+/* Copyright (c) 2008 The Board of Trustees of The Leland Stanford
+ * Junior University
+ *
+ * We are making the OpenFlow specification and associated documentation
+ * (Software) available for public use and benefit with the expectation
+ * that others will use, modify and enhance the Software and contribute
+ * those enhancements back to the community. However, since we would
+ * like to make the Software available for broadest use, with as few
+ * restrictions as possible permission is hereby granted, free of
+ * charge, to any person obtaining a copy of this Software to deal in
+ * the Software under the copyrights without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * The name and trademarks of copyright holder(s) may NOT be used in
+ * advertising or publicity pertaining to the Software or any
+ * derivatives without specific, written prior permission.
+ */
+
+#include "daemon.h"
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include "fatal-signal.h"
+#include "util.h"
+
+#define THIS_MODULE VLM_daemon
+#include "vlog.h"
+
+/* Should we run in the background? */
+static bool detach;
+
+/* Name of pidfile (null if none). */
+static char *pidfile;
+
+/* Sets up a following call to daemonize() to create a pidfile named 'name'.
+ * If 'name' begins with '/', then it is treated as an absolute path.
+ * Otherwise, it is taken relative to RUNDIR, which is $(prefix)/var/run by
+ * default. */
+void
+set_pidfile(const char *name)
+{
+ free(pidfile);
+ pidfile = *name == '/' ? xstrdup(name) : xasprintf("%s/%s", RUNDIR, name);
+}
+
+/* Sets up a following call to daemonize() to detach from the foreground
+ * session, running this process in the background. */
+void
+set_detach(void)
+{
+ detach = true;
+}
+
+/* If a pidfile has been configured, creates it and stores 'pid' in it. It is
+ * the caller's responsibility to make sure that the pidfile will eventually
+ * be deleted. */
+static void
+make_pidfile(pid_t pid)
+{
+ if (pidfile) {
+ FILE *file;
+
+ file = fopen(pidfile, "w");
+ if (file) {
+ fprintf(file, "%ld\n", (long int) pid);
+ fclose(file);
+ } else {
+ VLOG_ERR("failed to create \"%s\": %s", pidfile, strerror(errno));
+ }
+ free(pidfile);
+ pidfile = NULL;
+ }
+}
+
+/* If configured with set_pidfile() or set_detach(), creates the pid file and
+ * detaches from the foreground session. */
+void
+daemonize(void)
+{
+ if (detach) {
+ pid_t pid;
+
+ /* Fork and exit from the parent. */
+ pid = fork();
+ if (pid < 0) {
+ fatal(errno, "could not fork");
+ } else if (pid) {
+ fatal_signal_fork();
+ make_pidfile(pid);
+ exit(0);
+ }
+
+ if (pidfile) {
+ fatal_signal_add_file_to_unlink(pidfile);
+ }
+ setsid();
+ chdir("/");
+ } else {
+ if (pidfile) {
+ fatal_signal_add_file_to_unlink(pidfile);
+ }
+ make_pidfile(getpid());
+ }
+}
+