[Ulogd PATCH] Improve pid file handling.

[Eric Leblond <eric@regit.org>]

This patch improves latest patch by splitting in two part the pid
file creation. This allows to display a message to stdout when
ulogd can not be started. Another linked improvement is that the
plugin initialization is not done if the pid file existence will
result in a ulogd exit.

Signed-off-by: Eric Leblond <eric@regit.org>
---
 src/ulogd.c |   66 ++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 54 insertions(+), 12 deletions(-)

diff --git a/src/ulogd.c b/src/ulogd.c
index 4309201..c1aba77 100644
--- a/src/ulogd.c
+++ b/src/ulogd.c
@@ -82,6 +82,7 @@ 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 int ulogd_pidfile_fd = -1;
 static FILE syslog_dummy;
 
 static int info_mode = 0;
@@ -1017,7 +1018,7 @@ static int parse_conffile(const char *section, struct config_keyset *ce)
  * the GPL2+ license with the following copyright statement:
  * Copyright (C) 1996 Thomas Koenig
  */
-static int lock_fd(int fd)
+static int lock_fd(int fd, int wait)
 {
 	struct flock lock;
 
@@ -1026,7 +1027,10 @@ static int lock_fd(int fd)
 	lock.l_start = 0;
 	lock.l_len = 0;
 
-	return fcntl(fd, F_SETLK, &lock);
+	if (wait)
+		return fcntl(fd, F_SETLKW, &lock);
+	else
+		return fcntl(fd, F_SETLK, &lock);
 }
 
 /*
@@ -1036,12 +1040,15 @@ static int lock_fd(int fd)
  * under the GPL2+ license with the following copyright statement:
  * Copyright (C) 1996 Thomas Koenig
  */
-static int write_pidfile()
+static int create_pidfile()
 {
 	int fd;
 	FILE *fp;
 	pid_t pid = -1;
 
+	if (!ulogd_pidfile)
+		return 0;
+
 	fd = open(ulogd_pidfile, O_RDWR | O_CREAT | O_EXCL, 0644);
 	if (fd < 0) {
 		if (errno != EEXIST) {
@@ -1061,13 +1068,14 @@ static int write_pidfile()
 		if (fp == NULL) {
 			ulogd_log(ULOGD_ERROR, "cannot fdopen %s: %d\n",
 					ulogd_pidfile, errno);
+			close(fd);
 			return -1;
 		}
 
 		if ((fscanf(fp, "%d", &pid) != 1) || (pid == getpid())
-				|| (lock_fd(fd) == 0)) {
+				|| (lock_fd(fd, 0) == 0)) {
 			ulogd_log(ULOGD_NOTICE,
-				"removing stale pidfile for pid %d\n", pid);
+				  "removing stale pidfile for pid %d\n", pid);
 
 			if (unlink(ulogd_pidfile) < 0) {
 				ulogd_log(ULOGD_ERROR, "cannot unlink %s: %d\n",
@@ -1078,9 +1086,12 @@ static int write_pidfile()
 			ulogd_log(ULOGD_FATAL,
 				"another ulogd already running with pid %d\n",
 				pid);
+			fclose(fp);
+			close(fd);
 			return -1;
 		}
 
+		close(fd);
 		fclose(fp);
 		unlink(ulogd_pidfile);
 
@@ -1094,16 +1105,42 @@ static int write_pidfile()
 		}
 	}
 
-	if (lock_fd(fd) < 0) {
-		ulogd_log(ULOGD_ERROR, "cannot lock %s: %d\n", ulogd_pidfile,
-				errno);
+	if (lock_fd(fd, 0) < 0) {
+		ulogd_log(ULOGD_ERROR, "cannot lock %s: %s\n", ulogd_pidfile,
+				strerror(errno));
+		close(fd);
+		return -1;
+	}
+	ulogd_pidfile_fd = fd;
+	return 0;
+}
+
+static int write_pidfile(int daemonize)
+{
+	FILE *fp;
+	if (!ulogd_pidfile)
+		return 0;
+
+	if (ulogd_pidfile_fd == -1) {
+		ulogd_log(ULOGD_ERROR, "unset pid file fd\n");
 		return -1;
 	}
 
-	fp = fdopen(fd, "w");
+	if (daemonize) {
+		/* relocking as lock is not inherited */
+		if (lock_fd(ulogd_pidfile_fd, 1) < 0) {
+			ulogd_log(ULOGD_ERROR, "cannot lock %s: %d\n", ulogd_pidfile,
+					errno);
+			close(ulogd_pidfile_fd);
+			return -1;
+		}
+	}
+
+	fp = fdopen(ulogd_pidfile_fd, "w");
 	if (fp == NULL) {
 		ulogd_log(ULOGD_ERROR, "cannot fdopen %s: %d\n", ulogd_pidfile,
 				errno);
+		close(ulogd_pidfile_fd);
 		return -1;
 	}
 
@@ -1118,7 +1155,7 @@ static int write_pidfile()
 	 * 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);
+	fcntl(ulogd_pidfile_fd, F_SETFD, FD_CLOEXEC);
 
 	created_pidfile = 1;
 
@@ -1350,6 +1387,11 @@ int main(int argc, char* argv[])
 		loglevel_ce.u.value = loglevel;
 		loglevel_ce.flag |= CONFIG_FLAG_VAL_PROTECTED;
 
+	if (ulogd_pidfile) {
+		if (create_pidfile() < 0)
+			warn_and_exit(0);
+	}
+
 	if (daemonize && verbose) {
 		verbose = 0;
 		ulogd_log(ULOGD_ERROR,
@@ -1421,8 +1463,8 @@ int main(int argc, char* argv[])
 	}
 
 	if (ulogd_pidfile) {
-		if (write_pidfile() < 0)
-			warn_and_exit(daemonize);
+		if (write_pidfile(daemonize) < 0)
+			warn_and_exit(0);
 	}
 
 	signal(SIGTERM, &sigterm_handler);
-- 
1.7.10.4