feat(opennebula): support ETHx_METRIC for default route priority

cloudinit/sources/DataSourceOpenNebula.py

@@ -252,6 +252,9 @@ def get_routes(self, dev: str) -> List[Dict[str, str]]:
                 )
         return routes
 
+    def get_metric(self, dev: str) -> Optional[str]:
+        return self.get_field(dev, "metric")
+
     @overload
     def get_field(self, dev: str, name: str) -> Optional[str]: ...
     @overload
@@ -309,9 +312,21 @@ def gen_conf(self) -> Dict[str, Any]:
                 )
 
             # Set IPv4 default gateway
+            # When a metric is specified, emit an explicit route so the metric
+            # can be attached to it. Otherwise use the simpler gateway4 key.
             gateway = self.get_gateway(c_dev)
+            metric: Optional[str] = self.get_metric(c_dev)
             if gateway:
-                devconf["gateway4"] = gateway
+                if metric is not None:
+                    devconf.setdefault("routes", []).append(
+                        {
+                            "to": "default",
+                            "via": gateway,
+                            "metric": int(metric),
+                        }
+                    )
+                else:
+                    devconf["gateway4"] = gateway
 
             # Set IPv6 default gateway
             gateway6 = self.get_gateway6(c_dev)

doc/rtd/reference/datasources/opennebula.rst

@@ -68,6 +68,7 @@ the OpenNebula documentation.
     ETH<x>_DNS
     ETH<x>_SEARCH_DOMAIN
     ETH<x>_MTU
+    ETH<x>_METRIC
     ETH<x>_IP6
     ETH<x>_IP6_ULA
     ETH<x>_IP6_PREFIX_LENGTH
@@ -81,6 +82,12 @@ Static `network configuration`_.
 
     ETH0_ROUTES="10.0.0.0/8 via 192.168.1.1, 172.16.0.0/12 via 192.168.1.254"
 
+When ``ETH<x>_METRIC`` is set, the default gateway is expressed as an explicit
+route with that metric value rather than the simple ``gateway4`` key. This
+allows correct route priority on multi-homed VMs. For example, setting
+``ETH0_METRIC=0`` and ``ETH1_METRIC=1`` makes interface 0 the preferred
+default route.
+
 ::
 
     SET_HOSTNAME

tests/unittests/sources/test_opennebula.py

@@ -1045,6 +1045,114 @@ def test_gen_conf_no_routes_key_when_absent(self, m_get_phys_by_mac):
         conf = net.gen_conf()
         assert "routes" not in conf["ethernets"]["eth0"]
 
