DVR: Look at all SNAT ports for a subnet match

For IPv6, the csnat port list could have multiple
subnets contained in it, but we were only ever
looking at the one associated with the first fixed
IP when trying to match an internal port.  Change
to check all subnets on all port combinations
(internal and csnat) before giving up.

Change-Id: I9c0ac933c08734a3f6738a233fdf6021ce9bd375
Closes-bug: #1624515

neutron/agent/l3/dvr_router_base.py

@@ -38,16 +38,17 @@ class DvrRouterBase(router.RouterInfo):
         """Return the SNAT port for the given internal interface port."""
         if snat_ports is None:
             snat_ports = self.get_snat_interfaces()
-        fixed_ip = int_port['fixed_ips'][0]
-        subnet_id = fixed_ip['subnet_id']
-        if snat_ports:
-            match_port = [p for p in snat_ports
-                          if p['fixed_ips'][0]['subnet_id'] == subnet_id]
-            if match_port:
-                return match_port[0]
-            else:
-                LOG.error(_LE('DVR: SNAT port not found in the list '
-                              '%(snat_list)s for the given router '
-                              ' internal port %(int_p)s'), {
-                                  'snat_list': snat_ports,
-                                  'int_p': int_port})
+        if not snat_ports:
+            return
+        fixed_ips = int_port['fixed_ips']
+        subnet_ids = [fixed_ip['subnet_id'] for fixed_ip in fixed_ips]
+        for p in snat_ports:
+            for ip in p['fixed_ips']:
+                if ip['subnet_id'] in subnet_ids:
+                    return p
+
+        LOG.error(_LE('DVR: SNAT port not found in the list '
+                      '%(snat_list)s for the given router '
+                      'internal port %(int_p)s'), {
+                          'snat_list': snat_ports,
+                          'int_p': int_port})

neutron/tests/common/l3_test_common.py

@@ -132,18 +132,29 @@ def get_subnet_id(port):
 
 
 def router_append_interface(router, count=1, ip_version=4, ra_mode=None,
-                            addr_mode=None, dual_stack=False):
+                            addr_mode=None, dual_stack=False, same_port=False):
     interfaces = router[lib_constants.INTERFACE_KEY]
     current = sum(
         [netaddr.IPNetwork(subnet['cidr']).version == ip_version
          for p in interfaces for subnet in p['subnets']])
 
+    # If dual_stack=True, create IPv4 and IPv6 subnets on each port
+    # If same_port=True, create ip_version number of subnets on a single port
+    # Else create just an ip_version subnet on each port
+    if dual_stack:
+        ip_versions = [4, 6]
+    elif same_port:
+        ip_versions = [ip_version] * count
+        count = 1
+    else:
+        ip_versions = [ip_version]
+
     mac_address = netaddr.EUI('ca:fe:de:ad:be:ef')
     mac_address.dialect = netaddr.mac_unix
     for i in range(current, current + count):
         fixed_ips = []
         subnets = []
-        for loop_version in (4, 6):
+        for loop_version in ip_versions:
             if loop_version == 4 and (ip_version == 4 or dual_stack):
                 ip_pool = '35.4.%i.4'
                 cidr_pool = '35.4.%i.0/24'

neutron/tests/unit/agent/l3/test_agent.py

@@ -887,6 +887,38 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
             self.assertNotEqual(test_port, res_ip)
             self.assertIsNone(res_ip)
 
+    def test_get_snat_port_for_internal_port_ipv6_same_port(self):
+        router = l3_test_common.prepare_router_data(ip_version=4,
+                                                    enable_snat=True,
+                                                    num_internal_ports=1)
+        ri = dvr_router.DvrEdgeRouter(mock.sentinel.agent,
+                                      HOSTNAME,
+                                      router['id'],
+                                      router,
+                                      **self.ri_kwargs)
+
+        # Add two additional IPv6 prefixes on the same interface
+        l3_test_common.router_append_interface(router, count=2, ip_version=6,
+                                               same_port=True)
+        internal_ports = ri.router.get(lib_constants.INTERFACE_KEY, [])
+        with mock.patch.object(ri, 'get_snat_interfaces') as get_interfaces:
+            get_interfaces.return_value = internal_ports
+            # get the second internal interface in the list
+            res_port = ri.get_snat_port_for_internal_port(internal_ports[1])
+            self.assertEqual(internal_ports[1], res_port)
+
+            # tweak the first subnet_id, should still find port based
+            # on second subnet_id
+            test_port = copy.deepcopy(res_port)
+            test_port['fixed_ips'][0]['subnet_id'] = 1234
+            res_ip = ri.get_snat_port_for_internal_port(test_port)
+            self.assertEqual(internal_ports[1], res_ip)
+
+            # tweak the second subnet_id, shouldn't match now
+            test_port['fixed_ips'][1]['subnet_id'] = 1234
+            res_ip = ri.get_snat_port_for_internal_port(test_port)
+            self.assertIsNone(res_ip)
+
     def test_process_cent_router(self):
         router = l3_test_common.prepare_router_data()
         agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)