Support reading DNS settings from NetworkManager on Linux

platformsettings.py

@@ -477,9 +477,14 @@ class _LinuxPlatformSettings(_PosixPlatformSettings):
   """
   RESOLV_CONF = '/etc/resolv.conf'
   ROUTE_RE = re.compile('initcwnd (\d+)')
+  NM_DNS_RE = re.compile('IP4.DNS\[\d+\]:(\d+.\d+.\d+.\d+)')
   TCP_BASE_MSS = 'net.ipv4.tcp_base_mss'
   TCP_MTU_PROBING = 'net.ipv4.tcp_mtu_probing'
 
+  def __init__(self):
+    super(_LinuxPlatformSettings, self).__init__()
+    self._nmcli_executable = FindExecutable('nmcli')
+
   def _get_default_route_line(self):
     stdout = self._check_output('ip', 'route')
     for line in stdout.split('\n'):
@@ -534,7 +539,22 @@ def _write_resolve_conf(self, dns):
       raise DnsUpdateError('Could not find a suitable nameserver entry in %s' %
                            self.RESOLV_CONF)
 
+  def _use_network_manager(self):
+    if self._nmcli_executable != None:
+      stdout = self._nmcli('-t', '-f', 'state', 'nm')
+      if stdout.strip() == 'connected':
+        return True
+    return False
+
+  def _nmcli(self, *args):
+    return self._check_output(self._nmcli_executable, *args)
+
   def _get_primary_nameserver(self):
+    if self._use_network_manager():
+      stdout = self._nmcli('-t', '-f', 'IP4', 'dev', 'list')
+      m = self.NM_DNS_RE.search(stdout)
+      if m:
+        return m.group(1)
     try:
       resolv_file = open(self.RESOLV_CONF)
     except IOError:
@@ -546,6 +566,9 @@ def _get_primary_nameserver(self):
 
   def _set_primary_nameserver(self, dns):
     """Replace the first nameserver entry with the one given."""
+    if self._use_network_manager():
+      raise DnsUpdateError('Connection is managed by NetworkManager. Only --no-dns_forwarding is supported.')
+
     try:
       self._write_resolve_conf(dns)
     except OSError, e:

platformsettings_test.py

@@ -134,6 +134,11 @@
 }
 """
 
+LINUX_NM_DEV_LIST = """
+IP4.ADDRESS[1]:ip = 111.222.123.234/22, gw = 111.222.123.1
+IP4.DNS[1]:111.222.0.1
+IP4.DNS[2]:111.222.0.2
+"""
 
 class SystemProxyTest(unittest.TestCase):
 
@@ -236,6 +241,47 @@ def test_get_primary_nameserver_unexpected_dns_state_raises(self):
     self.assertRaises(platformsettings.DnsReadError,
                       self.settings._get_primary_nameserver)
 
+class LinuxSettingsNM(platformsettings._LinuxPlatformSettings):
+  def __init__(self):
+    super(LinuxSettingsNM, self).__init__()
+    self.state = None  # varies by test
+    self._nmcli_executable = "/usr/bin/nmcli" # make sure it is tested.
+
+  def _nmcli(self, *args):
+    if args[2] == 'state' and args[3] == 'nm':
+      return self.state + '\n'
+    if self.state == 'connected' and args[3] == 'dev' and args[4] == 'list':
+      return LINUX_NM_DEV_LIST
+    if self.state == 'disconnected' or self.state == 'asleep':
+      return ""
+
+class LinuxPlatformSettingsNMTest(unittest.TestCase):
+  def setUp(self):
+    self.settings = LinuxSettingsNM()
+
+  def test_get_primary_nameserver_nm(self):
+    self.settings.state = 'connected'
+    self.assertEqual('111.222.0.1', self.settings._get_primary_nameserver())
+    try:
+      self.settings.state = 'disconnected'
+      self.assertNotEqual('111.222.0.1', self.settings._get_primary_nameserver())
+    except platformsettings.DnsReadError, e:
+      pass
+    try:
+      self.settings.state = 'asleep'
+      self.assertNotEqual('111.222.0.1', self.settings._get_primary_nameserver())
+    except platformsettings.DnsReadError, e:
+      pass
+
+  def test_set_primary_nameserver_nm(self):
+    self.settings.state = 'connected'
+    with self.assertRaises(platformsettings.DnsUpdateError) as e1:
+      self.settings._set_primary_nameserver('127.0.0.1')
+    self.assertTrue('--no-dns_forwarding' in e1.exception.message)
+    self.settings.state = 'disconnected'
+    with self.assertRaises(platformsettings.DnsUpdateError) as e2:
+      self.settings._set_primary_nameserver('127.0.0.1')
+    self.assertTrue('sudo' in e2.exception.message)
 
 if __name__ == '__main__':
   unittest.main()