Azure: if user has set hostname, do not overwrite it

Due to the way the azure boot works, where we identify the hostname to the
fabric, we were inadvertently overwriting hostname that the user had set.

LP: #1375252

1 files changed, 73 insertions, 59 deletions

diff --git a/cloudinit/sources/DataSourceAzure.py b/cloudinit/sources/DataSourceAzure.py
index 6e030217..a19d9ca2 100644
--- a/cloudinit/sources/DataSourceAzure.py
+++ b/cloudinit/sources/DataSourceAzure.py
@@ -17,6 +17,7 @@
 #    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import base64
+import contextlib
 import crypt
 import fnmatch
 import os
@@ -66,6 +67,36 @@ DS_CFG_PATH = ['datasource', DS_NAME]
 DEF_EPHEMERAL_LABEL = 'Temporary Storage'
 
 
+def get_hostname(hostname_command='hostname'):
+    return util.subp(hostname_command, capture=True)[0].strip()
+
+
+def set_hostname(hostname, hostname_command='hostname'):
+    util.subp([hostname_command, hostname])
+
+
+@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
+    set_hostname(temp_hostname, hostname_command)
+    try:
+        yield previous_hostname
+    finally:
+        set_hostname(previous_hostname, hostname_command)
+
+
 class DataSourceAzureNet(sources.DataSource):
     def __init__(self, sys_cfg, distro, paths):
         sources.DataSource.__init__(self, sys_cfg, distro, paths)
@@ -154,33 +185,40 @@ class DataSourceAzureNet(sources.DataSource):
         # the directory to be protected.
         write_files(ddir, files, dirmode=0o700)
 
-        # handle the hostname 'publishing'
-        try:
-            handle_set_hostname(mycfg.get('set_hostname'),
-                                self.metadata.get('local-hostname'),
-                                mycfg['hostname_bounce'])
-        except Exception as e:
-            LOG.warn("Failed publishing hostname: %s", e)
-            util.logexc(LOG, "handling set_hostname failed")
-
-        try:
-            invoke_agent(mycfg['agent_command'])
-        except util.ProcessExecutionError:
-            # claim the datasource even if the command failed
-            util.logexc(LOG, "agent command '%s' failed.",
-                        mycfg['agent_command'])
-
-        shcfgxml = os.path.join(ddir, "SharedConfig.xml")
-        wait_for = [shcfgxml]
-
-        fp_files = []
-        for pk in self.cfg.get('_pubkeys', []):
-            bname = str(pk['fingerprint'] + ".crt")
-            fp_files += [os.path.join(ddir, bname)]
+        temp_hostname = self.metadata.get('local-hostname')
+        hostname_command = mycfg['hostname_bounce']['hostname_command']
+        with temporary_hostname(temp_hostname, mycfg,
+                                hostname_command=hostname_command) \
+                as previous_hostname:
+            if (previous_hostname is not None
+                    and util.is_true(mycfg.get('set_hostname'))):
+                cfg = mycfg['hostname_bounce']
+                try:
+                    perform_hostname_bounce(hostname=temp_hostname,
+                                            cfg=cfg,
+                                            prev_hostname=previous_hostname)
+                except Exception as e:
+                    LOG.warn("Failed publishing hostname: %s", e)
+                    util.logexc(LOG, "handling set_hostname failed")
 
-        missing = util.log_time(logfunc=LOG.debug, msg="waiting for files",
-                                func=wait_for_files,
-                                args=(wait_for + fp_files,))
+            try:
+                invoke_agent(mycfg['agent_command'])
+            except util.ProcessExecutionError:
+                # claim the datasource even if the command failed
+                util.logexc(LOG, "agent command '%s' failed.",
+                            mycfg['agent_command'])
+
+            shcfgxml = os.path.join(ddir, "SharedConfig.xml")
+            wait_for = [shcfgxml]
+
+            fp_files = []
+            for pk in self.cfg.get('_pubkeys', []):
+                bname = str(pk['fingerprint'] + ".crt")
+                fp_files += [os.path.join(ddir, bname)]
+
+            missing = util.log_time(logfunc=LOG.debug, msg="waiting for files",
+                                    func=wait_for_files,
+                                    args=(wait_for + fp_files,))
         if len(missing):
             LOG.warn("Did not find files, but going on: %s", missing)
 
@@ -299,39 +337,15 @@ def support_new_ephemeral(cfg):
     return mod_list
 
 
-def handle_set_hostname(enabled, hostname, cfg):
-    if not util.is_true(enabled):
-        return
-
-    if not hostname:
-        LOG.warn("set_hostname was true but no local-hostname")
-        return
-
-    apply_hostname_bounce(hostname=hostname, policy=cfg['policy'],
-                          interface=cfg['interface'],
-                          command=cfg['command'],
-                          hostname_command=cfg['hostname_command'])
-
-
-def apply_hostname_bounce(hostname, policy, interface, command,
-                          hostname_command="hostname"):
+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
-    prev_hostname = util.subp(hostname_command, capture=True)[0].strip()
-
-    util.subp([hostname_command, hostname])
-
-    msg = ("phostname=%s hostname=%s policy=%s interface=%s" %
-           (prev_hostname, hostname, policy, interface))
-
-    if util.is_false(policy):
-        LOG.debug("pubhname: policy false, skipping [%s]", msg)
-        return
-
-    if prev_hostname == hostname and policy != "force":
-        LOG.debug("pubhname: no change, policy != force. skipping. [%s]", msg)
-        return
+    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
@@ -344,9 +358,9 @@ def apply_hostname_bounce(hostname, policy, interface, command,
     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=util.subp,
-        kwargs={'args': command, 'shell': shell, 'capture': False,
-                'env': env})
+                  get_uptime=True, func=util.subp,
+                  kwargs={'args': command, 'shell': shell, 'capture': False,
+                          'env': env})
 
 
 def crtfile_to_pubkey(fname):