20 files changed, 742 insertions, 11 deletions

diff --git a/Server/Plugins/APIDump/APIDesc.lua b/Server/Plugins/APIDump/APIDesc.lua
index d7dc83043..573837333 100644
--- a/Server/Plugins/APIDump/APIDesc.lua
+++ b/Server/Plugins/APIDump/APIDesc.lua
@@ -1338,6 +1338,16 @@ end
 					},
 					Notes = "Returns the brand that the client has sent in their MC|Brand plugin message.",
 				},
+				GetForgeMods =
+				{
+					Returns =
+					{
+						{
+							Type = "table",
+						},
+					},
+					Notes = "Returns the Forge mods installed on the client.",
+				},
 				GetIPString =
 				{
 					Returns =
@@ -1456,6 +1466,16 @@ end
 					},
 					Notes = "Returns true if the client has registered to receive messages on the specified plugin channel.",
 				},
+				IsForgeClient =
+				{
+					Returns =
+					{
+						{
+							Type = "boolean",
+						},
+					},
+					Notes = "Returns true if the client is modded with Forge.",
+				},
 				IsUUIDOnline =
 				{
 					IsStatic = true,
@@ -11892,6 +11912,25 @@ end
 					},
 					Notes = "Returns true if the specified player is queued to be transferred to a World.",
 				},
+				RegisterForgeMod =
+				{
+					Params =
+					{
+						{
+							Name = "ModName",
+							Type = "string",
+						},
+						{
+							Name = "ModVersion",
+							Type = "string",
+						},
+						{
+							Name = "ProtocolVersionNumber",
+							Type = "number",
+						},
+					},
+					Notes = "Add a Forge mod name/version to the server ping list.",
+				},
 				SetMaxPlayers =
 				{
 					Params =
@@ -11913,6 +11952,21 @@ end
 					},
 					Notes = "Returns true iff the server is set to authenticate players (\"online mode\").",
 				},
+				UnregisterForgeMod =
+				{
+					Params =
+					{
+						{
+							Name = "ModName",
+							Type = "string",
+						},
+						{
+							Name = "ProtocolVersionNumber",
+							Type = "number",
+						},
+					},
+					Notes = "Remove a Forge mod name/version from the server ping list.",
+				},
 			},
 		},
 		cStringCompression =
diff --git a/Server/Plugins/APIDump/Classes/Plugins.lua b/Server/Plugins/APIDump/Classes/Plugins.lua
index e22f4e3a0..6c9df7902 100644
--- a/Server/Plugins/APIDump/Classes/Plugins.lua
+++ b/Server/Plugins/APIDump/Classes/Plugins.lua
@@ -796,6 +796,10 @@ cPluginManager.AddHook(cPluginManager.HOOK_CHAT, OnChatMessage);
 			{
 				Notes = "Called when a Login packet is sent to the client, before the client is queued for authentication.",
 			},
+			HOOK_LOGIN_FORGE =
+			{
+				Notes = "Called when a Forge client has sent its ModList to the server, during the login handshake.",
+			},
 			HOOK_PLAYER_ANIMATION =
 			{
 				Notes = "Called when a client send the Animation packet.",
diff --git a/src/Bindings/ManualBindings.cpp b/src/Bindings/ManualBindings.cpp
index c87e9ed20..ee9cb61e9 100644
--- a/src/Bindings/ManualBindings.cpp
+++ b/src/Bindings/ManualBindings.cpp
@@ -33,6 +33,7 @@
 #include "../HTTP/UrlParser.h"
 #include "../Item.h"
 #include "../LineBlockTracer.h"
+#include "../Server.h"
 #include "../Root.h"
 #include "../StringCompression.h"
 #include "../WebAdmin.h"
@@ -2365,6 +2366,27 @@ static int tolua_cClientHandle_SendPluginMessage(lua_State * L)
 
 
 
+static int tolua_cClientHandle_GetForgeMods(lua_State * L)
+{
+	cLuaState S(L);
+	if (
+		!S.CheckParamSelf("cClientHandle") ||
+		!S.CheckParamEnd(2)
+	)
+	{
+		return 0;
+	}
+	cClientHandle * Client;
+	S.GetStackValue(1, Client);
+
+	S.Push(Client->GetForgeMods());
+	return 1;
+}
+
+
+
+
+
 static int tolua_cClientHandle_GetUUID(lua_State * tolua_S)
 {
 	// Check the params:
@@ -3399,6 +3421,37 @@ static int tolua_cRoot_GetFurnaceRecipe(lua_State * tolua_S)
 
 
 
