Merge pull request #107382 from rnhmjoj/no-udev-settle

nixos/{networkd,dhcpcd}: remove udev-settle hack
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Michele Guerini Rocco 2021-02-20 20:49:19 +01:00 committed by GitHub
commit 19d715c573
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8 changed files with 136 additions and 8 deletions

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@ -15,5 +15,6 @@
<xi:include href="firewall.xml" />
<xi:include href="wireless.xml" />
<xi:include href="ad-hoc-network-config.xml" />
<xi:include href="renaming-interfaces.xml" />
<!-- TODO: OpenVPN, NAT -->
</chapter>

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@ -0,0 +1,67 @@
<section xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
version="5.0"
xml:id="sec-rename-ifs">
<title>Renaming network interfaces</title>
<para>
NixOS uses the udev
<link xlink:href="https://systemd.io/PREDICTABLE_INTERFACE_NAMES/">predictable naming scheme</link>
to assign names to network interfaces. This means that by default
cards are not given the traditional names like
<literal>eth0</literal> or <literal>eth1</literal>, whose order can
change unpredictably across reboots. Instead, relying on physical
locations and firmware information, the scheme produces names like
<literal>ens1</literal>, <literal>enp2s0</literal>, etc.
</para>
<para>
These names are predictable but less memorable and not necessarily
stable: for example installing new hardware or changing firmware
settings can result in a
<link xlink:href="https://github.com/systemd/systemd/issues/3715#issue-165347602">name change</link>.
If this is undesirable, for example if you have a single ethernet
card, you can revert to the traditional scheme by setting
<xref linkend="opt-networking.usePredictableInterfaceNames"/> to
<literal>false</literal>.
</para>
<section xml:id="sec-custom-ifnames">
<title>Assigning custom names</title>
<para>
In case there are multiple interfaces of the same type, its better to
assign custom names based on the device hardware address. For
example, we assign the name <literal>wan</literal> to the interface
with MAC address <literal>52:54:00:12:01:01</literal> using a
netword link unit:
</para>
<programlisting>
<link linkend="opt-systemd.network.links">systemd.network.links."10-wan"</link> = {
matchConfig.MACAddress = "52:54:00:12:01:01";
linkConfig.Name = "wan";
};
</programlisting>
<para>
Note that links are directly read by udev, <emphasis>not networkd</emphasis>,
and will work even if networkd is disabled.
</para>
<para>
Alternatively, we can use a plain old udev rule:
</para>
<programlisting>
<link linkend="opt-services.udev.initrdRules">services.udev.initrdRules</link> = ''
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", \
ATTR{address}=="52:54:00:12:01:01", KERNEL=="eth*", NAME="wan"
'';
</programlisting>
<warning><para>
The rule must be installed in the initrd using
<literal>services.udev.initrdRules</literal>, not the usual
<literal>services.udev.extraRules</literal> option. This is to avoid race
conditions with other programs controlling the interface.
</para></warning>
</section>
</section>

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@ -91,6 +91,16 @@
</para>
<itemizedlist>
<listitem>
<para>
If you are using <option>services.udev.extraRules</option> to assign
custom names to network interfaces, this may stop working due to a change
in the initialisation of dhcpcd and systemd networkd. To avoid this, either
move them to <option>services.udev.initrdRules</option> or see the new
<link linkend="sec-custom-ifnames">Assigning custom names</link> section
of the NixOS manual for an example using networkd links.
</para>
</listitem>
<listitem>
<para>
The <literal>systemConfig</literal> kernel parameter is no longer added to boot loader entries. It has been unused since September 2010, but if do have a system generation from that era, you will now be unable to boot into them.

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@ -202,12 +202,26 @@ in
'';
};
extraRules = mkOption {
initrdRules = mkOption {
default = "";
example = ''
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:1D:60:B9:6D:4F", KERNEL=="eth*", NAME="my_fast_network_card"
'';
type = types.lines;
description = ''
<command>udev</command> rules to include in the initrd
<emphasis>only</emphasis>. They'll be written into file
<filename>99-local.rules</filename>. Thus they are read and applied
after the essential initrd rules.
'';
};
extraRules = mkOption {
default = "";
example = ''
ENV{ID_VENDOR_ID}=="046d", ENV{ID_MODEL_ID}=="0825", ENV{PULSE_IGNORE}="1"
'';
type = types.lines;
description = ''
Additional <command>udev</command> rules. They'll be written
into file <filename>99-local.rules</filename>. Thus they are
@ -284,6 +298,13 @@ in
boot.kernelParams = mkIf (!config.networking.usePredictableInterfaceNames) [ "net.ifnames=0" ];
boot.initrd.extraUdevRulesCommands = optionalString (cfg.initrdRules != "")
''
cat <<'EOF' > $out/99-local.rules
${cfg.initrdRules}
EOF
'';
environment.etc =
{
"udev/rules.d".source = udevRules;

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@ -191,9 +191,8 @@ in
{ description = "DHCP Client";
wantedBy = [ "multi-user.target" ] ++ optional (!hasDefaultGatewaySet) "network-online.target";
wants = [ "network.target" "systemd-udev-settle.service" ];
wants = [ "network.target" ];
before = [ "network-online.target" ];
after = [ "systemd-udev-settle.service" ];
restartTriggers = [ exitHook ];

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@ -1553,9 +1553,6 @@ in
wantedBy = [ "multi-user.target" ];
aliases = [ "dbus-org.freedesktop.network1.service" ];
restartTriggers = map (x: x.source) (attrValues unitFiles);
# prevent race condition with interface renaming (#39069)
requires = [ "systemd-udev-settle.service" ];
after = [ "systemd-udev-settle.service" ];
};
systemd.services.systemd-networkd-wait-online = {

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@ -205,13 +205,22 @@ let
''; # */
# Networkd link files are used early by udev to set up interfaces early.
# This must be done in stage 1 to avoid race conditions between udev and
# network daemons.
linkUnits = pkgs.runCommand "link-units" {
allowedReferences = [ extraUtils ];
preferLocalBuild = true;
} ''
} (''
mkdir -p $out
cp -v ${udev}/lib/systemd/network/*.link $out/
'';
'' + (
let
links = filterAttrs (n: v: hasSuffix ".link" n) config.systemd.network.units;
files = mapAttrsToList (n: v: "${v.unit}/${n}") links;
in
concatMapStringsSep "\n" (file: "cp -v ${file} $out/") files
));
udevRules = pkgs.runCommand "udev-rules" {
allowedReferences = [ extraUtils ];

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@ -672,6 +672,30 @@ let
), "The IPv6 routing table has not been properly cleaned:\n{}".format(ipv6Residue)
'';
};
rename = {
name = "RenameInterface";
machine = { pkgs, ... }: {
virtualisation.vlans = [ 1 ];
networking = {
useNetworkd = networkd;
useDHCP = false;
};
} //
(if networkd
then { systemd.network.links."10-custom_name" = {
matchConfig.MACAddress = "52:54:00:12:01:01";
linkConfig.Name = "custom_name";
};
}
else { services.udev.initrdRules = ''
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="52:54:00:12:01:01", KERNEL=="eth*", NAME="custom_name"
'';
});
testScript = ''
machine.succeed("udevadm settle")
print(machine.succeed("ip link show dev custom_name"))
'';
};
# even with disabled networkd, systemd.network.links should work
# (as it's handled by udev, not networkd)
link = {