Simplify using external routers and metadata

The dhcp agent only pushes out the metadata
static route when the subnet is isolated, and it
determines that by checking if the gateway_ip is
not set. This makes it tricky to use external
routers and metadata from dhcp at the same time.

This patch changes how the dhcp agent determines
that the subnet is isolated. It now considers it
isolated if there is no Neutron router on it.
This makes it straightforward to use an external
router on a provider network and get the
metadata from the dhcp namespace.

Change-Id: I0e29a2f058564c267176dab26da00f6ef579808b
Closes-Bug: 1236783

neutron/agent/linux/dhcp.py

@@ -29,6 +29,7 @@ from oslo.config import cfg
 
 from neutron.agent.linux import ip_lib
 from neutron.agent.linux import utils
+from neutron.common import constants
 from neutron.common import exceptions
 from neutron.openstack.common import importutils
 from neutron.openstack.common import jsonutils
@@ -445,12 +446,8 @@ class Dnsmasq(DhcpLocalProcess):
                     host_routes.append("%s,%s" % (hr.destination, hr.nexthop))
 
             # Add host routes for isolated network segments
-            enable_metadata = (
-                self.conf.enable_isolated_metadata
-                and not subnet.gateway_ip
-                and subnet.ip_version == 4)
 
-            if enable_metadata:
+            if self._enable_metadata(subnet):
                 subnet_dhcp_ip = subnet_to_interface_ip[subnet.id]
                 host_routes.append(
                     '%s/32,%s' % (METADATA_DEFAULT_IP, subnet_dhcp_ip)
@@ -519,6 +516,25 @@ class Dnsmasq(DhcpLocalProcess):
 
         return ','.join((set_tag + tag, '%s' % option) + args)
 
+    def _enable_metadata(self, subnet):
+        '''Determine if the metadata route will be pushed to hosts on subnet.
+
+        If subnet has a Neutron router attached, we want the hosts to get
+        metadata from the router's proxy via their default route instead.
+        '''
+        if self.conf.enable_isolated_metadata and subnet.ip_version == 4:
+            if subnet.gateway_ip is None:
+                return True
+            else:
+                for port in self.network.ports:
+                    if port.device_owner == constants.DEVICE_OWNER_ROUTER_INTF:
+                        for alloc in port.fixed_ips:
+                            if alloc.subnet_id == subnet.id:
+                                return False
+                return True
+        else:
+            return False
+
     @classmethod
     def lease_update(cls):
         network_id = os.environ.get(cls.NEUTRON_NETWORK_ID_KEY)

neutron/tests/unit/test_linux_dhcp.py

@@ -30,8 +30,9 @@ LOG = logging.getLogger(__name__)
 
 
 class FakeIPAllocation:
-    def __init__(self, address):
+    def __init__(self, address, subnet_id=None):
         self.ip_address = address
+        self.subnet_id = subnet_id
 
 
 class DhcpOpt(object):
@@ -45,6 +46,7 @@ class DhcpOpt(object):
 class FakePort1:
     id = 'eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee'
     admin_state_up = True
+    device_owner = 'foo1'
     fixed_ips = [FakeIPAllocation('192.168.0.2')]
     mac_address = '00:00:80:aa:bb:cc'
 
@@ -55,6 +57,7 @@ class FakePort1:
 class FakePort2:
     id = 'ffffffff-ffff-ffff-ffff-ffffffffffff'
     admin_state_up = False
+    device_owner = 'foo2'
     fixed_ips = [FakeIPAllocation('fdca:3ba5:a17a:4ba3::2')]
     mac_address = '00:00:f3:aa:bb:cc'
 
@@ -65,6 +68,7 @@ class FakePort2:
 class FakePort3:
     id = '44444444-4444-4444-4444-444444444444'
     admin_state_up = True
+    device_owner = 'foo3'
     fixed_ips = [FakeIPAllocation('192.168.0.3'),
                  FakeIPAllocation('fdca:3ba5:a17a:4ba3::3')]
     mac_address = '00:00:0f:aa:bb:cc'
@@ -73,6 +77,18 @@ class FakePort3:
         self.extra_dhcp_opts = []
 