+static int tolua_cServer_RegisterForgeMod(lua_State * a_LuaState)
+{
+	cLuaState L(a_LuaState);
+	if (
+		!L.CheckParamSelf("cServer") ||
+		!L.CheckParamString(2, 3) ||
+		!L.CheckParamNumber(4) ||
+		!L.CheckParamEnd(5)
+	)
+	{
+		return 0;
+	}
+
+	cServer * Server;
+	AString Name, Version;
+	UInt32 Protocol;
+	L.GetStackValues(1, Server, Name, Version, Protocol);
+
+	if (!Server->RegisterForgeMod(Name, Version, Protocol))
+	{
+		tolua_error(L, "duplicate Forge mod name registration", nullptr);
+		return 0;
+	}
+
+	return 0;
+}
+
+
+
+
+
 static int tolua_cScoreboard_GetTeamNames(lua_State * L)
 {
 	cLuaState S(L);
@@ -4007,6 +4060,8 @@ void cManualBindings::Bind(lua_State * tolua_S)
 		tolua_beginmodule(tolua_S, "cClientHandle");
 			tolua_constant(tolua_S, "MAX_VIEW_DISTANCE",   cClientHandle::MAX_VIEW_DISTANCE);
 			tolua_constant(tolua_S, "MIN_VIEW_DISTANCE",   cClientHandle::MIN_VIEW_DISTANCE);
+
+			tolua_function(tolua_S, "GetForgeMods", tolua_cClientHandle_GetForgeMods);
 			tolua_function(tolua_S, "SendPluginMessage",   tolua_cClientHandle_SendPluginMessage);
 			tolua_function(tolua_S, "GetUUID",             tolua_cClientHandle_GetUUID);
 			tolua_function(tolua_S, "GenerateOfflineUUID", tolua_cClientHandle_GenerateOfflineUUID);
@@ -4164,6 +4219,10 @@ void cManualBindings::Bind(lua_State * tolua_S)
 			tolua_function(tolua_S, "GetTeamNames",     tolua_cScoreboard_GetTeamNames);
 		tolua_endmodule(tolua_S);
 
+		tolua_beginmodule(tolua_S, "cServer");
+			tolua_function(tolua_S, "RegisterForgeMod",            tolua_cServer_RegisterForgeMod);
+		tolua_endmodule(tolua_S);
+
 		tolua_beginmodule(tolua_S, "cStringCompression");
 			tolua_function(tolua_S, "CompressStringZLIB",     tolua_CompressStringZLIB);
 			tolua_function(tolua_S, "UncompressStringZLIB",   tolua_UncompressStringZLIB);
diff --git a/src/Bindings/Plugin.h b/src/Bindings/Plugin.h
index 22e8f15e2..fc0e2b4fc 100644
--- a/src/Bindings/Plugin.h
+++ b/src/Bindings/Plugin.h
@@ -69,6 +69,7 @@ public:
 	virtual bool OnKilled                   (cEntity & a_Victim, TakeDamageInfo & a_TDI, AString & a_DeathMessage) = 0;
 	virtual bool OnKilling                  (cEntity & a_Victim, cEntity * a_Killer, TakeDamageInfo & a_TDI) = 0;
 	virtual bool OnLogin                    (cClientHandle & a_Client, UInt32 a_ProtocolVersion, const AString & a_Username) = 0;
+	virtual bool OnLoginForge               (cClientHandle & a_Client, const AStringMap & a_Mods) = 0;
 	virtual bool OnPlayerAnimation          (cPlayer & a_Player, int a_Animation) = 0;
 	virtual bool OnPlayerBreakingBlock      (cPlayer & a_Player, int a_BlockX, int a_BlockY, int a_BlockZ, char a_BlockFace, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta) = 0;
 	virtual bool OnPlayerBrokenBlock        (cPlayer & a_Player, int a_BlockX, int a_BlockY, int a_BlockZ, char a_BlockFace, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta) = 0;
diff --git a/src/Bindings/PluginLua.cpp b/src/Bindings/PluginLua.cpp
index 5af336a95..9105f2555 100644
--- a/src/Bindings/PluginLua.cpp
+++ b/src/Bindings/PluginLua.cpp
@@ -550,6 +550,15 @@ bool cPluginLua::OnLogin(cClientHandle & a_Client, UInt32 a_ProtocolVersion, con
 
 
 
+bool cPluginLua::OnLoginForge(cClientHandle & a_Client, const AStringMap & a_Mods)
+{
+	return CallSimpleHooks(cPluginManager::HOOK_LOGIN_FORGE, &a_Client, a_Mods);
+}
+
+
+
+
+
 bool cPluginLua::OnPlayerAnimation(cPlayer & a_Player, int a_Animation)
 {
 	return CallSimpleHooks(cPluginManager::HOOK_PLAYER_ANIMATION, &a_Player, a_Animation);
@@ -1059,6 +1068,7 @@ const char * cPluginLua::GetHookFnName(int a_HookType)
 		case cPluginManager::HOOK_HANDSHAKE:                    return "OnHandshake";
 		case cPluginManager::HOOK_KILLING:                      return "OnKilling";
 		case cPluginManager::HOOK_LOGIN:                        return "OnLogin";
+		case cPluginManager::HOOK_LOGIN_FORGE:                  return "OnLoginForge";
 		case cPluginManager::HOOK_PLAYER_BREAKING_BLOCK:        return "OnPlayerBreakingBlock";
 		case cPluginManager::HOOK_PLAYER_BROKEN_BLOCK:          return "OnPlayerBrokenBlock";
 		case cPluginManager::HOOK_PLAYER_EATING:                return "OnPlayerEating";
diff --git a/src/Bindings/PluginLua.h b/src/Bindings/PluginLua.h
index 4de5751e7..7904fe115 100644
--- a/src/Bindings/PluginLua.h
+++ b/src/Bindings/PluginLua.h
@@ -90,6 +90,7 @@ public:
 	virtual bool OnKilled                   (cEntity & a_Victim, TakeDamageInfo & a_TDI, AString & a_DeathMessage) override;
 	virtual bool OnKilling                  (cEntity & a_Victim, cEntity * a_Killer, TakeDamageInfo & a_TDI) override;
 	virtual bool OnLogin                    (cClientHandle & a_Client, UInt32 a_ProtocolVersion, const AString & a_Username) override;
+	virtual bool OnLoginForge               (cClientHandle & a_Client, const AStringMap & a_Mods) override;
 	virtual bool OnPlayerAnimation          (cPlayer & a_Player, int a_Animation) override;
 	virtual bool OnPlayerBreakingBlock      (cPlayer & a_Player, int a_BlockX, int a_BlockY, int a_BlockZ, char a_BlockFace, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta) override;
 	virtual bool OnPlayerBrokenBlock        (cPlayer & a_Player, int a_BlockX, int a_BlockY, int a_BlockZ, char a_BlockFace, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta) override;
diff --git a/src/Bindings/PluginManager.cpp b/src/Bindings/PluginManager.cpp
index 1d977fcde..7c4712f0f 100644
--- a/src/Bindings/PluginManager.cpp
+++ b/src/Bindings/PluginManager.cpp
@@ -789,6 +789,24 @@ bool cPluginManager::CallHookLogin(cClientHandle & a_Client, UInt32 a_ProtocolVe
 
