LibGUI/WindowServer: Rework packet serialization

Instead of sending while serializing (what even was that), we serialize
the whole packet into a buffer which can be sent in one go. First of all
this reduces the number of sends by a lot. This also fixes WindowServer
ending up sending partial packets when client is not responsive.
Previously we would just try sending once, if any send failed the send
was aborted while partial packet was already transmitted. This lead to
packet stream being out of sync leading to the client killing itself.
Now we allow 64 KiB outgoing buffer per client. If this buffer ever fills
up, we will not send partial packets.

userspace/libraries/LibGUI/Window.cpp

@@ -16,47 +16,6 @@
 namespace LibGUI
 {
 
-	struct ReceivePacket
-	{
-		PacketType type;
-		BAN::Vector<uint8_t> data_with_type;
-	};
-
-	static BAN::ErrorOr<ReceivePacket> recv_packet(int socket)
-	{
-		uint32_t packet_size;
-
-		{
-			const ssize_t nrecv = recv(socket, &packet_size, sizeof(uint32_t), 0);
-			if (nrecv < 0)
-				return BAN::Error::from_errno(errno);
-			if (nrecv == 0)
-				return BAN::Error::from_errno(ECONNRESET);
-		}
-
-		if (packet_size < sizeof(uint32_t))
-			return BAN::Error::from_literal("invalid packet, does not fit packet id");
-
-		BAN::Vector<uint8_t> packet_data;
-		TRY(packet_data.resize(packet_size));
-
-		size_t total_recv = 0;
-		while (total_recv < packet_size)
-		{
-			const ssize_t nrecv = recv(socket, packet_data.data() + total_recv, packet_size - total_recv, 0);
-			if (nrecv < 0)
-				return BAN::Error::from_errno(errno);
-			if (nrecv == 0)
-				return BAN::Error::from_errno(ECONNRESET);
-			total_recv += nrecv;
-		}
-
-		return ReceivePacket {
-			*reinterpret_cast<PacketType*>(packet_data.data()),
-			packet_data
-		};
-	}
-
 	Window::~Window()
 	{
 		cleanup();
@@ -64,7 +23,7 @@ namespace LibGUI
 
 	BAN::ErrorOr<BAN::UniqPtr<Window>> Window::create(uint32_t width, uint32_t height, BAN::StringView title, Attributes attributes)
 	{
-		int server_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+		int server_fd = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
 		if (server_fd == -1)
 			return BAN::Error::from_errno(errno);
 		BAN::ScopeGuard server_closer([server_fd] { close(server_fd); });
@@ -74,16 +33,10 @@ namespace LibGUI
 			return BAN::Error::from_errno(errno);
 		BAN::ScopeGuard epoll_closer([epoll_fd] { close(epoll_fd); });
 
-		epoll_event epoll_event {
-			.events = EPOLLIN,
-			.data = { .fd = server_fd },
-		};
+		epoll_event epoll_event { .events = EPOLLIN, .data = { .fd = server_fd } };
 		if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_fd, &epoll_event) == -1)
 			return BAN::Error::from_errno(errno);
 
-		if (fcntl(server_fd, F_SETFD, fcntl(server_fd, F_GETFD) | FD_CLOEXEC) == -1)
-			return BAN::Error::from_errno(errno);
-
 		timespec start_time;
 		clock_gettime(CLOCK_MONOTONIC, &start_time);
 
@@ -107,19 +60,23 @@ namespace LibGUI
 			nanosleep(&sleep_time, nullptr);
 		}
 
+		auto window = TRY(BAN::UniqPtr<Window>::create(server_fd, epoll_fd, attributes));
+
 		WindowPacket::WindowCreate create_packet;
 		create_packet.width = width;
 		create_packet.height = height;
 		create_packet.attributes = attributes;
 		TRY(create_packet.title.append(title));
-		TRY(create_packet.send_serialized(server_fd));
-
-		auto window = TRY(BAN::UniqPtr<Window>::create(server_fd, epoll_fd, attributes));
+		window->send_packet(create_packet, __FUNCTION__);
 
 		bool resized = false;
 		window->set_resize_window_event_callback([&]() { resized = true; });
 		while (!resized)
+		{
+			// FIXME: timeout?
+			window->wait_events();
 			window->poll_events();
+		}
 		window->set_resize_window_event_callback({});
 
 		server_closer.disable();
@@ -128,6 +85,30 @@ namespace LibGUI
 		return window;
 	}
 
