bond: T8023: validate member interface min/max MTU

It is impossible to set the bond interface MTU to be larger or lower then the
limits of the underlaying interface MTU. Add proper commit validation and
smoketest.

2 files changed, 35 insertions, 0 deletions

diff --git a/smoketest/scripts/cli/test_interfaces_bonding.py b/smoketest/scripts/cli/test_interfaces_bonding.py
index 21918282d..b6eb5328d 100755
--- a/smoketest/scripts/cli/test_interfaces_bonding.py
+++ b/smoketest/scripts/cli/test_interfaces_bonding.py
@@ -334,5 +334,29 @@ class BondingInterfaceTest(BasicInterfaceTest.TestCase):
 
             id = int(id) + 1
 
+    def test_bonding_member_mtu(self):
+        # This Smoketest only works on our CI platform where we force the NIC
+        # to virtio and an MTU of only 1500 bytes max
+        if not os.path.exists('/tmp/vyos.smoketests.hint'):
+            self.skipTest('Not running under VyOS CI/CD QEMU environment!')
+
+        for interface in self._interfaces:
+            for option in self._options.get(interface, []):
+                self.cli_set(self._base_path + [interface] + option.split())
+
+            self.cli_set(self._base_path + [interface, 'mtu', '10000'])
+
+        # check validate() - MTU of bond higher then virtio max MTU
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+
+        for interface in self._interfaces:
+            for option in self._options.get(interface, []):
+                self.cli_set(self._base_path + [interface] + option.split())
+
+            self.cli_delete(self._base_path + [interface, 'mtu'])
+
+        self.cli_commit()
+
 if __name__ == '__main__':
     unittest.main(verbosity=2, failfast=VyOSUnitTestSHIM.TestCase.debug_on())
diff --git a/src/conf_mode/interfaces_bonding.py b/src/conf_mode/interfaces_bonding.py
index 68c2885bc..f844d0a21 100755
--- a/src/conf_mode/interfaces_bonding.py
+++ b/src/conf_mode/interfaces_bonding.py
@@ -248,6 +248,17 @@ def verify(bond):
                         continue
                     raise ConfigError(error_msg + f'it has a "{option_path.replace(".", " ")}" assigned!')
 
+            if mtu := bond.get('mtu'):
+                mtu = int(mtu)
+                max_mtu = int(EthernetIf(interface).get_max_mtu())
+                min_mtu = int(EthernetIf(interface).get_min_mtu())
+                if mtu > max_mtu:
+                    raise ConfigError('Configured MTU is greater then member '\
+                                      f'interface "{interface}" maximum of {max_mtu}!')
+                if mtu < min_mtu:
+                    raise ConfigError('Configured MTU is less then member '\
+                                      f'interface "{interface}" minimum of {min_mtu}!')
+
     if 'primary' in bond:
         if bond['primary'] not in bond['member']['interface']:
             raise ConfigError(f'Primary interface of bond "{bond_name}" must be a member interface')