 
 
+bool cPluginManager::CallHookLoginForge(cClientHandle & a_Client, AStringMap & a_Mods)
+{
+	FIND_HOOK(HOOK_LOGIN_FORGE)
+	VERIFY_HOOK;
+
+	for (PluginList::iterator itr = Plugins->second.begin(); itr != Plugins->second.end(); ++itr)
+	{
+		if ((*itr)->OnLoginForge(a_Client, a_Mods))
+		{
+			return true;
+		}
+	}
+	return false;
+}
+
+
+
+
 
 bool cPluginManager::CallHookPlayerAnimation(cPlayer & a_Player, int a_Animation)
 {
diff --git a/src/Bindings/PluginManager.h b/src/Bindings/PluginManager.h
index f3fc3551a..66f7d290a 100644
--- a/src/Bindings/PluginManager.h
+++ b/src/Bindings/PluginManager.h
@@ -102,6 +102,7 @@ public:
 		HOOK_KILLED,
 		HOOK_KILLING,
 		HOOK_LOGIN,
+		HOOK_LOGIN_FORGE,
 		HOOK_PLAYER_BREAKING_BLOCK,
 		HOOK_PLAYER_BROKEN_BLOCK,
 		HOOK_PLAYER_DESTROYED,
@@ -248,6 +249,7 @@ public:
 	bool CallHookKilled		      (cEntity & a_Victim, TakeDamageInfo & a_TDI, AString & a_DeathMessage);
 	bool CallHookKilling                  (cEntity & a_Victim, cEntity * a_Killer, TakeDamageInfo & a_TDI);
 	bool CallHookLogin                    (cClientHandle & a_Client, UInt32 a_ProtocolVersion, const AString & a_Username);
+	bool CallHookLoginForge               (cClientHandle & a_Client, AStringMap & a_Mods);
 	bool CallHookPlayerAnimation          (cPlayer & a_Player, int a_Animation);
 	bool CallHookPlayerBreakingBlock      (cPlayer & a_Player, int a_BlockX, int a_BlockY, int a_BlockZ, char a_BlockFace, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta);
 	bool CallHookPlayerBrokenBlock        (cPlayer & a_Player, int a_BlockX, int a_BlockY, int a_BlockZ, char a_BlockFace, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta);
diff --git a/src/ClientHandle.cpp b/src/ClientHandle.cpp
index caa2d8fd8..dbd6d4b4e 100644
--- a/src/ClientHandle.cpp
+++ b/src/ClientHandle.cpp
@@ -64,6 +64,7 @@ float cClientHandle::FASTBREAK_PERCENTAGE;
 
 cClientHandle::cClientHandle(const AString & a_IPString, int a_ViewDistance) :
 	m_LastSentDimension(dimNotSet),
+	m_ForgeHandshake(this),
 	m_CurrentViewDistance(a_ViewDistance),
 	m_RequestedViewDistance(a_ViewDistance),
 	m_IPString(a_IPString),
@@ -320,7 +321,6 @@ void cClientHandle::Authenticate(const AString & a_Name, const cUUID & a_UUID, c
 	// Atomically increment player count (in server thread)
 	cRoot::Get()->GetServer()->PlayerCreated();
 
-	cWorld * World;
 	{
 		cCSLock lock(m_CSState);
 		/*
@@ -351,6 +351,25 @@ void cClientHandle::Authenticate(const AString & a_Name, const cUUID & a_UUID, c
 		// Send login success (if the protocol supports it):
 		m_Protocol->SendLoginSuccess();
 
+		if (m_ForgeHandshake.m_IsForgeClient)
+		{
+			m_ForgeHandshake.BeginForgeHandshake(a_Name, a_UUID, a_Properties);
+		}
+		else
+		{
+			FinishAuthenticate(a_Name, a_UUID, a_Properties);
+		}
+	}
+}
+
+
+
+
+
+void cClientHandle::FinishAuthenticate(const AString & a_Name, const cUUID & a_UUID, const Json::Value & a_Properties)
+{
+	cWorld * World;
+	{
 		// Spawn player (only serversided, so data is loaded)
 		m_PlayerPtr = cpp14::make_unique<cPlayer>(m_Self, GetUsername());
 		m_Player = m_PlayerPtr.get();
@@ -854,6 +873,10 @@ void cClientHandle::HandlePluginMessage(const AString & a_Channel, const AString
 	{
 		UnregisterPluginChannels(BreakApartPluginChannels(a_Message));
 	}
+	else if (a_Channel == "FML|HS")
+	{
+		m_ForgeHandshake.DataReceived(this, a_Message.c_str(), a_Message.size());
+	}
 	else if (!HasPluginChannel(a_Channel))
 	{
 		// Ignore if client sent something but didn't register the channel first
diff --git a/src/ClientHandle.h b/src/ClientHandle.h
index 09188f2ae..4a4898179 100644
--- a/src/ClientHandle.h
+++ b/src/ClientHandle.h
@@ -16,6 +16,7 @@
 #include "json/json.h"
 #include "ChunkSender.h"
 #include "EffectID.h"
+#include "Protocol/ForgeHandshake.h"
 #include "UUID.h"
 