+	template<typename T>
+	void Window::send_packet(const T& packet, BAN::StringView function)
+	{
+		const size_t serialized_size = packet.serialized_size();
+		if (serialized_size > m_out_buffer.size())
+		{
+			dwarnln("cannot to send {} byte packet", serialized_size);
+			return on_socket_error(function);
+		}
+
+		packet.serialize(m_in_buffer.span());
+
+		size_t total_sent = 0;
+		while (total_sent < serialized_size)
+		{
+			const ssize_t nsend = send(m_server_fd, m_in_buffer.data() + total_sent, serialized_size - total_sent, 0);
+			if (nsend < 0)
+				dwarnln("send: {}", strerror(errno));
+			if (nsend <= 0)
+				return on_socket_error(function);
+			total_sent += nsend;
+		}
+	}
+
 	BAN::ErrorOr<void> Window::set_root_widget(BAN::RefPtr<Widget::Widget> widget)
 	{
 		TRY(widget->set_fixed_geometry({ 0, 0, m_width, m_height }));
@@ -186,36 +167,28 @@ namespace LibGUI
 		packet.y = y;
 		packet.width = width;
 		packet.height = height;
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::set_mouse_relative(bool enabled)
 	{
 		WindowPacket::WindowSetMouseRelative packet;
 		packet.enabled = enabled;
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::set_fullscreen(bool fullscreen)
 	{
 		WindowPacket::WindowSetFullscreen packet;
 		packet.fullscreen = fullscreen;
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::set_title(BAN::StringView title)
 	{
 		WindowPacket::WindowSetTitle packet;
 		MUST(packet.title.append(title));
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::set_position(int32_t x, int32_t y)
@@ -223,9 +196,7 @@ namespace LibGUI
 		WindowPacket::WindowSetPosition packet;
 		packet.x = x;
 		packet.y = y;
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::set_cursor_visible(bool visible)
@@ -247,9 +218,7 @@ namespace LibGUI
 		MUST(packet.pixels.resize(pixels.size()));
 		for (size_t i = 0; i < packet.pixels.size(); i++)
 			packet.pixels[i] = pixels[i];
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::set_min_size(uint32_t width, uint32_t height)
@@ -257,9 +226,7 @@ namespace LibGUI
 		WindowPacket::WindowSetMinSize packet;
 		packet.width = width;
 		packet.height = height;
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::set_max_size(uint32_t width, uint32_t height)
@@ -267,19 +234,14 @@ namespace LibGUI
 		WindowPacket::WindowSetMaxSize packet;
 		packet.width = width;
 		packet.height = height;
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::set_attributes(Attributes attributes)
 	{
 		WindowPacket::WindowSetAttributes packet;
 		packet.attributes = attributes;
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
-
+		send_packet(packet, __FUNCTION__);
 		m_attributes = attributes;
 	}
 
@@ -288,9 +250,7 @@ namespace LibGUI
 		WindowPacket::WindowSetSize packet;
 		packet.width = width;
 		packet.height = height;
-
-		if (auto ret = packet.send_serialized(m_server_fd); ret.is_error())
-			return on_socket_error(__FUNCTION__);
+		send_packet(packet, __FUNCTION__);
 	}
 
 	void Window::on_socket_error(BAN::StringView function)
@@ -347,20 +307,37 @@ namespace LibGUI
 
 	void Window::poll_events()
 	{
-#define TRY_OR_BREAK(...) ({ auto&& e = (__VA_ARGS__); if (e.is_error()) break; e.release_value(); })
 		for (;;)
 		{
 			epoll_event event;
 			if (epoll_wait(m_epoll_fd, &event, 1, 0) == 0)
 				break;
 
-			auto packet_or_error = recv_packet(m_server_fd);
-			if (packet_or_error.is_error())
+			if (event.events & (EPOLLHUP | EPOLLERR))
 				return on_socket_error(__FUNCTION__);
 
-			const auto [packet_type, packet_data] = packet_or_error.release_value();
-			switch (packet_type)
+			ASSERT(event.events & EPOLLIN);
+
 			{
+				const ssize_t nrecv = recv(m_server_fd, m_in_buffer.data() + m_in_buffer_size, m_in_buffer.size() - m_in_buffer_size, 0);
+				if (nrecv <= 0)
+					return on_socket_error(__FUNCTION__);
+				if (nrecv > 0)
+					m_in_buffer_size += nrecv;
+			}
+
+			size_t bytes_handled = 0;
+			while (m_in_buffer_size - bytes_handled >= sizeof(PacketHeader))
+			{
+				BAN::ConstByteSpan packet_span = m_in_buffer.span().slice(bytes_handled);
+				const auto header = packet_span.as<const PacketHeader>();
+				if (packet_span.size() < header.size || header.size < sizeof(LibGUI::PacketHeader))
+					break;
+				packet_span = packet_span.slice(0, header.size);
+
+				switch (header.type)
+				{
+#define TRY_OR_BREAK(...) ({ auto&& e = (__VA_ARGS__); if (e.is_error()) break; e.release_value(); })
 					case PacketType::DestroyWindowEvent:
 						exit(1);
 					case PacketType::CloseWindowEvent:
@@ -371,30 +348,30 @@ namespace LibGUI
 						break;
 					case PacketType::ResizeWindowEvent:
 					{
-					MUST(handle_resize_event(TRY_OR_BREAK(EventPacket::ResizeWindowEvent::deserialize(packet_data.span()))));
+						MUST(handle_resize_event(TRY_OR_BREAK(EventPacket::ResizeWindowEvent::deserialize(packet_span))));
 						if (m_resize_window_event_callback)
 							m_resize_window_event_callback();
 						break;
 					}
 					case PacketType::WindowShownEvent:
 						if (m_window_shown_event_callback)
-						m_window_shown_event_callback(TRY_OR_BREAK(EventPacket::WindowShownEvent::deserialize(packet_data.span())).event);
+							m_window_shown_event_callback(TRY_OR_BREAK(EventPacket::WindowShownEvent::deserialize(packet_span)).event);
 						break;
 					case PacketType::WindowFocusEvent:
 						if (m_window_focus_event_callback)
-						m_window_focus_event_callback(TRY_OR_BREAK(EventPacket::WindowFocusEvent::deserialize(packet_data.span())).event);
+							m_window_focus_event_callback(TRY_OR_BREAK(EventPacket::WindowFocusEvent::deserialize(packet_span)).event);
 						break;
 					case PacketType::WindowFullscreenEvent:
 						if (m_window_fullscreen_event_callback)
-						m_window_fullscreen_event_callback(TRY_OR_BREAK(EventPacket::WindowFullscreenEvent::deserialize(packet_data.span())).event);
+							m_window_fullscreen_event_callback(TRY_OR_BREAK(EventPacket::WindowFullscreenEvent::deserialize(packet_span)).event);
 						break;
 					case PacketType::KeyEvent:
 						if (m_key_event_callback)
-						m_key_event_callback(TRY_OR_BREAK(EventPacket::KeyEvent::deserialize(packet_data.span())).event);
+							m_key_event_callback(TRY_OR_BREAK(EventPacket::KeyEvent::deserialize(packet_span)).event);
 						break;
 					case PacketType::MouseButtonEvent:
 					{
-					auto event = TRY_OR_BREAK(EventPacket::MouseButtonEvent::deserialize(packet_data.span())).event;
+						auto event = TRY_OR_BREAK(EventPacket::MouseButtonEvent::deserialize(packet_span)).event;
 						if (m_mouse_button_event_callback)
 							m_mouse_button_event_callback(event);
 						if (m_root_widget)
@@ -403,7 +380,7 @@ namespace LibGUI
 					}
 					case PacketType::MouseMoveEvent:
 					{
-					auto event = TRY_OR_BREAK(EventPacket::MouseMoveEvent::deserialize(packet_data.span())).event;
+						auto event = TRY_OR_BREAK(EventPacket::MouseMoveEvent::deserialize(packet_span)).event;
 						if (m_mouse_move_event_callback)
 							m_mouse_move_event_callback(event);
 						if (m_root_widget)
@@ -416,13 +393,35 @@ namespace LibGUI
 					}
 					case PacketType::MouseScrollEvent:
 						if (m_mouse_scroll_event_callback)
-						m_mouse_scroll_event_callback(TRY_OR_BREAK(EventPacket::MouseScrollEvent::deserialize(packet_data.span())).event);
+							m_mouse_scroll_event_callback(TRY_OR_BREAK(EventPacket::MouseScrollEvent::deserialize(packet_span)).event);
 						break;
-				default:
-					break;
-			}
-		}
 #undef TRY_OR_BREAK
+					default:
+						dprintln("unhandled packet type: {}", static_cast<uint32_t>(header.type));
+						break;
+				}
+
+				bytes_handled += header.size;
+			}
+
+			// NOTE: this will only move a single partial packet, so this is fine
+			m_in_buffer_size -= bytes_handled;
+			memmove(
+				m_in_buffer.data(),
+				m_in_buffer.data() + bytes_handled,
+				m_in_buffer_size
+			);
+
+			if (m_in_buffer_size >= sizeof(LibGUI::PacketHeader))
+			{
+				const auto header = BAN::ConstByteSpan(m_in_buffer.span()).as<const LibGUI::PacketHeader>();
+				if (header.size < sizeof(LibGUI::PacketHeader) || header.size > m_in_buffer.size())
+				{
+					dwarnln("server tried to send a {} byte packet", header.size);
+					return on_socket_error(__FUNCTION__);
+				}
+			}
+		}
 
