nat: T3206: unable to delete only rules but keep destination node

(cherry picked from commit 9db4dbc4a84ff1a110617cb3c7849d7c9d4a62e7)

2 files changed, 12 insertions, 2 deletions

diff --git a/smoketest/scripts/cli/test_nat.py b/smoketest/scripts/cli/test_nat.py
index 7ca82f86f..b82805661 100755
--- a/smoketest/scripts/cli/test_nat.py
+++ b/smoketest/scripts/cli/test_nat.py
@@ -138,7 +138,6 @@ class TestNAT(unittest.TestCase):
             else:
                 self.assertEqual(iface, inbound_iface_200)
 
-
     def test_snat_required_translation_address(self):
         # T2813: Ensure translation address is specified
         rule = '5'
@@ -156,5 +155,16 @@ class TestNAT(unittest.TestCase):
         self.session.set(src_path + ['rule', rule, 'translation', 'address', 'masquerade'])
         self.session.commit()
 
+    def test_nat_no_rules(self):
+        # T3206: deleting all rules but keep the direction 'destination' or
+        # 'source' resulteds in KeyError: 'rule'.
+        #
+        # Test that both 'nat destination' and 'nat source' nodes can exist
+        # without any rule
+        self.session.set(src_path)
+        self.session.set(dst_path)
+        self.session.commit()
+
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)
diff --git a/src/conf_mode/nat.py b/src/conf_mode/nat.py
index 1ccec3d2e..2d98cb11b 100755
--- a/src/conf_mode/nat.py
+++ b/src/conf_mode/nat.py
@@ -88,7 +88,7 @@ def get_config(config=None):
     for direction in ['source', 'destination']:
         if direction in nat:
             default_values = defaults(base + [direction, 'rule'])
-            for rule in nat[direction]['rule']:
+            for rule in dict_search(f'{direction}.rule', nat) or []:
                 nat[direction]['rule'][rule] = dict_merge(default_values,
                     nat[direction]['rule'][rule])