sources/azure: remove unnecessary hostname bounce

Thanks to [1], the hostname is set prior to network bring-up.

The Azure data source has been bouncing the hostname during
setup(), occurring after the hostname has already been
properly configured.

Note that this doesn't prevent leaking the image's hostname
during Azure's _get_data() when it brings up ephemeral DHCP.
However, as are not guaranteed to have the hostname metadata
available from a truly "local" source, this behavior is to
be expected unless we disable `send host-name` from dhclient
config.

133ad2c

Signed-off-by: Chris Patterson <cpatterson@microsoft.com>

cloudinit/sources/DataSourceAzure.py

@@ -6,7 +6,6 @@
 
 import base64
 from collections import namedtuple
-import contextlib
 import crypt
 from functools import partial
 import os
@@ -52,20 +51,10 @@
 
 DS_NAME = 'Azure'
 DEFAULT_METADATA = {"instance-id": "iid-AZURE-NODE"}
-BOUNCE_COMMAND_IFUP = [
-    'sh', '-xc',
-    "i=$interface; x=0; ifdown $i || x=$?; ifup $i || x=$?; exit $x"
-]
-BOUNCE_COMMAND_FREEBSD = [
-    'sh', '-xc',
-    ("i=$interface; x=0; ifconfig down $i || x=$?; "
-     "ifconfig up $i || x=$?; exit $x")
-]
 
 # azure systems will always have a resource disk, and 66-azure-ephemeral.rules
 # ensures that it gets linked to this path.
 RESOURCE_DISK_PATH = '/dev/disk/cloud/azure_resource'
-DEFAULT_PRIMARY_NIC = 'eth0'
 LEASE_FILE = '/var/lib/dhcp/dhclient.eth0.leases'
 DEFAULT_FS = 'ext4'
 # DMI chassis-asset-tag is set static for all azure instances
@@ -247,7 +236,6 @@ def get_resource_disk_on_freebsd(port_id):
 
 # update the FreeBSD specific information
 if util.is_FreeBSD():
-    DEFAULT_PRIMARY_NIC = 'hn0'
     LEASE_FILE = '/var/db/dhclient.leases.hn0'
     DEFAULT_FS = 'freebsd-ufs'
     res_disk = get_resource_disk_on_freebsd(1)
@@ -261,13 +249,6 @@ def get_resource_disk_on_freebsd(port_id):
 
 BUILTIN_DS_CONFIG = {
     'data_dir': AGENT_SEED_DIR,
-    'set_hostname': True,
-    'hostname_bounce': {
-        'interface': DEFAULT_PRIMARY_NIC,
-        'policy': True,
-        'command': 'builtin',
-        'hostname_command': 'hostname',
-    },
     'disk_aliases': {'ephemeral0': RESOURCE_DISK_PATH},
     'dhclient_lease_file': LEASE_FILE,
     'apply_network_config': True,  # Use IMDS published network configuration
@@ -293,46 +274,6 @@ def get_resource_disk_on_freebsd(port_id):
 DEF_PASSWD_REDACTION = 'REDACTED'
 
 
-def get_hostname(hostname_command='hostname'):
-    if not isinstance(hostname_command, (list, tuple)):
-        hostname_command = (hostname_command,)
-    return subp.subp(hostname_command, capture=True)[0].strip()
-
-
-def set_hostname(hostname, hostname_command='hostname'):
-    subp.subp([hostname_command, hostname])
-
-
-@azure_ds_telemetry_reporter
-@contextlib.contextmanager
-def temporary_hostname(temp_hostname, cfg, hostname_command='hostname'):
-    """
-    Set a temporary hostname, restoring the previous hostname on exit.
-
-    Will have the value of the previous hostname when used as a context
-    manager, or None if the hostname was not changed.
-    """
-    policy = cfg['hostname_bounce']['policy']
-    previous_hostname = get_hostname(hostname_command)
-    if (not util.is_true(cfg.get('set_hostname')) or
-       util.is_false(policy) or
-       (previous_hostname == temp_hostname and policy != 'force')):
-        yield None
-        return
-    try:
-        set_hostname(temp_hostname, hostname_command)
-    except Exception as e:
-        report_diagnostic_event(
-            'Failed setting temporary hostname: %s' % e,
-            logger_func=LOG.warning)
-        yield None
-        return
-    try:
-        yield previous_hostname
-    finally:
-        set_hostname(previous_hostname, hostname_command)
-
-
 class DataSourceAzure(sources.DataSource):
 
     dsname = 'Azure'
@@ -369,34 +310,6 @@ def __str__(self):
         root = sources.DataSource.__str__(self)
         return "%s [seed=%s]" % (root, self.seed)
 
