From b1685981dadff2c45e1e1f3df4f86ecb5f1d0f9c Mon Sep 17 00:00:00 2001
From: Volodymyr Sorokin <sorrro@gmail.com>
Date: Wed, 9 Oct 2024 15:03:17 +0300
Subject: [PATCH] Backport #7515 to 9.4 - Connection limit problem for
 "onAccepting" connections

* Backport for the PR #12320
  * Fixed `ManagedSelector.Accept` to emit the event "accept failed" when closed.
  * Fixed `ConnectionLimit` to close connections that exceed the maximum (may happen when the connector is configured with acceptors=0).
---
 .../org/eclipse/jetty/io/ManagedSelector.java | 19 ++++++++-----------
 .../eclipse/jetty/server/ConnectionLimit.java | 11 ++++++++---
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/jetty-io/src/main/java/org/eclipse/jetty/io/ManagedSelector.java b/jetty-io/src/main/java/org/eclipse/jetty/io/ManagedSelector.java
index b3b9b7326ff0..2b74c6979397 100644
--- a/jetty-io/src/main/java/org/eclipse/jetty/io/ManagedSelector.java
+++ b/jetty-io/src/main/java/org/eclipse/jetty/io/ManagedSelector.java
@@ -23,6 +23,7 @@
 import java.net.ConnectException;
 import java.net.SocketTimeoutException;
 import java.nio.channels.CancelledKeyException;
+import java.nio.channels.ClosedChannelException;
 import java.nio.channels.ClosedSelectorException;
 import java.nio.channels.SelectableChannel;
 import java.nio.channels.SelectionKey;
@@ -861,8 +862,8 @@ class Accept implements SelectorUpdate, Runnable, Closeable
         public void close()
         {
             if (LOG.isDebugEnabled())
-                LOG.debug("closed accept of {}", channel);
-            IO.close(channel);
+                LOG.debug("Closed accept of {}", channel);
+            failed(new ClosedChannelException());
         }
 
         @Override
@@ -875,10 +876,9 @@ public void update(Selector selector)
             }
             catch (Throwable x)
             {
-                IO.close(channel);
-                _selectorManager.onAcceptFailed(channel, x);
                 if (LOG.isDebugEnabled())
-                    LOG.debug(x);
+                    LOG.debug("Could not register channel after accept {}", channel, x);
+                failed(x);
             }
         }
 
@@ -887,23 +887,20 @@ public void run()
         {
             try
             {
-                createEndPoint(channel, key);
                 _selectorManager.onAccepted(channel);
+                createEndPoint(channel, key);
             }
             catch (Throwable x)
             {
                 if (LOG.isDebugEnabled())
-                    LOG.debug(x);
+                    LOG.debug("Could not process accepted channel {}", channel, x);
                 failed(x);
             }
         }
 
-        protected void failed(Throwable failure)
+        private void failed(Throwable failure)
         {
             IO.close(channel);
-            LOG.warn(String.valueOf(failure));
-            if (LOG.isDebugEnabled())
-                LOG.debug(failure);
             _selectorManager.onAcceptFailed(channel, failure);
         }
 
diff --git a/jetty-server/src/main/java/org/eclipse/jetty/server/ConnectionLimit.java b/jetty-server/src/main/java/org/eclipse/jetty/server/ConnectionLimit.java
index a6bd5ddd49e5..b08867481449 100644
--- a/jetty-server/src/main/java/org/eclipse/jetty/server/ConnectionLimit.java
+++ b/jetty-server/src/main/java/org/eclipse/jetty/server/ConnectionLimit.java
@@ -28,6 +28,7 @@
 import org.eclipse.jetty.io.Connection.Listener;
 import org.eclipse.jetty.io.EndPoint;
 import org.eclipse.jetty.io.SelectorManager;
+import org.eclipse.jetty.util.IO;
 import org.eclipse.jetty.util.annotation.ManagedAttribute;
 import org.eclipse.jetty.util.annotation.ManagedObject;
 import org.eclipse.jetty.util.annotation.Name;
@@ -172,9 +173,10 @@ protected void doStop() throws Exception
         }
     }
 
-    protected void check()
+    protected boolean check()
     {
-        if ((_accepting.size() + _connections) >= _maxConnections)
+        int total = _accepting.size() + _connections;
+        if (total >= _maxConnections)
         {
             if (!_limiting)
             {
@@ -182,6 +184,7 @@ protected void check()
                 LOG.info("Connection Limit({}) reached for {}", _maxConnections, _connectors);
                 limit();
             }
+            return total > _maxConnections;
         }
         else
         {
@@ -191,6 +194,7 @@ protected void check()
                 LOG.info("Connection Limit({}) cleared for {}", _maxConnections, _connectors);
                 unlimit();
             }
+            return false;
         }
     }
 
@@ -234,7 +238,8 @@ public void onAccepting(SelectableChannel channel)
             _accepting.add(channel);
             if (LOG.isDebugEnabled())
                 LOG.debug("onAccepting ({}+{}) < {} {}", _accepting.size(), _connections, _maxConnections, channel);
-            check();
+            if (check())
+                IO.close(channel);
         }
     }