netplay: introduce abstractions for client/server-side sockets and co…

…nnection providers

This patch introduces multiple high-level abstractions over raw low-level
sockets, which are necessary for supporting network backends other
than default legacy `TCP_DIRECT` implementation:

1. `WzConnectionProvider` - abstracts the way WZ establishes
   server-side and client-side connections. This thing effectively
   provides usable listen sockets and client connections to work with,
   hence the name.
2. `IListenSocket` - abstraction over listen sockets.
3. `IClientConnection` - abstraction over client-side sockets (and
   also server-side connections to the game clients).
4. `IConnectionPollGroup` - generalization of socket sets for polling
   multiple connections in one go.
5. `ConnectionProviderRegistry` - trivial singleton class providing
   storage for connection providers.
6. `ConnectionAddress` - opaque connection address object, aimed
   to replace direct uses of `addrinfo` and provide a bit more
   abstract way to represent connection credentials. Still looks like
   a crutch right now, but it's better than nothing, nonetheless.

The existing implementation in `netplay/netsocket.h(.cpp)` has been
moved to the `tcp` subfolder and wrapped entirely into the `tcp`
namespace.

The patch provides `TCP*`-prefixed implementations of the base
interfaces mentioned above, which are implemented in terms of the
old `netsocket` code.

There's now a `ConnectionProviderType::TCP_DIRECT` enumeration
descriptor for accessing the default connection provider.

All uses in the high-level code (`netplay.cpp`, `joiningscreen.cpp`)
are amended appropriately to use the all-new high-level abstractions
instead of old low-level tcp-specific `Socket` and `SocketSet`.

NOTE: there are still a few functions from the `tcp::` namespace
used directly in the Discord RPC integration code, but these
shouldn't pose any problem to either extract these into a more generic
abstraction layer or to be rewritten not to use these functions at all,
because they don't actually use any low-level stuff that's hard to
refactor.

Signed-off-by: Pavel Solodovnikov <[email protected]>

lib/netplay/CMakeLists.txt

@@ -26,8 +26,16 @@ add_dependencies(autorevision_netcodeversion autorevision) # Ensure ordering and
 ############################
 # netplay library
 
-file(GLOB HEADERS "*.h")
-file(GLOB SRC "*.cpp")
+file(GLOB_RECURSE HEADERS "*.h")
+file(GLOB_RECURSE SRC "*.cpp")
+
+if(MSVC AND CMAKE_VERSION VERSION_GREATER 3.7)
+	# Automatic detection of source groups via `source_group(TREE <root>)` syntax
+	# has been introduced in CMake 3.8.
+	# Please consult https://cmake.org/cmake/help/latest/command/source_group.html for additional info.
+	source_group(TREE "${CMAKE_CURRENT_LIST_DIR}" PREFIX "Sources" FILES ${SRC})
+	source_group(TREE "${CMAKE_CURRENT_LIST_DIR}" PREFIX "Headers" FILES ${HEADERS})
+endif()
 
 find_package (Threads REQUIRED)
 find_package (ZLIB REQUIRED)

