The deamon currently does not have the ability to write a PID file to track its
process ID. This is very useful to an init script and to ensure there is only
one running instance. This patch implements this functionality.
Signed-off-by: Chris Boot <bootc@xxxxxxxxx>
---
Changes since v1:
- Added documentation about the option to ulogd.8.
- Move check for NULL ulogd_pidfile into main(), so it's more obvious that the
code does nothing unless the --pidfile option is present.
- Check for stale PID files and overwrite if that's the case, instead of
bailing out.
- Lock the pidfile with fcntl(); this is a good check to guard against running
multiple instances with the same pidfile. (from atd)
- Only unlink the pidfile at exit if we have created it. This prevents us
removing another running ulogd process's pidfile if we exit because there is
another running instance.
src/ulogd.c | 147 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
ulogd.8 | 3 ++
2 files changed, 149 insertions(+), 1 deletion(-)
diff --git a/src/ulogd.c b/src/ulogd.c
index 8a144e3..b835220 100644
--- a/src/ulogd.c
+++ b/src/ulogd.c
@@ -4,6 +4,7 @@
*
* (C) 2000-2005 by Harald Welte <laforge@xxxxxxxxxxxx>
* (C) 2013 by Eric Leblond <eric@xxxxxxxxx>
+ * (C) 2013 Chris Boot <bootc@xxxxxxxxx>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
@@ -55,12 +56,14 @@
#include <signal.h>
#include <dlfcn.h>
#include <sys/types.h>
+#include <fcntl.h>
#include <dirent.h>
#include <getopt.h>
#include <pwd.h>
#include <grp.h>
#include <syslog.h>
#include <sys/time.h>
+#include <sys/stat.h>
#include <ulogd/conffile.h>
#include <ulogd/ulogd.h>
#ifdef DEBUG
@@ -78,11 +81,13 @@
static FILE *logfile = NULL; /* logfile pointer */
static char *ulogd_logfile = NULL;
static const char *ulogd_configfile = ULOGD_CONFIGFILE;
+static const char *ulogd_pidfile = NULL;
static FILE syslog_dummy;
static int info_mode = 0;
static int verbose = 0;
+static int created_pidfile = 0;
/* linked list for all registered plugins */
static LLIST_HEAD(ulogd_plugins);
@@ -94,6 +99,7 @@ static LLIST_HEAD(ulogd_pi_stacks);
static int load_plugin(const char *file);
static int create_stack(const char *file);
static int logfile_open(const char *name);
+static void cleanup_pidfile();
static struct config_keyset ulogd_kset = {
.num_ces = 4,
@@ -457,6 +463,8 @@ void __ulogd_log(int level, char *file, int line, const char *format, ...)
static void warn_and_exit(int daemonize)
{
+ cleanup_pidfile();
+
if (!daemonize) {
if (logfile && !verbose) {
fprintf(stderr, "Fatal error, check logfile \"%s\""
@@ -1002,6 +1010,131 @@ static int parse_conffile(const char *section, struct config_keyset *ce)
return 1;
}
+/*
+ * Apply F_WRLCK to fd using fcntl().
+ *
+ * This function is copied verbatim from atd's daemon.c file, published under
+ * the GPL2+ license with the following copyright statement:
+ * Copyright (C) 1996 Thomas Koenig
+ */
+static int lock_fd(int fd)
+{
+ struct flock lock;
+
+ lock.l_type = F_WRLCK;
+ lock.l_whence = SEEK_SET;
+ lock.l_start = 0;
+ lock.l_len = 0;
+
+ return fcntl(fd, F_SETLK, &lock);
+}
+
+/*
+ * Manage ulogd's pidfile.
