[config]: Add loopback interfaces to interface name checker (#1869)

* Add loopback interfaces to interface name checker

Signed-off-by: Ze Gan <ganze718@gmail.com>

* Add unitest for interface name checker

Signed-off-by: Ze Gan <ganze718@gmail.com>

config/main.py

@@ -292,6 +292,7 @@ def interface_name_is_valid(config_db, interface_name):
     port_dict = config_db.get_table('PORT')
     port_channel_dict = config_db.get_table('PORTCHANNEL')
     sub_port_intf_dict = config_db.get_table('VLAN_SUB_INTERFACE')
+    loopback_dict = config_db.get_table('LOOPBACK_INTERFACE')
 
     if clicommon.get_interface_naming_mode() == "alias":
         interface_name = interface_alias_to_name(config_db, interface_name)
@@ -311,6 +312,10 @@ def interface_name_is_valid(config_db, interface_name):
             for sub_port_intf_name in sub_port_intf_dict:
                 if interface_name == sub_port_intf_name:
                     return True
+        if loopback_dict:
+            for loopback_name in loopback_dict:
+                if interface_name == loopback_name:
+                    return True
     return False
 
 def interface_name_to_alias(config_db, interface_name):

tests/config_int_name_test.py

@@ -0,0 +1,12 @@
+from unittest import mock
+
+from utilities_common.db import Db
+
+import config.main as config
+
+
+def test_interface_name_checker():
+    db = Db()
+    db.cfgdb.set_entry("LOOPBACK_INTERFACE", "Loopback0", {"NULL": "NULL"})
+
+    assert config.interface_name_is_valid(db.cfgdb, "Loopback0")