From c24fa039eb52d7c02a3f5b8ef37d663e32546ae8 Mon Sep 17 00:00:00 2001
From: Bradley Jones <jones.bradley@me.com>
Date: Thu, 12 Feb 2015 03:51:18 -0800
Subject: [PATCH] Advertise mtu over dhcp

If advertise_mtu option is set in the config then set the dnsmasq config option
to advertise the mtu

Partially Implements: blueprint mtu-selection-and-advertisement

Change-Id: I5f3d4276fe36dfd89d242e9afe2d46e9cc7a8a28
---
 neutron/agent/linux/dhcp.py           |  7 +++++++
 neutron/tests/unit/test_linux_dhcp.py | 10 ++++++++++
 2 files changed, 17 insertions(+)

diff --git a/neutron/agent/linux/dhcp.py b/neutron/agent/linux/dhcp.py
index 53752a8a3..99b42099b 100644
--- a/neutron/agent/linux/dhcp.py
+++ b/neutron/agent/linux/dhcp.py
@@ -20,6 +20,7 @@ import re
 import shutil
 
 import netaddr
+from oslo_config import cfg
 from oslo_log import log as logging
 from oslo_utils import importutils
 import six
@@ -349,6 +350,12 @@ class Dnsmasq(DhcpLocalProcess):
                                 cidr.prefixlen, lease))
                 possible_leases += cidr.size
 
+        if cfg.CONF.advertise_mtu:
+            mtu = self.network.mtu
+            # Do not advertise unknown mtu
+            if mtu > 0:
+                cmd.append('--dhcp-option-force=option:mtu,%d' % mtu)
+
         # Cap the limit because creating lots of subnets can inflate
         # this possible lease cap.
         cmd.append('--dhcp-lease-max=%d' %
diff --git a/neutron/tests/unit/test_linux_dhcp.py b/neutron/tests/unit/test_linux_dhcp.py
index e4f943b9b..2647bd8bc 100644
--- a/neutron/tests/unit/test_linux_dhcp.py
+++ b/neutron/tests/unit/test_linux_dhcp.py
@@ -860,6 +860,9 @@ class TestDnsmasq(TestBase):
                         lease_duration, seconds)])
                 possible_leases += netaddr.IPNetwork(s.cidr).size
 
+        if cfg.CONF.advertise_mtu:
+            expected.append('--dhcp-option-force=option:mtu,%s' % network.mtu)
+
         expected.append('--dhcp-lease-max=%d' % min(
             possible_leases, max_leases))
         expected.extend(extra_options)
@@ -946,6 +949,13 @@ class TestDnsmasq(TestBase):
         self._test_spawn(['--conf-file=', '--domain=openstacklocal',
                           '--dhcp-broadcast'])
 
+    def test_spawn_cfg_advertise_mtu(self):
+        cfg.CONF.set_override('advertise_mtu', True)
+        network = FakeV4Network()
+        network.mtu = 1500
+        self._test_spawn(['--conf-file=', '--domain=openstacklocal'],
+                         network)
+
     def _test_output_opts_file(self, expected, network, ipm_retval=None):
         with mock.patch.object(dhcp.Dnsmasq, 'get_conf_file_name') as conf_fn:
             conf_fn.return_value = '/foo/opts'
-- 
2.45.2