Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 632 insertions, 0 deletions

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+<?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-or-later -->
+
+<refentry id="systemd.net-naming-scheme" xmlns:xi="http://www.w3.org/2001/XInclude">
+  <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 names and MAC addresses may be generated based on certain stable interface
+    attributes. This is possible when there is enough information about the device to generate those
+    attributes and the use of this information is configured. This page describes interface naming, 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 and MAC addresses are derived from various stable device metadata attributes. Newer versions
+    of udev take more of these attributes into account, improving (and thus possibly changing) the names and
+    addresses used for the same devices. Different versions of those generation 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 overridden
+    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 properties have been generated, appropriate udev rules may be used to actually rename
+    devices based on those properties. See the description of <varname>NamePolicy=</varname> and
+    <varname>MACAddressPolicy=</varname> in
+    <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+
+    <para>Note that while the concept of network interface naming schemes is primarily relevant in the
+    context of <filename>systemd-udevd.service</filename>, the
+    <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    container manager also takes it into account when naming network interfaces, see below.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Policies</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>
+          <term><varname>ID_NET_NAME_ONBOARD=<replaceable>prefix</replaceable><constant>d</constant><replaceable>number</replaceable></varname></term>
+
+          <listitem><para>This name is set based on the numeric ordering information given by the firmware
+          for on-board devices. Different schemes are used depending on the firmware type, as described in
+          the table below.</para>
+
+            <table>
+              <title>On-board naming schemes</title>
+
+              <tgroup cols='2'>
+                <thead>
+                  <row>
+                    <entry>Format</entry>
+                    <entry>Description</entry>
+                  </row>
+                </thead>
+
+                <tbody>
+                  <row>
+                    <entry><replaceable>prefix</replaceable><constant>o</constant><replaceable>number</replaceable></entry>
+                    <entry>PCI on-board index</entry>
+                  </row>
+
+                  <row>
+                    <entry><replaceable>prefix</replaceable><constant>d</constant><replaceable>number</replaceable></entry>
+                    <entry>Devicetree alias index</entry>
+                  </row>
+
+                </tbody>
+              </tgroup>
+            </table>
+
+              <xi:include href="version-info.xml" xpointer="v243"/>
+          </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 textual 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>
+
+          <xi:include href="version-info.xml" xpointer="v243"/>
+          </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>
+
+          <xi:include href="version-info.xml" xpointer="v243"/>
+          </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>v</constant><replaceable>slot</replaceable></varname></term>
+          <term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable><constant>x</constant><replaceable>slot</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>
+          <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>r</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 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><replaceable>prefix</replaceable> <constant>v</constant><replaceable>slot</replaceable></entry>
+                  <entry>VIO slot number (IBM PowerVM)</entry>
+                </row>
+
+                <row>
+                  <entry><replaceable>prefix</replaceable> <constant>X</constant><replaceable>number</replaceable></entry>
+                  <entry>VIF interface number (Xen)</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>
+
+                <row>
+                  <entry>… <constant>r</constant><replaceable>slot</replaceable></entry>
+                  <entry>SR-IOV 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>
+
+          <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.</para>
+
+          <para>SR-IOV virtual device representors are named based on the name of the physical device
+          interface, with a suffix of <constant>r</constant> and the number of the virtual device that
+          is linked to the particular representor, with any leading zeros removed. The physical port
+          name and the bus number are ignored.</para>
+
+          <para>In some configurations a parent PCI bridge of a given network controller may be associated
+          with a slot. In such case we don't generate this device property to avoid possible naming conflicts.</para>
+
+          <xi:include href="version-info.xml" xpointer="v243"/>
+          </listitem>
+        </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>u</constant><replaceable>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>]</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>
+
+          <xi:include href="version-info.xml" xpointer="v243"/>
+          </listitem>
+        </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>History</title>
+
+    <para>The following "naming schemes" have been defined (which may be chosen at system boot-up time via
+    the <varname>net.naming-scheme=</varname> kernel command line switch, see above):</para>
+
+    <variablelist>
+        <varlistentry>
+          <term><constant>v238</constant></term>
+
+          <listitem><para>This is the naming scheme that was implemented in systemd 238.</para>
+
+          <xi:include href="version-info.xml" xpointer="v243"/></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>
+
+          <xi:include href="version-info.xml" xpointer="v243"/>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v240</constant></term>
+
+          <listitem><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 index="false">.link</filename> file. See
+          <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+          for a description of <varname>NamePolicy=</varname>.</para>
+
+          <xi:include href="version-info.xml" xpointer="v243"/></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v241</constant></term>
+
+          <listitem><para><option>MACAddressPolicy=persistent</option> was extended to set MAC addresses
+          based on the device name. Previously addresses were only based on the
