From 38d8243dd9c67d35adf48f7467cefcd262ce9ea0 Mon Sep 17 00:00:00 2001
From: baranowb <baranowb@gmail.com>
Date: Thu, 10 Jul 2025 12:24:21 +0200
Subject: [PATCH] [UNDERTOW-2575] Add flush before socket close on write
 timeout

---
 .../undertow/conduits/WriteTimeoutStreamSinkConduit.java  | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/core/src/main/java/io/undertow/conduits/WriteTimeoutStreamSinkConduit.java b/core/src/main/java/io/undertow/conduits/WriteTimeoutStreamSinkConduit.java
index 8398c8b43c..5971041dd4 100644
--- a/core/src/main/java/io/undertow/conduits/WriteTimeoutStreamSinkConduit.java
+++ b/core/src/main/java/io/undertow/conduits/WriteTimeoutStreamSinkConduit.java
@@ -109,7 +109,15 @@ private void handleWriteTimeout(final long ret) throws IOException {
         long expireTimeVar = expireTime;
         if (expireTimeVar != -1 && currentTime > expireTimeVar) {
             this.expireTime = -1;
+            //shutdown write will call AbstractFramedStreamSinkConduit#queueCloseFrames. In some cases it will schedule
+            //additional packets to adhere to protocol, we need to flush content( this would happen later, if not for
+            //subsequent close
             connection.getSinkChannel().shutdownWrites();
+            try {
+                connection.getSinkChannel().flush();
+            } catch(IOException e) {
+                UndertowLogger.REQUEST_LOGGER.ioException(e);
+            }
             IoUtils.safeClose(connection);
             throw new ClosedChannelException();
         }