Enable tcp fast open by default if available

proxy/src/main/java/com/velocitypowered/proxy/config/VelocityConfiguration.java

@@ -30,6 +30,7 @@
 import com.velocitypowered.proxy.config.migration.ForwardingMigration;
 import com.velocitypowered.proxy.config.migration.KeyAuthenticationMigration;
 import com.velocitypowered.proxy.config.migration.MotdMigration;
+import com.velocitypowered.proxy.config.migration.TcpFastOpenMigration;
 import com.velocitypowered.proxy.util.AddressUtil;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import java.io.IOException;
@@ -456,7 +457,8 @@ public static VelocityConfiguration read(Path path) throws IOException {
       final ConfigurationMigration[] migrations = {
           new ForwardingMigration(),
           new KeyAuthenticationMigration(),
-          new MotdMigration()
+          new MotdMigration(),
+          new TcpFastOpenMigration()
       };
 
       for (final ConfigurationMigration migration : migrations) {
@@ -695,7 +697,7 @@ private static class Advanced {
     @Expose
     private boolean proxyProtocol = false;
     @Expose
-    private boolean tcpFastOpen = false;
+    private boolean tcpFastOpen = true;
     @Expose
     private boolean bungeePluginMessageChannel = true;
     @Expose
@@ -724,7 +726,7 @@ private Advanced(CommentedConfig config) {
         } else {
           this.proxyProtocol = config.getOrElse("proxy-protocol", false);
         }
-        this.tcpFastOpen = config.getOrElse("tcp-fast-open", false);
+        this.tcpFastOpen = config.getOrElse("tcp-fast-open", true);
         this.bungeePluginMessageChannel = config.getOrElse("bungee-plugin-message-channel", true);
         this.showPingRequests = config.getOrElse("show-ping-requests", false);
         this.failoverOnUnexpectedServerDisconnect = config

proxy/src/main/java/com/velocitypowered/proxy/config/migration/ConfigurationMigration.java

@@ -25,7 +25,7 @@
  * Configuration Migration interface.
  */
 public sealed interface ConfigurationMigration
-        permits ForwardingMigration, KeyAuthenticationMigration, MotdMigration {
+        permits ForwardingMigration, KeyAuthenticationMigration, MotdMigration, TcpFastOpenMigration {
   boolean shouldMigrate(CommentedFileConfig config);
 
   void migrate(CommentedFileConfig config, Logger logger) throws IOException;

proxy/src/main/java/com/velocitypowered/proxy/config/migration/TcpFastOpenMigration.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2023 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.config.migration;
+
+import com.electronwill.nightconfig.core.file.CommentedFileConfig;
+import org.apache.logging.log4j.Logger;
+
+/**
+ * Migrate TCP Fast Open to be enabled by default.
+ */
+public final class TcpFastOpenMigration implements ConfigurationMigration {
+  @Override
+  public boolean shouldMigrate(final CommentedFileConfig config) {
+    return configVersion(config) < 2.7;
+  }
+
+  @Override
+  public void migrate(final CommentedFileConfig config, final Logger logger) {
+    if (!config.getOrElse("advanced.tcp-fast-open", false)) {
+      config.set("advanced.tcp-fast-open", true);
+    }
+
+    config.setComment("advanced.tcp-fast-open", """
+            Enables TCP fast open support on the proxy.
+            Disabled automatically if not supported by the operating system.""");
+    config.set("config-version", "2.7");
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/network/ConnectionManager.java

@@ -100,7 +100,8 @@ public void bind(final InetSocketAddress address) {
         .childOption(ChannelOption.IP_TOS, 0x18)
         .localAddress(address);
 
-    if (server.getConfiguration().useTcpFastOpen()) {
+    if (server.getConfiguration().useTcpFastOpen()
+        && transportType.supportsTcpFastOpenServer()) {
       bootstrap.option(ChannelOption.TCP_FASTOPEN, 3);
     }
 