 
@@ -255,8 +256,26 @@ public:  // tolua_export
 	/** Returns the client brand received in the MC|Brand plugin message or set by a plugin. */
 	const AString & GetClientBrand(void) const { return m_ClientBrand; }
 
+	/** Returns the Forge mods installed on the client. */
+	const AStringMap & GetForgeMods(void) const { return m_ForgeMods; }
+
+	/** Returns true if the client is modded with Forge. */
+	bool IsForgeClient(void) const { return m_ForgeHandshake.m_IsForgeClient; }
+
 	// tolua_end
 
+	/** Add the Forge mod list to the server ping response. */
+	void ForgeAugmentServerListPing(Json::Value & a_Response)
+	{
+		m_ForgeHandshake.AugmentServerListPing(a_Response);
+	}
+
+	/** Mark a client connection as using Forge. Set by the protocol. */
+	void SetIsForgeClient()
+	{
+		m_ForgeHandshake.m_IsForgeClient = true;
+	}
+
 	/** Returns true if the client wants the chunk specified to be sent (in m_ChunksToSend) */
 	bool WantsSendChunk(int a_ChunkX, int a_ChunkZ);
 
@@ -375,10 +394,17 @@ private:
 
 	friend class cServer;  // Needs access to SetSelf()
 
+	friend class cForgeHandshake;   // Needs access to FinishAuthenticate()
 
 	/** The type used for storing the names of registered plugin channels. */
 	typedef std::set<AString> cChannels;
 
+	/** Forge handshake state machine. */
+	cForgeHandshake m_ForgeHandshake;
+
+	/** Forge mods and versions installed on this client. */
+	AStringMap m_ForgeMods;
+
 	/** The actual view distance used, the minimum of client's requested view distance and world's max view distance. */
 	int m_CurrentViewDistance;
 
@@ -526,6 +552,9 @@ private:
 
 	float m_BreakProgress;
 
+	/** Finish logging the user in after authenticating. */
+	void FinishAuthenticate(const AString & a_Name, const cUUID & a_UUID, const Json::Value & a_Properties);
+
 	/** Returns true if the rate block interactions is within a reasonable limit (bot protection) */
 	bool CheckBlockInteractionsRate(void);
 
