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

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, RouteVia,
     },
     AddressFamily,
@@ -40,6 +41,16 @@ impl<T> RouteMessageBuilder<T> {
         }
     }
 
+    /// Sets the destination MPLS label.
+    pub fn destination_mpls(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 input interface index.
     pub fn input_interface(mut self, index: u32) -> Self {
         self.message.attributes.push(RouteAttribute::Iif(index));
@@ -52,6 +63,29 @@ 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
@@ -374,6 +408,7 @@ impl RouteMessageBuilder<IpAddr> {
                 RouteAttribute::Gateway(addr.into())
             }
             (Inet, IpAddr::V6(v6)) => RouteAttribute::Via(RouteVia::Inet6(v6)),
+            (Mpls, _) => RouteAttribute::Via(addr.into()),
             (af, _) => return Err(InvalidRouteMessage::AddressFamily(af)),
         };
         self.message.attributes.push(attr);