@@ -163,7 +164,8 @@ public Bootstrap createWorker(@Nullable EventLoopGroup group) {
             this.server.getConfiguration().getConnectTimeout())
         .group(group == null ? this.workerGroup : group)
         .resolver(this.resolver.asGroup());
-    if (server.getConfiguration().useTcpFastOpen()) {
+    if (server.getConfiguration().useTcpFastOpen()
+        && transportType.supportsTcpFastOpenClient()) {
       bootstrap.option(ChannelOption.TCP_FASTOPEN_CONNECT, true);
     }
     return bootstrap;

proxy/src/main/java/com/velocitypowered/proxy/network/TransportType.java

@@ -47,32 +47,44 @@ public enum TransportType {
   NIO("NIO", NioServerSocketChannel::new,
       NioSocketChannel::new,
       NioDatagramChannel::new,
-      (name, type) -> new NioEventLoopGroup(0, createThreadFactory(name, type))),
+      (name, type) -> new NioEventLoopGroup(0, createThreadFactory(name, type)),
+      false,
+      false),
   EPOLL("epoll", EpollServerSocketChannel::new,
       EpollSocketChannel::new,
       EpollDatagramChannel::new,
-      (name, type) -> new EpollEventLoopGroup(0, createThreadFactory(name, type))),
+      (name, type) -> new EpollEventLoopGroup(0, createThreadFactory(name, type)),
+      Epoll.isTcpFastOpenServerSideAvailable(),
+      Epoll.isTcpFastOpenClientSideAvailable()),
   KQUEUE("kqueue", KQueueServerSocketChannel::new,
       KQueueSocketChannel::new,
       KQueueDatagramChannel::new,
-      (name, type) -> new KQueueEventLoopGroup(0, createThreadFactory(name, type)));
+      (name, type) -> new KQueueEventLoopGroup(0, createThreadFactory(name, type)),
+      KQueue.isTcpFastOpenServerSideAvailable(),
+      KQueue.isTcpFastOpenClientSideAvailable());
 
   final String name;
   final ChannelFactory<? extends ServerSocketChannel> serverSocketChannelFactory;
   final ChannelFactory<? extends SocketChannel> socketChannelFactory;
   final ChannelFactory<? extends DatagramChannel> datagramChannelFactory;
   final BiFunction<String, Type, EventLoopGroup> eventLoopGroupFactory;
+  final boolean supportsTcpFastOpenServer;
+  final boolean supportsTcpFastOpenClient;
 
   TransportType(final String name,
       final ChannelFactory<? extends ServerSocketChannel> serverSocketChannelFactory,
       final ChannelFactory<? extends SocketChannel> socketChannelFactory,
       final ChannelFactory<? extends DatagramChannel> datagramChannelFactory,
-      final BiFunction<String, Type, EventLoopGroup> eventLoopGroupFactory) {
+      final BiFunction<String, Type, EventLoopGroup> eventLoopGroupFactory,
+      final boolean supportsTcpFastOpenServer,
+      final boolean supportsTcpFastOpenClient) {
     this.name = name;
     this.serverSocketChannelFactory = serverSocketChannelFactory;
     this.socketChannelFactory = socketChannelFactory;
     this.datagramChannelFactory = datagramChannelFactory;
     this.eventLoopGroupFactory = eventLoopGroupFactory;
+    this.supportsTcpFastOpenServer = supportsTcpFastOpenServer;
+    this.supportsTcpFastOpenClient = supportsTcpFastOpenClient;
   }
 
   @Override
@@ -84,6 +96,14 @@ public EventLoopGroup createEventLoopGroup(final Type type) {
     return this.eventLoopGroupFactory.apply(this.name, type);
   }
 
+  public boolean supportsTcpFastOpenServer() {
+    return supportsTcpFastOpenServer;
+  }
+
+  public boolean supportsTcpFastOpenClient() {
+    return supportsTcpFastOpenClient;
+  }
+
   private static ThreadFactory createThreadFactory(final String name, final Type type) {
     return new VelocityNettyThreadFactory("Netty " + name + ' ' + type.toString() + " #%d");
   }

proxy/src/main/resources/default-velocity.toml

@@ -1,5 +1,5 @@
 # Config version. Do not change this
-config-version = "2.6"
+config-version = "2.7"
 
 # What port should the proxy be bound to? By default, we'll bind to all addresses on port 25577.
 bind = "0.0.0.0:25577"
@@ -42,7 +42,7 @@ forwarding-secret-file = "forwarding.secret"
 
 # Announce whether or not your server supports Forge. If you run a modded server, we
 # suggest turning this on.
-# 
+#
 # If your network runs one modpack consistently, consider using ping-passthrough = "mods"
 # instead for a nicer display in the server list.
 announce-forge = false
@@ -116,8 +116,9 @@ read-timeout = 30000
 # don't enable it.
 haproxy-protocol = false
 
-# Enables TCP fast open support on the proxy. Requires the proxy to run on Linux.
-tcp-fast-open = false
+# Enables TCP fast open support on the proxy.
+# Disabled automatically if not supported by the operating system.
+tcp-fast-open = true
 
 # Enables BungeeCord plugin messaging channel support on Velocity.
 bungee-plugin-message-channel = true