Merge branch 'dev/1.1.0' into bungeequack-integrate

.gitignore

@@ -87,5 +87,5 @@ run/
 plugins/
 
 ### Natives stuff ###
-natives/mbedtls
-natives/zlib-ng
+native/mbedtls
+native/zlib-ng

.travis.yml

@@ -8,3 +8,4 @@ cache:
   - $HOME/.gradle/wrapper/
 jdk:
   - openjdk8
+  - openjdk11

api/build.gradle

@@ -73,6 +73,9 @@ javadoc {
 
     // Disable the crazy super-strict doclint tool in Java 8
     options.addStringOption('Xdoclint:none', '-quiet')
+    
+    // Mark sources as Java 8 source compatible
+    options.source = '8'
 }
 
 publishing {

api/src/main/java/com/velocitypowered/api/event/player/KickedFromServerEvent.java

@@ -147,10 +147,12 @@ public final class KickedFromServerEvent implements
    */
   public static final class RedirectPlayer implements ServerKickResult {
 
+    private final Component message;
     private final RegisteredServer server;
 
-    private RedirectPlayer(RegisteredServer server) {
+    private RedirectPlayer(RegisteredServer server, @Nullable Component message) {
       this.server = Preconditions.checkNotNull(server, "server");
+      this.message = message;
     }
 
     @Override
@@ -162,14 +164,23 @@ public final class KickedFromServerEvent implements
       return server;
     }
 
+    @Nullable
+    public Component getMessage() {
+      return message;
+    }
+
     /**
      * Creates a new redirect result to forward the player to the specified {@code server}.
      *
      * @param server the server to send the player to
      * @return the redirect result
      */
-    public static RedirectPlayer create(RegisteredServer server) {
-      return new RedirectPlayer(server);
+    public static RedirectPlayer create(RegisteredServer server, @Nullable Component message) {
+      return new RedirectPlayer(server, message);
+    }
+
+    public static ServerKickResult create(RegisteredServer server) {
+      return create(server, null);
     }
   }
 

api/src/main/java/com/velocitypowered/api/event/player/PlayerChooseInitialServerEvent.java

@@ -0,0 +1,51 @@
+package com.velocitypowered.api.event.player;
+
+import com.google.common.base.Preconditions;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.server.RegisteredServer;
+import java.util.Optional;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * Fired when a player has finished connecting to the proxy and we need to choose the first server
+ * to connect to.
+ */
+public class PlayerChooseInitialServerEvent {
+
+  private final Player player;
+  private @Nullable RegisteredServer initialServer;
+
+  /**
+   * Constructs a PlayerChooseInitialServerEvent.
+   * @param player the player that was connected
+   * @param initialServer the initial server selected, may be {@code null}
+   */
+  public PlayerChooseInitialServerEvent(Player player, @Nullable RegisteredServer initialServer) {
+    this.player = Preconditions.checkNotNull(player, "player");
+    this.initialServer = initialServer;
+  }
+
+  public Player getPlayer() {
+    return player;
+  }
+
+  public Optional<RegisteredServer> getInitialServer() {
+    return Optional.ofNullable(initialServer);
+  }
+
+  /**
+   * Sets the new initial server.
+   * @param server the initial server the player should connect to
+   */
+  public void setInitialServer(RegisteredServer server) {
+    this.initialServer = server;
+  }
+
+  @Override
+  public String toString() {
+    return "PlayerChooseInitialServerEvent{"
+        + "player=" + player
+        + ", initialServer=" + initialServer
+        + '}';
+  }
+}

api/src/main/java/com/velocitypowered/api/event/player/ServerConnectedEvent.java

@@ -3,6 +3,8 @@ package com.velocitypowered.api.event.player;
 import com.google.common.base.Preconditions;
 import com.velocitypowered.api.proxy.Player;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
+import java.util.Optional;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
  * This event is fired once the player has successfully connected to the target server and the
@@ -12,10 +14,24 @@ public final class ServerConnectedEvent {
 
   private final Player player;
   private final RegisteredServer server;
+  private final @Nullable RegisteredServer previousServer;
 
-  public ServerConnectedEvent(Player player, RegisteredServer server) {
+  /**
+   * Constructs a ServerConnectedEvent.
+   * @param player the player that was connected
+   * @param server the server the player was connected to
+   * @param previousServer the server the player was previously connected to, null if none
+   */
+  public ServerConnectedEvent(Player player, RegisteredServer server,
+      @Nullable RegisteredServer previousServer) {
     this.player = Preconditions.checkNotNull(player, "player");
     this.server = Preconditions.checkNotNull(server, "server");
+    this.previousServer = previousServer;
+  }
+
+  @Deprecated
+  public ServerConnectedEvent(Player player, RegisteredServer server) {
+    this(player, server, null);
   }
 
   public Player getPlayer() {
@@ -26,11 +42,16 @@ public final class ServerConnectedEvent {
     return server;
   }
 
+  public Optional<RegisteredServer> getPreviousServer() {
+    return Optional.ofNullable(previousServer);
+  }
+
   @Override
   public String toString() {
     return "ServerConnectedEvent{"
         + "player=" + player
         + ", server=" + server
+        + ", previousServer=" + previousServer
         + '}';
   }
 }

api/src/main/java/com/velocitypowered/api/network/ProtocolVersion.java

@@ -33,7 +33,8 @@ public enum ProtocolVersion {
   MINECRAFT_1_14_1(480, "1.14.1"),
   MINECRAFT_1_14_2(485, "1.14.2"),
   MINECRAFT_1_14_3(490, "1.14.3"),
-  MINECRAFT_1_14_4(498, "1.14.4");
+  MINECRAFT_1_14_4(498, "1.14.4"),
+  MINECRAFT_1_15(566, "1.15-pre2");
 
   private final int protocol;
   private final String name;

api/src/main/java/com/velocitypowered/api/util/FastUuidSansHyphens.java

@@ -0,0 +1,195 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Jon Chambers
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.velocitypowered.api.util;
+
+import java.util.UUID;
+
+/**
+ * This is a modified FastUUID implementation. The primary difference is that it does not dash its
+ * UUIDs. As the native Java 9+ UUID.toString() implementation dashes its UUIDs, we use the FastUUID
+ * internal method, which ought to be faster than a String.replace().
+ */
+class FastUuidSansHyphens {
+
+  private static final int MOJANG_BROKEN_UUID_LENGTH = 32;
+
+  private static final char[] HEX_DIGITS =
+      new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
+
+  private static final long[] HEX_VALUES = new long[128];
+
+  static {
+    for (int i = 0; i < HEX_VALUES.length; i++) {
+      HEX_VALUES[i] = -1;
+    }
+
+    HEX_VALUES['0'] = 0x0;
+    HEX_VALUES['1'] = 0x1;
+    HEX_VALUES['2'] = 0x2;
+    HEX_VALUES['3'] = 0x3;
+    HEX_VALUES['4'] = 0x4;
+    HEX_VALUES['5'] = 0x5;
+    HEX_VALUES['6'] = 0x6;
+    HEX_VALUES['7'] = 0x7;
+    HEX_VALUES['8'] = 0x8;
+    HEX_VALUES['9'] = 0x9;
+
+    HEX_VALUES['a'] = 0xa;
+    HEX_VALUES['b'] = 0xb;
+    HEX_VALUES['c'] = 0xc;
+    HEX_VALUES['d'] = 0xd;
+    HEX_VALUES['e'] = 0xe;
+    HEX_VALUES['f'] = 0xf;
+
+    HEX_VALUES['A'] = 0xa;
+    HEX_VALUES['B'] = 0xb;
+    HEX_VALUES['C'] = 0xc;
+    HEX_VALUES['D'] = 0xd;
+    HEX_VALUES['E'] = 0xe;
+    HEX_VALUES['F'] = 0xf;
+  }
+
+  private FastUuidSansHyphens() {
+    // A private constructor prevents callers from accidentally instantiating FastUUID instances
+  }
+
+  /**
+   * Parses a UUID from the given character sequence. The character sequence must represent a
+   * Mojang UUID.
+   *
+   * @param uuidSequence the character sequence from which to parse a UUID
+   *
+   * @return the UUID represented by the given character sequence
+   *
+   * @throws IllegalArgumentException if the given character sequence does not conform to the string
+   *         representation of a Mojang UUID.
+   */
+  static UUID parseUuid(final CharSequence uuidSequence) {
+    if (uuidSequence.length() != MOJANG_BROKEN_UUID_LENGTH) {
+      throw new IllegalArgumentException("Illegal UUID string: " + uuidSequence);
+    }
+
+    long mostSignificantBits = getHexValueForChar(uuidSequence.charAt(0)) << 60;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(1)) << 56;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(2)) << 52;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(3)) << 48;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(4)) << 44;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(5)) << 40;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(6)) << 36;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(7)) << 32;
+
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(8)) << 28;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(9)) << 24;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(10)) << 20;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(11)) << 16;
+
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(12)) << 12;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(13)) << 8;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(14)) << 4;
+    mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(15));
+
+    long leastSignificantBits = getHexValueForChar(uuidSequence.charAt(16)) << 60;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(17)) << 56;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(18)) << 52;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(19)) << 48;
+
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(20)) << 44;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(21)) << 40;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(22)) << 36;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(23)) << 32;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(24)) << 28;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(25)) << 24;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(26)) << 20;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(27)) << 16;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(28)) << 12;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(29)) << 8;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(30)) << 4;
+    leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(31));
+
+    return new UUID(mostSignificantBits, leastSignificantBits);
+  }
+
+  /**
+   * Returns a string representation of the given UUID. The returned string is formatted as a
+   * Mojang-style UUID.
+   *
+   * @param uuid the UUID to represent as a string
+   *
+   * @return a string representation of the given UUID
+   */
+  public static String toString(final UUID uuid) {
+    final long mostSignificantBits = uuid.getMostSignificantBits();
+    final long leastSignificantBits = uuid.getLeastSignificantBits();
+
+    final char[] uuidChars = new char[MOJANG_BROKEN_UUID_LENGTH];
+
+    uuidChars[0]  = HEX_DIGITS[(int) ((mostSignificantBits & 0xf000000000000000L) >>> 60)];
+    uuidChars[1]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x0f00000000000000L) >>> 56)];
+    uuidChars[2]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x00f0000000000000L) >>> 52)];
+    uuidChars[3]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x000f000000000000L) >>> 48)];
+    uuidChars[4]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x0000f00000000000L) >>> 44)];
+    uuidChars[5]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x00000f0000000000L) >>> 40)];
+    uuidChars[6]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x000000f000000000L) >>> 36)];
+    uuidChars[7]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x0000000f00000000L) >>> 32)];
+    uuidChars[8]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x00000000f0000000L) >>> 28)];
+    uuidChars[9]  = HEX_DIGITS[(int) ((mostSignificantBits & 0x000000000f000000L) >>> 24)];
+    uuidChars[10] = HEX_DIGITS[(int) ((mostSignificantBits & 0x0000000000f00000L) >>> 20)];
+    uuidChars[11] = HEX_DIGITS[(int) ((mostSignificantBits & 0x00000000000f0000L) >>> 16)];
+    uuidChars[12] = HEX_DIGITS[(int) ((mostSignificantBits & 0x000000000000f000L) >>> 12)];
+    uuidChars[13] = HEX_DIGITS[(int) ((mostSignificantBits & 0x0000000000000f00L) >>> 8)];
+    uuidChars[14] = HEX_DIGITS[(int) ((mostSignificantBits & 0x00000000000000f0L) >>> 4)];
+    uuidChars[15] = HEX_DIGITS[(int)  (mostSignificantBits & 0x000000000000000fL)];
+    uuidChars[16] = HEX_DIGITS[(int) ((leastSignificantBits & 0xf000000000000000L) >>> 60)];
+    uuidChars[17] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0f00000000000000L) >>> 56)];
+    uuidChars[18] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00f0000000000000L) >>> 52)];
+    uuidChars[19] = HEX_DIGITS[(int) ((leastSignificantBits & 0x000f000000000000L) >>> 48)];
+    uuidChars[20] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0000f00000000000L) >>> 44)];
+    uuidChars[21] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00000f0000000000L) >>> 40)];
+    uuidChars[22] = HEX_DIGITS[(int) ((leastSignificantBits & 0x000000f000000000L) >>> 36)];
+    uuidChars[23] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0000000f00000000L) >>> 32)];
+    uuidChars[24] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00000000f0000000L) >>> 28)];
+    uuidChars[25] = HEX_DIGITS[(int) ((leastSignificantBits & 0x000000000f000000L) >>> 24)];
+    uuidChars[26] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0000000000f00000L) >>> 20)];
+    uuidChars[27] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00000000000f0000L) >>> 16)];
+    uuidChars[28] = HEX_DIGITS[(int) ((leastSignificantBits & 0x000000000000f000L) >>> 12)];
+    uuidChars[29] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0000000000000f00L) >>> 8)];
+    uuidChars[30] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00000000000000f0L) >>> 4)];
+    uuidChars[31] = HEX_DIGITS[(int)  (leastSignificantBits & 0x000000000000000fL)];
+
+    return new String(uuidChars);
+  }
+
+  private static long getHexValueForChar(final char c) {
+    try {
+      if (HEX_VALUES[c] < 0) {
+        throw new IllegalArgumentException("Illegal hexadecimal digit: " + c);
+      }
+    } catch (final ArrayIndexOutOfBoundsException e) {
+      throw new IllegalArgumentException("Illegal hexadecimal digit: " + c);
+    }
+
+    return HEX_VALUES[c];
+  }
+}

