NSX|V: learn the default L3 section ID

Do not use a hard coded value for the defualt section ID.

Change-Id: I74f6f3ae3d2347e1f8cf60ec8e4b99da04082057

vmware_nsx/plugins/nsx_v/plugin.py

@@ -426,7 +426,11 @@ class NsxVPluginV2(addr_pair_db.AllowedAddressPairsMixin,
                 self.nsx_v.vcns.update_section_by_id(
                     section_id, 'ip', section_req_body)
             else:
-                h, c = self.nsx_v.vcns.create_section('ip', section_req_body)
+                # cluster section does not exists. Create it above the
+                # default l3 section
+                l3_id = self.nsx_v.vcns.get_default_l3_id()
+                h, c = self.nsx_v.vcns.create_section('ip', section_req_body,
+                                                      insert_before=l3_id)
                 section_id = self.nsx_sg_utils.parse_and_get_section_id(c)
         return section_id
 

vmware_nsx/plugins/nsx_v/vshield/vcns.py

@@ -627,6 +627,16 @@ class Vcns(object):
         return self.do_request(HTTP_GET, section_uri, format='xml',
                                decode=False)
 
+    def get_default_l3_id(self):
+        """Retrieve the id of the default l3 section."""
+        h, firewall_config = self.get_dfw_config()
+        root = utils.normalize_xml(firewall_config)
+        for child in root:
+            if str(child.tag) == 'layer3Sections':
+                sections = list(child.iter('section'))
+                default = sections[-1]
+                return default.attrib['id']
+
     def get_dfw_config(self):
         uri = FIREWALL_PREFIX
         return self.do_request(HTTP_GET, uri, decode=False, format='xml')

vmware_nsx/tests/unit/nsx_v/vshield/fake_vcns.py

@@ -1006,6 +1006,9 @@ class FakeVcns(object):
     def update_section_by_id(self, id, type, request):
         pass
 
+    def get_default_l3_id(self):
+        return 1234
+
     def get_dfw_config(self):
         response = ""
         for sec_id in range(0, self._sections['section_ids']):