/*
 * Copyright (C) 1994-2021 Altair Engineering, Inc.
 * For more information, contact Altair at www.altair.com.
 *
 * This file is part of both the OpenPBS software ("OpenPBS")
 * and the PBS Professional ("PBS Pro") software.
 *
 * Open Source License Information:
 *
 * OpenPBS is free software. You can redistribute it and/or modify it under
 * the terms of the GNU Affero General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * OpenPBS 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 Affero General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Commercial License Information:
 *
 * PBS Pro is commercially licensed software that shares a common core with
 * the OpenPBS software.  For a copy of the commercial license terms and
 * conditions, go to: (http://www.pbspro.com/agreement.html) or contact the
 * Altair Legal Department.
 *
 * Altair's dual-license business model allows companies, individuals, and
 * organizations to create proprietary derivative works of OpenPBS and
 * distribute them - whether embedded or bundled with other software -
 * under a commercial license agreement.
 *
 * Use of Altair's trademarks, including but not limited to "PBS™",
 * "OpenPBS®", "PBS Professional®", and "PBS Pro™" and Altair's logos is
 * subject to Altair's trademark licensing policies.
 */
#include <pbs_config.h>

#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include "server_limits.h"
#include "pbs_ifl.h"
#include "log.h"

/**
 * @brief
 *	Where possible enable protection for the daemon from the OS.
 *
 * @par	Linux
 *	Protect from OOM (Out of Memory) killer
 *
 * @param[in] pid_t pid - pid of process to protect, if 0 then myself.
 * @param[in] enum PBS_Daemon_Protect action - turn on/off proection:
 *	PBS_DAEMON_PROTECT_ON/OFF
 */

void
daemon_protect(pid_t pid, enum PBS_Daemon_Protect action)
{

#ifdef linux
	int fd;
	char fname[MAXPATHLEN + 1];
	struct oom_protect {
		char *oom_value[2]; /* value to write: unprotect/protect */
		char *oom_path;	    /* path to which to write */
	};
	static struct oom_protect oom_protect_old = {
		{
			"0\n",	/* unprotect value */
			"-17\n" /* protect value   */
		},
		"/proc/%ld/oom_adj"};
	static struct oom_protect oom_protect_new = {
		{
			"0\n",	  /* unprotect value */
			"-1000\n" /* protect value   */
		},
		"/proc/%ld/oom_score_adj"};

	if (pid == 0)
		pid = getpid(); /* use my pid */

	/**
	 *	for Linux:  Need to protect daemons from the Out of Memory killer.
	 *
	 *	First try to set /proc/<pid>/oom_score_adj to -1000 to protect
	 *	or 0 to unprotect.
	 *	If oom_score_adj is does not exist, try setting /proc/<pid>oom_adj
	 *	which is older to -17 to protect or 0 to unprotect.
	 */
	snprintf(fname, MAXPATHLEN, oom_protect_new.oom_path, pid);
	if ((fd = open(fname, O_WRONLY | O_TRUNC)) != -1) {
		if (write(fd, oom_protect_new.oom_value[(int) action], strlen(oom_protect_new.oom_value[(int) action])) == -1) 
				log_errf(-1, __func__, "write failed. ERR: %s", strerror(errno));
	} else {

		/* failed to open "oom_score_adj", now try "oom_adj" */
		/* found in older Linux kernels			     */
		snprintf(fname, MAXPATHLEN, oom_protect_old.oom_path, pid);
		if ((fd = open(fname, O_WRONLY | O_TRUNC)) != -1) {
			if (write(fd, oom_protect_old.oom_value[(int) action], strlen(oom_protect_old.oom_value[(int) action])) == -1) 
				log_errf(-1, __func__, "write failed. ERR: %s", strerror(errno));
		}
	}
	if (fd != -1)
		close(fd);
#endif /* linux */

	/**
	 *	For any other OS, we don't do anything currently.
	 */
	return;
}