api/src/main/java/com/velocitypowered/api/util/UuidUtils.java

@@ -1,7 +1,6 @@
 package com.velocitypowered.api.util;
 
 import com.google.common.base.Preconditions;
-import com.google.common.base.Strings;
 import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 import java.util.UUID;
@@ -23,11 +22,7 @@ public final class UuidUtils {
    */
   public static UUID fromUndashed(final String string) {
     Objects.requireNonNull(string, "string");
-    Preconditions.checkArgument(string.length() == 32, "Length is incorrect");
-    return new UUID(
-        Long.parseUnsignedLong(string.substring(0, 16), 16),
-        Long.parseUnsignedLong(string.substring(16), 16)
-    );
+    return FastUuidSansHyphens.parseUuid(string);
   }
 
   /**
@@ -38,10 +33,7 @@ public final class UuidUtils {
    */
   public static String toUndashed(final UUID uuid) {
     Preconditions.checkNotNull(uuid, "uuid");
-    String msbStr = Long.toHexString(uuid.getMostSignificantBits());
-    String lsbStr = Long.toHexString(uuid.getLeastSignificantBits());
-    return Strings.padStart(msbStr, 16, '0') + Strings.padStart(lsbStr,
-        16, '0');
+    return FastUuidSansHyphens.toString(uuid);
   }
 
   /**

build.gradle

@@ -24,7 +24,7 @@ allprojects {
         junitVersion = '5.3.0-M1'
         slf4jVersion = '1.7.25'
         log4jVersion = '2.11.2'
-        nettyVersion = '4.1.38.Final'
+        nettyVersion = '4.1.43.Final'
         guavaVersion = '25.1-jre'
         checkerFrameworkVersion = '2.7.0'
         configurateVersion = '3.6'

native/src/main/java/com/velocitypowered/natives/Native.java

@@ -1,5 +1,7 @@
 package com.velocitypowered.natives;
 
+import com.velocitypowered.natives.util.BufferPreference;
+
 public interface Native {
-  boolean isNative();
+  BufferPreference preferredBufferType();
 }

native/src/main/java/com/velocitypowered/natives/compression/Java11VelocityCompressor.java

@@ -0,0 +1,139 @@
+package com.velocitypowered.natives.compression;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkState;
+import static com.velocitypowered.natives.compression.CompressorUtils.ZLIB_BUFFER_SIZE;
+import static com.velocitypowered.natives.compression.CompressorUtils.ensureMaxSize;
+
+import com.velocitypowered.natives.util.BufferPreference;
+import io.netty.buffer.ByteBuf;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.nio.ByteBuffer;
+import java.util.zip.DataFormatException;
+import java.util.zip.Deflater;
+import java.util.zip.Inflater;
+
+public class Java11VelocityCompressor implements VelocityCompressor {
+
+  public static final VelocityCompressorFactory FACTORY = Java11VelocityCompressor::new;
+
+  // The use of MethodHandle is intentional. Velocity targets Java 8, and these methods don't exist
+  // in Java 8. This was also the most performant solution I could find, only slightly slower than a
+  // direct method call without long warmup times, requiring bytecode generation through ASM, or
+  // other stuff.
+  private static final MethodHandle DEFLATE_SET_INPUT;
+  private static final MethodHandle INFLATE_SET_INPUT;
+  private static final MethodHandle DEFLATE_CALL;
+  private static final MethodHandle INFLATE_CALL;
+
+  static {
+    try {
+      DEFLATE_SET_INPUT = MethodHandles.lookup().findVirtual(Deflater.class, "setInput",
+          MethodType.methodType(void.class, ByteBuffer.class));
+      INFLATE_SET_INPUT = MethodHandles.lookup().findVirtual(Inflater.class, "setInput",
+          MethodType.methodType(void.class, ByteBuffer.class));
+
+      DEFLATE_CALL = MethodHandles.lookup().findVirtual(Deflater.class, "deflate",
+          MethodType.methodType(int.class, ByteBuffer.class));
+      INFLATE_CALL = MethodHandles.lookup().findVirtual(Inflater.class, "inflate",
+          MethodType.methodType(int.class, ByteBuffer.class));
+    } catch (NoSuchMethodException | IllegalAccessException e) {
+      throw new AssertionError("Can't use Java 11 compressor on your version of Java");
+    }
+  }
+
+  private final Deflater deflater;
+  private final Inflater inflater;
+  private boolean disposed = false;
+
+  private Java11VelocityCompressor(int level) {
+    this.deflater = new Deflater(level);
+    this.inflater = new Inflater();
+  }
+
+  @Override
+  public void inflate(ByteBuf source, ByteBuf destination, int max) throws DataFormatException {
+    ensureNotDisposed();
+
+    // We (probably) can't nicely deal with >=1 buffer nicely, so let's scream loudly.
+    checkArgument(source.nioBufferCount() == 1, "source has multiple backing buffers");
+    checkArgument(destination.nioBufferCount() == 1, "destination has multiple backing buffers");
+
+    try {
+      int origIdx = source.readerIndex();
+      INFLATE_SET_INPUT.invokeExact(inflater, source.nioBuffer());
+
+      while (!inflater.finished() && inflater.getBytesRead() < source.readableBytes()) {
+        if (!destination.isWritable()) {
+          ensureMaxSize(destination, max);
+          destination.ensureWritable(ZLIB_BUFFER_SIZE);
+        }
+
+        ByteBuffer destNioBuf = destination.nioBuffer(destination.writerIndex(),
+            destination.writableBytes());
+        int produced = (int) INFLATE_CALL.invokeExact(inflater, destNioBuf);
+        source.readerIndex(origIdx + inflater.getTotalIn());
+        destination.writerIndex(destination.writerIndex() + produced);
+      }
+
+      inflater.reset();
+    } catch (Throwable e) {
+      if (e instanceof DataFormatException) {
+        throw (DataFormatException) e;
+      }
+      throw new RuntimeException(e);
+    }
+  }
+
+  @Override
+  public void deflate(ByteBuf source, ByteBuf destination) throws DataFormatException {
+    ensureNotDisposed();
+
+    // We (probably) can't nicely deal with >=1 buffer nicely, so let's scream loudly.
+    checkArgument(source.nioBufferCount() == 1, "source has multiple backing buffers");
+    checkArgument(destination.nioBufferCount() == 1, "destination has multiple backing buffers");
+
+    try {
+      int origIdx = source.readerIndex();
+      DEFLATE_SET_INPUT.invokeExact(deflater, source.nioBuffer());
+      deflater.finish();
+
+      while (!deflater.finished()) {
+        if (!destination.isWritable()) {
+          destination.ensureWritable(ZLIB_BUFFER_SIZE);
+        }
+
+        ByteBuffer destNioBuf = destination.nioBuffer(destination.writerIndex(),
+            destination.writableBytes());
+        int produced = (int) DEFLATE_CALL.invokeExact(deflater, destNioBuf);
+        source.readerIndex(origIdx + deflater.getTotalIn());
+        destination.writerIndex(destination.writerIndex() + produced);
+      }
+
+      deflater.reset();
+    } catch (Throwable e) {
+      if (e instanceof DataFormatException) {
+        throw (DataFormatException) e;
+      }
+      throw new RuntimeException(e);
+    }
+  }
+
+  @Override
+  public void dispose() {
+    disposed = true;
+    deflater.end();
+    inflater.end();
+  }
+
+  private void ensureNotDisposed() {
+    checkState(!disposed, "Object already disposed");
+  }
+
+  @Override
+  public BufferPreference preferredBufferType() {
+    return BufferPreference.DIRECT_PREFERRED;
+  }
+}

native/src/main/java/com/velocitypowered/natives/compression/JavaVelocityCompressor.java

@@ -4,6 +4,7 @@ import static com.velocitypowered.natives.compression.CompressorUtils.ZLIB_BUFFE
 import static com.velocitypowered.natives.compression.CompressorUtils.ensureMaxSize;
 
 import com.google.common.base.Preconditions;
+import com.velocitypowered.natives.util.BufferPreference;
 import io.netty.buffer.ByteBuf;
 import java.util.zip.DataFormatException;
 import java.util.zip.Deflater;
@@ -15,19 +16,37 @@ public class JavaVelocityCompressor implements VelocityCompressor {
 
   private final Deflater deflater;
   private final Inflater inflater;
-  private final byte[] buf;
+  private byte[] buf = new byte[0];
   private boolean disposed = false;
 
   private JavaVelocityCompressor(int level) {
     this.deflater = new Deflater(level);
     this.inflater = new Inflater();
-    this.buf = new byte[ZLIB_BUFFER_SIZE];
   }
 
