From 434772930f362145516dd60681134e7f0cf8115b Mon Sep 17 00:00:00 2001
From: Mark Thomas <markt@apache.org>
Date: Tue, 1 Jul 2025 19:58:55 +0100
Subject: [PATCH] Apply the initial HTTP/2 connection limits earlier.

Origin: https://github.com/apache/tomcat/commit/434772930f362145516dd60681134e7f0cf8115b

---
 .../coyote/http2/ConnectionSettingsBase.java  | 19 +++++++++++++++++--
 .../coyote/http2/ConnectionSettingsLocal.java |  5 ++++-
 .../coyote/http2/Http2UpgradeHandler.java     |  8 ++++++--
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/java/org/apache/coyote/http2/ConnectionSettingsBase.java b/java/org/apache/coyote/http2/ConnectionSettingsBase.java
index 749fac5cff51..47141ba05018 100644
--- a/java/org/apache/coyote/http2/ConnectionSettingsBase.java
+++ b/java/org/apache/coyote/http2/ConnectionSettingsBase.java
@@ -66,6 +66,11 @@ abstract class ConnectionSettingsBase<T extends Throwable> {
 
 
     final void set(Setting setting, long value) throws T {
+        set(setting,  value, false);
+    }
+
+
+    final void set(Setting setting, long value, boolean force) throws T {
         if (log.isTraceEnabled()) {
             log.trace(sm.getString("connectionSettings.debug", connectionId, getEndpointName(), setting,
                     Long.toString(value)));
@@ -102,11 +107,21 @@ final void set(Setting setting, long value) throws T {
                 return;
         }
 
-        set(setting, Long.valueOf(value));
+        set(setting, Long.valueOf(value), force);
     }
 
 
-    synchronized void set(Setting setting, Long value) {
+    /**
+     * Specify a new value for setting with the option to force the change to take effect immediately rather than
+     * waiting until an {@code ACK} is received.
+     *
+     * @param setting The setting to update
+     * @param value   The new value for the setting
+     * @param force   {@code false} if an {@code ACK} must be received before the setting takes effect or {@code true}
+     *                    if the setting to take effect immediately. Even if the setting takes effect immediately, it
+     *                    will still be included in the next {@code SETTINGS} frame and an {@code ACK} will be expected.
+     */
+    synchronized void set(Setting setting, Long value, boolean force) {
         current.put(setting, value);
     }
 
diff --git a/java/org/apache/coyote/http2/ConnectionSettingsLocal.java b/java/org/apache/coyote/http2/ConnectionSettingsLocal.java
index 372be80223c9..5ceec8ece198 100644
--- a/java/org/apache/coyote/http2/ConnectionSettingsLocal.java
+++ b/java/org/apache/coyote/http2/ConnectionSettingsLocal.java
@@ -40,12 +40,15 @@ class ConnectionSettingsLocal extends ConnectionSettingsBase<IllegalArgumentExce
 
 
     @Override
-    final synchronized void set(Setting setting, Long value) {
+    final synchronized void set(Setting setting, Long value, boolean force) {
         checkSend();
         if (current.get(setting).longValue() == value.longValue()) {
             pending.remove(setting);
         } else {
             pending.put(setting, value);
+            if (force) {
+                current.put(setting, value);
+            }
         }
     }
 
diff --git a/java/org/apache/coyote/http2/Http2UpgradeHandler.java b/java/org/apache/coyote/http2/Http2UpgradeHandler.java
index 51bf38923856..234dd74f8ab8 100644
--- a/java/org/apache/coyote/http2/Http2UpgradeHandler.java
+++ b/java/org/apache/coyote/http2/Http2UpgradeHandler.java
@@ -161,8 +161,12 @@ class Http2UpgradeHandler extends AbstractStream implements InternalHttpUpgradeH
         remoteSettings = new ConnectionSettingsRemote(connectionId);
         localSettings = new ConnectionSettingsLocal(connectionId);
 
-        localSettings.set(Setting.MAX_CONCURRENT_STREAMS, protocol.getMaxConcurrentStreams());
-        localSettings.set(Setting.INITIAL_WINDOW_SIZE, protocol.getInitialWindowSize());
+        /*
+         * Force set these initial limits. A well-behaved client should ACK the settings and adhere to them before it
+         * reaches the limits anyway.
+         */
+        localSettings.set(Setting.MAX_CONCURRENT_STREAMS, protocol.getMaxConcurrentStreams(), true);
+        localSettings.set(Setting.INITIAL_WINDOW_SIZE, protocol.getInitialWindowSize(), true);
 
         pingManager.initiateDisabled = protocol.getInitiatePingDisabled();