Add route support

route_mapping.go

@@ -0,0 +1,32 @@
+package tun
+
+import (
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/cache"
+)
+
+type RouteMapping struct {
+	status *cache.LruCache[RouteSession, RouteAction]
+}
+
+func NewRouteMapping(maxAge int64) *RouteMapping {
+	return &RouteMapping{
+		status: cache.New(
+			cache.WithAge[RouteSession, RouteAction](maxAge),
+			cache.WithUpdateAgeOnGet[RouteSession, RouteAction](),
+			cache.WithEvict[RouteSession, RouteAction](func(key RouteSession, conn RouteAction) {
+				common.Close(conn)
+			}),
+		),
+	}
+}
+
+func (m *RouteMapping) Lookup(session RouteSession, constructor func() RouteAction) RouteAction {
+	action, _ := m.status.LoadOrStore(session, constructor)
+	if action.Timeout() {
+		common.Close(action)
+		action = constructor()
+		m.status.Store(session, action)
+	}
+	return action
+}