Ben Pfaff
238 lines
7.4 KiB
C
238 lines
7.4 KiB
C
/* Copyright (c) 2008 The Board of Trustees of The Leland Stanford
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* Junior University
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*
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* We are making the OpenFlow specification and associated documentation
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* (Software) available for public use and benefit with the expectation
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* that others will use, modify and enhance the Software and contribute
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* those enhancements back to the community. However, since we would
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* like to make the Software available for broadest use, with as few
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* restrictions as possible permission is hereby granted, free of
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* charge, to any person obtaining a copy of this Software to deal in
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* the Software under the copyrights without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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* The name and trademarks of copyright holder(s) may NOT be used in
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* advertising or publicity pertaining to the Software or any
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* derivatives without specific, written prior permission.
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*/
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#include <config.h>
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#include "daemon.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "fatal-signal.h"
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#include "util.h"
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#define THIS_MODULE VLM_daemon
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#include "vlog.h"
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/* Should we run in the background? */
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static bool detach;
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/* Name of pidfile (null if none). */
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static char *pidfile;
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/* Create pidfile even if one already exists and is locked? */
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static bool force;
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/* Returns the file name that would be used for a pidfile if 'name' were
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* provided to set_pidfile(). The caller must free the returned string. */
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char *
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make_pidfile_name(const char *name)
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{
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return (!name ? xasprintf("%s/%s.pid", RUNDIR, program_name)
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: *name == '/' ? xstrdup(name)
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: xasprintf("%s/%s", RUNDIR, name));
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}
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/* Sets up a following call to daemonize() to create a pidfile named 'name'.
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* If 'name' begins with '/', then it is treated as an absolute path.
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* Otherwise, it is taken relative to RUNDIR, which is $(prefix)/var/run by
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* default.
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*
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* If 'name' is null, then program_name followed by ".pid" is used. */
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void
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set_pidfile(const char *name)
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{
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free(pidfile);
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pidfile = make_pidfile_name(name);
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}
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/* Returns an absolute path to the configured pidfile, or a null pointer if no
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* pidfile is configured. The caller must not modify or free the returned
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* string. */
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const char *
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get_pidfile(void)
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{
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return pidfile;
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}
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/* Normally, die_if_already_running() will terminate the program with a message
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* if a locked pidfile already exists. If this function is called,
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* die_if_already_running() will merely log a warning. */
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void
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ignore_existing_pidfile(void)
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{
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force = true;
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}
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/* Sets up a following call to daemonize() to detach from the foreground
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* session, running this process in the background. */
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void
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set_detach(void)
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{
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detach = true;
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}
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/* If a pidfile has been configured and that pidfile already exists and is
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* locked by a running process, returns the pid of the running process.
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* Otherwise, returns 0. */
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static pid_t
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already_running(void)
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{
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pid_t pid = 0;
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if (pidfile) {
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int fd = open(pidfile, O_RDWR);
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if (fd >= 0) {
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struct flock lck;
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lck.l_type = F_WRLCK;
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lck.l_whence = SEEK_SET;
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lck.l_start = 0;
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lck.l_len = 0;
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if (fcntl(fd, F_GETLK, &lck) != -1 && lck.l_type != F_UNLCK) {
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pid = lck.l_pid;
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}
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close(fd);
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}
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}
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return pid;
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}
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/* If a locked pidfile exists, issue a warning message and, unless
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* ignore_existing_pidfile() has been called, terminate the program. */
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void
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die_if_already_running(void)
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{
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pid_t pid = already_running();
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if (pid) {
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if (!force) {
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ofp_fatal(0, "%s: already running as pid %ld",
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get_pidfile(), (long int) pid);
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} else {
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VLOG_WARN("%s: %s already running as pid %ld",
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get_pidfile(), program_name, (long int) pid);
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}
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}
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}
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/* If a pidfile has been configured, creates it and stores the running process'
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* pid init. Ensures that the pidfile will be deleted when the process
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* exits. */
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static void
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make_pidfile(void)
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{
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if (pidfile) {
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/* Create pidfile via temporary file, so that observers never see an
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* empty pidfile or an unlocked pidfile. */
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long int pid = getpid();
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char *tmpfile;
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int fd;
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tmpfile = xasprintf("%s.tmp%ld", pidfile, pid);
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fatal_signal_add_file_to_unlink(tmpfile);
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fd = open(tmpfile, O_CREAT | O_WRONLY | O_TRUNC, 0666);
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if (fd >= 0) {
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struct flock lck;
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lck.l_type = F_WRLCK;
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lck.l_whence = SEEK_SET;
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lck.l_start = 0;
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lck.l_len = 0;
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if (fcntl(fd, F_SETLK, &lck) != -1) {
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char *text = xasprintf("%ld\n", pid);
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if (write(fd, text, strlen(text)) == strlen(text)) {
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fatal_signal_add_file_to_unlink(pidfile);
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if (rename(tmpfile, pidfile) < 0) {
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VLOG_ERR("failed to rename \"%s\" to \"%s\": %s",
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tmpfile, pidfile, strerror(errno));
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fatal_signal_remove_file_to_unlink(pidfile);
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close(fd);
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} else {
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/* Keep 'fd' open to retain the lock. */
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}
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} else {
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VLOG_ERR("%s: write failed: %s", tmpfile, strerror(errno));
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close(fd);
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}
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} else {
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VLOG_ERR("%s: fcntl failed: %s", tmpfile, strerror(errno));
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close(fd);
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}
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} else {
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VLOG_ERR("%s: create failed: %s", tmpfile, strerror(errno));
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}
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fatal_signal_remove_file_to_unlink(tmpfile);
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free(tmpfile);
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}
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free(pidfile);
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pidfile = NULL;
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}
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/* If configured with set_pidfile() or set_detach(), creates the pid file and
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* detaches from the foreground session. */
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void
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daemonize(void)
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{
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if (detach) {
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char c = 0;
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int fds[2];
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if (pipe(fds) < 0) {
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ofp_fatal(errno, "pipe failed");
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}
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switch (fork()) {
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default:
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/* Parent process: wait for child to create pidfile, then exit. */
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close(fds[1]);
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fatal_signal_fork();
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read(fds[0], &c, 1);
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exit(0);
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case 0:
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/* Child process. */
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close(fds[0]);
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make_pidfile();
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write(fds[1], &c, 1);
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close(fds[1]);
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setsid();
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chdir("/");
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break;
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case -1:
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/* Error. */
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ofp_fatal(errno, "could not fork");
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break;
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}
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} else {
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make_pidfile();
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}
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}
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