lldp: only have GHashTable instance for LLDP neighbors when running

When the instance is not running (after creation or after stop), there
is no need to keep the GHashTable around.

Create it when needed (during start) and clear it during stop. This
makes it slightly cheaper to keep a NMLldpListener instance around,
if it's currently not running.

NMDevice already keeps the NMLldpListener around, even after stopping
it. It's not clear whether the instance will be started again, so also
clear the GHashTable. Also, one effect is that if you initially were in
a network with many LLDP neibors, after stop and start, the GHashTable
now gets recreated and may not need to allocate a large internal array
as before.

src/devices/nm-device.c

@@ -3845,7 +3845,8 @@ nm_device_update_dynamic_ip_setup (NMDevice *self)
 		/* FIXME: todo */
 	}
 
-	if (priv->lldp_listener && nm_lldp_listener_is_running (priv->lldp_listener)) {
+	if (   priv->lldp_listener
+	    && nm_lldp_listener_is_running (priv->lldp_listener)) {
 		nm_lldp_listener_stop (priv->lldp_listener);
 		if (!nm_lldp_listener_start (priv->lldp_listener, nm_device_get_ifindex (self), &error)) {
 			_LOGD (LOGD_DEVICE, "LLDP listener %p could not be restarted: %s",
@@ -7157,7 +7158,8 @@ lldp_init (NMDevice *self, gboolean restart)
 		gs_free_error GError *error = NULL;
 
 		if (priv->lldp_listener) {
-			if (restart && nm_lldp_listener_is_running (priv->lldp_listener))
+			if (   restart
+			    && nm_lldp_listener_is_running (priv->lldp_listener))
 				nm_lldp_listener_stop (priv->lldp_listener);
 		} else {
 			priv->lldp_listener = nm_lldp_listener_new ();

src/devices/nm-lldp-listener.c

@@ -30,16 +30,15 @@ NM_GOBJECT_PROPERTIES_DEFINE (NMLldpListener,
 );
 
 typedef struct {
-	char         *iface;
-	int           ifindex;
 	sd_lldp      *lldp_handle;
 	GHashTable   *lldp_neighbors;
+	GVariant     *variant;
 
 	/* the timestamp in nsec until which we delay updates. */
 	gint64        ratelimit_next_nsec;
 	guint         ratelimit_id;
 
-	GVariant     *variant;
+	int           ifindex;
 } NMLldpListenerPrivate;
 
 struct _NMLldpListener {
@@ -724,6 +723,8 @@ process_lldp_neighbor (NMLldpListener *self, sd_lldp_neighbor *neighbor_sd, gboo
 	g_return_if_fail (priv->lldp_handle);
 	g_return_if_fail (neighbor_sd);
 
+	nm_assert (priv->lldp_neighbors);
+
 	p_parse_error = _LOGT_ENABLED () ? &parse_error : NULL;
 
 	neigh = lldp_neighbor_new (neighbor_sd, p_parse_error);
@@ -831,6 +832,10 @@ nm_lldp_listener_start (NMLldpListener *self, int ifindex, GError **error)
 		goto err;
 	}
 
+	priv->lldp_neighbors = g_hash_table_new_full (lldp_neighbor_id_hash,
+	                                              lldp_neighbor_id_equal,
+	                                              (GDestroyNotify) lldp_neighbor_free, NULL);
+
 	_LOGD ("start");
 
 	return TRUE;
@@ -863,6 +868,7 @@ nm_lldp_listener_stop (NMLldpListener *self)
 
 		size = g_hash_table_size (priv->lldp_neighbors);
 		g_hash_table_remove_all (priv->lldp_neighbors);
+		nm_clear_pointer (&priv->lldp_neighbors, g_hash_table_unref);
 		if (   size > 0
 		    || priv->ratelimit_id != 0)
 			changed = TRUE;
@@ -897,8 +903,8 @@ nm_lldp_listener_get_neighbors (NMLldpListener *self)
 	priv = NM_LLDP_LISTENER_GET_PRIVATE (self);
 
 	if (G_UNLIKELY (!priv->variant)) {
-		GVariantBuilder array_builder;
 		gs_free LldpNeighbor **neighbors = NULL;
+		GVariantBuilder array_builder;
 		guint i, n;
 
 		g_variant_builder_init (&array_builder, G_VARIANT_TYPE ("aa{sv}"));
@@ -932,12 +938,6 @@ get_property (GObject *object, guint prop_id,
 static void
 nm_lldp_listener_init (NMLldpListener *self)
 {
-	NMLldpListenerPrivate *priv = NM_LLDP_LISTENER_GET_PRIVATE (self);
-
-	priv->lldp_neighbors = g_hash_table_new_full (lldp_neighbor_id_hash,
-	                                              lldp_neighbor_id_equal,
-	                                              (GDestroyNotify) lldp_neighbor_free, NULL);
-
 	_LOGT ("lldp listener created");
 }
 
@@ -962,7 +962,6 @@ finalize (GObject *object)
 	NMLldpListenerPrivate *priv = NM_LLDP_LISTENER_GET_PRIVATE (self);
 
 	nm_lldp_listener_stop (self);
-	g_hash_table_unref (priv->lldp_neighbors);
 
 	nm_clear_g_variant (&priv->variant);