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ULTRIX

Guide to the Data Link Interface

Order Number : AA- PBKZA-TE

ULTRIX

Guide to the Data Link Interface

Order Number: AA-PBKZA-TE
June 1990

Product Version:

ULTRIX Version 4.0 or higher

This manual tells you how to use the Data Link Interface (DLI) to write applications at the
data link layer. The manual explains programming procedures and provides DLI
programming examples.

digital equipment corporation
maynard, massachusetts

Restricted Rights: Use, duplication, or disclosure by the U.S. Government is subject to restrictions as set forth in
subparagraph (c) (1) (ii) of the Rights in Technical Data and Computer Software clause of DFARS 252.227-7013.

The information in this document is subject to change without notice and should not be construed as a commitment
by Digital Equipment Corporation. Digital Equipment Corporation assumes no responsibility for any errors that may
appear in this document.
The software described in this document is furnished under a license and may be used or copied only in accordance
with the terms of such license.
No responsibility is assumed for the use or reliability of software on equipment that is not supplied by Digital or its
affiliated companies.

The following are trademarks of Digital Equipment Corporation:

r;amDDma
CDA
DDIF
DDIS
DEC
DECnet
DEC station

DECUS
DECwindows
DTIF
MASSBUS
MicroVAX
Q-bus
ULTRIX
ULTRIX Mail Connection

ULTRIX Worksystem Software
VAX
VAXstation
VMS
VMS/ULTRIX Connection
VT
XUI

UNIX is a registered trademark of AT&T in the USA and other countries.
Ethernet is a registered trademark of Xerox Corporation.

Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 1

vii

Introduction to the Data Link Interface

1.1

What Is DLI? .............................................. .
1.1 .1
DLI Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.2
Hardware Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1
1-1
1-2

1.2

Using DLI to Access the Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-2

1.3

Prerequisites for DLI Programming .............................. .

1-2

1.4

Including Higher-Level Services ................................ .

1-2

1.5

DLI Concepts .............................................. .

1-3

Chapter 2

Understanding the DLI Socket Address Data Structure

2.1

How the sockaddr_dl Structure Works ............................ .
2.1.1
Specifying Values Within the Structure ...................... .
2.1.2
Using Ethernet and 802 Substructures ...................... .

2-1
2-1
2-2

2.2

Using the Ethernet Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.1
How Ethernet Frames Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Defining Ethernet Substructure Values ...................... .
2.2.2
2.2.2.1
Target Node Physical Address ................... .
2.2.2.2
Protocol Type .............................. .
I/O Control Flag ............................. .
2.2.2.3

2-3
2-4
2-4
2-4
2-4
2-4

2.3

Using the 8802-3 Substructure ................................. .
2.3.1
Defining 802 Substructure Values ......................... .
2.3.1.1
Target Node Physical Address ................... .
2.3.1 .2
Service Class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.2
Destination Service Access Point ......................... .
2.3.2.1
Source Service Access Point .................... .
2.3.2.2
Control Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-5
2-6
2-6
2-6

2-7
2-7
2-8

iii

Chapter 3
3.1

Supplying Data Link Services

3-1

3.2

Using ULTRIX System Calls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-1

3.3

Creating a Socket. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-2

3.4

Setting Socket Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-3

3.5

Binding the Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.1
Filling in the sockaddr_dl Structure . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.1.1
Specifying the Address Family . . . . . . . . . . . . . . . . . . . .
3.5.1.2
Specifying the I/O device 10 . . . . . . . . . . . . . . . . . . . . .
3.5.1.3
Specifying the Substructure Type ................. .
3.5.2
Calculating the 8uffer Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-4
3-4
3-4
3-4
3-5

3.6

Transferring Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-7

3.7

Deactivating the Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-7

Appendix A

3-7

DLI Data Structures

A.1

DLI Socket Address Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-1

A.2

DLI Device Identification Structure ............................... .

A-1

A.3

DLI Ethernet Socket Address Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-2

A.4

DLI 8802-3 Socket Address Structure ............................. .

A-2

A.5

8802-3 Packet Header Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-2

Appendix B

Index

Writing DLI Programs

DLI Programming Examples

B.l

Sample DLI Client Program Using Ethernet Format Packets ............. .

8-2

B.2

Sample DLI Server Program Using Ethernet Format Packets ............ .

8-6

B.3

Sample DLI Client Program Using 8802-3 Format Packets .............. .

8-10

B.4

Sample DLI Server Program Using 8802-3 Format Packets ............. .

8-14

B.5

Sample DLI Program Using getsockopt and setsockopt ............... .

8-18

Figures
2-1

The Ethernet Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-3

2-2

The 8802-3 Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-6

3-1

Calling Sequence for DLI Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-2

Data Transfer System Calls Used with DLI . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-7

Tables

Preface

The Guide to the Data Link Interface (DLl) tells you how to use the Data
Link Interface to write application programs that run at the data link layer.

Audience
This guide is intended for anyone responsible for application programming using
the Data Link Interface. It assumes the following:
•

You have superuser (root) privileges.

•

You are familiar with an editor, such as vi or ed.

•

You have a thorough knowledge of the C programming language, with experience writing system or network programs.

•

You are familiar with ULTRIX socket calls.

•

You are familiar with the 8802-2 and 8802-3 protocols.

•

You are familiar with ULTRIX naming conventions.

Organization
This guide has three chapters and two appendixes:
Chapter 1:

Introduction to the Data Link Interface
Describes the Data Link Interface (DLl) capabilities and prerequisites for
using it.

Chapter 2:

Understanding the DLI Socket Address Data Structure
Describes format and input arguments used in the DLI socket address
(sockaddr_dl) structure, as well as the Ethernet and 8802-3 substructures.

Chapter 3:

Writing DLI Programs
Gives procedures for writing DLI programs.

Appendix A:

DLI Data Structures
Shows DLI data structures.

Appendix B:

DLI Programming Examples
Shows DLI programming examples.

vii

Related Documents
For additional information, see the following documents:

•

ULTRIX version 4.0 Release Notes
This manual gives information and updates not included in the ULTRIX
documentation set.

•

ULTRIX Reference Pages
These volumes provide ULTRIX system reference pages, which describe
commands, system calls, subroutines, file formats, and special files.

•

Guide to Network Programming
This manual describes network programming concepts for programming in
the ULTRIX environment.

To obtain a detailed description of the Digital Network Architecture, refer to the
following document:

•

DECnet Digital Network Architecture (Phase N), General Description

•

DECnet Digital Network Architecture, CSMA / CD Data Link Functional
Specification, v.1.0.1, Nov. 1985

For more information about the IEEE 8802-3 frame format, refer to the following
two standards:

•

Carrier Sense Multiple Access with Collision Detection (CSMA/ CD) Access
Method and Physical Layer Specifications, ANSIIIEEE Std 8802-3-1985, ISO
Draft International Standard 8802/3.

•

Logical Link Control, ANSIIIEEE Std 802.2-1985, ISO Draft International
Standard 8802/2.

Both standards are published by the Institute of Electrical and Electronics
Engineers, Inc. and are distributed in cooperation with Wiley-Interscience, a
division of John Wiley & Sons, Inc.

Terms and Acronyms
The following terms are used in this manual:
802

Refers to both ISO 8802-2 and ISO 8802-3. ISO 8802-2 is equivalent to
IEEE 802.2 and ISO 8802-3 is equivalent to IEEE 802.3.

Ethernet

A physical transmission media (cables and controllers) and data link software that provides access to the physical media according to the CSMAlCD
protocol. DLI programs can transfer data over Ethernet using the usual
Ethernet frame format or the Open Systems Interconnect (OSI) 8802-3
frame format.

The following acronyms are used in this manual:
DLI

viii

Data Link Interface

DNA

Digital Network Architecture

DSAP

Destination Service Access Point

IEEE

Institute of Electrical and Electronics Engineers

LLC

Logical Link Control

SAP

Service Access Point

SSAP

Source Service Access Point

SNAP

Subnetwork Access Protocol

XID

Exchange Identification

Graphic Conventions
Convention

Meaning

Special type

In text, each mention of a specific command, option, partition,
pathname, directory, or file is presented in this type.

command(x}

In text, cross-references to the command documentation include the section number in the reference manual where the
commands are documented. For example: See the cat(1} command. This indicates that you can find the material on the cat
command in Section 1 of the reference pages.

italics

In syntax descriptions, this type indicates terms that are
optional.

[ ]

In syntax descriptions, square brackets indicate terms that are
optional.
In syntax descriptions, a horizontal ellipsis indicates that the
preceding item can be repeated one or more times.

UPPERCASE

The ULTRIX system differentiates between lowercase and
uppercase characters. Enter uppercase characters only where
specifically indicated by an example or a syntax line.

example

In examples, computer output text is printed in this type.

All Ethernet addresses are hexadecimal; all other numbers are decimal unless
otherwise noted.

New and Changed Information
This is a new manual.

Chapter 1

Introduction to the Data Link Interface
This chapter describes the capabilities of the Data Link Interface (DLI) and
explains some basic DLI concepts.

1.1 What Is DLI?
DLI is network software that lets programs on an ULTRIX Ethernet node
communicate with data link programs on another Ethernet node. DLI lets a
user program interact directly with the broadcast network device drivers of an
ULTRIX system.
DLI programs can transfer data over an Ethernet using the standard Ethernet
frame format or the Open Systems Interconnect (OS1) 8802-3 frame format. Your
ULTRIX node can run DECnet, Internet, and DLI programs concurrently. Each
program can communicate with programs executing on a remote Ethernet node.

1.1.1

DLI Services
DLI provides the following services at the data link layer:
•

Datagram service.

•

Ethernet or 802 packets.

•

ISO 8802-2 Class I, Type I service.

•

Ability to use a multicast address mode to send and receive messages over the
network. Multicast address mode sends simultaneous messages to a group of
nodes.

