From 9668922f8f15f3a7331465a55f2cafca61f31db1 Mon Sep 17 00:00:00 2001
From: Sergey Popov <admin@pinkbyte.ru>
Date: Tue, 3 Jan 2012 03:48:26 +0400
Subject: [PATCH] Revert "remove unneeded fork(for now)" This reverts commit
 955aeb64b7b504a4d1b652274affcfacf3d581aa. Implement pid file management and
 locking. Only single instance of daemon is allowed

---
 yasnd.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/yasnd.c b/yasnd.c
index 65035d0..64b6418 100644
--- a/yasnd.c
+++ b/yasnd.c
@@ -8,6 +8,7 @@
 #include "yasnd.h"
 
 cfg_t *cfg; // pointer to configuration structure
+char pidfile[]="/var/run/yasnd.pid"; // pidfile path
 host_decl* hosts=NULL; // structure with hosts' definitions
 int hosts_count=0; // count of hosts
 int debug_flag=0;
@@ -94,6 +95,28 @@ int cb_validate_host(cfg_t *cfg, cfg_opt_t *opt)
 	return 0; // success
 }
 
+void pidfile_init()
+{
+	int pidfile_d=open(pidfile,O_RDWR|O_CREAT,0640);
+	/* Can not open/create pidfile? */
+	if (pidfile_d<0)
+	{
+		log_event("Error: can not open/create pid file");
+		exit(EXIT_FAILURE);
+	}
+	/* Can not lock pidfile? */
+	if (lockf(pidfile_d,F_TLOCK,0)<0)
+	{
+		log_event("Error: can not lock pid file, maybe another yasnd instance still running?");
+		exit(EXIT_FAILURE);
+	}
+	/* First daemon instance continues */
+	char pidstr[20];
+	sprintf(pidstr,"%d\n",getpid());
+	/* Record pid to pidfile and hold it */
+	write(pidfile_d,pidstr,strlen(pidstr));
+}
+
 void init()
 {
 	static cfg_opt_t host_opts[] = {
@@ -311,6 +334,8 @@ void signal_handler(int signum)
 		// free hosts structures memory
 		if (hosts!=NULL)
 			free(hosts);
+		// remove pid file
+		remove(pidfile);
 	}
 
 	if (signum==SIGHUP)
@@ -366,12 +391,29 @@ int main(int argc, char *argv[])
 	/* Our process ID and Session ID */
 	pid_t pid, sid;
 
+	/* Fork off the parent process */
+	pid = fork();
+	if (pid < 0) {
+		exit(EXIT_FAILURE);
+	}
+	/* If we got a good PID, then we can exit the parent process. */
+	if (pid > 0) {
+		exit(EXIT_SUCCESS);
+	}
+
 	/* Change the file mode mask */
 	umask(0);
 
 	/* Open any logs here */
 	openlog("yasnd", LOG_PID|LOG_CONS, LOG_USER);
 
+	/* Create a new SID for the child process */
+	sid = setsid();
+	if (sid < 0) {
+		/* Log the failure */
+		exit(EXIT_FAILURE);
+	}
+
 	/* Change the current working directory */
 	if ((chdir("/")) < 0) {
 		/* Log the failure */
@@ -383,6 +425,9 @@ int main(int argc, char *argv[])
 	close(STDOUT_FILENO);
 	close(STDERR_FILENO);
 
+	// create pid file and write current process pid
+	pidfile_init();
+
 	// initialize IPC queue and create process
 	// that will watch for new messages in it
 	ipc_init();