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163 changes: 163 additions & 0 deletions
163
core/src/main/java/com/github/shadowsocks/net/LocalDnsServer.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,163 @@ | ||
| package com.github.shadowsocks.net | ||
|
|
||
| import android.os.ParcelFileDescriptor | ||
| import android.util.Log | ||
| import com.github.shadowsocks.preference.DataStore | ||
| import com.github.shadowsocks.utils.parseNumericAddress | ||
| import com.github.shadowsocks.utils.printLog | ||
| import com.github.shadowsocks.utils.shutdown | ||
| import kotlinx.coroutines.* | ||
| import net.sourceforge.jsocks.Socks5DatagramSocket | ||
| import net.sourceforge.jsocks.Socks5Proxy | ||
| import org.xbill.DNS.* | ||
| import java.io.Closeable | ||
| import java.io.FileDescriptor | ||
| import java.io.IOException | ||
| import java.net.* | ||
| import java.nio.ByteBuffer | ||
| import java.util.* | ||
| import java.util.concurrent.ConcurrentHashMap | ||
|
|
||
| /** | ||
| * A simple DNS conditional forwarder. | ||
| * | ||
| * No cache is provided as localResolver may change from time to time. We expect DNS clients to do cache themselves. | ||
| * | ||
| * Based on: | ||
| * https://github.com/bitcoinj/httpseed/blob/809dd7ad9280f4bc98a356c1ffb3d627bf6c7ec5/src/main/kotlin/dns.kt | ||
| * https://github.com/shadowsocks/overture/tree/874f22613c334a3b78e40155a55479b7b69fee04 | ||
| */ | ||
| class LocalDnsServer(private val localResolver: suspend (String) -> Array<InetAddress>, | ||
| private val remoteDns: InetAddress) : SocketListener("LocalDnsServer"), CoroutineScope { | ||
| /** | ||
| * Forward all requests to remote and ignore localResolver. | ||
| */ | ||
| var forwardOnly = false | ||
| /** | ||
| * Forward UDP queries to TCP. | ||
| */ | ||
| var tcp = true | ||
| var remoteDomainMatcher: Regex? = null | ||
| var localIpMatcher: List<Subnet> = emptyList() | ||
|
|
||
| companion object { | ||
| private const val TIMEOUT = 10_000L | ||
| /** | ||
| * TTL returned from localResolver is set to 120. Android API does not provide TTL, | ||
| * so we suppose Android apps should not care about TTL either. | ||
| */ | ||
| private const val TTL = 120L | ||
| private const val UDP_PACKET_SIZE = 1500 | ||
|
|
||
| } | ||
| private val socket = DatagramSocket(DataStore.portLocalDns, DataStore.listenAddress.parseNumericAddress()) | ||
| private val DatagramSocket.fileDescriptor get() = ParcelFileDescriptor.fromDatagramSocket(this).fileDescriptor | ||
| override val fileDescriptor get() = socket.fileDescriptor | ||
| private val tcpProxy = DataStore.proxy | ||
| private val udpProxy = Socks5Proxy("127.0.0.1", DataStore.portProxy) | ||
|
|
||
| private val activeFds = Collections.newSetFromMap(ConcurrentHashMap<FileDescriptor, Boolean>()) | ||
| private val job = SupervisorJob() | ||
| override val coroutineContext get() = Dispatchers.Default + job + CoroutineExceptionHandler { _, t -> printLog(t) } | ||
|
|
||
| override fun run() { | ||
| while (running) { | ||
| val packet = DatagramPacket(ByteArray(UDP_PACKET_SIZE), 0, UDP_PACKET_SIZE) | ||
| try { | ||
| socket.receive(packet) | ||
| launch(start = CoroutineStart.UNDISPATCHED) { | ||
| resolve(packet) // this method should also put the reply in the packet | ||
| socket.send(packet) | ||
| } | ||
| } catch (e: RuntimeException) { | ||
| e.printStackTrace() | ||
| } | ||
| } | ||
| } | ||
|
|
||
| private suspend fun <T> io(block: suspend CoroutineScope.() -> T) = | ||
