@@ -395,7 +395,7 @@ AC_CHECK_HEADERS([ \

 	stdio.h stdarg.h \

 	time.h errno.h fcntl.h io.h direct.h \

 	ctype.h sys/types.h sys/socket.h \

-	signal.h unistd.h \

+	signal.h unistd.h dlfcn.h \

 	netinet/in.h netinet/in_systm.h \

 	netinet/tcp.h arpa/inet.h netdb.h \

 	windows.h winsock2.h ws2tcpip.h \

@@ -606,6 +606,13 @@ else

 	AC_CHECK_FUNCS(SOCKET_OPT_FUNCS)

 fi

+AC_CHECK_LIB(

+	[dl],

+	[dlopen],

+	[DL_LIBS="-ldl"]

+)

+AC_SUBST([DL_LIBS])

+

 case "${with_mem_check}" in

 	valgrind)

 		AC_CHECK_HEADER(

@@ -658,38 +665,6 @@ case "${with_mem_check}" in

 esac

 dnl

-dnl Check for dlopen -- first try libc then libdl.

-dnl

-if test "${WIN32}" != "yes" -a "${enable_plugins}" = "yes"; then

-	AC_CHECK_HEADER(

-		[dlfcn.h],

-		[AC_CHECK_FUNC(

-			[dlopen],

-			[AC_DEFINE(USE_LIBDL, 1, [Use libdl for dynamic library loading])],

-			[AC_CHECK_LIB(

-				[dl],

-				[dlopen],

-				[

-					LIBS="${LIBS} -ldl"

-					AC_DEFINE(USE_LIBDL, 1, [Use libdl for dynamic library loading])

-				],

-				[AC_MSG_RESULT([libdl library not found.])]

-			)],

-		)],

-	)

-	if test "${enable_eurephia}" = "yes"; then

-		AC_DEFINE([ENABLE_EUREPHIA], [1], [Enable support for the eurephia plug-in])

-	fi

-fi

-

-dnl

-dnl Check if LoadLibrary exists on Windows

-dnl

-if test "${WIN32}" = "yes"; then

-	AC_DEFINE(USE_LOAD_LIBRARY, 1, [Use LoadLibrary to load DLLs on Windows])

-fi

-

-dnl

 dnl check for LZO library

 dnl

 if test "${enable_lzo}" = "yes" && test "${enable_lzo_stub}" = "no"; then

@@ -898,6 +873,13 @@ test "${enable_strict_options}" = "yes" && AC_DEFINE([ENABLE_STRICT_OPTIONS_CHEC

 test "${enable_password_save}" = "yes" && AC_DEFINE([ENABLE_PASSWORD_SAVE], [1], [Allow --askpass and --auth-user-pass passwords to be read from a file])

 test "${enable_systemd}" = "yes" && AC_DEFINE([ENABLE_SYSTEMD], [1], [Enable systemd support])

+if test "${enable_plugins}" = "yes"; then

+	test "${WIN32}" != "yes" -a -z "${DL_LIBS}" && AC_MSG_ERROR([libdl is required for plugins])

+	OPTIONAL_DL_LIBS="${DL_LIBS}"

+	AC_DEFINE([ENABLE_PLUGIN], [1], [Enable systemd support])

+	test "${enable_eurephia}" = "yes" && AC_DEFINE([ENABLE_EUREPHIA], [1], [Enable support for the eurephia plug-in])

+fi

+

 if test "${enable_iproute2}" = "yes"; then

 	test -z "${IPROUTE}" && AC_MSG_ERROR([ip utility is required but missing])

 	AC_DEFINE([ENABLE_IPROUTE], [1], [enable iproute2 support])

@@ -933,6 +915,8 @@ AC_SUBST([TAP_WIN_COMPONENT_ID])

 AC_SUBST([TAP_WIN_MIN_MAJOR])

 AC_SUBST([TAP_WIN_MIN_MINOR])

+AC_SUBST([OPTIONAL_DL_LIBS])

+

 AM_CONDITIONAL([WIN32], [test "${WIN32}" = "yes"])

