Always use STUN for hosting games using the lobby

This makes using STUN mandatory for games hosted using the multiplayer
lobby. The motivation for that is a reduction in complexity, because
right now if STUN is disabled we use a home-grown STUN-like logic, which
got implemented before Pyrogenesis got STUN support.

That home-grown logic relies on a custom ejabberd module (mod_ipstamp),
which inserts the external IP-address of a host in the response messages
when a host registers a game. Originally mod_ipstamp was also used to
inform all potential players of a hosts IP-address, however that has
already been removed to let hosts to only share their IP-address with
players actually joining their game.

Removing the home-grown logic and instead always relying on STUN removes
complexity in Pyrogenesis and the lobby server and also eases hosting
games for players, as they don't have to figure out anymore whether they
need to enable STUN or not.

These changes shouldn't negatively impact the ability of Pyrogenesis to
handle different types of NAT or broken networks. There is one
difference though: While the custom logic using mod_ipstamp utilized TCP
as transport protocol, the STUN implementation in Pyrogenesis currently
uses UDP. That doesn't allow hosts with UDP-connectivity issues to
resolve their external IP-address anymore, however without
UDP-connectivity they aren't able to successfully host games anyway, as
the actual game updates are transferred using UDP as well.

binaries/data/config/default.cfg

@@ -519,8 +519,6 @@ rememberpassword = true             ; Whether to store the encrypted password in
 gamerating = false                  ; Show the average rating of the participating players in a column of the gamelist
 
 [lobby.stun]
-enabled = true                       ; The STUN protocol allows hosting games without configuring the firewall and router.
-                                     ; If STUN is disabled, the game relies on direct connection, UPnP and port forwarding.
 server = "lobby.wildfiregames.com"   ; Address of the STUN server.
 port = 3478                          ; Port of the STUN server.
 delay = 10                           ; Duration in milliseconds that is waited between checking for retrieved STUN responses.

binaries/data/mods/public/autostart/autostart_host.js

@@ -13,8 +13,8 @@ class AutoStartHost
 			const playerName = cmdLineArgs['autostart-playername'] || "anonymous";
 			const port = +(cmdLineArgs['autostart-port'] ?? 5073);
 
-			// Stun and password not implemented for autostart.
-			Engine.StartNetworkHost(playerName, port, false, "", !('autostart-disable-replay' in cmdLineArgs));
+			// Password not implemented for autostart.
+			Engine.StartNetworkHost(playerName, port, "", !('autostart-disable-replay' in cmdLineArgs));
 		}
 		catch (e)
 		{

binaries/data/mods/public/gui/gamesetup_mp/gamesetup_mp.js

@@ -50,15 +50,12 @@ function init(attribs)
 	case "host":
 	{
 		let hasXmppClient = Engine.HasXmppClient();
-		Engine.GetGUIObjectByName("hostSTUNWrapper").hidden = !hasXmppClient;
 		Engine.GetGUIObjectByName("hostPasswordWrapper").hidden = !hasXmppClient;
 		if (hasXmppClient)
 		{
 			Engine.GetGUIObjectByName("hostPlayerName").caption = attribs.name;
 			Engine.GetGUIObjectByName("hostServerName").caption =
 				sprintf(translate("%(name)s's game"), { "name": attribs.name });
-
-			Engine.GetGUIObjectByName("useSTUN").checked = Engine.ConfigDB_GetValue("user", "lobby.stun.enabled") == "true";
 		}
 
 		switchSetupPage("pageHost");
@@ -387,12 +384,10 @@ function startHost(playername, servername, port, password, loadSavedGame)
 		return false;
 	}
 
-	let useSTUN = Engine.HasXmppClient() && Engine.GetGUIObjectByName("useSTUN").checked;
-
 	try
 	{
 		Engine.StartNetworkHost(playername + (g_UserRating ? " (" + g_UserRating + ")" : ""), port,
-			useSTUN, password, loadSavedGame, true);
+			password, loadSavedGame, true);
 	}
 	catch (e)
 	{

binaries/data/mods/public/gui/gamesetup_mp/gamesetup_mp.xml

@@ -115,15 +115,6 @@
 					</action>
 				</object>
 			</object>
-
-			<object name="hostSTUNWrapper" size="80 152 100%-20 180">
-				<object name="useSTUN" size="0 4 32 100%" type="checkbox" style="ModernTickBox">
-					<action on="Press">Engine.ConfigDB_CreateAndSaveValue("user", "lobby.stun.enabled", String(this.checked));</action>
-				</object>
-				<object type="text" size="26 0 100% 100%" style="ModernLeftLabelText">
-					<translatableAttribute id="caption">Use STUN to work around firewalls</translatableAttribute>
-				</object>
-			</object>
 		</object>
 
