Create PID file at startup, in daemon mode

Code imported from Project Hail

5 files changed, 146 insertions, 3 deletions

diff --git a/Makefile.am b/Makefile.am
index d0cec2d..6822181 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -10,7 +10,7 @@ man_MANS	 = rngd.8 rngtest.1
 noinst_LIBRARIES = librngd.a
 
 rngd_SOURCES	= rngd.h rngd.c	rngd_entsource.h rngd_entsource.c	\
-		  rngd_linux.h rngd_linux.c
+		  rngd_linux.h rngd_linux.c util.c
 rngd_LDADD	= librngd.a
 
 rngtest_SOURCES	= exits.h stats.h stats.c rngtest.c
diff --git a/rngd.8.in b/rngd.8.in
index bbd9e3c..2fd357f 100644
--- a/rngd.8.in
+++ b/rngd.8.in
@@ -10,6 +10,7 @@ rngd \- Check and feed random data from hardware device to kernel random device
 [\fB\-b\fR, \fB\-\-background\fR]
 [\fB\-f\fR, \fB\-\-foreground\fR]
 [\fB\-o\fR, \fB\-\-random-device=\fIfile\fR]
+[\fB\-p\fR, \fB\-\-pid-file=\fIfile\fR]
 [\fB\-r\fR, \fB\-\-rng-device=\fIfile\fR]
 [\fB\-s\fR, \fB\-\-random-step=\fInnn\fR]
 [\fB\-W\fR, \fB\-\-fill-watermark=\fInnn\fR]
@@ -48,6 +49,10 @@ Become a daemon (default)
 \fB\-f\fR, \fB\-\-foreground\fR
 Do not fork and become a daemon
 .TP
+\fB\-p\fI file\fR, \fB\-\-pid-file=\fIfile\fR
+File used for recording daemon PID, and multiple exclusion
+(default: /var/run/rngd.pid)
+.TP
 \fB\-o\fI file\fR, \fB\-\-random-device=\fIfile\fR
 Kernel device used for random number output
 (default: /dev/random)
diff --git a/rngd.c b/rngd.c
index 90232f8..5875671 100644
--- a/rngd.c
+++ b/rngd.c
@@ -45,6 +45,7 @@
 #include <string.h>
 #include <argp.h>
 #include <syslog.h>
+#include <signal.h>
 
 #include "rngd.h"
 #include "fips.h"
@@ -59,6 +60,8 @@
 /* Background/daemon mode */
 int am_daemon;				/* Nonzero if we went daemon */
 
+bool server_running = true;		/* set to false, to stop daemon */
+
 /* Command line arguments and processing */
 const char *argp_program_version =
 	"rngd " VERSION "\n"
@@ -83,6 +86,9 @@ static struct argp_option options[] = {
 	{ "rng-device", 'r', "file", 0,
 	  "Kernel device used for random number input (default: /dev/hw_random)" },
 
+	{ "pid-file", 'p', "file", 0,
+	  "File used for recording daemon PID, and multiple exclusion (default: /var/run/rngd.pid)" },
+
 	{ "random-step", 's', "nnn", 0,
 	  "Number of bytes written to random-device at a time (default: 64)" },
 
@@ -103,6 +109,7 @@ static struct argp_option options[] = {
 
 static struct arguments default_arguments = {
 	.random_name	= "/dev/random",
+	.pid_file	= "/var/run/rngd.pid",
 	.poll_timeout	= 60,
 	.random_step	= 64,
 	.fill_watermark	= 2048,
@@ -136,6 +143,9 @@ static error_t parse_opt (int key, char *arg, struct argp_state *state)
 	case 'o':
 		arguments->random_name = arg;
 		break;
+	case 'p':
+		arguments->pid_file = arg;
+		break;
 	case 'r':
 		rng_default.rng_name = arg;
 		break;
@@ -227,6 +237,9 @@ static void do_loop(int random_step, double poll_timeout)
 		{
 			int rc;
 
+			if (!server_running)
+				return;
+
 			if (iter->disabled)
 				continue;	/* failed, no work */
 
@@ -260,10 +273,16 @@ static void do_loop(int random_step, double poll_timeout)
 		"No entropy sources working, exiting rngd\n");
 }
 
+static void term_signal(int signo)
+{
+	server_running = false;
+}
+
 int main(int argc, char **argv)
 {
 	int rc_rng = 0;
 	int rc_tpm = 0;
+	int pid_fd = -1;
 
 	openlog("rngd", 0, LOG_DAEMON);
 