Introduction to the Data Link Interface

1-1

1.1.2

Hardware Support
DLI supports the following hardware:

•
•
•
•
•
•
•

DEBNA
DEBNI (XNA)
DEBNT
DELQA
DEQNA
DESVA
DEUNA

1.2 Using DLI to Access the Ethernet
An Ethernet data link on a single Ethernet controller supports multiple
concurrent users. Each station represents an available port onto the Ethernet
channel.
Because multiple users simultaneously access the Ethernet channel, your
program must use addressing mechanisms that ensure delivery of messages to
the correct recipient. Any message you transmit on the Ethernet must include an
Ethernet address that identifies the target node. The message must also include
an additional identifier that directs the message to the correct user on the target
node; this identifier varies according to the frame format you choose to use. DLI
builds frames according to the Ethernet or IEEE 8802-3 standard.

1.3 Prerequisites for DLI Programming
ULTRIX allows only superusers to run DLI applications. If you do not have the
required privileges to run a DLI program, see your system manager.
DLI programming requires both a thorough knowledge of the C programming
language and experience writing system programs. If you intend to use the 802
substructure, you should also be familiar with 802 protocols.

1.4 Including Higher-Level Services
DLI provides only datagram service. Because DLI is a direct interface to the Data
Link layer, it does not offer higher-level services normally provided by Internet
and DECnet. Therefore, your application should provide the following kinds of
services:
•

Packet routing and guaranteed delivery

•

Flow control

•

Error recovery

•

Data segmentation

1-2 Introduction to the Data Link Interface

1.5 DLI Concepts
Familiarity with the following concepts will help you effectively use the DLI
programming procedures described in this manual:
•

Datagram Sockets-Your application uses sockets to send and receive both
Ethernet and 8802-3 frames. DLI uses datagram sockets only.
For more information about sockets and how to use them, see the Guide to
Network Programming.

•

Logical Link Control (LLC)-LLC is a sublayer of DLI that provides a set of
services determined by a value in the 8802-2 frame format.

•

Physical and Multicast Addressing-You can send and receive messages over
the network using physical or multicast addresses. You can send physical
addresses to a single destination node. Multicast addresses are not associated
with any specific node; instead, a packet sent to a multicast address is
received by all nodes with the multicast address enabled.

•

Standard Frame Formats-The Ethernet format is a proprietary standard
that belongs to Digital Equipment Corporation, Intel Corporation, arid
Xerox Corporation. The IEEE 8802-3 format is a standard for multivendor
networking. Any single application can send and receive both types of frames.

Introduction to the Data Link Interface

1-3

Chapter 2

Understanding the Dli Socket Address Data
Structure
This chapter describes the function of the DLI Socket Address data structure
(sockaddr_dl). It explains how you use sockaddr_dl to specify the domain
address, the network device, and the Ethernet and 8802-3 substructures.

2.1

How the sockaddr_dl Structure Works
DLI provides a socket address data structure through which you can configure
the set of services required for communication at the data link layer. The data
structure sockaddr_dl is used to convey information to DLI when an application
binds to the network, or when it transmits a packet to the network. DLI also
uses it to convey information to the application when it receives a packet from
the network. This includes network device information, the packet format to be
used, and addressing information.
The following example shows the DLI socket address structure:
#define DL1 ETHERNET
#define DL1 802
struct sockaddr dl

0
2

{

u_short dli_familYi
struct dli devid dli_devicei
u char dli substructypei

/*
/*
/*
/*

address family (AF_DL1) */
id of communication device */
id to interpret following union */
set to DL1 ETHERNET or DL1 802 */

union
struct sockaddr edl dli_eaddr;
/* Ethernet support */
struct sockaddr 802 dli 802addri /* OS1 802 support */
choose_addri
};

2.1.1

Specifying Values Within the Structure
You can use system calls to specify values within the socket address structure
by using either the Ethernet or 802 substructures. The fields within the
substructures are updated as a function of the system call. For example, the bind
call is used to specify the domain, network device, and most of the substructure.
The sendto call is used to specify the domain, network device, and part of the
substructure. The recvfrom call is used to specify the domain and network
device, and DLI fills in part of the substructure.
For further information, see bind(2), recvfrom(2), and sendto(2) in the ULTRIX
Reference Pages.

Understanding the DLI Socket Address Data Structure

2-1

The dlLeconn and dIL802_3_conn user-written subroutines open a socket
and bind the associated domain, network device name, protocol type, and other
substructure information to the socket.
The following code shows how the dli_econn subroutine can be used to fill in the
sockaddr_dl data structure:
dli_econn(devname, devunit, ptype, taddr, ioctl)
char *devname;
u_short devunit;
u_short ptype;
u_char *taddr;
u char ioctl;
{

int i, sock;
struct sockaddr_dl out bind;
if

(i = strlen(devname)) >
sizeof(out_bind.dli_device.dli_devname)
fprintf(stderr,
return(-l);

)

"dli eth: bad device name");

if ((sock = socket (AF_DLI, SOCK DGRAM, DLPROTO DLI)) < 0)
{

perror(IIdli_eth, can't open DLI socket");
return(-l);

Section B-1 contains the complete code for the dli_econn subroutine.

2.1.2

Using Ethernet and 802 Substructures
Any single application can send and receive both Ethernet and 802 substructures.
The Ethernet substructure enables applications to communicate across an
Ethernet. The 802 substructure enables applications to use 8802-2 and 8802-3
protocols to communicate with each other.
The following sections describe the functions the Ethernet and 8802-3
substructures provide within the DLI sockaddr_dl data structure.

2-2

Understanding the DLI Socket Address Data Structure

2.2 Using the Ethernet Substructure
The Ethernet substructure lets you specify the target node's physical address,
the client layer protocol type, and an I/O control flag for the protocol type. This
information is used to create the Ethernet frame format.
The following example shows the DLI Ethernet socket address structure:
#define DLI EADDRSIZE
struct sockaddr edl

{

u_char dli_ioctlflg;
u short dli protype;
u-char dli_target[DLI_EADDRSIZE];
u char dli_dest[DLI_EADDRSIZE];

/* filter on incoming packets */
/* Ethernet protocol type */
/* Ethernet address of target node */
/* Ethernet address used to address */
/* the local node; DLI places */
/* the destination address of an */
/* incoming packet here to be */
/* used in the recvfrom call. */

};

Figure 2-1 illustrates the Ethernet frame format.
Figure 2-1:

octets:

The Ethernet Frame Format

I PREAM I D AI S AI P Type

46-1500
Data

I PAD I FCS I
LKG~692-891

Understanding the DLI Socket Address Data Structure

2-3

2.2.1

How Ethernet Frames Work
All Ethernet frames contain a 16-bit identification number called an Ethernet
protocol type. When a message arrives at the controller, the protocol type
is issued to identify which port receives the frame. DLI applications that
communicate across the Ethernet must always enable the same Ethernet protocol
type. In addition to using protocol types to select a user for an incoming packet,
you can configure DLI to select a user as a function of both the protocol type and
the physical address of the remote node. This allows several applications in the
same system to use the same type, which can make input/output simpler for the
application.

2.2.2

Defining Ethernet Substructure Values
The following sections define the possible values for all members in the Ethernet
substructure.

2.2.2.1

Target Node Physical Address

The target node physical address is a 48-bit unique value assigned by Xerox
Corporation to a station on the Ethernet. For example, AA-00-03-22-14-55 is a
valid Ethernet address and it is the address of the remote node.
If you do not specify the target node physical address with the bind call, you must
specify this address when sending data by using the sendto call. In addition, you
should use the recvfrom call to determine the source of a data message.
You can use either the physical address or a multicast address to send messages.
2.2.2.2

Protocol Type

The protocol type is a 16-bit value in the Ethernet frame following the source
address. The Ethernet driver passes the protocol type to DLI for use in
determining the recipient of the data in the frame. With the exception of
reserved values, you can use any Ethernet protocol type assigned to you by
Xerox Corporation and not used elsewhere in your system.
The following hexadecimal values are reserved for use by the system:

2.2.2.3

2-4

•

OX 800

•

OX 806

•

OX 1000 <ptype> OX 1010, where ptype is the protocol type

I/O Control Flag
The I/O control flag is a value that DLI uses to determine how your program
reserves a protocol type. That is, it is used by DLI to determine whether to select
a user as a function of the protocol type alone, or as a function of the combination
of the protocol type and the target audience. The following list defines the
possible I/O control flags and describes the conditions for their use:

Understanding the DLI Socket Address Data Structure

•

NORMAL - Allows your program to exchange messages with one target node,
using only the specified protocol type. When using the NORMAL flag, you
must specify the target node physical address in the bind call, and you can
use any of the data transfer calls to send and receive data. DLI forwards to
the user all messages containing the specified protocol type from the specified
target.

•

EXCLUSIVE - Gives your program exclusive use of the specified protocol type
and allows the program to exchange data with any other node using this
protocol type. In other words, the program receives all messages with the
specified protocol type. When you use the EXCLUSIVE flag, do not specify
the target address with the bind call. You must use the sendto and recvfrom
calls to exchange data with other nodes, and you must specify the target
address with the sendto call. In the address structure (returned with
recvfrom), DLI fills in the target address with the source address in the
Ethernet frame. It also fills in the destination address with the destination
address in the Ethernet frame.

•

DEFAULT - Allows your program to receive messages that contain the
specified protocol type and that are meant for no other program on the
system. If no other program is bound exclusively to the protocol type or the
protocol type/address pair in the message, the socket bound to the protocol
type gets the message by default. This mode of operation is recommended for
use in programs that listen for messages but do not necessarily send them.
When you use the DEFAULT flag, do not specify the target address with the
bind call. Use the recvfrom call to receive data from other nodes. If you are
using the DEFAULT flag, DLI fills in the target node's physical address and
the destination address used for the incoming message on this call.

2.3 Using the 8802-3 Substructure
The 8802-3 substructure enables applications to communicate with each other
using the 8802-2 and 8802-3 protocol. It uses two basic modes of operation: Class
I, Type 1 service, and the services supplied by your application using the 8802-2
protocol.
The following example shows the DLI 8802-3 socket address structure:

struct sockaddr 802

/* 8802-3 sockaddr struct */

{

u char ioctli
u char SVCi
struct osi 802hdr eh_802i

/*
/*
/*
/*

filter on incoming packets */
addressed to the SNAP SAP */
service class for this portal */
OS1 802 header format */

The 8802-3 substructure lets you specify values for the following field in the
8802-3 frame format:
•

Target node physical address.