 
+class FakeRouterPort:
+    id = 'rrrrrrrr-rrrr-rrrr-rrrr-rrrrrrrrrrrr'
+    admin_state_up = True
+    device_owner = 'network:router_interface'
+    fixed_ips = [FakeIPAllocation('192.168.0.1',
+                                  'dddddddd-dddd-dddd-dddd-dddddddddddd')]
+    mac_address = '00:00:0f:rr:rr:rr'
+
+    def __init__(self):
+        self.extra_dhcp_opts = []
+
+
 class FakeV4HostRoute:
     destination = '20.0.0.1/24'
     nexthop = '20.0.0.1'
@@ -138,6 +154,16 @@ class FakeV4SubnetNoGateway:
     dns_nameservers = []
 
 
+class FakeV4SubnetNoRouter:
+    id = 'eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee'
+    ip_version = 4
+    cidr = '192.168.1.0/24'
+    gateway_ip = '192.168.1.1'
+    enable_dhcp = True
+    host_routes = []
+    dns_nameservers = []
+
+
 class FakeV4Network:
     id = 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa'
     subnets = [FakeV4Subnet()]
@@ -155,21 +181,21 @@ class FakeV6Network:
 class FakeDualNetwork:
     id = 'cccccccc-cccc-cccc-cccc-cccccccccccc'
     subnets = [FakeV4Subnet(), FakeV6Subnet()]
-    ports = [FakePort1(), FakePort2(), FakePort3()]
+    ports = [FakePort1(), FakePort2(), FakePort3(), FakeRouterPort()]
     namespace = 'qdhcp-ns'
 
 
 class FakeDualNetworkGatewayRoute:
     id = 'cccccccc-cccc-cccc-cccc-cccccccccccc'
     subnets = [FakeV4SubnetGatewayRoute(), FakeV6Subnet()]
-    ports = [FakePort1(), FakePort2(), FakePort3()]
+    ports = [FakePort1(), FakePort2(), FakePort3(), FakeRouterPort()]
     namespace = 'qdhcp-ns'
 
 
 class FakeDualNetworkSingleDHCP:
     id = 'cccccccc-cccc-cccc-cccc-cccccccccccc'
     subnets = [FakeV4Subnet(), FakeV4SubnetNoDHCP()]
-    ports = [FakePort1(), FakePort2(), FakePort3()]
+    ports = [FakePort1(), FakePort2(), FakePort3(), FakeRouterPort()]
     namespace = 'qdhcp-ns'
 
 
@@ -179,10 +205,16 @@ class FakeV4NoGatewayNetwork:
     ports = [FakePort1()]
 
 
+class FakeV4NetworkNoRouter:
+    id = 'cccccccc-cccc-cccc-cccc-cccccccccccc'
+    subnets = [FakeV4SubnetNoRouter()]
+    ports = [FakePort1()]
+
+
 class FakeDualV4Pxe3Ports:
     id = 'cccccccc-cccc-cccc-cccc-cccccccccccc'
     subnets = [FakeV4Subnet(), FakeV4SubnetNoDHCP()]
-    ports = [FakePort1(), FakePort2(), FakePort3()]
+    ports = [FakePort1(), FakePort2(), FakePort3(), FakeRouterPort()]
     namespace = 'qdhcp-ns'
 
     def __init__(self, port_detail="portsSame"):
@@ -217,7 +249,7 @@ class FakeDualV4Pxe3Ports:
 class FakeV4NetworkPxe2Ports:
     id = 'dddddddd-dddd-dddd-dddd-dddddddddddd'
     subnets = [FakeV4Subnet()]
-    ports = [FakePort1(), FakePort2()]
+    ports = [FakePort1(), FakePort2(), FakeRouterPort()]
     namespace = 'qdhcp-ns'
 
