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commit 69d7c0435c17444d5314da2d237e7468538e869a
Author: Mark Thomas <ma...@apache.org>
AuthorDate: Thu Sep 5 14:48:46 2019 +0100

    Keep connection flow control window consistent with initial window size.
    
    If the HTTP/2 connection requires an initial window size larger than the
    default, send a WINDOW_UPDATE to increase the flow control window for
    the connection so that the initial size of the flow control window for
    the connection is consistent with the increased value.
---
 .../coyote/http2/Http2AsyncUpgradeHandler.java     |  4 +--
 .../apache/coyote/http2/Http2UpgradeHandler.java   | 33 ++++++++++++++++++++++
 webapps/docs/changelog.xml                         |  6 ++++
 3 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/java/org/apache/coyote/http2/Http2AsyncUpgradeHandler.java 
b/java/org/apache/coyote/http2/Http2AsyncUpgradeHandler.java
index 92ad29c..545292f 100644
--- a/java/org/apache/coyote/http2/Http2AsyncUpgradeHandler.java
+++ b/java/org/apache/coyote/http2/Http2AsyncUpgradeHandler.java
@@ -105,10 +105,10 @@ public class Http2AsyncUpgradeHandler extends 
Http2UpgradeHandler {
 
     @Override
     protected void writeSettings() {
-        // Send the initial settings frame
         socketWrapper.write(BlockingMode.SEMI_BLOCK, 
protocol.getWriteTimeout(),
                 TimeUnit.MILLISECONDS, null, SocketWrapperBase.COMPLETE_WRITE, 
errorCompletion,
-                ByteBuffer.wrap(localSettings.getSettingsFrameForPending()));
+                ByteBuffer.wrap(localSettings.getSettingsFrameForPending()),
+                ByteBuffer.wrap(createWindowUpdateForSettings()));
         if (error != null) {
             String msg = sm.getString("upgradeHandler.sendPrefaceFail", 
connectionId);
             if (log.isDebugEnabled()) {
diff --git a/java/org/apache/coyote/http2/Http2UpgradeHandler.java 
b/java/org/apache/coyote/http2/Http2UpgradeHandler.java
index f395d10..9753ebc 100644
--- a/java/org/apache/coyote/http2/Http2UpgradeHandler.java
+++ b/java/org/apache/coyote/http2/Http2UpgradeHandler.java
@@ -560,11 +560,21 @@ class Http2UpgradeHandler extends AbstractStream 
implements InternalHttpUpgradeH
     }
 
 
+    /**
+     * Write the initial settings frame and any necessary supporting frames. If
+     * the initial settings increase the initial window size, it will also be
+     * necessary to send a WINDOW_UPDATE frame to increase the size of the flow
+     * control window for the connection (stream 0).
+     */
     protected void writeSettings() {
         // Send the initial settings frame
         try {
             byte[] settings = localSettings.getSettingsFrameForPending();
             socketWrapper.write(true, settings, 0, settings.length);
+            byte[] windowUpdateFrame = createWindowUpdateForSettings();
+            if (windowUpdateFrame.length > 0) {
+                socketWrapper.write(true,  windowUpdateFrame, 0 , 
windowUpdateFrame.length);
+            }
             socketWrapper.flush(true);
         } catch (IOException ioe) {
             String msg = sm.getString("upgradeHandler.sendPrefaceFail", 
connectionId);
@@ -576,6 +586,29 @@ class Http2UpgradeHandler extends AbstractStream 
implements InternalHttpUpgradeH
     }
 
 
+    /**
+     * @return  The WINDOW_UPDATE frame if one is required or an empty array if
+     *          no WINDOW_UPDATE is required.
+     */
+    protected byte[] createWindowUpdateForSettings() {
+        // Build a WINDOW_UPDATE frame if one is required. If not, create an
+        // empty byte array.
+        byte[] windowUpdateFrame;
+        int increment = protocol.getInitialWindowSize() - 
ConnectionSettingsBase.DEFAULT_INITIAL_WINDOW_SIZE;
+        if (increment > 0) {
+            // Build window update frame for stream 0
+            windowUpdateFrame = new byte[13];
+            ByteUtil.setThreeBytes(windowUpdateFrame, 0,  4);
+            windowUpdateFrame[3] = FrameType.WINDOW_UPDATE.getIdByte();
+            ByteUtil.set31Bits(windowUpdateFrame, 9, increment);
+        } else {
+            windowUpdateFrame = new byte[0];
+        }
+
+        return windowUpdateFrame;
+    }
+
+
     protected void writeGoAwayFrame(int maxStreamId, long errorCode, byte[] 
debugMsg)
             throws IOException {
         byte[] fixedPayload = new byte[8];
diff --git a/webapps/docs/changelog.xml b/webapps/docs/changelog.xml
index 6e907c9..b91c956 100644
--- a/webapps/docs/changelog.xml
+++ b/webapps/docs/changelog.xml
@@ -68,6 +68,12 @@
         <code>overheadDataThreshold</code> and
         <code>overheadWindowUpdateThreshold</code>. (markt)
       </fix>
+      <fix>
+        If the HTTP/2 connection requires an initial window size larger than 
the
+        default, send a WINDOW_UPDATE to increase the flow control window for 
the
+        connection so that the initial size of the flow control window for the
+        connection is consistent with the increased value. (markt)
+      </fix>
     </changelog>
   </subsection>
   <subsection name="Web applications">


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