util: Move dbus AddMatch const to util package

engine/resources/hostname.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/purpleidea/mgmt/engine"
 	"github.com/purpleidea/mgmt/engine/traits"
+	engineUtil "github.com/purpleidea/mgmt/engine/util"
 	"github.com/purpleidea/mgmt/util"
 
 	"github.com/godbus/dbus"
@@ -36,7 +37,6 @@ func init() {
 const (
 	hostname1Path  = "/org/freedesktop/hostname1"
 	hostname1Iface = "org.freedesktop.hostname1"
-	dbusAddMatch   = "org.freedesktop.DBus.AddMatch"
 )
 
 // ErrResourceInsufficientParameters is returned when the configuration of the
@@ -113,7 +113,7 @@ func (obj *HostnameRes) Watch() error {
 	}
 	defer bus.Close()
 	callResult := bus.BusObject().Call(
-		"org.freedesktop.DBus.AddMatch", 0,
+		engineUtil.DBusAddMatch, 0,
 		fmt.Sprintf("type='signal',path='%s',interface='org.freedesktop.DBus.Properties',member='PropertiesChanged'", hostname1Path))
 	if callResult.Err != nil {
 		return errwrap.Wrap(callResult.Err, "Failed to subscribe to DBus events for hostname1")

engine/resources/nspawn.go

@@ -25,6 +25,7 @@ import (
 
 	"github.com/purpleidea/mgmt/engine"
 	"github.com/purpleidea/mgmt/engine/traits"
+	engineUtil "github.com/purpleidea/mgmt/engine/util"
 	"github.com/purpleidea/mgmt/util"
 
 	systemdDbus "github.com/coreos/go-systemd/dbus"
@@ -154,7 +155,7 @@ func (obj *NspawnRes) Watch() error {
 	defer bus.Close()
 
 	// add a match rule to match messages going through the message bus
-	call := bus.BusObject().Call("org.freedesktop.DBus.AddMatch", 0,
+	call := bus.BusObject().Call(engineUtil.DBusAddMatch, 0,
 		fmt.Sprintf("type='signal',interface='%s',eavesdrop='true'",
 			dbusInterface))
 	// <-call.Done

engine/resources/packagekit/packagekit.go

@@ -25,6 +25,7 @@ import (
 	"runtime"
 	"strings"
 
+	engineUtil "github.com/purpleidea/mgmt/engine/util"
 	"github.com/purpleidea/mgmt/util"
 
 	"github.com/godbus/dbus"
@@ -46,7 +47,6 @@ const (
 	PkPath                 = "/org/freedesktop/PackageKit"
 	PkIface                = "org.freedesktop.PackageKit"
 	PkIfaceTransaction     = PkIface + ".Transaction"
-	dbusAddMatch           = "org.freedesktop.DBus.AddMatch"
 )
 
 var (
@@ -197,10 +197,10 @@ func (obj *Conn) matchSignal(ch chan *dbus.Signal, path dbus.ObjectPath, iface s
 	bus := obj.GetBus().BusObject()
 	pathStr := fmt.Sprintf("%s", path)
 	if len(signals) == 0 {
-		call = bus.Call(dbusAddMatch, 0, "type='signal',path='"+pathStr+"',interface='"+iface+"'")
+		call = bus.Call(engineUtil.DBusAddMatch, 0, "type='signal',path='"+pathStr+"',interface='"+iface+"'")
 	} else {
 		for _, signal := range signals {
-			call = bus.Call(dbusAddMatch, 0, "type='signal',path='"+pathStr+"',interface='"+iface+"',member='"+signal+"'")
+			call = bus.Call(engineUtil.DBusAddMatch, 0, "type='signal',path='"+pathStr+"',interface='"+iface+"',member='"+signal+"'")
 			if call.Err != nil {
 				break
 			}

engine/util/util.go

@@ -36,6 +36,14 @@ import (
 const (
 	// StructTag is the key we use in struct field names for key mapping.
 	StructTag = "lang"
+	// DBusInterface is the dbus interface that contains genereal methods.
+	DBusInterface = "org.freedesktop.DBus"
+	// DBusAddMatch is the dbus method to receive a subset of dbus broadcast
+	// signals.
+	DBusAddMatch = DBusInterface + ".AddMatch"
+	// DBusRemoveMatch is the dbus method to remove a previously defined
+	// AddMatch rule.
+	DBusRemoveMatch = DBusInterface + ".RemoveMatch"
 )
 
 // ResToB64 encodes a resource to a base64 encoded string (after serialization).