+ *
+ * This function is based on atd's daemon.c:daemon_setup() function, published
+ * under the GPL2+ license with the following copyright statement:
+ * Copyright (C) 1996 Thomas Koenig
+ */
+static int write_pidfile()
+{
+ int fd;
+ FILE *fp;
+ pid_t pid = -1;
+
+ fd = open(ulogd_pidfile, O_RDWR | O_CREAT | O_EXCL, 0644);
+ if (fd < 0) {
+ if (errno != EEXIST) {
+ ulogd_log(ULOGD_ERROR, "cannot open %s: %d\n",
+ ulogd_pidfile, errno);
+ return -1;
+ }
+
+ fd = open(ulogd_pidfile, O_RDWR);
+ if (fd < 0) {
+ ulogd_log(ULOGD_ERROR, "cannot open %s: %d\n",
+ ulogd_pidfile, errno);
+ return -1;
+ }
+
+ fp = fdopen(fd, "rw");
+ if (fp == NULL) {
+ ulogd_log(ULOGD_ERROR, "cannot fdopen %s: %d\n",
+ ulogd_pidfile, errno);
+ return -1;
+ }
+
+ if ((fscanf(fp, "%d", &pid) != 1) || (pid == getpid())
+ || (lock_fd(fd) == 0)) {
+ ulogd_log(ULOGD_NOTICE,
+ "removing stale pidfile for pid %d\n", pid);
+
+ if (unlink(ulogd_pidfile) < 0) {
+ ulogd_log(ULOGD_ERROR, "cannot unlink %s: %d\n",
+ ulogd_pidfile, errno);
+ return -1;
+ }
+ } else {
+ ulogd_log(ULOGD_FATAL,
+ "another ulogd already running with pid %d\n",
+ pid);
+ return -1;
+ }
+
+ fclose(fp);
+ unlink(ulogd_pidfile);
+
+ fd = open(ulogd_pidfile, O_RDWR | O_CREAT | O_EXCL, 0644);
+
+ if (fd < 0) {
+ ulogd_log(ULOGD_ERROR,
+ "cannot open %s (2nd time round): %d\n",
+ ulogd_pidfile, errno);
+ return -1;
+ }
+ }
+
+ if (lock_fd(fd) < 0) {
+ ulogd_log(ULOGD_ERROR, "cannot lock %s: %d\n", ulogd_pidfile,
+ errno);
+ return -1;
+ }
+
+ fp = fdopen(fd, "w");
+ if (fp == NULL) {
+ ulogd_log(ULOGD_ERROR, "cannot fdopen %s: %d\n", ulogd_pidfile,
+ errno);
+ return -1;
+ }
+
+ fprintf(fp, "%d\n", getpid());
+ fflush(fp);
+
+ if (ftruncate(fileno(fp), ftell(fp)) < 0)
+ ulogd_log(ULOGD_NOTICE, "cannot ftruncate %s: %d\n",
+ ulogd_pidfile, errno);
+
+ /*
+ * We do NOT close fd, since we want to keep the lock. However, we don't
+ * want to keep the file descriptor in case of an exec().
+ */
+ fcntl(fd, F_SETFD, FD_CLOEXEC);
+
+ created_pidfile = 1;
+
+ return 0;
+}
+
+static void cleanup_pidfile()
+{
+ if (!ulogd_pidfile || !created_pidfile)
+ return;
+
+ if (unlink(ulogd_pidfile) != 0)
+ ulogd_log(ULOGD_ERROR, "PID file %s could not be deleted: %d\n",
+ ulogd_pidfile, errno);
+}
+
static void deliver_signal_pluginstances(int signal)
{
struct ulogd_pluginstance_stack *stack;
@@ -1080,6 +1213,8 @@ static void sigterm_handler(int signal)
config_stop();
+ cleanup_pidfile();
+
exit(0);
}
@@ -1121,6 +1256,7 @@ static void print_usage(void)
printf("\t-v --verbose\tOutput info on standard output\n");
printf("\t-l --loglevel\tSet log level\n");
printf("\t-c --configfile\tUse alternative Configfile\n");
+ printf("\t-p --pidfile\tRecord ulogd PID in file\n");
printf("\t-u --uid\tChange UID/GID\n");
printf("\t-i --info\tDisplay infos about plugin\n");
}
@@ -1134,6 +1270,7 @@ static struct option opts[] = {
{ "info", 1, NULL, 'i' },
{ "verbose", 0, NULL, 'v' },
{ "loglevel", 1, NULL, 'l' },
+ { "pidfile", 1, NULL, 'p' },
{NULL, 0, NULL, 0}
};
@@ -1150,7 +1287,7 @@ int main(int argc, char* argv[])
ulogd_logfile = strdup(ULOGD_LOGFILE_DEFAULT);
- while ((argch = getopt_long(argc, argv, "c:dvl:h::Vu:i:", opts, NULL)) != -1) {
+ while ((argch = getopt_long(argc, argv, "c:p:dvl:h::Vu:i:", opts, NULL)) != -1) {
switch (argch) {
default:
case '?':
@@ -1179,6 +1316,9 @@ int main(int argc, char* argv[])
case 'c':
ulogd_configfile = optarg;
break;
+ case 'p':
+ ulogd_pidfile = optarg;
+ break;
case 'u':
change_uid = 1;
user = strdup(optarg);
@@ -1280,6 +1420,11 @@ int main(int argc, char* argv[])
setsid();
}
+ if (ulogd_pidfile) {
+ if (write_pidfile() < 0)
+ warn_and_exit(daemonize);
+ }
+
signal(SIGTERM, &sigterm_handler);
signal(SIGINT, &sigterm_handler);
signal(SIGHUP, &signal_handler);
diff --git a/ulogd.8 b/ulogd.8
index 9cbad7c..9d16aeb 100644
--- a/ulogd.8
+++ b/ulogd.8
@@ -57,6 +57,9 @@ change UID/GID
.TP
.B -i <pluginpath>, --info <pluginpath>
display infos about plugin
+.TP
+.B -p <filename>, --pidfile <filename>
+record the ulogd process ID to the given file name
.SH FILES
.I /etc/ulogd.conf
.br
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