   @Override
   public void inflate(ByteBuf source, ByteBuf destination, int max) throws DataFormatException {
     ensureNotDisposed();
 
+    final int available = source.readableBytes();
+    this.setInflaterInput(source);
+
+    if (destination.hasArray()) {
+      this.inflateDestinationIsHeap(destination, available, max);
+    } else {
+      if (buf.length == 0) {
+        buf = new byte[ZLIB_BUFFER_SIZE];
+      }
+      while (!inflater.finished() && inflater.getBytesRead() < available) {
+        ensureMaxSize(destination, max);
+        int read = inflater.inflate(buf);
+        destination.writeBytes(buf, 0, read);
+      }
+    }
+    inflater.reset();
+  }
+
+  private void setInflaterInput(ByteBuf source) {
     final int available = source.readableBytes();
     if (source.hasArray()) {
       inflater.setInput(source.array(), source.arrayOffset() + source.readerIndex(), available);
@@ -36,19 +55,45 @@ public class JavaVelocityCompressor implements VelocityCompressor {
       source.readBytes(inData);
       inflater.setInput(inData);
     }
-
-    while (!inflater.finished() && inflater.getBytesRead() < available) {
-      ensureMaxSize(destination, max);
-      int read = inflater.inflate(buf);
-      destination.writeBytes(buf, 0, read);
   }
-    inflater.reset();
+
+  private void inflateDestinationIsHeap(ByteBuf destination, int available, int max)
+      throws DataFormatException {
+    while (!inflater.finished() && inflater.getBytesRead() < available) {
+      if (!destination.isWritable()) {
+        ensureMaxSize(destination, max);
+        destination.ensureWritable(ZLIB_BUFFER_SIZE);
+      }
+
+      ensureMaxSize(destination, max);
+      int produced = inflater.inflate(destination.array(), destination.arrayOffset()
+          + destination.writerIndex(), destination.writableBytes());
+      destination.writerIndex(destination.writerIndex() + produced);
+    }
   }
 
   @Override
   public void deflate(ByteBuf source, ByteBuf destination) throws DataFormatException {
     ensureNotDisposed();
 
+    this.setDeflaterInput(source);
+    deflater.finish();
+
+    if (destination.hasArray()) {
+      this.deflateDestinationIsHeap(destination);
+    } else {
+      if (buf.length == 0) {
+        buf = new byte[ZLIB_BUFFER_SIZE];
+      }
+      while (!deflater.finished()) {
+        int bytes = deflater.deflate(buf);
+        destination.writeBytes(buf, 0, bytes);
+      }
+    }
+    deflater.reset();
+  }
+
+  private void setDeflaterInput(ByteBuf source) {
     if (source.hasArray()) {
       deflater.setInput(source.array(), source.arrayOffset() + source.readerIndex(),
           source.readableBytes());
@@ -57,12 +102,18 @@ public class JavaVelocityCompressor implements VelocityCompressor {
       source.readBytes(inData);
       deflater.setInput(inData);
     }
-    deflater.finish();
-    while (!deflater.finished()) {
-      int bytes = deflater.deflate(buf);
-      destination.writeBytes(buf, 0, bytes);
   }
-    deflater.reset();
+
+  private void deflateDestinationIsHeap(ByteBuf destination) {
+    while (!deflater.finished()) {
+      if (!destination.isWritable()) {
+        destination.ensureWritable(ZLIB_BUFFER_SIZE);
+      }
+
+      int produced = deflater.deflate(destination.array(), destination.arrayOffset()
+          + destination.writerIndex(), destination.writableBytes());
+      destination.writerIndex(destination.writerIndex() + produced);
+    }
   }
 
   @Override
@@ -77,7 +128,7 @@ public class JavaVelocityCompressor implements VelocityCompressor {
   }
 
   @Override
-  public boolean isNative() {
-    return false;
+  public BufferPreference preferredBufferType() {
+    return BufferPreference.HEAP_PREFERRED;
   }
 }

native/src/main/java/com/velocitypowered/natives/compression/NativeVelocityCompressor.java

@@ -4,6 +4,7 @@ import static com.velocitypowered.natives.compression.CompressorUtils.ZLIB_BUFFE
 import static com.velocitypowered.natives.compression.CompressorUtils.ensureMaxSize;
 
 import com.google.common.base.Preconditions;
+import com.velocitypowered.natives.util.BufferPreference;
 import io.netty.buffer.ByteBuf;
 import java.util.zip.DataFormatException;
 
@@ -82,7 +83,7 @@ public class NativeVelocityCompressor implements VelocityCompressor {
   }
 
   @Override
-  public boolean isNative() {
-    return true;
+  public BufferPreference preferredBufferType() {
+    return BufferPreference.DIRECT_REQUIRED;
   }
 }

native/src/main/java/com/velocitypowered/natives/encryption/JavaVelocityCipher.java

@@ -1,6 +1,7 @@
 package com.velocitypowered.natives.encryption;
 
 import com.google.common.base.Preconditions;
+import com.velocitypowered.natives.util.BufferPreference;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufUtil;
 import io.netty.channel.ChannelHandlerContext;
@@ -34,50 +35,25 @@ public class JavaVelocityCipher implements VelocityCipher {
   }
 
   @Override
-  public void process(ByteBuf source, ByteBuf destination) throws ShortBufferException {
+  public void process(ByteBuf source) {
     ensureNotDisposed();
+    Preconditions.checkArgument(source.hasArray(), "No source array");
 
     int inBytes = source.readableBytes();
-    byte[] asBytes = ByteBufUtil.getBytes(source);
+    int baseOffset = source.arrayOffset() + source.readerIndex();
 
-    int outputSize = cipher.getOutputSize(inBytes);
-    byte[] outBuf = new byte[outputSize];
-    cipher.update(asBytes, 0, inBytes, outBuf);
-    destination.writeBytes(outBuf);
-  }
-
-  @Override
-  public ByteBuf process(ChannelHandlerContext ctx, ByteBuf source) throws ShortBufferException {
-    ensureNotDisposed();
-
-    int inBytes = source.readableBytes();
-    ByteBuf asHeapBuf = toHeap(source);
-    ByteBuf out = ctx.alloc().heapBuffer(cipher.getOutputSize(inBytes));
     try {
-      out.writerIndex(
-          cipher.update(asHeapBuf.array(), asHeapBuf.arrayOffset() + asHeapBuf.readerIndex(),
-              inBytes, out.array(), out.arrayOffset() + out.writerIndex()));
-      return out;
-    } catch (ShortBufferException e) {
-      out.release();
-      throw e;
-    } finally {
-      asHeapBuf.release();
+      cipher.update(source.array(), baseOffset, inBytes, source.array(), baseOffset);
+    } catch (ShortBufferException ex) {
+      /* This _really_ shouldn't happen - AES CFB8 will work in place.
+         If you run into this, that means that for whatever reason the Java Runtime has determined
+         that the output buffer needs more bytes than the input buffer. When we are working with
+         AES-CFB8, the output size is equal to the input size. See the problem? */
+      throw new AssertionError("Cipher update did not operate in place and requested a larger "
+              + "buffer than the source buffer");
     }
   }
 
-  private static ByteBuf toHeap(ByteBuf src) {
-    if (src.hasArray()) {
-      return src.retain();
-    }
-
-    // Copy into a temporary heap buffer. We could use a local buffer, but Netty pools all buffers,
-    // so we'd lose more than we gain.
-    ByteBuf asHeapBuf = src.alloc().heapBuffer(src.readableBytes());
-    asHeapBuf.writeBytes(src);
-    return asHeapBuf;
-  }
-
   @Override
   public void dispose() {
     disposed = true;
@@ -88,7 +64,7 @@ public class JavaVelocityCipher implements VelocityCipher {
   }
 
   @Override
-  public boolean isNative() {
-    return false;
+  public BufferPreference preferredBufferType() {
+    return BufferPreference.HEAP_REQUIRED;
   }
 }

native/src/main/java/com/velocitypowered/natives/encryption/NativeVelocityCipher.java

@@ -1,6 +1,7 @@
 package com.velocitypowered.natives.encryption;
 
 import com.google.common.base.Preconditions;
+import com.velocitypowered.natives.util.BufferPreference;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
 import java.security.GeneralSecurityException;
@@ -32,40 +33,14 @@ public class NativeVelocityCipher implements VelocityCipher {
   }
 
   @Override
-  public void process(ByteBuf source, ByteBuf destination) throws ShortBufferException {
+  public void process(ByteBuf source) {
     ensureNotDisposed();
     source.memoryAddress();
-    destination.memoryAddress();
 
-    // The exact amount we read in is also the amount we write out.
+    long base = source.memoryAddress() + source.readerIndex();
     int len = source.readableBytes();
-    destination.ensureWritable(len);
 
-    impl.process(ctx, source.memoryAddress() + source.readerIndex(), len,
-        destination.memoryAddress() + destination.writerIndex(), encrypt);
-
-    source.skipBytes(len);
-    destination.writerIndex(destination.writerIndex() + len);
-  }
-
-  @Override
-  public ByteBuf process(ChannelHandlerContext ctx, ByteBuf source) throws ShortBufferException {
-    ensureNotDisposed();
-    source.memoryAddress(); // sanity check
-
-    int len = source.readableBytes();
-    ByteBuf out = ctx.alloc().directBuffer(len);
-
-    try {
-      impl.process(this.ctx, source.memoryAddress() + source.readerIndex(), len,
-          out.memoryAddress(), encrypt);
-      source.skipBytes(len);
-      out.writerIndex(len);
-      return out;
-    } catch (Exception e) {
-      out.release();
-      throw e;
-    }
+    impl.process(ctx, base, len, base, encrypt);
   }
 
   @Override
@@ -81,7 +56,7 @@ public class NativeVelocityCipher implements VelocityCipher {
   }
 
   @Override
-  public boolean isNative() {
-    return true;
+  public BufferPreference preferredBufferType() {
+    return BufferPreference.DIRECT_REQUIRED;
   }
 }

native/src/main/java/com/velocitypowered/natives/encryption/VelocityCipher.java

@@ -7,8 +7,5 @@ import io.netty.channel.ChannelHandlerContext;
 import javax.crypto.ShortBufferException;
 
 public interface VelocityCipher extends Disposable, Native {
-
-  void process(ByteBuf source, ByteBuf destination) throws ShortBufferException;
-
-  ByteBuf process(ChannelHandlerContext ctx, ByteBuf source) throws ShortBufferException;
+  void process(ByteBuf source);
 }

native/src/main/java/com/velocitypowered/natives/util/BufferPreference.java

@@ -0,0 +1,20 @@
+package com.velocitypowered.natives.util;
+
+public enum BufferPreference {
+  /**
+   * A heap buffer is required.
+   */
+  HEAP_REQUIRED,
+  /**
+   * A heap buffer is preferred (but not required).
+   */
+  HEAP_PREFERRED,
+  /**
+   * A direct buffer is preferred (but not required).
+   */
+  DIRECT_PREFERRED,
+  /**
+   * A direct buffer is required.
+   */
+  DIRECT_REQUIRED
+}

native/src/main/java/com/velocitypowered/natives/util/MoreByteBufUtils.java

@@ -20,28 +20,30 @@ public class MoreByteBufUtils {
    * @return a buffer compatible with the native
    */
   public static ByteBuf ensureCompatible(ByteBufAllocator alloc, Native nativeStuff, ByteBuf buf) {
-    if (!nativeStuff.isNative() || buf.hasMemoryAddress()) {
-      // Will always work in either case. JNI code demands a memory address, and if we have a Java
-      // fallback, it uses byte arrays in all cases.
+    if (isCompatible(nativeStuff, buf)) {
       return buf.retain();
     }
 
