.TH ETHERNET 4
.CT 2 comm_mach
.SH NAME
ethernet \(mi Ethernet interface
.SH SYNOPSIS
.B #include <sys/enio.h>
.br
.B #include <sys/ethernet.h>
.SH DESCRIPTION
There are drivers for several hardware interfaces to Ethernet.
All have the same programming interface.
.PP
There are eight software channels for each hardware device.
A channel sends and receives packets
for a single Ethernet interface;
hence eight protocols
may be used independently on the same device.
If a channel is open,
it may not be opened again.
.PP
.I Read
and
.I write
deal in Ethernet packets,
consisting of a header
followed by no less than 46
but no more than 1500 bytes of data.
The header,
defined in
.BR <sys/ethernet.h> ,
is as follows:
.LP
.EX
#define	ETHERALEN	6	/* bytes in an ethernet address */

struct etherpup {
	unsigned char dhost[ETHERALEN];	/* destination address */
	unsigned char shost[ETHERALEN];	/* source address */
	unsigned short type;	/* protocol type */
};
.EE
.LP
The protocol type is in the network's byte order,
most significant byte first.
.PP
.I Read
on a channel returns at most one complete packet.
If only part of a packet fits in the
.I read
buffer,
successive reads return the remainder.
.I Write
should be given a single complete packet;
.B dhost
and
.B type
must be filled in.
The system supplies
.BR shost .
.PP
There are a few
.I ioctl
calls,
defined in
.BR <sys/enio.h> :
.TP "\w'ENIOTYPE 'u"
.B ENIOTYPE
The third argument
points to a short integer;
use that as the protocol type for this channel.
.TP
.B ENIOADDR
The third argument
points to a six-character buffer;
copy the hardware address of this interface there.
.PP
Minor device numbers
0-7
are the eight channels of the first hardware device
of a given type;
8-15 are the second device,
and so on.
File names usually end in two digits,
like
.B /dev/il13
for the fourth channel of the second Interlan device.
.SH FILES
.TF /dev/bna??
.TP
.F /dev/il??
Interlan NI1010A devices
.TP
.F /dev/qe??
DEQNA devices
.TP
.F /dev/bna??
DEBNA devices
.SH SEE ALSO
.IR internet (3),
.IR ipconfig (8)
.SH BUGS
The DEQNA driver
fills in the protocol type field
in transmitted packets;
other drivers don't.