File: iftab.5

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.\" Jean II - HPL - 2004-2007
.\" iftab.5
.\"
.TH IFTAB 5 "26 February 2007" "wireless-tools" "Linux Programmer's Manual"
.\"
.\" NAME part
.\"
.SH NAME
iftab \- static information about the network interfaces
.\"
.\" DESCRIPTION part
.\"
.SH DESCRIPTION
The file
.B /etc/iftab
contains descriptive information about the various network interfaces.
.B iftab
is only used by the program
.IR ifrename (8)
to assign a consistent network interface name to each network interface.
.PP
.B /etc/iftab
defines a set of
.IR mappings .
Each mapping contains an interface name and a set of selectors. The
selectors allow
.B ifrename
to identify each network interface on the system. If a network
interface matches all descriptors of a mapping,
.B ifrename
attempt to change the name of the interface to the interface name
given by the mapping.
.\"
.\" MAPPINGS part
.\"
.SH MAPPINGS
Each mapping is described on a separate line, it starts with an
.IR "interface name" ,
and contains a set of
.IR descriptors ,
separated by space or tabs.
.PP
The relationship between descriptors of a mapping is a
.IR "logical and" .
A mapping matches a network interface only is all the descriptors
match. If a network interface doesn't support a specific descriptor,
it won't match any mappings using this descriptor.
.PP
If you want to use alternate descriptors for an interface name
(logical or), specify two different mappings with the same interface
name (one on each line).
.B Ifrename
always uses the last matching mapping in iftab.
.\"
.\" INTERFACE NAME part
.\"
.SH INTERFACE NAME
The first part of each mapping is an interface name. If a network
interface matches all descriptors of a mapping,
.B ifrename
attempt to change the name of the interface to the interface name
given by the mapping.
.PP
The interface name of a mapping is either a plain interface name (such as
.IR eth2 " or " wlan1 )
or a interface name pattern containing a single wildcard (such as
.IR eth* " or " wlan* ).
In case of wildcard, the kernel replace the '*' with the lowest
available integer making this interface name unique. Note that
wildcard is only supported for kernel 2.6.1 and 2.4.30 and later.
.PP
It is discouraged to try to map interfaces to default interfaces names
such as
.IR eth0 ", " wlan0 " or " ppp0 .
The kernel use those as the default name for any new interface,
therefore most likely an interface will already use this name and
prevent ifrename to use it. Even if you use takeover, the interface
may already be up in some cases. Not using those name will allow you
to immediately spot unconfigured or new interfaces.
.br
Good names are either totally unique and meaningfull,
such as
.IR mydsl " or " privatehub ,
or use larger integer, such as
.IR eth5 " or " wlan5 .
The second type is usually easier to integrate in various network utilities.
.\"
.\" DESCRIPTORS part
.\"
.SH DESCRIPTORS
Each descriptor is composed of a descriptor name and descriptor
value. Descriptors specify a static attribute of a network interface,
the goal is to uniquely identify each piece of hardware.
.PP
Most users will only use the
.B mac
selector despite its potential problems, other selectors are for more
specialised setup. Most selectors accept a '*' in the selector value
for wilcard matching, and most selectors are case insensitive.
.TP
.BI mac " mac address"
Matches the MAC Address of the interface with the specified MAC
address. The MAC address of the interface can be shown using
.IR ifconfig (8)
or
.IR ip (8).
.br
This is the most common selector, as most interfaces have a unique MAC
address allowing to identify network interfaces without ambiguity.
However, some interfaces don't have a valid MAC address until they are
brought up, in such case using this selector is tricky or impossible.
.TP
.BI arp " arp type"
Matches the ARP Type (also called Link Type) of the interface with the
specified ARP type as a number. The ARP Type of the interface can be
shown using
.IR ifconfig (8)
or
.IR ip (8),
the
.B link/ether
type correspond to
.B 1
and the
.B link/ieee802.11
type correspond to
.BR 801 .
.br
This selector is useful when a driver create multiple network
interfaces for a single network card.
.TP
.BI driver " driver name"
Matches the Driver Name of the interface with the specified driver
name. The Driver Name of the interface can be shown using
.IR "ethtool -i" (8).
.TP
.BI businfo " bus information"
Matches the Bus Information of the interface with the specified bus
information. The Bus Information of the interface can be shown using
.IR "ethtool -i" (8).
.TP
.BI firmware " firmware revision"
Matches the Firmware Revision of the interface with the firmware
revision information. The Firmware Revision of the interface can be
shown using
.IR "ethtool -i" (8).
.TP
.BI baseaddress " base address"
Matches the Base Address of the interface with the specified base
address. The Base Address of the interface can be shown using
.IR ifconfig (8).