     // It's not, so we must make a direct copy.
-    ByteBuf newBuf = alloc.directBuffer(buf.readableBytes());
+    ByteBuf newBuf = preferredBuffer(alloc, nativeStuff, buf.readableBytes());
     newBuf.writeBytes(buf);
     return newBuf;
   }
 
-  /**
-   * Creates a {@link ByteBuf} that will have the best performance with the specified
-   * {@code nativeStuff}.
-   *
-   * @param alloc the {@link ByteBufAllocator} to use
-   * @param nativeStuff the native we are working with
-   * @return a buffer compatible with the native
-   */
-  public static ByteBuf preferredBuffer(ByteBufAllocator alloc, Native nativeStuff) {
-    return nativeStuff.isNative() ? alloc.directBuffer() : alloc.heapBuffer();
+  private static boolean isCompatible(Native nativeStuff, ByteBuf buf) {
+    BufferPreference preferred = nativeStuff.preferredBufferType();
+    switch (preferred) {
+      case DIRECT_PREFERRED:
+      case HEAP_PREFERRED:
+        // The native prefers this type, but doesn't strictly require we provide it.
+        return true;
+      case DIRECT_REQUIRED:
+        return buf.hasMemoryAddress();
+      case HEAP_REQUIRED:
+        return buf.hasArray();
+      default:
+        throw new AssertionError("Preferred buffer type unknown");
+    }
   }
 
   /**
@@ -55,7 +57,15 @@ public class MoreByteBufUtils {
    */
   public static ByteBuf preferredBuffer(ByteBufAllocator alloc, Native nativeStuff,
       int initialCapacity) {
-    return nativeStuff.isNative() ? alloc.directBuffer(initialCapacity) : alloc
-        .heapBuffer(initialCapacity);
+    switch (nativeStuff.preferredBufferType()) {
+      case HEAP_REQUIRED:
+      case HEAP_PREFERRED:
+        return alloc.heapBuffer(initialCapacity);
+      case DIRECT_PREFERRED:
+      case DIRECT_REQUIRED:
+        return alloc.directBuffer(initialCapacity);
+      default:
+        throw new AssertionError("Preferred buffer type unknown");
+    }
   }
 }

native/src/main/java/com/velocitypowered/natives/util/NativeCodeLoader.java

@@ -15,7 +15,7 @@ public final class NativeCodeLoader<T> implements Supplier<T> {
 
   @Override
   public T get() {
-    return selected.object;
+    return selected.constructed;
   }
 
   private static <T> Variant<T> getVariant(List<Variant<T>> variants) {
@@ -38,9 +38,14 @@ public final class NativeCodeLoader<T> implements Supplier<T> {
     private Status status;
     private final Runnable setup;
     private final String name;
-    private final T object;
+    private final Supplier<T> object;
+    private T constructed;
 
     Variant(BooleanSupplier possiblyAvailable, Runnable setup, String name, T object) {
+      this(possiblyAvailable, setup, name, () -> object);
+    }
+
+    Variant(BooleanSupplier possiblyAvailable, Runnable setup, String name, Supplier<T> object) {
       this.status =
           possiblyAvailable.getAsBoolean() ? Status.POSSIBLY_AVAILABLE : Status.NOT_AVAILABLE;
       this.setup = setup;
@@ -57,6 +62,7 @@ public final class NativeCodeLoader<T> implements Supplier<T> {
       if (status == Status.POSSIBLY_AVAILABLE) {
         try {
           setup.run();
+          constructed = object.get();
           status = Status.SETUP;
         } catch (Exception e) {
           status = Status.SETUP_FAILURE;
@@ -64,7 +70,7 @@ public final class NativeCodeLoader<T> implements Supplier<T> {
         }
       }
 
-      return object;
+      return constructed;
     }
   }
 

native/src/main/java/com/velocitypowered/natives/util/NativeConstraints.java

@@ -6,6 +6,7 @@ import java.util.function.BooleanSupplier;
 
 public class NativeConstraints {
   private static final boolean NATIVES_ENABLED = !Boolean.getBoolean("velocity.natives-disabled");
+  private static final boolean IS_AMD64;
   private static final boolean CAN_GET_MEMORYADDRESS;
 
   static {
@@ -15,19 +16,28 @@ public class NativeConstraints {
     } finally {
       test.release();
     }
+
+    String osArch = System.getProperty("os.arch", "");
+    // HotSpot on Intel macOS prefers x86_64, but OpenJ9 on macOS and HotSpot/OpenJ9 elsewhere
+    // give amd64.
+    IS_AMD64 = osArch.equals("amd64") || osArch.equals("x86_64");
   }
 
   static final BooleanSupplier MACOS = () -> {
     return NATIVES_ENABLED
         && CAN_GET_MEMORYADDRESS
         && System.getProperty("os.name", "").equalsIgnoreCase("Mac OS X")
-        && System.getProperty("os.arch", "").equals("x86_64");
+        && IS_AMD64;
   };
 
   static final BooleanSupplier LINUX = () -> {
     return NATIVES_ENABLED
         && CAN_GET_MEMORYADDRESS
         && System.getProperty("os.name", "").equalsIgnoreCase("Linux")
-        && System.getProperty("os.arch", "").equals("amd64");
+        && IS_AMD64;
+  };
+
+  static final BooleanSupplier JAVA_11 = () -> {
+    return Double.parseDouble(System.getProperty("java.specification.version")) >= 11;
   };
 }

native/src/main/java/com/velocitypowered/natives/util/Natives.java

@@ -2,6 +2,7 @@ package com.velocitypowered.natives.util;
 
 import com.google.common.collect.ImmutableList;
 import com.velocitypowered.natives.NativeSetupException;
+import com.velocitypowered.natives.compression.Java11VelocityCompressor;
 import com.velocitypowered.natives.compression.JavaVelocityCompressor;
 import com.velocitypowered.natives.compression.NativeVelocityCompressor;
 import com.velocitypowered.natives.compression.VelocityCompressorFactory;
@@ -52,6 +53,8 @@ public class Natives {
           new NativeCodeLoader.Variant<>(NativeConstraints.LINUX,
               copyAndLoadNative("/linux_x64/velocity-compress.so"), "native (Linux amd64)",
               NativeVelocityCompressor.FACTORY),
+          new NativeCodeLoader.Variant<>(NativeConstraints.JAVA_11, () -> {
+          }, "Java 11", () -> Java11VelocityCompressor.FACTORY),
           new NativeCodeLoader.Variant<>(NativeCodeLoader.ALWAYS, () -> {
           }, "Java", JavaVelocityCompressor.FACTORY)
       )

native/src/test/java/com/velocitypowered/natives/compression/VelocityCompressorTest.java

@@ -6,6 +6,7 @@ import static org.junit.jupiter.api.Assertions.fail;
 import static org.junit.jupiter.api.condition.OS.LINUX;
 import static org.junit.jupiter.api.condition.OS.MAC;
 
+import com.velocitypowered.natives.util.BufferPreference;
 import com.velocitypowered.natives.util.Natives;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufUtil;
@@ -17,7 +18,9 @@ import java.util.zip.DataFormatException;
 import java.util.zip.Deflater;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledOnJre;
 import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.JRE;
 
 class VelocityCompressorTest {
 
@@ -39,7 +42,7 @@ class VelocityCompressorTest {
   @EnabledOnOs({MAC, LINUX})
   void nativeIntegrityCheck() throws DataFormatException {
     VelocityCompressor compressor = Natives.compress.get().create(Deflater.DEFAULT_COMPRESSION);
-    if (compressor instanceof JavaVelocityCompressor) {
+    if (compressor.preferredBufferType() != BufferPreference.DIRECT_REQUIRED) {
       compressor.dispose();
       fail("Loaded regular compressor");
     }
@@ -60,6 +63,22 @@ class VelocityCompressorTest {
     check(compressor, () -> Unpooled.buffer(TEST_DATA.length + 32));
   }
 
+  @Test
+  @EnabledOnJre(JRE.JAVA_11)
+  void java11IntegrityCheckDirect() throws DataFormatException {
+    VelocityCompressor compressor = Java11VelocityCompressor.FACTORY
+        .create(Deflater.DEFAULT_COMPRESSION);
+    check(compressor, () -> Unpooled.directBuffer(TEST_DATA.length + 32));
+  }
+
+  @Test
+  @EnabledOnJre(JRE.JAVA_11)
+  void java11IntegrityCheckHeap() throws DataFormatException {
+    VelocityCompressor compressor = Java11VelocityCompressor.FACTORY
+        .create(Deflater.DEFAULT_COMPRESSION);
+    check(compressor, () -> Unpooled.buffer(TEST_DATA.length + 32));
+  }
+
   private void check(VelocityCompressor compressor, Supplier<ByteBuf> bufSupplier)
       throws DataFormatException {
     ByteBuf source = bufSupplier.get();

native/src/test/java/com/velocitypowered/natives/encryption/VelocityCipherTest.java

@@ -56,20 +56,18 @@ class VelocityCipherTest {
     VelocityCipher encrypt = factory.forEncryption(new SecretKeySpec(AES_KEY, "AES"));
 
     ByteBuf source = bufSupplier.get();
-    ByteBuf dest = bufSupplier.get();
-    ByteBuf decryptionBuf = bufSupplier.get();
 
     source.writeBytes(TEST_DATA);
 
+    ByteBuf workingBuf = source.copy();
+
     try {
-      encrypt.process(source, dest);
-      decrypt.process(dest, decryptionBuf);
-      source.readerIndex(0);
-      assertTrue(ByteBufUtil.equals(source, decryptionBuf));
+      encrypt.process(workingBuf);
+      decrypt.process(workingBuf);
+      assertTrue(ByteBufUtil.equals(source, workingBuf));
     } finally {
       source.release();
-      dest.release();
-      decryptionBuf.release();
+      workingBuf.release();
       decrypt.dispose();
       encrypt.dispose();
     }

proxy/build.gradle

@@ -48,6 +48,8 @@ dependencies {
     compile "io.netty:netty-handler:${nettyVersion}"
     compile "io.netty:netty-transport-native-epoll:${nettyVersion}"
     compile "io.netty:netty-transport-native-epoll:${nettyVersion}:linux-x86_64"
+    compile "io.netty:netty-transport-native-kqueue:${nettyVersion}"
+    compile "io.netty:netty-transport-native-kqueue:${nettyVersion}:osx-x86_64"
     compile "io.netty:netty-resolver-dns:${nettyVersion}"
 
     compile "org.apache.logging.log4j:log4j-api:${log4jVersion}"
@@ -65,7 +67,7 @@ dependencies {
 
     compile 'com.mojang:brigadier:1.0.15'
     
