Make the management interface MTU configurable

The default MTU for the management interface is sometimes bigger than
allowable by the physical infrastructure.  Make the MTU configurable in
cloud-init and via config json.  For cloud-init default it to the minimum size
for IPv6 if the value is not specified in boot command.

Change-Id: Ib4d4381f6977aabbeefd2f520bb5fc26ea54ffcd
Closes-Bug: #1539786

astara_router/commands/management.py

@@ -72,6 +72,7 @@ def configure_management():
     )
     parser.add_argument('mac_address', metavar='lladdr', type=str)
     parser.add_argument('ip_address', metavar='ipaddr', type=str)
+    parser.add_argument('--mtu', metavar='mtu', type=int, default=1280)
     args = parser.parse_args()
 
     ip_addr = netaddr.IPNetwork(args.ip_address)
@@ -83,6 +84,8 @@ def configure_management():
             if not intf.is_up:
                 mgr.up(intf)
 
+            intf.mtu = args.mtu
+
             if ip_addr not in intf.addresses:
                 if ip_addr.version == 6:
                     real_ifname = mgr.generic_to_host(intf.ifname)

astara_router/drivers/ip.py

@@ -156,6 +156,15 @@ class IPManager(base.Manager):
         real_ifname = self.generic_to_host(interface.ifname)
         self.sudo('link', 'set', real_ifname, 'down')
 
+    def set_mtu(self, interface):
+        """
+        Sets the mtu on interface <interface> to mtu.
+        :param interface: the interface to set mtu
+        :type interface: astara_router.models.Interface
+        """
+        real_ifname = self.generic_to_host(interface.ifname)
+        self.sudo('link', 'set', real_ifname, 'mtu', str(interface.mtu))
+
     def update_interface(self, interface, ignore_link_local=True):
         """
         Updates a network interface, particularly its addresses
@@ -177,6 +186,9 @@ class IPManager(base.Manager):
         # in case where primary and alias are swapped.
         self._update_addresses(real_ifname, interface, old_interface)
 
+        if interface.mtu is not None and old_interface.mtu != interface.mtu:
+            self.set_mtu(interface)
+
     def _update_addresses(self, real_ifname, interface, old_interface):
         """
         Compare the state of an interface, and add/remove address that have

astara_router/models.py

@@ -37,7 +37,7 @@ class Interface(ModelBase):
     """
     """
     def __init__(self, ifname=None, addresses=[], groups=None, flags=None,
-                 lladdr=None, mtu=1500, media=None,
+                 lladdr=None, mtu=None, media=None,
                  description=None, **extra_params):
         self.ifname = ifname
         self.description = description

test/unit/drivers/test_ip.py

@@ -63,6 +63,7 @@ class IPTestCase(TestCase):
     def test_get_interfaces(self):
         iface_a = mock.Mock()
         iface_a.ifname = 'em0'
+        iface_a.mtu = 1500
 
         iface_b = mock.Mock()
         iface_b.ifname = 'em1'
@@ -79,6 +80,7 @@ class IPTestCase(TestCase):
     def test_get_interface(self):
         iface_a = mock.Mock()
         iface_a.ifname = 'em0'
+        iface_a.mtu = 1500
         iface = 'astara_router.drivers.ip._parse_interface'
         ifaces = 'astara_router.drivers.ip._parse_interfaces'
         with mock.patch(iface) as parse:
@@ -126,7 +128,9 @@ class IPTestCase(TestCase):
 
     def test_update_interfaces(self):
         iface_a = mock.Mock()
+        iface_a.mtu = 1500
         iface_b = mock.Mock()
+        iface_b.mtu = 1500
 
         attr = 'update_interface'
         with mock.patch.object(ip.IPManager, attr) as update:
@@ -162,6 +166,23 @@ class IPTestCase(TestCase):
         self.mock_execute.assert_has_calls(
             [mock.call(['/sbin/ip', 'link', 'set', 'em0', 'down'], 'sudo')])
 
+    def test_set_mtu(self):
+        iface = mock.Mock()
+        iface.ifname = 'ge0'
+        iface.mtu = 1280
+
+        attr = 'ensure_mapping'
+        with mock.patch.object(ip.IPManager, attr) as ensure:
+            mgr = ip.IPManager()
+            mgr.host_mapping = {'em0': 'ge0'}
+            mgr.generic_mapping = {'ge0': 'em0'}
+
+            mgr.set_mtu(iface)
+
+        self.mock_execute.assert_has_calls(
+            [mock.call(['/sbin/ip', 'link', 'set', 'em0', 'mtu', '1280'],
+                       'sudo')])
+
     def _update_interface_test_hlpr(self, new_iface, old_iface,
                                     ignore_link_local=True):
         mock_methods = {
@@ -185,10 +206,12 @@ class IPTestCase(TestCase):
         iface = mock.Mock()
         iface.ifname = 'ge0'
         iface.addresses = []
+        iface.mtu = 1500
 
         old_iface = mock.Mock(name='old')
         old_iface.ifname = 'ge0'
         old_iface.addresses = []
+        old_iface.mtu = 1500
 
         self._update_interface_test_hlpr(iface, old_iface)
 
@@ -196,10 +219,12 @@ class IPTestCase(TestCase):
         iface = mock.Mock()
         iface.ifname = 'ge0'
         iface.addresses = []
+        iface.mtu = 1500
 
         old_iface = mock.Mock(name='old')
         old_iface.ifname = 'ge0'
         old_iface.addresses = [netaddr.IPAddress('fe80::1')]
+        old_iface.mtu = 1500
 
         self._update_interface_test_hlpr(iface, old_iface)
         self.assertEqual(old_iface.addresses, [])
@@ -208,12 +233,14 @@ class IPTestCase(TestCase):
         iface = mock.Mock()
         iface.ifname = 'ge0'
         iface.addresses = []
+        iface.mtu = 1500
 
         link_local = netaddr.IPAddress('fe80::1')
 
         old_iface = mock.Mock(name='old')
         old_iface.ifname = 'ge0'
         old_iface.addresses = [link_local]
+        old_iface.mtu = 1500
 
         self._update_interface_test_hlpr(iface, old_iface, False)
         self.assertEqual(old_iface.addresses, [link_local])