systemd: install initrd services using a generator

Since both `NetworkManager.service` and `NetworkManager-initrd.service` are
allocated for the same bus name (`org.freedesktop.NetworkManager`) and this is
not allowed, the best option is to use a systemd generator to install them only
in the initrd, instead of setting fixed Install sections.

Fixes #1814

contrib/fedora/rpm/NetworkManager.spec

@@ -675,6 +675,7 @@ Preferably use nmcli instead.
 	-Dsession_tracking=systemd \
 	-Dsuspend_resume=systemd \
 	-Dsystemdsystemunitdir=%{_unitdir} \
+	-Dsystemdsystemgeneratordir=%{_systemdgeneratordir} \
 	-Dsystem_ca_path=/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem \
 	-Ddbus_conf_dir=%{dbus_sys_dir} \
 	-Dtests=yes \
@@ -747,6 +748,7 @@ rm -f %{buildroot}%{_libdir}/pppd/%{ppp_version}/*.la
 rm -f %{buildroot}%{nmplugindir}/*.la
 
 # Don't use the *-initrd.service files yet, wait dracut to support them
+rm -f %{buildroot}%{_systemdgeneratordir}/nm-initrd-generator.sh
 rm -f %{buildroot}%{_unitdir}/NetworkManager-config-initrd.service
 rm -f %{buildroot}%{_unitdir}/NetworkManager-initrd.service
 rm -f %{buildroot}%{_unitdir}/NetworkManager-wait-online-initrd.service

contrib/fedora/rpm/configure-for-system.sh

@@ -398,6 +398,7 @@ meson setup\
     -Dsession_tracking=systemd \
     -Dsuspend_resume=systemd \
     -Dsystemdsystemunitdir=/usr/lib/systemd/system \
+    -Dsystemdsystemgeneratordir=/usr/lib/systemd/system-generators \
     -Dsystem_ca_path=/etc/pki/tls/cert.pem \
     -Ddbus_conf_dir="$P_DBUS_SYS_DIR" \
     -Dtests=yes \

data/NetworkManager-config-initrd.service.in

@@ -1,10 +1,10 @@
 [Unit]
 Description=NetworkManager Configuration (initrd)
+AssertPathExists=/etc/initrd-release
 DefaultDependencies=no
 Wants=systemd-journald.socket
 After=systemd-journald.socket
 Before=systemd-udevd.service systemd-udev-trigger.service
-ConditionPathExists=/etc/initrd-release
 
 [Service]
 Type=oneshot
@@ -22,6 +22,3 @@ ExecStartPost=/bin/sh -c ' \
     fi \
 '
 RemainAfterExit=yes
-
-[Install]
-WantedBy=initrd.target

data/NetworkManager-initrd.service.in

@@ -1,11 +1,11 @@
 [Unit]
 Description=NetworkManager (initrd)
+AssertPathExists=/etc/initrd-release
 DefaultDependencies=no
 Wants=systemd-udev-trigger.service network.target
 After=systemd-udev-trigger.service network-pre.target dbus.service NetworkManager-config-initrd.service
 Before=network.target
 BindsTo=dbus.service
-ConditionPathExists=/etc/initrd-release
 ConditionPathExists=/run/NetworkManager/initrd/neednet
 ConditionPathExistsGlob=|/usr/lib/NetworkManager/system-connections/*
 ConditionPathExistsGlob=|/run/NetworkManager/system-connections/*
@@ -22,11 +22,3 @@ Environment=NM_CONFIG_ENABLE_TAG=initrd
 Restart=on-failure
 ProtectSystem=true
 ProtectHome=read-only
-
-[Install]
-WantedBy=initrd.target
-# We want to enable NetworkManager-wait-online-initrd.service whenever this
-# service is enabled. NetworkManager-wait-online-initrd.service has
-# WantedBy=network-online.target, so enabling it only has an effect if
-# network-online.target itself is enabled or pulled in by some other unit.
-Also=NetworkManager-config-initrd.service NetworkManager-wait-online-initrd.service

data/NetworkManager-wait-online-initrd.service.in

@@ -1,10 +1,10 @@
 [Unit]
 Description=NetworkManager Wait Online (initrd)
+AssertPathExists=/etc/initrd-release
 DefaultDependencies=no
 Requires=NetworkManager-initrd.service
 After=NetworkManager-initrd.service
 Before=network-online.target
-ConditionPathExists=/etc/initrd-release
 ConditionPathExists=/run/NetworkManager/initrd/neednet
 