.br
Because most cards use dynamic allocation of the Base Address, this
selector is only useful for ISA and EISA cards.
.TP
.BI irq " irq line"
Matches the IRQ Line (interrupt) of the interface with the specified
IRQ line. The IRQ Line of the interface can be shown using
.IR ifconfig (8).
.br
Because there are IRQ Lines may be shared, this selector is usually
not sufficient to uniquely identify an interface.
.TP
.BI iwproto " wireless protocol"
Matches the Wireless Protocol of the interface with the specified
wireless protocol. The Wireless Protocol of the interface can be shown
using
.IR iwconfig (8)
or
.IR iwgetid (8).
.br
This selector is only supported on wireless interfaces and is not
sufficient to uniquely identify an interface.
.TP
.BI pcmciaslot " pcmcia slot"
Matches the Pcmcia Socket number of the interface with the specified
slot number. Pcmcia Socket number of the interface can be shown
using
.IR "cardctl ident" (8).
.br
This selector is usually only supported on 16 bits cards, for 32 bits
cards it is advised to use the selector
.BR businfo .
.TP
.BI prevname " previous interface name"
Matches the name of the interface prior to renaming with the specified
oldname.
.br
This selector should be avoided as the previous interface name may
vary depending on various condition. A system/kernel/driver update may
change the original name. Then, ifrename or another tool may rename it
prior to the execution of this selector.
.TP
.BI SYSFS{ filename } " value"
Matches the content the sysfs attribute given by filename to the
specified value. For symlinks and parents directories, match the
actual directory name of the sysfs attribute given by filename to the
specified value.
.br
A list of the most useful sysfs attributes is given in the next
section.
.\"
.\" SYSFS DESCRIPTORS part
.\"
.SH SYSFS DESCRIPTORS
Sysfs attributes for a specific interface are located on most systems
in the directory named after that interface at
.IR /sys/class/net/ .
Most sysfs attribute are files, and their values can be read using
.IR cat "(1) or " more (1).
It is also possible to match attributes in subdirectories.
.PP
Some sysfs attributes are symlinks, pointing to another directory in
sysfs. If the attribute filename is a symlink the sysfs attribute
resolves to the name of the directory pointed by the symlink using
.IR readlink (1).
The location is a directory in the sysfs tree is also important. If
the attribute filename ends with
.IR /.. ,
the sysfs attribute resolves to the real name of the parent directory
using
.IR pwd (1).
.PP
The sysfs filesystem is only supported with 2.6.X kernel and need to
be mounted (usually in 
.IR /sys ).
sysfs selectors are not as efficient as other selectors, therefore
they should be avoided for maximum performance.
.PP
These are common sysfs attributes and their corresponding ifrename
descriptors.
.TP
.BI SYSFS{address} " value"
Same as the
.B mac
descriptor.
.TP
.BI SYSFS{type} " value"
Same as the
.B arp
descriptor.
.TP
.BI SYSFS{device} " value"
Valid only up to kernel 2.6.20. Same as the
.B businfo
descriptor.
.TP
.BI SYSFS{..} " value"
Valid only from kernel 2.6.21. Same as the
.B businfo
descriptor.
.TP
.BI SYSFS{device/driver} " value"
Valid only up to kernel 2.6.20. Same as the
.B driver
descriptor.
.TP
.BI SYSFS{../driver} " value"
Valid only from kernel 2.6.21. Same as the
.B driver
descriptor.
.TP
.BI SYSFS{device/irq} " value"
Valid only up to kernel 2.6.20. Same as the
.B irq
descriptor.
.TP
.BI SYSFS{../irq} " value"
Valid only from kernel 2.6.21. Same as the
.B irq
descriptor.
.\"
.\" EXAMPLES part
.\"
.SH EXAMPLES
# This is a comment
.br
eth2		mac 08:00:09:DE:82:0E
.br
eth3		driver wavelan interrupt 15 baseaddress 0x390
.br
eth4		driver pcnet32 businfo 0000:02:05.0
.br
air*		mac 00:07:0E:* arp 1
.br
myvpn	SYSFS{address} 00:10:83:* SYSFS{type} 1
.br
bcm*		SYSFS{device} 0000:03:00.0 SYSFS{device/driver} bcm43xx
.br
bcm*		SYSFS{..} 0000:03:00.0 SYSFS{../driver} bcm43xx
.\"
.\" AUTHOR part
.\"
.SH AUTHOR
Jean Tourrilhes \- jt@hpl.hp.com
.\"
.\" FILES part
.\"
.SH FILES
.I /etc/iftab
.\"
.\" SEE ALSO part
.\"
.SH SEE ALSO
.BR ifrename (8),
.BR ifconfig (8),
.BR ip (8),
.BR ethtool (8),
.BR iwconfig (8).