318 lines
14 KiB
Kotlin
318 lines
14 KiB
Kotlin
package be.mygod.vpnhotspot.net
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import android.os.Build
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import be.mygod.vpnhotspot.App.Companion.app
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import be.mygod.vpnhotspot.R
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import be.mygod.vpnhotspot.net.monitor.DefaultNetworkMonitor
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import be.mygod.vpnhotspot.net.monitor.IpNeighbourMonitor
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import be.mygod.vpnhotspot.net.monitor.TrafficRecorder
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import be.mygod.vpnhotspot.net.monitor.UpstreamMonitor
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import be.mygod.vpnhotspot.room.AppDatabase
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import be.mygod.vpnhotspot.util.RootSession
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import be.mygod.vpnhotspot.util.computeIfAbsentCompat
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import be.mygod.vpnhotspot.widget.SmartSnackbar
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import kotlinx.coroutines.runBlocking
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import timber.log.Timber
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import java.net.*
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/**
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* A transaction wrapper that helps set up routing environment.
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*
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* Once revert is called, this object no longer serves any purpose.
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*/
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class Routing(private val caller: Any, private val downstream: String) : IpNeighbourMonitor.Callback {
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companion object {
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/**
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* Since Android 5.0, RULE_PRIORITY_TETHERING = 18000.
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* This also works for Wi-Fi direct where there's no rule at 18000.
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*
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* We override system tethering rules by adding our own rules at higher priority.
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*
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* Source: https://android.googlesource.com/platform/system/netd/+/b9baf26/server/RouteController.cpp#65
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*/
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private const val RULE_PRIORITY_UPSTREAM = 17800
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private const val RULE_PRIORITY_UPSTREAM_FALLBACK = 17900
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/**
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* -w <seconds> is not supported on 7.1-.
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* Fortunately there also isn't a time limit for starting a foreground service back in 7.1-.
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*
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* Source: https://android.googlesource.com/platform/external/iptables/+/android-5.0.0_r1/iptables/iptables.c#1574
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*/
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val IPTABLES = if (Build.VERSION.SDK_INT >= 26) "iptables -w 1" else "iptables -w"
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/**
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* For debugging: check that we do not start a Routing for the same interface twice.
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*/
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private var downstreams = mutableSetOf<String>()
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fun clean() {
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TrafficRecorder.clean()
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RootSession.use {
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it.execQuiet("$IPTABLES -t nat -F PREROUTING")
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it.execQuiet("while $IPTABLES -D FORWARD -j vpnhotspot_fwd; do done")
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it.execQuiet("$IPTABLES -F vpnhotspot_fwd")
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it.execQuiet("$IPTABLES -X vpnhotspot_fwd")
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it.execQuiet("while $IPTABLES -t nat -D POSTROUTING -j vpnhotspot_masquerade; do done")
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it.execQuiet("$IPTABLES -t nat -F vpnhotspot_masquerade")
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it.execQuiet("$IPTABLES -t nat -X vpnhotspot_masquerade")
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it.execQuiet("while ip rule del priority $RULE_PRIORITY_UPSTREAM; do done")
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it.execQuiet("while ip rule del priority $RULE_PRIORITY_UPSTREAM_FALLBACK; do done")
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}
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downstreams.clear()
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}
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private fun RootSession.Transaction.iptables(command: String, revert: String) {
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val result = execQuiet(command, revert)
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val message = RootSession.checkOutput(command, result, err = false)
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if (result.err.isNotEmpty()) Timber.i(message) // busy wait message
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}
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private fun RootSession.Transaction.iptablesAdd(content: String, table: String = "filter") =
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iptables("$IPTABLES -t $table -A $content", "$IPTABLES -t $table -D $content")
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private fun RootSession.Transaction.iptablesInsert(content: String, table: String = "filter") =
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iptables("$IPTABLES -t $table -I $content", "$IPTABLES -t $table -D $content")
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private fun RootSession.Transaction.ndc(name: String, command: String, revert: String) {
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val result = execQuiet(command, revert)
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val log = RootSession.checkOutput(command, result,
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result.out.lastOrNull() != "200 0 $name operation succeeded")
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if (result.out.size > 1) Timber.i(log)
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}
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}
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enum class MasqueradeMode {
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None, Simple, Netd
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}
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class InterfaceNotFoundException(override val cause: Throwable) : SocketException() {
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override val message: String get() = app.getString(R.string.exception_interface_not_found)
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}
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init {
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check(downstreams.add(downstream)) { "Double routing detected from $caller" }
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}
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private val hostAddress = try {
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NetworkInterface.getByName(downstream)!!.interfaceAddresses!!.asSequence().single { it.address is Inet4Address }
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} catch (e: Exception) {
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throw InterfaceNotFoundException(e)
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}
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private val hostSubnet = "${hostAddress.address.hostAddress}/${hostAddress.networkPrefixLength}"
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private val transaction = RootSession.beginTransaction()
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private var masqueradeMode = MasqueradeMode.None
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private val upstreams = HashSet<String>()
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private open inner class Upstream(val priority: Int) : UpstreamMonitor.Callback {
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/**
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* The only case when upstream is null is on API 23- and we are using system default rules.
