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ForgeFlower is better than Spigots FernFlower at decompiling the source. However, in order to maintain the CraftBukkit patches, we must keep using spigots for the primary. However, for any file that we import on top of Spigots imported files there is nothing stopping us from using better decompiled files. So these changes will use ForgeFlower to maintain a better set of decomped files, so anything we add on top of Paper can start off in a better spot.
172 lines
6.2 KiB
Diff
172 lines
6.2 KiB
Diff
From 564fbb85dd3c175df607e688011c4a9dbf82c71f Mon Sep 17 00:00:00 2001
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From: Minecrell <minecrell@minecrell.net>
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Date: Wed, 11 Oct 2017 18:22:50 +0200
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Subject: [PATCH] Make legacy ping handler more reliable
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The Minecraft server often fails to respond to old ("legacy") pings
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from old Minecraft versions using the protocol used before the switch
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to Netty in Minecraft 1.7.
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Due to packet fragmentation[1], we might not have all needed bytes
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available when the LegacyPingHandler is called. In this case, it will
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run into an error, remove the handler and continue using the modern
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protocol.
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This is unlikely to happen for the first two revisions of the legacy
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ping protocol (used in Minecraft 1.5.x and older) since the request
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consists of only one or two bytes, but happens frequently for the
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last/third revision introduced in Minecraft 1.6.
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It has much larger, variable packet sizes due to the inclusion of
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the virtual host (the hostname/port used to connect to the server).
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The solution[2] is simple: If we find more than two matching bytes,
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we buffer the remaining bytes until we have enough to fully read and
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respond to the request.
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[1]: https://netty.io/wiki/user-guide-for-4.x.html#wiki-h3-11
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[2]: https://netty.io/wiki/user-guide-for-4.x.html#wiki-h4-13
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diff --git a/src/main/java/net/minecraft/server/LegacyPingHandler.java b/src/main/java/net/minecraft/server/LegacyPingHandler.java
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index 5691d0aeaf..aafca9c9c4 100644
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--- a/src/main/java/net/minecraft/server/LegacyPingHandler.java
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+++ b/src/main/java/net/minecraft/server/LegacyPingHandler.java
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@@ -13,6 +13,7 @@ import org.apache.logging.log4j.Logger;
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public class LegacyPingHandler extends ChannelInboundHandlerAdapter {
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private static final Logger a = LogManager.getLogger();
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private final ServerConnection b;
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+ private ByteBuf buf; // Paper
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public LegacyPingHandler(ServerConnection serverconnection) {
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this.b = serverconnection;
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@@ -20,6 +21,16 @@ public class LegacyPingHandler extends ChannelInboundHandlerAdapter {
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public void channelRead(ChannelHandlerContext channelhandlercontext, Object object) throws Exception {
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ByteBuf bytebuf = (ByteBuf)object;
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+ // Paper start - Make legacy ping handler more reliable
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+ if (this.buf != null) {
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+ try {
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+ readLegacy1_6(channelhandlercontext, bytebuf);
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+ } finally {
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+ bytebuf.release();
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+ }
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+ return;
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+ }
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+ // Paper end
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bytebuf.markReaderIndex();
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boolean flag = true;
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@@ -44,6 +55,10 @@ public class LegacyPingHandler extends ChannelInboundHandlerAdapter {
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this.a(channelhandlercontext, this.a(s));
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break;
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default:
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+ // Paper start - Replace with improved version below
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+ if (bytebuf.readUnsignedByte() != 0x01 || bytebuf.readUnsignedByte() != 0xFA) return;
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+ readLegacy1_6(channelhandlercontext, bytebuf);
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+ /*
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boolean flag1 = bytebuf.readUnsignedByte() == 1;
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flag1 = flag1 & bytebuf.readUnsignedByte() == 250;
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flag1 = flag1 & "MC|PingHost".equals(new String(bytebuf.readBytes(bytebuf.readShort() * 2).array(), StandardCharsets.UTF_16BE));
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@@ -65,6 +80,7 @@ public class LegacyPingHandler extends ChannelInboundHandlerAdapter {
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} finally {
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bytebuf1.release();
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}
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+ */ // Paper end- end commenting out
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}
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bytebuf.release();
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@@ -84,6 +100,90 @@ public class LegacyPingHandler extends ChannelInboundHandlerAdapter {
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}
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+ // Paper start
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+ private static String readLegacyString(ByteBuf buf) {
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+ int size = buf.readShort() * Character.BYTES;
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+ if (!buf.isReadable(size)) {
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+ return null;
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+ }
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+
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+ String result = buf.toString(buf.readerIndex(), size, StandardCharsets.UTF_16BE);
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+ buf.skipBytes(size); // toString doesn't increase readerIndex automatically
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+ return result;
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+ }
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+
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+ private void readLegacy1_6(ChannelHandlerContext ctx, ByteBuf part) {
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+ ByteBuf buf = this.buf;
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+
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+ if (buf == null) {
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+ this.buf = buf = ctx.alloc().buffer();
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+ buf.markReaderIndex();
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+ } else {
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+ buf.resetReaderIndex();
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+ }
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+
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+ buf.writeBytes(part);
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+
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+ if (!buf.isReadable(Short.BYTES + Short.BYTES + Byte.BYTES + Short.BYTES + Integer.BYTES)) {
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+ return;
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+ }
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+
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+ String s = readLegacyString(buf);
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+ if (s == null) {
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+ return;
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+ }
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+
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+ if (!s.equals("MC|PingHost")) {
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+ removeHandler(ctx);
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+ return;
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+ }
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+
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+ if (!buf.isReadable(Short.BYTES) || !buf.isReadable(buf.readShort())) {
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+ return;
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+ }
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+
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+ MinecraftServer server = this.b.d();
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+ int protocolVersion = buf.readByte();
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+ String host = readLegacyString(buf);
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+ if (host == null) {
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+ removeHandler(ctx);
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+ return;
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+ }
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+ int port = buf.readInt();
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+
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+ if (buf.isReadable()) {
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+ removeHandler(ctx);
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+ return;
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+ }
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+
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+ buf.release();
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+ this.buf = null;
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+
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+ a.debug("Ping: (1.6) from {}", ctx.channel().remoteAddress());
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+
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+ String response = String.format("\u00a71\u0000%d\u0000%s\u0000%s\u0000%d\u0000%d",
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+ Byte.MAX_VALUE, server.getVersion(), server.getMotd(), server.getPlayerCount(), server.getMaxPlayers());
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+ this.a(ctx, this.a(response));
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+ }
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+
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+ private void removeHandler(ChannelHandlerContext ctx) {
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+ ByteBuf buf = this.buf;
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+ this.buf = null;
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+
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+ buf.resetReaderIndex();
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+ ctx.pipeline().remove(this);
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+ ctx.fireChannelRead(buf);
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+ }
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+
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+ @Override
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+ public void handlerRemoved(ChannelHandlerContext ctx) {
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+ if (this.buf != null) {
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+ this.buf.release();
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+ this.buf = null;
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+ }
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+ }
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+ // Paper end
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+
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private void a(ChannelHandlerContext channelhandlercontext, ByteBuf bytebuf) {
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channelhandlercontext.pipeline().firstContext().writeAndFlush(bytebuf).addListener(ChannelFutureListener.CLOSE);
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}
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--
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2.18.0
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