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man: describe naming schemes in a new man page

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I decided to make this a separate man page because it is freakin' long.
This content could equally well go in systemd-udevd.service(8), systemd.link(5),
or a new man page for the net_id builtin.

v2:
- rename to systemd.net-naming-scheme
- add udevadm test-builtin net_id example
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2019-05-09 12:34:30 +02:00
parent 87b3c9193d
commit 0b1e5b6ed8
5 changed files with 436 additions and 94 deletions
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1
man/rules/meson.build
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@ -824,6 +824,7 @@ manpages = [
['systemd.kill', '5', [], ''],
['systemd.link', '5', [], ''],
['systemd.mount', '5', [], ''],
['systemd.net-naming-scheme', '7', [], ''],
['systemd.netdev', '5', [], 'ENABLE_NETWORKD'],
['systemd.network', '5', [], 'ENABLE_NETWORKD'],
['systemd.nspawn', '5', [], ''],

18
man/systemd-udevd.service.xml
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@ -171,15 +171,12 @@
<term><varname>net.naming-scheme=</varname></term>
<listitem>
<para>Network interfaces are renamed to give them predictable names when possible (unless
<varname>net.ifnames=0</varname> is specified, see above). The names are derived from various
device metadata fields. Newer versions of <filename>systemd-udevd.service</filename> take more of
these fields into account, improving (and thus possibly changing) the names used for the same
devices. With this kernel command line option it is possible to pick a specific version of this
algorithm. It expects a naming scheme identifier as argument. Currently the following identifiers
are known: <literal>v238</literal>, <literal>v239</literal>, <literal>v240</literal> which each
implement the naming scheme that was the default in the indicated systemd version. In addition,
<literal>latest</literal> may be used to designate the latest scheme known (to this particular
version of <filename>systemd-udevd.service</filename>).</para>
<varname>net.ifnames=0</varname> is specified, see above). With this kernel command line option it
is possible to pick a specific version of this algorithm and override the default chosen at
compilation time. Expects one of the naming scheme identifiers listed in
<citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
or <literal>latest</literal> to select the latest scheme known (to this particular version of
<filename>systemd-udevd.service</filename>).</para>
<para>Note that selecting a specific scheme is not sufficient to fully stabilize interface naming:
the naming is generally derived from driver attributes exposed by the kernel. As the kernel is
@ -188,8 +185,7 @@
</listitem>
</varlistentry>
</variablelist>
<!-- when adding entries here, consider also adding them
in kernel-command-line.xml -->
<!-- when adding entries here, consider also adding them in kernel-command-line.xml -->
</refsect1>
<refsect1>

10
man/systemd.link.xml
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@ -278,6 +278,7 @@
<para>The name is set based on information given by
the firmware for on-board devices, as exported by the
udev property <varname>ID_NET_NAME_ONBOARD</varname>.
See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
</para>
</listitem>
</varlistentry>
@ -287,6 +288,7 @@
<para>The name is set based on information given by
the firmware for hot-plug devices, as exported by the
udev property <varname>ID_NET_NAME_SLOT</varname>.
See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
</para>
</listitem>
</varlistentry>
@ -295,7 +297,9 @@
<listitem>
<para>The name is set based on the device's physical
location, as exported by the udev property
<varname>ID_NET_NAME_PATH</varname>.</para>
<varname>ID_NET_NAME_PATH</varname>.
See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
@ -303,7 +307,9 @@
<listitem>
<para>The name is set based on the device's persistent
MAC address, as exported by the udev property
<varname>ID_NET_NAME_MAC</varname>.</para>
<varname>ID_NET_NAME_MAC</varname>.
