[client] Fix Android DNS routes lost after TUN rebuild

client/internal/routemanager/notifier/notifier_android.go

@@ -31,26 +31,11 @@ func (n *Notifier) SetListener(listener listener.NetworkChangeListener) {
 	n.listener = listener
 }
 
+// SetInitialClientRoutes stores the full initial route set (including fake IP blocks)
+// and a separate comparison set (without fake IP blocks) for diff detection.
 func (n *Notifier) SetInitialClientRoutes(initialRoutes []*route.Route, routesForComparison []*route.Route) {
-	// initialRoutes contains fake IP block for interface configuration
-	filteredInitial := make([]*route.Route, 0)
-	for _, r := range initialRoutes {
-		if r.IsDynamic() {
-			continue
-		}
-		filteredInitial = append(filteredInitial, r)
-	}
-	n.initialRoutes = filteredInitial
-
-	// routesForComparison excludes fake IP block for comparison with new routes
-	filteredComparison := make([]*route.Route, 0)
-	for _, r := range routesForComparison {
-		if r.IsDynamic() {
-			continue
-		}
-		filteredComparison = append(filteredComparison, r)
-	}
-	n.currentRoutes = filteredComparison
+	n.initialRoutes = filterStatic(initialRoutes)
+	n.currentRoutes = filterStatic(routesForComparison)
 }
 
 func (n *Notifier) OnNewRoutes(idMap route.HAMap) {
@@ -83,13 +68,43 @@ func (n *Notifier) notify() {
 		return
 	}
 
-	routeStrings := n.routesToStrings(n.currentRoutes)
+	allRoutes := slices.Clone(n.currentRoutes)
+	allRoutes = append(allRoutes, n.extraInitialRoutes()...)
+
+	routeStrings := n.routesToStrings(allRoutes)
 	sort.Strings(routeStrings)
 	go func(l listener.NetworkChangeListener) {
-		l.OnNetworkChanged(strings.Join(n.addIPv6RangeIfNeeded(routeStrings, n.currentRoutes), ","))
+		l.OnNetworkChanged(strings.Join(n.addIPv6RangeIfNeeded(routeStrings, allRoutes), ","))
 	}(n.listener)
 }
 
+// extraInitialRoutes returns initialRoutes whose network prefix is absent
+// from currentRoutes (e.g. the fake IP block added at setup time).
+func (n *Notifier) extraInitialRoutes() []*route.Route {
+	currentNets := make(map[netip.Prefix]struct{}, len(n.currentRoutes))
+	for _, r := range n.currentRoutes {
+		currentNets[r.Network] = struct{}{}
+	}
+
+	var extra []*route.Route
+	for _, r := range n.initialRoutes {
+		if _, ok := currentNets[r.Network]; !ok {
+			extra = append(extra, r)
+		}
+	}
+	return extra
+}
+
+func filterStatic(routes []*route.Route) []*route.Route {
+	out := make([]*route.Route, 0, len(routes))
+	for _, r := range routes {
+		if !r.IsDynamic() {
+			out = append(out, r)
+		}
+	}
+	return out
+}
+
 func (n *Notifier) routesToStrings(routes []*route.Route) []string {
 	nets := make([]string, 0, len(routes))
 	for _, r := range routes {