•

Source service access point (SSAP). The protocol identifier and I/O control
field may be required, depending on the type of SSAP you enable.

•

Destination service access points (DSAPs).
Individual
Group

Understanding the DLI Socket Address Data Structure

2-5

•

Control field

Figure 2-2 illustrates the 8802-3 frame format.
Figure 2-2:

The 8802-3 Frame Format

Length

~D_S_A_P~__~__~__ln_f_o_l~
octets:

1
LKG-3779-901

NOTE

The Institute of Electrical and Electronics Engineers (IEEE) has
defined the 802 frame format for communicating over the Ethernet.
Before using the 8802-3 frame format, be sure to familiarize yourself
with the IEEE standard.

2.3.1

Defining 802 Substructure Values
The following sections define the possible values for all members in the 802
substructure.

2.3.1.1

Target Node Physical Address

The target node physical address is a 48-bit unique value assigned by Xerox
Corporation to a station on the Ethernet. For example, AA-00-03-22-14-55 is a
valid Ethernet address. This is the address of the remote node, with which the
application will attempt to exchange packets. It must be specified in the bind
call, except when the I/O control field is ether EXCLUSIVE or DEFAULT and the
service access point (SAP) is a SNAP_SAP type. The SAP must be specified in
the sendto call.

2.3.1.2

Service Class

The service class is a value in the 8802-3 substructure that determines the
capabilities and features provided by the Logical Link Control (LLC) sublayer of
the data link layer. The possible service classes are:
•

2-6

TYPE1 - This value causes DLI to interpret all header information and
provide Class I, Type 1 service.

Understanding the DLI Socket Address Data Structure

When Type 1 service is used, the DLI software handles the XID and TEST
packets. This is transparent to the application. DLI uses the source and
destination service access points to determine who should receive the
message; it interprets the control field on behalf of the user. Whether DLI
passes the data field to the user depends on the value of the control field.
•

2.3.2

USER - This value provides few services. The user must, therefore, implement
most of the 8802-2 protocol. In other words, the application must handle the
XID and TEST packets. DLI uses the source and destination service access
points, but it passes the control field with the data to the user. The user must
interpret the control field. This mode should be selected if the application
needs to implement Class II, Type 2 service.

Destination Service Access Point
The destination service access point (DSAP) is a field in the 8802-3 structure
that identifies the application for which the message is intended. You can use
individual or group DSAPs to identify one user or a group of users. (You can use
group DSAPs only when the service class is set to USER.) The possible values for
this field are:
•

Individual DSAPs:
NULL_SAP - A DSAP consisting of all zeros. You can send TEST and XID
commands and responses, but no data, to a NULL_SAP. (TEST and XID are
explained later in this section.) The data link layer uses the NULL_SAP to
talk to another data link layer, primarily for testing.
SNAP_SAP - The 8802-3 Subnetwork Access Protocol. When you send data,
you should enable a source SNAP_SAP and send to a remote destination
SNAP_SAP.

Only unnumbered information (VI) packets can be sent or received when
using the SNAP_SAP.
V ser-defined DSAP - Identifies one user for whom the message is intended.
The user-defined individual DSAP must be an even number greater than or
equal to 2 and less than or equal to 254.

•

2.3.2.1

Group DSAP (user-defined) - Identifies more than one user for whom the
message is intended. You can send data to a maximum of 127 group DSAPs
on one socket. The user-defined group DSAP must be an odd number greater
than or equal to 3 and less than or equal to 255. Note that the 255 number
is the global SAP and must be enabled like any other group SAP. You can use
Group SAPs only when the service class is set to USER.

Source Service Access Point

The source service access point (SSAP) is a field in the 8802-3 frame that
identifies the address of the application that sent the message. You can enable
only one SSAP on a socket. The possible values for this packet are:
•

SNAP_SAP - The 8802-3 Subnetwork Access Protocol. When you enable a
source SNAP_SAP you must specify the protocol identifier and control field.

The protocol identifier is five bytes. The control field is one byte. Enabling
the SNAP_SAP is allowed only when the service class is TYPE1.
Understanding the DLI Socket Address Data Structure

2-7

Only unnumbered information (VI) packets can be sent or received when
using the SNAP_SAP.

•

V ser-defined - The individual SSAP must be an even number greater than or
equal to 2 and less than or equal to 254.

The IEEE 8802-2 Standard reserves for its own definition all SAP addresses with
the second least significant bit set to 1. It is suggested that you use these SAP
values for their intended purposes, as defined in the IEEE 8802-2 Standard.
2.3.2.2

Control Field

The control field specifies the packet type. The following values are defined for
Type 1, Class I service, and can also be used in user-supplied mode to provide
Type 2, Class II service.
An application using this user mode is responsible for providing the correct
services. For other operations supported by CLASS II service, see the IEEE
Standards for Local Area Networks: Logical Link Control, published by the
Institute of Electrical and Electronics Engineers, Inc.
•

Exchange Identification - The value XID identifies the exchange identification
command or response. An 8-bit format identifier and a 16-bit parameter
follow the XID control field. The 16-bit parameter identifies the supported
LLC services and the receive window size. The LLC is the top sublayer in
the Data Link layer of the IEEE/Std 802 Local Area Network Protocol. The
following values of XID are defined in the DLI header file, dli_var.h:
XID_PCMD - Exchange identification command with the poll bit set.
The exchange identification command conveys the types of LLC services
supported and the receive window size to the destination LLC. This
command causes the destination LLC to reply with the XID response
Protocol Data Vnit (PDV) at the earliest opportunity. The poll bit is set to
1, soliciting a response PDV.
XID_NPCMD - Exchange identification command with no poll bit set. This
command is identical to the previous command, except that you clear the
poll bit. No response is expected.
XID_PRSP - Exchange identification response with the poll bit set. The
Data Link layer uses the exchange identification response to reply to
an XID command at the earliest opportunity. The XID response PDV
identifies the responding LLC and includes an information field like that
defined for the XID command PDV, regardless of what information is
present in the information field of the received XID command PDV. The
final bit is set to 1, indicating that this response is sent by the LLC as a
reply to a soliciting command PDV.
XID_NPRSP - Exchange identification response with no poll bit set. This
response is identical to the previous one, except that the final bit is
cleared.

•

LLC Protocol Data Vnit Test - The value TEST identifies the LLC PDV
command or response test. The TEST control field can be followed by a
data field. The following values of TESt are defined in the DLI header file,
dILvar.h:
TEST_PCMD - Test command with the poll bit set. This command tests

the LLC-to-LLC transmission path by causing the destination LLC to
respond with the TEST response Protocol Data Vnit (PDV) at the earliest
opportunity. An information field is optional with this control field value.
If used, the receiving LLC returns the information rather than passing it
to the user. The poll bit is set to 1, soliciting a response PDV.
2-8

Understanding the DLI Socket Address Data Structure

TEST_NPCMD - Test command with no poll bit set. This command is
identical to the previous command, except that the poll bit is cleared.
TEST_PRSP - Test response with the poll bit set. This response
Protocol Data Unit (PDU) is a reply to the TEST command PDU. An
information field, if present in the TEST command PDU, is returned in
the corresponding TEST response PDU. The final bit is set to 1, indicating'
that this response is sent by the LLC as a reply to a soliciting command
PDU.
TEST_NPRSP - Test response with no poll bit set. This response is
identical to the previous one, except that the final bit is cleared.

•

Unnumbered Information Command - The Unnumbered information
command with no poll set (ULNPCMD) sends information to one or more
LLCs. The UI_NPCMD command does not have an LLC response PDU. This
is usually passed up to the application.
Applications generally send and receive data using this command.

Understanding the DLI Socket Address Data Structure

2-9

Chapter 3

Writing Dli Programs
This chapter explains how to use ULTRIX system calls to write DLI programs
and describes procedures for specifying values within the Ethernet and 8802-3
substructures. Appendix B contains DLI programming examples of procedures
described in this chapter.
For additional information on how to use sockets and system calls to write
application programs, refer to the Guide to Network Programming.

3.1

Supplying Data Link Services
Your DLI application should contain other services that the higher levels of
network software normally provide:
•

Flow control-DLI programs running on different nodes must synchronize
data transfer or they will lose data.

•

Error recovery-DLI reports errors, but your application must recover from
them.

•

Data segmentation-Your application must segment data during
transmission. (See Section 3.5.2 for instructions on how to calculate the
buffer size for Ethernet and 8802-3 packets.)

3.2 Using ULTRIX System Calls
Your DLI program uses standard ULTRIX system calls with input arguments,
structures, and substructures specific to DLI. For example, when issuing the
socket call, your program uses the the address format AF_DLI and the protocol
DLPROTO_DLI.

Writing DLI Programs

3-1

At the beginning of any DLI program, you must include the header file,
Isys/netdnet/dli_var.h. Then, follow the calling sequence shown in Table 3-1.

Table 3-1:

Calling Sequence for DLI Programs

Function

System Call

Create a socket.

socket
bind

Bind the socket to a device by specifying the address
family, the frame format type, and the device over which
the program will send the data using the sockaddr_dl
structure.
Set socket options. This call is optional.
Transfer data.

Deactivate the socket descriptor.

setsockopt
write
send
sendto
read
recv
recvfrom
close

The following sections describe DLI functions, input arguments, and structures.