See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>

418
man/systemd.net-naming-scheme.xml Normal file
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@ -0,0 +1,418 @@
<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="systemd.net-naming-scheme">
<refentryinfo>
<title>systemd.net-naming-scheme</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.net-naming-scheme</refentrytitle>
<manvolnum>7</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.net-naming-scheme</refname>
<refpurpose>Network device naming schemes</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>Network interfaces may be renamed to give them predictable names when there's enough information to
generate appropriate names and the use of certain types of names is configured. This page describes the
first part, i.e. what possible names may be generated. Those names are generated by the
<citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
builtin <command>net_id</command> and exported as udev properties
(<varname>ID_NET_NAME_ONBOARD=</varname>, <varname>ID_NET_LABEL_ONBOARD=</varname>,
<varname>ID_NET_NAME_PATH=</varname>, <varname>ID_NET_NAME_SLOT=</varname>).</para>
<para>Names are derived from various device metadata attributes. Newer versions of udev take more of
these attributes into account, improving (and thus possibly changing) the names used for the same
devices. Differents version of the naming rules are called "naming schemes". The default naming scheme is
chosen at compilation time. Usually this will be the latest implemented version, but it is also possible
to set one of the older versions to preserve compatibility. This may be useful for example for
distributions, which may introduce new versions of systemd in stable releases without changing the naming
scheme. The naming scheme may also be overriden using the <varname>net.naming-scheme=</varname> kernel
command line switch, see
<citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
Available naming schemes are described below.</para>
<para>After the udev proprties have been generated, appropriate udev rules may be used to actually rename
devices based on those properties. See the description of <varname>NamePolicy=</varname> in
<citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
</refsect1>
<refsect1>
<title>Naming</title>
<para>All names start with a two-character prefix that signifies the interface type.</para>
<table>
<title>Two character prefixes based on the type of interface</title>
<tgroup cols='2'>
<thead>
<row>
<entry>Prefix</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><constant>en</constant></entry>
<entry>Ethernet</entry>
</row>
<row>
<entry><constant>ib</constant></entry>
<entry>InfiniBand</entry>
</row>
<row>
<entry><constant>sl</constant></entry>
<entry>serial line IP (slip)</entry>
</row>
<row>
<entry><constant>wl</constant></entry>
<entry>Wireless local area network (WLAN)</entry>
</row>
<row>
<entry><constant>ww</constant></entry>
<entry>Wireless wide area network (WWAN)</entry>
</row>
</tbody>
</tgroup>
</table>
<para>The udev <command>net_id</command> builtin exports the following udev device properties:</para>
<variablelist>
<varlistentry>
<term><varname>ID_NET_NAME_ONBOARD=<replaceable>prefix</replaceable><constant>o</constant><replaceable>number</replaceable></varname></term>
<listitem><para>This name is set based on the ordering information given by the firmware for
on-board devices. The name consists of the prefix, letter <constant>o</constant>, and a number
specified by the firmware. This is only available for PCI devices.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ID_NET_LABEL_ONBOARD=<replaceable>prefix</replaceable> <replaceable>label</replaceable></varname></term>
<listitem><para>This property is set based on label given by the firmware for on-board devices. The
name consists of the prefix concatenated with the label. This is only available for PCI devices.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ID_NET_NAME_MAC=<replaceable>prefix</replaceable><constant>x</constant><replaceable>AABBCCDDEEFF</replaceable></varname></term>
<listitem><para>This name consists of the prefix, letter <constant>x</constant>, and 12 hexadecimal
digits of the MAC address. It is available if the device has a fixed MAC address. Because this name
is based on an attribute of the card itself, it remains "stable" when the device is moved (even
between machines), but will change when the hardware is replaced.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]</varname></term>
<term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>b</constant><replaceable>number</replaceable></varname></term>
<term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>u</constant><replaceable>port</replaceable>…[<constant>c</constant><replaceable>config</replaceable>][<constant>i</constant><replaceable>interface</replaceable>]</varname></term>
<term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>v</constant><replaceable>slot</replaceable></varname></term>
<listitem><para>This property describes the slot position. Different schemes are used depending on
the bus type, as described in the table below. In all cases, PCI slot information must be known. In
case of USB, BCMA, and SR-VIO devices, the full name consists of the prefix, PCI slot identifier,
and USB or BCMA or SR-VIO slot identifier. The first two parts are denoted as "…" in the table
below.</para>
<table>
<title>Slot naming schemes</title>
<tgroup cols='2'>
<thead>
<row>
<entry>Format</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><replaceable>prefix</replaceable> [<constant>P</constant><replaceable>domain</replaceable>] <constant>s</constant><replaceable>slot</replaceable> [<constant>f</constant><replaceable>function</replaceable>] [<constant>n</constant><replaceable>port_name</replaceable> | <constant>d</constant><replaceable>dev_port</replaceable>]</entry>
<entry>PCI slot number</entry>
</row>
<row>
<entry>… <constant>b</constant><replaceable>number</replaceable></entry>
<entry>Broadcom bus (BCMA) core number</entry>
</row>
