Dont remove non controlled routes

network/route.go

@@ -119,7 +119,7 @@ func LinuxAddRoute(destination string, gateway string, interfaceName string) err
 	return nil
 }
 
-func LinuxRemoveRoute(destination string) error {
+func LinuxRemoveRoute(destination string, interfaceName string) error {
 	if runtime.GOOS != "linux" {
 		return nil
 	}
@@ -130,12 +130,24 @@ func LinuxRemoveRoute(destination string) error {
 		return fmt.Errorf("invalid destination address: %v", err)
 	}
 
-	// Create route to delete
+	// Create route to delete. LinkIndex and Priority are set to match the
+	// route we added exactly, so this only ever deletes the route we own -
+	// a local/native route to the same destination on a different
+	// interface (or with a different metric) must never be touched.
 	route := &netlink.Route{
-		Dst: ipNet,
+		Dst:      ipNet,
+		Priority: VPNRouteMetric,
 	}
 
-	logger.Info("Removing route to %s", destination)
+	if interfaceName != "" {
+		link, err := netlink.LinkByName(interfaceName)
+		if err != nil {
+			return fmt.Errorf("failed to get interface %s: %v", interfaceName, err)
+		}
+		route.LinkIndex = link.Attrs().Index
+	}
+
+	logger.Info("Removing route to %s via interface %s", destination, interfaceName)
 
 	// Delete the route
 	if err := netlink.RouteDel(route); err != nil {
@@ -178,9 +190,9 @@ func RemoveRouteForServerIP(serverIP string, interfaceName string) error {
 		return DarwinRemoveRoute(serverIP)
 	}
 	// else if runtime.GOOS == "windows" {
-	// 	return WindowsRemoveRoute(serverIP)
+	// 	return WindowsRemoveRoute(serverIP, interfaceName)
 	// } else if runtime.GOOS == "linux" {
-	// 	return LinuxRemoveRoute(serverIP)
+	// 	return LinuxRemoveRoute(serverIP, interfaceName)
 	// }
 	return nil
 }
@@ -263,8 +275,11 @@ func AddRoutes(remoteSubnets []string, interfaceName string) error {
 	return nil
 }
 
-// removeRoutesForRemoteSubnets removes routes for each subnet in RemoteSubnets
-func RemoveRoutes(remoteSubnets []string) error {
+// removeRoutesForRemoteSubnets removes routes for each subnet in RemoteSubnets.
+// interfaceName must match the interface the routes were added on (see
+// AddRoutes) so that only the routes we own are deleted, never an unrelated
+// local/native route to the same destination on another interface.
+func RemoveRoutes(remoteSubnets []string, interfaceName string) error {
 	if len(remoteSubnets) == 0 {
 		return nil
 	}
@@ -288,11 +303,11 @@ func RemoveRoutes(remoteSubnets []string) error {
 				logger.Error("Failed to remove Darwin route for subnet %s: %v", subnet, err)
 			}
 		case "windows":
-			if err := WindowsRemoveRoute(subnet); err != nil {
+			if err := WindowsRemoveRoute(subnet, interfaceName); err != nil {
 				logger.Error("Failed to remove Windows route for subnet %s: %v", subnet, err)
 			}
 		case "linux":
-			if err := LinuxRemoveRoute(subnet); err != nil {
+			if err := LinuxRemoveRoute(subnet, interfaceName); err != nil {
 				logger.Error("Failed to remove Linux route for subnet %s: %v", subnet, err)
 			}
 		case "android", "ios":

network/route_notwindows.go

@@ -6,6 +6,6 @@ func WindowsAddRoute(destination string, gateway string, interfaceName string) e
 	return nil
 }
 
-func WindowsRemoveRoute(destination string) error {
+func WindowsRemoveRoute(destination string, interfaceName string) error {
 	return nil
 }

network/route_windows.go

@@ -96,7 +96,7 @@ func WindowsAddRoute(destination string, gateway string, interfaceName string) e
 	return nil
 }
 
