lldp: delay change notification for LLDP neighbor events

We already rate limit change events by two seconds. When we notice
that something changed, we call data_changed_schedule().

Previously, that would immediately issue the change notification,
if ratelimiting currently was not in effect. That means, if we happen
go receive two LLDP neighbor events in short succession, then the
first one will trigger the change notification right away, while
the second will be rate limited.

Avoid that by always issue scheduling the change notification in
the background. And if we currently are not rate limited, with
an idle handler with low priority.

1 files changed, 22 insertions, 14 deletions

diff --git a/src/devices/nm-lldp-listener.c b/src/devices/nm-lldp-listener.c
index 91aee3b3bc..ff18975724 100644
--- a/src/devices/nm-lldp-listener.c
+++ b/src/devices/nm-lldp-listener.c
@@ -16,8 +16,8 @@
 
 #include "systemd/nm-sd.h"
 
-#define MAX_NEIGHBORS         128
-#define MIN_UPDATE_INTERVAL_NS (2 * NM_UTILS_NSEC_PER_SEC)
+#define MAX_NEIGHBORS            128
+#define MIN_UPDATE_INTERVAL_NSEC (2 * NM_UTILS_NSEC_PER_SEC)
 
 #define LLDP_MAC_NEAREST_BRIDGE          ((const struct ether_addr *) ((uint8_t[ETH_ALEN]) { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x0e }))
 #define LLDP_MAC_NEAREST_NON_TPMR_BRIDGE ((const struct ether_addr *) ((uint8_t[ETH_ALEN]) { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x03 }))
@@ -36,7 +36,7 @@ typedef struct {
 	GHashTable   *lldp_neighbors;
 
 	/* the timestamp in nsec until which we delay updates. */
-	gint64        ratelimit_next;
+	gint64        ratelimit_next_nsec;
 	guint         ratelimit_id;
 
 	GVariant     *variant;
@@ -678,7 +678,7 @@ data_changed_timeout (gpointer user_data)
 	priv = NM_LLDP_LISTENER_GET_PRIVATE (self);
 
 	priv->ratelimit_id = 0;
-	priv->ratelimit_next = nm_utils_get_monotonic_timestamp_nsec() + MIN_UPDATE_INTERVAL_NS;
+	priv->ratelimit_next_nsec = nm_utils_get_monotonic_timestamp_nsec() + MIN_UPDATE_INTERVAL_NSEC;
 	data_changed_notify (self, priv);
 	return G_SOURCE_REMOVE;
 }
@@ -687,18 +687,25 @@ static void
 data_changed_schedule (NMLldpListener *self)
 {
 	NMLldpListenerPrivate *priv = NM_LLDP_LISTENER_GET_PRIVATE (self);
-	gint64 now;
+	gint64 now_nsec;
 
-	now = nm_utils_get_monotonic_timestamp_nsec ();
-	if (now < priv->ratelimit_next) {
-		if (!priv->ratelimit_id)
-			priv->ratelimit_id = g_timeout_add (NM_UTILS_NSEC_TO_MSEC_CEIL (priv->ratelimit_next - now), data_changed_timeout, self);
+	if (priv->ratelimit_id != 0)
+		return;
+
+	now_nsec = nm_utils_get_monotonic_timestamp_nsec ();
+	if (now_nsec < priv->ratelimit_next_nsec) {
+		priv->ratelimit_id = g_timeout_add_full (G_PRIORITY_LOW,
+		                                         NM_UTILS_NSEC_TO_MSEC_CEIL (priv->ratelimit_next_nsec - now_nsec),
+		                                         data_changed_timeout,
+		                                         self,
+		                                         NULL);
 		return;
 	}
 
-	nm_clear_g_source (&priv->ratelimit_id);
-	priv->ratelimit_next = now + MIN_UPDATE_INTERVAL_NS;
-	data_changed_notify (self, priv);
+	priv->ratelimit_id = g_idle_add_full (G_PRIORITY_LOW,
+	                                      data_changed_timeout,
+	                                      self,
+	                                      NULL);
 }
 
 static void
@@ -856,12 +863,13 @@ nm_lldp_listener_stop (NMLldpListener *self)
 
 		size = g_hash_table_size (priv->lldp_neighbors);
 		g_hash_table_remove_all (priv->lldp_neighbors);
-		if (size || priv->ratelimit_id)
+		if (   size > 0
+		    || priv->ratelimit_id != 0)
 			changed = TRUE;
 	}
 
 	nm_clear_g_source (&priv->ratelimit_id);
-	priv->ratelimit_next = 0;
+	priv->ratelimit_next_nsec = 0;
 	priv->ifindex = 0;
 
 	if (changed)