 		if (m_root_widget)
 		{

userspace/libraries/LibGUI/include/LibGUI/Packet.h

@@ -1,15 +1,13 @@
 #pragma once
 
+#include <BAN/ByteSpan.h>
 #include <BAN/String.h>
 #include <BAN/StringView.h>
-#include <BAN/ByteSpan.h>
+#include <BAN/Vector.h>
 
 #include <LibInput/KeyEvent.h>
 #include <LibInput/MouseEvent.h>
 
-#include <sys/banan-os.h>
-#include <sys/socket.h>
-
 #define FOR_EACH_0(macro)
 #define FOR_EACH_2(macro, type, name)      macro(type, name)
 #define FOR_EACH_4(macro, type, name, ...) macro(type, name) FOR_EACH_2(macro, __VA_ARGS__)
@@ -31,7 +29,7 @@
 
 #define FIELD_DECL(type, name) type name;
 #define ADD_SERIALIZED_SIZE(type, name) serialized_size += Serialize::serialized_size_impl<type>(this->name);
-#define SEND_SERIALIZED(type, name) TRY(Serialize::send_serialized_impl<type>(socket, this->name));
+#define SERIALIZE(type, name) Serialize::serialize_impl<type>(buffer, this->name);
 #define DESERIALIZE(type, name) value.name = TRY(Serialize::deserialize_impl<type>(buffer));
 
 #define DEFINE_PACKET_EXTRA(name, extra, ...) \
@@ -44,26 +42,28 @@
  \
 		FOR_EACH(FIELD_DECL, __VA_ARGS__) \
  \
-		size_t serialized_size() \
+		size_t serialized_size() const \
 		{ \
-			size_t serialized_size = Serialize::serialized_size_impl<uint32_t>(type_u32); \
+			size_t serialized_size = 0; \
+			serialized_size += Serialize::serialized_size_impl<uint32_t>(0); \
+			serialized_size += Serialize::serialized_size_impl<uint32_t>(type_u32); \
 			FOR_EACH(ADD_SERIALIZED_SIZE, __VA_ARGS__) \
 			return serialized_size; \
 		} \
  \
-		BAN::ErrorOr<void> send_serialized(int socket) \
+		void serialize(BAN::ByteSpan buffer) const \
 		{ \
 			const uint32_t serialized_size = this->serialized_size(); \
-			TRY(Serialize::send_serialized_impl<uint32_t>(socket, serialized_size)); \
-			TRY(Serialize::send_serialized_impl<uint32_t>(socket, type_u32)); \
-			FOR_EACH(SEND_SERIALIZED, __VA_ARGS__) \
-			return {}; \
+			Serialize::serialize_impl<uint32_t>(buffer, serialized_size); \
+			Serialize::serialize_impl<uint32_t>(buffer, type_u32); \
+			FOR_EACH(SERIALIZE, __VA_ARGS__); \
 		} \
  \
 		static BAN::ErrorOr<name> deserialize(BAN::ConstByteSpan buffer) \
 		{ \
+			const uint32_t size_u32 = TRY(Serialize::deserialize_impl<uint32_t>(buffer)); \
 			const uint32_t type_u32 = TRY(Serialize::deserialize_impl<uint32_t>(buffer)); \
-			if (type_u32 != name::type_u32) \
+			if (type_u32 != name::type_u32 || size_u32 != buffer.size() + 2 * sizeof(uint32_t)) \
 				return BAN::Error::from_errno(EINVAL); \
 			name value; \
 			FOR_EACH(DESERIALIZE, __VA_ARGS__) \
@@ -90,19 +90,11 @@ namespace LibGUI
 	namespace Serialize
 	{
 
