[client] Implement dns routes for Android (#3989)

client/internal/routemanager/notifier/notifier_android.go

@@ -0,0 +1,127 @@
+//go:build android
+
+package notifier
+
+import (
+	"net/netip"
+	"slices"
+	"sort"
+	"strings"
+	"sync"
+
+	"github.com/netbirdio/netbird/client/internal/listener"
+	"github.com/netbirdio/netbird/route"
+)
+
+type Notifier struct {
+	initialRoutes []*route.Route
+	currentRoutes []*route.Route
+
+	listener    listener.NetworkChangeListener
+	listenerMux sync.Mutex
+}
+
+func NewNotifier() *Notifier {
+	return &Notifier{}
+}
+
+func (n *Notifier) SetListener(listener listener.NetworkChangeListener) {
+	n.listenerMux.Lock()
+	defer n.listenerMux.Unlock()
+	n.listener = listener
+}
+
+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
+}
+
+func (n *Notifier) OnNewRoutes(idMap route.HAMap) {
+	var newRoutes []*route.Route
+	for _, routes := range idMap {
+		for _, r := range routes {
+			if r.IsDynamic() {
+				continue
+			}
+			newRoutes = append(newRoutes, r)
+		}
+	}
+
+	if !n.hasRouteDiff(n.currentRoutes, newRoutes) {
+		return
+	}
+
+	n.currentRoutes = newRoutes
+	n.notify()
+}
+
+func (n *Notifier) OnNewPrefixes([]netip.Prefix) {
+	// Not used on Android
+}
+
+func (n *Notifier) notify() {
+	n.listenerMux.Lock()
+	defer n.listenerMux.Unlock()
+	if n.listener == nil {
+		return
+	}
+
+	routeStrings := n.routesToStrings(n.currentRoutes)
+	sort.Strings(routeStrings)
+	go func(l listener.NetworkChangeListener) {
+		l.OnNetworkChanged(strings.Join(n.addIPv6RangeIfNeeded(routeStrings, n.currentRoutes), ","))
+	}(n.listener)
+}
+
+func (n *Notifier) routesToStrings(routes []*route.Route) []string {
+	nets := make([]string, 0, len(routes))
+	for _, r := range routes {
+		nets = append(nets, r.NetString())
+	}
+	return nets
+}
+
+func (n *Notifier) hasRouteDiff(a []*route.Route, b []*route.Route) bool {
+	slices.SortFunc(a, func(x, y *route.Route) int {
+		return strings.Compare(x.NetString(), y.NetString())
+	})
+	slices.SortFunc(b, func(x, y *route.Route) int {
+		return strings.Compare(x.NetString(), y.NetString())
+	})
+
+	return !slices.EqualFunc(a, b, func(x, y *route.Route) bool {
+		return x.NetString() == y.NetString()
+	})
+}
+
+func (n *Notifier) GetInitialRouteRanges() []string {
+	initialStrings := n.routesToStrings(n.initialRoutes)
+	sort.Strings(initialStrings)
+	return n.addIPv6RangeIfNeeded(initialStrings, n.initialRoutes)
+}
+
+func (n *Notifier) addIPv6RangeIfNeeded(inputRanges []string, routes []*route.Route) []string {
+	for _, r := range routes {
+		if r.Network.Addr().Is4() && r.Network.Bits() == 0 {
+			return append(slices.Clone(inputRanges), "::/0")
+		}
+	}
+	return inputRanges
+}