Electrum: add support for socks5 proxies (#1315)

We use the socks5 proxy that is defined in the configuration and is typically used to connect to LN nodes running as TOR hidden services.
This should allow users to connect to Electrum servers that are running behind TOR.

eclair-core/src/main/scala/fr/acinq/eclair/Setup.scala

@@ -200,7 +200,7 @@ class Setup(datadir: File,
           val stream = classOf[Setup].getResourceAsStream(addressesFile)
           ElectrumClientPool.readServerAddresses(stream, sslEnabled)
       }
-      val electrumClient = system.actorOf(SimpleSupervisor.props(Props(new ElectrumClientPool(blockCount, addresses)), "electrum-client", SupervisorStrategy.Resume))
+      val electrumClient = system.actorOf(SimpleSupervisor.props(Props(new ElectrumClientPool(blockCount, addresses, nodeParams.socksProxy_opt)), "electrum-client", SupervisorStrategy.Resume))
       Electrum(electrumClient)
   }
 

eclair-core/src/main/scala/fr/acinq/eclair/blockchain/electrum/ElectrumClient.scala

@@ -23,6 +23,7 @@ import akka.actor.{Actor, ActorLogging, ActorRef, Stash, Terminated}
 import fr.acinq.bitcoin._
 import fr.acinq.eclair.blockchain.bitcoind.rpc.{Error, JsonRPCRequest, JsonRPCResponse}
 import fr.acinq.eclair.blockchain.electrum.ElectrumClient.SSL
+import fr.acinq.eclair.tor.Socks5ProxyParams
 import io.netty.bootstrap.Bootstrap
 import io.netty.buffer.PooledByteBufAllocator
 import io.netty.channel._
@@ -31,8 +32,10 @@ import io.netty.channel.socket.SocketChannel
 import io.netty.channel.socket.nio.NioSocketChannel
 import io.netty.handler.codec.string.{LineEncoder, StringDecoder}
 import io.netty.handler.codec.{LineBasedFrameDecoder, MessageToMessageDecoder, MessageToMessageEncoder}
+import io.netty.handler.proxy.Socks5ProxyHandler
 import io.netty.handler.ssl.SslContextBuilder
 import io.netty.handler.ssl.util.InsecureTrustManagerFactory
+import io.netty.resolver.{NoopAddressResolver, NoopAddressResolverGroup}
 import io.netty.util.CharsetUtil
 import org.json4s.JsonAST._
 import org.json4s.jackson.JsonMethods
@@ -48,7 +51,7 @@ import scala.util.{Failure, Success, Try}
   * For later optimizations, see http://normanmaurer.me/presentations/2014-facebook-eng-netty/slides.html
   *
   */
-class ElectrumClient(serverAddress: InetSocketAddress, ssl: SSL)(implicit val ec: ExecutionContext) extends Actor with Stash with ActorLogging {
+class ElectrumClient(serverAddress: InetSocketAddress, ssl: SSL, socksProxy_opt: Option[Socks5ProxyParams] = None)(implicit val ec: ExecutionContext) extends Actor with Stash with ActorLogging {
 
   import ElectrumClient._
 
@@ -93,9 +96,14 @@ class ElectrumClient(serverAddress: InetSocketAddress, ssl: SSL)(implicit val ec
       ch.pipeline.addLast(new JsonRPCRequestEncoder)
       // error handler
       ch.pipeline.addLast(new ExceptionHandler)
+      // optional proxy (must be the first handler)
+      socksProxy_opt.foreach(params => ch.pipeline().addFirst(new Socks5ProxyHandler(params.address)))
     }
   })
 
+  // don't try to resolve addresses if we're using a proxy
+  socksProxy_opt.foreach(params => b.resolver(NoopAddressResolverGroup.INSTANCE))
+
   // Start the client.
   log.info("connecting to server={}", serverAddress)
 

eclair-core/src/main/scala/fr/acinq/eclair/blockchain/electrum/ElectrumClientPool.scala

@@ -25,14 +25,15 @@ import fr.acinq.bitcoin.BlockHeader
 import fr.acinq.eclair.blockchain.CurrentBlockCount
 import fr.acinq.eclair.blockchain.electrum.ElectrumClient.SSL
 import fr.acinq.eclair.blockchain.electrum.ElectrumClientPool.ElectrumServerAddress
+import fr.acinq.eclair.tor.Socks5ProxyParams
 import org.json4s.JsonAST.{JObject, JString}
 import org.json4s.jackson.JsonMethods
 
 import scala.concurrent.ExecutionContext
 import scala.concurrent.duration._
 import scala.util.Random
 
-class ElectrumClientPool(blockCount: AtomicLong, serverAddresses: Set[ElectrumServerAddress])(implicit val ec: ExecutionContext) extends Actor with FSM[ElectrumClientPool.State, ElectrumClientPool.Data] {
+class ElectrumClientPool(blockCount: AtomicLong, serverAddresses: Set[ElectrumServerAddress], socksProxy_opt: Option[Socks5ProxyParams] = None)(implicit val ec: ExecutionContext) extends Actor with FSM[ElectrumClientPool.State, ElectrumClientPool.Data] {
   import ElectrumClientPool._
 
   val statusListeners = collection.mutable.HashSet.empty[ActorRef]
@@ -112,7 +113,7 @@ class ElectrumClientPool(blockCount: AtomicLong, serverAddresses: Set[ElectrumSe
       pickAddress(serverAddresses, addresses.values.toSet) match {
         case Some(ElectrumServerAddress(address, ssl)) =>
           val resolved = new InetSocketAddress(address.getHostName, address.getPort)
-          val client = context.actorOf(Props(new ElectrumClient(resolved, ssl)))
+          val client = context.actorOf(Props(new ElectrumClient(resolved, ssl, socksProxy_opt)))
           client ! ElectrumClient.AddStatusListener(self)
           // we watch each electrum client, they will stop on disconnection
           context watch client