/*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2014 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
-
#include <config.h>
#include "daemon.h"
+#include "daemon-private.h"
#include <errno.h>
#include <fcntl.h>
-#include <stdlib.h>
-#include <string.h>
#include <unistd.h>
-#include "fatal-signal.h"
-#include "dirs.h"
-#include "lockfile.h"
-#include "timeval.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;
+VLOG_DEFINE_THIS_MODULE(daemon);
-/* Create pidfile even if one already exists and is locked? */
-static bool overwrite_pidfile;
+/* For each of the standard file descriptors, whether to replace it by
+ * /dev/null (if false) or keep it for the daemon to use (if true). */
+static bool save_fds[3];
-/* Should we chdir to "/". */
-static bool chdir_ = true;
+/* Will daemonize() really detach? */
+bool
+get_detach(void)
+{
+ return detach;
+}
-/* Returns the file name that would be used for a pidfile if 'name' were
- * provided to set_pidfile(). The caller must free the returned string. */
-char *
-make_pidfile_name(const char *name)
+/* If configured with set_pidfile() or set_detach(), creates the pid file and
+ * detaches from the foreground session. */
+void
+daemonize(void)
{
- return (!name ? xasprintf("%s/%s.pid", ovs_rundir, program_name)
- : *name == '/' ? xstrdup(name)
- : xasprintf("%s/%s", ovs_rundir, name));
+ daemonize_start();
+ daemonize_complete();
}
/* 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.
+ * If 'name' begins with '/' (or contains ':' in windows), then it is treated
+ * as an absolute path. Otherwise, it is taken relative to RUNDIR,
+ * which is $(prefix)/var/run by default.
*
* If 'name' is null, then program_name followed by ".pid" is used. */
void
set_pidfile(const char *name)
{
+ assert_single_threaded();
free(pidfile);
pidfile = make_pidfile_name(name);
}
-/* Returns an absolute path to the configured pidfile, or a null pointer if no
- * pidfile is configured. The caller must not modify or free the returned
- * string. */
-const char *
-get_pidfile(void)
-{
- return pidfile;
-}
-
-/* Sets that we do not chdir to "/". */
+/* A daemon doesn't normally have any use for the file descriptors for stdin,
+ * stdout, and stderr after it detaches. To keep these file descriptors from
+ * e.g. holding an SSH session open, by default detaching replaces each of
+ * these file descriptors by /dev/null. But a few daemons expect the user to
+ * redirect stdout or stderr to a file, in which case it is desirable to keep
+ * these file descriptors. This function, therefore, disables replacing 'fd'
+ * by /dev/null when the daemon detaches. */
void
-set_no_chdir(void)
+daemon_save_fd(int fd)
{
- chdir_ = false;
+ ovs_assert(fd == STDIN_FILENO ||
+ fd == STDOUT_FILENO ||
+ fd == STDERR_FILENO);
+ save_fds[fd] = true;
}
-/* Will we chdir to "/" as part of daemonizing? */
-bool
-is_chdir_enabled(void)
+/* Returns a readable and writable fd for /dev/null, if successful, otherwise
+ * a negative errno value. The caller must not close the returned fd (because
+ * the same fd will be handed out to subsequent callers). */
+static int
+get_null_fd(void)
{
- return chdir_;
-}
-
-/* Normally, die_if_already_running() will terminate the program with a message
- * if a locked pidfile already exists. If this function is called,
- * die_if_already_running() will merely log a warning. */
-void
-ignore_existing_pidfile(void)
-{
- overwrite_pidfile = true;
-}
-
-/* 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;
-}
-
-/* Will daemonize() really detach? */
-bool
-get_detach(void)
-{
- return detach;
-}
-
-/* If a pidfile has been configured and that pidfile already exists and is
- * locked by a running process, returns the pid of the running process.
- * Otherwise, returns 0. */
-static pid_t
-already_running(void)
-{
- pid_t pid = 0;
- if (pidfile) {
- int fd = open(pidfile, O_RDWR);
- if (fd >= 0) {
- struct flock lck;
- lck.l_type = F_WRLCK;
- lck.l_whence = SEEK_SET;
- lck.l_start = 0;
- lck.l_len = 0;
- if (fcntl(fd, F_GETLK, &lck) != -1 && lck.l_type != F_UNLCK) {
- pid = lck.l_pid;
- }
- close(fd);
+ static int null_fd;
+#ifndef _WIN32
+ char *device = "/dev/null";
+#else
+ char *device = "nul";
+#endif
+
+ if (!null_fd) {
+ null_fd = open(device, O_RDWR);
+ if (null_fd < 0) {
+ int error = errno;
+ VLOG_ERR("could not open %s: %s", device, ovs_strerror(error));
+ null_fd = -error;
}
}
- return pid;
-}
-/* If a locked pidfile exists, issue a warning message and, unless
- * ignore_existing_pidfile() has been called, terminate the program. */
-void
-die_if_already_running(void)
-{
- pid_t pid = already_running();
- if (pid) {