3.3 Creating a Socket
Your DLI application must create a socket by using the socket system call with
the following input arguments:
Address family: AF_DLI
Socket type: SOCK_DGRAM
Protocol: DLPROTO_DLI
The value AF_DLI specifies the DLI address family. SOCK_DGRAM creates a
datagram socket, which is the only type of socket that DLI allows. DLI does not
supply the services necessary for connecting to other programs and for using
other socket types. The value DLPROTO_DLI specifies the DLI protocol module.
The following example shows how the socket call is used to open a socket to DLI:
int so;

if ( (so = socket(AF_DLI,SOCK_DGRAM,DLPROTO_DLI))<O)
{

perror("cannot open DLI socket");
return (-1);

3-2

Writing DLI Programs

3.4 Setting Socket Options
Use the setsockopt call to set the following socket options within the
sockaddr_dl structure:
DLLENAGSAP: Enables a Group Service Access Point (GSAP)
DLLDISGSAP: Disables a Group Service Access Point (GSAP)
DLI_SET802CTL: Sets the 802 control field
DLI_MULTICAST: Enables the reception of all messages addressed to a

multicast address
The following code examples show how to use the setsockopt call to set the
socket options.
This example shows how the setsockopt call is used to enable the GSAP option:
/* enable GSAPs supplied by user */
j = 3;
i = 0;
while (j < argc ) {
sscanf(argv[j++], "%X", .«k);
out_opt [i++] = k;
opt len = i;
if
(setsockopt(sock,DLPROTO_DLI,DLI_ENAGSAP,&out_opt[O],optlen) < 0) {
perror(IIdli_setsockopt: Can't enable gsap");
exit(l);

This exam pIe shows how the setsockopt call is used to disable the GSAP option:
/* disable all but the last 4 or all GSAPs, */
/* whichever is smallest */
if ( optlen > 4 )
optlen -= 4;
if
(setsockopt(sock,DLPROTO_DLI,DLI_DISGSAP,&Out_opt[O],optlen) < 0) {
perror("dli setsockopt: Can't disable gsap");

This example shows how the setsockopt call is used to set the 802 control field:
/* set 802 control field */
out_opt [0] = TEST_PCMD;
optlen = 1;
if
(setsockopt(sock,DLPROTO_DLI,DLI_SET802CTL,
&out opt[O],optlen)<O) {
perror("dliyetsockopt: Can't set 802 control");
exit (1) ;

Writing DLI Programs

3-3

This example shows how the setsockopt call is used to enable two multicast
addresses:
/* enable two multicast addresses */
bcopy(mcastO, out_opt, sizeof(mcastO));
bcopy(mcastl, out_opt+sizeof(mcastO), sizeof(mcastl));
if ( setsockopt(sock, DLPROTO_DLI, DLI_MULTICAST, &out_opt[O] ,
(sizeof (mcastO) + sizeof (mcastl) )) < 0 ) {
perror("dli setsockopt: can't enable multicast");

See Section B.5 for more detailed code examples.

3.5 Binding the Socket
Mter you create the socket, your application must bind the socket to a network
device. At this point, you specify the type of format for the message. You assign
a name to the socket, where the variable name is a pointer to a structure of the
type sockaddr_dl. Then, you must fill in the sockaddr_dl data structure and
include the substructures (Ethernet, 802, or both).
To bind the socket, use the following format:

bind (s,name,namelen)
int s;
struct sockaddr_dl *name;
int namelen;

For more information about the bind call, see bind(2) in the ULTRIX Reference
Pages.

3.5.1

Filling in the sockaddr_dl Structure
Fill in the sockaddr_dl structure with the following information:

3.5.1.1

•

Address family

•

I/O device ID

•

Substructure type

Specifying the Address Family

To specify the Address family, use the value AF_OLl in the socket call.

3.5.1.2

Specifying the I/O device 10

The I/O device is the controller over which your program sends and receives
data to and from the target node. The I/O device ID consists of the device name
(dli_devname) and the device number (dli_devnumber). Definitions for each
variable follow:

•

dli_devname: The possible device names are: de, qe, In, xna, and ni.

•

dli_devnumber: The device number is set up in the system configuration file.

3-4 Writing DLI Programs

3.5.1.3

Specifying the Substructure Type

The substructure specifies the type of frame format that the program will use.
Definitions for each variable follow:
•

dli_eaddr: Ethernet frame format (DLLETHERNET)

•

dli_802addr: 8802-3 frame format (DLL802)

A program can send and receive both Ethernet and 8802-3 frames, as long as it
has a socket for each type. For example, your DLI program might communicate
with one node using the Ethernet frames and another node using 8802-3 frames.
Your choice of frame formats depends on the frame types used by the target
program.
NOTE

Only one type of frame is allowed for each socket.
Your program must specify the packet header for sending your message after
filling in the substructure of your choice. The following examples show how to fill
the sockaddr_dl structure.
This example shows how to fill the sockaddr_dl structure for the Ethernet
protocol:
/*

* fill out the sockaddr dl structure for the bind call
*/
bzero(&out_bind, sizeof(out_bind))i
out_bind.dli_family = AF_DLli
out_bind.dli_substructype = DLI_ETHERNETi
bcopy(devname, out_bind. dli_device. dli_devname, i)i
out_bind.dli_device.dli_devnumber = devunit;
out_bind.choose_addr.dli_eaddr.dli_ioctlflg = ioctl;
out_bind.choose_addr.dli_eaddr.dli_protype = ptype;
if ( taddr )
bcopy(taddr, out_bind. choose_addr. dli_eaddr.dli_target,
DLI_EADDRSIZE) ;
if

bind(sock, &out_bind, sizeof(out_bind)) < 0 )

{

perror(IIdli_eth, can't bind DLI socket");
return(-l) ;
return (sock) ;

Writing DLI Programs

3-5

This example shows how to fill the sockaddr_dl substructure for the 802 protocol:
/*

* fill out sockaddr dl structure for the bind call.
* note that we need to determine whether the
* control field is S bits (unnumbered format) or
* 16 bits (informational/supervisory format) . We do this
* by checking the low order 2 bits, which are both 1 only
* for unnumbered control fields.
*/

bzero(&out_bind, sizeof(out_bind));
out_bind.dli_family = AF_DLI;
out_bind.dli_substructype = DLI_S02;
bcopy(devname, out_bind.dli_device.dli_devname, i);
out_bind.dli_device.dli_devnumber = devunit;
out_bind.choose_addr.dli_S02addr.ioctl = ioctl;
out_bind.choose_addr.dli S02addr.svc = svc;
if(ctl & 3)
out bind.choose_addr.dli_S02addr.eh_S02.ctl.U_fmt=(u char)ctl;
else
out_bind.choose_addr.dli_S02addr.eh_S02.ctl.I_S_fmt = ctl;
out bind.choose addr.dli S02addr.eh S02.ssap
sap;
out=bind.choose=addr.dli=S02addr.eh=S02.dsap = dsap;
if ( ptype )
bcopy(ptype,out_bind.choose_addr.dli_S02addr.eh_S02.osi_pi,5);
if ( taddr )
bcopy(taddr, out_bind.choose_addr.dli_S02addr.eh_S02.dst,
DLI_EADDRSIZE) ;
if
bind(sock, &out_bind, sizeof(out_bind)) < 0 )
{

perror("dli S02, can't bind DLI socket");
return (-1) ;
return(sock);

Writing DLI Programs

3.5.2

Calculating the Buffer Size
The buffer size should be no larger than the controllers on the communicating
nodes can handle, or you will lose data. The maximum buffer size for Ethernet
packets is 1500 bytes. The maximum buffer size for 8802-3 packets is calculated
as follows:
bytes = 1500 -

[ 2 + (control field == UI? 1:2) +
(Source SAP == SNAP SAP? 5:0)]

The number of bytes in the control field and in the Source SAP are specified in
the bind call.

3.6 Transferring Data
The DLI program can use the write, send, or sendto calls to send data and the
read, recv, or recvfrom calls to receive data. The "X" in Table 3-2 indicates the
conditions under which you can use the system calls with the bind call.
NOTE

You must set the target address in the bind call when using the Normal
control flag, not when using the Exclusive or Default control flags.
Table 3-2:

Data Transfer System Calls Used with DLI

System Calls

write
send
sendto
read
recv
recvfrom

Normal
Control

Exclusive
Control

Default
Control

X
X
X
X
X
X

When you set the control flag to NORMAL, set the target address in the bind call.
Then use any of the following calls to transfer data: write, send, sendto, read,
recv, recvfrom.
When you set the control flag to EXCLUSIVE, make the value of the target
address in the bind call zero. Then, set the target address in the sendto call.
Use only the sendto and recvfrom calls to transfer data.
When you set the control flag to DEFAULT, make the value of the target address
in the bind call zero. Then, use the sendto call to send data and set the target
address in that call. Use the recvfrom call to determine the source address of any
data.

3.7 Deactivating the Socket
When you have finished sending or receiving data, you can deactivate the socket
by issuing the close call. For more information about the close call, see close(2)
in the ULTRIX Reference Pages.

Writing DLI Programs

3-7

Appendix A

DLI Data Structures
This chapter contains the DLI data structures that are defined in the header file,
lusr/include/netdnet/dli_var.h. For guidelines on specifying these data structures,
see the relevant system calls and the header file, dli_var.h.