+    # ------------------------------------------------------------------ #
+    # ETHx_METRIC                                                          #
+    # ------------------------------------------------------------------ #
+
+    def test_get_metric_absent(self):
+        """get_metric returns None when ETHx_METRIC is not set."""
+        net = ds.OpenNebulaNetwork({}, mock.Mock())
+        assert net.get_metric("eth0") is None
+
+    def test_get_metric_set(self):
+        """get_metric returns the value string when ETHx_METRIC is set."""
+        net = ds.OpenNebulaNetwork({"ETH0_METRIC": "1"}, mock.Mock())
+        assert net.get_metric("eth0") == "1"
+
+    def test_get_metric_zero(self):
+        """get_metric returns '0' when ETHx_METRIC is explicitly zero."""
+        net = ds.OpenNebulaNetwork({"ETH0_METRIC": "0"}, mock.Mock())
+        assert net.get_metric("eth0") == "0"
+
+    @mock.patch(DS_PATH + ".get_physical_nics_by_mac")
+    def test_gen_conf_metric_replaces_gateway4(self, m_get_phys_by_mac):
+        """When metric is set, gateway is emitted as an explicit route."""
+        context = {
+            "ETH0_MAC": MACADDR,
+            "ETH0_IP": PUBLIC_IP,
+            "ETH0_GATEWAY": "10.0.0.1",
+            "ETH0_METRIC": "100",
+        }
+        m_get_phys_by_mac.return_value = {MACADDR: "eth0"}
+        net = ds.OpenNebulaNetwork(context, mock.Mock())
+        conf = net.gen_conf()
+        eth0 = conf["ethernets"]["eth0"]
+        assert "gateway4" not in eth0
+        expected_route = {"to": "default", "via": "10.0.0.1", "metric": 100}
+        assert expected_route in eth0["routes"]
+
+    @mock.patch(DS_PATH + ".get_physical_nics_by_mac")
+    def test_gen_conf_metric_zero(self, m_get_phys_by_mac):
+        """Metric value '0' is emitted as integer 0 in the route."""
+        context = {
+            "ETH0_MAC": MACADDR,
+            "ETH0_IP": PUBLIC_IP,
+            "ETH0_GATEWAY": "10.0.0.1",
+            "ETH0_METRIC": "0",
+        }
+        m_get_phys_by_mac.return_value = {MACADDR: "eth0"}
+        net = ds.OpenNebulaNetwork(context, mock.Mock())
+        conf = net.gen_conf()
+        eth0 = conf["ethernets"]["eth0"]
+        assert "gateway4" not in eth0
+        expected_route = {"to": "default", "via": "10.0.0.1", "metric": 0}
+        assert expected_route in eth0["routes"]
+
+    @mock.patch(DS_PATH + ".get_physical_nics_by_mac")
+    def test_gen_conf_no_metric_uses_gateway4(self, m_get_phys_by_mac):
+        """Without ETHx_METRIC the gateway4 key is used (no regression)."""
+        context = {
+            "ETH0_MAC": MACADDR,
+            "ETH0_IP": PUBLIC_IP,
+            "ETH0_GATEWAY": "10.0.0.1",
+        }
+        m_get_phys_by_mac.return_value = {MACADDR: "eth0"}
+        net = ds.OpenNebulaNetwork(context, mock.Mock())
+        conf = net.gen_conf()
+        eth0 = conf["ethernets"]["eth0"]
+        assert eth0["gateway4"] == "10.0.0.1"
+        assert "routes" not in eth0
+
+    @mock.patch(DS_PATH + ".get_physical_nics_by_mac")
+    def test_gen_conf_metric_without_gateway(self, m_get_phys_by_mac):
+        """Metric set but no gateway: no routes list, no gateway4 key."""
+        context = {
+            "ETH0_MAC": MACADDR,
+            "ETH0_IP": PUBLIC_IP,
+            "ETH0_METRIC": "10",
+        }
+        m_get_phys_by_mac.return_value = {MACADDR: "eth0"}
+        net = ds.OpenNebulaNetwork(context, mock.Mock())
+        conf = net.gen_conf()
+        eth0 = conf["ethernets"]["eth0"]
+        assert "gateway4" not in eth0
+        assert "routes" not in eth0
+
+    @mock.patch(DS_PATH + ".get_physical_nics_by_mac")
+    def test_gen_conf_multi_nic_different_metrics(self, m_get_phys_by_mac):
+        """Each NIC gets its own metric in its own explicit route."""
+        MAC_1 = "02:00:0a:12:01:01"
+        MAC_2 = "02:00:0a:12:01:02"
+        context = {
+            "ETH0_MAC": MAC_1,
+            "ETH0_IP": "10.0.0.5",
+            "ETH0_GATEWAY": "10.0.0.1",
+            "ETH0_METRIC": "0",
+            "ETH1_MAC": MAC_2,
+            "ETH1_IP": "185.70.43.5",
+            "ETH1_GATEWAY": "185.70.43.1",
+            "ETH1_METRIC": "1",
+        }
+        m_get_phys_by_mac.return_value = {MAC_1: "eth0", MAC_2: "eth1"}
+        net = ds.OpenNebulaNetwork(context, mock.Mock())
+        conf = net.gen_conf()
+        assert {"to": "default", "via": "10.0.0.1", "metric": 0} in (
+            conf["ethernets"]["eth0"]["routes"]
+        )
+        assert {"to": "default", "via": "185.70.43.1", "metric": 1} in (
+            conf["ethernets"]["eth1"]["routes"]
+        )
+
 
 class TestParseShellConfig:
     @pytest.mark.allow_subp_for("bash", "sh")