libnm: avoid loosing signals

D-Bus has an upper limit on number of Match rules and it's rather easy
to hit as the proxy likes to add one for each object. Let's remove the Match
rule the proxy added and ensure a less granular rule is present instead.

Ideally, we should be able to tell glib not to hook its rules.
Related: https://bugzilla.gnome.org/show_bug.cgi?id=758749

https://bugzilla.gnome.org/show_bug.cgi?id=758751

libnm/nm-dbus-helpers.c

@@ -25,6 +25,7 @@
 #include "nm-default.h"
 #include "nm-dbus-helpers.h"
 #include "nm-dbus-interface.h"
+#include "nm-macros-internal.h"
 
 static GBusType nm_bus = G_BUS_TYPE_SYSTEM;
 
@@ -116,6 +117,67 @@ _nm_dbus_register_proxy_type (const char *interface,
 #define NM_DBUS_PROXY_FLAGS (G_DBUS_PROXY_FLAGS_DO_NOT_LOAD_PROPERTIES | \
                              G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START)
 
+/* D-Bus has an upper limit on number of Match rules and it's rather easy
+ * to hit as the proxy likes to add one for each object. Let's remove the Match
+ * rule the proxy added and ensure a less granular rule is present instead.
+ *
+ * Also, don't do this immediately since it has a performance penalty.
+ * Still better than loosing the signals altogether.
+ *
+ * Ideally, we should be able to tell glib not to hook its rules:
+ * https://bugzilla.gnome.org/show_bug.cgi?id=758749
+ */
+static void
+_nm_dbus_proxy_replace_match (GDBusProxy *proxy)
+{
+	GDBusConnection *connection = g_dbus_proxy_get_connection (proxy);
+	static unsigned match_counter = 1024;
+	gchar *match;
+
+	nm_assert (!g_strcmp0 (g_dbus_proxy_get_name (proxy), NM_DBUS_SERVICE));
+
+	if (match_counter == 1) {
+		/* If we hit the low matches watermark, install a
+		 * less granular one. */
+		g_dbus_connection_call (connection,
+		                        "org.freedesktop.DBus",
+		                        "/org/freedesktop/DBus",
+		                        "org.freedesktop.DBus",
+		                        "AddMatch",
+		                        g_variant_new ("(s)", "type='signal',sender='" NM_DBUS_SERVICE "'"),
+		                        NULL,
+		                        G_DBUS_CALL_FLAGS_NONE,
+		                        -1,
+		                        NULL,
+		                        NULL,
+		                        NULL);
+	}
+
+	if (match_counter)
+		match_counter--;
+	if (match_counter)
+		return;
+
+	/* Remove what this proxy added. */
+	match = g_strdup_printf ("type='signal',sender='" NM_DBUS_SERVICE "',"
+	                         "interface='%s',path='%s'",
+	                         g_dbus_proxy_get_interface_name (proxy),
+	                         g_dbus_proxy_get_object_path (proxy));
+	g_dbus_connection_call (connection,
+	                        "org.freedesktop.DBus",
+	                        "/org/freedesktop/DBus",
+	                        "org.freedesktop.DBus",
+	                        "RemoveMatch",
+	                        g_variant_new ("(s)", match),
+	                        NULL,
+	                        G_DBUS_CALL_FLAGS_NONE,
+	                        -1,
+	                        NULL,
+	                        NULL,
+	                        NULL);
+	g_free (match);
+}
+
 GDBusProxy *
 _nm_dbus_new_proxy_for_connection (GDBusConnection *connection,
                                    const char *path,
@@ -123,6 +185,7 @@ _nm_dbus_new_proxy_for_connection (GDBusConnection *connection,
                                    GCancellable *cancellable,
                                    GError **error)
 {
+	GDBusProxy *proxy;
 	GType proxy_type;
 	const char *name;
 
@@ -135,13 +198,16 @@ _nm_dbus_new_proxy_for_connection (GDBusConnection *connection,
 	else
 		name = NM_DBUS_SERVICE;
 
-	return g_initable_new (proxy_type, cancellable, error,
-	                       "g-connection", connection,
-	                       "g-flags", NM_DBUS_PROXY_FLAGS,
-	                       "g-name", name,
-	                       "g-object-path", path,
-	                       "g-interface-name", interface,
-	                       NULL);
+	proxy = g_initable_new (proxy_type, cancellable, error,
+	                        "g-connection", connection,
+	                        "g-flags", NM_DBUS_PROXY_FLAGS,
+	                        "g-name", name,
+	                        "g-object-path", path,
+	                        "g-interface-name", interface,
+	                        NULL);
+	_nm_dbus_proxy_replace_match (proxy);
+
+	return proxy;
 }
 
 void
@@ -178,13 +244,15 @@ GDBusProxy *
 _nm_dbus_new_proxy_for_connection_finish (GAsyncResult *result,
                                           GError **error)
 {
-	GObject *source, *proxy;
+	GObject *source;
+	GDBusProxy *proxy;
 
 	source = g_async_result_get_source_object (result);
-	proxy = g_async_initable_new_finish (G_ASYNC_INITABLE (source), result, error);
+	proxy = G_DBUS_PROXY (g_async_initable_new_finish (G_ASYNC_INITABLE (source), result, error));
 	g_object_unref (source);
+	_nm_dbus_proxy_replace_match (proxy);
 
-	return G_DBUS_PROXY (proxy);
+	return proxy;
 }
 
 /* Binds the properties on a generated server-side GDBus object to the

src/org.freedesktop.NetworkManager.conf

@@ -123,5 +123,6 @@
         </policy>
 
 	<limit name="max_replies_per_connection">1024</limit>
+	<limit name="max_match_rules_per_connection">2048</limit>
 </busconfig>