<row>
<entry>… <constant>u</constant><replaceable>port</replaceable>… [<constant>c</constant><replaceable>config</replaceable>] [<constant>i</constant><replaceable>interface</replaceable>]</entry>
<entry>USB port number chain</entry>
</row>
<row>
<entry>… <constant>v</constant><replaceable>slot</replaceable></entry>
<entry>SR-VIO slot number</entry>
</row>
</tbody>
</tgroup>
</table>
<para>The PCI domain is only prepended when it is not 0. All multi-function PCI devices will carry
the <constant>f<replaceable>function</replaceable></constant> number in the device name, including
the function 0 device. For non-multi-function devices, the number is suppressed if 0. The port name
<replaceable>port_name</replaceable> is used, or the port number
<constant>d</constant><replaceable>dev_port</replaceable> if the name is not known.</para>
<para>For BCMA devices, the core number is suppressed when 0.</para>
<para>For USB devices the full chain of port numbers of hubs is composed. If the name gets longer
than the maximum number of 15 characters, the name is not exported. The usual USB configuration
number 1 and interface number 0 values are suppressed.</para>
</listitem>
<para>SR-IOV virtual devices are named based on the name of the parent interface, with a suffix of
<constant>v</constant> and the virtual device number, with any leading zeros removed. The bus
number is ignored. This device type is found in IBM PowerVMs.</para>
</varlistentry>
<varlistentry>
<term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable><constant>c</constant><replaceable>bus_id</replaceable></varname></term>
<term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable><constant>a</constant><replaceable>vendor</replaceable><replaceable>model</replaceable><constant>i</constant><replaceable>instance</replaceable></varname></term>
<term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable><constant>i</constant><replaceable>address</replaceable><constant>n</constant><replaceable>port_name</replaceable></varname></term>
<term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>p</constant><replaceable>bus</replaceable><constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>phys_port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]</varname></term>
<term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>p</constant><replaceable>bus</replaceable><constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>phys_port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>b</constant><replaceable>number</replaceable></varname></term>
<term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>p</constant><replaceable>bus</replaceable><constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>phys_port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>u</constant><replaceable>port</replaceable>…[<constant>c</constant><replaceable>config</replaceable>][<constant>i</constant><replaceable>interface</replaceable>]</varname></term>
<listitem><para>This property describes the device installation location. Different schemes are
used depending on the bus type, as described in the table below. For BCMA and USB devices, PCI path
information must known, and the full name consists of the prefix, PCI slot identifier, and USB or
BCMA location. The first two parts are denoted as "…" in the table below.</para>
<table>
<title>Path naming schemes</title>
<tgroup cols='2'>
<thead>
<row>
<entry>Format</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><replaceable>prefix</replaceable> <constant>c</constant><replaceable>bus_id</replaceable></entry>
<entry>CCW or grouped CCW device identifier</entry>
</row>
<row>
<entry><replaceable>prefix</replaceable> <constant>a</constant><replaceable>vendor</replaceable> <replaceable>model</replaceable> <constant>i</constant><replaceable>instance</replaceable></entry>
<entry>ACPI path names for ARM64 platform devices</entry>
</row>
<row>
<entry><replaceable>prefix</replaceable> <constant>i</constant><replaceable>address</replaceable> <constant>n</constant><replaceable>port_name</replaceable></entry>
<entry>Netdevsim (simulated networking device) device number and port name</entry>
</row>
<row>
<entry><replaceable>prefix</replaceable> [<constant>P</constant><replaceable>domain</replaceable>] <constant>p</constant><replaceable>bus</replaceable> <constant>s</constant><replaceable>slot</replaceable> [<constant>f</constant><replaceable>function</replaceable>] [<constant>n</constant><replaceable>phys_port_name</replaceable> | <constant>d</constant><replaceable>dev_port</replaceable>]</entry>
<entry>PCI geographical location</entry>
</row>
<row>
<entry>… <constant>b</constant><replaceable>number</replaceable></entry>
<entry>Broadcom bus (BCMA) core number</entry>
</row>
<row>
<entry>… <constant>u</constant><replaceable>port</replaceable>… [<constant>c</constant><replaceable>config</replaceable>] [<constant>i</constant><replaceable>interface</replaceable>]</entry>
<entry>USB port number chain</entry>
</row>
</tbody>
</tgroup>
</table>
<para>CCW and grouped CCW devices are found in IBM System Z mainframes. Any leading zeros and
dots are suppressed.</para>
<para>For PCI, BCMA, and USB devices, the same rules as described above for slot naming are
used.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>History</title>
<para>The following "naming schemes" have been defined:</para>
<variablelist>
<varlistentry>
<term><constant>v238</constant></term>
<listitem><para>This is the naming naming that was implemented in systemd 238.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>v239</constant></term>
<listitem><para>Naming was changed for virtual network interfaces created with SR-IOV and NPAR and
for devices where the PCI network controller device does not have a slot number associated.</para>
<para>SR-IOV virtual devices are named based on the name of the parent interface, with a suffix of
<literal>v<replaceable>port</replaceable></literal>, where <replaceable>port</replaceable> is the
virtual device number. Previously those virtual devices were named as if completely independent.