A.1

Dli Socket Address Structure
The following example shows the DLI socket address structure:
#define DLI_ETHERNET
#define DLI 802
struct sockaddr dl

0
2

{

u_short dli_family;
struct dli devid dli_device;
u char dli substructype;

/*
/*
/*
/*

address family (AF DLI) */
id of communication device */
id to interpret following union */
set to DLI ETHERNET or DLI 802 */

union
struct sockaddr edl dli_eaddr;
/* Ethernet support */
struct sockaddr 802 dli 802addr; /* OS1 802 support */
choose_addr;
};

A.2 Dli Device Identification Structure
The following example shows the DLI device identification structure:
#define DLI_DEVSIZE
struct dli devid

{

u_char dli_devname[DLI_DEVSIZE+1];
u short dli_devnumber;

/* device name */
/* device unit number */

};

DLI Data Structures

A-1

A.3 DLI Ethernet Socket Address Structure
The following example shows the DLI Ethernet socket address structure:
#define DL1 EADDRS1ZE
struct sockaddr edl

{

u_char dli_ioctlflg;
u_short dli_protype;
u_char dli_target[DL1_EADDRS1ZE];
u char dli_dest[DL1_EADDRS1ZE];

/* filter on incoming packets */
/* Ethernet protocol type */
/* Ethernet address of target node */
/* Ethernet address used to address */
/* the local node; DL1 places */
/* the destination address of an */
/* incoming packet here to be */
/* used in the recvfrom call. */

};

A.4 DLI 8802-3 Socket Address Structure
The following example shows the DLI 8802-3 socket address structure:
struct sockaddr 802

/* 8802-3 sockaddr struct */

{

u char ioctl;

/* filter on incoming packets */

u char svc;
struct osi 802hdr eh_802;

/* addressed to the SNAP SAP */
/* service class for this portal */
/* OS1 802 header format */

};

A.5 8802-3 Packet Header Format
The following example shows the 8802-3 packet header format:
#define DLI EADDRSIZE
struct osi 802hdr

{

u_char dst[DLI EADDRSIZE];
u_char src[DLI_EADDRSIZE];
u_short len;
u_char dsap;
u_char ssap;
union {
u_char U_fmt;
u_short I_S_fmt;
}ctl;
u char osi_pi[5];m
};

A-2

DLI Data Structures

/*
/*
/*
/*
/*
/*

Ethernet address of remote node */
Ethernet address of local node */
length of user data and 802 header */
SAP used by the remote node */
SAP used by the local node */
control field */
/* unnumbered information format */
/* information/supervisory format */

/* 8802-3 protocol identifier used */
/* when SNAP SAP is used */

Appendix B

DLI Programming Examples
This appendix presents the following DLI programming examples:

B.l: A sample DLI client program using Ethernet format packets
B.2: A sample DLI server program using Ethernet format packets
B.3: A sample DLI client program using 8802-3 format packets
B.4: A sample DLI server program using 8802-3 format packets
B.5: A sample DLI program using getsockopt and setsockopt system calls
These programming examples are also available on-line in lusr/examples/dli.

DLI Programming Examples

8-1

B.1

Sample DLI Client Program Using Ethernet Format Packets
#ifndef lint
static char
#endif lint

*sccsid

"@(#)dli_eth.c

1.5

3/27/90";

#include <stdio.h>
#include <ctype.h>
#include <errno.h>
#include <strings.h>
#include <sys/types.h>
#include <sys/socket.h>
#include '<net/if.h>
#include <netinet/in.h>
#include <netinet/if ether.h>
#include <netdnet/dli var.h>
#include <sys/ioctl.h>
extern int errno;

/*
d I i
e x amp I e : d I i
e t h
*
*
* Description: This program sends out a message to a node where a
companion program, dli_ethd, echoes the message.
*
The Ethernet packet format is used.
The Ethernet
*
address of the node where the companion program is
*
running, the protocol type, and the message are
*
supplied
by the user.
The companion program should
*
be started before executing this program.
*

* Inputs:
*
* Outputs:
*
* To compile:
*
* Example:
*
* Comments:
*
*
*
*
*
*
*

device, target address, protocol type, short message.
Exit status.
cc

-0

dli eth dli eth.c

dli_eth qeO 08-00-2b-02-e2-ff 6006 "Echo this"
This example demonstrates the use of the "NORMAL" I/O
control flag.
The use of the "NORMAL" flag means that
we can communicate only with a single specific node
whose address is specified during the bind. Because
of this, we can use the normal write and read system
calls on the socket, because the source/destination of
all data that is read/written on the socket is fixed.

/*
* Digital Equipment Corporation supplies this software example on
* an "as-is" basis for general customer use.
Note that Digital
* does not offer any support for it, nor is it covered under any
* of Digital's support contracts.
*/
main (argc, argv, envp)
int argc;
char **argv, **envp;

B-2

DLI Programming Examples

u char inbuf[1500] , outbuf[1500];
u char target_eaddr[6];
u char devname[16];
int rsize, devunit;
char *cp;
int i, sock;
u_short ptype, obsiz;
if ( argc < 5 )
{

fprintf(stderr, "%s %s %s\n",
"usage:",
argv[O] ,
"device ethernet-address hex-protocol-type short-message");
exit(l);

1* get device name and unit number.
bzero(devname, sizeof(devname»;
i = 0;
cp = argv[l];
while ( isalpha(*cp)
devname[i++] = *cp++;
sscanf(cp, "%d" , &devunit);

1* get phys addr of remote node *1
bzero(target eaddr, sizeof(target_eaddr»;
i = 0;
cp = argv[2];
while ( *cp )
if ( *cp == '-'
cp++;
continue;
else {
sscanf(cp, "%2x", &target_eaddr[i++]);
cp += 2;

1* get protocol type *1
sscanf(argv[3], "%hx", &ptype);

1* get message *1
bzero(outbuf, sizeof(outbuf»;
if ( (obsiz = strlen(argv[4]»
> 1500 )
fprintf(stderr, "%s: message is too long\n", argv[O]);
exit(l);
strcpy(outbuf, argv[4]);

1* open dli socket *1
if ( (sock = dli_econn(devname, devunit, ptype,
target_eaddr, DLI_NORMAL»
perror("dli_eth, dli_econn failed");
exit(l);

< 0 ) {

1* send message to target. minimum message size is 46 bytes.
if ( write (sock, outbuf, (obsiz < 46 ? 46
obsiz»
< 0 ) {
sprintf(outbuf, "%s: DLI transmission failed", argv[O]);
perror(outbuf);
exit(2);

DLI Programming Examples

9-3

/* wait for response */
if «rsize = read(sock, inbuf, sizeof(inbuf») < 0 ) {
sprintf(inbuf, "%s: DLI reception failed", argv[O]);
perror(inbuf);
exit(2);
if ( ! rsize ) {
fprintf(stderr,
exit(2);

"%s, no data returned\n", argv[O]);

/* print results */
printf("%s\n", inbuf);
close(sock);

/*
d 1 i

e con n

*
*
*

* Description:
*
This subroutine opens a dli socket, then binds an associated
*
device name and protocol type to the socket.

* Inputs:
*
devname
*
devunit
*
ptype
*
taddr
*
ioctl

ptr to device name
device unit number
protocol type
target address
io control flag

*
*

* Outputs:
returns
*

socket handle if success, otherwise -1

*
*

dli_econn(devname, devunit, ptype, taddr,
char *devname;
u_short devunit;
u_short ptype;
u_char *taddr;
u_char ioctl;

i~ctl)

{

int i, sock;
struct sockaddr_dl out bind;
if

(i = strlen(devname» >
sizeof(out_bind.dli_device.dli_devname)
fprintf(stderr,
return(-l);

)

"dli eth: bad device name");

if «sock = socket (AF_DLI, S OCK_D GRAM , DLPROTO_DLI»
{

perror("dli_eth, can't open DLI socket");
return(-l);

8-4

DLI Programming Examples

< 0)

* fill out bind structure
*/
bzero(&out bind, sizeof(out bind));
out_bind.dli_familY = AF_DLI;
out_bind.dli_substructype = DLI_ETHERNET;
bcopy(devname, out bind.dli device.dli devname, i);
out_bind.dli_device.dli_devnumber = devunit;
out_bind.choose_addr.dli_eaddr.dli_ioctlflg = ioctl;
out bind. choose addr.dli eaddr.dli protype = ptype;
if ( taddr)
bcopy(taddr, out_bind.choose_addr.dli_eaddr.dli_target,
DLI_EADDRSIZE) ;
if

bind(sock, &out_bind, sizeof(out_bind)) < 0 )

{

perror(IIdli_eth, can't bind DLI socket");
return(-l);
return (sock) ;

DLI Programming Examples

8-5

B.2 Sample DLI Server Program Using Ethernet Format Packets
#ifndef lint
static char
#endif lint

*sccsid

"@(#)dli_ethd.c

1.6

3/27/90";

#include <stdio.h>
#include <ctype.h>
#include <errno.h>
#include <strings.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/if ether.h>
#include <netdnet/dli var.h>
#include <sys/ioctl.h>
extern int errno;

*
*
*

d l i e x amp I e : d 1 i

* Description:
*
*
*

* Inputs:

* Outputs:

* To compile:

* Example:

* Comments:

*
*
*
*
*
*

e t h d

This daemon program transmits any message it receives
to the originating node, that is, it echoes the message.
The device and protocol type are supplied by
the user.
The program uses Ethernet format packets.
device, protocol type.
Exit status.
cc

-0

dli ethd dli ethd.c

dli ethd deO 6006
This example demonstrates the use of the "DEFAULT" I/O
control flag, and the recvfrom & sendto system calls.
By specifying "DEFAULT" when binding the DLI socket to
the device we inform the system that this program will
receive any Ethernet format packet with the given
protocol type that is not meant for any other program
on the system.
Since packets may arrive from
different nodes, we use the recvfrom call to read the
packets.
This call gives us access to the packet
header information so that we can determine where the
packet came from.
When we write on the socket we must
use the sendto system call to explicitly give the
destination of the packet.

8-6

DLI Programming Examples

u char inbuf[1500], outbuf[1500];
u char devname[16];
u char target_eaddr[6];
char *cp;
int rsize, devunit;
int i, sock, fromlen;
u_short ptype, obsiz;
struct sockaddr_dl from;
if ( argc < 3 )
{

fprintf(stderr,
"usage: %s device hex-protocol-type\n", argv[O]);
exit(l);
/* get device name and unit number. */
bzero(devname, sizeof(devname));
i = 0;
cp = argv[l];
while ( isalpha(*cp)
devname[i++] = *cp++;
sscanf (cp, "%d", &devunit);
/* get protocol type */
sscanf(argv[2], "%x", &ptype);
/* open dli socket */
if
((sock = dli_econn(devname, devunit, ptype, NULL, DLI_DEFAULT) )<0)
{

perror("dli_ethd, dli econn failed");
exit(l);
while ( 1 ) {
/* wait for message */
from.dli_family = AF_DLI;
fromlen = sizeof(struct sockaddr dl);
if ((rsize = recvfrom(sock, inbuf, sizeof(inbuf),
NULL, &from, &fromlen)) < 0 ) {
sprintf(inbuf, "%s: DLI reception failed", argv[O]);
perror(inbuf);
exit(2) ;
/* check header */
if ( fromlen != sizeof(struct sockaddr dl) ) {
fprintf(stderr,"%s, incorrect head;r supplied\n",argv[O]);
continue;
/* any data? */
if ( ! rsize )
fprintf(stderr, "%s, NO data received from ", argv[O]);
else
fprintf(stderr, "%s, data received from ", argv[O]);
for ( i = 0; i < 6; i++ )
fprintf (stderr, "%x%s",
from.choose_addr.dli_eaddr.dli target[i],
((i<5)?"-":" "));
fprintf(stderr, "on protocol type %x\n",
from.choose_addr.dli_eaddr.dli_protype);

DLI Programming Examples

8-7

/* send response to originator. */
if ( sendto(sock, inbuf, rsize, NULL, &from, fromlen) < 0 )
sprintf(outbuf, "%s: DLI transmission failed", argv[O));
perror(outbuf);
exit(2);

/*
d 1 i

*
*
*
*

e con n

* Description:
*
This subroutine opens a dli socket, then binds an associated
*
device name and protocol type to the socket.

