purge old entries from SSRC hash table if it gets too full

fixes #417

Change-Id: I4da50858d3c4959687b341b7c0856a868c87ffa7

daemon/ssrc.c

@@ -21,6 +21,7 @@ static struct ssrc_entry *create_ssrc_entry(u_int32_t ssrc) {
 }
 static void add_ssrc_entry(struct ssrc_entry *ent, struct ssrc_hash *ht) {
 	g_hash_table_replace(ht->ht, &ent->ssrc, ent);
+	g_queue_push_tail(&ht->q, ent);
 }
 static void free_sender_report(struct ssrc_sender_report_item *i) {
 	g_slice_free1(sizeof(*i), i);
@@ -78,11 +79,11 @@ restart:
 
 	rwlock_lock_w(&ht->lock);
 
-	if (G_UNLIKELY(g_hash_table_size(ht->ht) > 20)) { // arbitrary limit
-		rwlock_unlock_w(&ht->lock);
-		free_ssrc_entry(ent);
-		ilog(LOG_INFO, "SSRC hash table exceeded size limit (trying to add %u)", ssrc);
-		return NULL;
+	while (G_UNLIKELY(ht->q.length > 20)) { // arbitrary limit
+		struct ssrc_entry *old_ent = g_queue_pop_head(&ht->q);
+		ilog(LOG_DEBUG, "SSRC hash table exceeded size limit (trying to add %u) - deleting SSRC %u",
+				ssrc, old_ent->ssrc);
+		g_hash_table_remove(ht->ht, &old_ent->ssrc);
 	}
 
 	if (g_hash_table_lookup(ht->ht, &ssrc)) {
@@ -101,6 +102,7 @@ void free_ssrc_hash(struct ssrc_hash **ht) {
 	if (!*ht)
 		return;
 	g_hash_table_destroy((*ht)->ht);
+	g_queue_clear(&(*ht)->q);
 	g_slice_free1(sizeof(**ht), *ht);
 	*ht = NULL;
 }

daemon/ssrc.h

@@ -21,6 +21,7 @@ enum ssrc_dir;
 
 struct ssrc_hash {
 	GHashTable *ht;
+	GQueue q;
 	rwlock_t lock;
 };
 struct ssrc_ctx {