libSzarp2: process daemonization - new implementation

* it has several advantages over the old libSzarp version:
  - is parametrizable.
  - does double forking.
  - doesn't use deprecated signal(2).

libSzarp2/Makefile.am

@@ -216,7 +216,8 @@ libSzarp2_la_SOURCES = \
 			$(SZ4_DIR)/filelock.cpp \
 			$(SZ4_DIR)/decode_file.cpp \
 			\
-			$(PROTOBUF)
+			$(PROTOBUF) \
+			$(SOURCE_DIR)/utils/daemonize.cc
 
 
 libSzarp2_la_LIBADD = libSzarpLuaParser.la

libSzarp2/include/daemonize.h

@@ -0,0 +1,35 @@
+/**
+ * System daemon tools for GNU/Linux.
+ *
+ * Copyright (C) 2015 Newterm
+ * Author: Tomasz Pieczerak <tph@newterm.pl>
+ *
+ * This file is a part of SZARP SCADA software.
+ *
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ *
+ */
+#ifndef __DAEMONIZE_H
+#define __DAEMONIZE_H
+
+/* daemonize() flags */
+#define DMN_SIGPIPE_IGN  0x01  /* set IGNORE action on SIGPIPE */
+#define DMN_NOREDIR_STD  0x02  /* don't redirect std descriptors to /dev/null */
+#define DMN_NOCHDIR      0x04  /* don't change the working directory to "/" */
+
+int daemonize (unsigned int flags);
+
+#endif  /* __DAEMONIZE_H */

libSzarp2/utils/daemonize.cc

@@ -0,0 +1,136 @@
+/**
+ * System daemon tools for GNU/Linux.
+ *
+ * Copyright (C) 2015 Newterm
+ * Author: Tomasz Pieczerak <tph@newterm.pl>
+ *
+ * This file is a part of SZARP SCADA software.
+ *
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ *
+ */
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "daemonize.h"
+
+/**
+ * _signal() - a handy wrapper for changing signal actions.
+ *
+ * It's meant to be as simple as the deprecated signal(2) and as portable as
+ * sigaction(2). Why signal(2) should be avoided - see its manpage.
+ */
+typedef void sigfunc_t(int);
+
+sigfunc_t *_signal (int signo, sigfunc_t *func)
+{
+	struct sigaction act, oact;
+
+	act.sa_handler = func;
+	sigemptyset(&act.sa_mask);
+	act.sa_flags = 0;
+
+	if (signo == SIGALRM) {
+#ifdef  SA_INTERRUPT
+		act.sa_flags |= SA_INTERRUPT;   /* SunOS 4.x */
+#endif
+	}
+	else {
+#ifdef  SA_RESTART
+		act.sa_flags |= SA_RESTART;     /* SVR4, 44BSD */
+#endif
+	}
+	if (sigaction(signo, &act, &oact) < 0)
+		return SIG_ERR;
+
+	return oact.sa_handler;
+}
+
+/**
+ * daemonize() - became a system daemon, gain control.
+ *
+ * The calling process is detached from the controlling terminal and made run
+ * in the background.
+ *
+ * Returns zero on success. If an error occurs, returns -1 and sets errno to
+ * any of the errors specified for the fork(2), setsid(2), sigaction(2),
+ * chdir(2), open(2) and dup2(2).
+ */
+int daemonize (unsigned int flags)
+{
+	int i, fd;
+	pid_t pid;
+
+	/* first fork */
+	if ( (pid = fork()) == -1)
+		return -1;
+	if (pid != 0)
+		exit(0);	/* parent process */
+
+	/* create a new session */
+	setsid();
+
+	/* set up signal handlers */
+	if (_signal(SIGHUP, SIG_IGN) == SIG_ERR)
+		return -1;
+
+	if (_signal(SIGCHLD, SIG_DFL) == SIG_ERR)
+		return -1;
+
+	if (flags & DMN_SIGPIPE_IGN) {
+		if (_signal(SIGPIPE, SIG_IGN) == SIG_ERR)
+			return -1;
+	}
+
+	/* second fork, give up session leadership */
+	if ( (pid = fork()) == -1)
+		return -1;
+	if (pid != 0)
+		exit(0);	/* parent process */
+
+	/* change working directory to the root directory */
+	if (!(flags & DMN_NOCHDIR)) {
+		if (chdir("/") == -1)
+			return -1;
+	}
+
+	/* reset umask */
+	umask(0);
+
+	/* redirect stdout, stdin and stderr to /dev/null */
+	if (!(flags & DMN_NOREDIR_STD)) {
+		close(0);	/* stdout */
+		close(1);	/* stdin  */
+		close(2);	/* stderr */
+
+		if ( (fd = open("/dev/null", O_RDWR)) == -1)
+			return -1;
+
+		if ( (fd = dup2(fd, 0)) == -1)
+			return -1;
+		if ( (fd = dup2(fd, 1)) == -1)
+			return -1;
+		if ( (fd = dup2(fd, 2)) == -1)
+			return -1;
+	}
+
+	return 0;	/* done */
+}