If we can found a common subnet we return the host binding for link

creation

Fix #773

gns3server/controller/compute.py

@@ -618,4 +618,8 @@ class Compute:
                 other_network = ipaddress.ip_network("{}/{}".format(other_interface["ip_address"], other_interface["netmask"]), strict=False)
                 if this_network.overlaps(other_network):
                     return (this_interface["ip_address"], other_interface["ip_address"])
+
+        # Perhaps the user has correct network gateway
+        if (self.host_ip not in ('0.0.0.0', '127.0.0.1') and other_compute.host_ip not in ('0.0.0.0', '127.0.0.1')):
+            return (self.host_ip, other_compute.host_ip)
         raise ValueError("No common subnet for compute {} and {}".format(self.name, other_compute.name))

tests/controller/test_compute.py

@@ -447,7 +447,6 @@ def test_get_ip_on_same_subnet(controller, async_run):
     assert async_run(compute1.get_ip_on_same_subnet(compute2)) == ("192.168.1.1", "192.168.1.2")
 
     #No common interface
-    # Case 2 compute2 host is on a different network but a common interface is available
     compute2 = Compute("compute2", host="127.0.0.1", controller=controller)
     compute2._interfaces_cache = [
         {
@@ -481,5 +480,4 @@ def test_get_ip_on_same_subnet(controller, async_run):
             "netmask": "255.255.0.0"
         },
     ]
-    with pytest.raises(ValueError):
-        assert async_run(compute1.get_ip_on_same_subnet(compute2))
+    assert async_run(compute1.get_ip_on_same_subnet(compute2)) == ('192.168.2.1', '192.168.1.2')