lib/netplay/client_connection.h

@@ -0,0 +1,120 @@
+/*
+	This file is part of Warzone 2100.
+	Copyright (C) 2024  Warzone 2100 Project
+	Warzone 2100 is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+	Warzone 2100 is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+	GNU General Public License for more details.
+	You should have received a copy of the GNU General Public License
+	along with Warzone 2100; if not, write to the Free Software
+	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#pragma once
+
+#include <string>
+#include <stddef.h>
+
+#include "lib/framework/types.h" // bring in `ssize_t` for MSVC
+#include "lib/netplay/net_result.h"
+
+/// <summary>
+/// Basic abstraction over client connection sockets.
+///
+/// These are capable of reading (`readAll` and `readNoInt`) and
+/// writing data (via `writeAll()` + `flush()` combination).
+///
+/// The internal implementation may also implement advanced compression mechanisms
+/// on top of these connections by providing non-trivial `enableCompression()` overload.
+///
+///	In this case, `writeAll()` should somehow accumulate the data into a write queue,
+/// compressing the outcoming data on-the-fly; and `flush()` should empty the write queue
+/// and actually post a message to the transmission queue, which, in turn, will be emptied
+/// by the internal connection interface in a timely manner, when there are enough messages
+/// to be sent over the network.
+/// </summary>
+class IClientConnection
+{
+public:
+
+	virtual ~IClientConnection() = default;
+
+	/// <summary>
+	/// Read exactly `size` bytes into `buf` buffer.
+	/// Supports setting a timeout value in milliseconds.
+	/// </summary>
+	/// <param name="buf">Destination buffer to read the data into.</param>
+	/// <param name="size">The size of data to be read in bytes.</param>
+	/// <param name="timeout">Timeout value in milliseconds.</param>
+	/// <returns>On success, returns the number of bytes read;
+	/// On failure, returns an `std::error_code` (having `GenericSystemErrorCategory` error category)
+	/// describing the actual error.</returns>
+	virtual net::result<ssize_t> readAll(void* buf, size_t size, unsigned timeout) = 0;
+	/// <summary>
+	/// Reads at most `max_size` bytes into `buf` buffer.
+	/// Raw count of bytes (after compression) is returned in `rawByteCount`.
+	/// </summary>
+	/// <param name="buf">Destination buffer to read the data into.</param>
+	/// <param name="max_size">The maximum number of bytes to read from the client socket.</param>
+	/// <param name="rawByteCount">Output parameter: Raw count of bytes (after compression).</param>
+	/// <returns>On success, returns the number of bytes read;
+	/// On failure, returns an `std::error_code` (having `GenericSystemErrorCategory` error category)
+	/// describing the actual error.</returns>
+	virtual net::result<ssize_t> readNoInt(void* buf, size_t max_size, size_t* rawByteCount) = 0;
+	/// <summary>
+	/// Nonblocking write of `size` bytes to the socket. The data will be written to a
+	/// separate write queue in asynchronous manner, possibly by a separate thread.
+	/// Raw count of bytes (after compression) will be returned in `rawByteCount`, which
+	/// will often be 0 until the socket is flushed.
+	///
+	/// The reason for this method to be async is that in some cases we want
+	/// client connections to have compression mechanism enabled. This naturally
+	/// introduces the 2-phase write process, which involves a write queue (accumulating
+	/// the data for compression on-the-fly) and a submission (transmission)
+	/// queue (for transmitting of compressed and assembled messages),
+	/// which is managed by the network backend implementation.
+	/// </summary>
+	/// <param name="buf">Source buffer to read the data from.</param>
+	/// <param name="size">The number of bytes to write to the socket.</param>
+	/// <param name="rawByteCount">Output parameter: raw count of bytes (after compression) written.</param>
+	/// <returns>The total number of bytes written.</returns>
+	virtual net::result<ssize_t> writeAll(const void* buf, size_t size, size_t* rawByteCount) = 0;
+	/// <summary>
+	/// This method indicates whether the socket has some data ready to be read (i.e.
+	/// whether the next `readAll/readNoInt` operation will execute without blocking or not).
+	/// </summary>
+	virtual bool readReady() const = 0;
+	/// <summary>
+	/// Actually sends the data written with `writeAll()`. Only useful with sockets
+	/// which have compression enabled.
+	/// Note that flushing too often makes compression less effective.
+	/// Raw count of bytes (after compression) is returned in `rawByteCount`.
+	/// </summary>
+	/// <param name="rawByteCount">Raw count of bytes (after compression) as written
+	/// to the submission queue by the flush operation.</param>
+	virtual void flush(size_t* rawByteCount) = 0;
+	/// <summary>
+	/// Enables compression for the current socket.
+	///
+	/// This makes all subsequent write operations asynchronous, plus
+	/// the written data will need to be flushed explicitly at some point.
+	/// </summary>
+	virtual void enableCompression() = 0;
+	/// <summary>
+	/// Enables or disables the use of Nagle algorithm for the socket.
+	///
+	/// For direct TCP connections this is equivalent to setting `TCP_NODELAY` to the
+	/// appropriate value (i.e.:
+	/// `enable == true`  <=> `TCP_NODELAY == false`;
+	/// `enable == false` <=> `TCP_NODELAY == true`).
+	/// </summary>
+	virtual void useNagleAlgorithm(bool enable) = 0;
+	/// <summary>
+	/// Returns textual representation of the socket's connection address.
+	/// </summary>
+	virtual std::string textAddress() const = 0;
+};

lib/netplay/connection_address.cpp

@@ -0,0 +1,65 @@
+/*
+	This file is part of Warzone 2100.
+	Copyright (C) 2024  Warzone 2100 Project
+
+	Warzone 2100 is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+
+	Warzone 2100 is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Warzone 2100; if not, write to the Free Software
+	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#include "lib/netplay/connection_address.h"
+#include "lib/netplay/tcp/netsocket.h" // for `resolveHost`
+
+#include "lib/framework/frame.h" // for `ASSERT`
+
+struct ConnectionAddress::Impl final
+{
+	explicit Impl(SocketAddress* addr)
+		: mAddr_(addr)
+	{}
+
+	~Impl()
+	{
+		ASSERT(mAddr_ != nullptr, "Invalid addrinfo stored in the connection address");
+		freeaddrinfo(mAddr_);
+	}
+
+	SocketAddress* mAddr_;
+};
+
+ConnectionAddress::ConnectionAddress() = default;
+ConnectionAddress::ConnectionAddress(ConnectionAddress&&) = default;
+ConnectionAddress::~ConnectionAddress() = default;
+
+const SocketAddress* ConnectionAddress::asRawSocketAddress() const
+{
+	return mPimpl_->mAddr_;
+}
+
+
+net::result<ConnectionAddress> ConnectionAddress::parse(const char* hostname, uint16_t port)
+{
+	ConnectionAddress res;
+	const auto addr = tcp::resolveHost(hostname, port);
+	if (!addr.has_value())
+	{
+		return tl::make_unexpected(addr.error());
+	}
+	res.mPimpl_ = std::make_unique<Impl>(addr.value());
+	return net::result<ConnectionAddress>{std::move(res)};
+}
+
+net::result<ConnectionAddress> ConnectionAddress::parse(const std::string& hostname, uint16_t port)
+{
+	return parse(hostname.c_str(), port);
+}

