kubevirt: Support default route destinations in NoCloud config

docs/release-notes.md

@@ -12,6 +12,7 @@ Minor changes:
 
 - Reuse the existing HTTP client when building PATCH, PUT, and POST requests
 - Azure: Read the admin password from OVF `UserPassword` when rendering the platform-user Ignition fragment
+- KubeVirt: Support `default` route destinations in NoCloud network config
 
 Packaging changes:
 

src/providers/kubevirt/nocloud.rs

@@ -24,6 +24,21 @@ pub fn read_config_file(path: &Path, file: &str) -> Result<Option<BufReader<File
     Ok(Some(BufReader::new(file)))
 }
 
+/// Parse a route destination in CIDR notation
+///
+/// Like cloud-init and Netplan, `default` is accepted as an alias for the
+/// default route of the gateway's address family.
+fn parse_route_destination(destination: &str, gateway: IpAddr) -> Result<IpNetwork> {
+    if destination == "default" {
+        let unspecified = match gateway {
+            IpAddr::V4(_) => "0.0.0.0/0",
+            IpAddr::V6(_) => "::/0",
+        };
+        return Ok(IpNetwork::from_str(unspecified)?);
+    }
+    Ok(IpNetwork::from_str(destination)?)
+}
+
 /// Cloud-init Network Config format wrapper
 ///
 /// This can be either v1 or v2 format
@@ -71,7 +86,7 @@ pub struct NetworkConfigV1Entry {
 /// OpenStack-compatible `network`/`netmask` alias.
 #[derive(Debug, Deserialize)]
 pub struct RouteConfigV1 {
-    /// Destination in CIDR notation (preferred)
+    /// Destination in CIDR notation (preferred), or `default`
     pub destination: Option<String>,
     /// Destination network (OpenStack alias for `destination`)
     pub network: Option<String>,
@@ -195,7 +210,7 @@ pub struct NameserversConfig {
 /// Route configuration in v2 format
 #[derive(Debug, Deserialize)]
 pub struct RouteConfigV2 {
-    /// Destination network in CIDR notation
+    /// Destination network in CIDR notation, or `default`
     pub to: String,
     /// Gateway address
     pub via: String,
@@ -351,7 +366,7 @@ impl NetworkConfigV1Entry {
 
                 // Parse destination: prefer `destination` (CIDR), fall back to `network`/`netmask`
                 let destination = if let Some(dest) = &route.destination {
-                    IpNetwork::from_str(dest)?
+                    parse_route_destination(dest, gateway)?
                 } else if let Some(network) = &route.network {
                     let network_addr = IpAddr::from_str(network)?;
                     if let Some(netmask) = &route.netmask {
@@ -455,9 +470,10 @@ impl NetworkConfigV2 {
 
             // Process explicit routes first
             for route in &config.routes {
+                let gateway = IpAddr::from_str(&route.via)?;
                 iface.routes.push(NetworkRoute {
-                    destination: IpNetwork::from_str(&route.to)?,
-                    gateway: IpAddr::from_str(&route.via)?,
+                    destination: parse_route_destination(&route.to, gateway)?,
+                    gateway,
                 });
             }
 

src/providers/kubevirt/tests.rs

@@ -398,3 +398,51 @@ fn test_no_duplicate_routes_nocloud_v2() {
     .expect("cannot parse config");
     assert_no_duplicate_routes(&config);
 }
+
+/// `default` route destinations resolve to the gateway's address family.
+fn assert_route_to_default(config: &KubeVirtCloudConfig) {
+    let interfaces = config.networks().expect("cannot get interfaces");
+    assert_eq!(interfaces.len(), 1);
+
+    let eth0 = &interfaces[0];
+    assert_eq!(eth0.routes.len(), 2, "Unexpected routes: {:?}", eth0.routes);
+    assert!(eth0
+        .routes
+        .iter()
+        .any(|r| r.gateway == IpAddr::from_str("192.168.1.1").unwrap()
+            && r.destination == IpNetwork::from_str("0.0.0.0/0").unwrap()));
+    assert!(eth0
+        .routes
+        .iter()
+        .any(|r| r.gateway == IpAddr::from_str("2001:db8::1").unwrap()
+            && r.destination == IpNetwork::from_str("::/0").unwrap()));
+
+    let kargs = config.rd_network_kargs().unwrap().unwrap();
+    let expected = [
+        "rd.route=0.0.0.0/0:192.168.1.1",
+        "rd.route=[::/0]:[2001:db8::1]",
+    ];
+    for exp in expected {
+        assert!(kargs.contains(exp), "Missing '{exp}' in: {kargs}");
+    }
+}
+
+#[test]
+fn test_route_to_default_nocloud_v1() {
+    let config = KubeVirtCloudConfig::try_new(
+        Path::new("./tests/fixtures/kubevirt/route_to_default_nocloud_v1"),
+        NetworkConfigurationFormat::NoCloud,
+    )
+    .expect("cannot parse config");
+    assert_route_to_default(&config);
+}
+
+#[test]
+fn test_route_to_default_nocloud_v2() {
+    let config = KubeVirtCloudConfig::try_new(
+        Path::new("./tests/fixtures/kubevirt/route_to_default_nocloud_v2"),
+        NetworkConfigurationFormat::NoCloud,
+    )
+    .expect("cannot parse config");
+    assert_route_to_default(&config);
+}

tests/fixtures/kubevirt/route_to_default_nocloud_v1/meta-data

@@ -0,0 +1,2 @@
+instance-id: test-route-to-default-v1
+local-hostname: test-route-to-default-v1

tests/fixtures/kubevirt/route_to_default_nocloud_v1/network-config

@@ -0,0 +1,15 @@
+version: 1
+config:
+  - type: physical
+    name: eth0
+    subnets:
+      - type: static
+        address: 192.168.1.10/24
+        routes:
+          - destination: default
+            gateway: 192.168.1.1
+      - type: static6
+        address: "2001:db8::10/64"
+        routes:
+          - destination: default
+            gateway: "2001:db8::1"

tests/fixtures/kubevirt/route_to_default_nocloud_v2/meta-data

@@ -0,0 +1,2 @@
+instance-id: test-route-to-default-v2
+local-hostname: test-route-to-default-v2

tests/fixtures/kubevirt/route_to_default_nocloud_v2/network-config

@@ -0,0 +1,11 @@
+version: 2
+ethernets:
+  eth0:
+    addresses:
+      - 192.168.1.10/24
+      - "2001:db8::10/64"
+    routes:
+      - to: default
+        via: 192.168.1.1
+      - to: default
+        via: "2001:db8::1"