feat: add support for MTU in Netdog

sources/netdog/src/net_config/devices/bond.rs

@@ -26,6 +26,7 @@ pub(crate) struct NetBondV1 {
     #[serde(rename = "monitoring")]
     pub(crate) monitoring_config: BondMonitoringConfigV1,
     pub(crate) interfaces: Vec<InterfaceName>,
+    pub(crate) mtu: Option<u32>,
 }
 
 // Single variant enum only used to direct deserialization.  If the kind is not "Bond" or "bond",

sources/netdog/src/net_config/devices/interface.rs

@@ -15,6 +15,7 @@ pub(crate) struct NetInterfaceV2 {
     pub(crate) static6: Option<StaticConfigV1>,
     #[serde(rename = "route")]
     pub(crate) routes: Option<Vec<RouteV1>>,
+    pub(crate) mtu: Option<u32>,
 }
 
 impl Validate for NetInterfaceV2 {

sources/netdog/src/net_config/devices/vlan.rs

@@ -20,6 +20,7 @@ pub(crate) struct NetVlanV1 {
     _kind: VlanKind,
     pub(crate) device: InterfaceName,
     pub(crate) id: VlanId,
+    pub(crate) mtu: Option<u32>,
 }
 
 // Single variant enum only used to direct deserialization.  If the kind is not "VLAN", "Vlan", or

sources/netdog/src/net_config/test_macros/mod.rs

@@ -18,13 +18,16 @@ pub(super) mod bonding;
 #[cfg(test)]
 pub(super) mod dhcp;
 #[cfg(test)]
+pub(super) mod mtu;
+#[cfg(test)]
 pub(super) mod static_address;
 #[cfg(test)]
 pub(super) mod vlan;
 
 pub(super) use basic::basic_tests;
 pub(super) use bonding::bonding_tests;
 pub(super) use dhcp::dhcp_tests;
+pub(super) use mtu::mtu_tests;
 pub(super) use static_address::static_address_tests;
 pub(super) use vlan::vlan_tests;
 

sources/netdog/src/net_config/test_macros/mtu.rs

@@ -0,0 +1,40 @@
+/// The mtu_tests macro contains MTU-related net config tests.  It accepts a version number,
+/// and creates a module for that version containing all applicable MTU tests.
+macro_rules! mtu_tests {
+    ($version:expr) => {
+        mod mtu {
+            use $crate::net_config::deserialize_config;
+            use $crate::net_config::test_macros::gen_boilerplate;
+
+            gen_boilerplate!($version, "mtu");
+
+            // Only test MTU for version 3 and later
+            #[test]
+            fn mtu_configuration() {
+                if VERSION < 3 {
+                    // MTU is only supported in version 3 and later
+                    return;
+                }
+
+                let config_str = render_config_template(net_config().join("net_config.toml"));
+                let net_config = deserialize_config(&config_str);
+                assert!(net_config.is_ok(), "Failed to deserialize config: {:?}", net_config.err());
+
+                let net_config = net_config.unwrap();
+
+                // Check that the config has interfaces
+                assert!(net_config.has_interfaces());
+
+                // Convert to networkd config to ensure MTU values are passed through
+                let networkd_config = net_config.as_networkd_config();
+                assert!(networkd_config.is_ok(), "Failed to create networkd config: {:?}", networkd_config.err());
+
+                // The test passes if we can successfully deserialize and create networkd config
+                // with MTU values. The actual MTU values will be written to the .network files
+                // when the networkd config is written to disk.
+            }
+        }
+    };
+}
+
+pub(crate) use mtu_tests;

sources/netdog/src/net_config/v3.rs

@@ -108,12 +108,13 @@ impl Validate for NetConfigV3 {
 #[cfg(test)]
 mod tests {
     use crate::net_config::test_macros::{
-        basic_tests, bonding_tests, dhcp_tests, static_address_tests, vlan_tests,
+        basic_tests, bonding_tests, dhcp_tests, mtu_tests, static_address_tests, vlan_tests,
     };
 
     basic_tests!(3);
     dhcp_tests!(3);
     static_address_tests!(3);
     vlan_tests!(3);
     bonding_tests!(3);
+    mtu_tests!(3);
 }

sources/netdog/src/networkd/config/network.rs

@@ -48,6 +48,8 @@ struct LinkSection {
     required: Option<bool>,
     #[systemd(entry = "RequiredFamilyForOnline")]
     required_family: Option<RequiredFamily>,
+    #[systemd(entry = "MTUBytes")]
+    mtu_bytes: Option<u32>,
 }
 
