From 5a834f69b723cb4aa4ca9f7a23ad9b05f17cfb8f Mon Sep 17 00:00:00 2001
From: Art Cancro <ajc@citadel.org>
Date: Wed, 20 Dec 2006 19:04:43 +0000
Subject: [PATCH] * Lock citadel.control using flock() immediately after  
 opening it.  Failure to acquire a lock means that another citserver   already
 running, which causes the server to abort.

---
 citadel/control.c     | 20 +++++++++++++++++++-
 citadel/server_main.c |  4 ++++
 citadel/sysdep.c      | 17 ++++++++++++++++-
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/citadel/control.c b/citadel/control.c
index f2268d8fa..0c9dd11b1 100644
--- a/citadel/control.c
+++ b/citadel/control.c
@@ -28,6 +28,7 @@
 #include <errno.h>
 #include <limits.h>
 #include <sys/types.h>
+#include <sys/file.h>
 #include "citadel.h"
 #include "server.h"
 #include "control.h"
@@ -48,12 +49,27 @@ struct CitControl CitControl;
 extern struct config config;
 FILE *control_fp = NULL;
 
+
+
+/*
+ * lock_control  -  acquire a lock on the control record file.
+ *                  This keeps multiple citservers from running concurrently.
+ */
+void lock_control(void)
+{
+	if (flock(fileno(control_fp), (LOCK_EX | LOCK_NB))) {
+		lprintf(CTDL_EMERG, "citserver: unable to lock %s.\n", file_citadel_control);
+		lprintf(CTDL_EMERG, "Is another citserver already running?\n");
+		exit(1);
+	}
+}
+
+
 /*
  * get_control  -  read the control record into memory.
  */
 void get_control(void)
 {
-
 	/* Zero it out.  If the control record on disk is missing or short,
 	 * the system functions with all control record fields initialized
 	 * to zero.
@@ -62,12 +78,14 @@ void get_control(void)
 	if (control_fp == NULL) {
 		control_fp = fopen(file_citadel_control, "rb+");
 		if (control_fp != NULL) {
+			lock_control();
 			fchown(fileno(control_fp), config.c_ctdluid, -1);
 		}
 	}
 	if (control_fp == NULL) {
 		control_fp = fopen(file_citadel_control, "wb+");
 		if (control_fp != NULL) {
+			lock_control();
 			fchown(fileno(control_fp), config.c_ctdluid, -1);
 			memset(&CitControl, 0, sizeof(struct CitControl));
 			fwrite(&CitControl, sizeof(struct CitControl),
diff --git a/citadel/server_main.c b/citadel/server_main.c
index ef1c9c96e..7c152d744 100644
--- a/citadel/server_main.c
+++ b/citadel/server_main.c
@@ -51,6 +51,7 @@
 #include "citserver.h"
 #include "support.h"
 #include "config.h"
+#include "control.h"
 #include "database.h"
 #include "housekeeping.h"
 #include "tools.h"
@@ -187,6 +188,9 @@ int main(int argc, char **argv)
 	config.c_ipgm_secret = rand();
 	put_config();
 
+	lprintf(CTDL_INFO, "Acquiring control record\n");
+	get_control();
+
 #ifdef HAVE_RUN_DIR
 	/* on some dists rundir gets purged on startup. so we need to recreate it. */
 
diff --git a/citadel/sysdep.c b/citadel/sysdep.c
index f4e20d72e..c992adbe6 100644
--- a/citadel/sysdep.c
+++ b/citadel/sysdep.c
@@ -757,7 +757,22 @@ void kill_session(int session_to_kill) {
  * Start running as a daemon.
  */
 void start_daemon(int unused) {
-	close(0); close(1); close(2);
+	int nullfd;
+
+	/* Close stdin/stdout/stderr and replace them with /dev/null.
+	 * We don't just call close() because we don't want these fd's
+	 * to be reused for other files.
+	 */
+	nullfd = open("/dev/null", O_RDWR);
+	if (nullfd < 0) {
+		fprintf(stderr, "/dev/null: %s\n", strerror(errno));
+		exit(2);
+	}
+	dup2(nullfd, 0);
+	dup2(nullfd, 1);
+	dup2(nullfd, 2);
+	close(nullfd);
+
 	if (fork()) exit(0);
 	setsid();
 	signal(SIGHUP,SIG_IGN);
-- 
2.39.2