Fix: Properly check whether the so_reuseport socket option is available (#4579)

* Try to properly check if so_reuseport is available

* io_uring "support"

* comment out io_uring, for now

* Make IO_uring opt-in via `-DGeyser.io_uring=true` flag

* dont include io_uring

* oops - bungee 

editing on mobile is hard

* oops - spigot

* oops - velocity

* properly exclude all io_uring on all platforms except standalone

---------

Co-authored-by: Kas-tle <26531652+Kas-tle@users.noreply.github.com>

core/build.gradle.kts

@@ -47,6 +47,8 @@ dependencies {
     implementation(libs.netty.transport.native.epoll) { artifact { classifier = "linux-x86_64" } }
     implementation(libs.netty.transport.native.epoll) { artifact { classifier = "linux-aarch_64" } }
     implementation(libs.netty.transport.native.kqueue) { artifact { classifier = "osx-x86_64" } }
+    implementation(libs.netty.transport.native.io.uring) { artifact { classifier = "linux-x86_64" } }
+    implementation(libs.netty.transport.native.io.uring) { artifact { classifier = "linux-aarch_64" } }
 
     // Adventure text serialization
     api(libs.bundles.adventure)
@@ -66,11 +68,6 @@ dependencies {
     api(libs.events)
 }
 
-configurations.api {
-    // This is still experimental - additionally, it could only really benefit standalone
-    exclude(group = "io.netty.incubator", module = "netty-incubator-transport-native-io_uring")
-}
-
 tasks.processResources {
     // This is solely for backwards compatibility for other programs that used this file before the switch to gradle.
     // It used to be generated by the maven Git-Commit-Id-Plugin

core/src/main/java/org/geysermc/geyser/network/netty/Bootstraps.java

@@ -49,6 +49,7 @@ public final class Bootstraps {
         String kernelVersion;
         try {
             kernelVersion = Native.KERNEL_VERSION;
+            GeyserImpl.getInstance().getLogger().debug("Kernel version: " + kernelVersion);
         } catch (Throwable e) {
             GeyserImpl.getInstance().getLogger().debug("Could not determine kernel version! " + e.getMessage());
             kernelVersion = null;
@@ -67,10 +68,22 @@ public final class Bootstraps {
     }
 
     @SuppressWarnings({"rawtypes, unchecked"})
-    public static void setupBootstrap(AbstractBootstrap bootstrap) {
+    public static boolean setupBootstrap(AbstractBootstrap bootstrap) {
+        boolean success = true;
         if (REUSEPORT_AVAILABLE) {
-            bootstrap.option(UnixChannelOption.SO_REUSEPORT, true);
+            // Guessing whether so_reuseport is available based on kernel version is cool, but unreliable.
+            Channel channel = bootstrap.register().channel();
+            if (channel.config().setOption(UnixChannelOption.SO_REUSEPORT, true)) {
+                bootstrap.option(UnixChannelOption.SO_REUSEPORT, true);
+            } else {
+                // If this occurs, we guessed wrong and reuseport is not available
+                GeyserImpl.getInstance().getLogger().debug("so_reuseport is not available despite version being " + Native.KERNEL_VERSION);
+                success = false;
+            }
+            // Now yeet that channel
+            channel.close();
         }
+        return success;
     }
 
     private static int[] fromString(String input) {

core/src/main/java/org/geysermc/geyser/network/netty/GeyserServer.java

@@ -25,7 +25,6 @@
 
 package org.geysermc.geyser.network.netty;
 
-import com.github.steveice10.packetlib.helper.TransportHelper;
 import io.netty.bootstrap.ServerBootstrap;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
@@ -39,6 +38,9 @@ import io.netty.channel.kqueue.KQueueEventLoopGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.DatagramChannel;
 import io.netty.channel.socket.nio.NioDatagramChannel;
+import io.netty.incubator.channel.uring.IOUring;
+import io.netty.incubator.channel.uring.IOUringDatagramChannel;
+import io.netty.incubator.channel.uring.IOUringEventLoopGroup;
 import io.netty.util.concurrent.Future;
 import lombok.Getter;
 import net.jodah.expiringmap.ExpirationPolicy;
@@ -106,7 +108,7 @@ public final class GeyserServer {
 
     @Getter
     private final ExpiringMap<InetSocketAddress, InetSocketAddress> proxiedAddresses;
-    private final int listenCount;
+    private int listenCount;
 
     private ChannelFuture[] bootstrapFutures;
 
@@ -127,8 +129,11 @@ public final class GeyserServer {
         this.childGroup = TRANSPORT.eventLoopGroupFactory().apply(threadCount);
 
         this.bootstrap = this.createBootstrap();
-        // setup SO_REUSEPORT if exists
-        Bootstraps.setupBootstrap(this.bootstrap);
+        // setup SO_REUSEPORT if exists - or, if the option does not actually exist, reset listen count
+        // otherwise, we try to bind multiple times which wont work if so_reuseport is not valid
+        if (!Bootstraps.setupBootstrap(this.bootstrap)) {
+            this.listenCount = 1;
+        }
 
         if (this.geyser.getConfig().getBedrock().isEnableProxyProtocol()) {
             this.proxiedAddresses = ExpiringMap.builder()
@@ -415,22 +420,35 @@ public final class GeyserServer {
     }
 
     private static Transport compatibleTransport() {
-        TransportHelper.TransportMethod transportMethod = TransportHelper.determineTransportMethod();
-        if (transportMethod == TransportHelper.TransportMethod.EPOLL) {
+        if (isClassAvailable("io.netty.incubator.channel.uring.IOUring")
+                && IOUring.isAvailable()
+                && Boolean.parseBoolean(System.getProperty("Geyser.io_uring"))) {
+            return new Transport(IOUringDatagramChannel.class, IOUringEventLoopGroup::new);
+        }
+
+        if (isClassAvailable("io.netty.channel.epoll.Epoll") && Epoll.isAvailable()) {
             return new Transport(EpollDatagramChannel.class, EpollEventLoopGroup::new);
         }
 
-        if (transportMethod == TransportHelper.TransportMethod.KQUEUE) {
+        if (isClassAvailable("io.netty.channel.kqueue.KQueue") && KQueue.isAvailable()) {
             return new Transport(KQueueDatagramChannel.class, KQueueEventLoopGroup::new);
         }
 
-        // if (transportMethod == TransportHelper.TransportMethod.IO_URING) {
-        //     return new Transport(IOUringDatagramChannel.class, IOUringEventLoopGroup::new);
-        // }
-
         return new Transport(NioDatagramChannel.class, NioEventLoopGroup::new);
     }
 
     private record Transport(Class<? extends DatagramChannel> datagramChannel, IntFunction<EventLoopGroup> eventLoopGroupFactory) {
     }
+
+    /**
+     * Used so implementations can opt to remove these dependencies if so desired
+     */
+    private static boolean isClassAvailable(String className) {
+        try {
+            Class.forName(className);
+            return true;
+        } catch (ClassNotFoundException e) {
+            return false;
+        }
+    }
 }