openstack: Allow discovery in init-local using dhclient in a sandbox.

Network has not yet been configured in the init-local stage so the
openstack datasource will use dhcp-client to temporarily obtain an ipv4
address and query the metadata service at http://169.254.169.254 to get
network_data.json configuration. If present, the datasource will return
network_config version 1 config based on that network_data.json content.
Previously OpenStack datasource only setup dhcp on the fallback interface
so this represents a change in behavior to react to the full config
provided by openstack.

Also significant to OpenStack is the separation of a _crawl_data operation
from get_data(). crawl_data walks the available metadata services and
returns a dict of discovered content. get_data consumes the crawled_data,
 caches it in the datasource and reacts to that data.
/run/cloud-init/instance-data.json now published network_data.json or
ec2_metadata key if that data is present on any datasource.

The main reasons for the separation of crawl from get_data:
 * Enable performance metrics of cloud-init's metadata crawls on each
 * Enable cloud-init modules and scripts to query and consume metadata
   content which may have updated/changed after cloud-init's initial cache
   during instance boot. (Think hotplug)

Also generalize common logic to base DataSource class/module:
 * Move to a common UNSET variable up into base datasource module fix EC2,
   ConfigDrive, OpenStack, SmartOS to use the global.
 * Drop get_url_settings from Ec2, CloudStack and OpenStack and generalize
   DataSource.get_url_params(). Allow subclasses to override url_max_wait,
   url_timeout and url_retries params.
 * Rename get_network_metadata bool to perform_dhcp_setup as it designates
   whether EphemeralDHCPv4 setup is required before crawling metadata.

LP: #1749717

1 files changed, 2 insertions, 2 deletions

diff --git a/cloudinit/sources/DataSourceConfigDrive.py b/cloudinit/sources/DataSourceConfigDrive.py
index 121cf215..4cb28977 100644
--- a/cloudinit/sources/DataSourceConfigDrive.py
+++ b/cloudinit/sources/DataSourceConfigDrive.py
@@ -43,7 +43,7 @@ class DataSourceConfigDrive(openstack.SourceMixin, sources.DataSource):
         self.version = None
         self.ec2_metadata = None
         self._network_config = None
-        self.network_json = None
+        self.network_json = sources.UNSET
         self.network_eni = None
         self.known_macs = None
         self.files = {}
@@ -149,7 +149,7 @@ class DataSourceConfigDrive(openstack.SourceMixin, sources.DataSource):
     @property
     def network_config(self):
         if self._network_config is None:
-            if self.network_json is not None:
+            if self.network_json not in (None, sources.UNSET):
                 LOG.debug("network config provided via network_json")
                 self._network_config = openstack.convert_net_json(
                     self.network_json, known_macs=self.known_macs)