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man pages section 4: Device and Network Interfaces

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Updated: Wednesday, July 27, 2022



llc1 - Logical Link Control Protocol Class 1 Driver


#include <sys/stropts.h> 
#include <sys/ethernet.h> 
#include <sys/dlpi.h> 
#include <sys/llc1.h> 


The llc1 driver is a multi-threaded, loadable, clonable, STREAMS multiplexing driver supporting the connectionless Data Link Provider Interface, dlpi(4P), implementing IEEE 802.2 Logical Link Control Protocol Class 1 over a STREAM to a MAC level driver. Multiple MAC level interfaces installed within the system can be supported by the driver. The llc1 driver provides basic support for the LLC1 protocol. Functions provided include frame transmit and receive, XID, and TEST, multicast support, and error recovery and reporting.

The cloning, character-special device, /dev/llc1, is used to access all LLC1 controllers configured under llc1.

The llc1 driver is a “Style 2” Data Link Service provider. All messages of types M_PROTO and M_PCPROTO are interpreted as DLPI primitives. An explicit DL_ATTACH_REQ message by the user is required to associate the opened stream with a particular device (ppa). The ppa ID is interpreted as an unsigned long and indicates the corresponding device instance (unit) number. An error (DL_ERROR_ACK) is returned by the driver if the ppa field value does not correspond to a valid device instance number for this system.

The values returned by the driver in the DL_INFO_ACK primitive in response to the DL_INFO_REQ from the user are as follows:

  • The maximum Service Data UNIT (SDU) is derived from the MAC layer linked below the driver. In the case of an Ethernet driver, the SDU will be 1497.

  • The minimum SDU is 0.

  • The MAC type is DL_CSMACD or DL_TPR as determined by the driver linked under llc1. If the driver reports that it is DL_ETHER, it will be changed to DL_CSMACD; otherwise the type is the same as the MAC type.

  • The sap length value is −1, meaning the physical address component is followed immediately by a 1-octet sap component within the DLSAP address.

  • The service mode is DL_CLDLS.

  • The MAC type is DL_CSMACD or DL_TPR as determined by the driver linked under llc1. If the driver reports that it is DL_ETHER, it will be changed to DL_CSMACD; otherwise the type is the same as the MAC type.

  • The dlsap address length is 7.

  • No optional quality of service (QOS) support is included at present, so the QOS fields should be initialized to 0.

  • The DLPI version is DL_VERSION_2.

  • The provider style is DL_STYLE2.

  • The broadcast address value is the broadcast address returned from the lower level driver.

Once in the DL_ATTACHED state, the user must send a DL_BIND_REQ to associate a particular Service Access Point (SAP) with the stream. The llc1 driver interprets the sap field within the DL_BIND_REQ as an IEEE 802.2 “SAP,” therefore valid values for the sap field are in the [0-0xFF] range with only even values being legal.

The llc1 driver DLSAP address format consists of the 6-octet physical (e.g., Ethernet) address component followed immediately by the 1-octet sap (type) component producing a 7-octet DLSAP address. Applications should not hard-code to this particular implementation-specific DLSAP address format, but use information returned in the DL_INFO_ACK primitive to compose and decompose DLSAP addresses. The sap length, full DLSAP length, and sap/physical ordering are included within the DL_INFO_ACK. The physical address length can be computed by subtracting the absolute value of the sap length from the full DLSAP address length or by issuing the DL_PHYS_ADDR_REQ to obtain the current physical address associated with the stream.

Once in the DL_BOUND state, the user may transmit frames on the LAN by sending DL_UNITDATA_REQ messages to the llc1 driver. The llc1 driver will route received frames up all open and bound streams having a sap which matches the IEEE 802.2 DSAP as DL_UNITDATA_IND messages. Received frames are duplicated and routed up multiple open streams if necessary. The DLSAP address contained within the DL_UNITDATA_REQ and DL_UNITDATA_IND messages consists of both the sap (type) and physical (Ethernet) components.

In addition to the mandatory, connectionless DLPI message set, the driver additionally supports the following primitives:

The DL_ENABMULTI_REQ and DL_DISABMULTI_REQ primitives enable/disable reception of specific multicast group addresses. A set of multicast addresses may be iteratively created and modified on a per-stream basis using these primitives. These primitives are accepted by the driver in any driver state that is valid while still being attached to the ppa.

The DL_PHYS_ADDR_REQ primitive returns the 6-octet physical address currently associated (attached) to the stream in the DL_PHYS_ADDR_ACK primitive. This primitive is valid only in states following a successful DL_ATTACH_REQ.

The DL_SET_PHYS_ADDR_REQ primitive changes the 6-octet physical address currently associated (attached) to this stream. Once changed, all streams subsequently opened and attached to this device will obtain this new physical address. Once changed, the physical address will remain set until this primitive is used to change the physical address again or the system is rebooted, whichever occurs first.

The DL_XID_REQ/DL_TEST_REQ primitives provide the means for a user to issue an LLC XID or TEST request message. A response to one of these messages will be in the form of a DL_XID_CON/DL_TEST_CON message.

The DL_XID_RES/DL_TEST_RES primitives provide a way for the user to respond to the receipt of an XID or TEST message that was received as a DL_XID_IND/DL_TEST_IND message.

XID and TEST will be automatically processed by llc1 if the DL_AUTO_XID/DL_AUTO_TEST bits are set in the DL_BIND_REQ.



cloning, character-special device


See attributes(7) for descriptions of the following attributes:


See Also

dlpi(4P), attributes(7)