 		<object name="hostFeedback" type="text" style="ModernLabelText" size="50 100%-80 100%-50 100%-45" textcolor="red"/>

source/lobby/StanzaExtensions.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -298,9 +298,6 @@ ConnectionData::ConnectionData(const gloox::Tag* tag)
 	const gloox::Tag* pip = tag->findTag("connectiondata/isLocalIP");
 	if (pip)
 		m_IsLocalIP = pip->cdata();
-	const gloox::Tag* s = tag->findTag("connectiondata/useSTUN");
-	if (s)
-		m_UseSTUN = s->cdata();
 	const gloox::Tag* pw = tag->findTag("connectiondata/password");
 	if (pw)
 		m_Password = pw->cdata();
@@ -335,8 +332,6 @@ gloox::Tag* ConnectionData::tag() const
 		t->addChild(new gloox::Tag("port", m_Port));
 	if (!m_IsLocalIP.empty())
 		t->addChild(new gloox::Tag("isLocalIP", m_IsLocalIP));
-	if (!m_UseSTUN.empty())
-		t->addChild(new gloox::Tag("useSTUN", m_UseSTUN));
 	if (!m_Password.empty())
 		t->addChild(new gloox::Tag("password", m_Password));
 	if (!m_ClientSalt.empty())

source/lobby/StanzaExtensions.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -61,7 +61,6 @@ public:
 	std::string m_Ip;
 	std::string m_Port;
 	std::string m_IsLocalIP;
-	std::string m_UseSTUN;
 	std::string m_Password;
 	std::string m_ClientSalt;
 	std::string m_Error;

source/lobby/XmppClient.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -855,8 +855,8 @@ bool XmppClient::handleIq(const gloox::IQ& iq)
 				return true;
 			}
 
-			g_NetClient->SetupServerData(cd->m_Ip, stoi(cd->m_Port), !cd->m_UseSTUN.empty());
-			g_NetClient->TryToConnect(iq.from().full(), !cd->m_IsLocalIP.empty());
+			g_NetClient->SetupServerData(cd->m_Ip, stoi(cd->m_Port));
+			g_NetClient->TryToConnectWithSTUN(iq.from().full(), !cd->m_IsLocalIP.empty());
 		}
 		if (gq)
 		{
@@ -866,23 +866,6 @@ bool XmppClient::handleIq(const gloox::IQ& iq)
 				return true;
 			}
 
-			if (gq->m_Command == "register" && g_NetServer && !g_NetServer->GetUseSTUN())
-			{
-				if (gq->m_GameList.empty())
-				{
-					LOGWARNING("XmppClient: Received empty game list in response to Game Register");
-					return true;
-				}
-				std::string publicIP = gq->m_GameList.front()->findAttribute("ip");
-				if (publicIP.empty())
-				{
-					LOGWARNING("XmppClient: Received game with no IP in response to Game Register");
-					return true;
-				}
-				g_NetServer->SetConnectionData(publicIP, g_NetServer->GetPublicPort());
-				return true;
-			}
-
 			for (const gloox::Tag* const& t : m_GameList)
 				delete t;
 			m_GameList.clear();
@@ -1006,7 +989,6 @@ bool XmppClient::handleIq(const gloox::IQ& iq)
 			{
 				connectionData->m_Ip = g_NetServer->GetPublicIp();
 				connectionData->m_Port = std::to_string(g_NetServer->GetPublicPort());
-				connectionData->m_UseSTUN = g_NetServer->GetUseSTUN() ? "true" : "";
 				connectionData->m_IsLocalIP = "";
 			}
 			else
@@ -1016,7 +998,6 @@ bool XmppClient::handleIq(const gloox::IQ& iq)
 				{
 					connectionData->m_Ip = ip;
 					connectionData->m_Port = std::to_string(g_NetServer->GetLocalPort());
-					connectionData->m_UseSTUN = "";
 					connectionData->m_IsLocalIP = "true";
 				}
 				else

source/network/NetClient.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -182,13 +182,12 @@ void CNetClient::SetupConnectionViaLobby()
 	g_XmppClient->SendIqGetConnectionData(m_HostJID, m_Password, m_UserName.ToUTF8(), false);
 }
 
