diff options
Diffstat (limited to 'lib/daemon.c')
| -rw-r--r-- | lib/daemon.c | 294 |
1 files changed, 294 insertions, 0 deletions
diff --git a/lib/daemon.c b/lib/daemon.c new file mode 100644 index 000000000..8b1762388 --- /dev/null +++ b/lib/daemon.c @@ -0,0 +1,294 @@ +/* + * Copyright (c) 2008, 2009 Nicira Networks. + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#include <config.h> +#include "daemon.h" +#include <errno.h> +#include <fcntl.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include "fatal-signal.h" +#include "dirs.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; + +/* Create pidfile even if one already exists and is locked? */ +static bool force; + +/* 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) +{ + return (!name ? xasprintf("%s/%s.pid", ovs_rundir, program_name) + : *name == '/' ? xstrdup(name) + : xasprintf("%s/%s", ovs_rundir, name)); +} + +/* 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' is null, then program_name followed by ".pid" is used. */ +void +set_pidfile(const char *name) +{ + 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; +} + +/* 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) +{ + force = 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; +} + +/* 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); + } + } + 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 (!force) { + 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); + } + } +} + +/* 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. */ +void +daemonize(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); + + case 0: + /* Child process. */ + close(fds[0]); + make_pidfile(); + write(fds[1], &c, 1); + close(fds[1]); + setsid(); + chdir("/"); + break; + + case -1: + /* Error. */ + ovs_fatal(errno, "could not fork"); + break; + } + } else { + make_pidfile(); + } +} + +void +daemon_usage(void) +{ + printf( + "\nDaemon options:\n" + " -D, --detach run in background as daemon\n" + " -P, --pidfile[=FILE] create pidfile (default: %s/%s.pid)\n" + " -f, --force with -P, 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; +} |