-    @azure_ds_telemetry_reporter
-    def bounce_network_with_azure_hostname(self):
-        # When using cloud-init to provision, we have to set the hostname from
-        # the metadata and "bounce" the network to force DDNS to update via
-        # dhclient
-        azure_hostname = self.metadata.get('local-hostname')
-        LOG.debug("Hostname in metadata is %s", azure_hostname)
-        hostname_command = self.ds_cfg['hostname_bounce']['hostname_command']
-
-        with temporary_hostname(azure_hostname, self.ds_cfg,
-                                hostname_command=hostname_command) \
-                as previous_hn:
-            if (previous_hn is not None and
-                    util.is_true(self.ds_cfg.get('set_hostname'))):
-                cfg = self.ds_cfg['hostname_bounce']
-
-                # "Bouncing" the network
-                try:
-                    return perform_hostname_bounce(hostname=azure_hostname,
-                                                   cfg=cfg,
-                                                   prev_hostname=previous_hn)
-                except Exception as e:
-                    report_diagnostic_event(
-                        "Failed publishing hostname: %s" % e,
-                        logger_func=LOG.warning)
-                    util.logexc(LOG, "handling set_hostname failed")
-        return False
-
     def _get_subplatform(self):
         """Return the subplatform metadata source details."""
         if self.seed.startswith('/dev'):
@@ -1502,9 +1415,6 @@ def _negotiate(self):
            On success, returns a dictionary including 'public_keys'.
            On failure, returns False.
         """
-
-        self.bounce_network_with_azure_hostname()
-
         pubkey_info = None
         ssh_keys_and_source = self._get_public_ssh_keys_and_source()
 
@@ -1763,42 +1673,6 @@ def address_ephemeral_resize(devpath=RESOURCE_DISK_PATH,
     return
 
 
-@azure_ds_telemetry_reporter
-def perform_hostname_bounce(hostname, cfg, prev_hostname):
-    # set the hostname to 'hostname' if it is not already set to that.
-    # then, if policy is not off, bounce the interface using command
-    # Returns True if the network was bounced, False otherwise.
-    command = cfg['command']
-    interface = cfg['interface']
-    policy = cfg['policy']
-
-    msg = ("hostname=%s policy=%s interface=%s" %
-           (hostname, policy, interface))
-    env = os.environ.copy()
-    env['interface'] = interface
-    env['hostname'] = hostname
-    env['old_hostname'] = prev_hostname
-
-    if command == "builtin":
-        if util.is_FreeBSD():
-            command = BOUNCE_COMMAND_FREEBSD
-        elif subp.which('ifup'):
-            command = BOUNCE_COMMAND_IFUP
-        else:
-            LOG.debug(
-                "Skipping network bounce: ifupdown utils aren't present.")
-            # Don't bounce as networkd handles hostname DDNS updates
-            return False
-    LOG.debug("pubhname: publishing hostname [%s]", msg)
-    shell = not isinstance(command, (list, tuple))
-    # capture=False, see comments in bug 1202758 and bug 1206164.
-    util.log_time(logfunc=LOG.debug, msg="publishing hostname",
-                  get_uptime=True, func=subp.subp,
-                  kwargs={'args': command, 'shell': shell, 'capture': False,
-                          'env': env})
-    return True
-
-
 @azure_ds_telemetry_reporter
 def write_files(datadir, files, dirmode=None):
 

doc/examples/cloud-config-datasources.txt

@@ -45,12 +45,6 @@ datasource:
       instance-id: i-87018aed
       local-hostname: myhost.internal
 
-  Azure:
-    set_hostname: True
-    hostname_bounce:
-      interface: eth0
-      policy: on # [can be 'on', 'off' or 'force']
-
   SmartOS:
     # For KVM guests:
     # Smart OS datasource works over a serial console interacting with

doc/rtd/topics/datasources/azure.rst

@@ -60,20 +60,6 @@ The settings that may be configured are:
    custom DHCP option 245 from Azure fabric.
  * **disk_aliases**: A dictionary defining which device paths should be
    interpreted as ephemeral images. See cc_disk_setup module for more info.
- * **hostname_bounce**: A dictionary Azure hostname bounce behavior to react to
-   metadata changes.  The '``hostname_bounce: command``' entry can be either
-   the literal string 'builtin' or a command to execute.  The command will be
-   invoked after the hostname is set, and will have the 'interface' in its
-   environment.  If ``set_hostname`` is not true, then ``hostname_bounce``
-   will be ignored.  An example might be:
-
-     ``command:  ["sh", "-c", "killall dhclient; dhclient $interface"]``
-
- * **hostname_bounce**: A dictionary Azure hostname bounce behavior to react to
-   metadata changes. Azure will throttle ifup/down in some cases after metadata
-   has been updated to inform dhcp server about updated hostnames.
- * **set_hostname**: Boolean set to True when we want Azure to set the hostname
-   based on metadata.
 
 Configuration for the datasource can also be read from a
 ``dscfg`` entry in the ``LinuxProvisioningConfigurationSet``.  Content in
@@ -91,12 +77,6 @@ An example configuration with the default values is provided below:
       dhclient_lease_file: /var/lib/dhcp/dhclient.eth0.leases
       disk_aliases:
         ephemeral0: /dev/disk/cloud/azure_resource
-      hostname_bounce:
-        interface: eth0
-        command: builtin
-        policy: true
-        hostname_command: hostname
-      set_hostname: true
 
 
 Userdata