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*/
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inner class Subrouting(priority: Int, val upstream: String? = null) {
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val transaction = RootSession.beginTransaction().safeguard {
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if (upstream != null) {
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exec("ip rule add from all iif $downstream lookup $upstream priority $priority",
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// by the time stopScript is called, table entry for upstream may already get removed
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"ip rule del from all iif $downstream priority $priority")
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}
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when (masqueradeMode) {
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MasqueradeMode.None -> { } // nothing to be done here
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// note: specifying -i wouldn't work for POSTROUTING
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MasqueradeMode.Simple -> {
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iptablesAdd(if (upstream == null) "vpnhotspot_masquerade -s $hostSubnet -j MASQUERADE" else
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"vpnhotspot_masquerade -s $hostSubnet -o $upstream -j MASQUERADE", "nat")
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}
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MasqueradeMode.Netd -> {
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check(upstream != null)
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/**
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* 0 means that there are no interface addresses coming after, which is unused anyway.
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*
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* https://android.googlesource.com/platform/frameworks/base/+/android-5.0.0_r1/services/core/java/com/android/server/NetworkManagementService.java#1251
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* https://android.googlesource.com/platform/system/netd/+/android-5.0.0_r1/server/CommandListener.cpp#638
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*/
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ndc("Nat", "ndc nat enable $downstream $upstream 0", "ndc nat disable $downstream $upstream 0")
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}
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}
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}
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}
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var subrouting: Subrouting? = null
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var dns: List<InetAddress> = emptyList()
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override fun onAvailable(ifname: String, dns: List<InetAddress>) = synchronized(this@Routing) {
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val subrouting = subrouting
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when {
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subrouting != null -> check(subrouting.upstream == ifname)
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!upstreams.add(ifname) -> return
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else -> this.subrouting = try {
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Subrouting(priority, ifname)
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} catch (e: Exception) {
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SmartSnackbar.make(e).show()
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Timber.w(e)
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null
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}
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}
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this.dns = dns
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updateDnsRoute()
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}
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override fun onLost() = synchronized(this@Routing) {
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val subrouting = subrouting ?: return
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// we could be removing fallback subrouting which no collision could ever happen, check before removing
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if (subrouting.upstream != null) check(upstreams.remove(subrouting.upstream))
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subrouting.transaction.revert()
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this.subrouting = null
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dns = emptyList()
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updateDnsRoute()
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}
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}
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private val fallbackUpstream = object : Upstream(RULE_PRIORITY_UPSTREAM_FALLBACK) {
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override fun onFallback() = synchronized(this@Routing) {
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check(subrouting == null)
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subrouting = try {
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Subrouting(priority)
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} catch (e: Exception) {
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SmartSnackbar.make(e).show()
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Timber.w(e)
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null
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}
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updateDnsRoute()
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}
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}
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private val upstream = Upstream(RULE_PRIORITY_UPSTREAM)
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private inner class Client(private val ip: Inet4Address, mac: Long) : AutoCloseable {
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private val transaction = RootSession.beginTransaction().safeguard {
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val address = ip.hostAddress
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iptablesInsert("vpnhotspot_fwd -i $downstream -s $address -j ACCEPT")
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iptablesInsert("vpnhotspot_fwd -o $downstream -d $address -m state --state ESTABLISHED,RELATED -j ACCEPT")
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}
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init {
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try {
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TrafficRecorder.register(ip, downstream, mac)
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} catch (e: Exception) {
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close()
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throw e
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}
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}
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override fun close() {
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TrafficRecorder.unregister(ip, downstream)
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transaction.revert()
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}
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}
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private val clients = HashMap<InetAddress, Client>()
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override fun onIpNeighbourAvailable(neighbours: List<IpNeighbour>) = synchronized(this) {
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val toRemove = HashSet(clients.keys)
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for (neighbour in neighbours) {
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if (neighbour.dev != downstream || neighbour.ip !is Inet4Address ||
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runBlocking { AppDatabase.instance.clientRecordDao.lookup(neighbour.lladdr) }
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?.blocked == true) continue
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toRemove.remove(neighbour.ip)
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try {
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clients.computeIfAbsentCompat(neighbour.ip) { Client(neighbour.ip, neighbour.lladdr) }
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} catch (e: Exception) {
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Timber.w(e)
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SmartSnackbar.make(e).show()
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}
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}
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if (toRemove.isNotEmpty()) {
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TrafficRecorder.update() // record stats before removing rules to prevent stats losing
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for (address in toRemove) clients.remove(address)!!.close()
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}
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}
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/**
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* This command is available since API 23 and also handles IPv6 forwarding.
