Use /system/bin/ip and ifindex for lookup

README.md

@@ -304,7 +304,7 @@ Undocumented system binaries are all bundled and executable:
 
 * (since API 24) `iptables-save`, `ip6tables-save`;
 * `echo`;
-* `ip` (`link monitor neigh rule`);
+* `/system/bin/ip` (`link monitor neigh rule unreachable`);
 * `ndc` (`ipfwd` since API 23, `nat` since API 28);
 * `iptables`, `ip6tables` (with correct version corresponding to API level, `-nvx -L <chain>`);
 * `sh`;

mobile/src/main/java/be/mygod/vpnhotspot/net/DhcpWorkaround.kt

@@ -2,6 +2,7 @@ package be.mygod.vpnhotspot.net
 
 import android.content.SharedPreferences
 import be.mygod.vpnhotspot.App.Companion.app
+import be.mygod.vpnhotspot.net.Routing.Companion.IP
 import be.mygod.vpnhotspot.root.RoutingCommands
 import be.mygod.vpnhotspot.util.RootSession
 import be.mygod.vpnhotspot.widget.SmartSnackbar
@@ -32,7 +33,7 @@ object DhcpWorkaround : SharedPreferences.OnSharedPreferenceChangeListener {
         try {
             RootSession.use {
                 try {
-                    it.exec("ip rule $action iif lo uidrange 0-0 lookup local_network priority 11000")
+                    it.exec("$IP rule $action iif lo uidrange 0-0 lookup local_network priority 11000")
                 } catch (e: RoutingCommands.UnexpectedOutputException) {
                     if (Routing.shouldSuppressIpError(e, enabled)) return@use
                     Timber.w(IOException("Failed to tweak dhcp workaround rule", e))

mobile/src/main/java/be/mygod/vpnhotspot/net/Routing.kt

@@ -14,6 +14,8 @@ import be.mygod.vpnhotspot.room.AppDatabase
 import be.mygod.vpnhotspot.root.RootManager
 import be.mygod.vpnhotspot.root.RoutingCommands
 import be.mygod.vpnhotspot.util.RootSession
+import be.mygod.vpnhotspot.util.if_nametoindex
+import be.mygod.vpnhotspot.util.parseNumericAddress
 import be.mygod.vpnhotspot.widget.SmartSnackbar
 import timber.log.Timber
 import java.io.BufferedWriter
@@ -43,6 +45,8 @@ class Routing(private val caller: Any, private val downstream: String) : IpNeigh
         private const val RULE_PRIORITY_UPSTREAM_FALLBACK = 17900
         private const val RULE_PRIORITY_UPSTREAM_DISABLE_SYSTEM = 17980
 
+        private const val ROOT_DIR = "/system/bin/"
+        const val IP = "${ROOT_DIR}ip"
         const val IPTABLES = "iptables -w"
         const val IP6TABLES = "ip6tables -w"
 
@@ -61,10 +65,10 @@ class Routing(private val caller: Any, private val downstream: String) : IpNeigh
             commands.appendln("while $IP6TABLES -D OUTPUT -j vpnhotspot_filter; do done")
             commands.appendln("$IP6TABLES -F vpnhotspot_filter")
             commands.appendln("$IP6TABLES -X vpnhotspot_filter")
-            commands.appendln("while ip rule del priority $RULE_PRIORITY_DNS; do done")
+            commands.appendln("while $IP rule del priority $RULE_PRIORITY_DNS; do done")
-            commands.appendln("while ip rule del priority $RULE_PRIORITY_UPSTREAM; do done")
+            commands.appendln("while $IP rule del priority $RULE_PRIORITY_UPSTREAM; do done")
-            commands.appendln("while ip rule del priority $RULE_PRIORITY_UPSTREAM_FALLBACK; do done")
+            commands.appendln("while $IP rule del priority $RULE_PRIORITY_UPSTREAM_FALLBACK; do done")
-            commands.appendln("while ip rule del priority $RULE_PRIORITY_UPSTREAM_DISABLE_SYSTEM; do done")
+            commands.appendln("while $IP rule del priority $RULE_PRIORITY_UPSTREAM_DISABLE_SYSTEM; do done")
         }
 
         suspend fun clean() {
@@ -99,17 +103,17 @@ class Routing(private val caller: Any, private val downstream: String) : IpNeigh
                 } == e.result.err.trim()
     }
 
