add ip6defaultif, which configures default outgoing interface

when no neighboring router is found (rare case).  this is to conform
strictly to the ND spec.  it is safe to leave it empty.

src/etc/rc

@@ -1,4 +1,4 @@
-#	$OpenBSD: rc,v 1.129 2000/01/30 02:45:51 millert Exp $
+#	$OpenBSD: rc,v 1.130 2000/02/28 17:28:35 itojun Exp $
 
 # System startup script run by init on autoboot
 # or after single-user.
@@ -400,6 +400,10 @@ if ifconfig lo0 inet6 >/dev/null 2>&1; then
 			echo -n ' rtsold'
 			/usr/sbin/rtsold ${rtsold_flags}
 		fi
+
+		if [ "X${ip6defaultif}" != X"" ]; then
+			/usr/sbin/ndp -I ${ip6defaultif}
+		fi
 	else
 		# $route6d_flags is imported from /etc/rc.conf;
 		# If $route6d_flags == NO, then route6d isn't run.

src/etc/rc.conf

@@ -1,6 +1,6 @@
 #!/bin/sh -
 #
-#	$OpenBSD: rc.conf,v 1.43 2000/02/19 14:36:02 deraadt Exp $
+#	$OpenBSD: rc.conf,v 1.44 2000/02/28 17:28:35 itojun Exp $
 
 # set these to "NO" to turn them off.  otherwise, they're used as flags
 routed_flags=NO		# for normal use: "-q"
@@ -19,6 +19,7 @@ mopd_flags=NO		# for normal use: "-a"
 httpd_flags=NO		# for normal use: "" (or "-DSSL" after reading ssl(8))
 apmd_flags=NO		# for normal use: ""
 dhcpd_flags=NO		# for normal use: "-q"
+ip6defaultif=""		# for normal use: ""
 rtadvd_flags=NO		# for normal use: list of interfaces
 			# be sure to set net.inet6.ip6.forwarding=1
 route6d_flags=NO	# for normal use: ""