-		inline BAN::ErrorOr<void> send_raw_data(int socket, BAN::ConstByteSpan data)
+		inline void append_raw_data(BAN::ByteSpan& buffer, BAN::ConstByteSpan data)
 		{
-			size_t send_done = 0;
-			while (send_done < data.size())
-			{
-				const ssize_t nsend = ::send(socket, data.data() + send_done, data.size() - send_done, 0);
-				if (nsend < 0)
-					return BAN::Error::from_errno(errno);
-				if (nsend == 0)
-					return BAN::Error::from_errno(ECONNRESET);
-				send_done += nsend;
-			}
-			return {};
+			ASSERT(buffer.size() >= data.size());
+			memcpy(buffer.data(), data.data(), data.size());
+			buffer = buffer.slice(data.size());
 		}
 
 		template<typename T> requires BAN::is_pod_v<T>
@@ -112,10 +104,9 @@ namespace LibGUI
 		}
 
 		template<typename T> requires BAN::is_pod_v<T>
-		inline BAN::ErrorOr<void> send_serialized_impl(int socket, const T& value)
+		inline void serialize_impl(BAN::ByteSpan& buffer, const T& value)
 		{
-			TRY(send_raw_data(socket, BAN::ConstByteSpan::from(value)));
-			return {};
+			append_raw_data(buffer, BAN::ConstByteSpan::from(value));
 		}
 
 		template<typename T> requires BAN::is_pod_v<T>
@@ -135,13 +126,12 @@ namespace LibGUI
 		}
 
 		template<typename T> requires BAN::is_same_v<T, BAN::String>
-		inline BAN::ErrorOr<void> send_serialized_impl(int socket, const T& value)
+		inline void serialize_impl(BAN::ByteSpan& buffer, const T& value)
 		{
 			const uint32_t value_size = value.size();
-			TRY(send_raw_data(socket, BAN::ConstByteSpan::from(value_size)));
+			append_raw_data(buffer, BAN::ConstByteSpan::from(value_size));
 			auto* u8_data = reinterpret_cast<const uint8_t*>(value.data());
-			TRY(send_raw_data(socket, BAN::ConstByteSpan(u8_data, value.size())));
-			return {};
+			append_raw_data(buffer, BAN::ConstByteSpan(u8_data, value.size()));
 		}
 
 		template<typename T> requires BAN::is_same_v<T, BAN::String>
@@ -173,13 +163,12 @@ namespace LibGUI
 		}
 
 		template<detail::Vector T>
-		inline BAN::ErrorOr<void> send_serialized_impl(int socket, const T& vector)
+		inline void serialize_impl(BAN::ByteSpan& buffer, const T& vector)
 		{
 			const uint32_t value_size = vector.size();
-			TRY(send_raw_data(socket, BAN::ConstByteSpan::from(value_size)));
+			append_raw_data(buffer, BAN::ConstByteSpan::from(value_size));
 			for (const auto& element : vector)
-				TRY(send_serialized_impl(socket, element));
-			return {};
+				serialize_impl(buffer, element);
 		}
 
 		template<detail::Vector T>
@@ -226,6 +215,12 @@ namespace LibGUI
 		MouseScrollEvent,
 	};
 
+	struct PacketHeader
+	{
+		uint32_t size;
+		PacketType type;
+	};
+
 	namespace WindowPacket
 	{
 

userspace/libraries/LibGUI/include/LibGUI/Window.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <BAN/Array.h>
 #include <BAN/Function.h>
 #include <BAN/StringView.h>
 #include <BAN/UniqPtr.h>
@@ -93,6 +94,9 @@ namespace LibGUI
 
 		BAN::ErrorOr<void> handle_resize_event(const EventPacket::ResizeWindowEvent&);
 
+		template<typename T>
+		void send_packet(const T& packet, BAN::StringView function);
+
 	private:
 		const int m_server_fd;
 		const int m_epoll_fd;
@@ -119,6 +123,11 @@ namespace LibGUI
 		BAN::Function<void(EventPacket::MouseMoveEvent::event_t)>        m_mouse_move_event_callback;
 		BAN::Function<void(EventPacket::MouseScrollEvent::event_t)>      m_mouse_scroll_event_callback;
 
+		size_t m_in_buffer_size { 0 };
+		BAN::Array<uint8_t, 64 * 1024> m_in_buffer;
+
+		BAN::Array<uint8_t, 64 * 1024> m_out_buffer;
+
 		friend class BAN::UniqPtr<Window>;
 	};
 

userspace/programs/WindowServer/Window.cpp

@@ -16,7 +16,22 @@ Window::~Window()
 	smo_delete(m_smo_key);
 
 	LibGUI::EventPacket::DestroyWindowEvent packet;
-	(void)packet.send_serialized(m_client_fd);
+
+	BAN::Vector<uint8_t> buffer;
+	if (!buffer.resize(packet.serialized_size()).is_error())
+	{
+		packet.serialize(buffer.span());
+
+		size_t total_sent = 0;
+		while (total_sent < buffer.size())
+		{
+			const ssize_t nsend = send(m_client_fd, buffer.data() + total_sent, buffer.size() - total_sent, 0);
+			if (nsend <= 0)
+				break;
+			total_sent += nsend;
+		}
+	}
+
 	close(m_client_fd);
 }
 