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* https://android.googlesource.com/platform/system/netd/+/android-6.0.0_r1/server/CommandListener.cpp#527
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*
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* `requester` set by system service is assumed to be `tethering`.
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* https://android.googlesource.com/platform/frameworks/base/+/bd249a19bba38a29e617aa849b2f42c3c281eff5/services/core/java/com/android/server/NetworkManagementService.java#1241
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*
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* The fallback approach is consistent with legacy system's IP forwarding approach,
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* but may be broken when system tethering shutdown before local-only interfaces.
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*/
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fun ipForward() {
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if (Build.VERSION.SDK_INT >= 23) try {
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transaction.ndc("ipfwd", "ndc ipfwd enable vpnhotspot_$downstream",
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"ndc ipfwd disable vpnhotspot_$downstream")
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return
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} catch (e: RootSession.UnexpectedOutputException) {
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Timber.w(e)
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}
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transaction.exec("echo 1 >/proc/sys/net/ipv4/ip_forward")
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}
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/**
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* Alternative approach: ndc interface ipv6 $downstream <enable|disable>
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*
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* This approach does the same (up until now) and is easier for parsing error output.
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*/
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fun disableIpv6() = transaction.exec("echo 1 >/proc/sys/net/ipv6/conf/$downstream/disable_ipv6",
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"echo 0 >/proc/sys/net/ipv6/conf/$downstream/disable_ipv6")
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fun forward() {
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transaction.execQuiet("$IPTABLES -N vpnhotspot_fwd")
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transaction.iptablesInsert("FORWARD -j vpnhotspot_fwd")
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transaction.iptablesAdd("vpnhotspot_fwd -i $downstream ! -o $downstream -j DROP") // ensure blocking works
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// the real forwarding filters will be added in Subrouting when clients are connected
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}
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fun masquerade(mode: MasqueradeMode) {
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masqueradeMode = mode
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if (mode == MasqueradeMode.Simple) {
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transaction.execQuiet("$IPTABLES -t nat -N vpnhotspot_masquerade")
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transaction.iptablesInsert("POSTROUTING -j vpnhotspot_masquerade", "nat")
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// further rules are added when upstreams are found
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}
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}
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private inner class DnsRoute(val dns: String) {
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val transaction = RootSession.beginTransaction().safeguard {
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val hostAddress = hostAddress.address.hostAddress
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iptablesAdd("PREROUTING -i $downstream -p tcp -d $hostAddress --dport 53 -j DNAT --to-destination $dns", "nat")
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iptablesAdd("PREROUTING -i $downstream -p udp -d $hostAddress --dport 53 -j DNAT --to-destination $dns", "nat")
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}
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}
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private var currentDns: DnsRoute? = null
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private fun updateDnsRoute() {
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var dns = (upstream.dns + fallbackUpstream.dns).firstOrNull { it is Inet4Address }?.hostAddress
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if (dns.isNullOrBlank()) dns = null
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if (dns != currentDns?.dns) {
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currentDns?.transaction?.revert()
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currentDns = if (dns == null) null else try {
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DnsRoute(dns)
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} catch (e: RuntimeException) {
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Timber.w(e)
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SmartSnackbar.make(e).show()
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null
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}
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}
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}
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fun stop() {
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IpNeighbourMonitor.unregisterCallback(this)
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DefaultNetworkMonitor.unregisterCallback(fallbackUpstream)
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UpstreamMonitor.unregisterCallback(upstream)
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}
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fun commit(localOnly: Boolean = false) {
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transaction.commit()
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Timber.i("Started routing for $downstream by $caller")
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if (localOnly || masqueradeMode != MasqueradeMode.Netd) DefaultNetworkMonitor.registerCallback(fallbackUpstream)
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UpstreamMonitor.registerCallback(upstream)
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IpNeighbourMonitor.registerCallback(this)
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}
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fun revert() {
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stop()
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Timber.i("Stopped routing for $downstream by $caller")
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TrafficRecorder.update() // record stats before exiting to prevent stats losing
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clients.values.forEach { it.close() }
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currentDns?.transaction?.revert()
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fallbackUpstream.subrouting?.transaction?.revert()
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upstream.subrouting?.transaction?.revert()
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transaction.revert()
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check(downstreams.remove(downstream)) { "Double reverting detected from $caller" }
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}
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}
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