netplay: Enable TCP_NODELAY for game sockets

Among other reasons, we already use an internal buffer

lib/netplay/netplay.cpp

@@ -89,6 +89,7 @@ char masterserver_name[255] = {'\0'};
 static unsigned int masterserver_port = 0, gameserver_port = 0;
 static bool bJoinPrefTryIPv6First = true;
 static bool bDefaultHostFreeChatEnabled = true;
+static bool bEnableTCPNoDelay = true;
 
 // This is for command line argument override
 // Disables port saving and reading from/to config
@@ -3993,6 +3994,12 @@ static void NETallowJoining()
 		tmp_connectState[i].ip = rIP;
 		tmp_connectState[i].connectTime = std::chrono::steady_clock::now();
 		tmp_connectState[i].connectState = TmpSocketInfo::TmpConnectState::PendingInitialConnect;
+
+		if (bEnableTCPNoDelay)
+		{
+			// Enable TCP_NODELAY
+			socketSetTCPNoDelay(*tmp_socket[i], true);
+		}
 	}
 
 	if (checkSockets(*tmp_socket_set, NET_READ_TIMEOUT) > 0)
@@ -4921,6 +4928,12 @@ bool NETjoinGame(const char *host, uint32_t port, const char *playername, const
 	// `client_transient_socket` is used to talk to host machine
 	SocketSet_AddSocket(*client_socket_set, client_transient_socket);
 
+	if (bEnableTCPNoDelay)
+	{
+		// Enable TCP_NODELAY
+		socketSetTCPNoDelay(*client_transient_socket, true);
+	}
+
 	// Send NETCODE_VERSION_MAJOR and NETCODE_VERSION_MINOR
 	p_buffer = buffer;
 	auto pushu32 = [&](uint32_t value) {
@@ -5170,6 +5183,16 @@ bool NETgetDefaultMPHostFreeChatPreference()
 	return bDefaultHostFreeChatEnabled;
 }
 
+void NETsetEnableTCPNoDelay(bool enabled)
+{
+	bEnableTCPNoDelay = enabled;
+}
+
+bool NETgetEnableTCPNoDelay()
+{
+	return bEnableTCPNoDelay;
+}
+
 void NETsetPlayerConnectionStatus(CONNECTION_STATUS status, unsigned player)
 {
 	unsigned n;

lib/netplay/netplay.h

@@ -443,6 +443,8 @@ void NETsetJoinPreferenceIPv6(bool bTryIPv6First);
 bool NETgetJoinPreferenceIPv6();
 void NETsetDefaultMPHostFreeChatPreference(bool enabled);
 bool NETgetDefaultMPHostFreeChatPreference();
+void NETsetEnableTCPNoDelay(bool enabled);
+bool NETgetEnableTCPNoDelay();
 
 void NETsetGamePassword(const char *password);
 void NETBroadcastPlayerInfo(uint32_t index);

lib/netplay/netsocket.cpp

@@ -40,6 +40,12 @@
 	#pragma clang diagnostic ignored "-Wshorten-64-to-32" // FIXME!!
 #endif
 
+#if defined(WZ_OS_UNIX)
+# include <netinet/tcp.h> // For TCP_NODELAY
+#elif defined(WZ_OS_WIN)
+// Already included Winsock2.h which defines TCP_NODELAY
+#endif
+
 enum
 {
 	SOCK_CONNECTION,
@@ -795,6 +801,19 @@ void socketBeginCompression(Socket& sock)
 	wzMutexUnlock(socketThreadMutex);
 }
 
+bool socketSetTCPNoDelay(Socket& sock, bool nodelay)
+{
+#if defined(TCP_NODELAY)
+	int value = (nodelay) ? 1 : 0;
+	int result = setsockopt(sock.fd[SOCK_CONNECTION], IPPROTO_TCP, TCP_NODELAY, (char *) &value, sizeof(int));
+	debug(LOG_INFO, "Setting TCP_NODELAY on socket: %s", (result != SOCKET_ERROR) ? "success" : "failure");
+	return result != SOCKET_ERROR;
+#else
+	debug(LOG_INFO, "Unable to set TCP_NODELAY on socket - unsupported");
+	return false;
+#endif
+}
+
 Socket::~Socket()
 {
 	if (isCompressed)

lib/netplay/netsocket.h

@@ -116,6 +116,8 @@ ssize_t readAll(Socket& sock, void *buf, size_t size, unsigned timeout);///< Rea
 WZ_DECL_NONNULL(2)
 ssize_t writeAll(Socket& sock, const void *buf, size_t size, size_t *rawByteCount = nullptr);  ///< Nonblocking write of size bytes to the Socket. All bytes will be written asynchronously, by a separate thread. Raw count of bytes (after compression) returned in rawByteCount, which will often be 0 until the socket is flushed.
 
+bool socketSetTCPNoDelay(Socket& sock, bool nodelay); ///< nodelay = true disables the Nagle algorithm for TCP socket
+
 // Sockets, compressed.
 void socketBeginCompression(Socket& sock); ///< Makes future data sent compressed, and future data received expected to be compressed.
 bool socketReadDisconnected(const Socket& sock);  ///< If readNoInt returned 0, returns true if this is the result of a disconnect, or false if the input compressed data just hasn't produced any output bytes.

src/configuration.cpp

@@ -423,6 +423,7 @@ bool loadConfig()
 	}
 	NETsetJoinPreferenceIPv6(iniGetBool("prefer_ipv6", true).value());
 	NETsetDefaultMPHostFreeChatPreference(iniGetBool("hostingChatDefault", NETgetDefaultMPHostFreeChatPreference()).value());
+	NETsetEnableTCPNoDelay(iniGetBool("tcp_nodelay", NETgetEnableTCPNoDelay()).value());
 	setPublicIPv4LookupService(iniGetString("publicIPv4LookupService_Url", WZ_DEFAULT_PUBLIC_IPv4_LOOKUP_SERVICE_URL).value(), iniGetString("publicIPv4LookupService_JSONKey", WZ_DEFAULT_PUBLIC_IPv4_LOOKUP_SERVICE_JSONKEY).value());
 	setPublicIPv6LookupService(iniGetString("publicIPv6LookupService_Url", WZ_DEFAULT_PUBLIC_IPv6_LOOKUP_SERVICE_URL).value(), iniGetString("publicIPv6LookupService_JSONKey", WZ_DEFAULT_PUBLIC_IPv6_LOOKUP_SERVICE_JSONKEY).value());
 	war_SetFMVmode((FMV_MODE)iniGetInteger("FMVmode", war_GetFMVmode()).value());
@@ -722,6 +723,8 @@ bool saveConfig()
 	}
 	iniSetBool("prefer_ipv6", NETgetJoinPreferenceIPv6());
 	iniSetInteger("hostingChatDefault", (NETgetDefaultMPHostFreeChatPreference()) ? 1 : 0);
+	iniSetInteger("tcp_nodelay", (NETgetEnableTCPNoDelay()) ? 1 : 0);
+
 	iniSetString("publicIPv4LookupService_Url", getPublicIPv4LookupServiceUrl());
 	iniSetString("publicIPv4LookupService_JSONKey", getPublicIPv4LookupServiceJSONKey());
 	iniSetString("publicIPv6LookupService_Url", getPublicIPv6LookupServiceUrl());