- if (!overwrite_pidfile) {
- ovs_fatal(0, "%s: already running as pid %ld",
- get_pidfile(), (long int) pid);
- } else {
- VLOG_WARN("%s: %s already running as pid %ld",
- get_pidfile(), program_name, (long int) pid);
- }
- }
+ return null_fd;
}
-/* If a pidfile has been configured, creates it and stores the running process'
- * pid init. Ensures that the pidfile will be deleted when the process
- * exits. */
-static void
-make_pidfile(void)
-{
- if (pidfile) {
- /* Create pidfile via temporary file, so that observers never see an
- * empty pidfile or an unlocked pidfile. */
- long int pid = getpid();
- char *tmpfile;
- int fd;
-
- tmpfile = xasprintf("%s.tmp%ld", pidfile, pid);
- fatal_signal_add_file_to_unlink(tmpfile);
- fd = open(tmpfile, O_CREAT | O_WRONLY | O_TRUNC, 0666);
- if (fd >= 0) {
- struct flock lck;
- lck.l_type = F_WRLCK;
- lck.l_whence = SEEK_SET;
- lck.l_start = 0;
- lck.l_len = 0;
- if (fcntl(fd, F_SETLK, &lck) != -1) {
- char *text = xasprintf("%ld\n", pid);
- if (write(fd, text, strlen(text)) == strlen(text)) {
- fatal_signal_add_file_to_unlink(pidfile);
- if (rename(tmpfile, pidfile) < 0) {
- VLOG_ERR("failed to rename \"%s\" to \"%s\": %s",
- tmpfile, pidfile, strerror(errno));
- fatal_signal_remove_file_to_unlink(pidfile);
- close(fd);
- } else {
- /* Keep 'fd' open to retain the lock. */
- }
- free(text);
- } else {
- VLOG_ERR("%s: write failed: %s", tmpfile, strerror(errno));
- close(fd);
- }
- } else {
- VLOG_ERR("%s: fcntl failed: %s", tmpfile, strerror(errno));
- close(fd);
- }
- } else {
- VLOG_ERR("%s: create failed: %s", tmpfile, strerror(errno));
- }
- fatal_signal_remove_file_to_unlink(tmpfile);
- free(tmpfile);
- }
- free(pidfile);
- pidfile = NULL;
-}
-
-/* If configured with set_pidfile() or set_detach(), creates the pid file and
- * detaches from the foreground session. */
+/* Close standard file descriptors (except any that the client has requested we
+ * leave open by calling daemon_save_fd()). If we're started from e.g. an SSH
+ * session, then this keeps us from holding that session open artificially. */
void
-daemonize(void)
+close_standard_fds(void)
{
- if (detach) {
- char c = 0;
- int fds[2];
- if (pipe(fds) < 0) {
- ovs_fatal(errno, "pipe failed");
- }
-
- switch (fork()) {
- default:
- /* Parent process: wait for child to create pidfile, then exit. */
- close(fds[1]);
- fatal_signal_fork();
- if (read(fds[0], &c, 1) != 1) {
- ovs_fatal(errno, "daemon child failed to signal startup");
- }
- exit(0);
+ int null_fd = get_null_fd();
+ if (null_fd >= 0) {
+ int fd;
- case 0:
- /* Child process. */
- close(fds[0]);
- make_pidfile();
- write(fds[1], &c, 1);
- close(fds[1]);
- setsid();
- if (chdir_) {
- chdir("/");
+ for (fd = 0; fd < 3; fd++) {
+ if (!save_fds[fd]) {
+ dup2(null_fd, fd);
}
- time_postfork();
- lockfile_postfork();
- break;
-
- case -1:
- /* Error. */
- ovs_fatal(errno, "could not fork");
- break;
}
- } else {
- make_pidfile();
}
-}
-
-void
-daemon_usage(void)
-{
- printf(
- "\nDaemon options:\n"
- " --detach run in background as daemon\n"
- " --no-chdir do not chdir to '/'\n"
- " --pidfile[=FILE] create pidfile (default: %s/%s.pid)\n"
- " --overwrite-pidfile with --pidfile, start even if already "
- "running\n",
- ovs_rundir, program_name);
-}
-/* Opens and reads a PID from 'pidfile'. Returns the nonnegative PID if
- * successful, otherwise a negative errno value. */
-pid_t
-read_pidfile(const char *pidfile)
-{
- char line[128];
- struct flock lck;
- FILE *file;
- int error;
-
- file = fopen(pidfile, "r");
- if (!file) {
- error = errno;
- VLOG_WARN("%s: open: %s", pidfile, strerror(error));
- goto error;
- }
-
- lck.l_type = F_WRLCK;
- lck.l_whence = SEEK_SET;
- lck.l_start = 0;
- lck.l_len = 0;
- if (fcntl(fileno(file), F_GETLK, &lck)) {
- error = errno;
- VLOG_WARN("%s: fcntl: %s", pidfile, strerror(error));
- goto error;
- }
- if (lck.l_type == F_UNLCK) {
- error = ESRCH;
- VLOG_WARN("%s: pid file is not locked", pidfile);
- goto error;
- }
-
- if (!fgets(line, sizeof line, file)) {
- if (ferror(file)) {
- error = errno;
- VLOG_WARN("%s: read: %s", pidfile, strerror(error));
- } else {
- error = ESRCH;
- VLOG_WARN("%s: read: unexpected end of file", pidfile);
- }
- goto error;
- }
-
- if (lck.l_pid != strtoul(line, NULL, 10)) {
- error = ESRCH;
- VLOG_WARN("l_pid (%ld) != %s pid (%s)",
- (long int) lck.l_pid, pidfile, line);
- goto error;
- }
-
- fclose(file);
- return lck.l_pid;
-
-error:
- if (file) {
- fclose(file);
- }
- return -error;
+ /* Disable logging to stderr to avoid wasting CPU time. */
+ vlog_set_levels(NULL, VLF_CONSOLE, VLL_OFF);
}
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