-    compile 'org.asynchttpclient:async-http-client:2.10.1'
+    compile 'org.asynchttpclient:async-http-client:2.10.4'
     
     compile 'com.spotify:completable-futures:0.3.2'
 

proxy/src/main/java/com/velocitypowered/proxy/command/VelocityCommand.java

@@ -72,7 +72,10 @@ public class VelocityCommand implements Command {
   @Override
   public List<String> suggest(CommandSource source, String @NonNull [] currentArgs) {
     if (currentArgs.length == 0) {
-      return ImmutableList.copyOf(subcommands.keySet());
+      return subcommands.entrySet().stream()
+              .filter(e -> e.getValue().hasPermission(source, new String[0]))
+              .map(Map.Entry::getKey)
+              .collect(ImmutableList.toImmutableList());
     }
 
     if (currentArgs.length == 1) {
@@ -81,7 +84,7 @@ public class VelocityCommand implements Command {
               currentArgs[0].length()))
           .filter(e -> e.getValue().hasPermission(source, new String[0]))
           .map(Map.Entry::getKey)
-          .collect(Collectors.toList());
+          .collect(ImmutableList.toImmutableList());
     }
 
     Command command = subcommands.get(currentArgs[0].toLowerCase(Locale.US));

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

@@ -100,7 +100,7 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
       "              configuration is used if no servers could be contacted."
   })
   @ConfigKey("ping-passthrough")
-  private PingPassthroughMode pingPassthrough;
+  private PingPassthroughMode pingPassthrough = PingPassthroughMode.DISABLED;
 
   @Table("[servers]")
   private final Servers servers;
@@ -192,12 +192,7 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
     }
 
     if (servers.getServers().isEmpty()) {
-      logger.error("You have no servers configured. :(");
-      valid = false;
-    } else {
-      if (servers.getAttemptConnectionOrder().isEmpty()) {
-        logger.error("No fallback servers are configured!");
-        valid = false;
+      logger.warn("You don't have any servers configured.");
     }
 
     for (Map.Entry<String, String> entry : servers.getServers().entrySet()) {
@@ -230,7 +225,6 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
         }
       }
     }
-    }
 
     try {
       getMotdComponent();

proxy/src/main/java/com/velocitypowered/proxy/connection/ConnectionType.java

@@ -34,14 +34,4 @@ public interface ConnectionType {
    */
   GameProfile addGameProfileTokensIfRequired(GameProfile original,
                                              PlayerInfoForwarding forwardingType);
-
-  /**
-   * Tests whether the hostname is the handshake packet is valid.
-   *
-   * @param address The address to check
-   * @return true if valid.
-   */
-  default boolean checkServerAddressIsValid(String address) {
-    return true;
-  }
 }

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/TransitionSessionHandler.java

@@ -80,7 +80,8 @@ public class TransitionSessionHandler implements MinecraftSessionHandler {
     // The goods are in hand! We got JoinGame. Let's transition completely to the new state.
     smc.setAutoReading(false);
     server.getEventManager()
-        .fire(new ServerConnectedEvent(serverConn.getPlayer(), serverConn.getServer()))
+        .fire(new ServerConnectedEvent(serverConn.getPlayer(), serverConn.getServer(),
+            existingConnection != null ? existingConnection.getServer() : null))
         .whenCompleteAsync((x, error) -> {
           // Strap on the ClientPlaySessionHandler if required.
           ClientPlaySessionHandler playHandler;

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -304,26 +304,20 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
       // Clear tab list to avoid duplicate entries
       player.getTabList().clearAll();
 
-      // In order to handle switching to another server, you will need to send three packets:
+      // In order to handle switching to another server, you will need to send two packets:
       //
-      // - The join game packet from the backend server
-      // - A respawn packet with a different dimension
-      // - Another respawn with the correct dimension
-      //
-      // The two respawns with different dimensions are required, otherwise the client gets
-      // confused.
+      // - The join game packet from the backend server, with a different dimension
+      // - A respawn with the correct dimension
       //
       // Most notably, by having the client accept the join game packet, we can work around the need
       // to perform entity ID rewrites, eliminating potential issues from rewriting packets and
       // improving compatibility with mods.
+      int realDim = joinGame.getDimension();
+      joinGame.setDimension(getFakeTemporaryDimensionId(realDim));
       player.getConnection().delayedWrite(joinGame);
-      int tempDim = joinGame.getDimension() == 0 ? -1 : 0;
       player.getConnection().delayedWrite(
-          new Respawn(tempDim, joinGame.getDifficulty(), joinGame.getGamemode(),
-              joinGame.getLevelType()));
-      player.getConnection().delayedWrite(
-          new Respawn(joinGame.getDimension(), joinGame.getDifficulty(), joinGame.getGamemode(),
-              joinGame.getLevelType()));
+          new Respawn(realDim, joinGame.getPartialHashedSeed(), joinGame.getDifficulty(),
+              joinGame.getGamemode(), joinGame.getLevelType()));
     }
 
     // Remove previous boss bars. These don't get cleared when sending JoinGame, thus the need to
@@ -360,11 +354,14 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     destination.completeJoin();
   }
 
+  private static int getFakeTemporaryDimensionId(int dim) {
+    return dim == 0 ? -1 : 0;
+  }
+
   public List<UUID> getServerBossBars() {
     return serverBossBars;
   }
 
-
   private boolean handleCommandTabComplete(TabCompleteRequest packet) {
     // In 1.13+, we need to do additional work for the richer suggestions available.
     String command = packet.getCommand().substring(1);
@@ -389,31 +386,19 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     }
 
     List<Offer> offers = new ArrayList<>();
-    int longestLength = 0;
     for (String suggestion : suggestions) {
       offers.add(new Offer(suggestion));
-      if (suggestion.length() > longestLength) {
-        longestLength = suggestion.length();
     }
-    }
-
-    TabCompleteResponse resp = new TabCompleteResponse();
-    resp.setTransactionId(packet.getTransactionId());
 
     int startPos = packet.getCommand().lastIndexOf(' ') + 1;
-    int length;
-    if (startPos == 0) {
-      startPos = packet.getCommand().length() + 1;
-      length = longestLength;
-    } else {
-      length = packet.getCommand().length() - startPos;
-    }
-
+    if (startPos > 0) {
+      TabCompleteResponse resp = new TabCompleteResponse();
+      resp.setTransactionId(packet.getTransactionId());
       resp.setStart(startPos);
-    resp.setLength(length);
+      resp.setLength(packet.getCommand().length() - startPos);
       resp.getOffers().addAll(offers);
-
       player.getConnection().write(resp);
+    }
     return true;
   }
 

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -425,17 +425,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
       return;
     }
 
-    if (connectedServer == null) {
-      Optional<RegisteredServer> nextServer = getNextServerToTry(rs);
-      if (nextServer.isPresent()) {
-        // There can't be any connection in flight now.
-        resetInFlightConnection();
-        createConnectionRequest(nextServer.get()).fireAndForget();
-      } else {
-        disconnect(friendlyReason);
-      }
-    } else {
-      boolean kickedFromCurrent = connectedServer.getServer().equals(rs);
+    boolean kickedFromCurrent = connectedServer == null || connectedServer.getServer().equals(rs);
     ServerKickResult result;
     if (kickedFromCurrent) {
       Optional<RegisteredServer> next = getNextServerToTry(rs);
@@ -452,7 +442,6 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
         !kickedFromCurrent, result);
     handleKickEvent(originalEvent, friendlyReason);
   }
-  }
 
   private void handleKickEvent(KickedFromServerEvent originalEvent, Component friendlyReason) {
     server.getEventManager().fire(originalEvent)
@@ -471,7 +460,11 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
                   if (newResult == null || !newResult) {
                     disconnect(friendlyReason);
                   } else {
+                    if (res.getMessage() == null) {
                       sendMessage(VelocityMessages.MOVED_TO_NEW_SERVER.append(friendlyReason));
+                    } else {
+                      sendMessage(res.getMessage());
+                    }
                   }
                 }, connection.eventLoop());
           } else if (event.getResult() instanceof Notify) {

proxy/src/main/java/com/velocitypowered/proxy/connection/client/HandshakeSessionHandler.java

@@ -26,9 +26,14 @@ import java.util.Optional;
 import net.kyori.text.TextComponent;
 import net.kyori.text.TranslatableComponent;
 import net.kyori.text.format.TextColor;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class HandshakeSessionHandler implements MinecraftSessionHandler {
 
+  private static final Logger LOGGER = LogManager.getLogger(HandshakeSessionHandler.class);
+
   private final MinecraftConnection connection;
   private final VelocityServer server;
 
@@ -58,39 +63,57 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
   public boolean handle(Handshake handshake) {
     InitialInboundConnection ic = new InitialInboundConnection(connection,
         cleanVhost(handshake.getServerAddress()), handshake);
+    StateRegistry nextState = getStateForProtocol(handshake.getNextStatus());
+    if (nextState == null) {
+      LOGGER.error("{} provided invalid protocol {}", ic, handshake.getNextStatus());
+      connection.close();
+    } else {
+      connection.setState(nextState);
+      connection.setProtocolVersion(handshake.getProtocolVersion());
       connection.setAssociation(ic);
-    switch (handshake.getNextStatus()) {
-      case StateRegistry.STATUS_ID:
-        connection.setState(StateRegistry.STATUS);
-        connection.setProtocolVersion(handshake.getProtocolVersion());
-        connection.setSessionHandler(new StatusSessionHandler(server, connection, ic));
-        return true;
-      case StateRegistry.LOGIN_ID:
-        connection.setState(StateRegistry.LOGIN);
-        connection.setProtocolVersion(handshake.getProtocolVersion());
 
+      switch (nextState) {
+        case STATUS:
+          connection.setSessionHandler(new StatusSessionHandler(server, connection, ic));
+          break;
+        case LOGIN:
+          this.handleLogin(handshake, ic);
+          break;
+        default:
+          // If you get this, it's a bug in Velocity.
+          throw new AssertionError("getStateForProtocol provided invalid state!");
+      }
+    }
+
+    return true;
+  }
+
+  private static @Nullable StateRegistry getStateForProtocol(int status) {
+    switch (status) {
+      case StateRegistry.STATUS_ID:
+        return StateRegistry.STATUS;
+      case StateRegistry.LOGIN_ID:
+        return StateRegistry.LOGIN;
+      default:
+        return null;
+    }
+  }
+
+  private void handleLogin(Handshake handshake, InitialInboundConnection ic) {
     if (!ProtocolVersion.isSupported(handshake.getProtocolVersion())) {
       connection.closeWith(Disconnect
           .create(TranslatableComponent.of("multiplayer.disconnect.outdated_client")));
-          return true;
+      return;
     }
 