userspace/programs/WindowServer/WindowServer.cpp

@@ -86,7 +86,7 @@ void WindowServer::on_window_create(int fd, const LibGUI::WindowPacket::WindowCr
 	response.width = window->client_width();
 	response.height = window->client_height();
 	response.smo_key = window->smo_key();
-	if (auto ret = response.send_serialized(fd); ret.is_error())
+	if (auto ret = append_serialized_packet(response, fd); ret.is_error())
 	{
 		dwarnln("could not respond to window create request: {}", ret.error());
 		return;
@@ -205,7 +205,7 @@ void WindowServer::on_window_set_attributes(int fd, const LibGUI::WindowPacket::
 			.shown = target_window->get_attributes().shown,
 		},
 	};
-	if (auto ret = event_packet.send_serialized(target_window->client_fd()); ret.is_error())
+	if (auto ret = append_serialized_packet(event_packet, target_window->client_fd()); ret.is_error())
 		dwarnln("could not send window shown event: {}", ret.error());
 
 	if (packet.attributes.focusable && packet.attributes.shown && m_state == State::Normal)
@@ -312,7 +312,7 @@ void WindowServer::on_window_set_fullscreen(int fd, const LibGUI::WindowPacket::
 		auto event_packet = LibGUI::EventPacket::WindowFullscreenEvent {
 			.event = { .fullscreen = false }
 		};
-		if (auto ret = event_packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+		if (auto ret = append_serialized_packet(event_packet, m_focused_window->client_fd()); ret.is_error())
 			dwarnln("could not send window fullscreen event: {}", ret.error());
 
 		m_state = State::Normal;
@@ -347,7 +347,7 @@ void WindowServer::on_window_set_fullscreen(int fd, const LibGUI::WindowPacket::
 	auto event_packet = LibGUI::EventPacket::WindowFullscreenEvent {
 		.event = { .fullscreen = true }
 	};
-	if (auto ret = event_packet.send_serialized(target_window->client_fd()); ret.is_error())
+	if (auto ret = append_serialized_packet(event_packet, target_window->client_fd()); ret.is_error())
 		dwarnln("could not send window fullscreen event: {}", ret.error());
 
 	m_state = State::Fullscreen;
@@ -488,7 +488,7 @@ void WindowServer::on_key_event(LibInput::KeyEvent event)
 	if (m_is_mod_key_held && event.pressed() && event.key == LibInput::Key::Q)
 	{
 		LibGUI::EventPacket::CloseWindowEvent packet;
-		if (auto ret = packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+		if (auto ret = append_serialized_packet(packet, m_focused_window->client_fd()); ret.is_error())
 			dwarnln("could not send window close event: {}", ret.error());
 		return;
 	}
@@ -521,7 +521,7 @@ void WindowServer::on_key_event(LibInput::KeyEvent event)
 		auto event_packet = LibGUI::EventPacket::WindowFullscreenEvent {
 			.event = { .fullscreen = (m_state == State::Fullscreen) }
 		};
-		if (auto ret = event_packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+		if (auto ret = append_serialized_packet(event_packet, m_focused_window->client_fd()); ret.is_error())
 			dwarnln("could not send window fullscreen event: {}", ret.error());
 
 		invalidate(m_framebuffer.area());
@@ -530,7 +530,7 @@ void WindowServer::on_key_event(LibInput::KeyEvent event)
 
 	LibGUI::EventPacket::KeyEvent packet;
 	packet.event = event;
-	if (auto ret = packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+	if (auto ret = append_serialized_packet(packet, m_focused_window->client_fd()); ret.is_error())
 		dwarnln("could not send key event: {}", ret.error());
 }
 
@@ -545,7 +545,7 @@ void WindowServer::on_mouse_button(LibInput::MouseButtonEvent event)
 		packet.event.pressed = event.pressed;
 		packet.event.x = 0;
 		packet.event.y = 0;
-		if (auto ret = packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+		if (auto ret = append_serialized_packet(packet, m_focused_window->client_fd()); ret.is_error())
 			dwarnln("could not send mouse button event: {}", ret.error());
 		return;
 	}
@@ -604,7 +604,7 @@ void WindowServer::on_mouse_button(LibInput::MouseButtonEvent event)
 			if (event.button == LibInput::MouseButton::Left && !event.pressed && target_window->close_button_area().contains(m_cursor))
 			{
 				LibGUI::EventPacket::CloseWindowEvent packet;
-				if (auto ret = packet.send_serialized(target_window->client_fd()); ret.is_error())
+				if (auto ret = append_serialized_packet(packet, target_window->client_fd()); ret.is_error())
 					dwarnln("could not send close window event: {}", ret.error());
 				break;
 			}
@@ -618,7 +618,7 @@ void WindowServer::on_mouse_button(LibInput::MouseButtonEvent event)
 				packet.event.pressed = event.pressed;
 				packet.event.x = m_cursor.x - target_window->client_x();
 				packet.event.y = m_cursor.y - target_window->client_y();
-				if (auto ret = packet.send_serialized(target_window->client_fd()); ret.is_error())
+				if (auto ret = append_serialized_packet(packet, target_window->client_fd()); ret.is_error())
 				{
 					dwarnln("could not send mouse button event: {}", ret.error());
 					return;
@@ -649,7 +649,7 @@ void WindowServer::on_mouse_button(LibInput::MouseButtonEvent event)
 				event.width = m_focused_window->client_width();
 				event.height = m_focused_window->client_height();
 				event.smo_key = m_focused_window->smo_key();
-				if (auto ret = event.send_serialized(m_focused_window->client_fd()); ret.is_error())
+				if (auto ret = append_serialized_packet(event, m_focused_window->client_fd()); ret.is_error())
 				{
 					dwarnln("could not respond to window resize request: {}", ret.error());
 					return;
@@ -698,7 +698,7 @@ void WindowServer::on_mouse_move_impl(int32_t new_x, int32_t new_y)
 			LibGUI::EventPacket::MouseMoveEvent packet;
 			packet.event.x = m_cursor.x - m_focused_window->client_x();
 			packet.event.y = m_cursor.y - m_focused_window->client_y();
-			if (auto ret = packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+			if (auto ret = append_serialized_packet(packet, m_focused_window->client_fd()); ret.is_error())
 			{
 				dwarnln("could not send mouse move event: {}", ret.error());
 				return;
@@ -736,7 +736,7 @@ void WindowServer::on_mouse_move(LibInput::MouseMoveEvent event)
 		LibGUI::EventPacket::MouseMoveEvent packet;
 		packet.event.x =  event.rel_x;
 		packet.event.y = -event.rel_y;
-		if (auto ret = packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+		if (auto ret = append_serialized_packet(packet, m_focused_window->client_fd()); ret.is_error())
 			dwarnln("could not send mouse move event: {}", ret.error());
 		return;
 	}
@@ -807,7 +807,7 @@ void WindowServer::on_mouse_scroll(LibInput::MouseScrollEvent event)
 	{
 		LibGUI::EventPacket::MouseScrollEvent packet;
 		packet.event.scroll = event.scroll;
-		if (auto ret = packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+		if (auto ret = append_serialized_packet(packet, m_focused_window->client_fd()); ret.is_error())
 		{
 			dwarnln("could not send mouse scroll event: {}", ret.error());
 			return;
@@ -831,7 +831,7 @@ void WindowServer::set_focused_window(BAN::RefPtr<Window> window)
 	{
 		LibGUI::EventPacket::WindowFocusEvent packet;
 		packet.event.focused = false;
-		if (auto ret = packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+		if (auto ret = append_serialized_packet(packet, m_focused_window->client_fd()); ret.is_error())
 			dwarnln("could not send window focus event: {}", ret.error());
 	}
 
