feat(Core): Linux: Support systemd socket activation for the worldserver game socket (#21998)

src/common/Utilities/Systemd.cpp

@@ -0,0 +1,59 @@
+/*
+ * This file is part of the AzerothCore Project. See AUTHORS file for Copyright information.
+ *
+ * Portions of this file are derived from systemd, licensed under:
+ * - GPL-2.0-or-later (if the original systemd file was GPL-2.0+)
+ *   OR
+ * - LGPL-2.1-or-later, relicensed under GPL-2.0-or-later as permitted by LGPL-2.1+
+ *
+ * Original systemd copyright:
+ *   Copyright (c) the systemd contributors.
+ *
+ * This program 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.
+ *
+ * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#if defined(__linux__)
+#include "Log.h"
+#include "StringConvert.h"
+#include <cstdlib>
+#include <unistd.h>
+#include <string>
+
+int get_listen_fd()
+{
+    char* const listen_pid = std::getenv("LISTEN_PID");
+    char* const listen_fds = std::getenv("LISTEN_FDS");
+    if (!listen_pid || !listen_fds)
+        return 0;
+
+    pid_t pid = Acore::StringTo<int>(listen_pid).value_or(0);
+    if (pid != getpid())
+        return 0;
+
+    int fds = Acore::StringTo<int>(listen_fds).value_or(0);
+    if (fds <= 0)
+        return 0;
+
+    if (fds > 1)
+        LOG_WARN("network", "Multiple file descriptors received from systemd socket activation, only the first will be used");
+
+    return 3;
+}
+#else
+// On non-Linux systems, just return 0 (no socket activation)
+int get_listen_fd()
+{
+    return 0;
+}
+#endif

src/common/Utilities/Systemd.h

@@ -0,0 +1,31 @@
+/*
+ * This file is part of the AzerothCore Project. See AUTHORS file for Copyright information.
+ *
+ * Portions of this file are derived from systemd, licensed under:
+ * - GPL-2.0-or-later (if the original systemd file was GPL-2.0+)
+ *   OR
+ * - LGPL-2.1-or-later, relicensed under GPL-2.0-or-later as permitted by LGPL-2.1+
+ *
+ * Original systemd copyright:
+ *   Copyright (c) the systemd contributors.
+ *
+ * This program 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.
+ *
+ * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _SYSTEMD_H_
+#define _SYSTEMD_H_
+
+int get_listen_fd();
+
+#endif