[neighbor_advertiser] Use existing tunnel if present for creating tun…

…nel mappings (sonic-net#1589)

scripts/neighbor_advertiser

@@ -169,9 +169,11 @@ def get_loopback_addr(ip_ver):
 def get_vlan_interfaces():
     vlan_info = config_db.get_table('VLAN')
     vlan_interfaces = []
-
+    vlan_intfs = config_db.get_table('VLAN_INTERFACE')
+    # Skip L2 VLANs
     for vlan_name in vlan_info:
-        vlan_interfaces.append(vlan_name)
+        if vlan_name in vlan_intfs:
+            vlan_interfaces.append(vlan_name)
 
     return vlan_interfaces
 
@@ -502,6 +504,14 @@ def reset_mirror_tunnel():
 # Set vxlan tunnel
 #
 
+def check_existing_tunnel():
+    vxlan_tunnel = config_db.get_table('VXLAN_TUNNEL')
+    if len(vxlan_tunnel):
+        global VXLAN_TUNNEL_NAME
+        VXLAN_TUNNEL_NAME = list(vxlan_tunnel.keys())[0]
+        return True
+    return False
+
 def add_vxlan_tunnel(dst_ipv4_addr):
     vxlan_tunnel_info = {
         'src_ip': get_loopback_addr(4),
@@ -517,12 +527,12 @@ def add_vxlan_tunnel_map():
             'vni': get_vlan_interface_vxlan_id(vlan_intf_name),
             'vlan': vlan_intf_name
         }
-
         config_db.set_entry('VXLAN_TUNNEL_MAP', (VXLAN_TUNNEL_NAME, VXLAN_TUNNEL_MAP_PREFIX + str(index)), vxlan_tunnel_map_info)
 
 
 def set_vxlan_tunnel(ferret_server_ip):
-    add_vxlan_tunnel(ferret_server_ip)
+    if not check_existing_tunnel():
+        add_vxlan_tunnel(ferret_server_ip)
     add_vxlan_tunnel_map()
     log.log_info('Finish setting vxlan tunnel; Ferret: {}'.format(ferret_server_ip))
 

tests/neighbor_advertiser_test.py

@@ -57,3 +57,12 @@ def test_neighbor_advertiser_slice(self, set_up):
             }
         )
         assert output == expected_output
+
+    def test_set_vxlan(self, set_up):
+        assert(neighbor_advertiser.check_existing_tunnel())
+        neighbor_advertiser.add_vxlan_tunnel_map()
+        tunnel_mapping = neighbor_advertiser.config_db.get_table('VXLAN_TUNNEL_MAP')
+        expected_mapping = {("vtep1", "map_1"): {"vni": "1000", "vlan": "Vlan1000"}, ("vtep1", "map_2"): {"vni": "2000", "vlan": "Vlan2000"}}
+        for key in expected_mapping.keys():
+            assert(key in tunnel_mapping.keys())
+            assert(expected_mapping[key] == tunnel_mapping[key])