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>

bootstrap/bungeecord/build.gradle.kts

@@ -22,6 +22,7 @@ tasks.withType<com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar> {
 
     dependencies {
         exclude(dependency("com.google.*:.*"))
+        exclude(dependency("io.netty.incubator:.*"))
         exclude(dependency("io.netty:netty-transport-native-epoll:.*"))
         exclude(dependency("io.netty:netty-transport-native-unix-common:.*"))
         exclude(dependency("io.netty:netty-handler:.*"))

bootstrap/spigot/build.gradle.kts

@@ -41,6 +41,7 @@ tasks.withType<com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar> {
 
         // We cannot shade Netty, or else native libraries will not load
         // Needed because older Spigot builds do not provide the haproxy module
+        exclude(dependency("io.netty.incubator:.*"))
         exclude(dependency("io.netty:netty-transport-classes-epoll:.*"))
         exclude(dependency("io.netty:netty-transport-native-epoll:.*"))
         exclude(dependency("io.netty:netty-transport-native-unix-common:.*"))

bootstrap/velocity/build.gradle.kts

@@ -12,7 +12,8 @@ platformRelocate("org.yaml")
 
 exclude("com.google.*:*")
 
-// Needed because Velocity provides every dependency except netty-resolver-dns 
+// Needed because Velocity provides every dependency except netty-resolver-dns
+exclude("io.netty.incubator:.*")
 exclude("io.netty:netty-transport-native-epoll:*")
 exclude("io.netty:netty-transport-native-unix-common:*")
 exclude("io.netty:netty-transport-native-kqueue:*")
@@ -57,6 +58,7 @@ tasks.withType<com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar> {
         exclude(dependency("io.netty:netty-transport:.*"))
         exclude(dependency("io.netty:netty-codec:.*"))
         exclude(dependency("io.netty:netty-codec-haproxy:.*"))
+        exclude(dependency("io.netty.incubator:.*"))
         exclude(dependency("org.slf4j:.*"))
         exclude(dependency("org.ow2.asm:.*"))
         // Exclude all Kyori dependencies except the legacy NBT serializer

bootstrap/viaproxy/build.gradle.kts

@@ -22,6 +22,7 @@ tasks.withType<com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar> {
     dependencies {
         exclude(dependency("com.google.*:.*"))
         exclude(dependency("io.netty:.*"))
+        exclude(dependency("io.netty.incubator:.*"))
         exclude(dependency("org.slf4j:.*"))
         exclude(dependency("org.ow2.asm:.*"))
     }

build-logic/src/main/kotlin/geyser.modded-conventions.gradle.kts

@@ -26,6 +26,8 @@ provided("io.netty", "netty-transport-native-epoll")
 provided("io.netty", "netty-transport-native-unix-common")
 provided("io.netty", "netty-transport-classes-kqueue")
 provided("io.netty", "netty-transport-native-kqueue")
+provided("io.netty.incubator", "netty-incubator-transport-native-io_uring")
+provided("io.netty.incubator", "netty-incubator-transport-classes-io_uring")
 provided("io.netty", "netty-handler")
 provided("io.netty", "netty-common")
 provided("io.netty", "netty-buffer")

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
+        // setup SO_REUSEPORT if exists - or, if the option does not actually exist, reset listen count
-        Bootstraps.setupBootstrap(this.bootstrap);
+        // 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 (isClassAvailable("io.netty.incubator.channel.uring.IOUring")
-        if (transportMethod == TransportHelper.TransportMethod.EPOLL) {
+                && 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;
+        }
+    }
 }

gradle/libs.versions.toml

@@ -6,6 +6,7 @@ events = "1.1-SNAPSHOT"
 jackson = "2.17.0"
 fastutil = "8.5.2"
 netty = "4.1.107.Final"
+netty-io-uring = "0.0.25.Final-SNAPSHOT"
 guava = "29.0-jre"
 gson = "2.3.1" # Provided by Spigot 1.8.8
 websocket = "1.5.1"
@@ -75,6 +76,7 @@ netty-codec-haproxy = { group = "io.netty", name = "netty-codec-haproxy", versio
 netty-handler = { group = "io.netty", name = "netty-handler", version.ref = "netty" }
 netty-transport-native-epoll = { group = "io.netty", name = "netty-transport-native-epoll", version.ref = "netty" }
 netty-transport-native-kqueue = { group = "io.netty", name = "netty-transport-native-kqueue", version.ref = "netty" }
+netty-transport-native-io_uring = { group = "io.netty.incubator", name = "netty-incubator-transport-native-io_uring", version.ref = "netty-io-uring" }
 
 log4j-api = { group = "org.apache.logging.log4j", name = "log4j-api", version.ref = "log4j" }
 log4j-core = { group = "org.apache.logging.log4j", name = "log4j-core", version.ref = "log4j" }