@@ -851,7 +851,7 @@ void WindowServer::set_focused_window(BAN::RefPtr<Window> window)
 	{
 		LibGUI::EventPacket::WindowFocusEvent packet;
 		packet.event.focused = true;
-		if (auto ret = packet.send_serialized(m_focused_window->client_fd()); ret.is_error())
+		if (auto ret = append_serialized_packet(packet, m_focused_window->client_fd()); ret.is_error())
 			dwarnln("could not send window focus event: {}", ret.error());
 	}
 }
@@ -1526,7 +1526,7 @@ BAN::RefPtr<Window> WindowServer::find_hovered_window() const
 	return {};
 }
 
-bool WindowServer::resize_window(BAN::RefPtr<Window> window, uint32_t width, uint32_t height) const
+bool WindowServer::resize_window(BAN::RefPtr<Window> window, uint32_t width, uint32_t height)
 {
 	if (auto ret = window->resize(width, height); ret.is_error())
 	{
@@ -1538,7 +1538,7 @@ bool WindowServer::resize_window(BAN::RefPtr<Window> window, uint32_t width, uin
 	response.width = window->client_width();
 	response.height = window->client_height();
 	response.smo_key = window->smo_key();
-	if (auto ret = response.send_serialized(window->client_fd()); ret.is_error())
+	if (auto ret = append_serialized_packet(response, window->client_fd()); ret.is_error())
 	{
 		dwarnln("could not respond to window resize request: {}", ret.error());
 		return false;
@@ -1547,13 +1547,10 @@ bool WindowServer::resize_window(BAN::RefPtr<Window> window, uint32_t width, uin
 	return true;
 }
 
-void WindowServer::add_client_fd(int fd)
+BAN::ErrorOr<void> WindowServer::add_client_fd(int fd)
 {
-	if (auto ret = m_client_data.emplace(fd); ret.is_error())
-	{
-		dwarnln("could not add client: {}", ret.error());
-		return;
-	}
+	TRY(m_client_data.emplace(fd));
+	return {};
 }
 
 void WindowServer::remove_client_fd(int fd)
@@ -1612,3 +1609,31 @@ WindowServer::ClientData& WindowServer::get_client_data(int fd)
 
 	ASSERT_NOT_REACHED();
 }
+
+// TODO: this epoll stuff is very hacky
+
+#include <sys/epoll.h>
+
+extern int g_epoll_fd;
+
+template<typename T>
+BAN::ErrorOr<void> WindowServer::append_serialized_packet(const T& packet, int fd)
+{
+	const size_t serialized_size = packet.serialized_size();
+
+	auto& client_data = m_client_data[fd];
+	if (client_data.out_buffer_size + serialized_size > client_data.out_buffer.size())
+		return BAN::Error::from_errno(ENOBUFS);
+
+	if (client_data.out_buffer_size == 0)
+	{
+		epoll_event event { .events = EPOLLIN | EPOLLOUT, .data = { .fd = fd } };
+		if (epoll_ctl(g_epoll_fd, EPOLL_CTL_MOD, fd, &event) == -1)
+			dwarnln("epoll_ctl add EPOLLOUT: {}", strerror(errno));
+	}
+
+	packet.serialize(client_data.out_buffer.span().slice(client_data.out_buffer_size, serialized_size));
+	client_data.out_buffer_size += serialized_size;
+
+	return {};
+}

userspace/programs/WindowServer/WindowServer.h

@@ -20,8 +20,10 @@ class WindowServer
 public:
 	struct ClientData
 	{
-		size_t packet_buffer_nread = 0;
-		BAN::Vector<uint8_t> packet_buffer;
+		size_t in_buffer_size { 0 };
+		BAN::Array<uint8_t, 64 * 1024> in_buffer;
+		size_t out_buffer_size { 0 };
+		BAN::Array<uint8_t, 64 * 1024> out_buffer;
 	};
 
 public:
@@ -54,7 +56,7 @@ public:
 	Rectangle cursor_area() const;
 	Rectangle resize_area(Position cursor) const;
 