diff --git a/src/Protocol/CMakeLists.txt b/src/Protocol/CMakeLists.txt
index f21c81f83..00ffeb255 100644
--- a/src/Protocol/CMakeLists.txt
+++ b/src/Protocol/CMakeLists.txt
@@ -5,6 +5,7 @@ include_directories ("${PROJECT_SOURCE_DIR}/../")
 SET (SRCS
 	Authenticator.cpp
 	ChunkDataSerializer.cpp
+	ForgeHandshake.cpp
 	MojangAPI.cpp
 	Packetizer.cpp
 	Protocol_1_8.cpp
@@ -18,6 +19,7 @@ SET (SRCS
 SET (HDRS
 	Authenticator.h
 	ChunkDataSerializer.h
+	ForgeHandshake.h
 	MojangAPI.h
 	Packetizer.h
 	Protocol.h
diff --git a/src/Protocol/ForgeHandshake.cpp b/src/Protocol/ForgeHandshake.cpp
new file mode 100644
index 000000000..48b89baf4
--- /dev/null
+++ b/src/Protocol/ForgeHandshake.cpp
@@ -0,0 +1,363 @@
+
+// ForgeHandshake.cpp
+
+// Implements Forge protocol handshaking
+
+#include "Globals.h"
+#include "ForgeHandshake.h"
+#include "json/json.h"
+#include "../Server.h"
+#include "../ByteBuffer.h"
+#include "../Bindings/PluginManager.h"
+#include "../ClientHandle.h"
+#include "../Root.h"
+
+
+/** Discriminator byte values prefixing the FML|HS packets to determine their type. */
+namespace Discriminator
+{
+	static const Int8 ServerHello = 0;
+	static const Int8 ClientHello = 1;
+	static const Int8 ModList = 2;
+	static const Int8 RegistryData = 3;
+	// static const Int8 HandshakeReset = -2;
+	static const Int8 HandshakeAck = -1;
+}
+
+/** Client handshake state phases. */
+namespace ClientPhase
+{
+	static const Int8 WAITINGSERVERDATA = 2;
+	static const Int8 WAITINGSERVERCOMPLETE = 3;
+	static const Int8 PENDINGCOMPLETE = 4;
+	static const Int8 COMPLETE = 5;
+}
+
+/** Server handshake state phases. */
+namespace ServerPhase
+{
+	static const Int8 WAITINGCACK = 2;
+	static const Int8 COMPLETE = 3;
+}
+
+
+
+
+
+cForgeHandshake::cForgeHandshake(cClientHandle *a_Client) :
+	m_IsForgeClient(false),
+	m_Errored(false),
+	m_Client(a_Client)
+{
+}
+
+
+
+
+
+void cForgeHandshake::SetError(const AString & message)
+{
+	LOGD("Forge handshake error: %s", message.c_str());
+	m_Errored = true;
+}
+
+
+
+
+
+void cForgeHandshake::AugmentServerListPing(Json::Value & a_ResponseValue)
+{
+	auto ProtocolVersion = m_Client->GetProtocolVersion();
+	auto & Mods = cRoot::Get()->GetServer()->GetRegisteredForgeMods(ProtocolVersion);
+
+	if (Mods.empty())
+	{
+		return;
+	}
+
+	LOGD("Received server ping from version: %d", ProtocolVersion);
+
+	Json::Value Modinfo;
+	Modinfo["type"] = "FML";
+
+	Json::Value ModList(Json::arrayValue);
+	for (auto & item: Mods)
+	{
+		Json::Value Mod;
+		Mod["modid"] = item.first;
+		Mod["version"] = item.second;
+		ModList.append(Mod);
+	}
+	Modinfo["modList"] = ModList;
+
+	a_ResponseValue["modinfo"] = Modinfo;
+}
+
+
+
+
+
+void cForgeHandshake::BeginForgeHandshake(const AString & a_Name, const cUUID & a_UUID, const Json::Value & a_Properties)
+{
+	ASSERT(m_IsForgeClient);
+
+	m_Name = a_Name;
+	m_UUID = a_UUID;
+	m_Properties = a_Properties;
+
+	static const std::array<AString, 5> Channels{{ "FML|HS", "FML", "FML|MP", "FML", "FORGE" }};
+	AString ChannelsString;
+	for (auto & Channel: Channels)
+	{
+		ChannelsString.append(Channel);
+		ChannelsString.push_back('\0');
+	}
+
+	m_Client->SendPluginMessage("REGISTER", ChannelsString);
+	SendServerHello();
+}
+
+
+
+
+
+void cForgeHandshake::SendServerHello()
+{
+	AString Message;
+	cByteBuffer Buf(6);
+	// Discriminator | Byte | Always 0 for ServerHello
+	Buf.WriteBEInt8(Discriminator::ServerHello);
+	// FML protocol Version | Byte | Determined from NetworkRegistery. Currently 2.
+	Buf.WriteBEInt8(2);
+	// Dimension TODO
+	Buf.WriteBEInt32(0);
+	Buf.ReadAll(Message);
+
+	m_Client->SendPluginMessage("FML|HS", Message);
+}
+
+
+
+
+
+AStringMap cForgeHandshake::ParseModList(const char * a_Data, size_t a_Size)
+{
+	AStringMap Mods;
+
+	if (a_Size < 4)
+	{
+		SetError(Printf("ParseModList invalid packet, missing length (size = " SIZE_T_FMT ")", a_Size));
+		return Mods;
+	}
+
+	cByteBuffer Buf(a_Size);
+	Buf.Write(a_Data, a_Size);
+	UInt32 NumMods;
+	if (!Buf.ReadVarInt32(NumMods))
+	{
+		SetError("ParseModList failed to read mod count");
+		return Mods;
+	}
+
+	for (UInt32 i = 0; i < NumMods; ++i)
+	{
+		AString Name, Version;
+		if (!Buf.ReadVarUTF8String(Name))
+		{
+			SetError(Printf("ParseModList failed to read mod name at i = %d", i));
+			break;
+		}
+		if (!Buf.ReadVarUTF8String(Version))
+		{
+			SetError(Printf("ParseModList failed to read mod version at i = %d", i));
+			break;
+		}
+		Mods.insert({Name, Version});
+	}
+
+	return Mods;
+}
+
+
+
+
+void cForgeHandshake::HandleClientHello(cClientHandle * a_Client, const char * a_Data, size_t a_Size)
+{
+	if (a_Size == 2)
+	{
+		int FmlProtocolVersion = a_Data[1];
+		LOGD("Received ClientHello with FML protocol version %d", FmlProtocolVersion);
+		if (FmlProtocolVersion != 2)
+		{
+			SetError(Printf("Unsupported FML client protocol version received in ClientHello: %d", FmlProtocolVersion));
+		}
+	}
+	else
+	{
+		SetError(Printf("Received unexpected length of ClientHello: " SIZE_T_FMT, a_Size));
+	}
+}
+
+
+
+
+void cForgeHandshake::HandleModList(cClientHandle * a_Client, const char * a_Data, size_t a_Size)
+{
+	LOGD("Received ModList");
+
+	auto ClientMods = ParseModList(a_Data + 1, a_Size - 1);
+	AString ClientModsString;
+	for (auto & item: ClientMods)
+	{
+		AppendPrintf(ClientModsString, "%s@%s, ", item.first.c_str(), item.second.c_str());
+	}
+
+	LOG("Client connected with " SIZE_T_FMT " mods: %s", ClientMods.size(), ClientModsString.c_str());
+
+	m_Client->m_ForgeMods = ClientMods;
+
+	// Let the plugins know about this event, they may refuse the player:
+	if (cRoot::Get()->GetPluginManager()->CallHookLoginForge(*a_Client, ClientMods))
+	{
