route: add support for MPLS routes and nexthop label stacks

Extend `RouteMessageBuilder` to support the creation of MPLS routes
and nexthops with MPLS label stacks. This enables configuration of
IP-to-MPLS, MPLS-to-MPLS, and MPLS-to-IP routes.

Signed-off-by: Renato Westphal <[email protected]>

Author: rwestphal

examples/add_route_mpls.rs

@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: MIT
+
+use std::env;
+
+use ipnetwork::IpNetwork;
+use netlink_packet_route::route::MplsLabel;
+use rtnetlink::{new_connection, Error, Handle, RouteMessageBuilder};
+
+#[tokio::main]
+async fn main() -> Result<(), ()> {
+    let args: Vec<String> = env::args().collect();
+    if args.len() != 4 {
+        usage();
+        return Ok(());
+    }
+
+    let input_label = args[1]
+        .parse::<u32>()
+        .map(|label| MplsLabel {
+            label,
+            traffic_class: 0,
+            bottom_of_stack: true,
+            ttl: 0,
+        })
+        .unwrap_or_else(|_| {
+            eprintln!("invalid MPLS input label");
+            std::process::exit(1);
+        });
+
+    let gateway: IpNetwork = args[2].parse().unwrap_or_else(|_| {
+        eprintln!("invalid gateway");
+        std::process::exit(1);
+    });
+
+    let output_label = args[3]
+        .parse::<u32>()
+        .map(|label| MplsLabel {
+            label,
+            traffic_class: 0,
+            bottom_of_stack: true,
+            ttl: 0,
+        })
+        .unwrap_or_else(|_| {
+            eprintln!("invalid MPLS output label");
+            std::process::exit(1);
+        });
+
+    let (connection, handle, _) = new_connection().unwrap();
+    tokio::spawn(connection);
+
+    if let Err(e) =
+        add_route_mpls(input_label, &gateway, output_label, handle.clone())
+            .await
+    {
+        eprintln!("{e}");
+    } else {
+        println!("Route has been added");
+    }
+    Ok(())
+}
+
+async fn add_route_mpls(
+    input_label: MplsLabel,
+    gateway: &IpNetwork,
+    output_label: MplsLabel,
+    handle: Handle,
+) -> Result<(), Error> {
+    let route = RouteMessageBuilder::<MplsLabel>::new()
+        .label(input_label)
+        .via(gateway.ip().into())
+        .output_mpls(vec![output_label])
+        .build();
+    handle.route().add(route).execute().await?;
+    Ok(())
+}
+
+fn usage() {
+    eprintln!(
+        "\
+usage:
+    cargo run --example add_route_mpls -- <input_label> <gateway> <output_label>
+
+Note that you need to run this program as root:
+
+    env CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER='sudo -E' \\
+        cargo run --example add_route_mpls -- <input_label> <gateway> \
+        <output_label>"
+    );
+}

src/route/builder.rs

@@ -7,7 +7,8 @@ use std::{
 
 use netlink_packet_route::{
     route::{
-        RouteAddress, RouteAttribute, RouteFlags, RouteHeader, RouteMessage,
+        MplsLabel, RouteAddress, RouteAttribute, RouteFlags, RouteHeader,
+        RouteLwEnCapType, RouteLwTunnelEncap, RouteMessage, RouteMplsIpTunnel,
         RouteProtocol, RouteScope, RouteType,
     },
     AddressFamily,
@@ -52,6 +53,29 @@ impl<T> RouteMessageBuilder<T> {
         self
     }
 
+    /// Sets the output MPLS encapsulation labels.
+    pub fn output_mpls(mut self, labels: Vec<MplsLabel>) -> Self {
+        if labels.is_empty() {
+            return self;
+        }
+        if self.message.header.address_family == AddressFamily::Mpls {
+            self.message
+                .attributes
+                .push(RouteAttribute::NewDestination(labels));
+        } else {
+            self.message
+                .attributes
+                .push(RouteAttribute::EncapType(RouteLwEnCapType::Mpls));
+            let encap = RouteLwTunnelEncap::Mpls(
+                RouteMplsIpTunnel::Destination(labels),
+            );
+            self.message
+                .attributes
+                .push(RouteAttribute::Encap(vec![encap]));
+        }
+        self
+    }
+
     /// Sets the route priority (metric)
     pub fn priority(mut self, priority: u32) -> Self {
         self.message
@@ -402,3 +426,44 @@ impl Default for RouteMessageBuilder<IpAddr> {
         Self::new()
     }
 }
+
+impl RouteMessageBuilder<MplsLabel> {
+    /// Create default RouteMessage with header set to:
+    ///  * route: [RouteHeader::RT_TABLE_MAIN]
+    ///  * protocol: [RouteProtocol::Static]
+    ///  * scope: [RouteScope::Universe]
+    ///  * kind: [RouteType::Unicast]
+    ///  * address_family: [AddressFamily::Mpls]
+    ///
+    /// For using this message in querying routes, these settings
+    /// are ignored unless `NETLINK_GET_STRICT_CHK` been enabled.
+    pub fn new() -> Self {
+        let mut builder = Self::new_no_address_family();
+        builder.get_mut().header.address_family = AddressFamily::Mpls;
+        builder
+    }
+
+    /// Sets the destination MPLS label.
+    pub fn label(mut self, label: MplsLabel) -> Self {
+        self.message.header.address_family = AddressFamily::Mpls;
+        self.message.header.destination_prefix_length = 20;
+        self.message
+            .attributes
+            .push(RouteAttribute::Destination(RouteAddress::Mpls(label)));
+        self
+    }
+
+    /// Sets the gateway (via) address.
+    pub fn via(mut self, addr: IpAddr) -> Self {
+        self.message
+            .attributes
+            .push(RouteAttribute::Via(addr.into()));
+        self
+    }
+}
+
+impl Default for RouteMessageBuilder<MplsLabel> {
+    fn default() -> Self {
+        Self::new()
+    }
+}