 [Service]
@@ -21,6 +21,3 @@ Type=oneshot
 ExecStart=@bindir@/nm-online -s -q
 RemainAfterExit=yes
 Environment=NM_ONLINE_TIMEOUT=3600
-
-[Install]
-WantedBy=initrd.target network-online.target

meson.build

@@ -383,6 +383,14 @@ if install_systemdunitdir and systemd_systemdsystemunitdir == ''
   systemd_systemdsystemunitdir = systemd_dep.get_variable(pkgconfig: 'systemdsystemunitdir', pkgconfig_define: ['rootprefix', nm_prefix])
 endif
 
+systemd_systemdsystemgeneratordir = get_option('systemdsystemgeneratordir')
+install_systemdgeneratordir = (systemd_systemdsystemgeneratordir != 'no')
+
+if install_systemdgeneratordir and systemd_systemdsystemgeneratordir == ''
+  assert(systemd_dep.found(), 'systemd required but not found, please provide a valid systemd user generator dir or disable it')
+  systemd_systemdsystemgeneratordir = systemd_dep.get_variable(pkgconfig: 'systemdsystemgeneratordir', pkgconfig_define: ['rootprefix', nm_prefix])
+endif
+
 enable_systemd_journal = get_option('systemd_journal')
 if enable_systemd_journal
   assert(libsystemd_dep.found(), 'Missing systemd-journald support')
@@ -1059,6 +1067,7 @@ output = '\nSystem paths:\n'
 output += '  prefix: ' + nm_prefix + '\n'
 output += '  exec_prefix: ' + nm_prefix + '\n'
 output += '  systemdunitdir: ' + systemd_systemdsystemunitdir + '\n'
+output += '  systemdgeneratordir: ' + systemd_systemdsystemgeneratordir + '\n'
 output += '  udev_dir: ' + udev_udevdir + '\n'
 output += '  nmbinary: ' + nm_pkgsbindir + '\n'
 output += '  nmconfdir: ' + nm_pkgconfdir + '\n'

meson_options.txt

@@ -1,5 +1,6 @@
 # system paths
 option('systemdsystemunitdir', type: 'string', value: '', description: 'Directory for systemd service files')
+option('systemdsystemgeneratordir', type: 'string', value: '', description: 'Directory for systemd generator files')
 option('system_ca_path', type: 'string', value: '/etc/ssl/certs', description: 'path to system CA certificates')
 option('udev_dir', type: 'string', value: '', description: 'Absolute path of the udev base directory. Set to \'no\' not to install the udev rule')
 option('dbus_conf_dir', type: 'string', value: '', description: 'where D-Bus system.d directory is')

src/nm-initrd-generator/meson.build

@@ -46,3 +46,10 @@ executable(
   install: true,
   install_dir: nm_libexecdir,
 )
+
+if install_systemdgeneratordir
+  install_data(
+    'nm-initrd-generator.sh',
+    install_dir: systemd_systemdsystemgeneratordir,
+  )
+endif

src/nm-initrd-generator/nm-initrd-generator.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+# initrd-specific units
+initrd_units=(
+    NetworkManager-config-initrd.service
+    NetworkManager-initrd.service
+    NetworkManager-wait-online-initrd.service
+)
+
+# host-specific units
+host_units=(
+    NetworkManager.service
+    NetworkManager-dispatcher.service
+    NetworkManager-wait-online.service
+)
+
+# Get generator normal directory
+normal_dir=$1
+
+# Since NetworkManager-initrd.service and NetworkManager.service are allocated
+# for the same bus name org.freedesktop.NetworkManager, we should mask one of
+# them depending on if we are in the initrd or on the host.
+if [ "$SYSTEMD_IN_INITRD" != 1 ]; then
+    # Mask initrd units in the host
+    for unit in "${initrd_units[@]}"; do
+        ln -s /dev/null "$normal_dir"/"$unit" 2> /dev/null
+    done
+    # Nothing else to do
+    exit 0
+fi
+
+# Mask host units in the initrd
+for unit in "${host_units[@]}"; do
+    ln -s /dev/null "$normal_dir"/"$unit" 2> /dev/null
+done
+
+# Install initrd units in the unit file hierarchy
+mkdir -p "$normal_dir"/initrd.target.wants
+mkdir -p "$normal_dir"/network-online.target.wants
+for unit in "${initrd_units[@]}"; do
+    ln -s /usr/lib/systemd/system/"$unit" \
+        "$normal_dir"/initrd.target.wants/"$unit"
+    if [ "$unit" = "NetworkManager-wait-online-initrd.service" ]; then
+        ln -s /usr/lib/systemd/system/"$unit" \
+            "$normal_dir"/network-online.target.wants/"$unit"
+    fi
+done
+
+exit 0