-void CNetClient::SetupServerData(CStr address, u16 port, bool stun)
+void CNetClient::SetupServerData(CStr address, u16 port)
 {
 	ENSURE(!m_Session);
 
 	m_ServerAddress = address;
 	m_ServerPort = port;
-	m_UseSTUN = stun;
 }
 
 void CNetClient::HandleGetServerDataFailed(const CStr& error)
@@ -203,8 +202,10 @@ void CNetClient::HandleGetServerDataFailed(const CStr& error)
 	);
 }
 
-bool CNetClient::TryToConnect(const CStr& hostJID, bool localNetwork)
+bool CNetClient::TryToConnectWithSTUN(const CStr& hostJID, bool localNetwork)
 {
+	ENSURE(g_XmppClient);
+
 	if (m_Session)
 		return false;
 
@@ -231,7 +232,7 @@ bool CNetClient::TryToConnect(const CStr& hostJID, bool localNetwork)
 
 	CStr ip;
 	u16 port = 0;
-	if (g_XmppClient && m_UseSTUN)
+	if (!localNetwork)
 	{
 		if (!StunClient::FindPublicIP(*enetClient, ip, port))
 		{
@@ -252,7 +253,7 @@ bool CNetClient::TryToConnect(const CStr& hostJID, bool localNetwork)
 			return true;
 		}
 	}
-	else if (g_XmppClient && localNetwork)
+	else
 	{
 		// We may need to punch a hole through the local firewall, so fetch our local IP.
 		// NB: we'll ignore failures here, and hope that the firewall will be open to connection

source/network/NetClient.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -116,7 +116,7 @@ public:
 	 * Set connection data to the remote networked server.
 	 * @param address IP address or host name to connect to
 	 */
-	void SetupServerData(CStr address, u16 port, bool stun);
+	void SetupServerData(CStr address, u16 port);
 
 	/**
 	 * Set up a connection to the remote networked server.
@@ -136,7 +136,7 @@ public:
 	 * @param localNetwork - if true, assume we are trying to connect on the local network.
 	 * @return true on success, false on connection failure
 	 */
-	bool TryToConnect(const CStr& hostJID, bool localNetwork);
+	bool TryToConnectWithSTUN(const CStr& hostJID, bool localNetwork);
 
 	/**
 	 * Destroy the connection to the server.
@@ -325,7 +325,6 @@ private:
 	CStr m_HostJID;
 	CStr m_ServerAddress;
 	u16 m_ServerPort;
-	bool m_UseSTUN;
 
 	/**
 	 * Password to join the game.

source/network/NetServer.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -1676,7 +1676,7 @@ void CNetServerWorker::SendHolePunchingMessage(const CStr& ipStr, u16 port)
 
 CNetServer::CNetServer(const bool continueSavedGame, const bool useLobbyAuth) :
 	m_Worker{new CNetServerWorker{continueSavedGame, useLobbyAuth}},
-	m_LobbyAuth(useLobbyAuth), m_UseSTUN(false), m_PublicIp(""), m_PublicPort(20595), m_Password()
+	m_LobbyAuth(useLobbyAuth), m_PublicIp(""), m_PublicPort(20595), m_Password()
 {
 }
 
@@ -1685,11 +1685,6 @@ CNetServer::~CNetServer()
 	delete m_Worker;
 }
 
-bool CNetServer::GetUseSTUN() const
-{
-	return m_UseSTUN;
-}
-
 bool CNetServer::UseLobbyAuth() const
 {
 	return m_LobbyAuth;
@@ -1718,16 +1713,8 @@ u16 CNetServer::GetLocalPort() const
 	return m_Worker->m_Host->address.port;
 }
 
-void CNetServer::SetConnectionData(const CStr& ip, const u16 port)
+bool CNetServer::SetConnectionData()
 {
-	m_PublicIp = ip;
-	m_PublicPort = port;
-	m_UseSTUN = false;
-}
-
-bool CNetServer::SetConnectionDataViaSTUN()
-{
-	m_UseSTUN = true;
 	std::lock_guard<std::mutex> lock(m_Worker->m_WorkerMutex);
 	if (!m_Worker->m_Host)
 		return false;

source/network/NetServer.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -144,10 +144,7 @@ public:
 
 	void SendHolePunchingMessage(const CStr& ip, u16 port);
 
