Store PID of quota_nld

If quota_nld is run as daemon, daemon's PID will be stored into
/var/run/${PROGNAME}.pid file and it will be deleted on receiving SIGTERM
just before program termination.

PID file is used by init scripts to find and kill forked daemon.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 80 insertions, 0 deletions

diff --git a/quota_nld.c b/quota_nld.c
index 5a53b7e..1decd96 100644
--- a/quota_nld.c
+++ b/quota_nld.c
@@ -25,6 +25,7 @@
 #include <string.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <signal.h>
 
 #include <netlink/genl/genl.h>
 #include <netlink/genl/ctrl.h>
@@ -374,6 +375,84 @@ static void run(struct nl_handle *nhandle)
 	}
 }
 
+/* Build file name (absolute path) to PID file of this daemon.
+ * The returned name is allocated on heap. */
+static char *build_pid_file_name(void)
+{
+	char *pid_name = NULL;
+	if (!progname) {
+		errstr(_("Undefined program name.\n"));
+		return NULL;
+	}
+	pid_name = malloc(9 + strlen(progname) + 4 + 1);
+	if (!pid_name) {
+		errstr(_("Not enough memory to build PID file name.\n"));
+		return NULL;
+	}
+	sprintf(pid_name, "/var/run/%s.pid", progname);
+	return pid_name;
+}
+
+/* Store daemon's PID to file */
+static int store_pid(void)
+{
+	FILE *pid_file;
+	char *pid_name;
+
+	pid_name = build_pid_file_name();
+	if (!pid_name)
+		return -1;
+
+	pid_file = fopen(pid_name, "w");
+	if (!pid_file) {
+		errstr(_("Could not open PID file '%s': %s\n"),
+			pid_name, strerror(errno));
+		free(pid_name);
+		return -1;
+	}
+	if (fprintf(pid_file, "%jd\n", (intmax_t)getpid()) < 0) {
+		errstr(_("Could not write daemon's PID into '%s'.\n"),
+			pid_name);
+		fclose(pid_file);
+		free(pid_name);
+		return -1;
+	}
+	if (fclose(pid_file)) {
+		errstr(_("Could not close PID file '%s'.\n"), pid_name);
+		free(pid_name);
+		return -1;
+	}
+
+	free(pid_name);
+	return 0;
+}
+
+/* Handler for SIGTERM to remove PID file */
+static void remove_pid(int signal)
+{
+	char *pid_name;
+
+	pid_name = build_pid_file_name();
+	if (pid_name) {
+		unlink(pid_name);
+		free(pid_name);
+	}
+	exit(EXIT_SUCCESS);
+}
+
+/* Store daemon's PID into file and register its removal on SIGTERM */
+static void use_pid_file(void)
+{
+	struct sigaction term_action;
+
+	term_action.sa_handler = remove_pid;
+	term_action.sa_flags = 0;
+	if (sigaction(SIGTERM, &term_action, NULL))
+		errstr(_("Could not register PID file removal on SIGTERM.\n"));
+	if (store_pid())
+		errstr(_("Could not store my PID %jd.\n"), (intmax_t )getpid());
+}
+
 int main(int argc, char **argv)
 {
 	struct nl_handle *nhandle;
@@ -388,6 +467,7 @@ int main(int argc, char **argv)
 	if (!(flags & FL_NODAEMON)) {
 		use_syslog();
 		daemon(0, 0);
+		use_pid_file();
 	}
 	run(nhandle);
 	return 0;