AS_HELP_STRING([--enable-vde], [enable support for Virtual Distributed Ethernet]),
[ AS_IF([test "x$enable_vde" = "xyes"],
[ AC_CHECK_HEADERS(libvdeplug_dyn.h, [], [AC_MSG_ERROR([VDE plug header files not found.]); break])
+ AC_CHECK_LIB(dl, dlopen, [LIBS="$LIBS -ldl"], [AC_MSG_ERROR([VDE plug depends on libdl.]); break])
AC_DEFINE(ENABLE_VDE, 1, [Support for VDE])
vde=true
],