From c49b0a053c5e28de1afa83600ebffd383766e38a Mon Sep 17 00:00:00 2001
From: Liam Mitchell <liam.mitchell@epicgames.com>
Date: Thu, 27 Feb 2025 02:16:10 +0000
Subject: Implementation of service commands for Linux.

---
 src/zenutil/service.cpp | 59 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 46 insertions(+), 13 deletions(-)

(limited to 'src/zenutil/service.cpp')

diff --git a/src/zenutil/service.cpp b/src/zenutil/service.cpp
index 8d6b399ca..c156b001c 100644
--- a/src/zenutil/service.cpp
+++ b/src/zenutil/service.cpp
@@ -6,6 +6,7 @@
 #include <zencore/process.h>
 #include <zencore/scopeguard.h>
 #include <zencore/zencore.h>
+#include <string_view>
 
 #if ZEN_PLATFORM_WINDOWS
 #	include <zencore/windows.h>
@@ -23,6 +24,7 @@
 
 #	include <unistd.h>
 #	include <sys/stat.h>
+#	include <regex>
 #endif
 
 namespace zen {
@@ -258,7 +260,6 @@ namespace {
 
 #if ZEN_PLATFORM_MAC || ZEN_PLATFORM_LINUX
 
-	// TODO: Is this good enough to capture all output/errors/return codes?
 	std::pair<int, std::string> ExecuteProgram(std::string_view Cmd)
 	{
 		std::string Data;
@@ -289,10 +290,11 @@ namespace {
 			int Status = pclose(Stream);
 			if (Status < 0)
 			{
+				ZEN_DEBUG("Command {} returned {}, errno {}", Command, Status, errno);
 				return {Status, Data};
 			}
 			uint64_t WaitMS = 100;
-			if (!WIFEXITED(Status))
+			if (WIFEXITED(Status))
 			{
 				Res = WEXITSTATUS(Status);
 			}
@@ -319,10 +321,9 @@ namespace {
 	std::string BuildUnitFile(std::string_view			   ServiceName,
 							  const std::filesystem::path& ExecutablePath,
 							  std::string_view			   CommandLineOptions,
-							  std::string_view			   AliasName)
+							  std::string_view			   AliasName,
+							  std::string_view			   UserName)
 	{
-		// TODO: Revise to make sure the unit file is correct
-		// TODO: Do we need a separate config file or is that optional?
 		return fmt::format(
 			"[Unit]\n"
 			"Description={}\n"
@@ -336,14 +337,14 @@ namespace {
 			"Type=simple\n"
 			"Restart=always\n"
 			"RestartSec=1\n"
-			"User=serviceuser\n"
+			"User={}\n"
 			"ExecStart={} {}\n"
-			"Restart=always\n"
 			"RuntimeDirectory={}\n"
 			"[Install]\n"
 			"Alias={}\n"
 			"WantedBy=multi-user.target",
 			ServiceName,
+			UserName,
 			ExecutablePath,
 			CommandLineOptions,
 			ExecutablePath.parent_path(),
@@ -881,12 +882,23 @@ StopService(std::string_view ServiceName)
 std::error_code
 InstallService(std::string_view ServiceName, const ServiceSpec& Spec)
 {
-	// TODO: Do we need to create a separate user for the service or is running as root OK?
-
 	const std::string			UnitName		= GetUnitName(ServiceName);
 	const std::filesystem::path ServiceUnitPath = GetServiceUnitPath(UnitName);
+	std::string UserName = Spec.UserName;
+
+	if (UserName == "")
+	{
+		std::pair<int, std::string> UserResult = ExecuteProgram("echo $SUDO_USER");
+		if (UserResult.first != 0 || UserResult.second.empty())
+		{
+			ZEN_ERROR("Unable to determine current user");	
+			return MakeErrorCode(UserResult.first);
+		}
+
+		UserName = UserResult.second;
+	}
 
-	std::string UnitFile = BuildUnitFile(ServiceName, Spec.ExecutablePath, Spec.CommandLineOptions, UnitName);
+	std::string UnitFile = BuildUnitFile(ServiceName, Spec.ExecutablePath, Spec.CommandLineOptions, UnitName, UserName);
 	ZEN_DEBUG("Writing systemd unit file to {}", ServiceUnitPath.string());
 	try
 	{
@@ -963,13 +975,34 @@ QueryInstalledService(std::string_view ServiceName, ServiceInfo& OutInfo)
 	if (std::filesystem::is_regular_file(ServiceUnitPath))
 	{
 		OutInfo.Status = ServiceStatus::Stopped;
-		// TODO: Read and parse unit file ?
 
-		std::pair<int, std::string> Res = ExecuteProgram(fmt::format("systemctl status {}", UnitName));
+		std::pair<int, std::string> Res = ExecuteProgram(fmt::format("systemctl is-active --quiet {}", UnitName));
 		if (Res.first == 0)
 		{
-			// TODO: What does status really return and what info can we use here to get the ServiceInfo complete?
 			OutInfo.Status = ServiceStatus::Running;
+
+			std::pair<int, std::string> ShowResult = ExecuteProgram(fmt::format("systemctl show -p ExecStart {}", UnitName));
+			if (ShowResult.first == 0)
+			{
+				std::regex Regex(R"~(ExecStart=\{ path=(.*?) ; argv\[\]=(.*?) ;)~");
+				std::smatch Match;
+
+				if (std::regex_search(ShowResult.second, Match, Regex))
+				{
+					std::string Executable = Match[1].str();
+					std::string CommandLine = Match[2].str();
+					OutInfo.Spec.ExecutablePath = Executable;
+					OutInfo.Spec.CommandLineOptions = CommandLine.substr(Executable.size(), CommandLine.size());
+				}
+				else
+				{
+					ZEN_WARN("Failed to parse output of systemctl show: {}", ShowResult.second);
+				}
+			}
+			else
+			{
+				ZEN_WARN("Failed to read start info from systemctl: error code {}", ShowResult.first);
+			}
 		}
 		else
 		{
-- 
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