 #[derive(Debug, Default, SystemdUnitSection)]
@@ -601,6 +603,11 @@ where
         self.network.route.push(route_section)
     }
 
+    /// Set the MTU for the interface
+    pub(crate) fn with_mtu(&mut self, mtu: u32) {
+        self.network.link_mut().mtu_bytes = Some(mtu);
+    }
+
     // =^..^=   =^..^=   =^..^=   =^..^=   =^..^=   =^..^=   =^..^=   =^..^=   =^..^=   =^..^=
     // The following helper methods on the `DhcpXConfig` structs exist to conveniently parse out
     // the required information.  Since this is the only place we parse these values, and will only

sources/netdog/src/networkd/conversions.rs

@@ -33,6 +33,7 @@ impl TryFrom<(InterfaceName, NetInterfaceV1)> for NetworkDDevice {
             static4: None,
             static6: None,
             routes: None,
+            mtu: None,  // v1 doesn't support MTU
         }))
     }
 }
@@ -49,6 +50,7 @@ impl TryFrom<(InterfaceName, NetInterfaceV2)> for NetworkDDevice {
             static4: config.static4,
             static6: config.static6,
             routes: config.routes,
+            mtu: config.mtu,
         }))
     }
 }
@@ -65,6 +67,7 @@ impl TryFrom<(InterfaceId, NetInterfaceV2)> for NetworkDDevice {
             static4: config.static4,
             static6: config.static6,
             routes: config.routes,
+            mtu: config.mtu,
         }))
     }
 }
@@ -94,6 +97,7 @@ impl TryFrom<(InterfaceId, NetBondV1)> for NetworkDDevice {
             min_links: config.min_links,
             monitoring_config: config.monitoring_config,
             interfaces: config.interfaces,
+            mtu: config.mtu,
         }))
     }
 }
@@ -121,6 +125,7 @@ impl TryFrom<(InterfaceId, NetVlanV1)> for NetworkDDevice {
             routes: config.routes,
             device: config.device,
             id: config.id,
+            mtu: config.mtu,
         }))
     }
 }

sources/netdog/src/networkd/devices/bond.rs

@@ -24,6 +24,7 @@ pub(crate) struct NetworkDBond {
     pub(crate) min_links: Option<usize>,
     pub(crate) monitoring_config: BondMonitoringConfigV1,
     pub(crate) interfaces: Vec<InterfaceName>,
+    pub(crate) mtu: Option<u32>,
 }
 
 impl NetDevFileCreator for NetworkDBond {
@@ -42,6 +43,7 @@ impl NetDevFileCreator for NetworkDBond {
             min_links,
             monitoring_config,
             interfaces: _, // Used in .network files, not here
+            mtu: _, // MTU is configured in .network files, not .netdev
         } = self;
 
         let mut netdev = NetDevBuilder::new_bond(name.clone());
@@ -75,13 +77,17 @@ impl NetworkFileCreator for NetworkDBond {
             min_links: _,
             monitoring_config: _,
             interfaces,
+            mtu,
         } = self;
 
         let mut network = NetworkBuilder::new_bond(name.clone());
         network.with_dhcp(dhcp4.clone(), dhcp6.clone());
         maybe_add_some!(network, with_static_config, static4);
         maybe_add_some!(network, with_static_config, static6);
         maybe_add_some!(network, with_routes, routes);
+        if let Some(m) = mtu {
+            network.with_mtu(*m);
+        }
 
