the DLC_ENABLE_SAP (group address) ioctl operation.

DLC_ADD_FUNC_ADDR

The add_functional_address option is not supported by DLC8023.

DLC_DEL_FUNC_ADDR

The delete_functional_address option is not supported by DLC8023.

DLC_DEL_GRP

The delete group or multicast option is supported by the DLC8023 device manager. The address being removed must match an address that was added with a DLC_ENABLE_SAP or DLC_ADD_GRP ioctl operation.

IOCINFO

The returned ioctype variable is defined as a DD_DLC definition, and the subtype returned is DS_DLC8023.

STAT	Indicates a station type for an SDLC.
NEGO	Indicates a negotiable station type for an SDLC.

RTE	Alter routing.
SM1, SM2	Set SDLC control mode.