fix(azure): Reconfigure secondary NICs by removing route to DNS via t…

…hem.

As from Bionic, systemd has associated DNS server with secondary NICs,
this causes delay in the DNS resolution from Jammy and forwards. We see
it evidently in the cloud-init logs where resolving the url takes way more
seconds.

cloudinit/sources/DataSourceAzure.py

@@ -1482,18 +1482,23 @@ def availability_zone(self):
     def _generate_network_config(self):
         """Generate network configuration according to configuration."""
         # Use IMDS network metadata, if configured.
+        fxn = add_dhcp_config_for_primary_and_secondary_nics_to_network_config
         if (
             self._metadata_imds
             and self._metadata_imds != sources.UNSET
             and self.ds_cfg.get("apply_network_config")
         ):
             try:
-                return generate_network_config_from_instance_network_metadata(
-                    self._metadata_imds["network"],
-                    apply_network_config_for_secondary_ips=self.ds_cfg.get(
-                        "apply_network_config_for_secondary_ips"
-                    ),
+                netcfg = (
+                    generate_network_config_from_instance_network_metadata(
+                        self._metadata_imds["network"],
+                        apply_network_config_for_secondary_ips=self.ds_cfg.get(
+                            "apply_network_config_for_secondary_ips"
+                        ),
+                    )
                 )
+                net_cfg = fxn(netcfg)
+                return net_cfg
             except Exception as e:
                 LOG.error(
                     "Failed generating network config "
@@ -1945,6 +1950,30 @@ def load_azure_ds_dir(source_dir):
     return (md, ud, cfg, {"ovf-env.xml": contents})
 
 
+def add_dhcp_config_for_primary_and_secondary_nics_to_network_config(
+    netconfig: dict,
+) -> dict:
+    """
+    Configure the ephemeral and hotplug details.
+    parameters:
+        netconfig: dict, Network config details with other ethernet devices.
+
+    returns the updated network configuration
+    """
+    netconfig["ethernets"]["primary"] = {
+        "dhcp4": True,
+        "match": {"driver": "hv_netvsc", "name": "eth0"},
+    }
+    netconfig["ethernets"]["secondary"] = {
+        "dhcp4": True,
+        "dhcp4-overrides": {"use-dns": False},
+        "optional": True,
+        "match": {"driver": "hv_netvsc", "name": "!eth0"},
+    }
+
+    return netconfig
+
+
 @azure_ds_telemetry_reporter
 def generate_network_config_from_instance_network_metadata(
     network_metadata: dict,

tests/integration_tests/datasources/test_azure.py

@@ -1,11 +1,15 @@
+import datetime
+
 import pytest
+import yaml
+from pycloudlib.azure.util import AzureCreateParams, AzureParams
 from pycloudlib.cloud import ImageType
 
 from tests.integration_tests.clouds import IntegrationCloud
 from tests.integration_tests.conftest import get_validated_source
 from tests.integration_tests.instances import IntegrationInstance
 from tests.integration_tests.integration_settings import PLATFORM
-from tests.integration_tests.releases import CURRENT_RELEASE
+from tests.integration_tests.releases import BIONIC, CURRENT_RELEASE
 
