azure: Add apply_network_config option to disable network from IMDS

Azure generates network configuration from the IMDS service and removes
any preexisting hotplug network scripts which exist in Azure cloud images.
Add a datasource configuration option which allows for writing a default
network configuration which sets up dhcp on eth0 and leave the hotplug
handling to the cloud-image scripts.

To disable network-config from Azure IMDS, add the following to
/etc/cloud/cloud.cfg.d/99-azure-no-imds-network.cfg:
datasource:
  Azure:
    apply_network_config: False

LP: #1798424

1 files changed, 9 insertions, 2 deletions

diff --git a/cloudinit/sources/DataSourceAzure.py b/cloudinit/sources/DataSourceAzure.py
index 39391d01..d0358e96 100644
--- a/cloudinit/sources/DataSourceAzure.py
+++ b/cloudinit/sources/DataSourceAzure.py
@@ -207,7 +207,9 @@ BUILTIN_DS_CONFIG = {
     },
     'disk_aliases': {'ephemeral0': RESOURCE_DISK_PATH},
     'dhclient_lease_file': LEASE_FILE,
+    'apply_network_config': True,  # Use IMDS published network configuration
 }
+# RELEASE_BLOCKER: Xenial and earlier apply_network_config default is False
 
 BUILTIN_CLOUD_CONFIG = {
     'disk_setup': {
@@ -458,7 +460,8 @@ class DataSourceAzure(sources.DataSource):
         except sources.InvalidMetaDataException as e:
             LOG.warning('Could not crawl Azure metadata: %s', e)
             return False
-        if self.distro and self.distro.name == 'ubuntu':
+        if (self.distro and self.distro.name == 'ubuntu' and
+                self.ds_cfg.get('apply_network_config')):
             maybe_remove_ubuntu_network_config_scripts()
 
         # Process crawled data and augment with various config defaults
@@ -619,7 +622,11 @@ class DataSourceAzure(sources.DataSource):
               the blacklisted devices.
         """
         if not self._network_config:
-            self._network_config = parse_network_config(self._metadata_imds)
+            if self.ds_cfg.get('apply_network_config'):
+                nc_src = self._metadata_imds
+            else:
+                nc_src = None
+            self._network_config = parse_network_config(nc_src)
         return self._network_config