Transparent proxy mode (#823)

Adds a **transparent TCP proxy mode** to zenserver (activated via `zenserver proxy`), allowing it to sit between clients and upstream Zen servers to inspect and monitor HTTP/1.x traffic in real time. Primarily useful during development, to be able to observe multi-server/client interactions in one place.

- **Dedicated proxy port** -- Proxy mode defaults to port 8118 with its own data directory to avoid collisions with a normal zenserver instance.
- **TCP proxy core** (`src/zenserver/proxy/`) -- A new transparent TCP proxy that forwards connections to upstream targets, with support for both TCP/IP and Unix socket listeners. Multi-threaded I/O for connection handling. Supports Unix domain sockets for both upstream/downstream.
- **HTTP traffic inspection** -- Parses HTTP/1.x request/response streams inline to extract method, path, status, content length, and WebSocket upgrades without breaking the proxied data.
- **Proxy dashboard** -- A web UI showing live connection stats, per-target request counts, active connections, bytes transferred, and client IP/session ID rollups.
- **Server mode display** -- Dashboard banner now shows the running server mode (Zen Proxy, Zen Compute, etc.).

Supporting changes included in this branch:

- **Wildcard log level matching** -- Log levels can now be set per-category using wildcard patterns (e.g. `proxy.*=debug`).
- **`zen down --all`** -- New flag to shut down all running zenserver instances; also used by the new `xmake kill` task.
- Minor test stability fixes (flaky hash collisions, per-thread RNG seeds).
- Support ZEN_MALLOC environment variable for default allocator selection and switch default to rpmalloc
- Fixed sentry-native build to allow LTO on Windows

1 files changed, 96 insertions, 0 deletions

diff --git a/src/zenserver/proxy/zenproxyserver.h b/src/zenserver/proxy/zenproxyserver.h
new file mode 100644
index 000000000..7dad748cf
--- /dev/null
+++ b/src/zenserver/proxy/zenproxyserver.h
@@ -0,0 +1,96 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include "zenserver.h"
+
+#include "proxy/tcpproxy.h"
+
+#include <memory>
+#include <thread>
+#include <vector>
+
+namespace zen {
+class HttpApiService;
+class HttpFrontendService;
+class HttpProxyStatsService;
+}  // namespace zen
+
+namespace cxxopts {
+class Options;
+}
+namespace zen::LuaConfig {
+struct Options;
+}
+
+namespace zen {
+
+struct ZenProxyServerConfig : public ZenServerConfig
+{
+	static constexpr int kDefaultProxyPort = 8118;
+
+	std::vector<ProxyMapping> ProxyMappings;
+};
+
+struct ZenProxyServerConfigurator : public ZenServerConfiguratorBase
+{
+	ZenProxyServerConfigurator(ZenProxyServerConfig& ServerOptions)
+	: ZenServerConfiguratorBase(ServerOptions)
+	, m_ServerOptions(ServerOptions)
+	{
+	}
+
+	~ZenProxyServerConfigurator() = default;
+
+private:
+	virtual void AddCliOptions(cxxopts::Options& Options) override;
+	virtual void AddConfigOptions(LuaConfig::Options& Options) override;
+	virtual void ApplyOptions(cxxopts::Options& Options) override;
+	virtual void OnConfigFileParsed(LuaConfig::Options& LuaOptions) override;
+	virtual void ValidateOptions() override;
+
+	ZenProxyServerConfig& m_ServerOptions;
+
+	std::vector<std::string> m_RawProxyMappings;
+};
+
+class ZenProxyServerMain : public ZenServerMain
+{
+public:
+	ZenProxyServerMain(ZenProxyServerConfig& ServerOptions);
+	virtual void DoRun(ZenServerState::ZenServerEntry* Entry) override;
+
+	ZenProxyServerMain(const ZenProxyServerMain&) = delete;
+	ZenProxyServerMain& operator=(const ZenProxyServerMain&) = delete;
+
+	typedef ZenProxyServerConfig	   Config;
+	typedef ZenProxyServerConfigurator Configurator;
+
+private:
+	ZenProxyServerConfig& m_ServerOptions;
+};
+
+class ZenProxyServer : public ZenServerBase
+{
+	ZenProxyServer& operator=(ZenProxyServer&&) = delete;
+	ZenProxyServer(ZenProxyServer&&)			= delete;
+
+public:
+	ZenProxyServer();
+	~ZenProxyServer();
+
+	int	 Initialize(const ZenProxyServerConfig& ServerConfig, ZenServerState::ZenServerEntry* ServerEntry);
+	void Run();
+	void Cleanup();
+
+private:
+	asio::io_context							  m_ProxyIoContext;
+	std::unique_ptr<asio::io_context::work>		  m_ProxyIoWorkGuard;
+	std::vector<std::thread>					  m_ProxyIoThreads;
+	std::vector<std::unique_ptr<TcpProxyService>> m_ProxyServices;
+	std::unique_ptr<HttpApiService>				  m_ApiService;
+	std::unique_ptr<HttpFrontendService>		  m_FrontendService;
+	std::unique_ptr<HttpProxyStatsService>		  m_ProxyStatsService;
+};
+
+}  // namespace zen