Description: Implement PID file writing

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.

Author: Chris Boot <debian@bootc.net>

Forwarded: http://git.netfilter.org/ulogd2/commit/?id=e04f1ce916965464318f882376eef04a8b6759f2

Reviewed-by: Eric Leblond <eric@regit.org>

Last-Update: 2013-05-21

--- a/src/ulogd.c

+++ b/src/ulogd.c

@@ -4,6 +4,7 @@

  *

  * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>

  * (C) 2013 by Eric Leblond <eric@regit.org>

+ * (C) 2013 Chris Boot <bootc@bootc.net>

  *

  *  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 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 @@

 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 @@

 	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 @@

 	config_stop();

+	cleanup_pidfile();

+

 	exit(0);

 }

@@ -1121,6 +1256,7 @@

 	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 @@

 	{ "info", 1, NULL, 'i' },

 	{ "verbose", 0, NULL, 'v' },

 	{ "loglevel", 1, NULL, 'l' },

+	{ "pidfile", 1, NULL, 'p' },

 	{NULL, 0, NULL, 0}

 };

@@ -1150,7 +1287,7 @@

 	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 @@

 		case 'c':

 			ulogd_configfile = optarg;

 			break;

+		case 'p':

+			ulogd_pidfile = optarg;

+			break;

 		case 'u':

 			change_uid = 1;

 			user = strdup(optarg);

@@ -1280,6 +1420,11 @@

 		setsid();

 	}

+	if (ulogd_pidfile) {

+		if (write_pidfile() < 0)

+			warn_and_exit(daemonize);

+	}

+

 	signal(SIGTERM, &sigterm_handler);

 	signal(SIGINT, &sigterm_handler);

 	signal(SIGHUP, &signal_handler);

--- a/ulogd.8

+++ b/ulogd.8

@@ -57,6 +57,9 @@

 .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