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.TH ETHER 3
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.SH NAME
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ether \- Ethernet device
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.SH SYNOPSIS
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.nf
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.B bind -a #l\fIn\fP /net
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.BI /net/ether n /clone
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.BI /net/ether n /addr
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.BI /net/ether n /ifstats
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.BI /net/ether n /stats
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.BI /net/ether n /[0-7]
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.BI /net/ether n /[0-7]/data
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.BI /net/ether n /[0-7]/ctl
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.BI /net/ether n /[0-7]/ifstats
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.BI /net/ether n /[0-7]/stats
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.BI /net/ether n /[0-7]/type
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.fi
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.SH DESCRIPTION
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The Ethernet interface,
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.BI /net/ether n\f1,
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is a directory
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containing subdirectories, one for each distinct Ethernet packet type,
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and
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.BR clone ,
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.BR addr ,
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.BR ifstats ,
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and
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.B stats
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files.
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.B stats
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and
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.B ifstats
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are the same as in the subdirectories (see below).
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Reading
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.B addr
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returns the MAC address of this interface in hex with no punctuation
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and no trailing newline.
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The number
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.I n
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(optional in the bind)
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is the device number of the card, permitting multiple cards to be used on a single machine.
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.PP
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Each directory contains files to control the associated connection,
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receive and send data,
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and supply statistics.
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Incoming Ethernet packets are demultiplexed by packet type and passed up
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the corresponding open connection.
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Reading from the
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.B data
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file reads packets of that type arriving from the network.
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A read will terminate at packet boundaries.
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Each write to the
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.B data
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file causes a packet to be sent.
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The Ethernet address of the interface is inserted into
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the packet header as the source address.
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.PP
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A connection is assigned to a packet type by opening its
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.B ctl
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file and
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writing
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.B connect
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.I n
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where
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.I n
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is a decimal integer constant identifying the Ethernet packet type.
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A type of \-1 enables the connection to receive copies of packets of
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all types. A type of \-2 enables the connection to receive copies of
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the first 64 bytes of packets of all types.
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If multiple connections are assigned to a given packet type
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a copy of each packet is passed up each connection.
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.PP
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Some interfaces also accept unique options when written to the
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.I ctl
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(or
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.IR clone )
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file; see the description of
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.I wavelan
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in
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.IR plan9.ini (8).
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The control messages described in
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.IR ip (3)
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under
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.B "Configuring interfaces"
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from
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.L bridge
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to
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.L headersonly
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are understood.
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The additional control message
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.L nonblocking
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makes
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.I write
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systems calls to this interface non-blocking iff
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followed by nothing or a non-zero integer;
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a following
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.L 0
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makes
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.I writes
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block on a full output queue.
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.PP
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Reading the
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.B ctl
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file returns the decimal index of the associated connection, 0 through 7.
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Reading the
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.B type
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file returns the decimal value of the assigned Ethernet packet type.
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Reading the
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.B stats
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file returns status information such as the Ethernet address of the
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card and general statistics, independent of the interface;
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.B ifstats
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contains device-specific data and statistics about the card.
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.PP
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An interface normally receives only those packets whose
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destination address is that of the interface or is the
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broadcast address,
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.BR ff:ff:ff:ff:ff:ff .
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The interface can be made to receive all packets on the
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network by writing the string
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.B promiscuous
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to the
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.B ctl
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file.
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The interface remains promiscuous until the control file is
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closed.
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The extra packets are passed up connections only of types \-1
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and \-2.
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.SH SOURCE
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.B /sys/src/9/*/devether.c
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