     InetAddress address = ((InetSocketAddress) connection.getRemoteAddress()).getAddress();
     if (!server.getIpAttemptLimiter().attempt(address)) {
       connection.closeWith(
           Disconnect.create(TextComponent.of("You are logging in too fast, try again later.")));
-          return true;
+      return;
     }
 
-        ConnectionType type = checkForForge(handshake);
-        connection.setType(type);
-
-        // Make sure legacy forwarding is not in use on this connection.
-        if (!type.checkServerAddressIsValid(handshake.getServerAddress())) {
-          connection.closeWith(Disconnect
-              .create(TextComponent.of("Running Velocity behind Velocity is unsupported.")));
-          return true;
-        }
+    connection.setType(getHandshakeConnectionType(handshake));
 
     // If the proxy is configured for modern forwarding, we must deny connections from 1.12.2
     // and lower, otherwise IP information will never get forwarded.
@@ -98,18 +121,14 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
         && handshake.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_13) < 0) {
       connection.closeWith(Disconnect
           .create(TextComponent.of("This server is only compatible with 1.13 and above.")));
-          return true;
+      return;
     }
 
     server.getEventManager().fireAndForget(new ConnectionHandshakeEvent(ic));
     connection.setSessionHandler(new LoginSessionHandler(server, connection, ic));
-        return true;
-      default:
-        throw new IllegalArgumentException("Invalid state " + handshake.getNextStatus());
-    }
   }
 
-  private ConnectionType checkForForge(Handshake handshake) {
+  private ConnectionType getHandshakeConnectionType(Handshake handshake) {
     // Determine if we're using Forge (1.8 to 1.12, may not be the case in 1.13).
     if (handshake.getServerAddress().endsWith(LegacyForgeConstants.HANDSHAKE_HOSTNAME_TOKEN)
         && handshake.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_13) < 0) {
@@ -119,8 +138,8 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
       // forge handshake attempts. Also sends a reset handshake packet on every transition.
       return ConnectionTypes.UNDETERMINED_17;
     } else {
-      // For later: See if we can determine Forge 1.13+ here, else this will need to be UNDETERMINED
-      // until later in the cycle (most likely determinable during the LOGIN phase)
+      // Note for future implementation: Forge 1.13+ identifies itself using a slightly different
+      // hostname token.
       return ConnectionTypes.VANILLA;
     }
   }

proxy/src/main/java/com/velocitypowered/proxy/connection/client/LoginSessionHandler.java

@@ -1,24 +1,21 @@
 package com.velocitypowered.proxy.connection.client;
 
 import static com.google.common.net.UrlEscapers.urlFormParameterEscaper;
-import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_13;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_8;
 import static com.velocitypowered.proxy.VelocityServer.GSON;
 import static com.velocitypowered.proxy.connection.VelocityConstants.EMPTY_BYTE_ARRAY;
-import static com.velocitypowered.proxy.connection.VelocityConstants.VELOCITY_IP_FORWARDING_CHANNEL;
 import static com.velocitypowered.proxy.util.EncryptionUtils.decryptRsa;
 import static com.velocitypowered.proxy.util.EncryptionUtils.generateServerId;
 import static org.asynchttpclient.Dsl.asyncHttpClient;
-import static org.asynchttpclient.Dsl.config;
 
 import com.google.common.base.Preconditions;
-import com.google.common.net.UrlEscapers;
 import com.velocitypowered.api.event.connection.LoginEvent;
 import com.velocitypowered.api.event.connection.PostLoginEvent;
 import com.velocitypowered.api.event.connection.PreLoginEvent;
 import com.velocitypowered.api.event.connection.PreLoginEvent.PreLoginComponentResult;
 import com.velocitypowered.api.event.permission.PermissionsSetupEvent;
 import com.velocitypowered.api.event.player.GameProfileRequestEvent;
+import com.velocitypowered.api.event.player.PlayerChooseInitialServerEvent;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
 import com.velocitypowered.api.util.GameProfile;
 import com.velocitypowered.proxy.VelocityServer;
@@ -29,17 +26,12 @@ import com.velocitypowered.proxy.protocol.StateRegistry;
 import com.velocitypowered.proxy.protocol.packet.Disconnect;
 import com.velocitypowered.proxy.protocol.packet.EncryptionRequest;
 import com.velocitypowered.proxy.protocol.packet.EncryptionResponse;
-import com.velocitypowered.proxy.protocol.packet.LoginPluginMessage;
-import com.velocitypowered.proxy.protocol.packet.LoginPluginResponse;
 import com.velocitypowered.proxy.protocol.packet.ServerLogin;
 import com.velocitypowered.proxy.protocol.packet.ServerLoginSuccess;
 import com.velocitypowered.proxy.protocol.packet.SetCompression;
 import com.velocitypowered.proxy.util.VelocityMessages;
 import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
 import java.net.InetSocketAddress;
-import java.net.MalformedURLException;
-import java.net.URL;
 import java.security.GeneralSecurityException;
 import java.security.KeyPair;
 import java.util.Arrays;
@@ -50,7 +42,6 @@ import java.util.concurrent.ThreadLocalRandom;
 import net.kyori.text.Component;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
-import org.asynchttpclient.Dsl;
 import org.asynchttpclient.ListenableFuture;
 import org.asynchttpclient.Response;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
@@ -66,7 +57,6 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
   private final InitialInboundConnection inbound;
   private @MonotonicNonNull ServerLogin login;
   private byte[] verify = EMPTY_BYTE_ARRAY;
-  private int playerInfoId;
   private @MonotonicNonNull ConnectedPlayer connectedPlayer;
 
   LoginSessionHandler(VelocityServer server, MinecraftConnection mcConnection,
@@ -79,29 +69,7 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
   @Override
   public boolean handle(ServerLogin packet) {
     this.login = packet;
-    if (mcConnection.getProtocolVersion().compareTo(MINECRAFT_1_13) >= 0) {
-      // To make sure the connecting client isn't Velocity, send a plugin message that Velocity will
-      // recognize and respond to.
-      playerInfoId = ThreadLocalRandom.current().nextInt();
-      mcConnection.write(new LoginPluginMessage(playerInfoId, VELOCITY_IP_FORWARDING_CHANNEL,
-          Unpooled.EMPTY_BUFFER));
-    } else {
     beginPreLogin();
-    }
-    return true;
-  }
-
-  @Override
-  public boolean handle(LoginPluginResponse packet) {
-    if (packet.getId() == playerInfoId) {
-      if (packet.isSuccess()) {
-        // Uh oh, someone's trying to run Velocity behind Velocity. We don't want that happening.
-        inbound.disconnect(VelocityMessages.NO_PROXY_BEHIND_PROXY);
-      } else {
-        // Proceed with the regular login process.
-        beginPreLogin();
-      }
-    }
     return true;
   }
 
@@ -254,12 +222,6 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
   }
 
   private void finishLogin(ConnectedPlayer player) {
-    Optional<RegisteredServer> toTry = player.getNextServerToTry();
-    if (!toTry.isPresent()) {
-      player.disconnect(VelocityMessages.NO_AVAILABLE_SERVERS);
-      return;
-    }
-
     int threshold = server.getConfiguration().getCompressionThreshold();
     if (threshold >= 0 && mcConnection.getProtocolVersion().compareTo(MINECRAFT_1_8) >= 0) {
       mcConnection.write(new SetCompression(threshold));
@@ -292,11 +254,27 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
 
             mcConnection.setSessionHandler(new InitialConnectSessionHandler(player));
             server.getEventManager().fire(new PostLoginEvent(player))
-                .thenRun(() -> player.createConnectionRequest(toTry.get()).fireAndForget());
+                .thenRun(() -> connectToInitialServer(player));
           }
         }, mcConnection.eventLoop());
   }
 
+  private void connectToInitialServer(ConnectedPlayer player) {
+    Optional<RegisteredServer> initialFromConfig = player.getNextServerToTry();
+    PlayerChooseInitialServerEvent event = new PlayerChooseInitialServerEvent(player,
+        initialFromConfig.orElse(null));
+
+    server.getEventManager().fire(event)
+        .thenRunAsync(() -> {
+          Optional<RegisteredServer> toTry = event.getInitialServer();
+          if (!toTry.isPresent()) {
+            player.disconnect(VelocityMessages.NO_AVAILABLE_SERVERS);
+            return;
+          }
+          player.createConnectionRequest(toTry.get()).fireAndForget();
+        }, mcConnection.eventLoop());
+  }
+
   @Override
   public void handleUnknown(ByteBuf buf) {
     mcConnection.close();

proxy/src/main/java/com/velocitypowered/proxy/connection/forge/legacy/LegacyForgeConstants.java

@@ -6,7 +6,7 @@ package com.velocitypowered.proxy.connection.forge.legacy;
 public class LegacyForgeConstants {
 
   /**
-   * Clients attempting to connect to 1.8+ Forge servers will have
+   * Clients attempting to connect to 1.8-1.12.2 Forge servers will have
    * this token appended to the hostname in the initial handshake
    * packet.
    */

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

@@ -7,6 +7,11 @@ import io.netty.channel.epoll.EpollDatagramChannel;
 import io.netty.channel.epoll.EpollEventLoopGroup;
 import io.netty.channel.epoll.EpollServerSocketChannel;
 import io.netty.channel.epoll.EpollSocketChannel;
+import io.netty.channel.kqueue.KQueue;
+import io.netty.channel.kqueue.KQueueDatagramChannel;
+import io.netty.channel.kqueue.KQueueEventLoopGroup;
+import io.netty.channel.kqueue.KQueueServerSocketChannel;
+import io.netty.channel.kqueue.KQueueSocketChannel;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.DatagramChannel;
 import io.netty.channel.socket.ServerSocketChannel;
@@ -22,7 +27,11 @@ enum TransportType {
       (name, type) -> new NioEventLoopGroup(0, createThreadFactory(name, type))),
   EPOLL("epoll", EpollServerSocketChannel.class, EpollSocketChannel.class,
       EpollDatagramChannel.class,
-      (name, type) -> new EpollEventLoopGroup(0, createThreadFactory(name, type)));
+      (name, type) -> new EpollEventLoopGroup(0, createThreadFactory(name, type))),
+  KQUEUE("Kqueue", KQueueServerSocketChannel.class, KQueueSocketChannel.class,
+      KQueueDatagramChannel.class,
+      (name, type) -> new KQueueEventLoopGroup(0, createThreadFactory(name, type)));
+
 
   final String name;
   final Class<? extends ServerSocketChannel> serverSocketChannelClass;
@@ -62,6 +71,8 @@ enum TransportType {
 
     if (Epoll.isAvailable()) {
       return EPOLL;
+    } else if (KQueue.isAvailable()) {
+      return KQUEUE;
     } else {
       return NIO;
     }

proxy/src/main/java/com/velocitypowered/proxy/plugin/VelocityPluginManager.java

@@ -3,6 +3,7 @@ package com.velocitypowered.proxy.plugin;
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 
+import com.google.common.base.Joiner;
 import com.velocitypowered.api.plugin.PluginContainer;
 import com.velocitypowered.api.plugin.PluginDescription;
 import com.velocitypowered.api.plugin.PluginManager;
@@ -101,6 +102,8 @@ public class VelocityPluginManager implements PluginManager {
         continue;
       }
 
