[CORD-3184] Adding compute-nodes to fabric config

Change-Id: Ief7158e635cae5df89a3bbd6c210e625bc7bb1fc
diff --git a/xos/synchronizer/model_policies/model_policy_compute_nodes.py b/xos/synchronizer/model_policies/model_policy_compute_nodes.py
new file mode 100644
index 0000000..91efd40
--- /dev/null
+++ b/xos/synchronizer/model_policies/model_policy_compute_nodes.py
@@ -0,0 +1,100 @@
+
+# Copyright 2017-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import ipaddress
+import random
+from synchronizers.new_base.modelaccessor import NodeToSwitchPort, PortInterface, model_accessor
+from synchronizers.new_base.policy import Policy
+
+from xosconfig import Config
+from multistructlog import create_logger
+
+from helpers import Helpers
+
+log = create_logger(Config().get('logging'))
+
+class ComputeNodePolicy(Policy):
+    model_name = "NodeToSwitchPort"
+
+    @staticmethod
+    def getLastAddress(network):
+        return str(network.network_address + network.num_addresses - 2) + "/" + str(network.prefixlen)
+        # return ipaddress.ip_interface(network.network_address + network.num_addresses - 2)
+
+    @staticmethod
+    def getPortCidrByIp(ip):
+        interface = ipaddress.ip_interface(ip)
+        network = ipaddress.ip_network(interface.network)
+        cidr = ComputeNodePolicy.getLastAddress(network)
+        return cidr
+
+    @staticmethod
+    def generateVlan(used_vlans):
+        availabel_tags = range(16, 4093)
+        valid_tags = list(set(availabel_tags) - set(used_vlans))
+        if len(valid_tags) == 0:
+            raise Exception("No VLANs left")
+        return random.choice(valid_tags)
+
+    @staticmethod
+    def getVlanByCidr(subnet):
+        # vlanUntagged is unique per subnet
+        same_subnet_ifaces = PortInterface.objects.filter(ips=str(subnet))
+
+        if len(same_subnet_ifaces) > 0:
+            return same_subnet_ifaces[0].vlanUntagged
+        else:
+            PortInterface.objects.all()
+            used_vlans = list(set([i.vlanUntagged for i in same_subnet_ifaces]))
+            log.info("MODEL_POLICY: used vlans", vlans=used_vlans, subnet=subnet)
+            return ComputeNodePolicy.generateVlan(used_vlans)
+
+    def handle_create(self, node_to_port):
+        return self.handle_update(node_to_port)
+
+    def handle_update(self, node_to_port):
+        log.info("MODEL_POLICY: NodeToSwitchPort %s handle update" % node_to_port.id, node=node_to_port.node, port=node_to_port.port, switch=node_to_port.port.switch)
+
+        compute_node = node_to_port.node
+
+        cidr = ComputeNodePolicy.getPortCidrByIp(compute_node.dataPlaneIp)
+
+        # check if an interface already exists
+        try:
+            PortInterface.objects.get(
+                port_id=node_to_port.port.id,
+                name=compute_node.dataPlaneIntf,
+                ips=str(cidr)
+            )
+        except IndexError:
+
+            vlan = self.getVlanByCidr(cidr)
+
+            log.info("MODEL_POLICY: choosen vlan", vlan=vlan, cidr=cidr)
+
+            interface = PortInterface(
+                port_id=node_to_port.port.id,
+                name=compute_node.dataPlaneIntf,
+                ips=str(cidr),
+                vlanUntagged=vlan
+            )
+
+            interface.save()
+        
+        # TODO if the model is updated I need to remove the old interface, how?
+
+
+    def handle_delete(self, node_to_port):
+        pass