Loopback address routing should be invalid

Host route validators should reject loopback CIDRs.

Change-Id: Ifa545242224bdc80a934b529e44b25b4492d4e0b
CLoses-bug: 1834012

neutron_lib/api/validators/__init__.py

@@ -680,6 +680,8 @@ def validate_route_cidr(data, valid_values=None):
             msg = _("'%(data)s' is not a recognized CIDR,"
                     " '%(cidr)s' is recommended") % {"data": data,
                                                      "cidr": net.cidr}
+        elif net.is_loopback():
+            msg = _("'%(data)s' is not a routable CIDR") % {"data": data}
         else:
             return
     except Exception:

neutron_lib/tests/unit/api/validators/test_validators.py

@@ -742,6 +742,12 @@ class TestAttributeValidation(base.BaseTestCase):
                                                    "cidr": "192.0.0.0/8"}
         self.assertEqual(error, msg)
 
+        # Invalid - loopback CIDR
+        cidr = "127.0.0.0/8"
+        msg = validators.validate_route_cidr(cidr, None)
+        error = _("'%(data)s' is not a routable CIDR") % {"data": cidr}
+        self.assertEqual(error, msg)
+
         # Invalid - CIDR format error
         cidr = 'invalid'
         msg = validators.validate_route_cidr(cidr, None)

releasenotes/notes/validator_check_route_loopback-bc2166b10a754c77.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Static route validator should verify that routed CIDR isn't a loopback.
+    Loopback addresses should not be routable.
+    Bug: `1834012 <https://bugs.launchpad.net/neutron/+bug/1834012>`_
+