[client] Fix iOS DNS upstream routing for deselected exit nodes (#5803)

- Add GetSelectedClientRoutes() to the route manager that filters through FilterSelectedExitNodes, returning only active routes instead of all management routes              
  - Use GetSelectedClientRoutes() in the DNS route checker so deselected exit nodes' 0.0.0.0/0 no longer matches upstream DNS IPs — this prevented the resolver from switching
  away from the utun-bound socket after exit node deselection                                                                                                                   
  - Initialize iOS DNS server with host DNS fallback addresses (1.1.1.1:53, 1.0.0.1:53) and a permanent root zone handler, matching Android's behavior — without this, unmatched
   DNS queries arriving via the 0.0.0.0/0 tunnel route had no handler and were silently dropped

client/internal/connect.go

@@ -111,6 +111,7 @@ func (c *ConnectClient) RunOniOS(
 	fileDescriptor int32,
 	networkChangeListener listener.NetworkChangeListener,
 	dnsManager dns.IosDnsManager,
+	dnsAddresses []netip.AddrPort,
 	stateFilePath string,
 ) error {
 	// Set GC percent to 5% to reduce memory usage as iOS only allows 50MB of memory for the extension.
@@ -120,6 +121,7 @@ func (c *ConnectClient) RunOniOS(
 		FileDescriptor:        fileDescriptor,
 		NetworkChangeListener: networkChangeListener,
 		DnsManager:            dnsManager,
+		HostDNSAddresses:      dnsAddresses,
 		StateFilePath:         stateFilePath,
 	}
 	return c.run(mobileDependency, nil, "")

client/internal/dns/server.go

@@ -187,11 +187,16 @@ func NewDefaultServerIos(
 	ctx context.Context,
 	wgInterface WGIface,
 	iosDnsManager IosDnsManager,
+	hostsDnsList []netip.AddrPort,
 	statusRecorder *peer.Status,
 	disableSys bool,
 ) *DefaultServer {
+	log.Debugf("iOS host dns address list is: %v", hostsDnsList)
 	ds := newDefaultServer(ctx, wgInterface, NewServiceViaMemory(wgInterface), statusRecorder, nil, disableSys)
 	ds.iosDnsManager = iosDnsManager
+	ds.hostsDNSHolder.set(hostsDnsList)
+	ds.permanent = true
+	ds.addHostRootZone()
 	return ds
 }
 

client/internal/engine.go

@@ -1805,7 +1805,7 @@ func (e *Engine) newDnsServer(dnsConfig *nbdns.Config) (dns.Server, error) {
 		return dnsServer, nil
 
 	case "ios":
-		dnsServer := dns.NewDefaultServerIos(e.ctx, e.wgInterface, e.mobileDep.DnsManager, e.statusRecorder, e.config.DisableDNS)
+		dnsServer := dns.NewDefaultServerIos(e.ctx, e.wgInterface, e.mobileDep.DnsManager, e.mobileDep.HostDNSAddresses, e.statusRecorder, e.config.DisableDNS)
 		return dnsServer, nil
 
 	default:

client/internal/routemanager/notifier/notifier_ios.go

@@ -53,7 +53,6 @@ func (n *Notifier) OnNewPrefixes(prefixes []netip.Prefix) {
 	n.currentPrefixes = newNets
 	n.notify()
 }
-
 func (n *Notifier) notify() {
 	n.listenerMux.Lock()
 	defer n.listenerMux.Unlock()