     def __init__(self, port_detail="portsSame"):
@@ -244,7 +276,7 @@ class FakeV4NetworkPxe2Ports:
 class FakeV4NetworkPxe3Ports:
     id = 'dddddddd-dddd-dddd-dddd-dddddddddddd'
     subnets = [FakeV4Subnet()]
-    ports = [FakePort1(), FakePort2(), FakePort3()]
+    ports = [FakePort1(), FakePort2(), FakePort3(), FakeRouterPort()]
     namespace = 'qdhcp-ns'
 
     def __init__(self, port_detail="portsSame"):
@@ -716,6 +748,24 @@ tag:tag0,option:router""".lstrip()
 
         self.safe.assert_called_once_with('/foo/opts', expected)
 
+    def test_output_opts_file_no_neutron_router_on_subnet(self):
+        expected = """
+tag:tag0,option:classless-static-route,169.254.169.254/32,192.168.1.2
+tag:tag0,249,169.254.169.254/32,192.168.1.2
+tag:tag0,option:router,192.168.1.1""".lstrip()
+
+        with mock.patch.object(dhcp.Dnsmasq, 'get_conf_file_name') as conf_fn:
+            conf_fn.return_value = '/foo/opts'
+            dm = dhcp.Dnsmasq(self.conf, FakeV4NetworkNoRouter(),
+                              version=float(2.59))
+            with mock.patch.object(dm, '_make_subnet_interface_ip_map') as ipm:
+                ipm.return_value = {FakeV4SubnetNoRouter.id: '192.168.1.2'}
+
+                dm._output_opts_file()
+                self.assertTrue(ipm.called)
+
+        self.safe.assert_called_once_with('/foo/opts', expected)
+
     def test_release_lease(self):
         dm = dhcp.Dnsmasq(self.conf, FakeDualNetwork(), version=float(2.59))
         dm.release_lease(mac_address=FakePort2.mac_address,
@@ -830,7 +880,9 @@ tag:44444444-4444-4444-4444-444444444444,option:bootfile-name,pxelinux3.0"""
                          '00:00:0f:aa:bb:cc,host-192-168-0-3.openstacklocal,'
                          '192.168.0.3\n'
                          '00:00:0f:aa:bb:cc,host-fdca-3ba5-a17a-4ba3--3.'
-                         'openstacklocal,fdca:3ba5:a17a:4ba3::3\n').lstrip()
+                         'openstacklocal,fdca:3ba5:a17a:4ba3::3\n'
+                         '00:00:0f:rr:rr:rr,host-192-168-0-1.openstacklocal,'
+                         '192.168.0.1\n').lstrip()
         exp_opt_name = '/dhcp/cccccccc-cccc-cccc-cccc-cccccccccccc/opts'
         exp_opt_data = "tag:tag0,option:router,192.168.0.1"
         fake_v6 = 'gdca:3ba5:a17a:4ba3::1'
@@ -877,7 +929,9 @@ tag:tag1,249,%s,%s""".lstrip() % (fake_v6,
                          '00:00:0f:aa:bb:cc,host-192-168-0-3.openstacklocal,'
                          '192.168.0.3\n'
                          '00:00:0f:aa:bb:cc,host-fdca-3ba5-a17a-4ba3--3.'
-                         'openstacklocal,fdca:3ba5:a17a:4ba3::3\n').lstrip()
+                         'openstacklocal,fdca:3ba5:a17a:4ba3::3\n'
+                         '00:00:0f:rr:rr:rr,host-192-168-0-1.openstacklocal,'
+                         '192.168.0.1\n').lstrip()
         exp_host_data.replace('\n', '')
         exp_opt_name = '/dhcp/cccccccc-cccc-cccc-cccc-cccccccccccc/opts'
         exp_opt_data = "tag:tag0,option:router,192.168.0.1"