diff --git a/cf/krb-ipv6.m4 b/cf/krb-ipv6.m4
index 292dc582e..0a74cf08a 100644
--- a/cf/krb-ipv6.m4
+++ b/cf/krb-ipv6.m4
@@ -40,5 +40,91 @@ ac_cv_lib_ipv6=yes,
 ac_cv_lib_ipv6=no))
 if test "$ac_cv_lib_ipv6" = yes; then
   AC_DEFINE(HAVE_IPV6)
+
+	dnl check for different v6 implementations (by itojun)
+	v6type=unknown
+	v6lib=none
+
+	AC_MSG_CHECKING([ipv6 stack type])
+	for i in v6d toshiba kame inria zeta linux; do
+		case $i in
+		v6d)
+			AC_EGREP_CPP(yes, [dnl
+#include </usr/local/v6/include/sys/types.h>
+#ifdef __V6D__
+yes
+#endif],
+				[v6type=$i; v6lib=v6;
+				v6libdir=/usr/local/v6/lib;
+				CFLAGS="-I/usr/local/v6/include $CFLAGS"])
+			;;
+		toshiba)
+			AC_EGREP_CPP(yes, [dnl
+#include <sys/param.h>
+#ifdef _TOSHIBA_INET6
+yes
+#endif],
+				[v6type=$i; v6lib=inet6;
+				v6libdir=/usr/local/v6/lib;
+				CFLAGS="-DINET6 $CFLAGS"])
+			;;
+		kame)
+			AC_EGREP_CPP(yes, [dnl
+#include <netinet/in.h>
+#ifdef __KAME__
+yes
+#endif],
+				[v6type=$i; v6lib=inet6;
+				v6libdir=/usr/local/v6/lib;
+				CFLAGS="-DINET6 $CFLAGS"])
+			;;
+		inria)
+			AC_EGREP_CPP(yes, [dnl
+#include <netinet/in.h>
+#ifdef IPV6_INRIA_VERSION
+yes
+#endif],
+				[v6type=$i; CFLAGS="-DINET6 $CFLAGS"])
+			;;
+		zeta)
+			AC_EGREP_CPP(yes, [dnl
+#include <sys/param.h>
+#ifdef _ZETA_MINAMI_INET6
+yes
+#endif],
+				[v6type=$i; v6lib=inet6;
+				v6libdir=/usr/local/v6/lib;
+				CFLAGS="-DINET6 $CFLAGS"])
+			;;
+		linux)
+			if test -d /usr/inet6; then
+				v6type=$i
+				v6lib=inet6
+				v6libdir=/usr/inet6
+				CFLAGS="-DINET6 $CFLAGS"
+			fi
+			;;
+		esac
+		if test "$v6type" != "unknown"; then
+			break
+		fi
+	done
+	AC_MSG_RESULT($v6type)
+
+	if test "$v6lib" != "none"; then
+		for dir in $v6libdir /usr/local/v6/lib /usr/local/lib; do
+			if test -d $dir -a -f $dir/lib$v6lib.a; then
+				LIBS="-L$dir -l$v6lib $LIBS"
+				break
+			fi
+		done
+dnl		AC_CHECK_LIB($v6lib, getaddrinfo,
+dnl			[SERVER_LIBS="-l$v6lib $SERVER_LIBS"],
+dnl			[dnl
+dnl			echo "Fatal: no $v6lib library found.  cannot continue."
+dnl			echo "You need to fetch lib$v6lib.a from appropriate v6 kit and"
+dnl			echo 'compile beforehand.'
+dnl			exit 1])
+	fi
 fi
 ])