-    private fun RootSession.Transaction.ipRule(add: String, priority: Int, rule: String = "", del: String = add) {
+    private fun RootSession.Transaction.ipRule(action: String, priority: Int, rule: String = "") {
         try {
-            exec("ip rule add $rule iif $downstream $add priority $priority",
+            exec("$IP rule add $rule iif $downstream $action priority $priority",
-                    "ip rule del $rule iif $downstream $del priority $priority")
+                    "$IP rule del $rule iif $downstream $action priority $priority")
         } catch (e: RoutingCommands.UnexpectedOutputException) {
             if (!shouldSuppressIpError(e)) throw e
         }
     }
-    private fun RootSession.Transaction.ipRuleLookup(upstream: String, priority: Int, rule: String = "") =
+    private fun RootSession.Transaction.ipRuleLookup(ifindex: Int, priority: Int, rule: String = "") =
-            // by the time stopScript is called, table entry for upstream may already get removed
+            // https://android.googlesource.com/platform/system/netd/+/android-5.0.0_r1/server/RouteController.h#37
-            ipRule("lookup $upstream", priority, rule, "")
+            ipRule("lookup ${1000 + ifindex}", priority, rule)
 
     enum class MasqueradeMode {
         None,
@@ -148,8 +152,9 @@ class Routing(private val caller: Any, private val downstream: String) : IpNeigh
          * The only case when upstream is null is on API 23- and we are using system default rules.
          */
         inner class Subrouting(priority: Int, val upstream: String? = null) {
+            val ifindex = if (upstream == null) 0 else if_nametoindex(upstream).also { check(it != 0) }
             val transaction = RootSession.beginTransaction().safeguard {
-                if (upstream != null) ipRuleLookup(upstream, priority)
+                if (upstream != null) ipRuleLookup(ifindex, priority)
                 @TargetApi(28) when (masqueradeMode) {
                     MasqueradeMode.None -> { }  // nothing to be done here
                     MasqueradeMode.Simple -> {
@@ -216,6 +221,7 @@ class Routing(private val caller: Any, private val downstream: String) : IpNeigh
                 Timber.w(e)
                 null
             }
+            dns = listOf(parseNumericAddress("8.8.8.8"))
             updateDnsRoute()
         }
     }
@@ -313,10 +319,10 @@ class Routing(private val caller: Any, private val downstream: String) : IpNeigh
         }
     }
 
-    private inner class DnsRoute(val upstream: String, val dns: String) {
+    private inner class DnsRoute(val ifindex: Int, val dns: String) {
         val transaction = RootSession.beginTransaction().safeguard {
             val hostAddress = hostAddress.address.hostAddress
-            ipRuleLookup(upstream, RULE_PRIORITY_DNS, "to $dns")
+            ipRuleLookup(ifindex, RULE_PRIORITY_DNS, "to $dns")
             iptablesAdd("PREROUTING -i $downstream -p tcp -d $hostAddress --dport 53 -j DNAT --to-destination $dns", "nat")
             iptablesAdd("PREROUTING -i $downstream -p udp -d $hostAddress --dport 53 -j DNAT --to-destination $dns", "nat")
         }
@@ -324,16 +330,16 @@ class Routing(private val caller: Any, private val downstream: String) : IpNeigh
     private var currentDns: DnsRoute? = null
     private fun updateDnsRoute() {
         val selected = sequenceOf(upstream, fallbackUpstream).flatMap { upstream ->
-            val ifname = upstream.subrouting?.upstream
+            val ifindex = upstream.subrouting?.ifindex ?: 0
-            if (ifname == null) emptySequence() else upstream.dns.asSequence().map { ifname to it }
+            if (ifindex == 0) emptySequence() else upstream.dns.asSequence().map { ifindex to it }
         }.firstOrNull { it.second is Inet4Address }
-        val upstream = selected?.first
+        val ifindex = selected?.first ?: 0
         var dns = selected?.second?.hostAddress
         if (dns.isNullOrBlank()) dns = null
-        if (upstream != currentDns?.upstream || dns != currentDns?.dns) {
+        if (ifindex != currentDns?.ifindex || dns != currentDns?.dns) {
             currentDns?.transaction?.revert()
-            currentDns = if (upstream == null || dns == null) null else try {
+            currentDns = if (ifindex == 0 || dns == null) null else try {
-                DnsRoute(upstream, dns)
+                DnsRoute(ifindex, dns)
             } catch (e: RuntimeException) {
                 Timber.w(e)
                 SmartSnackbar.make(e).show()

