netmon: add per-interface metric field

ts_netmon/src/bsd/message.rs

@@ -245,12 +245,12 @@ impl<'a> Message<'a> {
 
         let (MessageHeader::Interface(net_table::Interface {
             index,
-            data: net_table::InterfaceData { mtu, .. },
+            data: net_table::InterfaceData { mtu, metric, .. },
             ..
         })
         | MessageHeader::Interface2(net_table::Interface2 {
             index,
-            data: net_table::InterfaceData64 { mtu, .. },
+            data: net_table::InterfaceData64 { mtu, metric, .. },
             ..
         })) = &self.header
         else {
@@ -271,6 +271,8 @@ impl<'a> Message<'a> {
             },
             name: la.name.clone(),
             up: self.header.flags().contains(Flags::UP),
+            metric_v4: metric.get() as _,
+            metric_v6: metric.get() as _,
         })
     }
 

ts_netmon/src/lib.rs

@@ -60,6 +60,20 @@ pub struct Interface {
 
     /// The interface's hardware address (if set).
     pub hardware_addr: Option<smallvec::SmallVec<[u8; 6]>>,
+
+    /// The routing metric for IPv4 addresses on this interface.
+    ///
+    /// Only some platforms have this field on an interface basis; others should set it to
+    /// zero. The metric for a route is the sum of the interface metric and the route's
+    /// intrinsic metric.
+    pub metric_v4: usize,
+
+    /// The routing metric for IPv6 addresses on this interface.
+    ///
+    /// Only some platforms have this field on an interface basis; others should set it to
+    /// zero. The metric for a route is the sum of the interface metric and the route's
+    /// intrinsic metric.
+    pub metric_v6: usize,
 }
 
 /// The unique/identifying part of a [`Route`] (excludes the metric field).
@@ -77,6 +91,10 @@ pub struct Route {
     /// gateways for a given route.
     pub gateway: smallvec::SmallVec<[IpAddr; 1]>,
     /// The metric for this route. Lower is higher-preference.
+    ///
+    /// Not all platforms (notably BSD, including macOS) have a per-route metric and instead
+    /// use the interface metric instead. The metric for a route is the sum of its interface
+    /// metric and this intrinsic metric.
     pub metric: usize,
 }
 

ts_netmon/src/linux/mod.rs

@@ -187,6 +187,8 @@ fn load_interface(link: LinkMessage) -> Option<Interface> {
         name: name?,
         mtu,
         hardware_addr,
+        metric_v4: 0,
+        metric_v6: 0,
     })
 }