dbus: add socket activation but do not enable it

The following changes are included:

1) install user unit files from upstream dbus
2) use absolute paths to config for --system and --session instances
3) make socket activation of user units configurable

There has been a number of PRs to address this, so this one does the
bare minimum, which is to make the functionality available and
configurable but defaults to off.

Related PRs:
 - #18382
 - #18222

(cherry picked from commit f7215c9b5b47dfb0a6dbe87ff33d7730729a32e5)
Signed-off-by: Domen Kožar <domen@dev.si>

nixos/modules/services/system/dbus.nix

@@ -8,7 +8,7 @@ let
 
   cfg = config.services.dbus;
 
-  homeDir = "/var/run/dbus";
+  homeDir = "/run/dbus";
 
   systemExtraxml = concatStrings (flip concatMap cfg.packages (d: [
     "<servicedir>${d}/share/dbus-1/system-services</servicedir>"
@@ -20,6 +20,8 @@ let
     "<includedir>${d}/etc/dbus-1/session.d</includedir>"
   ]));
 
+  daemonArgs = "--address=systemd: --nofork --nopidfile --systemd-activation";
+
   configDir = pkgs.runCommand "dbus-conf"
     { preferLocalBuild = true;
       allowSubstitutes = false;
@@ -27,6 +29,14 @@ let
     ''
       mkdir -p $out
 
+      cp ${pkgs.dbus.out}/share/dbus-1/{system,session}.conf $out
+
+      # avoid circular includes
+      sed -ri 's@(<include ignore_missing="yes">/etc/dbus-1/(system|session)\.conf</include>)@<!-- \1 -->@g' $out/{system,session}.conf
+
+      # include by full path
+      sed -ri "s@/etc/dbus-1/(system|session)-@$out/\1-@" $out/{system,session}.conf
+
       sed '${./dbus-system-local.conf.in}' \
         -e 's,@servicehelper@,${config.security.wrapperDir}/dbus-daemon-launch-helper,g' \
         -e 's,@extra@,${systemExtraxml},' \
@@ -72,11 +82,16 @@ in
         '';
       };
 
+      socketActivated = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Make the user instance socket activated.
+        '';
+      };
     };
-
   };
 
-
   ###### implementation
 
   config = mkIf cfg.enable {
@@ -114,13 +129,29 @@ in
       config.system.path
     ];
 
-    # Don't restart dbus-daemon. Bad things tend to happen if we do.
-    systemd.services.dbus.reloadIfChanged = true;
+    systemd.services.dbus = {
+      # Don't restart dbus-daemon. Bad things tend to happen if we do.
+      reloadIfChanged = true;
+      restartTriggers = [ configDir ];
+      serviceConfig.ExecStart = [
+        ""
+        "${lib.getBin pkgs.dbus}/bin/dbus-daemon --config-file=${configDir}/system.conf ${daemonArgs}"
+      ];
+    };
 
-    systemd.services.dbus.restartTriggers = [ configDir ];
+    systemd.user = {
+      services.dbus = {
+        # Don't restart dbus-daemon. Bad things tend to happen if we do.
+        reloadIfChanged = true;
+        restartTriggers = [ configDir ];
+        serviceConfig.ExecStart = [
+          ""
+          "${lib.getBin pkgs.dbus}/bin/dbus-daemon --config-file=${configDir}/session.conf ${daemonArgs}"
+        ];
+      };
+      sockets.dbus.wantedBy = mkIf cfg.socketActivated [ "sockets.target" ];
+    };
 
     environment.pathsToLink = [ "/etc/dbus-1" "/share/dbus-1" ];
-
   };
-
 }

nixos/modules/services/x11/display-managers/default.nix

@@ -134,13 +134,8 @@ let
         (*) echo "$0: Desktop manager '$desktopManager' not found.";;
       esac
 
-      # FIXME: gdbus should not be in glib.dev!
-      ${optionalString (cfg.startDbusSession && cfg.updateDbusEnvironment) ''
-        ${pkgs.glib.dev}/bin/gdbus call --session \
-          --dest org.freedesktop.DBus --object-path /org/freedesktop/DBus \
-          --method org.freedesktop.DBus.UpdateActivationEnvironment \
-          "{$(env | ${pkgs.gnused}/bin/sed "s/'/\\\\'/g; s/\([^=]*\)=\(.*\)/'\1':'\2'/" \
-                  | ${pkgs.coreutils}/bin/paste -sd,)}"
+      ${optionalString cfg.updateDbusEnvironment ''
+        ${lib.getBin pkgs.dbus}/bin/dbus-update-activation-environment --systemd --all
       ''}
 
       test -n "$waitPID" && wait "$waitPID"

pkgs/development/libraries/dbus/default.nix

@@ -44,7 +44,11 @@ self =  stdenv.mkDerivation {
       "--localstatedir=/var"
       "--sysconfdir=/etc"
       "--with-session-socket-dir=/tmp"
+      "--with-system-pid-file=/run/dbus/pid"
+      "--with-system-socket=/run/dbus/system_bus_socket"
       "--with-systemdsystemunitdir=$(out)/etc/systemd/system"
+      "--with-systemduserunitdir=$(out)/etc/systemd/user"
+      "--enable-user-session"
       # this package installs nothing into those dirs and they create a dependency
       "--datadir=/run/current-system/sw/share"
       "--libexecdir=$(out)/libexec" # we don't need dbus-daemon-launch-helper
@@ -81,4 +85,3 @@ self =  stdenv.mkDerivation {
     };
   };
 in self
-