Replace strict mode with fallback upstream interface

Fixes #40. Apparently we can no longer take advantage of default network rules set by Android system since Android 9.0 thanks to this commit: 758627c4d9

mobile/src/main/java/be/mygod/vpnhotspot/LocalOnlyInterfaceManager.kt

@@ -1,54 +1,33 @@
 package be.mygod.vpnhotspot
 
-import android.content.Context
 import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.net.Routing
-import be.mygod.vpnhotspot.net.monitor.UpstreamMonitor
 import be.mygod.vpnhotspot.widget.SmartSnackbar
 import timber.log.Timber
-import java.net.InetAddress
 import java.net.InterfaceAddress
 
-class LocalOnlyInterfaceManager(private val owner: Context, val downstream: String) : UpstreamMonitor.Callback {
+class LocalOnlyInterfaceManager(val downstream: String) {
     private var routing: Routing? = null
-    private var dns = emptyList<InetAddress>()
 
     init {
         app.cleanRoutings[this] = this::clean
-        UpstreamMonitor.registerCallback(this) { initRouting() }
-    }
-
-    override fun onAvailable(ifname: String, dns: List<InetAddress>) {
-        val routing = routing
-        initRouting(ifname, if (routing == null) null else {
-            routing.revert()
-            routing.hostAddress
-        }, dns)
-    }
-    override fun onLost() {
-        val routing = routing ?: return
-        routing.revert()
-        initRouting(null, routing.hostAddress, emptyList())
+        initRouting()
     }
 
     private fun clean() {
         val routing = routing ?: return
         routing.stop()
-        initRouting(routing.upstream, routing.hostAddress, dns)
+        initRouting(routing.hostAddress)
     }
 
-    private fun initRouting(upstream: String? = null, owner: InterfaceAddress? = null,
-                            dns: List<InetAddress> = this.dns) {
-        this.dns = dns
-        try {
-            routing = Routing(this.owner, upstream, downstream, owner, app.strict).apply {
+    private fun initRouting(owner: InterfaceAddress? = null) {
+        routing = try {
+            Routing(downstream, owner).apply {
                 try {
                     if (app.dhcpWorkaround) dhcpWorkaround()
                     ipForward()                                     // local only interfaces need to enable ip_forward
-                    rule()
                     forward()
                     if (app.masquerade) masquerade()
-                    dnsRedirect(dns)
                     commit()
                 } catch (e: Exception) {
                     revert()
@@ -58,12 +37,11 @@ class LocalOnlyInterfaceManager(private val owner: Context, val downstream: Stri
         } catch (e: Exception) {
             SmartSnackbar.make(e.localizedMessage).show()
             Timber.w(e)
-            routing = null
+            null
         }
     }
 
     fun stop() {
-        UpstreamMonitor.unregisterCallback(this)
         app.cleanRoutings -= this
         routing?.revert()
     }