Add packet compression

src/outputmessage.h

@@ -21,12 +21,12 @@ class OutputMessage : public NetworkMessage
 
 	void writeMessageLength() { add_header(info.length); }
 
-	void addCryptoHeader(checksumMode_t mode, uint32_t& sequence)
+	void addCryptoHeader(checksumMode_t mode)
 	{
 		if (mode == CHECKSUM_ADLER) {
 			add_header(adlerChecksum(&buffer[outputBufferStart], info.length));
 		} else if (mode == CHECKSUM_SEQUENCE) {
-			add_header(sequence++);
+			add_header(getSequenceId());
 		}
 
 		writeMessageLength();
@@ -48,6 +48,9 @@ class OutputMessage : public NetworkMessage
 		info.position += msgLen;
 	}
 
+	void setSequenceId(uint32_t sequence) { sequenceId = sequence; }
+	uint32_t getSequenceId() const { return sequenceId; }
+
 private:
 	template <typename T>
 	void add_header(T add)
@@ -60,6 +63,7 @@ class OutputMessage : public NetworkMessage
 	}
 
 	MsgSize_t outputBufferStart = INITIAL_BUFFER_POSITION;
+	uint32_t sequenceId;
 };
 
 namespace tfs::net {

src/protocol.cpp

@@ -46,11 +46,20 @@ bool XTEA_decrypt(NetworkMessage& msg, const xtea::round_keys& key)
 void Protocol::onSendMessage(const OutputMessage_ptr& msg)
 {
 	if (!rawMessages) {
+		if (encryptionEnabled && checksumMode == CHECKSUM_SEQUENCE) {
+			uint32_t compressionChecksum = 0;
+			if (msg->getLength() >= 128 && deflateMessage(*msg)) {
+				compressionChecksum = 0x80000000;
+			}
+
+			msg->setSequenceId(compressionChecksum | getNextSequenceId());
+		}
+
 		msg->writeMessageLength();
 
 		if (encryptionEnabled) {
 			XTEA_encrypt(*msg, key);
-			msg->addCryptoHeader(checksumMode, sequenceNumber);
+			msg->addCryptoHeader(checksumMode);
 		}
 	}
 }
@@ -86,6 +95,34 @@ bool Protocol::RSA_decrypt(NetworkMessage& msg)
 	return msg.getByte() == 0;
 }
 
+bool Protocol::deflateMessage(OutputMessage& msg)
+{
+	static thread_local std::vector<uint8_t> buffer(NETWORKMESSAGE_MAXSIZE);
+	zstream.next_in = msg.getOutputBuffer();
+	zstream.avail_in = msg.getLength();
+	zstream.next_out = buffer.data();
+	zstream.avail_out = buffer.size();
+
+	const auto result = deflate(&zstream, Z_FINISH);
+	if (result != Z_OK && result != Z_STREAM_END) {
+		std::cout << "Error while deflating packet data error: " << (zstream.msg ? zstream.msg : "unknown")
+		          << std::endl;
+		return false;
+	}
+
+	const auto size = zstream.total_out;
+	if (size <= 0) {
+		std::cout << "Deflated packet data had invalid size: " << size
+		          << " error: " << (zstream.msg ? zstream.msg : "unknown") << std::endl;
+		return false;
+	}
+
+	msg.reset();
+	msg.addBytes(reinterpret_cast<const char*>(buffer.data()), size);
+
+	return true;
+}
+
 Connection::Address Protocol::getIP() const
 {
 	if (auto connection = getConnection()) {

src/protocol.h

@@ -7,10 +7,17 @@
 #include "connection.h"
 #include "xtea.h"
 
+#include <zlib.h>
+
 class Protocol : public std::enable_shared_from_this<Protocol>
 {
 public:
-	explicit Protocol(Connection_ptr connection) : connection(connection) {}
+	explicit Protocol(Connection_ptr connection) : connection(connection)
+	{
+		if (deflateInit2(&zstream, 6, Z_DEFLATED, -15, 8, Z_DEFAULT_STRATEGY) != Z_OK) {
+			std::cout << "ZLIB initialization error: " << (zstream.msg ? zstream.msg : "unknown") << std::endl;
+		}
+	}
 	virtual ~Protocol() = default;
 
 	// non-copyable
@@ -42,6 +49,16 @@ class Protocol : public std::enable_shared_from_this<Protocol>
 		}
 	}
 
+	uint32_t getNextSequenceId()
+	{
+		const auto sequence = ++sequenceNumber;
+		if (sequenceNumber >= std::numeric_limits<int32_t>::max()) {
+			sequenceNumber = 0;
+		}
+
+		return sequence;
+	}
+
 protected:
 	static constexpr size_t RSA_BUFFER_LENGTH = 128;
 
@@ -57,6 +74,8 @@ class Protocol : public std::enable_shared_from_this<Protocol>
 
 	static bool RSA_decrypt(NetworkMessage& msg);
 
+	bool deflateMessage(OutputMessage& msg);
+
 	void setRawMessages(bool value) { rawMessages = value; }
 
 	virtual void release() {}
@@ -72,6 +91,8 @@ class Protocol : public std::enable_shared_from_this<Protocol>
 	bool encryptionEnabled = false;
 	checksumMode_t checksumMode = CHECKSUM_ADLER;
 	bool rawMessages = false;
+
+	z_stream zstream{};
 };
 
 #endif // FS_PROTOCOL_H