From e6499f44a49d449e41ba605a0c7476019da432b4 Mon Sep 17 00:00:00 2001
From: Art Cancro <ajc@citadel.org>
Date: Sat, 10 Sep 2016 17:20:21 -0400
Subject: [PATCH] Simple concurrency lock to prevent multiple citservers
 running at the same time

---
 citadel/citserver.c   | 14 ++++++++------
 citadel/citserver.h   |  2 +-
 citadel/database.c    | 13 ++++---------
 citadel/server_main.c | 44 +++++++++++++++++++++++++++++++++++++++++--
 4 files changed, 55 insertions(+), 18 deletions(-)

diff --git a/citadel/citserver.c b/citadel/citserver.c
index 9f41f35f5..f389ac9f0 100644
--- a/citadel/citserver.c
+++ b/citadel/citserver.c
@@ -185,9 +185,9 @@ void master_startup(void) {
 
 
 /*
- * Cleanup routine to be called when the server is shutting down.
+ * Cleanup routine to be called when the server is shutting down.  Returns the needed exit code.
  */
-void master_cleanup(int exitcode) {
+int master_cleanup(int exitcode) {
 	struct CleanupFunctionHook *fcn;
 	static int already_cleaning_up = 0;
 
@@ -225,11 +225,13 @@ void master_cleanup(int exitcode) {
 	syslog(LOG_NOTICE, "citserver: Exiting with status %d\n", exitcode);
 	fflush(stdout); fflush(stderr);
 	
-	if (restart_server != 0)
-		exit(1);
-	if ((running_as_daemon != 0) && ((exitcode == 0) ))
+	if (restart_server != 0) {
+		exitcode = 1;
+	}
+	else if ((running_as_daemon != 0) && ((exitcode == 0) )) {
 		exitcode = CTDLEXIT_SHUTDOWN;
-	exit(exitcode);
+	}
+	return(exitcode);
 }
 
 
diff --git a/citadel/citserver.h b/citadel/citserver.h
index c02492512..61f1964b7 100644
--- a/citadel/citserver.h
+++ b/citadel/citserver.h
@@ -36,7 +36,7 @@ void cit_backtrace(void);
 void cit_oneline_backtrace(void);
 void cit_panic_backtrace(int SigNum);
 void master_startup (void);
-void master_cleanup (int exitcode);
+int master_cleanup (int exitcode);
 void set_wtmpsupp (char *newtext);
 void set_wtmpsupp_to_current_room(void);
 void do_command_loop(void);
diff --git a/citadel/database.c b/citadel/database.c
index e7e57a643..dbfac8dd5 100644
--- a/citadel/database.c
+++ b/citadel/database.c
@@ -34,17 +34,15 @@
 #ifdef HAVE_DB_H
 #include <db.h>
 #elif defined(HAVE_DB4_DB_H)
-#include <db4/db.h>
+#include <db5/db.h>
 #else
-#error Neither <db.h> nor <db4/db.h> was found by configure. Install db4-devel.
+#error Neither <db.h> nor <db5/db.h> was found by configure. Install db5-devel.
 #endif
 
-
-#if DB_VERSION_MAJOR < 4 || DB_VERSION_MINOR < 1
-#error Citadel requires Berkeley DB v4.1 or newer.  Please upgrade.
+#if DB_VERSION_MAJOR < 5
+#error Citadel requires Berkeley DB v5.0 or newer.  Please upgrade.
 #endif
 
-
 #include <libcitadel.h>
 
 #include "ctdl_module.h"
@@ -52,7 +50,6 @@
 #include "citserver.h"
 #include "config.h"
 
-
 static DB *dbp[MAXCDB];		/* One DB handle for each Citadel database */
 static DB_ENV *dbenv;		/* The DB environment (global) */
 
@@ -281,9 +278,7 @@ void open_databases(void)
 	dbenv->set_paniccall(dbenv, dbpanic);
 	dbenv->set_errcall(dbenv, cdb_verbose_err);
 	dbenv->set_errpfx(dbenv, "ctdl");
-#if (DB_VERSION_MAJOR > 4) || ( (DB_VERSION_MAJOR == 4) && (DB_VERSION_MINOR >= 3) )
 	dbenv->set_msgcall(dbenv, cdb_verbose_log);
-#endif
 	dbenv->set_verbose(dbenv, DB_VERB_DEADLOCK, 1);
 	dbenv->set_verbose(dbenv, DB_VERB_RECOVERY, 1);
 
diff --git a/citadel/server_main.c b/citadel/server_main.c
index 45312588e..061273a63 100644
--- a/citadel/server_main.c
+++ b/citadel/server_main.c
@@ -14,6 +14,7 @@
 #include <stdio.h>
 #include <sys/types.h>
 #include <grp.h>
+#include <sys/file.h>
 #include <libcitadel.h>
 
 #include "citserver.h"
@@ -34,6 +35,42 @@ const char *CitadelServiceTCP="citadel-TCP";
 
 void go_threading(void);
 
+
+
+/*
+ * Create or remove a lock file, so we only have one Citadel Server running at a time.
+ */
+void ctdl_lockfile(int yo) {
+	static char lockfilename[SIZ];
+	static FILE *fp;
+
+
+	if (yo) {
+		syslog(LOG_DEBUG, "Creating lockfile");
+		snprintf(lockfilename, sizeof lockfilename, "%s/citadel.lock", ctdl_run_dir);
+		fp = fopen(lockfilename, "w");
+		if (!fp) {
+			syslog(LOG_ERR, "Cannot open or create %s", lockfilename);
+			exit(CTDLEXIT_DB);
+		}
+		if (flock(fileno(fp), (LOCK_EX|LOCK_NB)) != 0) {
+			syslog(LOG_ERR, "Cannot lock %s , is another citserver running?", lockfilename);
+			exit(CTDLEXIT_DB);
+		}
+		return;
+	}
+
+	syslog(LOG_DEBUG, "Removing lockfile");
+	unlink(lockfilename);
+	flock(fileno(fp), LOCK_UN);
+	fclose(fp);
+}
+
+
+
+
+
+
 /*
  * Here's where it all begins.
  */
@@ -232,6 +269,8 @@ int main(int argc, char **argv)
 
 #endif
 
+	ctdl_lockfile(1);
+
 	/* Initialize... */
 	init_sysdep();
 
@@ -362,6 +401,7 @@ int main(int argc, char **argv)
 
 	go_threading();
 	
-	master_cleanup(exit_signal);
-	return(0);
+	int exit_code = master_cleanup(exit_signal);
+	ctdl_lockfile(0);
+	return(exit_code);
 }
-- 
2.30.2