 
 def _check_for_eject_errors(
@@ -45,3 +49,42 @@ def test_azure_eject(session_cloud: IntegrationCloud):
                 session_cloud.cloud_instance.delete_image(snapshot_id)
         else:
             _check_for_eject_errors(instance)
+
+
+@pytest.mark.skipif(PLATFORM != "azure", reason="Test is Azure specific")
+@pytest.mark.skipif(
+    CURRENT_RELEASE < BIONIC, reason="Easier to test on Bionic+"
+)
+def test_azure_multi_nic_setup(
+    setup_image, session_cloud: IntegrationCloud
+) -> None:
+    """Integration test for https://warthogs.atlassian.net/browse/CPC-3999.
+
+    Azure should have the primary NIC only route to DNS.
+    Ensure other NICs do not have route to DNS.
+    """
+    us = datetime.datetime.now().strftime("%f")
+    rg_params = AzureParams(f"ci-test-multi-nic-setup-{us}", None)
+    nic_one = AzureCreateParams(f"ci-nic1-test-{us}", rg_params.name, None)
+    nic_two = AzureCreateParams(f"ci-nic2-test-{us}", rg_params.name, None)
+    with session_cloud.launch(
+        launch_kwargs={
+            "resource_group_params": rg_params,
+            "network_interfaces_params": [nic_one, nic_two],
+        }
+    ) as snapshot_instance:
+        _check_for_eject_errors(snapshot_instance)
+        if CURRENT_RELEASE.series == "bionic":
+            ret = snapshot_instance.execute("systemd-resolve --status")
+            assert ret.ok, ret.stderr
+            assert ret.stdout.count("Current Scopes: DNS") == 1
+        else:
+            ret = snapshot_instance.execute("resolvectl dns")
+            assert ret.ok, ret.stderr
+            routes = yaml.safe_load(ret.stdout)
+            routes_devices = list(routes.keys())
+            eth1_dev = [dev for dev in routes_devices if "(eth1)" in dev][0]
+            assert routes[eth1_dev] is None
+            # check the instance can resolve something
+            res = snapshot_instance.execute("resolvectl query google.com")
+            assert res.ok, res.stderr

tests/unittests/sources/test_azure.py

@@ -976,7 +976,17 @@ def test_single_ipv4_nic_configuration(
                     "dhcp6": False,
                     "match": {"macaddress": "00:0d:3a:04:75:98"},
                     "set-name": "eth0",
-                }
+                },
+                "primary": {
+                    "dhcp4": True,
+                    "match": {"driver": "hv_netvsc", "name": "eth0"},
+                },
+                "secondary": {
+                    "dhcp4": True,
+                    "dhcp4-overrides": {"use-dns": False},
+                    "optional": True,
+                    "match": {"driver": "hv_netvsc", "name": "!eth0"},
+                },
             },
             "version": 2,
         }
@@ -1557,7 +1567,17 @@ def test_network_config_set_from_imds(self):
                     "dhcp6": False,
                     "dhcp4": True,
                     "dhcp4-overrides": {"route-metric": 100},
-                }
+                },
+                "primary": {
+                    "dhcp4": True,
+                    "match": {"driver": "hv_netvsc", "name": "eth0"},
+                },
+                "secondary": {
+                    "dhcp4": True,
+                    "dhcp4-overrides": {"use-dns": False},
+                    "optional": True,
+                    "match": {"driver": "hv_netvsc", "name": "!eth0"},
+                },
             },
             "version": 2,
         }
@@ -1595,6 +1615,16 @@ def test_network_config_set_from_imds_route_metric_for_secondary_nic(self):
                     "dhcp4": True,
                     "dhcp4-overrides": {"route-metric": 300},
                 },
+                "primary": {
+                    "dhcp4": True,
+                    "match": {"driver": "hv_netvsc", "name": "eth0"},
+                },
+                "secondary": {
+                    "dhcp4": True,
+                    "dhcp4-overrides": {"use-dns": False},
+                    "optional": True,
+                    "match": {"driver": "hv_netvsc", "name": "!eth0"},
+                },
             },
             "version": 2,
         }
@@ -1626,7 +1656,17 @@ def test_network_config_set_from_imds_for_secondary_nic_no_ip(self):
                     "dhcp6": False,
                     "dhcp4": True,
                     "dhcp4-overrides": {"route-metric": 100},
-                }
+                },
+                "primary": {
+                    "dhcp4": True,
+                    "match": {"driver": "hv_netvsc", "name": "eth0"},
+                },
+                "secondary": {
+                    "dhcp4": True,
+                    "dhcp4-overrides": {"use-dns": False},
+                    "optional": True,
+                    "match": {"driver": "hv_netvsc", "name": "!eth0"},
+                },
             },
             "version": 2,
         }