* Inputs:
*
devname
*
devunit
*
ptype
*
taddr
*
ioctl

ptr to device name
device unit number
protocol type
target address
io control flag

* Outputs:
returns
*

socket handle if success, otherwise -1

*
*

*/
dli_econn(devname, devunit, ptype, taddr, ioctl)
char *devname;
u_short devunit;
u_short ptype;
u_char *taddr;
u_char ioctl;
{

int i, sock;
struct sockaddr_dl out bind;
if

(i = strlen(devname)) >
sizeof(out_bind.dli_device.dli_devname)
fprintf(stderr,
return(-l);

if ((sock

)

"dli ethd: bad device name");

socket (AF_DLI, SOCK DGRAM, DLPROTO DLI)) < 0)

{

perror("dli_ethd, can't open DLI socket");
return(-l);

/*
* fill out bind structure
*/

bzero(&out_bind, sizeof(out_bind));
out_bind.dli_family = AF_DLI;
out bind.dli substructype = DLI ETHERNET;
bcopy(devname, out_bind.dli_device.dli_devname, i) i
out bind.dli device.dli devnumber = devuniti
out=bind.choose_addr.dli_eaddr.dli_ioctlflg = ioctli
out_bind.choose_addr.dli_eaddr.dli_protype = ptype;
if ( taddr )
bcopy(taddr, out_bind.choose_addr.dli_eaddr.dli_target,
DLI_EADDRSIZE) ;

8-8

DLI Programming Examples

bind(sock, &out_bind, sizeof(out_bind»

< 0

{

perror(Ildli_ethd, can't bind DLI socket");
return(-l);
return (sock) ;

DLI Programming Examples

8-9

B.3 Sample DLI Client Program Using 8802-3 Format Packets
#ifndef lint
static char
#endif lint

*sccsid

"@ (#) dli_802. c

1. 7

3/27/90" i

{OxOO, OxOO, OxOO, OxOO, Ox5}
PROTOCOL_IDi

*
*

d 1 i

e x amp I e : d I i

802

* Description: This program sends out a message to a node where a
companion program, dli_802d, echoes the message.
The 8802-3 packet format is used.
The Ethernet
*
address of the node where the companion program is
*
running, the sap, and the message are supplied by the
*
user.
The companion program should be started before
*
executing this program.
*

* Inputs:

* Outputs:

* To compile:

* Example:

* Comments:

*
*
*
*
*
*
*
*
*
*
*
*
*

device, target address, sap, short message.
Exit status.
cc

-0

dli 802 dli 802.c

dli_802 qeO 08-00-2b-02-e2-ff ac "Echo this"
This example demonstrates the use of 802 "TYPEl"
service. With TYPEI service, the processing of
XID and TEST messages is handled transparently by
DLI, that is, this program doesn't have to be concerned
with handling them.
If the SNAP SAP (OxAA) is
selected, a 5-byte protocol id is also required.
This example automatically uses a protocol id
of PROTOCOL_ID when this SNAP SAP is used. Also,
note the use of DLI NORMAL for the i/o control flag.
DLI makes use of this only when that SNAP SAP/Protocol
ID pair is used. DLI filters all incoming-messages
by comparing the Ethernet source address and Protocol
ID against the target address and Protocol ID set up
in the bind call. Only if a match occurs will DLI
pass the message up to the application.

/*
* Digital Equipment Corporation supplies this software example on
* an "as-is" basis for general customer use. Note that Digital
* does not offer any support for it, nor is it covered under any
* of Digital's support contracts.
*/

8-10

DLI Programming Examples

main (argc, argv, envp)
int argc;
char **argv, **envp;

u char inbuf[1500], outbuf[1500];
u char target_eaddr[6];
u char devname[16];
int rsize, devunit;
char *cp;
int i, sock, fromlen;
struct sockaddr dl from;
u_short obsiz;
u_int sap;
u_char *pi
0;
if ( argc < 5
{

fprintf (stderr, "%s %s %s\n",
"usage:",
argv[O] ,
"device ethernet-address hex-sap short-message");
exit(l);

/* get device name and unit number. */
bzero(devname, sizeof(devname));
i = 0;
cp = argv[l];
while ( isalpha(*cp)
devname[i++] = *cp++;
sscanf(cp, "%d", &devunit);
/* get phys addr of remote node */
bzero(target_eaddr, sizeof(target_eaddr));
i = 0;
cp = argv[2];
while ( *cp )
if ( *cp == ' - '
cp++;
continue;
else {
sscanf(cp, "%2x", &target_eaddr[i++]);
cp += 2;

/* get sap */
sscanf(argv[3], "%x", &sap);
/* get message */
bzero(outbuf, sizeof(outbuf));
if ( (obsiz = strlen(argv[4])) > 1500 )
fprintf(stderr, "%s: message is too long\n", argv[O]);
exit(2);
strcpy(outbuf, argv[4]);
/* open dli socket. notice that if (and only if) the snap sap */
/* was selected then a protocol id must also be provided. */
if ( sap == SNAP_SAP )
pi = protocolid;
if ( (sock = dli 802_3_conn(devname, devunit, pi, target_eaddr,
DLI NORMAL, TYPE1, sap, sap, UI_NPCMD)) < 0 ) {
perror("dli_802,-dli econn failed");
exit (3) ;

DLI Programming Examples

8-11

/* send message to target. minimum message size is 46 bytes. */
if ( write (sock, outbuf, (obsiz < 46 ? 46 : obsiz»
< 0 ) {
sprintf(outbuf, "%s: DLI transmission failed", argv[O]);
perror(outbuf);
exit (4) ;

/* wait for response from correct address */
while (1)
bzero(&from, sizeof(from»;
from.dli_family = AF_DLI;
fromlen = sizeof(struct sockaddr_dl);
if ((rsize = recvfrom(sock, inbuf, sizeof(inbuf),
NULL, &from, &fromlen»
< 0 ) {
sprintf(inbuf, "%s: DLI reception failed", argv[O]);
perror(inbuf);
exit(5);

fromlen!= sizeof(struct sockaddr_dl) ) {
fprintf(stderr,"%s, invalid address size\n",argv[O]);
exit(6);

bcmp(from.choose_addr.dli 802addr.eh 802.dst,
target_eaddr, sizeof(target_eaddr»
== 0
break;

( ! rsize ) {
fprintf(stderr,
exit(7);

"%s, no data returned\n" , argv[O]);

}

/* print message */
printf("%s\n", inbuf);
close(sock);

/*
d 1 i
802
con n
3
*
*
*
*
* Description:
*
This subroutine opens a dli 8802-3 socket and then binds an
*
associated device name and protocol type to the socket.
*
* Inputs:
ptr to device name
*
devname
device unit number
*
devunit
protocol type
*
ptype
target address
*
taddr
ioctl
io control flag
*
svc
service class
*
sap
source sap
*
dsap
destination sap
*
ctl
control field
*
*
*
* Outputs:
socket handle if success, otherwise -1
returns
*
*
*
*/

8-12

DLI Programming Examples

dli_S02_3_conn (devname,devunit,ptype,taddr,ioctl,svc,sap,dsap,ctl)
char *devname:
u_short devunit:
u char *ptype:
u char *taddr:
u char ioctl:
u char svc:
u char sap:
u_char dsap:
u_short ctl;
int i, sock;
struct sockaddr_dl out_bind;
if

(i = strlen(devname)) >
sizeof(out_bind.dli_device.dli_devname)
fprintf(stderr,
return(-l);

)

"dli S02: bad device name");

if «sock = socket (AF_DLI, SOCK DGRAM, DLPROTO DLI)) < 0)
{

perror("dli_S02, can't open DLI socket");
return(-l):
/*
* fill out bind structure. note that we need to determine
* whether the ctl field is S bits (unnumbered format) or
* 16 bits (informational/supervisory format) . We do this
* by checking the low order 2 bits, which are both 1 only
* for unnumbered control fields.
*/
bzero(&out_bind, sizeof(out_bind)):
out bind.dli family = AF DLI:
out_bind.dli_substructype = DLI S02;
bcopy(devname, out_bind.dli_devlce.dli_devname, i):
out bind.dli device.dli devnumber = devunit:
out-bind.choose addr.dll S02addr.ioctl = ioctl:
out-bind.choose-addr.dli-S02addr.svc = svc:
if(ctl & 3)
out_bind.choose addr.dli S02addr.eh_S02.ctl.U_fmt=(u_char)ctl;
else
out_bind. choose addr.dli S02addr.eh_S02.ctl.I_S_fmt = ctl;
out_bind.choose_addr.dli_S02addr.eh_S02.ssap
sap:
out bind.choose addr.dli S02addr.eh S02.dsap = dsap;
if ( ptype)
bcopy(ptype,out_bind.choose_addr.dli_S02addr.eh_S02.osi_pi,S):
if ( taddr )
bcopy(taddr, out_bind.choose_addr.dli_802addr.eh_802.dst,
DLI EADDRSIZE):
if
bind(sock~ &out_bind, sizeof(out_bind)) < 0 )
{

perror("dli 802, can't bind DLI socket"):
return(-l);
return (sock) ;

DLI Programming Examples

8-13

8.4 Sample DLI Server Program Using 8802-3 Format Packets
#ifndef lint
static char
#endif lint

*sccsid

"@(#)dli_802d.c

1.6

3/27/90";

{OxOO, OxOO, OxOO, OxOO, Ox5}
PROTOCOL_ID;

*
*

d l i e x amp I e

* Description:
*
*
*

* Inputs:

* Outputs:

* To compile:

* Example:

* Comments:

*
*
*
*

*
*
*

d I i

8 0 2 d

This daemon program transmits any message it receives
to the originating node, that is, it echoes the message.
The device and sap are supplied by the user.
The program uses 8802-3 format packets.
device, sap.
Exit status.
cc

-0

dli 802d dli 802d.c

dli 802d deO ac
This example demonstrates the recvfrom and sendto system
calls.
Since packets may arrive from different nodes,
we use the recvfrom call to read the packets. This
call gives us access to the packet header information
so that we can determine where the packet came from.
When we write on the socket, we must use the sendto
system call to explicitly give the destination of
the packet. The use of the "DEFAULT" I/O control flag
only has an affect when the SNAP SAP is used.
When the SNAP SAP is used, any arriving packets that
have the specified protocol id and that are not
destined for some other program will be given to this
program.