lib/netplay/connection_address.h

@@ -0,0 +1,72 @@
+/*
+	This file is part of Warzone 2100.
+	Copyright (C) 2024  Warzone 2100 Project
+	Warzone 2100 is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+	Warzone 2100 is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+	GNU General Public License for more details.
+	You should have received a copy of the GNU General Public License
+	along with Warzone 2100; if not, write to the Free Software
+	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#pragma once
+
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+
+#include "lib/netplay/net_result.h"
+
+#if defined WZ_OS_UNIX
+# include <netdb.h>
+#elif defined WZ_OS_WIN
+# include <ws2tcpip.h>
+#endif
+
+typedef struct addrinfo SocketAddress;
+
+/// <summary>
+/// Opaque class representing abstract connection address to use with various
+/// network backend implementations. The internal representation is made
+/// hidden on purpose since we don't want to actually leak internal data layout
+/// to clients.
+///
+/// Instead, we would like to introduce "conversion routines" yielding
+/// various representations for convenient consumption with various network
+/// backends.
+///
+/// NOTE: this class may or may not represent a chain of resolved network addresses
+/// instead of just a single one, much like a `addrinfo` structure.
+///
+/// Currently, only knows how to convert itself to `addrinfo` struct,
+/// which is used with the `TCP_DIRECT` network backend.
+///
+/// New conversion routines should be introduced for other network backends,
+/// if deemed necessary.
+/// </summary>
+class ConnectionAddress
+{
+public:
+
+	ConnectionAddress();
+	ConnectionAddress(ConnectionAddress&&);
+	ConnectionAddress(const ConnectionAddress&) = delete;
+	~ConnectionAddress();
+
+	static net::result<ConnectionAddress> parse(const char* hostname, uint16_t port);
+	static net::result<ConnectionAddress> parse(const std::string& hostname, uint16_t port);
+
+	// NOTE: The lifetime of the returned `addrinfo` struct is bounded by the parent object's lifetime!
+	const SocketAddress* asRawSocketAddress() const;
+
+private:
+
+	struct Impl;
+	std::unique_ptr<Impl> mPimpl_;
+};

lib/netplay/connection_poll_group.h

@@ -0,0 +1,42 @@
+/*
+	This file is part of Warzone 2100.
+	Copyright (C) 2024  Warzone 2100 Project
+	Warzone 2100 is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+	Warzone 2100 is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+	GNU General Public License for more details.
+	You should have received a copy of the GNU General Public License
+	along with Warzone 2100; if not, write to the Free Software
+	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#pragma once
+
+class IClientConnection;
+
+/// <summary>
+/// Abstract representation of a poll group comprised of several client connections.
+/// </summary>
+class IConnectionPollGroup
+{
+public:
+
+	virtual ~IConnectionPollGroup() = default;
+
+	/// <summary>
+	/// Polls the sockets in the poll group for updates.
+	/// </summary>
+	/// <param name="timeout">Timeout value after which the internal implementation should abandon
+	/// polling the client connections and return.</param>
+	/// <returns>On success, returns the number of connection descriptors in the poll group.
+	/// On failure, `0` can returned if the timeout expired before any connection descriptors
+	/// became ready, or `-1` if there was an error during the internal poll operation.</returns>
+	virtual int checkSockets(unsigned timeout) = 0;
+
+	virtual void add(IClientConnection* conn) = 0;
+	virtual void remove(IClientConnection* conn) = 0;
+};

lib/netplay/connection_provider_registry.cpp

@@ -0,0 +1,38 @@
+/*
+	This file is part of Warzone 2100.
+	Copyright (C) 2024  Warzone 2100 Project
+
+	Warzone 2100 is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+
+	Warzone 2100 is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Warzone 2100; if not, write to the Free Software
+	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#include <stdexcept>
+
+#include "lib/netplay/connection_provider_registry.h"
+
+ConnectionProviderRegistry& ConnectionProviderRegistry::Instance()
+{
+	static ConnectionProviderRegistry instance;
+	return instance;
+}
+
+WzConnectionProvider& ConnectionProviderRegistry::Get(ConnectionProviderType pt)
+{
+	const auto it = registeredProviders_.find(pt);
+	if (it == registeredProviders_.end())
+	{
+		throw std::runtime_error("Attempt to get nonexistent connection provider");
+	}
+	return *it->second;
+}