+      logger.info("Loaded plugin {} {} by {}", plugin.getId(), plugin.getVersion()
+          .orElse("<UNKNOWN>"), Joiner.on(", ").join(plugin.getAuthors()));
       registerPlugin(pluginObject);
     }
   }

proxy/src/main/java/com/velocitypowered/proxy/protocol/StateRegistry.java

@@ -5,6 +5,7 @@ import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_12;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_12_1;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_13;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_14;
+import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_15;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_7_2;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_8;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_9;
@@ -120,51 +121,61 @@ public enum StateRegistry {
           map(0x1F, MINECRAFT_1_14, false));
 
       clientbound.register(BossBar.class, BossBar::new,
-          map(0x0C, MINECRAFT_1_9, false));
+          map(0x0C, MINECRAFT_1_9, false),
+          map(0x0D, MINECRAFT_1_15, false));
       clientbound.register(Chat.class, Chat::new,
           map(0x02, MINECRAFT_1_7_2, true),
           map(0x0F, MINECRAFT_1_9, true),
-          map(0x0E, MINECRAFT_1_13, true));
+          map(0x0E, MINECRAFT_1_13, true),
+          map(0x0F, MINECRAFT_1_15, true));
       clientbound.register(TabCompleteResponse.class, TabCompleteResponse::new,
           map(0x3A, MINECRAFT_1_7_2, false),
           map(0x0E, MINECRAFT_1_9, false),
-          map(0x10, MINECRAFT_1_13, false));
+          map(0x10, MINECRAFT_1_13, false),
+          map(0x11, MINECRAFT_1_15, false));
       clientbound.register(AvailableCommands.class, AvailableCommands::new,
-          map(0x11, MINECRAFT_1_13, false));
+          map(0x11, MINECRAFT_1_13, false),
+          map(0x12, MINECRAFT_1_15, false));
       clientbound.register(PluginMessage.class, PluginMessage::new,
           map(0x3F, MINECRAFT_1_7_2, false),
           map(0x18, MINECRAFT_1_9, false),
           map(0x19, MINECRAFT_1_13, false),
-          map(0x18, MINECRAFT_1_14, false));
+          map(0x18, MINECRAFT_1_14, false),
+          map(0x19, MINECRAFT_1_15, false));
       clientbound.register(Disconnect.class, Disconnect::new,
           map(0x40, MINECRAFT_1_7_2, false),
           map(0x1A, MINECRAFT_1_9, false),
           map(0x1B, MINECRAFT_1_13, false),
-          map(0x1A, MINECRAFT_1_14, false));
+          map(0x1A, MINECRAFT_1_14, false),
+          map(0x1B, MINECRAFT_1_15, false));
       clientbound.register(KeepAlive.class, KeepAlive::new,
           map(0x00, MINECRAFT_1_7_2, false),
           map(0x1F, MINECRAFT_1_9, false),
           map(0x21, MINECRAFT_1_13, false),
-          map(0x20, MINECRAFT_1_14, false));
+          map(0x20, MINECRAFT_1_14, false),
+          map(0x21, MINECRAFT_1_15, false));
       clientbound.register(JoinGame.class, JoinGame::new,
           map(0x01, MINECRAFT_1_7_2, false),
           map(0x23, MINECRAFT_1_9, false),
           map(0x25, MINECRAFT_1_13, false),
-          map(0x25, MINECRAFT_1_14, false));
+          map(0x25, MINECRAFT_1_14, false),
+          map(0x26, MINECRAFT_1_15, false));
       clientbound.register(Respawn.class, Respawn::new,
           map(0x07, MINECRAFT_1_7_2, true),
           map(0x33, MINECRAFT_1_9, true),
           map(0x34, MINECRAFT_1_12, true),
           map(0x35, MINECRAFT_1_12_1, true),
           map(0x38, MINECRAFT_1_13, true),
-          map(0x3A, MINECRAFT_1_14, true));
+          map(0x3A, MINECRAFT_1_14, true),
+          map(0x3B, MINECRAFT_1_15, true));
       clientbound.register(ResourcePackRequest.class, ResourcePackRequest::new,
           map(0x48, MINECRAFT_1_8, true),
           map(0x32, MINECRAFT_1_9, true),
           map(0x33, MINECRAFT_1_12, true),
           map(0x34, MINECRAFT_1_12_1, true),
           map(0x37, MINECRAFT_1_13, true),
-          map(0x39, MINECRAFT_1_14, true));
+          map(0x39, MINECRAFT_1_14, true),
+          map(0x3A, MINECRAFT_1_15, true));
       clientbound.register(HeaderAndFooter.class, HeaderAndFooter::new,
           map(0x47, MINECRAFT_1_8, true),
           map(0x48, MINECRAFT_1_9, true),
@@ -172,20 +183,23 @@ public enum StateRegistry {
           map(0x49, MINECRAFT_1_12, true),
           map(0x4A, MINECRAFT_1_12_1, true),
           map(0x4E, MINECRAFT_1_13, true),
-          map(0x53, MINECRAFT_1_14, true));
+          map(0x53, MINECRAFT_1_14, true),
+          map(0x54, MINECRAFT_1_15, true));
       clientbound.register(TitlePacket.class, TitlePacket::new,
           map(0x45, MINECRAFT_1_8, true),
           map(0x45, MINECRAFT_1_9, true),
           map(0x47, MINECRAFT_1_12, true),
           map(0x48, MINECRAFT_1_12_1, true),
           map(0x4B, MINECRAFT_1_13, true),
-          map(0x4F, MINECRAFT_1_14, true));
+          map(0x4F, MINECRAFT_1_14, true),
+          map(0x50, MINECRAFT_1_15, true));
       clientbound.register(PlayerListItem.class, PlayerListItem::new,
           map(0x38, MINECRAFT_1_7_2, false),
           map(0x2D, MINECRAFT_1_9, false),
           map(0x2E, MINECRAFT_1_12_1, false),
           map(0x30, MINECRAFT_1_13, false),
-          map(0x33, MINECRAFT_1_14, false));
+          map(0x33, MINECRAFT_1_14, false),
+          map(0x34, MINECRAFT_1_15, false));
     }
   },
   LOGIN {

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/GS4QueryHandler.java

@@ -18,6 +18,7 @@ import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.channel.socket.DatagramPacket;
 import java.net.InetAddress;
 import java.nio.charset.StandardCharsets;
+import java.security.SecureRandom;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Iterator;
@@ -59,6 +60,7 @@ public class GS4QueryHandler extends SimpleChannelInboundHandler<DatagramPacket>
   private final Cache<InetAddress, Integer> sessions = CacheBuilder.newBuilder()
       .expireAfterWrite(30, TimeUnit.SECONDS)
       .build();
+  private final SecureRandom random;
 
   private volatile @MonotonicNonNull List<QueryResponse.PluginInformation> pluginInformationList
       = null;
@@ -67,6 +69,7 @@ public class GS4QueryHandler extends SimpleChannelInboundHandler<DatagramPacket>
 
   public GS4QueryHandler(VelocityServer server) {
     this.server = server;
+    this.random = new SecureRandom();
   }
 
   private QueryResponse createInitialResponse() {
@@ -111,7 +114,7 @@ public class GS4QueryHandler extends SimpleChannelInboundHandler<DatagramPacket>
       switch (type) {
         case QUERY_TYPE_HANDSHAKE: {
           // Generate new challenge token and put it into the sessions cache
-          int challengeToken = ThreadLocalRandom.current().nextInt();
+          int challengeToken = random.nextInt();
           sessions.put(senderAddress, challengeToken);
 
           // Respond with challenge token

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftCipherDecoder.java

@@ -5,10 +5,10 @@ import com.velocitypowered.natives.encryption.VelocityCipher;
 import com.velocitypowered.natives.util.MoreByteBufUtils;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
-import io.netty.handler.codec.ByteToMessageDecoder;
+import io.netty.handler.codec.MessageToMessageDecoder;
 import java.util.List;
 
-public class MinecraftCipherDecoder extends ByteToMessageDecoder {
+public class MinecraftCipherDecoder extends MessageToMessageDecoder<ByteBuf> {
 
   private final VelocityCipher cipher;
 
@@ -18,16 +18,19 @@ public class MinecraftCipherDecoder extends ByteToMessageDecoder {
 
   @Override
   protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
-    ByteBuf compatible = MoreByteBufUtils.ensureCompatible(ctx.alloc(), cipher, in);
+    ByteBuf compatible = MoreByteBufUtils.ensureCompatible(ctx.alloc(), cipher, in).slice();
     try {
-      out.add(cipher.process(ctx, compatible));
-    } finally {
-      compatible.release();
+      cipher.process(compatible);
+      out.add(compatible);
+      in.skipBytes(in.readableBytes());
+    } catch (Exception e) {
+      compatible.release(); // compatible will never be used if we throw an exception
+      throw e;
     }
   }
 
   @Override
-  protected void handlerRemoved0(ChannelHandlerContext ctx) throws Exception {
+  public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
     cipher.dispose();
   }
 }

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftCipherEncoder.java

@@ -20,9 +20,11 @@ public class MinecraftCipherEncoder extends MessageToMessageEncoder<ByteBuf> {
   protected void encode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
     ByteBuf compatible = MoreByteBufUtils.ensureCompatible(ctx.alloc(), cipher, msg);
     try {
-      out.add(cipher.process(ctx, compatible));
-    } finally {
-      compatible.release();
+      cipher.process(compatible);
+      out.add(compatible);
+    } catch (Exception e) {
+      compatible.release(); // compatible will never be used if we throw an exception
+      throw e;
     }
   }
 

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftCompressDecoder.java

@@ -13,7 +13,8 @@ import java.util.List;
 
 public class MinecraftCompressDecoder extends MessageToMessageDecoder<ByteBuf> {
 
-  private static final int MAXIMUM_UNCOMPRESSED_SIZE = 2 * 1024 * 1024; // 2MiB
+  private static final int SOFT_MAXIMUM_UNCOMPRESSED_SIZE = 2 * 1024 * 1024; // 2MiB
+  private static final int HARD_MAXIMUM_UNCOMPRESSED_SIZE = 16 * 1024 * 1024; // 16MiB
 
   private final int threshold;
   private final VelocityCompressor compressor;
@@ -25,21 +26,23 @@ public class MinecraftCompressDecoder extends MessageToMessageDecoder<ByteBuf> {
 