-func WindowsRemoveRoute(destination string) error {
+func WindowsRemoveRoute(destination string, interfaceName string) error {
 	// Parse destination CIDR
 	_, ipNet, err := net.ParseCIDR(destination)
 	if err != nil {
@@ -120,8 +120,25 @@ func WindowsRemoveRoute(destination string) error {
 	}
 	prefix := netip.PrefixFrom(addr, maskBits)
 
+	// Resolve the LUID of the interface we added the route on, so we only
+	// ever delete the route we own rather than any route matching the
+	// destination - a local/native route to the same destination on a
+	// different interface must never be touched.
+	var luid winipcfg.LUID
+	var haveLuid bool
+	if interfaceName != "" {
+		iface, err := net.InterfaceByName(interfaceName)
+		if err != nil {
+			return fmt.Errorf("failed to get interface %s: %v", interfaceName, err)
+		}
+		luid, err = winipcfg.LUIDFromIndex(uint32(iface.Index))
+		if err != nil {
+			return fmt.Errorf("failed to get LUID for interface %s: %v", interfaceName, err)
+		}
+		haveLuid = true
+	}
+
 	// Get all routes and find the one to delete
-	// We need to get the LUID from the existing route
 	var family winipcfg.AddressFamily
 	if addr.Is4() {
 		family = 2 // AF_INET
@@ -134,17 +151,23 @@ func WindowsRemoveRoute(destination string) error {
 		return fmt.Errorf("failed to get route table: %v", err)
 	}
 
-	// Find and delete matching route
+	// Find and delete matching route. When we know which interface we added
+	// the route on, only delete the entry on that interface with our
+	// VPNRouteMetric so we never remove an unrelated local/native route to
+	// the same destination.
 	for _, route := range routes {
 		routePrefix := route.DestinationPrefix.Prefix()
-		if routePrefix == prefix {
-			logger.Info("Removing route to %s", destination)
-			err = route.Delete()
-			if err != nil {
-				return fmt.Errorf("failed to delete route: %v", err)
-			}
-			return nil
+		if routePrefix != prefix {
+			continue
 		}
+		if haveLuid && (route.InterfaceLUID != luid || route.Metric != VPNRouteMetric) {
+			continue
+		}
+		logger.Info("Removing route to %s on interface %s", destination, interfaceName)
+		if err := route.Delete(); err != nil {
+			return fmt.Errorf("failed to delete route: %v", err)
+		}
+		return nil
 	}
 
 	return fmt.Errorf("route to %s not found", destination)

newt/handlers.go

@@ -430,7 +430,7 @@ func (n *Newt) registerHandlers(ctx context.Context) {
 		}
 
 		if n.config.UseNativeMainInterface {
-			if err := network.RemoveRoutes(data.Subnets); err != nil {
+			if err := network.RemoveRoutes(data.Subnets, n.config.NativeMainInterfaceName); err != nil {
 				logger.Warn("Failed to remove routes for subnets: %v", err)
 			}
 		}

newt/tunnel.go

@@ -24,7 +24,7 @@ func (n *Newt) updateRemoteExitNodeSubnets(subnets []string) {
 			}
 		}
 		if len(toRemove) > 0 {
-			if err := network.RemoveRoutes(toRemove); err != nil {
+			if err := network.RemoveRoutes(toRemove, n.config.NativeMainInterfaceName); err != nil {
 				logger.Warn("Failed to remove old subnet routes: %v", err)
 			}
 		}
@@ -88,7 +88,7 @@ func (n *Newt) closeWgTunnel() {
 		}
 		toRemove = append(toRemove, n.activeRemoteSubnets...)
 		if len(toRemove) > 0 {
-			if err := network.RemoveRoutes(toRemove); err != nil {
+			if err := network.RemoveRoutes(toRemove, n.config.NativeMainInterfaceName); err != nil {
 				logger.Warn("Failed to remove native main tunnel routes: %v", err)
 			}
 		}