net: Add subnet option into config

The subnet for IPv6 is now taken from separate parameter
in config file if provided.

lago/providers/libvirt/network.py

@@ -52,6 +52,9 @@ def name(self):
     def gw(self):
         return self._spec.get('gw')
 
+    def subnet(self):
+        return self._spec.get('subnet')
+
     def mtu(self):
         if self.libvirt_con.getLibVersion() > 3001001:
             return self._spec.get('mtu', '1500')
@@ -180,7 +183,10 @@ def _ipv6_prefix(self, subnet, const='fd8f:1391:3a82:'):
     def _libvirt_xml(self):
         net_raw_xml = libvirt_utils.get_template('net_nat_template.xml')
 
-        subnet = self.gw().split('.')[2]
+        subnet = self.subnet()
+        if not subnet:
+            subnet = self.gw().split('.')[2]
+
         ipv6_prefix = self._ipv6_prefix(subnet=subnet)
         mtu = self.mtu()
 

tests/functional-sdk/test_sdk_sanity.py

@@ -62,6 +62,10 @@ def init_str(images):
         dhcp:
           start: 100
           end: 254
+          
+      net-03:
+        type: nat
+        subnet: 250
     """
     )
     template = Environment(loader=BaseLoader()).from_string(init_template)
@@ -110,6 +114,12 @@ def test_custom_gateway(vms, nets, init_dict):
             assert nets[net_name].gw() == net['gw']
 
 
+def test_custom_subnet(vms, nets, init_dict):
+    for net_name, net in init_dict['nets'].iteritems():
+        if 'subnet' in net:
+            assert nets[net_name].subnet() == net['subnet']
+
+
 def test_vm_is_running(vms, vm_name):
     vm = vms[vm_name]
     assert vm.running()