Custom 25565 port page (#5369)

+ Add a custom response when an HTTP request comes in to port 25565...

Co-authored-by: Alexander Harkness <me@bearbin.net>

src/Protocol/ProtocolRecognizer.cpp

@@ -90,6 +90,11 @@ void cMultiVersionProtocol::HandleIncomingDataInRecognitionStage(cClientHandle &
 		return;
 	}
 
+	if (TryHandleHTTPRequest(a_Client, a_Data))
+	{
+		return;
+	}
+
 	// TODO: recover from git history
 	// Unlengthed protocol, ...
 
@@ -238,6 +243,37 @@ void cMultiVersionProtocol::SendDisconnect(cClientHandle & a_Client, const AStri
 
 
 
+bool cMultiVersionProtocol::TryHandleHTTPRequest(cClientHandle & a_Client, ContiguousByteBuffer & a_Data)
+{
+	const auto RedirectUrl = cRoot::Get()->GetServer()->GetCustomRedirectUrl();
+
+	if (RedirectUrl.empty())
+	{
+		return false;
+	}
+
+	ContiguousByteBuffer Buffer;
+	m_Buffer.ReadSome(Buffer, 10U);
+	m_Buffer.ResetRead();
+
+	// The request line, hastily decoded with the hope that it's encoded in US-ASCII.
+	const std::string_view Value(reinterpret_cast<const char *>(Buffer.data()), Buffer.size());
+
+	if (Value == u8"GET / HTTP")
+	{
+		const auto Response = fmt::format(u8"HTTP/1.0 303 See Other\r\nLocation: {}\r\n\r\n", cRoot::Get()->GetServer()->GetCustomRedirectUrl());
+		a_Client.SendData({ reinterpret_cast<const std::byte *>(Response.data()), Response.size() });
+		a_Client.Destroy();
+		return true;
+	}
+
+	return false;
+}
+
+
+
+
+
 std::unique_ptr<cProtocol> cMultiVersionProtocol::TryRecognizeLengthedProtocol(cClientHandle & a_Client)
 {
 	UInt32 PacketType;

src/Protocol/ProtocolRecognizer.h

@@ -59,6 +59,9 @@ private:
 	/** Handles and responds to unsupported clients sending pings. */
 	void HandleIncomingDataInOldPingResponseStage(cClientHandle & a_Client, ContiguousByteBufferView a_Data);
 
+	/* Checks if incoming data is an HTTP request and handles it if it is. */
+	bool TryHandleHTTPRequest(cClientHandle & a_Client, ContiguousByteBuffer & a_Data);
+
 	/** Tries to recognize a protocol in the lengthed family (1.7+), based on m_Buffer.
 	Returns a cProtocol_XXX instance if recognized. */
 	std::unique_ptr<cProtocol> TryRecognizeLengthedProtocol(cClientHandle & a_Client);

src/Server.cpp

@@ -158,6 +158,7 @@ bool cServer::InitServer(cSettingsRepositoryInterface & a_Settings, bool a_Shoul
 	m_bIsHardcore = a_Settings.GetValueSetB("Server", "HardcoreEnabled", false);
 	m_bAllowMultiLogin = a_Settings.GetValueSetB("Server", "AllowMultiLogin", false);
 	m_ResourcePackUrl = a_Settings.GetValueSet("Server", "ResourcePackUrl", "");
+	m_CustomRedirectUrl = a_Settings.GetValueSet("Server", "CustomRedirectUrl", "https://youtu.be/dQw4w9WgXcQ");
 
 	m_FaviconData = Base64Encode(cFile::ReadWholeFile(AString("favicon.png")));  // Will return empty string if file nonexistant; client doesn't mind
 

src/Server.h

@@ -96,6 +96,8 @@ public:
 
 	const AString & GetResourcePackUrl(void) { return m_ResourcePackUrl; }
 
+	std::string_view GetCustomRedirectUrl(void) { return m_CustomRedirectUrl; }
+
 	bool Start(void);
 
 	bool Command(cClientHandle & a_Client, AString & a_Cmd);
@@ -222,6 +224,7 @@ private:
 	size_t m_MaxPlayers;
 	bool m_bIsHardcore;
 	AString m_ResourcePackUrl;
+	AString m_CustomRedirectUrl;
 
 	/** Map of protocol version to Forge mods (map of ModName -> ModVersionString) */
 	std::map<UInt32, AStringMap> m_ForgeModsByVersion;