Artery hostname for client side of TCP connection, #28546

akka-remote/src/main/resources/reference.conf

@@ -1087,6 +1087,9 @@ akka {
         tcp {
           # Timeout of establishing outbound connections.
           connection-timeout = 5 seconds
+
+          # The local address that is used for the client side of the TCP connection.
+          outbound-client-hostname = ""
         }
 
 

akka-remote/src/main/scala/akka/remote/artery/ArterySettings.scala

@@ -223,6 +223,12 @@ private[akka] final class ArterySettings private (config: Config) {
       val ConnectionTimeout: FiniteDuration = config
         .getMillisDuration("connection-timeout")
         .requiring(interval => interval > Duration.Zero, "connection-timeout must be more than zero")
+      val OutboundClientHostname: Option[String] = {
+        config.getString("outbound-client-hostname") match {
+          case ""       => None
+          case hostname => Some(hostname)
+        }
+      }
     }
 
   }

akka-remote/src/main/scala/akka/remote/artery/tcp/ArteryTcpTransport.scala

@@ -121,13 +121,17 @@ private[remote] class ArteryTcpTransport(
     val port = outboundContext.remoteAddress.port.get
     val remoteAddress = InetSocketAddress.createUnresolved(host, port)
 
-    def connectionFlow: Flow[ByteString, ByteString, Future[Tcp.OutgoingConnection]] =
+    def connectionFlow: Flow[ByteString, ByteString, Future[Tcp.OutgoingConnection]] = {
+      val localAddress = settings.Advanced.Tcp.OutboundClientHostname match {
+        case None                 => None
+        case Some(clientHostname) => Some(new InetSocketAddress(clientHostname, 0))
+      }
       if (tlsEnabled) {
         val sslProvider = sslEngineProvider.get
         Tcp().outgoingConnectionWithTls(
           remoteAddress,
           createSSLEngine = () => sslProvider.createClientSSLEngine(host, port),
-          localAddress = None,
+          localAddress,
           options = Nil,
           connectTimeout = settings.Advanced.Tcp.ConnectionTimeout,
           idleTimeout = Duration.Inf,
@@ -136,9 +140,11 @@ private[remote] class ArteryTcpTransport(
       } else {
         Tcp().outgoingConnection(
           remoteAddress,
+          localAddress,
           halfClose = true, // issue https://github.com/akka/akka/issues/24392 if set to false
           connectTimeout = settings.Advanced.Tcp.ConnectionTimeout)
       }
+    }
 
     def connectionFlowWithRestart: Flow[ByteString, ByteString, NotUsed] = {
       val restartCount = new AtomicInteger(0)