It does not make sense to insert a specific route for 224/4 when the

default one is good enough.
So merge rc.conf(8)'s 'multicast_router' and 'multicast_host' into a
single 'multicast'.  If set to YES the reject route for 224/4 is not
inserted by netstart(8).
Manual bits from jmc@
ok henning@, ajacoutot@

src/etc/netstart

@@ -1,6 +1,6 @@
 #!/bin/sh -
 #
-#	$OpenBSD: netstart,v 1.162 2015/11/12 23:11:11 rpe Exp $
+#	$OpenBSD: netstart,v 1.163 2015/12/05 18:43:12 mpi Exp $
 
 # Turn off Strict Bourne shell mode.
 set +o sh
@@ -270,37 +270,18 @@ done
 # Multicast routing.
 #
 # The routing to the 224.0.0.0/4 net is setup according to these rules:
-# multicast_host	multicast_router	route		comment
-# NO			NO			-reject		no multicast
-# NO			YES			none installed	daemon will run
-# YES/interface		NO			-interface	YES=def. iface
-#	   Any other combination		-reject		config error
+# multicast			route			comment
+# NO				-reject			no multicast
+# YES				none installed		daemon can run
+# Any other combination		-reject			config error
 route -qn delete 224.0.0.0/4 >/dev/null 2>&1
-case "$multicast_host:$multicast_router" in
-NO:NO)
+case $multicast in
+NO)
 	route -qn add -net 224.0.0.0/4 -interface 127.0.0.1 -reject >/dev/null
 	;;
-NO:YES)
+YES)
 	;;
-*:NO)
-	maddr=$(if [[ $multicast_host == YES ]]; then
-		ed -s '!route -qn show -inet' <<EOF
-/^default/p
-EOF
-	else
-		ed -s "!ifconfig $multicast_host" <<EOF
-/^	inet /p
-EOF
-	fi 2>/dev/null)
-	if [[ -n $maddr ]]; then
-		set $maddr
-		route -qn add -net 224.0.0.0/4 -interface $2 >/dev/null
-	else
-		route -qn add -net 224.0.0.0/4 -interface \
-			127.0.0.1 -reject >/dev/null
-	fi
-	;;
-*:*)
+*)
 	echo 'config error, multicasting disabled until rc.conf is fixed'
 	route -qn add -net 224.0.0.0/4 -interface 127.0.0.1 -reject >/dev/null
 	;;

src/etc/rc.conf

@@ -1,4 +1,4 @@
-#	$OpenBSD: rc.conf,v 1.208 2015/12/05 09:55:18 jasper Exp $
+#	$OpenBSD: rc.conf,v 1.209 2015/12/05 18:43:12 mpi Exp $
 
 # DO NOT EDIT THIS FILE!!
 #
@@ -93,8 +93,7 @@ accounting=NO		# process accounting (using /var/account/acct)
 
 # Multicast routing configuration
 # Please look at netstart(8) for a detailed description if you change these
-multicast_host=NO	# Route all multicast packets to a single interface
-multicast_router=NO	# A multicast routing daemon will be run, e.g. mrouted
+multicast=NO		# Reject IPv4 multicast packets by default
 
 # miscellaneous other flags
 amd_master=/etc/amd/master	# AMD 'master' map

src/etc/rc.d/rc.subr

@@ -1,4 +1,4 @@
-#	$OpenBSD: rc.subr,v 1.100 2015/10/16 20:12:00 ajacoutot Exp $
+#	$OpenBSD: rc.subr,v 1.101 2015/12/05 18:43:12 mpi Exp $
 #
 # Copyright (c) 2010, 2011, 2014 Antoine Jacoutot <ajacoutot@openbsd.org>
 # Copyright (c) 2010, 2011 Ingo Schwarze <schwarze@openbsd.org>
@@ -124,7 +124,7 @@ _rc_parse_conf() {
 	local _l _rcfile _val
 	set -A _allowed_keys -- \
 		spamd_black pf ipsec check_quotas accounting \
-		multicast_host multicast_router amd_master \
+		multicast amd_master \
 		shlib_dirs pkg_scripts nfs_server
 
 	[ $# -gt 0 ] || set -- /etc/rc.conf /etc/rc.conf.local