ETHER(3) ETHER(3)
NAME
ether - Ethernet device
SYNOPSIS
bind -a #ln /net
/net/ethern/clone
/net/ethern/addr
/net/ethern/mtu
/net/ethern/ifstats
/net/ethern/stats
/net/ethern/[0-7]
/net/ethern/[0-7]/data
/net/ethern/[0-7]/ctl
/net/ethern/[0-7]/ifstats
/net/ethern/[0-7]/stats
/net/ethern/[0-7]/type
DESCRIPTION
The Ethernet interface, /net/ethern, is a directory contain-
ing subdirectories, one for each distinct Ethernet packet
type, and clone, addr, mtu, ifstats, and stats files. stats
and ifstats are the same as in the subdirectories (see
below). Reading addr returns the MAC address of this inter-
face in hex with no punctuation and no trailing newline.
Reading mtu returns 3 12-byte numbers: the hardware's mini-
mum MTU, the current MTU and the maximum MTU supported by
the interface. The MTU is set by writing mtu n into the ctl
file. The number n (optional in the bind) is the device
number of the card, permitting multiple cards to be used on
a single machine.
Each directory contains files to control the associated con-
nection, receive and send data, and supply statistics.
Incoming Ethernet packets are demultiplexed by packet type
and passed up the corresponding open connection. Reading
from the data file reads packets of that type arriving from
the network. A read will terminate at packet boundaries.
Each write to the data file causes a packet to be sent. The
Ethernet address of the interface is inserted into the
packet header as the source address unless l2bridge is set.
A connection is assigned to a packet type by opening its ctl
file and writing connect n where n is a decimal integer con-
stant identifying the Ethernet packet type. A type of -1
enables the connection to receive copies of packets of all
types. A type of -2 enables the connection to receive
copies of the first 64 bytes of packets of all types. If
multiple connections are assigned to a given packet type a
copy of each packet is passed up each connection.
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ETHER(3) ETHER(3)
Some interfaces also accept unique options when written to
the ctl (or clone) file; see the description of wavelan in
plan9.ini(8). The control messages described in ip(3) under
Configuring interfaces from `bridge' to `headersonly' are
understood. The additional control message `nonblocking'
makes write systems calls to this interface non-blocking iff
followed by nothing or a non-zero integer; a following `0'
makes writes block on a full output queue.
Reading the ctl file returns the decimal index of the asso-
ciated connection, 0 through 7. Reading the type file
returns the decimal value of the assigned Ethernet packet
type. Reading the stats file returns status information
such as the Ethernet address of the card and general statis-
tics, independent of the interface; ifstats contains
device-specific data and statistics about the card. The
format of the stats file is stat:value.... In particular,
if link is non-zero, mbps is the current speed of the inter-
face in megabits-per-second. While in and out are the total
number of packets input or output and do differ (in the case
of dropped packets or loop back) from hardware counters.
An interface normally receives only those packets whose des-
tination address is that of the interface, the broadcast
address, ff:ff:ff:ff:ff:ff, or a a multicast address
assigned to the interface. Multicast addresses are added by
writing addmulti ea and remove by writing remmulti ea to the
ctl file. Multicast addresses are automatically dropped
when the connection is closed. The interface can be made to
receive all packets on the network by writing the string
promiscuous to the ctl file. The interface remains promiscu-
ous until the control file is closed by all connections
requesting promiscuous mode. The extra packets are passed
up connections of types -1 and -2 only.
Writing bridge to the ctl file causes loop back packets to
be ignored. This is useful for layer 3 bridging. Writing
l2bridge also allows the connection to set the source
address and receive packets with any destination address.
Writing scanbs [ secs ] starts a scan for wireless base sta-
tions and sets the scanning interval to secs. Scanning is
terminated when the connection is closed. The default
interval is 5s. For wired connections, this command is
ignored.
SOURCE
/sys/src/9/*/devether.c
/sys/src/9/port/netif.c
SEE ALSO
ip(3).
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ETHER(3) ETHER(3)
BUGS
The multicast interface makes removal of multicast addresses
on that rely on hashing difficult.
Interface MTU settings must be greater than those used by
ip(3); this is not enforced. NB: interface MTU is different
than IP stack's MTU.
Page 3 Plan 9 (printed 11/18/24)