Nat node is only on the GNS3 VM for the moment

Fix https://github.com/GNS3/gns3-gui/issues/1448

gns3server/compute/builtin/__init__.py

@@ -21,7 +21,7 @@ Builtin nodes server module.
 
 
 from ..base_manager import BaseManager
-from .builtin_node_factory import BuiltinNodeFactory
+from .builtin_node_factory import BuiltinNodeFactory, BUILTIN_NODES
 
 import logging
 log = logging.getLogger(__name__)
@@ -40,4 +40,7 @@ class Builtin(BaseManager):
         """
         :returns: List of node type supported by this class and computer
         """
-        return ['cloud', 'nat', 'ethernet_hub', 'ethernet_switch']
+        types = ['cloud', 'ethernet_hub', 'ethernet_switch']
+        if BUILTIN_NODES['nat'].is_supported():
+            types.append('nat')
+        return types

gns3server/compute/builtin/nodes/nat.py

@@ -41,6 +41,10 @@ class Nat(Cloud):
             }
         ]
 
+    @classmethod
+    def is_supported(self):
+        return socket.gethostname() == "gns3vm"
+
     def __json__(self):
         return {
             "name": self.name,