Fix #557 - mac addess collision when running IOU on multiple GNS3 servers

gns3server/compute/iou/utils/application_id.py

@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2017 GNS3 Technologies Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from ..iou_error import IOUError
+
+import logging
+log = logging.getLogger(__name__)
+
+
+def get_next_application_id(nodes):
+    """
+    Calculates free application_id from given nodes
+    :param nodes:
+    :raises IOUError when exceeds number
+    :return: integer first free id
+    """
+    used = set([n.properties.get('application_id') for n in nodes if n.node_type == 'iou'])
+    pool = set(range(1, 512))
+    try:
+        return (pool - used).pop()
+    except KeyError:
+        raise IOUError("Cannot create a new IOU VM (limit of 512 VMs reached)")