Get Azure endpoint server from DHCP client

It is more efficient and cross-distribution safe to use the hooks function
from dhclient to obtain the Azure endpoint server (DHCP option 245).

This is done by providing shell scritps that are called by the hooks
infrastructure of both dhclient and NetworkManager.  The hooks then
invoke 'cloud-init dhclient-hook' that maintains json data
with the dhclient options in
/run/cloud-init/dhclient.hooks/<interface>.json .

The azure helper then pulls the value from
/run/cloud-init/dhclient.hooks/<interface>.json file(s). If that file does
not exist or the value is not present, it will then fall back to the
original method of scraping the dhcp client lease file.

1 files changed, 87 insertions, 12 deletions

diff --git a/cloudinit/sources/helpers/azure.py b/cloudinit/sources/helpers/azure.py
index 63ccf10e..6e43440f 100644
--- a/cloudinit/sources/helpers/azure.py
+++ b/cloudinit/sources/helpers/azure.py
@@ -1,3 +1,4 @@
+import json
 import logging
 import os
 import re
@@ -6,6 +7,7 @@ import struct
 import tempfile
 import time
 
+from cloudinit import stages
 from contextlib import contextmanager
 from xml.etree import ElementTree
 
@@ -187,19 +189,32 @@ class WALinuxAgentShim(object):
         '  </Container>',
         '</Health>'])
 
-    def __init__(self):
+    def __init__(self, fallback_lease_file=None):
         LOG.debug('WALinuxAgentShim instantiated...')
-        self.endpoint = self.find_endpoint()
+        self.dhcpoptions = None
+        self._endpoint = None
         self.openssl_manager = None
         self.values = {}
+        self.lease_file = fallback_lease_file
 
     def clean_up(self):
         if self.openssl_manager is not None:
             self.openssl_manager.clean_up()
 
     @staticmethod
-    def get_ip_from_lease_value(lease_value):
-        unescaped_value = lease_value.replace('\\', '')
+    def _get_hooks_dir():
+        _paths = stages.Init()
+        return os.path.join(_paths.paths.get_runpath(), "dhclient.hooks")
+
+    @property
+    def endpoint(self):
+        if self._endpoint is None:
+            self._endpoint = self.find_endpoint(self.lease_file)
+        return self._endpoint
+
+    @staticmethod
+    def get_ip_from_lease_value(fallback_lease_value):
+        unescaped_value = fallback_lease_value.replace('\\', '')
         if len(unescaped_value) > 4:
             hex_string = ''
             for hex_pair in unescaped_value.split(':'):
@@ -213,15 +228,75 @@ class WALinuxAgentShim(object):
         return socket.inet_ntoa(packed_bytes)
 
     @staticmethod
-    def find_endpoint():
-        LOG.debug('Finding Azure endpoint...')
-        content = util.load_file('/var/lib/dhcp/dhclient.eth0.leases')
-        value = None
+    def _get_value_from_leases_file(fallback_lease_file):
+        leases = []
+        content = util.load_file(fallback_lease_file)
+        LOG.debug("content is {}".format(content))
         for line in content.splitlines():
             if 'unknown-245' in line:
-                value = line.strip(' ').split(' ', 2)[-1].strip(';\n"')
+                # Example line from Ubuntu
+                # option unknown-245 a8:3f:81:10;
+                leases.append(line.strip(' ').split(' ', 2)[-1].strip(';\n"'))
+        # Return the "most recent" one in the list
+        if len(leases) < 1:
+            return None
+        else:
+            return leases[-1]
+
+    @staticmethod
+    def _load_dhclient_json():
+        dhcp_options = {}
+        hooks_dir = WALinuxAgentShim._get_hooks_dir()
+        if not os.path.exists(hooks_dir):
+            LOG.debug("%s not found.", hooks_dir)
+            return None
+        hook_files = [os.path.join(hooks_dir, x)
+                      for x in os.listdir(hooks_dir)]
+        for hook_file in hook_files:
+            try:
+                name = os.path.basename(hook_file).replace('.json', '')
+                dhcp_options[name] = json.loads(util.load_file((hook_file)))
+            except ValueError:
+                raise ValueError("%s is not valid JSON data", hook_file)
+        return dhcp_options
+
+    @staticmethod
+    def _get_value_from_dhcpoptions(dhcp_options):
+        if dhcp_options is None:
+            return None
+        # the MS endpoint server is given to us as DHPC option 245
+        _value = None
+        for interface in dhcp_options:
+            _value = dhcp_options[interface].get('unknown_245', None)
+            if _value is not None:
+                LOG.debug("Endpoint server found in dhclient options")
+                break
+        return _value
+
+    @staticmethod
+    def find_endpoint(fallback_lease_file=None):
+        LOG.debug('Finding Azure endpoint...')
+        value = None
+        # Option-245 stored in /run/cloud-init/dhclient.hooks/<ifc>.json
+        # a dhclient exit hook that calls cloud-init-dhclient-hook
+        dhcp_options = WALinuxAgentShim._load_dhclient_json()
+        value = WALinuxAgentShim._get_value_from_dhcpoptions(dhcp_options)
         if value is None:
-            raise ValueError('No endpoint found in DHCP config.')
+            # Fallback and check the leases file if unsuccessful
+            LOG.debug("Unable to find endpoint in dhclient logs. "
+                      " Falling back to check lease files")
+            if fallback_lease_file is None:
+                LOG.warn("No fallback lease file was specified.")
+                value = None
+            else:
+                LOG.debug("Looking for endpoint in lease file %s",
+                          fallback_lease_file)
+                value = WALinuxAgentShim._get_value_from_leases_file(
+                    fallback_lease_file)
+
+        if value is None:
+            raise ValueError('No endpoint found.')
+
         endpoint_ip_address = WALinuxAgentShim.get_ip_from_lease_value(value)
         LOG.debug('Azure endpoint found at %s', endpoint_ip_address)
         return endpoint_ip_address
@@ -271,8 +346,8 @@ class WALinuxAgentShim(object):
         LOG.info('Reported ready to Azure fabric.')
 
 
-def get_metadata_from_fabric():
-    shim = WALinuxAgentShim()
+def get_metadata_from_fabric(fallback_lease_file=None):
+    shim = WALinuxAgentShim(fallback_lease_file=fallback_lease_file)
     try:
         return shim.register_with_azure_and_fetch_data()
     finally: