daemon: Write own daemon routine

RPC will start page-server daemon and needs to get the
controll back to report back to caller, but the glibc's
daemon() does exit() in parent context preventing it.

Thus -- introduce own daemonizing routine.

Strictly speaking, this is not pure daemon() clone, as the
parent process has to exit himself. But this is OK for now.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/util.h

@@ -271,6 +271,7 @@ extern void shfree_last(void *ptr);
 extern int run_scripts(char *action);
 
 extern int cr_system(int in, int out, int err, char *cmd, char *const argv[]);
+extern int cr_daemon(int nochdir, int noclose);
 extern int is_root_user(void);
 
 static inline bool dir_dots(struct dirent *de)

util.c

@@ -572,6 +572,35 @@ out:
 	return ret;
 }
 
+int cr_daemon(int nochdir, int noclose)
+{
+	int pid;
+
+	pid = fork();
+	if (pid < 0) {
+		pr_perror("Can't fork");
+		return -1;
+	}
+
+	if (pid > 0)
+		return pid;
+
+	setsid();
+	if (!nochdir)
+		chdir("/");
+	if (!noclose) {
+		int fd;
+
+		fd = open("/dev/null", O_RDWR);
+		dup2(fd, 0);
+		dup2(fd, 1);
+		dup2(fd, 2);
+		close(fd);
+	}
+
+	return 0;
+}
+
 int is_root_user()
 {
 	if (geteuid() != 0) {