+          <varname index="false">ID_NET_NAME_*</varname> attributes, which meant that interface names would
+          never be generated for virtual devices. Now a persistent address will be generated for most
+          devices, including in particular bridges.</para>
+
+          <para>Note: when userspace does not set a MAC address for a bridge device, the kernel will
+          initially assign a random address, and then change it when the first device is enslaved to the
+          bridge. With this naming policy change, bridges get a persistent MAC address based on the bridge
+          name instead of the first enslaved device.</para>
+
+          <xi:include href="version-info.xml" xpointer="v243"/></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v243</constant></term>
+
+          <listitem><para>Support for renaming netdevsim (simulated networking) devices was added. Previously
+          those devices were not renamed.</para>
+
+          <para>Previously two-letter interface type prefix was prepended to
+          <varname>ID_NET_LABEL_ONBOARD=</varname>. This is not done anymore.</para>
+
+          <xi:include href="version-info.xml" xpointer="v243"/></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v245</constant></term>
+
+          <listitem><para>When
+          <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+          derives the name for the host side of the network interface created with
+          <option>--network-veth</option> from the container name it previously simply truncated the result
+          at 15 characters if longer (since that's the maximum length for network interface names). From now
+          on, for any interface name that would be longer than 15 characters the last 4 characters are set to
+          a 24bit hash value of the full interface name. This way network interface name collisions between
+          multiple similarly named containers (who only differ in container name suffix) should be less
+          likely (but still possible, since the 24bit hash value is very small).</para>
+
+          <xi:include href="version-info.xml" xpointer="v245"/></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v247</constant></term>
+
+          <listitem><para>When a PCI slot is associated with a PCI bridge that has multiple child network
+          controllers, the same value of the <varname>ID_NET_NAME_SLOT</varname> property might be derived
+          for those controllers. This would cause a naming conflict if the property is selected as the device
+          name. Now, we detect this situation and don't produce the <varname>ID_NET_NAME_SLOT</varname>
+          property.</para>
+
+          <xi:include href="version-info.xml" xpointer="v247"/></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v249</constant></term>
+
+          <listitem><para>PCI hotplug slot names for the s390 PCI driver are a hexadecimal representation
+          of the <filename>function_id</filename> device attribute. This attribute is now used to build the
+          <varname>ID_NET_NAME_SLOT</varname>. Before that, all slot names were parsed as decimal
+          numbers, which could either result in an incorrect value of the <varname>ID_NET_NAME_SLOT</varname>
+          property or none at all.</para>
+
+          <para>Some firmware and hypervisor implementations report unreasonably high numbers for the
+          on-board index. To prevent the generation of bogus on-board interface names, index numbers greater
+          than 16381 (2¹⁴-1) were ignored. For s390 PCI devices index values up to 65535 (2¹⁶-1) are valid.
+          To account for that, the limit was increased to 65535.</para>
+
+          <para>The udev rule <varname>NAME=</varname> replaces <literal>:</literal>,
+          <literal>/</literal>, and <literal>%</literal> with an underscore (<literal>_</literal>), and
+          refuses strings which contain only numerics.</para>
+
+          <xi:include href="version-info.xml" xpointer="v249"/>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v250</constant></term>
+
+          <listitem><para>Added naming scheme for Xen netfront "vif" interfaces based on the guest side
+          VIF number set from the Xen config (or the interface index in AWS EC2).</para>
+
+          <xi:include href="version-info.xml" xpointer="v250"/>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v251</constant></term>
+
+          <listitem><para>Since version <constant>v247</constant> we no longer set
+          <varname>ID_NET_NAME_SLOT</varname> if we detect that a PCI device associated with a slot is a PCI
+          bridge as that would create naming conflict when there are more child devices on that bridge. Now,
+          this is relaxed and we will use slot information to generate the name based on it but only if
+          the PCI device has multiple functions. This is safe because distinct function number is a part of
+          the device name for multifunction devices.</para>
+
+          <xi:include href="version-info.xml" xpointer="v251"/>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v252</constant></term>
+
+          <listitem><para>Added naming scheme for platform devices with devicetree aliases.</para>
+
+          <xi:include href="version-info.xml" xpointer="v252"/>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v253</constant></term>
+
+          <listitem><para>Set <varname>ID_NET_NAME_PATH</varname> for usb devices not connected via a PCI bus.</para>
+
+          <xi:include href="version-info.xml" xpointer="v253"/>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v254</constant></term>
+
+          <listitem><para>Naming was changed for SR-IOV virtual device representors, optionally settable at
+          compilation time. The <literal>r<replaceable>slot</replaceable></literal> suffix was added to
+          differentiate SR-IOV virtual device representors attached to a single physical device interface.
+          Because of a mistake, this scheme was <emphasis>not the the default scheme for systemd version
+          254</emphasis>.</para>
+
+          <xi:include href="version-info.xml" xpointer="v255"/>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>v255</constant></term>
+
+          <listitem><para>Naming was changed for SR-IOV virtual device representors to enable the
+          change introduced in <constant>v254</constant> by default.</para>
+
+          <xi:include href="version-info.xml" xpointer="v255"/>
+          </listitem>
+        </varlistentry>
+
+      </variablelist>
+
+    <para>Note that <constant>latest</constant> may be used to denote the latest scheme known (to this
+    particular version of systemd).</para>
+  </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=Ethernet Port 1
+      </programlisting>
+    </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://systemd.io/PREDICTABLE_INTERFACE_NAMES">Predictable Network Interface Names</ulink>,
+      <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>