| withTimeout(TIMEOUT) { withContext(Dispatchers.IO, block) } | ||
|
|
||
| private suspend fun resolve(packet: DatagramPacket) { | ||
| if (forwardOnly) return forward(packet) | ||
| val request = try { | ||
| Message(ByteBuffer.wrap(packet.data, packet.offset, packet.length)) | ||
| } catch (e: IOException) { | ||
| printLog(e) | ||
| return forward(packet) | ||
| } | ||
| if (request.header.opcode != Opcode.QUERY || request.header.rcode != Rcode.NOERROR) return forward(packet) | ||
| val question = request.question | ||
| if (question?.type != Type.A) return forward(packet) | ||
| val host = question.name.toString(true) | ||
| if (remoteDomainMatcher?.containsMatchIn(host) == true) return forward(packet) | ||
| val localResults = try { | ||
| io { localResolver(host) } | ||
| } catch (_: TimeoutCancellationException) { | ||
| return forward(packet) | ||
| } catch (_: UnknownHostException) { | ||
| return forward(packet) | ||
| } | ||
| if (localResults.isEmpty()) return forward(packet) | ||
| if (localIpMatcher.isEmpty() || localIpMatcher.any { subnet -> localResults.any(subnet::matches) }) { | ||
| Log.d("DNS", "$host (local) -> $localResults") | ||
| val response = Message(request.header.id) | ||
| response.header.setFlag(Flags.QR.toInt()) // this is a response | ||
| if (request.header.getFlag(Flags.RD.toInt())) response.header.setFlag(Flags.RD.toInt()) | ||
| response.header.setFlag(Flags.RA.toInt()) // recursion available | ||
| response.addRecord(request.question, Section.QUESTION) | ||
| for (address in localResults) response.addRecord(when (address) { | ||
| is Inet4Address -> ARecord(request.question.name, DClass.IN, TTL, address) | ||
| is Inet6Address -> AAAARecord(request.question.name, DClass.IN, TTL, address) | ||
| else -> throw IllegalStateException("Unsupported address $address") | ||
| }, Section.ANSWER) | ||
| val wire = response.toWire() | ||
| return packet.setData(wire, 0, wire.size) | ||
| } | ||
| return forward(packet) | ||
| } | ||
|
|
||
| private suspend fun forward(packet: DatagramPacket) = if (tcp) Socket(tcpProxy).useFd { | ||
| it.connect(InetSocketAddress(remoteDns, 53), 53) | ||
| it.getOutputStream().apply { | ||
| write(packet.data, packet.offset, packet.length) | ||
| flush() | ||
| } | ||
| val read = it.getInputStream().read(packet.data, 0, UDP_PACKET_SIZE) | ||
| packet.length = if (read < 0) 0 else read | ||
| } else Socks5DatagramSocket(udpProxy, 0, null).useFd { | ||
| val address = packet.address // we are reusing the packet, save it first | ||
| packet.address = remoteDns | ||
| packet.port = 53 | ||
| packet.toString() | ||
| Log.d("DNS", "Sending $packet") | ||
| it.send(packet) | ||
| Log.d("DNS", "Receiving $packet") | ||
| it.receive(packet) | ||
| Log.d("DNS", "Finished $packet") | ||
| packet.address = address | ||
| } | ||
|
|
||
| private suspend fun <T : Closeable> T.useFd(block: (T) -> Unit) { | ||
| val fd = when (this) { | ||
| is Socket -> ParcelFileDescriptor.fromSocket(this).fileDescriptor | ||
| is DatagramSocket -> fileDescriptor | ||
| else -> throw IllegalStateException("Unsupported type $javaClass for obtaining FileDescriptor") | ||
| } | ||
| try { | ||
| activeFds += fd | ||
| io { use(block) } | ||
| } finally { | ||
| fd.shutdown() | ||
| activeFds -= fd | ||
| } | ||
| } | ||
|
|
||
| suspend fun shutdown() { | ||
| running = false | ||
| job.cancel() | ||
| close() | ||
| activeFds.forEach { it.shutdown() } | ||
| job.join() | ||
| } | ||
| } |
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