   @Override
   protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
-    int expectedSize = ProtocolUtils.readVarInt(in);
-    if (expectedSize == 0) {
+    int claimedUncompressedSize = ProtocolUtils.readVarInt(in);
+    if (claimedUncompressedSize == 0) {
       // Strip the now-useless uncompressed size, this message is already uncompressed.
       out.add(in.retainedSlice());
       in.skipBytes(in.readableBytes());
       return;
     }
 
-    checkFrame(expectedSize >= threshold, "Uncompressed size %s is less than threshold %s",
-        expectedSize, threshold);
-    int initialCapacity = Math.min(expectedSize, MAXIMUM_UNCOMPRESSED_SIZE);
+    checkFrame(claimedUncompressedSize >= threshold, "Uncompressed size %s is less than"
+            + " threshold %s", claimedUncompressedSize, threshold);
+    int allowedMax = Math.min(claimedUncompressedSize, HARD_MAXIMUM_UNCOMPRESSED_SIZE);
+    int initialCapacity = Math.min(claimedUncompressedSize, SOFT_MAXIMUM_UNCOMPRESSED_SIZE);
+
     ByteBuf compatibleIn = ensureCompatible(ctx.alloc(), compressor, in);
     ByteBuf uncompressed = preferredBuffer(ctx.alloc(), compressor, initialCapacity);
     try {
-      compressor.inflate(compatibleIn, uncompressed, expectedSize);
+      compressor.inflate(compatibleIn, uncompressed, allowedMax);
       out.add(uncompressed);
     } catch (Exception e) {
       uncompressed.release();

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftDecoder.java

@@ -47,20 +47,21 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf> {
         packet.decode(msg, direction, registry.version);
       } catch (Exception e) {
         throw new CorruptedFrameException(
-            "Error decoding " + packet.getClass() + " Direction " + direction
-                + " Protocol " + registry.version + " State " + state + " ID " + Integer
-                .toHexString(packetId), e);
+            "Error decoding " + packet.getClass() + " " + getExtraConnectionDetail(packetId), e);
       }
       if (msg.isReadable()) {
-        throw new CorruptedFrameException(
-            "Did not read full packet for " + packet.getClass() + " Direction " + direction
-                + " Protocol " + registry.version + " State " + state + " ID " + Integer
-                .toHexString(packetId));
+        throw new CorruptedFrameException("Did not read full packet for " + packet.getClass() + " "
+                + getExtraConnectionDetail(packetId));
       }
       out.add(packet);
     }
   }
 
+  private String getExtraConnectionDetail(int packetId) {
+    return "Direction " + direction + " Protocol " + registry.version + " State " + state
+        + " ID " + Integer.toHexString(packetId);
+  }
+
   public void setProtocolVersion(ProtocolVersion protocolVersion) {
     this.registry = direction.getProtocolRegistry(state, protocolVersion);
   }

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftVarintFrameDecoder.java

@@ -27,16 +27,13 @@ public class MinecraftVarintFrameDecoder extends ByteToMessageDecoder {
         // Make sure reader index of length buffer is returned to the beginning
         in.readerIndex(origReaderIndex);
         int packetLength = ProtocolUtils.readVarInt(in);
-        if (packetLength == 0) {
-          return;
-        }
-
-        if (in.readableBytes() < packetLength) {
-          in.readerIndex(origReaderIndex);
-          return;
-        }
 
+        if (in.readableBytes() >= packetLength) {
           out.add(in.readRetainedSlice(packetLength));
+        } else {
+          in.readerIndex(origReaderIndex);
+        }
+
         return;
       }
     }

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftVarintLengthEncoder.java

@@ -1,5 +1,7 @@
 package com.velocitypowered.proxy.protocol.netty;
 
+import com.velocitypowered.natives.encryption.JavaVelocityCipher;
+import com.velocitypowered.natives.util.Natives;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandler;
@@ -11,6 +13,7 @@ import java.util.List;
 public class MinecraftVarintLengthEncoder extends MessageToMessageEncoder<ByteBuf> {
 
   public static final MinecraftVarintLengthEncoder INSTANCE = new MinecraftVarintLengthEncoder();
+  private static final boolean IS_JAVA_CIPHER = Natives.cipher.get() == JavaVelocityCipher.FACTORY;
 
   private MinecraftVarintLengthEncoder() {
   }
@@ -18,7 +21,7 @@ public class MinecraftVarintLengthEncoder extends MessageToMessageEncoder<ByteBu
   @Override
   protected void encode(ChannelHandlerContext ctx, ByteBuf buf, List<Object> list)
       throws Exception {
-    ByteBuf lengthBuf = ctx.alloc().buffer(5); // the maximum size of a varint
+    ByteBuf lengthBuf = IS_JAVA_CIPHER ? ctx.alloc().heapBuffer(5) : ctx.alloc().directBuffer(5);
     ProtocolUtils.writeVarInt(lengthBuf, buf.readableBytes());
     list.add(lengthBuf);
     list.add(buf.retain());

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/JoinGame.java

@@ -12,11 +12,13 @@ public class JoinGame implements MinecraftPacket {
   private int entityId;
   private short gamemode;
   private int dimension;
+  private long partialHashedSeed; // 1.15+
   private short difficulty;
   private short maxPlayers;
   private @Nullable String levelType;
   private int viewDistance; //1.14+
   private boolean reducedDebugInfo;
+  private boolean mystery;
 
   public int getEntityId() {
     return entityId;
@@ -42,6 +44,10 @@ public class JoinGame implements MinecraftPacket {
     this.dimension = dimension;
   }
 
+  public long getPartialHashedSeed() {
+    return partialHashedSeed;
+  }
+
   public short getDifficulty() {
     return difficulty;
   }
@@ -91,6 +97,7 @@ public class JoinGame implements MinecraftPacket {
         + "entityId=" + entityId
         + ", gamemode=" + gamemode
         + ", dimension=" + dimension
+        + ", partialHashedSeed=" + partialHashedSeed
         + ", difficulty=" + difficulty
         + ", maxPlayers=" + maxPlayers
         + ", levelType='" + levelType + '\''
@@ -111,6 +118,9 @@ public class JoinGame implements MinecraftPacket {
     if (version.compareTo(ProtocolVersion.MINECRAFT_1_13_2) <= 0) {
       this.difficulty = buf.readUnsignedByte();
     }
+    if (version.compareTo(ProtocolVersion.MINECRAFT_1_15) >= 0) {
+      this.partialHashedSeed = buf.readLong();
+    }
     this.maxPlayers = buf.readUnsignedByte();
     this.levelType = ProtocolUtils.readString(buf, 16);
     if (version.compareTo(ProtocolVersion.MINECRAFT_1_14) >= 0) {
@@ -119,6 +129,9 @@ public class JoinGame implements MinecraftPacket {
     if (version.compareTo(ProtocolVersion.MINECRAFT_1_8) >= 0) {
       this.reducedDebugInfo = buf.readBoolean();
     }
+    if (version.compareTo(ProtocolVersion.MINECRAFT_1_15) >= 0) {
+      this.mystery = buf.readBoolean();
+    }
   }
 
   @Override
@@ -133,6 +146,9 @@ public class JoinGame implements MinecraftPacket {
     if (version.compareTo(ProtocolVersion.MINECRAFT_1_13_2) <= 0) {
       buf.writeByte(difficulty);
     }
+    if (version.compareTo(ProtocolVersion.MINECRAFT_1_15) >= 0) {
+      buf.writeLong(partialHashedSeed);
+    }
     buf.writeByte(maxPlayers);
     if (levelType == null) {
       throw new IllegalStateException("No level type specified.");
@@ -144,6 +160,9 @@ public class JoinGame implements MinecraftPacket {
     if (version.compareTo(ProtocolVersion.MINECRAFT_1_8) >= 0) {
       buf.writeBoolean(reducedDebugInfo);
     }
+    if (version.compareTo(ProtocolVersion.MINECRAFT_1_15) >= 0) {
+      buf.writeBoolean(mystery);
+    }
   }
 
   @Override

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/Respawn.java

@@ -9,6 +9,7 @@ import io.netty.buffer.ByteBuf;
 public class Respawn implements MinecraftPacket {
 
   private int dimension;
+  private long partialHashedSeed;
   private short difficulty;
   private short gamemode;
   private String levelType = "";
@@ -16,8 +17,10 @@ public class Respawn implements MinecraftPacket {
   public Respawn() {
   }
 
-  public Respawn(int dimension, short difficulty, short gamemode, String levelType) {
+  public Respawn(int dimension, long partialHashedSeed, short difficulty, short gamemode,
+      String levelType) {
     this.dimension = dimension;
+    this.partialHashedSeed = partialHashedSeed;
     this.difficulty = difficulty;
     this.gamemode = gamemode;
     this.levelType = levelType;
@@ -31,6 +34,14 @@ public class Respawn implements MinecraftPacket {
     this.dimension = dimension;
   }
 
+  public long getPartialHashedSeed() {
+    return partialHashedSeed;
+  }
+
+  public void setPartialHashedSeed(long partialHashedSeed) {
+    this.partialHashedSeed = partialHashedSeed;
+  }
+
   public short getDifficulty() {
     return difficulty;
   }
@@ -59,6 +70,7 @@ public class Respawn implements MinecraftPacket {
   public String toString() {
     return "Respawn{"
         + "dimension=" + dimension
+        + ", partialHashedSeed=" + partialHashedSeed
         + ", difficulty=" + difficulty
         + ", gamemode=" + gamemode
         + ", levelType='" + levelType + '\''
@@ -71,6 +83,9 @@ public class Respawn implements MinecraftPacket {
     if (version.compareTo(ProtocolVersion.MINECRAFT_1_13_2) <= 0) {
       this.difficulty = buf.readUnsignedByte();
     }
+    if (version.compareTo(ProtocolVersion.MINECRAFT_1_15) >= 0) {
+      this.partialHashedSeed = buf.readLong();
+    }
     this.gamemode = buf.readUnsignedByte();
     this.levelType = ProtocolUtils.readString(buf, 16);
   }
@@ -81,6 +96,9 @@ public class Respawn implements MinecraftPacket {
     if (version.compareTo(ProtocolVersion.MINECRAFT_1_13_2) <= 0) {
       buf.writeByte(difficulty);
     }
+    if (version.compareTo(ProtocolVersion.MINECRAFT_1_15) >= 0) {
+      buf.writeLong(partialHashedSeed);
+    }
     buf.writeByte(gamemode);
     ProtocolUtils.writeString(buf, levelType);
   }

proxy/src/main/java/com/velocitypowered/proxy/util/concurrent/VelocityNettyThreadFactory.java

@@ -17,7 +17,7 @@ public class VelocityNettyThreadFactory implements ThreadFactory {
 
   @Override
   public Thread newThread(Runnable r) {
-    String name = String.format(nameFormat, threadNumber.incrementAndGet());
+    String name = String.format(nameFormat, threadNumber.getAndIncrement());
     return new FastThreadLocalThread(r, name);
   }
 }