Fix some retained topic memory not being cleared immediately after used.

ChangeLog.txt

@@ -1,6 +1,7 @@
 Broker:
 - Fix $SYS messages being expired after 60 seconds and hence unchanged values
   disappearing.
+- Fix some retained topic memory not being cleared immediately after used.
 
 2.0.15 - 2022-08-16
 ===================

src/retain.c

@@ -72,6 +72,25 @@ int retain__init(void)
 }
 
 
+void retain__clean_empty_hierarchy(struct mosquitto__retainhier *retainhier)
+{
+	struct mosquitto__retainhier *parent;
+
+	while(retainhier){
+		if(retainhier->children || retainhier->retained || retainhier->parent == NULL){
+			/* Entry is being used */
+			return;
+		}else{
+			HASH_DELETE(hh, retainhier->parent->children, retainhier);
+			mosquitto__free(retainhier->topic);
+			parent = retainhier->parent;
+			mosquitto__free(retainhier);
+			retainhier = parent;
+		}
+	}
+}
+
+
 int retain__store(const char *topic, struct mosquitto_msg_store *stored, char **split_topics)
 {
 	struct mosquitto__retainhier *retainhier;
@@ -124,6 +143,7 @@ int retain__store(const char *topic, struct mosquitto_msg_store *stored, char **
 #endif
 	}else{
 		retainhier->retained = NULL;
+		retain__clean_empty_hierarchy(retainhier);
 	}
 
 	return MOSQ_ERR_SUCCESS;

test/broker/04-retain-clear-multiple.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+
+# Exercise multi-level retain clearing
+
+from mosq_test_helper import *
+
+def send_retain(port, topic, payload):
+    connect_packet = mosq_test.gen_connect("retain-clear-test")
+    connack_packet = mosq_test.gen_connack(rc=0)
+
+    publish_packet = mosq_test.gen_publish(topic, qos=1, mid=1, payload=payload, retain=True)
+    puback_packet = mosq_test.gen_puback(mid=1)
+
+    sock = mosq_test.do_client_connect(connect_packet, connack_packet, timeout=4, port=port)
+    mosq_test.do_send_receive(sock, publish_packet, puback_packet, f"set retain {topic}")
+    sock.close()
+
+def do_test():
+    rc = 1
+    connect_packet = mosq_test.gen_connect("retain-clear-test")
+    connack_packet = mosq_test.gen_connack(rc=0)
+
+    subscribe_packet = mosq_test.gen_subscribe(1, "#", 0)
+    suback_packet = mosq_test.gen_suback(1, 0)
+
+    retain1_packet = mosq_test.gen_publish("1/2/3/4/5/6/7", qos=0, payload="retained message", retain=True)
+    retain2_packet = mosq_test.gen_publish("1/2/3/4", qos=0, payload="retained message", retain=True)
+    retain3_packet = mosq_test.gen_publish("1", qos=0, payload="retained message", retain=True)
+
+    port = mosq_test.get_port()
+    broker = mosq_test.start_broker(filename=os.path.basename(__file__), port=port)
+
+    try:
+        send_retain(port, "1/2/3/4/5/6/7", "retained message")
+        send_retain(port, "1/2/3/4", "retained message")
+        send_retain(port, "1", "retained message")
+
+        sock = mosq_test.do_client_connect(connect_packet, connack_packet, port=port)
+        mosq_test.do_send_receive(sock, subscribe_packet, suback_packet, "suback")
+        mosq_test.expect_packet(sock, "retain3", retain3_packet)
+        mosq_test.expect_packet(sock, "retain2", retain2_packet)
+        mosq_test.expect_packet(sock, "retain1", retain1_packet)
+        sock.close()
+
+        send_retain(port, "1/2/3/4", None)
+
+        sock = mosq_test.do_client_connect(connect_packet, connack_packet, port=port)
+        mosq_test.do_send_receive(sock, subscribe_packet, suback_packet, "suback")
+        mosq_test.expect_packet(sock, "retain3", retain3_packet)
+        mosq_test.expect_packet(sock, "retain1", retain1_packet)
+        sock.close()
+
+        send_retain(port, "1/2/3/4/5/6/7", None)
+
+        sock = mosq_test.do_client_connect(connect_packet, connack_packet, port=port)
+        mosq_test.do_send_receive(sock, subscribe_packet, suback_packet, "suback")
+        mosq_test.expect_packet(sock, "retain3", retain3_packet)
+        sock.close()
+
+        send_retain(port, "1", None)
+
+        sock = mosq_test.do_client_connect(connect_packet, connack_packet, port=port)
+        mosq_test.do_send_receive(sock, subscribe_packet, suback_packet, "suback")
+        mosq_test.do_ping(sock)
+        sock.close()
+
+        rc = 0
+    except mosq_test.TestError:
+        pass
+    finally:
+        broker.terminate()
+        broker.wait()
+        (stdo, stde) = broker.communicate()
+        if rc:
+            print(stde.decode('utf-8'))
+            exit(rc)
+
+do_test()
+exit(0)
+

test/broker/Makefile

@@ -90,6 +90,7 @@ msg_sequence_test:
 	./04-retain-check-source-persist-diff-port.py
 	./04-retain-check-source-persist.py
 	./04-retain-check-source.py
+	./04-retain-clear-multiple.py
 	./04-retain-qos0-clear.py
 	./04-retain-qos0-fresh.py
 	./04-retain-qos0-repeated.py

test/broker/test.py

@@ -68,6 +68,7 @@ tests = [
 
     (1, './04-retain-check-source-persist.py'),
     (1, './04-retain-check-source.py'),
+	(1, './04-retain-clear-multiple.py'),
     (1, './04-retain-qos0-clear.py'),
     (1, './04-retain-qos0-fresh.py'),
     (1, './04-retain-qos0-repeated.py'),