@@ -284,7 +303,7 @@ int main(int argc, char **argv)
 		}
 		return 1;
 	}
-	
+
 	if (arguments->verbose) {
 		printf("Available entropy sources:\n");
 		if (!rc_rng)
@@ -293,7 +312,7 @@ int main(int argc, char **argv)
 			printf("\tTPM\n");
 	}
 
-	if (rc_rng 
+	if (rc_rng
 		&& (rc_tpm || !arguments->enable_tpm)) {
 		if (!arguments->quiet)
 			message(LOG_DAEMON|LOG_ERR,
@@ -313,10 +332,23 @@ int main(int argc, char **argv)
 				strerror(errno));
 			return 1;
 		}
+
+		/* require valid, locked PID file to proceed */
+		pid_fd = write_pid_file(arguments->pid_file);
+		if (pid_fd < 0)
+			return 1;
+
+		signal(SIGHUP, SIG_IGN);
+		signal(SIGPIPE, SIG_IGN);
+		signal(SIGINT, term_signal);
+		signal(SIGTERM, term_signal);
 	}
 
 	do_loop(arguments->random_step,
 		arguments->poll_timeout ? : -1.0);
 
+	if (pid_fd >= 0)
+		unlink(arguments->pid_file);
+
 	return 0;
 }
diff --git a/rngd.h b/rngd.h
index 60a9861..074bcd6 100644
--- a/rngd.h
+++ b/rngd.h
@@ -40,6 +40,7 @@ enum {
 /* Command line arguments and processing */
 struct arguments {
 	char *random_name;
+	char *pid_file;
 
 	int random_step;
 	int fill_watermark;
@@ -82,5 +83,6 @@ extern int am_daemon;			/* Nonzero if we went daemon */
 } while (0)
 
 extern void src_list_add(struct rng *ent_src);
+extern int write_pid_file(const char *pid_fn);
 #endif /* RNGD__H */
 
diff --git a/util.c b/util.c
new file mode 100644
index 0000000..bc1903a
--- /dev/null
+++ b/util.c
@@ -0,0 +1,104 @@
+
+/*
+ * Copyright 2009 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#define _GNU_SOURCE
+
+#ifndef HAVE_CONFIG_H
+#error Invalid or missing autoconf build environment
+#endif
+
+#include "rng-tools-config.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <string.h>
+#include <errno.h>
+
+#include "rngd.h"
+
+int write_pid_file(const char *pid_fn)
+{
+	char str[32], *s;
+	size_t bytes;
+	int fd;
+	struct flock lock;
+	int err;
+
+	/* build file data */
+	sprintf(str, "%u\n", (unsigned int) getpid());
+
+	/* open non-exclusively (works on NFS v2) */
+	fd = open(pid_fn, O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR);
+	if (fd < 0) {
+		err = errno;
+
+		message(LOG_DAEMON|LOG_ERR, "Cannot open PID file %s: %s",
+			 pid_fn, strerror(err));
+		return -err;
+	}
+
+	/* lock */
+	memset(&lock, 0, sizeof(lock));
+	lock.l_type = F_WRLCK;
+	lock.l_whence = SEEK_SET;
+	if (fcntl(fd, F_SETLK, &lock) != 0) {
+		err = errno;
+		if (err == EAGAIN) {
+			message(LOG_DAEMON|LOG_ERR, "PID file %s is already locked",
+				 pid_fn);
+		} else {
+			message(LOG_DAEMON|LOG_ERR, "Cannot lock PID file %s: %s",
+				 pid_fn, strerror(err));
+		}
+		close(fd);
+		return -err;
+	}
+
+	/* write file data */
+	bytes = strlen(str);
+	s = str;
+	while (bytes > 0) {
+		ssize_t rc = write(fd, s, bytes);
+		if (rc < 0) {
+			err = errno;
+			message(LOG_DAEMON|LOG_ERR, "PID number write failed: %s",
+				 strerror(err));
+			goto err_out;
+		}
+
+		bytes -= rc;
+		s += rc;
+	}
+
+	/* make sure file data is written to disk */
+	if (fsync(fd) < 0) {
+		err = errno;
+		message(LOG_DAEMON|LOG_ERR, "PID file fsync failed: %s", strerror(err));
+		goto err_out;
+	}
+
+	return fd;
+
+err_out:
+	unlink(pid_fn);
+	close(fd);
+	return -err;
+}
+