set_hostname: When present in metadata, set it before network bringup.

When instance meta-data provides hostname information, run
cc_set_hostname in the init-local or init-net stage before network
comes up.

Prevent an initial DHCP request which leaks the stock cloud-image default
hostname before the meta-data provided hostname was processed.
A leaked cloud-image hostname adversely affects Dynamic DNS which
would reallocate 'ubuntu' hostname in DNS to every instance brought up by
cloud-init. These instances would only update DNS to the cloud-init
configured hostname upon DHCP lease renewal.

This branch extends the get_hostname methods in datasource, cloud and
util to limit results to metadata_only to avoid extra cost of querying
the distro for hostname information if metadata does not provide that
information.

LP: #1746455

2 files changed, 186 insertions, 0 deletions

diff --git a/cloudinit/cmd/main.py b/cloudinit/cmd/main.py
index fcddd75c..3f2dbb93 100644
--- a/cloudinit/cmd/main.py
+++ b/cloudinit/cmd/main.py
@@ -40,6 +40,7 @@ from cloudinit.settings import (PER_INSTANCE, PER_ALWAYS, PER_ONCE,
 
 from cloudinit import atomic_helper
 
+from cloudinit.config import cc_set_hostname
 from cloudinit.dhclient_hook import LogDhclient
 
 
@@ -352,6 +353,11 @@ def main_init(name, args):
     LOG.debug("[%s] %s will now be targeting instance id: %s. new=%s",
               mode, name, iid, init.is_new_instance())
 
+    if mode == sources.DSMODE_LOCAL:
+        # Before network comes up, set any configured hostname to allow
+        # dhcp clients to advertize this hostname to any DDNS services
+        # LP: #1746455.
+        _maybe_set_hostname(init, stage='local', retry_stage='network')
     init.apply_network_config(bring_up=bool(mode != sources.DSMODE_LOCAL))
 
     if mode == sources.DSMODE_LOCAL:
@@ -368,6 +374,7 @@ def main_init(name, args):
     init.setup_datasource()
     # update fully realizes user-data (pulling in #include if necessary)
     init.update()
+    _maybe_set_hostname(init, stage='init-net', retry_stage='modules:config')
     # Stage 7
     try:
         # Attempt to consume the data per instance.
@@ -681,6 +688,24 @@ def status_wrapper(name, args, data_d=None, link_d=None):
     return len(v1[mode]['errors'])
 
 
+def _maybe_set_hostname(init, stage, retry_stage):
+    """Call set-hostname if metadata, vendordata or userdata provides it.
+
+    @param stage: String representing current stage in which we are running.
+    @param retry_stage: String represented logs upon error setting hostname.
+    """
+    cloud = init.cloudify()
+    (hostname, _fqdn) = util.get_hostname_fqdn(
+        init.cfg, cloud, metadata_only=True)
+    if hostname:  # meta-data or user-data hostname content
+        try:
+            cc_set_hostname.handle('set-hostname', init.cfg, cloud, LOG, None)
+        except cc_set_hostname.SetHostnameError as e:
+            LOG.debug(
+                'Failed setting hostname in %s stage. Will'
+                ' retry in %s stage. Error: %s.', stage, retry_stage, str(e))
+
+
 def main_features(name, args):
     sys.stdout.write('\n'.join(sorted(version.FEATURES)) + '\n')
 
