fix(azure): disable use-dns for secondary nics

cloudinit/sources/DataSourceAzure.py

@@ -1965,6 +1965,9 @@ def generate_network_config_from_instance_network_metadata(
         # addresses.
         nicname = "eth{idx}".format(idx=idx)
         dhcp_override = {"route-metric": (idx + 1) * 100}
+        # DNS resolution through secondary NICs is not supported, disable it.
+        if idx > 0:
+            dhcp_override["use-dns"] = False
         dev_config: Dict[str, Any] = {
             "dhcp4": True,
             "dhcp4-overrides": dhcp_override,

tests/integration_tests/datasources/test_azure.py

@@ -1,11 +1,14 @@
+import datetime
+
 import pytest
+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 +48,70 @@ def test_azure_eject(session_cloud: IntegrationCloud):
                 session_cloud.cloud_instance.delete_image(snapshot_id)
         else:
             _check_for_eject_errors(instance)
+
+
+def parse_resolvectl_dns(output: str) -> dict:
+    """Parses the output of 'resolvectl dns'.
+
+    >>> parse_resolvectl_dns(
+    ...    "Global:",
+    ...    "Link 2 (eth0): 168.63.129.16",
+    ...    "Link 3 (eth1): 168.63.129.16",
+    ... )
+    {'Global': '',
+     'Link 2 (eth0)': '168.63.129.16',
+     'Link 3 (eth1)': '168.63.129.16'}
+    """
+
+    parsed = dict()
+    for line in output.splitlines():
+        if line.isspace():
+            continue
+        splitted = line.split(":")
+        k = splitted.pop(0).strip()
+        v = splitted.pop(0).strip() if splitted else ""
+        parsed[k] = v
+    return parsed
+
+
+@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 client:
+        _check_for_eject_errors(client)
+        if CURRENT_RELEASE == BIONIC:
+            ret = client.execute("systemd-resolve --status")
+            assert ret.ok, ret.stderr
+            assert ret.stdout.count("Current Scopes: DNS") == 1
+        else:
+            ret = client.execute("resolvectl dns")
+            assert ret.ok, ret.stderr
+            routes = parse_resolvectl_dns(ret.stdout)
+            routes_devices = list(routes.keys())
+            eth1_dev = [dev for dev in routes_devices if "(eth1)" in dev][0]
+            assert not routes[eth1_dev], (
+                f"Expected eth1 to not have routes to dns."
+                f" Found: {routes[eth1_dev]}"
+            )
+
+        # check the instance can resolve something
+        res = client.execute("resolvectl query google.com")
+        assert res.ok, res.stderr

tests/unittests/sources/test_azure.py

@@ -742,14 +742,20 @@ class TestGenerateNetworkConfig:
                             "match": {"macaddress": "00:0d:3a:04:75:98"},
                             "dhcp6": False,
                             "dhcp4": True,
-                            "dhcp4-overrides": {"route-metric": 200},
+                            "dhcp4-overrides": {
+                                "route-metric": 200,
+                                "use-dns": False,
+                            },
                         },
                         "eth2": {
                             "set-name": "eth2",
                             "match": {"macaddress": "00:0d:3a:04:75:98"},
                             "dhcp6": False,
                             "dhcp4": True,
-                            "dhcp4-overrides": {"route-metric": 300},
+                            "dhcp4-overrides": {
+                                "route-metric": 300,
+                                "use-dns": False,
+                            },
                         },
                     },
                     "version": 2,
@@ -976,7 +982,7 @@ def test_single_ipv4_nic_configuration(
                     "dhcp6": False,
                     "match": {"macaddress": "00:0d:3a:04:75:98"},
                     "set-name": "eth0",
-                }
+                },
             },
             "version": 2,
         }
@@ -1557,7 +1563,7 @@ def test_network_config_set_from_imds(self):
                     "dhcp6": False,
                     "dhcp4": True,
                     "dhcp4-overrides": {"route-metric": 100},
-                }
+                },
             },
             "version": 2,
         }
@@ -1586,14 +1592,14 @@ def test_network_config_set_from_imds_route_metric_for_secondary_nic(self):
                     "match": {"macaddress": "22:0d:3a:04:75:98"},
                     "dhcp6": False,
                     "dhcp4": True,
-                    "dhcp4-overrides": {"route-metric": 200},
+                    "dhcp4-overrides": {"route-metric": 200, "use-dns": False},
                 },
                 "eth2": {
                     "set-name": "eth2",
                     "match": {"macaddress": "33:0d:3a:04:75:98"},
                     "dhcp6": False,
                     "dhcp4": True,
-                    "dhcp4-overrides": {"route-metric": 300},
+                    "dhcp4-overrides": {"route-metric": 300, "use-dns": False},
                 },
             },
             "version": 2,
@@ -1626,7 +1632,7 @@ def test_network_config_set_from_imds_for_secondary_nic_no_ip(self):
                     "dhcp6": False,
                     "dhcp4": True,
                     "dhcp4-overrides": {"route-metric": 100},
-                }
+                },
             },
             "version": 2,
         }