--- a/configure.ac	Tue Feb 24 17:09:42 2009 -0800
+++ b/configure.ac	Wed Apr 15 10:50:05 2009 -0600
@@ -225,19 +225,31 @@
 dnl +-------------------------------------------------------------------+
 dnl | Checking for libasyncns                                           |
 dnl +-------------------------------------------------------------------+
-AC_ARG_WITH(asyncns, [  --with-asyncns=yes/no  define whether to use libasyncns, default=no],
-            ac_asyncns=$withval,
-            ac_asyncns=no
-            )
+AC_ARG_WITH(asyncns,
+	AS_HELP_STRING([--with-asyncns],
+		[define whether to use libasyncns, @<:@default=no@:>@ (internal/system/no)]),
+	ac_asyncns=$withval,
+	ac_asyncns=no)
 
 enable_asyncns=no
+have_asyncns_system=no
 if test x$ac_asyncns != xno; then
 	enable_asyncns=yes
 	AC_DEFINE(HAVE_ASYNCNS, 1, [Whether to use libasyncns])
+
+	if test x$ac_asyncns = xsystem; then
+		PKG_CHECK_MODULES(ASYNCNS, [libasyncns >= 0.3],
+			[have_asyncns_system=yes],
+			[have_asyncns_system=no])
+	fi
 else
 	echo "Not using asynchronous dns lookups"
 fi
 
+AC_SUBST(ASYNCNS_CFLAGS)
+AC_SUBST(ASYNCNS_LIBS)
+AM_CONDITIONAL(USE_SYSTEM_ASYNCNS, test x$have_asyncns_system = xyes)
+
 dnl +-------------------------------------------------------------------+
 dnl | Checking for Linux TCP/IP stack                                   |
 dnl +-------------------------------------------------------------------+