MXS-1689 Properly check for duplicate port/socket of service

It is now impossible to create two listeners for a service that
would listen on the same port/socket (as before), but the error
message is now sensible and provides detailed information to the
user.

include/maxscale/service.h

@@ -236,6 +236,24 @@ bool serviceAddBackend(SERVICE *service, SERVER *server);
  */
 bool serviceHasBackend(SERVICE *service, SERVER *server);
 
+/**
+ * @brief Find listener with specified properties.
+ *
+ * @param service Service to check
+ * @param socket  Listener socket path
+ * @param address Listener address
+ * @param port    Listener port number
+ *
+ * @note Either socket should be NULL and port non-zero or socket
+ *       non-NULL and port zero.
+ *
+ * @return True if service has the listener
+ */
+SERV_LISTENER* service_find_listener(SERVICE* service,
+                                     const char* socket,
+                                     const char* address,
+                                     unsigned short port);
+
 /**
  * @brief Check if a service has a listener
  *

server/core/config.cc

@@ -3456,13 +3456,17 @@ int create_new_listener(CONFIG_CONTEXT *obj)
         SERVICE *service = service_find(service_name);
         if (service)
         {
+            SERV_LISTENER *listener;
             SSL_LISTENER *ssl_info = make_ssl_structure(obj, true, &error_count);
             if (socket)
             {
-                if (serviceHasListener(service, obj->object, protocol, address, 0))
+                listener = service_find_listener(service, socket, NULL, 0);
+
+                if (listener)
                 {
-                    MXS_ERROR("Listener '%s' for service '%s' already has a socket at '%s.",
+                    MXS_ERROR("Creation of listener '%s' for service '%s' failed, because "
-                              obj->object, service_name, socket);
+                              "listener '%s' already listens on the socket '%s'.",
+                              obj->object, raw_service_name, listener->name, socket);
                     error_count++;
                 }
                 else
@@ -3474,12 +3478,13 @@ int create_new_listener(CONFIG_CONTEXT *obj)
 
             if (port)
             {
-                if (serviceHasListener(service, obj->object, protocol, address, atoi(port)))
+                listener = service_find_listener(service, NULL, address, atoi(port));
+
+                if (listener)
                 {
-                    MXS_ERROR("Listener '%s', for service '%s', already have port %s.",
+                    MXS_ERROR("Creation of listener '%s' for service '%s' failed, because "
-                              obj->object,
+                              "listener '%s' already listens on the port %s.",
-                              service_name,
+                              obj->object, raw_service_name, listener->name, port);
-                              port);
                     error_count++;
                 }
                 else

server/core/service.cc

@@ -806,6 +806,46 @@ SERV_LISTENER* serviceCreateListener(SERVICE *service, const char *name, const c
     return proto;
 }
 
+SERV_LISTENER* service_find_listener(SERVICE* service,
+                                     const char* socket,
+                                     const char* address, unsigned short port)
+{
+    LISTENER_ITERATOR iter;
+
+    for (SERV_LISTENER *listener = listener_iterator_init(service, &iter);
+         listener; listener = listener_iterator_next(&iter))
+    {
+        if (listener_is_active(listener))
+        {
+            bool is_same_port = false;
+
+            if (port && (port == listener->port) &&
+                ((address && listener->address && strcmp(listener->address, address) == 0) ||
+                 (address == NULL && listener->address == NULL)))
+            {
+                is_same_port = true;
+            }
+
+            bool is_same_socket = false;
+
+            if (!is_same_port)
+            {
+                if (socket && listener->address && strcmp(listener->address, socket) == 0)
+                {
+                    is_same_socket = true;
+                }
+            }
+
+            if (is_same_port || is_same_socket)
+            {
+                return listener;
+            }
+        }
+    }
+
+    return NULL;
+}
+
 /**
  * Check if a protocol/port pair is part of the service
  *