support set tun stack

service/src/main/java/com/github/kr328/clash/service/TunService.kt

@@ -218,6 +218,7 @@ class TunService : VpnService(), CoroutineScope by CoroutineScope(Dispatchers.De
             TunModule.TunDevice(
                 fd = establish()?.detachFd()
                     ?: throw NullPointerException("Establish VPN rejected by system"),
+                stack = store.tunStackMode,
                 gateway = "$TUN_GATEWAY/$TUN_SUBNET_PREFIX" + if (store.allowIpv6) ",$TUN_GATEWAY6/$TUN_SUBNET_PREFIX6" else "",
                 portal = TUN_PORTAL + if (store.allowIpv6) ",$TUN_PORTAL6" else "",
                 dns = if (store.dnsHijacking) NET_ANY else (TUN_DNS + if (store.allowIpv6) ",$TUN_DNS6" else ""),

service/src/main/java/com/github/kr328/clash/service/clash/module/TunModule.kt

@@ -15,6 +15,7 @@ import java.security.SecureRandom
 class TunModule(private val vpn: VpnService) : Module<Unit>(vpn) {
     data class TunDevice(
         val fd: Int,
+        var stack: String,
         val gateway: String,
         val portal: String,
         val dns: String,
@@ -56,6 +57,7 @@ class TunModule(private val vpn: VpnService) : Module<Unit>(vpn) {
     fun attach(device: TunDevice) {
         Clash.startTun(
             fd = device.fd,
+            stack = device.stack,
             gateway = device.gateway,
             portal = device.portal,
             dns = device.dns,

service/src/main/java/com/github/kr328/clash/service/store/ServiceStore.kt

@@ -56,6 +56,11 @@ class ServiceStore(context: Context) {
         defaultValue = false
     )
 
+    var tunStackMode by store.string(
+        key = "tun_stack_mode",
+        defaultValue = "system"
+    )
+
     var dynamicNotification by store.boolean(
         key = "dynamic_notification",
         defaultValue = true