verify: T2587: allow MTU < 1280 when IPv6 is disabled on an interface

2 files changed, 35 insertions, 6 deletions

diff --git a/python/vyos/configverify.py b/python/vyos/configverify.py
index 833ef3772..d3ca56d11 100644
--- a/python/vyos/configverify.py
+++ b/python/vyos/configverify.py
@@ -60,19 +60,19 @@ def verify_mtu_ipv6(config):
             error_msg = f'IPv6 address will be configured on interface "{interface}" ' \
                         f'thus the minimum MTU requirement is {min_mtu}!'
 
-            if not dict_search('ipv6.address.no_default_link_local', config):
-                raise ConfigError('link-local ' + error_msg)
-
             for address in (dict_search('address', config) or []):
                 if address in ['dhcpv6'] or is_ipv6(address):
                     raise ConfigError(error_msg)
 
-            if dict_search('ipv6.address.autoconf', config):
-                raise ConfigError(error_msg)
+            tmp = dict_search('ipv6.address', config)
+            if tmp and 'no_default_link_local' not in tmp:
+                raise ConfigError('link-local ' + error_msg)
 
-            if dict_search('ipv6.address.eui64', config):
+            if tmp and 'autoconf' in tmp:
                 raise ConfigError(error_msg)
 
+            if tmp and 'eui64' in tmp:
+                raise ConfigError(error_msg)
 
 def verify_vrf(config):
     """
diff --git a/smoketest/scripts/cli/base_interfaces_test.py b/smoketest/scripts/cli/base_interfaces_test.py
index 7dc92feb5..653cc91f9 100644
--- a/smoketest/scripts/cli/base_interfaces_test.py
+++ b/smoketest/scripts/cli/base_interfaces_test.py
@@ -162,16 +162,45 @@ class BasicInterfaceTest:
             """ Testcase if MTU can be changed on interface """
             if not self._test_mtu:
                 return None
+
+            for intf in self._interfaces:
+                base = self._base_path + [intf]
+                self.session.set(base + ['mtu', self._mtu])
+                for option in self._options.get(intf, []):
+                    self.session.set(base + option.split())
+
+            # commit interface changes
+            self.session.commit()
+
+            # verify changed MTU
+            for intf in self._interfaces:
+                self._mtu_test(intf)
+
+        def test_change_mtu_1200(self):
+            """ Testcase if MTU can be changed to 1200 on non IPv6 enabled interfaces """
+            if not self._test_mtu:
+                return None
+
+            old_mtu = self._mtu
+            self._mtu = '1200'
+
             for intf in self._interfaces:
                 base = self._base_path + [intf]
                 self.session.set(base + ['mtu', self._mtu])
+                self.session.set(base + ['ipv6', 'address', 'no-default-link-local'])
+
                 for option in self._options.get(intf, []):
                     self.session.set(base + option.split())
 
+            # commit interface changes
             self.session.commit()
+
+            # verify changed MTU
             for intf in self._interfaces:
                 self._mtu_test(intf)
 
+            self._mtu = old_mtu
+
         def test_8021q_vlan(self):
             """ Testcase for 802.1q VLAN interfaces """
             if not self._test_vlan: