Add Forge mod list support

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

@@ -0,0 +1,23 @@
+package com.velocitypowered.api.event.player;
+
+import com.google.common.base.Preconditions;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.util.ModInfo;
+
+public final class PlayerModInfoEvent {
+    private final Player player;
+    private final ModInfo modInfo;
+    
+    public PlayerModInfoEvent(Player player, ModInfo modInfo) {
+        this.player = Preconditions.checkNotNull(player, "player");
+        this.modInfo = Preconditions.checkNotNull(modInfo, "modInfo");
+    }
+    
+    public Player getPlayer() {
+        return player;
+    }
+    
+    public ModInfo getModInfo() {
+        return modInfo;
+    }
+}

api/src/main/java/com/velocitypowered/api/proxy/Player.java

@@ -8,6 +8,7 @@ import com.velocitypowered.api.proxy.server.RegisteredServer;
 import com.velocitypowered.api.util.GameProfile;
 import com.velocitypowered.api.proxy.player.TabList;
 import com.velocitypowered.api.util.MessagePosition;
+import com.velocitypowered.api.util.ModInfo;
 import com.velocitypowered.api.util.title.Title;
 import java.util.List;
 
@@ -45,6 +46,12 @@ public interface Player extends CommandSource, InboundConnection, ChannelMessage
      */
     PlayerSettings getPlayerSettings();
     
+    /**
+     * Returns the player's mod info if they have a modded client.
+     * @return an {@link Optional} the mod info. which may be empty
+     */
+    Optional<ModInfo> getModInfo();
+
     /**
      * Returns the current player's ping
      * @return the player's ping or -1 if ping information is currently unknown

api/src/main/java/com/velocitypowered/api/proxy/server/ServerPing.java

@@ -3,6 +3,7 @@ package com.velocitypowered.api.proxy.server;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.velocitypowered.api.util.Favicon;
+import com.velocitypowered.api.util.ModInfo;
 import net.kyori.text.Component;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
@@ -16,13 +17,13 @@ public final class ServerPing {
     private final Players players;
     private final Component description;
     private final @Nullable Favicon favicon;
-    private final ModInfo modinfo;
+    private final @Nullable ModInfo modinfo;
 
     public ServerPing(Version version, @Nullable Players players, Component description, @Nullable Favicon favicon) {
         this(version, players, description, favicon, ModInfo.DEFAULT);
     }
 
-    public ServerPing(Version version, @Nullable Players players, Component description, @Nullable Favicon favicon, ServerPing.@Nullable ModInfo modinfo) {
+    public ServerPing(Version version, @Nullable Players players, Component description, @Nullable Favicon favicon, @Nullable ModInfo modinfo) {
         this.version = Preconditions.checkNotNull(version, "version");
         this.players = players;
         this.description = Preconditions.checkNotNull(description, "description");
@@ -74,8 +75,8 @@ public final class ServerPing {
         builder.favicon = favicon;
         builder.nullOutModinfo = modinfo == null;
         if (modinfo != null) {
-            builder.modType = modinfo.type;
+            builder.modType = modinfo.getType();
-            builder.mods.addAll(modinfo.modList);
+            builder.mods.addAll(modinfo.getMods());
         }
         return builder;
     }
@@ -93,7 +94,7 @@ public final class ServerPing {
         private int maximumPlayers;
         private final List<SamplePlayer> samplePlayers = new ArrayList<>();
         private String modType;
-        private final List<Mod> mods = new ArrayList<>();
+        private final List<ModInfo.Mod> mods = new ArrayList<>();
         private Component description;
         private Favicon favicon;
         private boolean nullOutPlayers;
@@ -128,7 +129,7 @@ public final class ServerPing {
             return this;
         }
 
-        public Builder mods(Mod... mods) {
+        public Builder mods(ModInfo.Mod... mods) {
             this.mods.addAll(Arrays.asList(mods));
             return this;
         }
@@ -196,7 +197,7 @@ public final class ServerPing {
             return modType;
         }
 
-        public List<Mod> getMods() {
+        public List<ModInfo.Mod> getMods() {
             return mods;
         }
 
@@ -301,58 +302,4 @@ public final class ServerPing {
                     '}';
         }
     }
-
-    public static final class ModInfo {
-        public static final ModInfo DEFAULT = new ModInfo("FML", ImmutableList.of());
-
-        private final String type;
-        private final List<Mod> modList;
-
-        public ModInfo(String type, List<Mod> modList) {
-            this.type = Preconditions.checkNotNull(type, "type");
-            this.modList = ImmutableList.copyOf(modList);
-        }
-
-        public String getType() {
-            return type;
-        }
-
-        public List<Mod> getMods() {
-            return modList;
-        }
-
-        @Override
-        public String toString() {
-            return "ModInfo{" +
-                    "type='" + type + '\'' +
-                    ", modList=" + modList +
-                    '}';
-        }
-    }
-
-    public static final class Mod {
-        private final String id;
-        private final String version;
-
-        public Mod(String id, String version) {
-            this.id = Preconditions.checkNotNull(id, "id");
-            this.version = Preconditions.checkNotNull(version, "version");
-        }
-
-        public String getId() {
-            return id;
-        }
-
-        public String getVersion() {
-            return version;
-        }
-
-        @Override
-        public String toString() {
-            return "Mod{" +
-                    "id='" + id + '\'' +
-                    ", version='" + version + '\'' +
-                    '}';
-        }
-    }
 }

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

@@ -0,0 +1,60 @@
+package com.velocitypowered.api.util;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+
+import java.util.List;
+
+public final class ModInfo {
+    public static final ModInfo DEFAULT = new ModInfo("FML", ImmutableList.of());
+    
+    private final String type;
+    private final List<Mod> modList;
+    
+    public ModInfo(String type, List<Mod> modList) {
+        this.type = Preconditions.checkNotNull(type, "type");
+        this.modList = ImmutableList.copyOf(modList);
+    }
+    
+    public String getType() {
+        return type;
+    }
+    
+    public List<Mod> getMods() {
+        return modList;
+    }
+    
+    @Override
+    public String toString() {
+        return "ModInfo{" +
+                "type='" + type + '\'' +
+                ", modList=" + modList +
+                '}';
+    }
+    
+    public static final class Mod {
+        private final String id;
+        private final String version;
+        
+        public Mod(String id, String version) {
+            this.id = Preconditions.checkNotNull(id, "id");
+            this.version = Preconditions.checkNotNull(version, "version");
+        }
+        
+        public String getId() {
+            return id;
+        }
+        
+        public String getVersion() {
+            return version;
+        }
+        
+        @Override
+        public String toString() {
+            return "Mod{" +
+                    "id='" + id + '\'' +
+                    ", version='" + version + '\'' +
+                    '}';
+        }
+    }
+}

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

@@ -1,10 +1,9 @@
 package com.velocitypowered.proxy.connection.client;
 
-import com.velocitypowered.api.event.connection.DisconnectEvent;
 import com.velocitypowered.api.event.connection.PluginMessageEvent;
 import com.velocitypowered.api.event.player.PlayerChatEvent;
 import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
-import com.velocitypowered.api.proxy.player.TabList;
+import com.velocitypowered.api.util.ModInfo;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
 import com.velocitypowered.proxy.connection.VelocityConstants;
@@ -13,7 +12,6 @@ import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
 import com.velocitypowered.proxy.protocol.packet.*;
 import com.velocitypowered.proxy.protocol.util.PluginMessageUtil;
-import com.velocitypowered.proxy.tablist.VelocityTabList;
 import com.velocitypowered.proxy.util.ThrowableUtils;
 import io.netty.buffer.ByteBuf;
 import net.kyori.text.TextComponent;
@@ -147,6 +145,11 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
             player.getConnectedServer().getConnection().write(PluginMessageUtil.rewriteMCBrand(packet));
         } else if (player.getConnectedServer().isLegacyForge() && !player.getConnectedServer().hasCompletedJoin()) {
             if (packet.getChannel().equals(VelocityConstants.FORGE_LEGACY_HANDSHAKE_CHANNEL)) {
+                List<ModInfo.Mod> mods = PluginMessageUtil.readModList(packet);
+                if (!mods.isEmpty()) {
+                    player.setModInfo(new ModInfo("FML", mods));
+                }
+                
                 // Always forward the FML handshake to the remote server.
                 player.getConnectedServer().getConnection().write(packet);
             } else {

