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

3 files changed, 23 insertions, 10 deletions

diff --git a/cloudinit/net/network_state.py b/cloudinit/net/network_state.py
index ba85c69e..20b7716b 100644
--- a/cloudinit/net/network_state.py
+++ b/cloudinit/net/network_state.py
@@ -22,8 +22,9 @@ NETWORK_STATE_REQUIRED_KEYS = {
     1: ['version', 'config', 'network_state'],
 }
 NETWORK_V2_KEY_FILTER = [
-    'addresses', 'dhcp4', 'dhcp6', 'gateway4', 'gateway6', 'interfaces',
-    'match', 'mtu', 'nameservers', 'renderer', 'set-name', 'wakeonlan'
+    'addresses', 'dhcp4', 'dhcp4-overrides', 'dhcp6', 'dhcp6-overrides',
+    'gateway4', 'gateway6', 'interfaces', 'match', 'mtu', 'nameservers',
+    'renderer', 'set-name', 'wakeonlan'
 ]
 
 NET_CONFIG_TO_V2 = {
@@ -747,12 +748,20 @@ class NetworkStateInterpreter(object):
     def _v2_to_v1_ipcfg(self, cfg):
         """Common ipconfig extraction from v2 to v1 subnets array."""
 
+        def _add_dhcp_overrides(overrides, subnet):
+            if 'route-metric' in overrides:
+                subnet['metric'] = overrides['route-metric']
+
         subnets = []
         if cfg.get('dhcp4'):
-            subnets.append({'type': 'dhcp4'})
+            subnet = {'type': 'dhcp4'}
+            _add_dhcp_overrides(cfg.get('dhcp4-overrides', {}), subnet)
+            subnets.append(subnet)
         if cfg.get('dhcp6'):
+            subnet = {'type': 'dhcp6'}
             self.use_ipv6 = True
-            subnets.append({'type': 'dhcp6'})
+            _add_dhcp_overrides(cfg.get('dhcp6-overrides', {}), subnet)
+            subnets.append(subnet)
 
         gateway4 = None
         gateway6 = None
diff --git a/cloudinit/net/sysconfig.py b/cloudinit/net/sysconfig.py
index 6717d924..fe0c67ca 100644
--- a/cloudinit/net/sysconfig.py
+++ b/cloudinit/net/sysconfig.py
@@ -395,6 +395,9 @@ class Renderer(renderer.Renderer):
         ipv6_index = -1
         for i, subnet in enumerate(subnets, start=len(iface_cfg.children)):
             subnet_type = subnet.get('type')
+            # metric may apply to both dhcp and static config
+            if 'metric' in subnet:
+                iface_cfg['METRIC'] = subnet['metric']
             if subnet_type in ['dhcp', 'dhcp4', 'dhcp6']:
                 if has_default_route and iface_cfg['BOOTPROTO'] != 'none':
                     iface_cfg['DHCLIENT_SET_DEFAULT_ROUTE'] = False
@@ -426,9 +429,6 @@ class Renderer(renderer.Renderer):
                     else:
                         iface_cfg['GATEWAY'] = subnet['gateway']
 
-                if 'metric' in subnet:
-                    iface_cfg['METRIC'] = subnet['metric']
-
                 if 'dns_search' in subnet:
                     iface_cfg['DOMAIN'] = ' '.join(subnet['dns_search'])
 
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']))