</para>
<para>The ninth and later NPAR virtual devices are named following the scheme used for the first
eight NPAR partitions. Previously those devices were not renamed and the kernel default
("eth<replaceable>N</replaceable>") was used.</para>
<para>Names are also generated for PCI devices where the PCI network controller device does not
have an associated slot number itself, but one of its parents does. Previously those devices were
not renamed and the kernel default was used.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>v240</constant></term>
<para>The <literal>ib</literal> prefix and stable names for infiniband devices are
introduced. Previously those devices were not renamed.</para>
<para>The ACPI index field (used in <varname>ID_NET_NAME_ONBOARD=</varname>) is now also used when
0.</para>
<para>A new naming policy <varname>NamePolicy=keep</varname> was introduced. With this policy, if
the network device name was already set by userspace, the device will not be renamed
again. Previously, this naming policy applied implicitly, and now it must be explicitly
requested. Effectively, this means that network devices will be renamed according to the
configuration, even if they have been renamed already, if <constant>keep</constant> is not
specified as the naming policy in the <filename noindex='true'>.link</filename> file. See
<citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for a description of <varname>NamePolicy=</varname>.</para>
</varlistentry>
<varlistentry>
<term><constant>v243</constant></term>
<para>Support for netdevsim (simulated networking devices) was added. Previously those devices were
not renamed.</para>
</varlistentry>
<para>Note that <constant>latest</constant> may be used to denote the latest scheme known (to this
particular version of systemd.</para>
</variablelist>
</refsect1>
<refsect1>
<title>Examples</title>
<example>
<title>Using <command>udevadm test-builtin</command> to display device properties</title>
<programlisting>$ udevadm test-builtin net_id /sys/class/net/enp0s31f6
...
Using default interface naming scheme 'v243'.
ID_NET_NAMING_SCHEME=v243
ID_NET_NAME_MAC=enx54ee75cb1dc0
ID_OUI_FROM_DATABASE=Wistron InfoComm(Kunshan)Co.,Ltd.
ID_NET_NAME_PATH=enp0s31f6
...</programlisting>
</example>
<example>
<title>PCI Ethernet card with firmware index "1"</title>
<programlisting>ID_NET_NAME_ONBOARD=eno1
ID_NET_NAME_ONBOARD_LABEL=enEthernet Port 1
</programlisting>
<!-- FIXME: nuke the prefix! -->
</example>
<example>
<title>PCI Ethernet card in hotplug slot with firmware index number</title>
<programlisting># /sys/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/net/ens1
ID_NET_NAME_MAC=enx000000000466
ID_NET_NAME_PATH=enp5s0
ID_NET_NAME_SLOT=ens1</programlisting>
</example>
<example>
<title>PCI Ethernet multi-function card with 2 ports</title>
<programlisting># /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/enp2s0f0
ID_NET_NAME_MAC=enx78e7d1ea46da
ID_NET_NAME_PATH=enp2s0f0
# /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.1/net/enp2s0f1
ID_NET_NAME_MAC=enx78e7d1ea46dc
ID_NET_NAME_PATH=enp2s0f1</programlisting>
</example>
<example>
<title>PCI WLAN card</title>
<programlisting># /sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/net/wlp3s0
ID_NET_NAME_MAC=wlx0024d7e31130
ID_NET_NAME_PATH=wlp3s0</programlisting>
</example>
<example>
<title>PCI IB host adapter with 2 ports</title>
<programlisting># /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.0/net/ibp21s0f0
ID_NET_NAME_PATH=ibp21s0f0
# /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.1/net/ibp21s0f1
ID_NET_NAME_PATH=ibp21s0f1</programlisting>
</example>
<example>
<title>USB built-in 3G modem</title>
<programlisting># /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.6/net/wwp0s29u1u4i6
ID_NET_NAME_MAC=wwx028037ec0200
ID_NET_NAME_PATH=wwp0s29u1u4i6</programlisting>
</example>
<example>