8-14

DLI Programming Examples

u char inbuf[1500] , outbuf[1500];
u char devname[16];
u char target_eaddr[6J;
char *cp;
int rsize, devunit;
int i, sock, fromlen;
u_short obsiz;
u_char tmpsap, sap;
struct sockaddr dl from;
u char *pi = 0;
if ( argc < 3 )
{

fprintf(stderr,
exit(l);

"usage: %s device hex-sap\n", argv[O]);

/* get device name and unit number. */
bzero(devname, sizeof(devname»;
i = 0;
cp = argv[l];
while ( isalpha(*cp)
devname[i++] = *cp++;
sscanf(cp, "%d", &devunit);
/* get sap */
sscanf (argv [2],

"%x", &sap);

/* open dli socket. note that if (and only if) the snap sap */
/* was selected then a protocol id must also be specified. */
if ( sap == SNAP_SAP )
pi = protocolid;
if «sock = dli_802_3_conn(devname, devunit, pi, target_eaddr,
DLI_DEFAULT, TYPE1, sap, sap, UI_NPCMD»
< 0) {
perror( dli_802d, dli conn failed");
exit(l);
lt

/* listen and respond */
while ( 1 ) {
/* wait for message */
from.dli_family = AF_DLI;
fromlen = sizeof(struct sockaddr dl);
if «rsize = recvfrom(sock, inbuf, sizeof(inbuf), NULL,
&from, &fromlen»
< 0 ) {
sprintf(inbuf, "%s: DLI reception failed", argv[O]);
perror(inbuf);
exit(2) ;
/* check header */
if ( fromlen != sizeof(struct sockaddr dl) )
fprintf(stderr,"%s, incorrect header supplied\n",argv[O]);
continue;

/*
* Note that DLI swaps the source and destination saps and Ian
* addresses in the sockaddr dl structure returned by the
* recvfrom call. That is, It places the DSAP in eh_802.ssap
* and the SSAP in eh_802.dsap; it also places the destination
* Ian address in eh 802.src and the source Ian address in
* eh 802.dst. This allows for minimal manipulation of
* the address structure for subsequent sendto or dli
* connection calls.
*/

DLI Programming Examples

8-15

/* any data? */
if ( ! rsize )
fprintf(stderr, "%s: NO data received from ", argv[O]);
else
fprintf(stderr, "%s: data received ftom ", argv[O));
for ( i = 0; i < 6; i++ )
fprintf (stderr, "%x%s",
from.choose_addr.dli_802addr.eh 802.dst[i),
((i<5)?"-":" "));
fprintf (stderr, "\n
on dsap %x ",
from.choose addr.dli 802addr.eh 802.ssap);
if ( from. choose addr.dli 802addr.eh 802.dsap == SNAP SAP
fprintf(stderr,
II
,
"(SNAP SAP), protocol id = %x-%x-%x-%x-%x\n
from.choose_addr.dli_802addr.eh_802.os i -pi[O] ,
from.choose_addr.dli_802addr.eh_802.os i -pi[1) ,
from.choose addr.dli 802addr.eh 802.osi pi[2),
from.choose=addr.dli=802addr.eh=802.osi~i[3],
from.choose addr.dli 802addr.eh 802.osi pi[4]);
fprintf(stderr, II from ;sap %x II~
from.choose addr.dli 802addr.eh 802.dsap);
fprintf(stderr, "\n\n");
/* send response to originator. */
if ( from.choose_addr.dli_802addr.eh_802.dsap == SNAP SAP
bcopy(protocolid,
from.choose addr.dli 802addr.eh 802.osi pi, 5);
if ( sendto(sock, inbuf, rsize~ NULL, &from, fromlen) < 0 ) {
sprintf(outbuf, "%s: DLI transmission failed", argv[O));
perror(outbuf);
exit(2);

/*
d 1 i

*
*

802

con n

*
* Description:
*
This subroutine opens a dli 8802-3 socket and then binds an
*
associated device name and protocol type to the socket.
*
* Inputs:
devname
ptr to device name
*
device unit number
devunit
*
protocol type
ptype
*
*.

taddr

ioctl
*
svc
*
sap
*
dsap
*
ctl
*
*
*
* Outputs:
returns
*
*
*

8-16

DLI Programming Examples

target address
io control flag
service class
source sap
destination sap
control field

socket handle if success, otherwise -1

dli_S02_3_conn (devname,devunit,ptype,taddr,ioctl,svc,sap,dsap,ctl)
char *devname;
u_short devunit;
u_char *ptype;
u_char *taddr;
u char ioctl;
u char svc;
u char sap;
u_char dsap;
u_short ctl;
{

int i, sock;
struct sockaddr_dl out bind;
if

(i = strlen(devname)) >
sizeof(out_bind.dli_device.dli_devname)
fprintf(stderr,
return(-l);

)

"dli S02d: bad device name");

if «sock = socket (AF_DLI, SOCK DGRAM, DLPROTO DLI)) < 0)
{

perror("dli_S02d, can't open DLI socket");
return(-l);

/*
* fill out bind structure. note that we need to determine
* whether the ctl field is S bits (unnumbered format) or
* 16 bits (informational/supervisory format) . We do this
* by checking the low order 2 bits, which are both 1 only
* for unnumbered control fields.
*/
bzero(&out bind, sizeof(out bind));
out bind.dli family = AF DLI;
out-bind.dli-substructype = DLI S02;
bzero(&out bind, sizeof(out bind));
out bind.dli family = AF DLI;
out=bind.dli=substructype = DLI_S02;
bcopy(devname, out bind.dli device.dli devname, i);
out_bind.dli_device.dli_dev~umber = de~unit;
out bind. choose addr.dli S02addr.ioctl = ioctl;
out-bind.choose-addr.dli-S02addr.svc = svc;
if(ctl & 3)
out_bind.choose_addr.dli 802addr.eh_802.ctl.U_fmt=(u_char)ctl;
else
out_bind.choose_addr.dli_802addr.eh_802.ctl.I_S_fmt = ctl;
out_bind.choose_addr.dli_802addr.eh_802.ssap
sap;
out bind.choose addr.dli 802addr.eh 802.dsap = dsap;
if ( ptype)
bcopy(ptype,out_bind.choose_addr.dli_802addr.eh_802.osi_pi,5);
if ( taddr )
bcopy(taddr, out_bind.choose_addr.dli_802addr.eh_802.dst,
DLI_EADDRSIZE);
if

bind(sock, &out_bind, sizeof(out_bind)) < 0

{

perror("dli_802d, can't bind DLI socket");
return(-l);
return (sock) ;

DLI Programming Examples

8-17

8.5 Sample DLI Program Using getsockopt and setsockopt
#ifndef lint
static char
#endif lint

*sccsid

"@(#)dli_setsockopt.c

1.5

3/27/90";

{OxOO, OxOO, OxOO, OxOO, Ox5}
{Oxab, OxOO, Ox04, OxOO, OxOO, OxOO}
{Oxab, OxOO, Ox04, OxOO, OxOO, OxOl}

u char mcastO[] = CUSTOMERO;
u char mcastl[] = CUSTOMERl;
u char protocolid[] = PROTOCOL ID;
/*

d l i e x amp 1 e : d l i s e t s o c k

P t

* Description: This program demonstrates the use of the DLI get
*
and setsockopt calls.
It opens a socket, enables
*
2 multicast addresses, changes the 802 control
*
field, enables a number of group saps supplied by
*
the user, and reads the group saps that are enabled.

* Inputs:

* Outputs:

* To compile:

* Example:

* Comments:

*
*
*
*
*
*

device, sap, group-saps.
Exit status.
cc

-0

dli setsockopt dli setsockopt.c

dli_setsockopt qeO ac

5 9 d

When a packet arrives with a group dsap, all dli
programs that have that group sap enabled will
receive copies of that packet.
Group saps are
those with the low order bit set. Group sap 1
is currently not allowed for customer use. Group
saps with the second bit set (eg 3,7,etc) are
reserved by IEEE.

