fix(tun): make FakeDNS UDP listener persistent and fix SOCKS tracking half-close and IPv6 route capture

Author: Drakaris-Test

android/app/src/main/java/com/masterdns/vpn/service/MasterDnsVpnService.kt

@@ -396,6 +396,17 @@ class MasterDnsVpnService : VpnService() {
             VpnManager.appendLog("Added fake DNS route: 198.18.0.0/16")
         }
 
+        // Route IPv6 into VPN so apps don't leak or hang on IPv6 DNS / connections
+        runCatching {
+            builder.addAddress("fd00::1", 128)
+            builder.addRoute("::", 0)
+            if (inputs.globalSettings.fakeDnsEnabled) {
+                builder.addDnsServer("fd00::2")
+            }
+        }.onFailure { e ->
+            VpnManager.appendLog("IPv6 VPN route setup: ${e.message}")
+        }
+
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
             val splitEnabled = inputs.globalSettings.splitTunnelingEnabled &&
                 inputs.globalSettings.splitPackagesCsv.isNotBlank()

mobile/mobile.go

@@ -113,16 +113,26 @@ func handleTracking(c net.Conn, realProxyAddr string) {
 		onWrite: func(n int64) { atomic.AddInt64(&trackedDown, n) },
 	}
 
-	errc := make(chan error, 2)
+	var wg sync.WaitGroup
+	wg.Add(2)
+
 	go func() {
-		_, err := io.Copy(server, tcClient)
-		errc <- err
+		defer wg.Done()
+		_, _ = io.Copy(server, tcClient)
+		if tc, ok := server.(interface{ CloseWrite() error }); ok {
+			_ = tc.CloseWrite()
+		}
 	}()
+
 	go func() {
-		_, err := io.Copy(tcClient, server)
-		errc <- err
+		defer wg.Done()
+		_, _ = io.Copy(tcClient, server)
+		if tc, ok := tcClient.Conn.(interface{ CloseWrite() error }); ok {
+			_ = tc.CloseWrite()
+		}
 	}()
-	<-errc
+
+	wg.Wait()
 }
 
 // Bandwidth holds upload and download counters for gomobile bindings.

mobile/tun/dns_mapper.go

@@ -3,6 +3,7 @@ package tun
 import (
 	"fmt"
 	"log"
+	"strings"
 	"sync"
 	"sync/atomic"
 )
@@ -26,7 +27,9 @@ func (d *DNSMapper) GetFakeIP(hostname string) string {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 
-	if ip, ok := d.hostnameToIP[hostname]; ok {
+	normalized := strings.ToLower(strings.TrimSuffix(hostname, "."))
+
+	if ip, ok := d.hostnameToIP[normalized]; ok {
 		return ip
 	}
 
@@ -40,10 +43,10 @@ func (d *DNSMapper) GetFakeIP(hostname string) string {
 	octet4 := byte(counter & 0xFF)
 	fakeIP := fmt.Sprintf("198.18.%d.%d", octet3, octet4)
 
-	d.hostnameToIP[hostname] = fakeIP
-	d.ipToHostname[fakeIP] = hostname
+	d.hostnameToIP[normalized] = fakeIP
+	d.ipToHostname[fakeIP] = normalized
 
-	log.Printf("[TUN-DNS] Mapped %s -> %s", hostname, fakeIP)
+	log.Printf("[TUN-DNS] Mapped %s -> %s", normalized, fakeIP)
 	return fakeIP
 }
 

mobile/tun/dns_mapper_test.go

@@ -29,6 +29,22 @@ func TestDNSMapper_GetFakeIP_StableForSameHostname(t *testing.T) {
 	}
 }
 
+func TestDNSMapper_GetFakeIP_CaseInsensitiveAndDotNormalization(t *testing.T) {
+	d := NewDNSMapper()
+
+	first := d.GetFakeIP("WwW.GoOgLe.CoM")
+	second := d.GetFakeIP("www.google.com.")
+	third := d.GetFakeIP("WWW.GOOGLE.COM")
+	if first != second || second != third {
+		t.Fatalf("case-randomized hostnames mapped differently: %q vs %q vs %q", first, second, third)
+	}
+
+	host, ok := d.GetHostname(first)
+	if !ok || host != "www.google.com" {
+		t.Fatalf("GetHostname(%q) = %q (ok=%v), want www.google.com", first, host, ok)
+	}
+}
+
 func TestDNSMapper_GetHostname_RoundTrips(t *testing.T) {
 	d := NewDNSMapper()