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

@@ -4,6 +4,7 @@ import com.google.common.base.Preconditions;
 import com.google.gson.JsonObject;
 import com.velocitypowered.api.event.connection.DisconnectEvent;
 import com.velocitypowered.api.event.player.KickedFromServerEvent;
+import com.velocitypowered.api.event.player.PlayerModInfoEvent;
 import com.velocitypowered.api.event.player.PlayerSettingsChangedEvent;
 import com.velocitypowered.api.event.player.ServerPreConnectEvent;
 import com.velocitypowered.api.permission.PermissionFunction;
@@ -16,8 +17,8 @@ import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
 import com.velocitypowered.api.proxy.player.PlayerSettings;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
 import com.velocitypowered.api.util.GameProfile;
-import com.velocitypowered.api.proxy.player.TabList;
 import com.velocitypowered.api.util.MessagePosition;
+import com.velocitypowered.api.util.ModInfo;
 import com.velocitypowered.api.util.title.TextTitle;
 import com.velocitypowered.api.util.title.Title;
 import com.velocitypowered.api.util.title.Titles;
@@ -31,9 +32,6 @@ import com.velocitypowered.proxy.connection.util.ConnectionRequestResults;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
 import com.velocitypowered.proxy.protocol.packet.*;
 import com.velocitypowered.proxy.server.VelocityRegisteredServer;
-import com.velocitypowered.proxy.protocol.packet.Chat;
-import com.velocitypowered.proxy.protocol.packet.ClientSettings;
-import com.velocitypowered.proxy.protocol.packet.PluginMessage;
 import com.velocitypowered.proxy.tablist.VelocityTabList;
 import com.velocitypowered.proxy.util.ThrowableUtils;
 import net.kyori.text.Component;
@@ -69,6 +67,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
     private VelocityServerConnection connectedServer;
     private VelocityServerConnection connectionInFlight;
     private PlayerSettings settings;
+    private ModInfo modInfo;
     private final VelocityTabList tabList;
     private final VelocityServer server;
     
@@ -121,6 +120,15 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
         server.getEventManager().fireAndForget(new PlayerSettingsChangedEvent(this, this.settings));
     }
     
+    public Optional<ModInfo> getModInfo() {
+        return Optional.ofNullable(modInfo);
+    }
+    
+    void setModInfo(ModInfo modInfo) {
+        this.modInfo = modInfo;
+        server.getEventManager().fireAndForget(new PlayerModInfoEvent(this, this.modInfo));
+    }
+    
     @Override
     public InetSocketAddress getRemoteAddress() {
         return (InetSocketAddress) connection.getRemoteAddress();

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

@@ -4,6 +4,7 @@ import com.google.common.collect.ImmutableList;
 import com.velocitypowered.api.event.proxy.ProxyPingEvent;
 import com.velocitypowered.api.proxy.InboundConnection;
 import com.velocitypowered.api.proxy.server.ServerPing;
+import com.velocitypowered.api.util.ModInfo;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.config.VelocityConfiguration;
 import com.velocitypowered.proxy.connection.MinecraftConnection;
@@ -42,7 +43,7 @@ public class StatusSessionHandler implements MinecraftSessionHandler {
                 new ServerPing.Players(server.getPlayerCount(), configuration.getShowMaxPlayers(), ImmutableList.of()),
                 configuration.getMotdComponent(),
                 configuration.getFavicon().orElse(null),
-                configuration.isAnnounceForge() ? ServerPing.ModInfo.DEFAULT : null
+                configuration.isAnnounceForge() ? ModInfo.DEFAULT : null
         );
 
         ProxyPingEvent event = new ProxyPingEvent(inboundWrapper, initialPing);

proxy/src/main/java/com/velocitypowered/proxy/protocol/util/PluginMessageUtil.java

@@ -2,6 +2,8 @@ package com.velocitypowered.proxy.protocol.util;
 
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
+import com.velocitypowered.api.util.ModInfo;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import com.velocitypowered.proxy.protocol.packet.PluginMessage;
@@ -76,4 +78,23 @@ public class PluginMessageUtil {
         newMsg.setData(rewrittenData);
         return newMsg;
     }
+    
+    public static List<ModInfo.Mod> readModList(PluginMessage message) {
+        List<ModInfo.Mod> mods = Lists.newArrayList();
+        
+        ByteBuf byteBuf = Unpooled.wrappedBuffer(message.getData());
+        byte discriminator = byteBuf.readByte();
+        
+        if (discriminator == 2) {
+            int modCount = ProtocolUtils.readVarInt(byteBuf);
+            
+            for (int index = 0; index < modCount; index++) {
+                String id = ProtocolUtils.readString(byteBuf);
+                String version = ProtocolUtils.readString(byteBuf);
+                mods.add(new ModInfo.Mod(id, version));
+            }
+        }
+        
+        return ImmutableList.copyOf(mods);
+    }
 }