Dnsmasq uses all agent IPs as nameservers

Add dhcp option which provides all agent IPs
which will be used as nameserver entries when
neutron uses multiple dhcp agent per network and
when there is no dns nameserver provided by the
neutron server.

Change-Id: I639a844bba212a731616851ff479a5e735612cf8
Closes-bug: #1259482

neutron/agent/linux/dhcp.py

@@ -16,6 +16,7 @@
 #    under the License.
 
 import abc
+import collections
 import os
 import re
 import shutil
@@ -442,6 +443,9 @@ class Dnsmasq(DhcpLocalProcess):
             subnet_to_interface_ip = self._make_subnet_interface_ip_map()
 
         options = []
+
+        dhcp_ips = collections.defaultdict(list)
+        subnet_idx_map = {}
         for i, subnet in enumerate(self.network.subnets):
             if not subnet.enable_dhcp:
                 continue
@@ -449,6 +453,10 @@ class Dnsmasq(DhcpLocalProcess):
                 options.append(
                     self._format_option(i, 'dns-server',
                                         ','.join(subnet.dns_nameservers)))
+            else:
+                # use the dnsmasq ip as nameservers only if there is no
+                # dns-server submitted by the server
+                subnet_idx_map[subnet.id] = i
 
             gateway = subnet.gateway_ip
             host_routes = []
@@ -486,6 +494,22 @@ class Dnsmasq(DhcpLocalProcess):
                     self._format_option(port.id, opt.opt_name, opt.opt_value)
                     for opt in port.extra_dhcp_opts)
 
+            # provides all dnsmasq ip as dns-server if there is more than
+            # one dnsmasq for a subnet and there is no dns-server submitted
+            # by the server
+            if port.device_owner == 'network:dhcp':
+                for ip in port.fixed_ips:
+                    i = subnet_idx_map.get(ip.subnet_id)
+                    if i is None:
+                        continue
+                    dhcp_ips[i].append(ip.ip_address)
+
+        for i, ips in dhcp_ips.items():
+            if len(ips) > 1:
+                options.append(self._format_option(i,
+                                                   'dns-server',
+                                                   ','.join(ips)))
+
         name = self.get_conf_file_name('opts')
         utils.replace_file(name, '\n'.join(options))
         return name

neutron/tests/unit/test_linux_dhcp.py

@@ -89,6 +89,30 @@ class FakeRouterPort:
         self.extra_dhcp_opts = []
 
 
+class FakePortMultipleAgents1:
+    id = 'rrrrrrrr-rrrr-rrrr-rrrr-rrrrrrrrrrrr'
+    admin_state_up = True
+    device_owner = 'network:dhcp'
+    fixed_ips = [FakeIPAllocation('192.168.0.5',
+                                  'dddddddd-dddd-dddd-dddd-dddddddddddd')]
+    mac_address = '00:00:0f:dd:dd:dd'
+
+    def __init__(self):
+        self.extra_dhcp_opts = []
+
+
+class FakePortMultipleAgents2:
+    id = 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa'
+    admin_state_up = True
+    device_owner = 'network:dhcp'
+    fixed_ips = [FakeIPAllocation('192.168.0.6',
+                                  'dddddddd-dddd-dddd-dddd-dddddddddddd')]
+    mac_address = '00:00:0f:ee:ee:ee'
+
+    def __init__(self):
+        self.extra_dhcp_opts = []
+
+
 class FakeV4HostRoute:
     destination = '20.0.0.1/24'
     nexthop = '20.0.0.1'
@@ -124,6 +148,42 @@ class FakeV4SubnetGatewayRoute:
     dns_nameservers = ['8.8.8.8']
 
 
+class FakeV4SubnetMultipleAgentsWithoutDnsProvided:
+    id = 'dddddddd-dddd-dddd-dddd-dddddddddddd'
+    ip_version = 4
+    cidr = '192.168.0.0/24'
+    gateway_ip = '192.168.0.1'
+    enable_dhcp = True
+    dns_nameservers = []
+    host_routes = []
+
+
+class FakeV4MultipleAgentsWithoutDnsProvided:
+    id = 'ffffffff-ffff-ffff-ffff-ffffffffffff'
+    subnets = [FakeV4SubnetMultipleAgentsWithoutDnsProvided()]
+    ports = [FakePort1(), FakePort2(), FakePort3(), FakeRouterPort(),
+             FakePortMultipleAgents1(), FakePortMultipleAgents2()]
+    namespace = 'qdhcp-ns'
+
+
+class FakeV4SubnetMultipleAgentsWithDnsProvided:
+    id = 'dddddddd-dddd-dddd-dddd-dddddddddddd'
+    ip_version = 4
+    cidr = '192.168.0.0/24'
+    gateway_ip = '192.168.0.1'
+    enable_dhcp = True
+    dns_nameservers = ['8.8.8.8']
+    host_routes = []
+
+
+class FakeV4MultipleAgentsWithDnsProvided:
+    id = 'ffffffff-ffff-ffff-ffff-ffffffffffff'
+    subnets = [FakeV4SubnetMultipleAgentsWithDnsProvided()]
+    ports = [FakePort1(), FakePort2(), FakePort3(), FakeRouterPort(),
+             FakePortMultipleAgents1(), FakePortMultipleAgents2()]
+    namespace = 'qdhcp-ns'
+
+
 class FakeV6Subnet:
     id = 'ffffffff-ffff-ffff-ffff-ffffffffffff'
     ip_version = 6
@@ -716,6 +776,30 @@ tag:tag1,249,%s,%s""".lstrip() % (fake_v6,
 
         self.safe.assert_called_once_with('/foo/opts', expected)
 
+    def test_output_opts_file_multiple_agents_without_dns_provided(self):
+        expected = """
+tag:tag0,option:router,192.168.0.1
+tag:tag0,option:dns-server,192.168.0.5,192.168.0.6""".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,
+                              FakeV4MultipleAgentsWithoutDnsProvided(),
+                              version=float(2.59))
+            dm._output_opts_file()
+        self.safe.assert_called_once_with('/foo/opts', expected)
+
+    def test_output_opts_file_multiple_agents_with_dns_provided(self):
+        expected = """
+tag:tag0,option:dns-server,8.8.8.8
+tag:tag0,option:router,192.168.0.1""".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,
+                              FakeV4MultipleAgentsWithDnsProvided(),
+                              version=float(2.59))
+            dm._output_opts_file()
+        self.safe.assert_called_once_with('/foo/opts', expected)
+
     def test_output_opts_file_single_dhcp(self):
         expected = """
 tag:tag0,option:dns-server,8.8.8.8