broker: fix queue_qos0_messages behaviour

Prior, offline qos0 clients had an unlimited queue depth when
queue_qos0_messages was true.

Signed-off-by: Karl Palsson <karlp@etactica.com>

ChangeLog.txt

@@ -33,6 +33,7 @@ Broker:
 - new $SYS/broker/store/messages/bytes
 - max_queued_bytes feature to limit queues by real size rather than
   than just message count. Closes Eclipse #452919 or Github #100
+- queue_qos0_messages was not observing max_queued_** limits
 
 Client library:
 - Outgoing messages with QoS>1 are no longer retried after a timeout period.

src/database.c

@@ -58,25 +58,36 @@ static bool db__ready_for_flight(struct mosquitto *context, int qos)
 
 /**
  * For a given client context, are more messages allowed to be queued?
+ * It is assumed that inflight checks and queue_qos0 checks have already
+ * been made.
  * @param context client of interest
+ * @param qos destination qos for the packet of interest
  * @return true if queuing is allowed, false if should be dropped
  */
-static bool db__ready_for_queue(struct mosquitto *context)
+static bool db__ready_for_queue(struct mosquitto *context, int qos)
 {
 	if(max_queued == 0 && max_queued_bytes == 0){
 		return true;
 	}
 
+	unsigned long source_bytes = context->msg_bytes12;
+	int source_count = context->msg_count12;
 	unsigned long adjust_bytes = max_inflight_bytes;
 	int adjust_count = max_inflight;
+
 	/* nothing in flight for offline clients */
 	if(context->sock == INVALID_SOCKET){
 		adjust_bytes = 0;
 		adjust_count = 0;
 	}
 
-	bool valid_bytes = context->msg_bytes12 - adjust_bytes < max_queued_bytes;
-	bool valid_count = context->msg_count12 - adjust_count < max_queued;
+	if(qos == 0){
+		source_bytes = context->msg_bytes;
+		source_count = context->msg_count;
+	}
+
+	bool valid_bytes = source_bytes - adjust_bytes < max_queued_bytes;
+	bool valid_count = source_count - adjust_count < max_queued;
 
 	if(max_queued_bytes == 0){
 		return valid_count;
@@ -388,7 +399,7 @@ int db__message_insert(struct mosquitto_db *db, struct mosquitto *context, uint1
 					return 1;
 				}
 			}
-		}else if(db__ready_for_queue(context)){
+		}else if(db__ready_for_queue(context, qos)){
 			state = mosq_ms_queued;
 			rc = 2;
 		}else{