diff --git a/cloudinit/cmd/tests/test_main.py b/cloudinit/cmd/tests/test_main.py
new file mode 100644
index 00000000..dbe421c0
--- /dev/null
+++ b/cloudinit/cmd/tests/test_main.py
@@ -0,0 +1,161 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+
+from collections import namedtuple
+import copy
+import os
+from six import StringIO
+
+from cloudinit.cmd import main
+from cloudinit.util import (
+    ensure_dir, load_file, write_file, yaml_dumps)
+from cloudinit.tests.helpers import (
+    FilesystemMockingTestCase, wrap_and_call)
+
+mypaths = namedtuple('MyPaths', 'run_dir')
+myargs = namedtuple('MyArgs', 'debug files force local reporter subcommand')
+
+
+class TestMain(FilesystemMockingTestCase):
+
+    with_logs = True
+
+    def setUp(self):
+        super(TestMain, self).setUp()
+        self.new_root = self.tmp_dir()
+        self.cloud_dir = self.tmp_path('var/lib/cloud/', dir=self.new_root)
+        os.makedirs(self.cloud_dir)
+        self.replicateTestRoot('simple_ubuntu', self.new_root)
+        self.cfg = {
+            'datasource_list': ['None'],
+            'runcmd': ['ls /etc'],  # test ALL_DISTROS
+            'system_info': {'paths': {'cloud_dir': self.cloud_dir,
+                                      'run_dir': self.new_root}},
+            'write_files': [
+                {
+                    'path': '/etc/blah.ini',
+                    'content': 'blah',
+                    'permissions': 0o755,
+                },
+            ],
+            'cloud_init_modules': ['write-files', 'runcmd'],
+        }
+        cloud_cfg = yaml_dumps(self.cfg)
+        ensure_dir(os.path.join(self.new_root, 'etc', 'cloud'))
+        self.cloud_cfg_file = os.path.join(
+            self.new_root, 'etc', 'cloud', 'cloud.cfg')
+        write_file(self.cloud_cfg_file, cloud_cfg)
+        self.patchOS(self.new_root)
+        self.patchUtils(self.new_root)
+        self.stderr = StringIO()
+        self.patchStdoutAndStderr(stderr=self.stderr)
+
+    def test_main_init_run_net_stops_on_file_no_net(self):
+        """When no-net file is present, main_init does not process modules."""
+        stop_file = os.path.join(self.cloud_dir, 'data', 'no-net')  # stop file
+        write_file(stop_file, '')
+        cmdargs = myargs(
+            debug=False, files=None, force=False, local=False, reporter=None,
+            subcommand='init')
+        (item1, item2) = wrap_and_call(
+            'cloudinit.cmd.main',
+            {'util.close_stdin': True,
+             'netinfo.debug_info': 'my net debug info',
+             'util.fixup_output': ('outfmt', 'errfmt')},
+            main.main_init, 'init', cmdargs)
+        # We should not run write_files module
+        self.assertFalse(
+            os.path.exists(os.path.join(self.new_root, 'etc/blah.ini')),
+            'Unexpected run of write_files module produced blah.ini')
+        self.assertEqual([], item2)
+        # Instancify is called
+        instance_id_path = 'var/lib/cloud/data/instance-id'
+        self.assertFalse(
+            os.path.exists(os.path.join(self.new_root, instance_id_path)),
+            'Unexpected call to datasource.instancify produced instance-id')
+        expected_logs = [
+            "Exiting. stop file ['{stop_file}'] existed\n".format(
+                stop_file=stop_file),
+            'my net debug info'  # netinfo.debug_info
+        ]
+        for log in expected_logs:
+            self.assertIn(log, self.stderr.getvalue())
+
+    def test_main_init_run_net_runs_modules(self):
+        """Modules like write_files are run in 'net' mode."""
+        cmdargs = myargs(
+            debug=False, files=None, force=False, local=False, reporter=None,
+            subcommand='init')
+        (item1, item2) = wrap_and_call(
+            'cloudinit.cmd.main',
+            {'util.close_stdin': True,
+             'netinfo.debug_info': 'my net debug info',
+             'util.fixup_output': ('outfmt', 'errfmt')},
+            main.main_init, 'init', cmdargs)
+        self.assertEqual([], item2)
+        # Instancify is called
+        instance_id_path = 'var/lib/cloud/data/instance-id'
+        self.assertEqual(
+            'iid-datasource-none\n',
+            os.path.join(load_file(
+                os.path.join(self.new_root, instance_id_path))))
+        # modules are run (including write_files)
+        self.assertEqual(
+            'blah', load_file(os.path.join(self.new_root, 'etc/blah.ini')))
+        expected_logs = [
+            'network config is disabled by fallback',  # apply_network_config
+            'my net debug info',  # netinfo.debug_info
+            'no previous run detected'
+        ]
+        for log in expected_logs:
+            self.assertIn(log, self.stderr.getvalue())
+
+    def test_main_init_run_net_calls_set_hostname_when_metadata_present(self):
+        """When local-hostname metadata is present, call cc_set_hostname."""
+        self.cfg['datasource'] = {
+            'None': {'metadata': {'local-hostname': 'md-hostname'}}}
+        cloud_cfg = yaml_dumps(self.cfg)
+        write_file(self.cloud_cfg_file, cloud_cfg)
+        cmdargs = myargs(
+            debug=False, files=None, force=False, local=False, reporter=None,
+            subcommand='init')
+
+        def set_hostname(name, cfg, cloud, log, args):
+            self.assertEqual('set-hostname', name)
+            updated_cfg = copy.deepcopy(self.cfg)
+            updated_cfg.update(
+                {'def_log_file': '/var/log/cloud-init.log',
+                 'log_cfgs': [],
+                 'syslog_fix_perms': ['syslog:adm', 'root:adm', 'root:wheel'],
+                 'vendor_data': {'enabled': True, 'prefix': []}})
+            updated_cfg.pop('system_info')
+
+            self.assertEqual(updated_cfg, cfg)
+            self.assertEqual(main.LOG, log)
+            self.assertIsNone(args)
+
+        (item1, item2) = wrap_and_call(
+            'cloudinit.cmd.main',
+            {'util.close_stdin': True,
+             'netinfo.debug_info': 'my net debug info',
+             'cc_set_hostname.handle': {'side_effect': set_hostname},
+             'util.fixup_output': ('outfmt', 'errfmt')},
+            main.main_init, 'init', cmdargs)
+        self.assertEqual([], item2)
+        # Instancify is called
+        instance_id_path = 'var/lib/cloud/data/instance-id'
+        self.assertEqual(
+            'iid-datasource-none\n',
+            os.path.join(load_file(
+                os.path.join(self.new_root, instance_id_path))))
+        # modules are run (including write_files)
+        self.assertEqual(
+            'blah', load_file(os.path.join(self.new_root, 'etc/blah.ini')))
+        expected_logs = [
+            'network config is disabled by fallback',  # apply_network_config
+            'my net debug info',  # netinfo.debug_info
+            'no previous run detected'
+        ]
+        for log in expected_logs:
+            self.assertIn(log, self.stderr.getvalue())
+
+# vi: ts=4 expandtab