UNIX services write logs to stdout

To better adopt SoftEther VPN for execution in Docker container all
services output logs to stdout if running in foreground.

src/Mayaqua/Mayaqua.c

@@ -133,6 +133,7 @@ BOOL kernel_status_inited = false;				// Kernel state initialization flag
 bool g_little_endian = true;
 char *cmdline = NULL;							// Command line
 wchar_t *uni_cmdline = NULL;					// Unicode command line
+bool g_foreground = false;					// Execute service in foreground mode
 
 // Static variable
 static char *exename = NULL;						// EXE file name (ANSI)
@@ -512,6 +513,7 @@ void InitMayaqua(bool memcheck, bool debug, int argc, char **argv)
 		// Fail this for some reason when this is called this in .NET mode
 		setbuf(stdout, NULL);
 	}
+	g_foreground = (argc >= 3 && StrCmpi(argv[2], UNIX_SVC_ARG_FOREGROUND) == 0);
 
 	// Acquisition whether NT
 #ifdef	OS_WIN32

src/Mayaqua/Mayaqua.h

@@ -395,6 +395,7 @@ extern char *cmdline;
 extern wchar_t *uni_cmdline;
 extern bool g_little_endian;
 extern LOCK *tick_manual_lock;
+extern bool g_foreground;
 
 // Kernel state
 #define	NUM_KERNEL_STATUS	128

src/Mayaqua/Unix.c

@@ -1703,6 +1703,23 @@ void *UnixFileOpen(char *name, bool write_mode, bool read_lock)
 	return (void *)p;
 }
 
+// Get UNIXIO object for stdout
+void* GetUnixio4Stdout()
+{
+	static UNIXIO unixio =
+	{
+		.fd = -1,
+		.write_mode = true
+	};
+
+	if (g_foreground)
+	{
+		unixio.fd = STDOUT_FILENO;
+		return &unixio;
+	}
+	return NULL;
+}
+
 // Return the current thread ID
 UINT UnixThreadId()
 {

src/Mayaqua/Unix.h

@@ -179,6 +179,7 @@ void *UnixFileOpen(char *name, bool write_mode, bool read_lock);
 void *UnixFileOpenW(wchar_t *name, bool write_mode, bool read_lock);
 void *UnixFileCreate(char *name);
 void *UnixFileCreateW(wchar_t *name);
+void *GetUnixio4Stdout();
 bool UnixFileWrite(void *pData, void *buf, UINT size);
 bool UnixFileRead(void *pData, void *buf, UINT size);
 void UnixFileClose(void *pData, bool no_flush);