-	void add_client_fd(int fd);
+	BAN::ErrorOr<void> add_client_fd(int fd);
 	void remove_client_fd(int fd);
 	ClientData& get_client_data(int fd);
 
@@ -65,11 +67,14 @@ private:
 
 	void mark_pending_sync(Rectangle area);
 
-	bool resize_window(BAN::RefPtr<Window> window, uint32_t width, uint32_t height) const;
+	bool resize_window(BAN::RefPtr<Window> window, uint32_t width, uint32_t height);
 
 	BAN::RefPtr<Window> find_window_with_fd(int fd) const;
 	BAN::RefPtr<Window> find_hovered_window() const;
 
+	template<typename T>
+	BAN::ErrorOr<void> append_serialized_packet(const T& packet, int fd);
+
 private:
 	struct RangeList
 	{

userspace/programs/WindowServer/main.cpp

@@ -145,6 +145,8 @@ int open_server_fd()
 	return server_fd;
 }
 
+int g_epoll_fd = -1;
+
 int main()
 {
 	srand(time(nullptr));
@@ -157,8 +159,8 @@ int main()
 		return 1;
 	}
 
-	int epoll_fd = epoll_create1(EPOLL_CLOEXEC);
-	if (epoll_fd == -1)
+	g_epoll_fd = epoll_create1(EPOLL_CLOEXEC);
+	if (g_epoll_fd == -1)
 	{
 		dwarnln("epoll_create1: {}", strerror(errno));
 		return 1;
@@ -169,7 +171,7 @@ int main()
 			.events = EPOLLIN,
 			.data = { .fd = server_fd },
 		};
-		if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_fd, &event) == -1)
+		if (epoll_ctl(g_epoll_fd, EPOLL_CTL_ADD, server_fd, &event) == -1)
 		{
 			dwarnln("epoll_ctl server: {}", strerror(errno));
 			return 1;
@@ -214,7 +216,7 @@ int main()
 			.events = EPOLLIN,
 			.data = { .fd = keyboard_fd },
 		};
-		if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, keyboard_fd, &event) == -1)
+		if (epoll_ctl(g_epoll_fd, EPOLL_CTL_ADD, keyboard_fd, &event) == -1)
 		{
 			dwarnln("epoll_ctl keyboard: {}", strerror(errno));
 			close(keyboard_fd);
@@ -231,7 +233,7 @@ int main()
 			.events = EPOLLIN,
 			.data = { .fd = mouse_fd },
 		};
-		if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, mouse_fd, &event) == -1)
+		if (epoll_ctl(g_epoll_fd, EPOLL_CTL_ADD, mouse_fd, &event) == -1)
 		{
 			dwarnln("epoll_ctl mouse: {}", strerror(errno));
 			close(mouse_fd);
@@ -283,7 +285,7 @@ int main()
 			timeout.tv_nsec = (sync_interval_us - (current_us - last_sync_us)) * 1000;
 
 		epoll_event events[16];
-		int epoll_events = epoll_pwait2(epoll_fd, events, 16, &timeout, nullptr);
+		int epoll_events = epoll_pwait2(g_epoll_fd, events, 16, &timeout, nullptr);
 		if (epoll_events == -1 && errno != EINTR)
 		{
 			dwarnln("epoll_pwait2: {}", strerror(errno));
@@ -296,25 +298,28 @@ int main()
 			{
 				ASSERT(events[i].events & EPOLLIN);
 
-				int window_fd = accept4(server_fd, nullptr, nullptr, SOCK_NONBLOCK | SOCK_CLOEXEC);
-				if (window_fd == -1)
+				int client_fd = accept4(server_fd, nullptr, nullptr, SOCK_NONBLOCK | SOCK_CLOEXEC);
+				if (client_fd == -1)
 				{
 					dwarnln("accept: {}", strerror(errno));
 					continue;
 				}
 
-				epoll_event event {
-					.events = EPOLLIN,
-					.data = { .fd = window_fd },
-				};
-				if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, window_fd, &event) == -1)
+				epoll_event event { .events = EPOLLIN, .data = { .fd = client_fd } };
+				if (epoll_ctl(g_epoll_fd, EPOLL_CTL_ADD, client_fd, &event) == -1)
 				{
 					dwarnln("epoll_ctl: {}", strerror(errno));
-					close(window_fd);
+					close(client_fd);
+					continue;
+				}
+
+				if (auto ret = window_server.add_client_fd(client_fd); ret.is_error())
+				{
+					dwarnln("add_client: {}", ret.error());
+					close(client_fd);
 					continue;
 				}
 
-				window_server.add_client_fd(window_fd);
 				continue;
 			}
 
@@ -361,80 +366,87 @@ int main()
 			}
 
 			const int client_fd = events[i].data.fd;
-			if (events[i].events & EPOLLHUP)
+			if (events[i].events & (EPOLLHUP | EPOLLERR))
 			{
-				epoll_ctl(epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
+				epoll_ctl(g_epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
 				window_server.remove_client_fd(client_fd);
 				continue;
 			}
 
-			ASSERT(events[i].events & EPOLLIN);
-
 			auto& client_data = window_server.get_client_data(client_fd);
 
-			if (client_data.packet_buffer.empty())
+			if (events[i].events & EPOLLOUT)
 			{
-				uint32_t packet_size;
-				const ssize_t nrecv = recv(client_fd, &packet_size, sizeof(uint32_t), 0);
-				if (nrecv < 0)
-					dwarnln("recv 1: {}", strerror(errno));
-				if (nrecv > 0 && nrecv != sizeof(uint32_t))
-					dwarnln("could not read packet size with a single recv call, closing connection...");
-				if (nrecv != sizeof(uint32_t))
+				ASSERT(client_data.out_buffer_size > 0);
+
+				const ssize_t nsend = send(client_fd, client_data.out_buffer.data(), client_data.out_buffer_size, 0);
+				if (nsend < 0 && !(errno == EWOULDBLOCK || errno == EAGAIN))
 				{
-					epoll_ctl(epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
+					dwarnln("send: {}", strerror(errno));
+					epoll_ctl(g_epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
 					window_server.remove_client_fd(client_fd);
 					break;
 				}
 