+		SetError("Modded client refused by plugin");
+		return;
+	}
+
+	// Send server ModList
+
+	// Send server-side Forge mods registered by plugins
+	const auto & ServerMods = m_Client->GetForgeMods();
+
+	const auto ModCount = ServerMods.size();
+
+	cByteBuffer Buf(256 * ModCount);
+
+	Buf.WriteBEInt8(Discriminator::ModList);
+	Buf.WriteVarInt32(static_cast<UInt32>(ModCount));
+	for (const auto & item: ServerMods)
+	{
+		Buf.WriteVarUTF8String(item.first);   // name
+		Buf.WriteVarUTF8String(item.second);  // version
+	}
+	AString ServerModList;
+	Buf.ReadAll(ServerModList);
+
+	m_Client->SendPluginMessage("FML|HS", ServerModList);
+}
+
+
+
+
+void cForgeHandshake::HandleHandshakeAck(cClientHandle * a_Client, const char * a_Data, size_t a_Size)
+{
+	if (a_Size != 2)
+	{
+		SetError(Printf("Unexpected HandshakeAck packet length: " SIZE_T_FMT "", a_Size));
+		return;
+	}
+
+	auto Phase = a_Data[1];
+	LOGD("Received client HandshakeAck with phase = %d", Phase);
+
+	switch (Phase)
+	{
+		case ClientPhase::WAITINGSERVERDATA:
+		{
+			cByteBuffer Buf(1024);
+			Buf.WriteBEInt8(Discriminator::RegistryData);
+
+			// TODO: send real registry data
+			bool HasMore = false;
+			AString RegistryName = "potions";
+			UInt32 NumIDs = 0;
+			UInt32 NumSubstitutions = 0;
+			UInt32 NumDummies = 0;
+
+			Buf.WriteBool(HasMore);
+			Buf.WriteVarUTF8String(RegistryName);
+			Buf.WriteVarInt32(NumIDs);
+			Buf.WriteVarInt32(NumSubstitutions);
+			Buf.WriteVarInt32(NumDummies);
+
+			AString RegistryData;
+			Buf.ReadAll(RegistryData);
+			m_Client->SendPluginMessage("FML|HS", RegistryData);
+			break;
+		}
+
+		case ClientPhase::WAITINGSERVERCOMPLETE:
+		{
+			LOGD("Client finished receiving registry data; acknowledging");
+
+			AString Ack;
+			Ack.push_back(Discriminator::HandshakeAck);
+			Ack.push_back(ServerPhase::WAITINGCACK);
+			m_Client->SendPluginMessage("FML|HS", Ack);
+			break;
+		}
+
+		case ClientPhase::PENDINGCOMPLETE:
+		{
+			LOGD("Client is pending completion; sending complete ack");
+
+			AString Ack;
+			Ack.push_back(Discriminator::HandshakeAck);
+			Ack.push_back(ServerPhase::COMPLETE);
+			m_Client->SendPluginMessage("FML|HS", Ack);
+
+			break;
+		}
+
+		case ClientPhase::COMPLETE:
+		{
+			// Now finish logging in
+			m_Client->FinishAuthenticate(m_Name, m_UUID, m_Properties);
+			break;
+		}
+
+		default:
+		{
+			SetError(Printf("Received unknown phase in Forge handshake acknowledgement: %d", Phase));
+			break;
+		}
+	}
+}
+
+
+
+
+
+void cForgeHandshake::DataReceived(cClientHandle * a_Client, const char * a_Data, size_t a_Size)
+{
+	if (!m_IsForgeClient)
+	{
+		SetError(Printf("Received unexpected Forge data from non-Forge client (" SIZE_T_FMT " bytes)", a_Size));
+		return;
+	}
+	if (m_Errored)
+	{
+		LOGD("Received unexpected Forge data when in errored state, ignored");
+		return;
+	}
+
+	if (a_Size <= 1)
+	{
+		SetError(Printf("Received unexpectedly short Forge data (" SIZE_T_FMT " bytes)", a_Size));
+		return;
+	}
+
+	auto Discriminator = a_Data[0];
+
+	switch (Discriminator)
+	{
+		case Discriminator::ClientHello:  HandleClientHello(a_Client, a_Data, a_Size); break;
+		case Discriminator::ModList:      HandleModList(a_Client, a_Data, a_Size); break;
+		case Discriminator::HandshakeAck: HandleHandshakeAck(a_Client, a_Data, a_Size); break;
+
+		default:
+		{
+			SetError(Printf("Unexpected Forge packet %d received", Discriminator));
+			return;
+		}
+	}
+}
diff --git a/src/Protocol/ForgeHandshake.h b/src/Protocol/ForgeHandshake.h
new file mode 100644
index 000000000..f7be9e958
--- /dev/null
+++ b/src/Protocol/ForgeHandshake.h
@@ -0,0 +1,60 @@
+
+// ForgeHandshake.h
+
+// Implements Forge protocol handshaking
+
+#pragma once
+
+#include <stddef.h>
+#include "UUID.h"
+#include "json/json.h"
+
+// fwd:
+class cClientHandle;
+
+
+
+
+
+class cForgeHandshake
+{
+public:
+	/** True if the client advertised itself as a Forge client. */
+	bool m_IsForgeClient;
+
+	cForgeHandshake(cClientHandle * client);
+
+	/** Add the registered Forge mods to the server ping list packet. */
+	void AugmentServerListPing(Json::Value & ResponseValue);
+
+	/** Begin the Forge Modloader Handshake (FML|HS) sequence. */
+	void BeginForgeHandshake(const AString & a_Name, const cUUID & a_UUID, const Json::Value & a_Properties);
+
+	/** Send the ServerHello packet in the Forge handshake. */
+	void SendServerHello();
+
+	/** Process received data from the client advancing the Forge handshake. */
+	void DataReceived(cClientHandle * a_Client, const char * a_Data, size_t a_Size);
+
+private:
+	/** True if the Forge handshake is in an errored state. */
+	bool m_Errored;
+
+	/** The client handle undergoing this Forge handshake. */
+	cClientHandle * m_Client;
+
+	/** Values saved from BeginForgeHandshake() for continuing the normal handshake after Forge completes. */
+	AString m_Name;
+	cUUID m_UUID;
+	Json::Value m_Properties;
+
+	void HandleClientHello(cClientHandle * a_Client, const char * a_Data, size_t a_Size);
+	void HandleModList(cClientHandle * a_Client, const char * a_Data, size_t a_Size);
+	void HandleHandshakeAck(cClientHandle * a_Client, const char * a_Data, size_t a_Size);
+
+	/** Set errored state to prevent further handshake message processing. */
+	void SetError(const AString & message);
+
+	/** Parse the client ModList packet of installed Forge mods and versions. */
+	AStringMap ParseModList(const char * a_Data, size_t a_Size);
+};
diff --git a/src/Protocol/Protocol_1_10.cpp b/src/Protocol/Protocol_1_10.cpp
index 67b76872a..7f86d4bdc 100644
--- a/src/Protocol/Protocol_1_10.cpp
+++ b/src/Protocol/Protocol_1_10.cpp
@@ -15,6 +15,7 @@ Implements the 1.10 protocol classes:
 