<title>USB Android phone</title>
<programlisting># /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0/net/enp0s29u1u2
ID_NET_NAME_MAC=enxd626b3450fb5
ID_NET_NAME_PATH=enp0s29u1u2</programlisting>
</example>
<example>
<title>s390 grouped CCW interface</title>
<programlisting># /sys/devices/css0/0.0.0007/0.0.f5f0/group_device/net/encf5f0
ID_NET_NAME_MAC=enx026d3c00000a
ID_NET_NAME_PATH=encf5f0</programlisting>
</example>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<ulink url="https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames">the
original page describing stable interface names</ulink>
</para>
</refsect1>
</refentry>

81
src/udev/udev-builtin-net_id.c
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@ -9,86 +9,7 @@
*
* http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames
*
* Two character prefixes based on the type of interface:
* en — Ethernet
* ib — InfiniBand
* sl — serial line IP (slip)
* wl — wlan
* ww — wwan
*
* Type of names:
* b<number> — BCMA bus core number
* c<bus_id> — bus id of a grouped CCW or CCW device,
* with all leading zeros stripped [s390]
* o<index>[n<phys_port_name>|d<dev_port>]
* — on-board device index number
* s<slot>[f<function>][n<phys_port_name>|d<dev_port>]
* — hotplug slot index number
* x<MAC> — MAC address
* [P<domain>]p<bus>s<slot>[f<function>][n<phys_port_name>|d<dev_port>]
* — PCI geographical location
* [P<domain>]p<bus>s<slot>[f<function>][u<port>][..][c<config>][i<interface>]
* — USB port number chain
* v<slot> - VIO slot number (IBM PowerVM)
* a<vendor><model>i<instance> — Platform bus ACPI instance id
* i<addr>n<phys_port_name> — Netdevsim bus address and port name
*
* All multi-function PCI devices will carry the [f<function>] number in the
* device name, including the function 0 device.
*
* SR-IOV virtual devices are named based on the name of the parent interface,
* with a suffix of "v<N>", where <N> is the virtual device number.
*
* When using PCI geography, The PCI domain is only prepended when it is not 0.
*
* For USB devices the full chain of port numbers of hubs is composed. If the
* name gets longer than the maximum number of 15 characters, the name is not
* exported.
* The usual USB configuration == 1 and interface == 0 values are suppressed.
*
* PCI Ethernet card with firmware index "1":
* ID_NET_NAME_ONBOARD=eno1
* ID_NET_NAME_ONBOARD_LABEL=Ethernet Port 1
*
* PCI Ethernet card in hotplug slot with firmware index number:
* /sys/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/net/ens1
* ID_NET_NAME_MAC=enx000000000466
* ID_NET_NAME_PATH=enp5s0
* ID_NET_NAME_SLOT=ens1
*
* PCI Ethernet multi-function card with 2 ports:
* /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/enp2s0f0
* ID_NET_NAME_MAC=enx78e7d1ea46da
* ID_NET_NAME_PATH=enp2s0f0
* /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.1/net/enp2s0f1
* ID_NET_NAME_MAC=enx78e7d1ea46dc
* ID_NET_NAME_PATH=enp2s0f1
*
* PCI wlan card:
* /sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/net/wlp3s0
* ID_NET_NAME_MAC=wlx0024d7e31130
* ID_NET_NAME_PATH=wlp3s0
*
* PCI IB host adapter with 2 ports:
* /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.0/net/ibp21s0f0
* ID_NET_NAME_PATH=ibp21s0f0
* /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.1/net/ibp21s0f1
* ID_NET_NAME_PATH=ibp21s0f1
*
* USB built-in 3G modem:
* /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.6/net/wwp0s29u1u4i6
* ID_NET_NAME_MAC=wwx028037ec0200
* ID_NET_NAME_PATH=wwp0s29u1u4i6
*
* USB Android phone:
* /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0/net/enp0s29u1u2
* ID_NET_NAME_MAC=enxd626b3450fb5
* ID_NET_NAME_PATH=enp0s29u1u2
*
* s390 grouped CCW interface:
* /sys/devices/css0/0.0.0007/0.0.f5f0/group_device/net/encf5f0
* ID_NET_NAME_MAC=enx026d3c00000a
* ID_NET_NAME_PATH=encf5f0
* When the code here is changed, man/systemd.net-naming-scheme.xml must be updated too.
*/
#include <errno.h>