         network.with_bind_carrier(interfaces.clone());
 

sources/netdog/src/networkd/devices/interface.rs

@@ -18,6 +18,7 @@ pub(crate) struct NetworkDInterface {
     pub(crate) static4: Option<StaticConfigV1>,
     pub(crate) static6: Option<StaticConfigV1>,
     pub(crate) routes: Option<Vec<RouteV1>>,
+    pub(crate) mtu: Option<u32>,
 }
 
 impl NetworkDInterface {
@@ -32,12 +33,14 @@ impl NetworkDInterface {
             static4,
             static6,
             routes,
+            mtu,
         } = self;
         dhcp4.is_none()
             && dhcp6.is_none()
             && static4.is_none()
             && static6.is_none()
             && routes.is_none()
+            && mtu.is_none()
     }
 }
 
@@ -53,6 +56,7 @@ impl NetworkFileCreator for NetworkDInterface {
             static4,
             static6,
             routes,
+            mtu,
         } = self;
 
         // Attach VLANs to this interface if configured with a name.
@@ -77,6 +81,9 @@ impl NetworkFileCreator for NetworkDInterface {
             maybe_add_some!(network, with_static_config, static4);
             maybe_add_some!(network, with_static_config, static6);
             maybe_add_some!(network, with_routes, routes);
+            if let Some(m) = mtu {
+                network.with_mtu(*m);
+            }
             if let Some(vlans) = attached_vlans {
                 network.with_vlans(vlans.to_vec())
             }

sources/netdog/src/networkd/devices/vlan.rs

@@ -24,6 +24,7 @@ pub(crate) struct NetworkDVlan {
     // entry for this VLAN
     pub(crate) device: InterfaceName,
     pub(crate) id: VlanId,
+    pub(crate) mtu: Option<u32>,
 }
 
 impl NetDevFileCreator for NetworkDVlan {
@@ -40,6 +41,7 @@ impl NetDevFileCreator for NetworkDVlan {
             routes: _,
             device: _, // Device isn't used in .netdev files
             id,
+            mtu: _, // MTU is configured in .network files, not .netdev
         } = self;
 
         let mut netdev = NetDevBuilder::new_vlan(name.clone());
@@ -63,13 +65,17 @@ impl NetworkFileCreator for NetworkDVlan {
             routes,
             device: _, // device and id aren't used in .network files
             id: _,
+            mtu,
         } = self;
 
         let mut network = NetworkBuilder::new_vlan(name.clone());
         network.with_dhcp(dhcp4.clone(), dhcp6.clone());
         maybe_add_some!(network, with_static_config, static4);
         maybe_add_some!(network, with_static_config, static6);
         maybe_add_some!(network, with_routes, routes);
+        if let Some(m) = mtu {
+            network.with_mtu(*m);
+        }
 
         vec![network.build()]
     }

sources/netdog/src/networkd/mod.rs

@@ -56,6 +56,7 @@ impl NetworkDConfig {
                     static4: None,
                     static6: None,
                     routes: None,
+                    mtu: None,
                 }))
             }
         }

sources/netdog/test_data/net_config/mtu/net_config.toml

@@ -0,0 +1,38 @@
+version = {{version}}
+
+# Interface with jumbo frames
+[eno1]
+dhcp4 = true
+mtu = 9000
+primary = true
+
+# Interface with standard MTU
+[eno2]
+dhcp6 = true
+mtu = 1500
+
+# Bond with custom MTU
+[bond0]
+kind = "bond"
+mode = "active-backup"
+mtu = 1500
+interfaces = ["eth0", "eth1"]
+dhcp4 = true
+
+[bond0.monitoring]
+miimon-frequency-ms = 100
+miimon-updelay-ms = 200
+miimon-downdelay-ms = 200
+
+# VLAN with custom MTU
+[vlan100]
+kind = "vlan"
+device = "eno1"
+id = 100
+mtu = 1500
+dhcp4 = true
+
+# Interface without MTU specified (will use default)
+[eno3]
+dhcp4 = true
+dhcp6 = true