 #include "../Root.h"
 #include "../Server.h"
+#include "../ClientHandle.h"
 
 #include "../WorldStorage/FastNBT.h"
 
@@ -346,6 +347,7 @@ void cProtocol_1_10_0::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
diff --git a/src/Protocol/Protocol_1_11.cpp b/src/Protocol/Protocol_1_11.cpp
index c562503bd..b9b6e9ac3 100644
--- a/src/Protocol/Protocol_1_11.cpp
+++ b/src/Protocol/Protocol_1_11.cpp
@@ -586,6 +586,7 @@ void cProtocol_1_11_0::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
@@ -1209,6 +1210,7 @@ void cProtocol_1_11_1::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
diff --git a/src/Protocol/Protocol_1_12.cpp b/src/Protocol/Protocol_1_12.cpp
index 43ab682eb..a8e38a4e0 100644
--- a/src/Protocol/Protocol_1_12.cpp
+++ b/src/Protocol/Protocol_1_12.cpp
@@ -399,6 +399,7 @@ void cProtocol_1_12::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
@@ -1667,6 +1668,7 @@ void cProtocol_1_12_1::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
diff --git a/src/Protocol/Protocol_1_8.cpp b/src/Protocol/Protocol_1_8.cpp
index 0e7abfd7a..c77af1029 100644
--- a/src/Protocol/Protocol_1_8.cpp
+++ b/src/Protocol/Protocol_1_8.cpp
@@ -2169,6 +2169,7 @@ void cProtocol_1_8_0::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
diff --git a/src/Protocol/Protocol_1_9.cpp b/src/Protocol/Protocol_1_9.cpp
index 7fc6cf5f1..c6e007984 100644
--- a/src/Protocol/Protocol_1_9.cpp
+++ b/src/Protocol/Protocol_1_9.cpp
@@ -124,21 +124,46 @@ cProtocol_1_9_0::cProtocol_1_9_0(cClientHandle * a_Client, const AString & a_Ser
 	m_IsEncrypted(false)
 {
 
-	// BungeeCord handling:
-	// If BC is setup with ip_forward == true, it sends additional data in the login packet's ServerAddress field:
-	// hostname\00ip-address\00uuid\00profile-properties-as-json
 	AStringVector Params;
-	if (cRoot::Get()->GetServer()->ShouldAllowBungeeCord() && SplitZeroTerminatedStrings(a_ServerAddress, Params) && (Params.size() == 4))
+	SplitZeroTerminatedStrings(a_ServerAddress, Params);
+
+	if (Params.size() >= 2)
 	{
-		LOGD("Player at %s connected via BungeeCord", Params[1].c_str());
 		m_ServerAddress = Params[0];
-		m_Client->SetIPString(Params[1]);
 
-		cUUID UUID;
-		UUID.FromString(Params[2]);
-		m_Client->SetUUID(UUID);
+		if (Params[1] == "FML")
+		{
+			LOGD("Forge client connected!");
+			m_Client->SetIsForgeClient();
+		}
+		else if (Params.size() == 4)
+		{
+			if (cRoot::Get()->GetServer()->ShouldAllowBungeeCord())
+			{
+				// BungeeCord handling:
+				// If BC is setup with ip_forward == true, it sends additional data in the login packet's ServerAddress field:
+				// hostname\00ip-address\00uuid\00profile-properties-as-json
+
+				LOGD("Player at %s connected via BungeeCord", Params[1].c_str());
+
+				m_Client->SetIPString(Params[1]);
+
+				cUUID UUID;
+				UUID.FromString(Params[2]);
+				m_Client->SetUUID(UUID);
 