mobile/src/main/java/be/mygod/vpnhotspot/net/monitor/IpMonitor.kt

@@ -8,6 +8,7 @@ import be.mygod.librootkotlinx.RootServer
 import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.BuildConfig
 import be.mygod.vpnhotspot.R
+import be.mygod.vpnhotspot.net.Routing
 import be.mygod.vpnhotspot.root.ProcessData
 import be.mygod.vpnhotspot.root.ProcessListener
 import be.mygod.vpnhotspot.root.RootManager
@@ -104,14 +105,14 @@ abstract class IpMonitor {
             if (mode.isMonitor) {
                 if (mode != Mode.MonitorRoot) {
                     // monitor may get rejected by SELinux enforcing
-                    handleProcess(ProcessBuilder("ip", "monitor", monitoredObject))
+                    handleProcess(ProcessBuilder(Routing.IP, "monitor", monitoredObject))
                     if (destroyed) return@thread
                 }
                 try {
                     runBlocking(EmptyCoroutineContext + worker) {
                         RootManager.use { server ->
                             // while we only need to use this server once, we need to also keep the server alive
-                            handleChannel(server.create(ProcessListener(errorMatcher, "ip", "monitor", monitoredObject),
+                            handleChannel(server.create(ProcessListener(errorMatcher, Routing.IP, "monitor", monitoredObject),
                                     this))
                         }
                     }
@@ -152,7 +153,7 @@ abstract class IpMonitor {
         }
         var newServer = server
         try {
-            val command = listOf("ip", monitoredObject)
+            val command = listOf(Routing.IP, monitoredObject)
             val result = (server ?: RootManager.acquire().also { newServer = it })
                     .execute(RoutingCommands.Process(command))
             result.check(command, false)
@@ -167,7 +168,7 @@ abstract class IpMonitor {
     }
 
     private fun poll() {
-        val process = ProcessBuilder("ip", monitoredObject)
+        val process = ProcessBuilder(Routing.IP, monitoredObject)
                 .redirectErrorStream(true)
                 .start()
         process.waitFor()

mobile/src/main/java/be/mygod/vpnhotspot/root/MiscCommands.kt

@@ -8,7 +8,8 @@ import android.provider.Settings
 import androidx.annotation.RequiresApi
 import be.mygod.librootkotlinx.*
 import be.mygod.vpnhotspot.App.Companion.app
-import be.mygod.vpnhotspot.net.Routing
+import be.mygod.vpnhotspot.net.Routing.Companion.IP
+import be.mygod.vpnhotspot.net.Routing.Companion.IPTABLES
 import be.mygod.vpnhotspot.net.TetheringManager
 import be.mygod.vpnhotspot.util.Services
 import kotlinx.android.parcel.Parcelize
@@ -50,16 +51,16 @@ class Dump(val path: String, val cacheDir: File = app.deviceStorage.codeCacheDir
                     |$ip6tablesSave
                     |echo
                     |echo ip rule
-                    |ip rule
+                    |$IP rule
                     |echo
                     |echo ip neigh
-                    |ip neigh
+                    |$IP neigh
                     |echo
                     |echo iptables -nvx -L vpnhotspot_fwd
-                    |${Routing.IPTABLES} -nvx -L vpnhotspot_fwd
+                    |$IPTABLES -nvx -L vpnhotspot_fwd
                     |echo
                     |echo iptables -nvx -L vpnhotspot_acl
-                    |${Routing.IPTABLES} -nvx -L vpnhotspot_acl
+                    |$IPTABLES -nvx -L vpnhotspot_acl
                     |echo
                     |echo logcat-su
                     |logcat -d

mobile/src/main/java/be/mygod/vpnhotspot/util/Utils.kt

@@ -7,6 +7,7 @@ import android.net.InetAddresses
 import android.os.Build
 import android.os.Handler
 import android.os.RemoteException
+import android.system.Os
 import android.text.Spannable
 import android.text.SpannableString
 import android.text.SpannableStringBuilder
@@ -24,6 +25,7 @@ import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.net.MacAddressCompat
 import be.mygod.vpnhotspot.widget.SmartSnackbar
 import timber.log.Timber
+import java.io.File
 import java.lang.invoke.MethodHandles
 import java.lang.reflect.InvocationHandler
 import java.lang.reflect.InvocationTargetException
@@ -150,3 +152,7 @@ fun InvocationHandler.callSuper(interfaceClass: Class<*>, proxy: Any, method: Me
         null
     }
 }
+
+fun if_nametoindex(ifname: String) = if (Build.VERSION.SDK_INT >= 26) {
+    Os.if_nametoindex(ifname)
+} else File("/sys/class/net/$ifname/ifindex").inputStream().bufferedReader().readText().toInt()