azure: support matching dhcp route-metrics for dual-stack ipv4 ipv6

Network v2 configuration for Azure will set both dhcp4 and
dhcp6 to False by default.

When IPv6 privateIpAddresses are present for an interface in Azure's
Instance Metadata Service (IMDS), set dhcp6: True and provide a
route-metric value that will match the corresponding dhcp4 route-metric.
The route-metric value will increase by 100 for each additional
interface present to ensure the primary interface has a route to IMDS.

Also fix dhcp route-metric rendering for eni and sysconfig distros.

LP: #1850308

1 files changed, 7 insertions, 3 deletions

diff --git a/cloudinit/sources/DataSourceAzure.py b/cloudinit/sources/DataSourceAzure.py
index cdf49d36..44cca210 100755
--- a/cloudinit/sources/DataSourceAzure.py
+++ b/cloudinit/sources/DataSourceAzure.py
@@ -1322,7 +1322,8 @@ def parse_network_config(imds_metadata):
             network_metadata = imds_metadata['network']
             for idx, intf in enumerate(network_metadata['interface']):
                 nicname = 'eth{idx}'.format(idx=idx)
-                dev_config = {}
+                dev_config = {'dhcp4': False, 'dhcp6': False}
+                dhcp_override = {'route-metric': (idx + 1) * 100}
                 for addr4 in intf['ipv4']['ipAddress']:
                     privateIpv4 = addr4['privateIpAddress']
                     if privateIpv4:
@@ -1340,12 +1341,15 @@ def parse_network_config(imds_metadata):
                             # non-primary interfaces should have a higher
                             # route-metric (cost) so default routes prefer
                             # primary nic due to lower route-metric value
-                            dev_config['dhcp4-overrides'] = {
-                                'route-metric': (idx + 1) * 100}
+                            dev_config['dhcp4-overrides'] = dhcp_override
                 for addr6 in intf['ipv6']['ipAddress']:
                     privateIpv6 = addr6['privateIpAddress']
                     if privateIpv6:
                         dev_config['dhcp6'] = True
+                        # non-primary interfaces should have a higher
+                        # route-metric (cost) so default routes prefer
+                        # primary nic due to lower route-metric value
+                        dev_config['dhcp6-overrides'] = dhcp_override
                         break
                 if dev_config:
                     mac = ':'.join(re.findall(r'..', intf['macAddress']))