-		m_Client->SetProperties(Params[3]);
+				m_Client->SetProperties(Params[3]);
+			}
+			else
+			{
+				LOG("BungeeCord is disabled, but client sent additional data, set AllowBungeeCord=1 if you want to allow it");
+			}
+		}
+		else
+		{
+			LOG("Unknown additional data sent in server address (BungeeCord/FML?): " SIZE_T_FMT " parameters", Params.size());
+			// TODO: support FML + BungeeCord? (what parameters does it send in that case?) https://github.com/SpigotMC/BungeeCord/issues/899
+		}
 	}
 
 	// Create the comm log file, if so requested:
@@ -2194,6 +2219,7 @@ void cProtocol_1_9_0::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
@@ -4204,6 +4230,7 @@ void cProtocol_1_9_1::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
@@ -4261,6 +4288,7 @@ void cProtocol_1_9_2::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
@@ -4318,6 +4346,7 @@ void cProtocol_1_9_4::HandlePacketStatusRequest(cByteBuffer & a_ByteBuffer)
 	ResponseValue["version"] = Version;
 	ResponseValue["players"] = Players;
 	ResponseValue["description"] = Description;
+	m_Client->ForgeAugmentServerListPing(ResponseValue);
 	if (!Favicon.empty())
 	{
 		ResponseValue["favicon"] = Printf("data:image/png;base64,%s", Favicon.c_str());
diff --git a/src/Server.cpp b/src/Server.cpp
index 70d594f2d..6ddb14ae5 100644
--- a/src/Server.cpp
+++ b/src/Server.cpp
@@ -235,6 +235,56 @@ bool cServer::InitServer(cSettingsRepositoryInterface & a_Settings, bool a_Shoul
 
 
 
+bool cServer::RegisterForgeMod(const AString & a_ModName, const AString & a_ModVersion, UInt32 a_ProtocolVersionNumber)
+{
+	auto & Mods = RegisteredForgeMods(a_ProtocolVersionNumber);
+
+	return Mods.insert({a_ModName, a_ModVersion}).second;
+}
+
+
+
+
+
+void cServer::UnregisterForgeMod(const AString & a_ModName, UInt32 a_ProtocolVersionNumber)
+{
+	auto & Mods = RegisteredForgeMods(a_ProtocolVersionNumber);
+
+	auto it = Mods.find(a_ModName);
+	if (it != Mods.end())
+	{
+		Mods.erase(it);
+	}
+}
+
+
+
+
+AStringMap & cServer::RegisteredForgeMods(const UInt32 a_Protocol)
+{
+	auto it = m_ForgeModsByVersion.find(a_Protocol);
+
+	if (it == m_ForgeModsByVersion.end())
+	{
+		AStringMap mods;
+		m_ForgeModsByVersion.insert({a_Protocol, mods});
+		return m_ForgeModsByVersion.find(a_Protocol)->second;
+	}
+
+	return it->second;
+}
+
+
+
+
+const AStringMap & cServer::GetRegisteredForgeMods(const UInt32 a_Protocol)
+{
+	return RegisteredForgeMods(a_Protocol);
+}
+
+
+
+
 bool cServer::IsPlayerInQueue(AString a_Username)
 {
 	cCSLock Lock(m_CSClients);
diff --git a/src/Server.h b/src/Server.h
index 633f6de70..ffdee64d9 100644
--- a/src/Server.h
+++ b/src/Server.h
@@ -71,6 +71,16 @@ public:
 	size_t GetNumPlayers(void) const { return m_PlayerCount; }
 	void SetMaxPlayers(size_t a_MaxPlayers) { m_MaxPlayers = a_MaxPlayers; }
 
+	// tolua_end
+
+	/** Add a Forge mod to the server ping list. */
+	bool RegisterForgeMod(const AString & a_ModName, const AString & a_ModVersion, UInt32 a_ProtocolVersionNumber);
+
+	// tolua_begin
+
+	/** Remove a Forge mod to the server ping list. */
+	void UnregisterForgeMod(const AString & a_ModName, UInt32 a_ProtocolVersionNumber);
+
 	/** Check if the player is queued to be transferred to a World.
 	Returns true is Player is found in queue. */
 	bool IsPlayerInQueue(AString a_Username);
@@ -145,6 +155,9 @@ public:
 	from the settings. */
 	bool ShouldAllowMultiWorldTabCompletion(void) const { return m_ShouldAllowMultiWorldTabCompletion; }
 
+	/** Get the Forge mods (map of ModName -> ModVersionString) registered for a given protocol. */
+	const AStringMap & GetRegisteredForgeMods(const UInt32 a_Protocol);
+
 private:
 
 	friend class cRoot;  // so cRoot can create and destroy cServer
@@ -202,6 +215,9 @@ private:
 	size_t m_MaxPlayers;
 	bool m_bIsHardcore;
 
+	/** Map of protocol version to Forge mods (map of ModName -> ModVersionString) */
+	std::map<UInt32, AStringMap> m_ForgeModsByVersion;
+
 	/** True - allow same username to login more than once False - only once */
 	bool m_bAllowMultiLogin;
 
@@ -241,6 +257,9 @@ private:
 
 	cServer(void);
 
+	/** Get the Forge mods registered for a given protocol, for modification */
+	AStringMap & RegisteredForgeMods(const UInt32 a_Protocol);
+
 	/** Loads, or generates, if missing, RSA keys for protocol encryption */
 	void PrepareKeys(void);