On 12/05/13 13:47, Chris Boot wrote:
> 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
Hi folks,
Any comments about my revised patch? Is this likely to be taken up into
ulogd?
Cheers,
Chris
--
Chris Boot
bootc@xxxxxxxxx
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