-	void SetConnectionData(const CStr& ip, u16 port);
-	bool SetConnectionDataViaSTUN();
-
-	bool GetUseSTUN() const;
+	bool SetConnectionData();
 
 	/**
 	 * Return the externally accessible IP.
@@ -186,7 +183,6 @@ public:
 private:
 	CNetServerWorker* m_Worker;
 	const bool m_LobbyAuth;
-	bool m_UseSTUN;
 	u16 m_PublicPort;
 	CStr m_PublicIp;
 	CStr m_Password;

source/network/scripting/JSInterface_Network.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -65,7 +65,7 @@ bool HasNetClient()
 	return !!g_NetClient;
 }
 
-void StartNetworkHost(const ScriptRequest& rq, const CStrW& playerName, const u16 serverPort, bool useSTUN,
+void StartNetworkHost(const ScriptRequest& rq, const CStrW& playerName, const u16 serverPort,
 	const CStr& password, const bool continueSavedGame, bool storeReplay)
 {
 	ENSURE(!g_NetClient);
@@ -84,20 +84,12 @@ void StartNetworkHost(const ScriptRequest& rq, const CStrW& playerName, const u1
 	}
 
 	// In lobby, we send our public ip and port on request to the players who want to connect.
-	// Thus we need to know our public IP. Use STUN if that's available,
-	// otherwise, the lobby's reponse to the game registration stanza will tell us our public IP.
-	if (hasLobby)
+	// Thus we need to know our public IP and use STUN to get it.
+	if (hasLobby && !g_NetServer->SetConnectionData())
 	{
-		if (!useSTUN)
-			// Don't store IP - the lobby bot will send it later.
-			// (if a client tries to connect before it's setup, they'll be disconnected)
-			g_NetServer->SetConnectionData("", serverPort);
-		else if (!g_NetServer->SetConnectionDataViaSTUN())
-		{
-			ScriptException::Raise(rq, "Failed to host via STUN.");
-			SAFE_DELETE(g_NetServer);
-			return;
-		}
+		ScriptException::Raise(rq, "Failed to resolve public IP-address.");
+		SAFE_DELETE(g_NetServer);
+		return;
 	}
 
 	// Generate a secret to identify the host client.
@@ -134,7 +126,7 @@ void StartNetworkHost(const ScriptRequest& rq, const CStrW& playerName, const u1
 		g_NetClient->SetGamePassword(hashedPass);
 	}
 
-	g_NetClient->SetupServerData("127.0.0.1", serverPort, false);
+	g_NetClient->SetupServerData("127.0.0.1", serverPort);
 	g_NetClient->SetControllerSecret(secret);
 
 	if (!g_NetClient->SetupConnection(nullptr))
@@ -154,7 +146,7 @@ void StartNetworkJoin(const ScriptRequest& rq, const CStrW& playerName, const CS
 	g_Game = new CGame(storeReplay);
 	g_NetClient = new CNetClient(g_Game);
 	g_NetClient->SetUserName(playerName);
-	g_NetClient->SetupServerData(serverAddress, serverPort, false);
+	g_NetClient->SetupServerData(serverAddress, serverPort);
 
 	if (!g_NetClient->SetupConnection(nullptr))
 	{

source/network/tests/test_Net.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -73,7 +73,7 @@ public:
 		TS_ASSERT(server.SetupConnection(PS_DEFAULT_PORT));
 		for (CNetClient* client: clients)
 		{
-			client->SetupServerData("127.0.0.1", PS_DEFAULT_PORT, false);
+			client->SetupServerData("127.0.0.1", PS_DEFAULT_PORT);
 			TS_ASSERT(client->SetupConnection(nullptr));
 		}
 
@@ -307,7 +307,7 @@ public:
 		client2B.SetUserName(L"bob");
 		clients.push_back(&client2B);
 
-		client2B.SetupServerData("127.0.0.1", PS_DEFAULT_PORT, false);
+		client2B.SetupServerData("127.0.0.1", PS_DEFAULT_PORT);
 		TS_ASSERT(client2B.SetupConnection(nullptr));
 
 		for (size_t i = 0; ; ++i)