-				if (packet_size < 4)
+				if (nsend > 0)
 				{
-					dwarnln("client sent invalid packet, closing connection...");
-					epoll_ctl(epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
-					window_server.remove_client_fd(client_fd);
-					break;
+					client_data.out_buffer_size -= nsend;
+					if (client_data.out_buffer_size == 0)
+					{
+						epoll_event event { .events = EPOLLIN, .data = { .fd = client_fd } };
+						if (epoll_ctl(g_epoll_fd, EPOLL_CTL_MOD, client_fd, &event) == -1)
+							dwarnln("epoll_ctl remove EPOLLOUT: {}", strerror(errno));
+					}
+					else
+					{
+						// TODO: maybe use a ring buffer so we don't have to memmove everything not sent
+						memmove(
+							client_data.out_buffer.data(),
+							client_data.out_buffer.data() + nsend,
+							client_data.out_buffer_size
+						);
+					}
+				}
 			}
 
-				// this is a bit harsh, but i don't want to work on skipping streaming packets
-				if (client_data.packet_buffer.resize(packet_size).is_error())
-				{
-					dwarnln("could not allocate memory for client packet, closing connection...");
-					epoll_ctl(epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
-					window_server.remove_client_fd(client_fd);
-					break;
-				}
-
-				client_data.packet_buffer_nread = 0;
+			if (!(events[i].events & EPOLLIN))
 				continue;
-			}
 
+			{
 				const ssize_t nrecv = recv(
 					client_fd,
-				client_data.packet_buffer.data() + client_data.packet_buffer_nread,
-				client_data.packet_buffer.size() - client_data.packet_buffer_nread,
+					client_data.in_buffer.data() + client_data.in_buffer_size,
+					client_data.in_buffer.size() - client_data.in_buffer_size,
 					0
 				);
-			if (nrecv < 0)
-				dwarnln("recv 2: {}", strerror(errno));
-			if (nrecv <= 0)
+				if (nrecv < 0 && !(errno == EWOULDBLOCK || errno == EAGAIN))
 				{
-				epoll_ctl(epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
+					dwarnln("recv: {}", strerror(errno));
+					epoll_ctl(g_epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
 					window_server.remove_client_fd(client_fd);
 					break;
 				}
+				if (nrecv > 0)
+					client_data.in_buffer_size += nrecv;
+			}
 
-			client_data.packet_buffer_nread += nrecv;
-			if (client_data.packet_buffer_nread < client_data.packet_buffer.size())
-				continue;
+			size_t bytes_handled = 0;
+			while (client_data.in_buffer_size - bytes_handled >= sizeof(LibGUI::PacketHeader))
+			{
+				BAN::ConstByteSpan packet_span = client_data.in_buffer.span().slice(bytes_handled, client_data.in_buffer_size - bytes_handled);
+				const auto header = packet_span.as<const LibGUI::PacketHeader>();
+				if (packet_span.size() < header.size || header.size < sizeof(LibGUI::PacketHeader))
+					break;
+				packet_span = packet_span.slice(0, header.size);
 
-			ASSERT(client_data.packet_buffer.size() >= sizeof(uint32_t));
-
-			switch (*reinterpret_cast<LibGUI::PacketType*>(client_data.packet_buffer.data()))
+				switch (header.type)
 				{
 #define WINDOW_PACKET_CASE(enum, function) \
 					case LibGUI::PacketType::enum: \
-					if (auto ret = LibGUI::WindowPacket::enum::deserialize(client_data.packet_buffer.span()); !ret.is_error()) \
+						if (auto ret = LibGUI::WindowPacket::enum::deserialize(packet_span); !ret.is_error()) \
 							window_server.function(client_fd, ret.release_value()); \
+						else \
+							derrorln("invalid packet: {}", ret.error()); \
 						break
 					WINDOW_PACKET_CASE(WindowCreate,           on_window_create);
 					WINDOW_PACKET_CASE(WindowInvalidate,       on_window_invalidate);
@@ -449,11 +461,32 @@ int main()
 					WINDOW_PACKET_CASE(WindowSetCursor,        on_window_set_cursor);
 #undef WINDOW_PACKET_CASE
 					default:
-					dprintln("unhandled packet type: {}", *reinterpret_cast<uint32_t*>(client_data.packet_buffer.data()));
+						dprintln("unhandled packet type: {}", static_cast<uint32_t>(header.type));
+						break;
 				}
 
-			client_data.packet_buffer.clear();
-			client_data.packet_buffer_nread = 0;
+				bytes_handled += header.size;
+			}
+
+			// NOTE: this will only move a single partial packet, so this is fine
+			client_data.in_buffer_size -= bytes_handled;
+			memmove(
+				client_data.in_buffer.data(),
+				client_data.in_buffer.data() + bytes_handled,
+				client_data.in_buffer_size
+			);
+
+			if (client_data.in_buffer_size >= sizeof(LibGUI::PacketHeader))
+			{
+				const auto header = BAN::ConstByteSpan(client_data.in_buffer.span()).as<const LibGUI::PacketHeader>();
+				if (header.size < sizeof(LibGUI::PacketHeader) || header.size > client_data.in_buffer.size())
+				{
+					dwarnln("client tried to send a {} byte packet", header.size);
+					epoll_ctl(g_epoll_fd, EPOLL_CTL_DEL, client_fd, nullptr);
+					window_server.remove_client_fd(client_fd);
+					break;
+				}
+			}
 		}
 	}
 }