 AC_CONFIG_FILES([

@@ -95,7 +95,9 @@ openvpn_SOURCES = \

 	tun.c tun.h \

 	win32.h win32.c \

 	cryptoapi.h cryptoapi.c

+openvpn_LDADD = \

+	$(OPTIONAL_DL_LIBS)

 if WIN32

 openvpn_SOURCES += openvpn_win32_resources.rc

-openvpn_LDADD = -lgdi32 -lws2_32 -lwininet -lcrypt32 -liphlpapi -lwinmm -lshell32

+openvpn_LDADD += -lgdi32 -lws2_32 -lwininet -lcrypt32 -liphlpapi -lwinmm -lshell32

 endif

@@ -26,6 +26,10 @@

 #ifdef ENABLE_PLUGIN

+#ifdef HAVE_DLFCN_H

+#include <dlfcn.h>

+#endif

+

 #include "buffer.h"

 #include "error.h"

 #include "misc.h"

@@ -160,7 +164,7 @@ plugin_option_list_print (const struct plugin_option_list *list, int msglevel)

 }

 #endif

-#if defined(USE_LIBDL)

+#ifndef WIN32

 static void

 libdl_resolve_symbol (void *handle, void **dest, const char *symbol, const char *plugin_name, const unsigned int flags)

@@ -170,7 +174,7 @@ libdl_resolve_symbol (void *handle, void **dest, const char *symbol, const char

     msg (M_FATAL, "PLUGIN: could not find required symbol '%s' in plugin shared object %s: %s", symbol, plugin_name, dlerror());

 }

-#elif defined(USE_LOAD_LIBRARY)

+#else

 static void

 dll_resolve_symbol (HMODULE module, void **dest, const char *symbol, const char *plugin_name, const unsigned int flags)

@@ -191,7 +195,7 @@ plugin_init_item (struct plugin *p, const struct plugin_option *o)

   p->so_pathname = o->so_pathname;

   p->plugin_type_mask = plugin_supported_types ();

-#if defined(USE_LIBDL)

+#ifndef WIN32

   p->handle = NULL;

 #if defined(PLUGIN_LIBDIR)

@@ -220,7 +224,7 @@ plugin_init_item (struct plugin *p, const struct plugin_option *o)

 # define PLUGIN_SYM(var, name, flags) libdl_resolve_symbol (p->handle, (void*)&p->var, name, p->so_pathname, flags)

-#elif defined(USE_LOAD_LIBRARY)

+#else

   rel = !absolute_pathname (p->so_pathname);

   p->module = LoadLibraryW (wide_string (p->so_pathname, &gc));

@@ -427,10 +431,10 @@ plugin_close_item (struct plugin *p)

       if (p->plugin_handle)

 	(*p->close)(p->plugin_handle);

-#if defined(USE_LIBDL)

+#ifndef WIN32

       if (dlclose (p->handle))

 	msg (M_WARN, "PLUGIN_CLOSE: dlclose() failed on plugin: %s", p->so_pathname);

-#elif defined(USE_LOAD_LIBRARY)

+#elif defined(WIN32)

       if (!FreeLibrary (p->module))

 	msg (M_WARN, "PLUGIN_CLOSE: FreeLibrary() failed on plugin: %s", p->so_pathname);

 #endif

@@ -59,9 +59,9 @@ struct plugin {

   unsigned int plugin_type_mask;

   int requested_initialization_point;

-#if defined(USE_LIBDL)

+#ifndef WIN32

   void *handle;

-#elif defined(USE_LOAD_LIBRARY)

+#else

   HMODULE module;

 #endif

@@ -156,10 +156,6 @@

 #include <grp.h>

 #endif

-#ifdef USE_LIBDL

-#include <dlfcn.h>

-#endif

-

 #ifdef HAVE_NETDB_H

 #include <netdb.h>

 #endif

@@ -507,13 +503,6 @@ socket_defined (const socket_descriptor_t sd)

 #endif

 /*

- * Do we have a plug-in capability?

- */

-#if defined(USE_LIBDL) || defined(USE_LOAD_LIBRARY)

-#define ENABLE_PLUGIN

-#endif

-

-/*

  * Enable deferred authentication?

  */

 #if defined(ENABLE_DEF_AUTH) && P2MP_SERVER && defined(ENABLE_PLUGIN)