/*
* Digital Equipment Corporation supplies this software example on
* an "as-is" basis for general customer use. Note that Digital
* does not offer any support for it, nor is it covered under any
* of Digital's support contracts.
*/

main (argc, argv, envp)
int argc;
char **argv, **envp;

8-18

DLI Programming Examples

u char inbuf[1500] , outbuf[1500];
u char devname[16];
u char target_eaddr[6];
char *cp;
int rsize, devunit;
int i, j, k, sock, fromlen;
u_short obsiz;
u_char tmpsap, sap;
struct sockaddr_dl from;
u char *pi = 0;
u_char out_opt [1000] , in_opt[lOOO];
int optlen, ioptlen
sizeof(in_opt);
if ( argc < 4 )
{

fprintf(stderr,
argv [0] ) ;
exit(l);

"usage: %s device hex-sap hex-groupsaps\n",

/* get device name and unit number. */
bzero(devname, sizeof(devname»;
i = 0;
cp = argv[l];
while ( isalpha(*cp)
devname[i++] = *cp++;
sscanf(cp, "%d" , &devunit);
/* get protocol type */
sscanf(argv[2], "%x", &sap);
/* open dli socket */
if ( sap == SNAP_SAP )
fprintf (stderr,
"%s: can't use SNAP SAP in USER mode\n", argv[O]);
exit (1) ;
if ( (sock = dli_802_3_conn(devname, devunit, pi, target_eaddr,
DLI_DEFAULT, USER, sap, sap, UI_NPCMD»
< 0 ) {
perror("dli setsockopt: dli conn failed");
exit (1) ;
/* enable two multicast addresses */
bcopy(mcastO, out_opt, sizeof(mcastO»;
bcopy(mcastl, out_opt+sizeof(mcastO), sizeof(mcast1»;
if ( setsockopt(sock, DLPROTO_DLI, DLI_MULTICAST, &out_opt [0] ,
(sizeof (mcastO) + sizeof (mcastl) » < 0 ) {
perror("dli setsockopt: can't enable multicast");
/* set 802 control field */
out_opt [0] = TEST_PCMD;
optlen = 1;
if
(setsockopt(sock,DLPROTO_DLI,DLI SET802CTL,&out opt[O],optlen)<O)S () {
perror("dli setsockopt: Can't set 802 control");
exit(l);

DLI Programming Examples

8-19

/* enable GSAPs supplied by user */
j = 3;
i = 0;
while (j < argc ) {
sscanf (argv [j++],
out_opt [i++] = k;

"%X", &k);

optlen = i;
if
(setsockopt(sock,DLPROTO DLI,DLI ENAGSAP,&out opt[O],optlen) < 0) {
perror("dli setsockopt: Can't enable gsap");
exit(l);
-

/* verify all gsaps are enabled */
bzero (in opt, (ioptlen = sizeof (in_opt)
if
(getsockopt(sock,DLPROTO DLI,DLI GETGSAP,in opt,&ioptlen) < 0) {
perror("dli setsockopt: DLI getsockopt 2" failed");
exit(l);
-

»;

printf(" number of enabled GSAPs
for(i = 0; i < ioptlen; i++) {
if ( ! (i % 10) )
printf ("\n");
printf("%2x ",in_opt[i]);

%d, GSAPS:", ioptlen);

printf ("\n");

/* disable all but the last 4 or all GSAPs, */
/* whichever is smallest */
if ( opt len > 4 )
optlen -= 4;
if
(setsockopt(sock,DLPROTO_DLI,DLI_DISGSAP,&out_opt[O],optlen) < 0) {
perror("dli_setsockopt: Can't disable gsap");
/* verify some gsaps still enabled */
bzero (in opt, (ioptlen = sizeof (in opt»);
if
(getsockopt(sock,DLPROTO DLI,DLI_GETGSAP,in_opt,&ioptlen) < 0) {
perror(IIdli_setsockopt: getsockopt 3 failed");
exit(l);
printf(IInumber of enabled GSAPs
for(i = 0; i < ioptlen; i++) {
if ( ! (i % 10) )
printf ("\n");
printf("%2x ",in_opt[i]);
printf ("\n");

8-20

DLI Programming Examples

%d, GSAPS:",

ioptlen);

/*
d 1 i

*
*
*
*

802

con n

* Description:
*
This subroutine opens a dli 8802-3 socket and then binds an
*
associated device name and protocol type to it.
*
* Inputs:
devname
*
ptr to device name
devunit
*
device unit number
*
ptype
protocol type
*
taddr
target address
*
ioctl
io control flag
*
svc
service class
*
sap
source sap
dsap
*
destination sap
*
ctl
control field

*
*

* Outputs:
returns
*

socket handle if success, otherwise -1

*
*

*/
dli_802_3_conn (devname,devunit,ptype,taddr,ioctl,svc,sap,dsap,ctl)
char *devname;
u_short devunit;
u char *ptype;
u char *taddr;
u char ioctl;
u char svc;
u char sap;
u_char dsap;
u short ctl;
{

int i, sock;
struct sockaddr_dl out_bind;
if

(i = strlen(devname)) >
sizeof(out_bind.dli_device.dli_devname)
fprintf(stderr,
return(-l);

)

Ildli_setsockopt: bad device name");

if ((sock = socket (AF_DLI, SOCK DGRAM, DLPROTO_DLI)) < 0)
{

perror("dli setsockopt: can't open DLI socket");
return(-l);

DLI Programming Examples

8-21

* fill out bind structure
*/
bzero(&out bind, sizeof(out bind»;
out bind.dli family = AF DLI;
out=bind.dli=substructype = DLI_802;
bcopy(devname, out_bind.dli_device.dli_devname, i);
out_bind.dli_device.dli_devnumber = devunit;
out_bind.choose_addr.dli_802addr.ioctl = ioctl;
out_bind.choose_addr.dli_802addr.svc = svc;
if(ctl & 3)
out_bind.choose_addr.dli 802addr.eh 802.ctl.U fmt=(u_char)ctl;
else
out_bind.choose_addr.dli 802addr.eh_802.ctl.I_S_fmt = ctl;
out_bind.choose_addr.dli_802addr.eh_802.ssap
sap;
out bind.choose addr.dli 802addr.eh 802.dsap = dsap;
if ( ptype)
bcopy(ptype,out_bind.choose_addr.dli_802addr.eh_802.osi_pi,5);
if ( taddr )
bcopy(taddr, out_bind.choose_addr.dli_802addr.eh_802.dst,
DLI_EADDRSIZE) ;
if ( bind(sock, &out_bind, sizeof(out_bind»
< 0 )
{

perror("dli_setsockopt: can't bind DLI socket");
return (-1) ;
return (sock) ;

8-22

DLI Programming Examples

Index
A

Address family,
specifying the, 3-2

Error recovery,
providing, 1-2,3-1
Ethernet,
accessing, 1-2
address, 1-2
multiple users, 1-2
transmitting messages on, 1-2
Ethernet frame structure,
example of, 2-3
function of, 2-4
specifying target node informatfon, 2-3
Ethernet substructure,
filling the, 3-5
frame structure, 2-3
sending and receiving, 2-2
values, 2-4
Exchange Identification,
definition of, 2-8
function of, 2-8

8
bind system call,
using, 2-1, 2-4
Buffer size,
calculating, 3-7

c
Concurrent programs,
running, 1-1
Control field,
function of, 2-8

D
Datagram socket,
creating a, 3-2
using, 1-3
Data Link Interface,
definition of, 1-1
Data segmentation,
providing, 1-2, 3-1
Data Transfer,
using DLI program, 3-7
Destination Service Access Point,
definition of, 2-7
DLI address family,
specifying the, 3-2
DLI program,
transferring data, 3-7
writing, 3-1
DLI protocol module,
specifying the, 3-2
DLI Services,
examples of, 1-1
dIL802_3_conn subroutine,
example, B-17
using, 2-2
dli_econn subroutine,
example, B-5
using, 2-2
Domain,
specifying the, 2-1
DSAP,
definition of, 2-7

F
Flow control,
providing, 1-2, 3-1
Frame format,
802, 1-3
description of 8802-3, 2-5
Ethernet, 1-3, 2-3
example of 8802-3, 2-6
proceSSing 8802-3, 2-6
standard, 1-3
Frames,
building, 1-2

G
Guaranteed delivery,
providing, 1-2

H
Hardware support,
examples of, 1-2
High-Level services,
providing, 1-2, 3-1

1\0 control flags,
functions of, 2-4

Index-1

L
LLC,
sublayer of DU, 2-6
LLC Protocol Data Unit Test,
definition of, 2-8
function of, 2-8
Logical Link Control (LLC),
definition, 1-3
sublayer of DU, 2-6

M
Multicast address,
using, 1-3, 2-4
Multiple users,
on Ethernet, 1-2

Socket options, (Cont.)
setting, 3-3
socket system call,
using, 3-2
SSAP,
definition of, 2-7
Standard frame formats,

802, 1-3
Ethernet, 1-3
Subroutines,
using, 2-2
802 substructure,
filling in, 2-1
sending and receiving, 2-2
8802-3 substructure,
filling the, 3-6
Substructures,

8802-3, 2-5

N
Network device,
specifying the, 2-1

p
Packet routing,
providing, 1-2
Physical address,
using, 1-3, 2-4
Prerequisites,
for DU programming, 1-2
Privileges,
superuser, 1-2
Protocol type,
definition, 2-4

R
recvfrom system call,
using, 2-4

s
sendto system call,
'Using, 2-1,2-4
Service class,
definition of, 2-6
values, 2-6
Services,
providing high-level, 3-1
SNAP_SAP,
using, 2-7
sockaddr_dl data structure,
explanation of, 2-1
filling in, 2-1
function of, 2-1
using system calls to fill, 2-1
Socket,
binding the, 3-4
creating a, 3-2
deactivating, 3-7
Socket address data structure,
explanation of, 2-1
filling in, 2-1, 3-2
function of, 2-1
using system calls to fill, 2-1
Socket options,

Index-2

Ethernet frame structure, 2-3
filling in, 2-1
sending and receiving, 2-2
8802-3 substructure values,
control field, 2-8
destination service access point, 2-7
exchange identification, 2-8
LLC Protocol Data Unit Test, 2-8
Service class, 2-6
source service access point, 2-7
target node physical address, 2-6
Unnumbered Information Command, 2-9
XID, 2-8
System calls,
bind, 3-2
calling sequence, 3-2
close, 3-2
read, 3-2
recv, 3-2
recvfrom, 3-2
send, 3-2
sendto, 3-2
socket, 3-2
specifying values with, 2-1
summary of, 3-2
used to transfer data, 3-7
using, 3-1
write, 3-2

T
Target node,
specifying information, 2-3
Target node physical address,
definition of, 2-4, 2-6
. specifying, 2-4

u
Unnumbered Information Command,
definition of, 2-9
function of, 2-9

x
XID,
definition of, 2-8
function of, 2-8

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