477885 - Jetty HTTP2 client fails to connect with Netty server - HTTP2 client preface missing or corrupt.

Fixed by starting to read from the server only after having sent the
client preface.

jetty-http2/http2-client/src/main/java/org/eclipse/jetty/http2/client/HTTP2ClientConnectionFactory.java

@@ -102,7 +102,6 @@ public class HTTP2ClientConnectionFactory implements ClientConnectionFactory
         @Override
         public void onOpen()
         {
-            super.onOpen();
             Map<Integer, Integer> settings = listener.onPreface(getSession());
             if (settings == null)
                 settings = Collections.emptyMap();
@@ -120,6 +119,10 @@ public class HTTP2ClientConnectionFactory implements ClientConnectionFactory
             {
                 session.frames(null, this, prefaceFrame, settingsFrame);
             }
+            // Only start reading from server after we have sent the client preface,
+            // otherwise we risk to read the server preface (a SETTINGS frame) and
+            // reply to that before we have the chance to send the client preface.
+            super.onOpen();
         }
 
         @Override

jetty-http2/http2-client/src/test/java/org/eclipse/jetty/http2/client/PrefaceTest.java

@@ -0,0 +1,98 @@
+//
+//  ========================================================================
+//  Copyright (c) 1995-2015 Mort Bay Consulting Pty. Ltd.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
+package org.eclipse.jetty.http2.client;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.jetty.http.HttpFields;
+import org.eclipse.jetty.http.HttpVersion;
+import org.eclipse.jetty.http.MetaData;
+import org.eclipse.jetty.http2.api.Session;
+import org.eclipse.jetty.http2.api.Stream;
+import org.eclipse.jetty.http2.api.server.ServerSessionListener;
+import org.eclipse.jetty.http2.frames.HeadersFrame;
+import org.eclipse.jetty.http2.frames.SettingsFrame;
+import org.eclipse.jetty.util.Callback;
+import org.eclipse.jetty.util.Promise;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class PrefaceTest extends AbstractTest
+{
+    @Test
+    public void testServerPrefaceBeforeClientPreface() throws Exception
+    {
+        start(new ServerSessionListener.Adapter()
+        {
+            @Override
+            public void onAccept(Session session)
+            {
+                // Send the server preface from here.
+                session.settings(new SettingsFrame(new HashMap<>(), false), Callback.NOOP);
+            }
+
+            @Override
+            public Stream.Listener onNewStream(Stream stream, HeadersFrame frame)
+            {
+                MetaData.Response metaData = new MetaData.Response(HttpVersion.HTTP_2, 200, new HttpFields());
+                HeadersFrame responseFrame = new HeadersFrame(stream.getId(), metaData, null, true);
+                stream.headers(responseFrame, Callback.NOOP);
+                return null;
+            }
+        });
+
+        Session session = newClient(new Session.Listener.Adapter()
+        {
+            @Override
+            public Map<Integer, Integer> onPreface(Session session)
+            {
+                try
+                {
+                    // Wait for the server preface (a SETTINGS frame) to
+                    // arrive on the client, and for its reply to be sent.
+                    Thread.sleep(1000);
+                    return null;
+                }
+                catch (InterruptedException x)
+                {
+                    x.printStackTrace();
+                    return null;
+                }
+            }
+        });
+
+        CountDownLatch latch = new CountDownLatch(1);
+        MetaData.Request metaData = newRequest("GET", new HttpFields());
+        HeadersFrame requestFrame = new HeadersFrame(metaData, null, true);
+        session.newStream(requestFrame, new Promise.Adapter<>(), new Stream.Listener.Adapter()
+        {
+            @Override
+            public void onHeaders(Stream stream, HeadersFrame frame)
+            {
+                if (frame.isEndStream())
+                    latch.countDown();
+            }
+        });
+
+        Assert.assertTrue(latch.await(5, TimeUnit.SECONDS));
+    }
+}