tunnel: improve validation of options

executor-scripts/linux/tunnel

@@ -2,6 +2,23 @@
 
 # Based on alpine's tunnel configuration script.
 # Copyright (c) 2017 Kaarle Ritvanen
+# Copyright (c) 2020 Ariadne Conill (extended for ifupdown-ng)
+
+[ -z "$IF_TUNNEL_LOCAL" ] && exit 1
+[ -z "$IF_TUNNEL_REMOTE" ] && exit 1
+[ -z "$IF_TUNNEL_MODE" ] && exit 1
+
+COMMAND="tunnel"
+FAMILY="-4"
+
+case "$IF_TUNNEL_MODE" in
+gretap)
+	COMMAND="link"
+	;;
+vti6|ipip6|ip6*)
+	FAMILY="-6"
+	;;
+esac
 
 PARAMS=$(set | sed -E '
 	s/^IF_TUNNEL_([A-Z0-9_]+)=(.+)/\1\n\2/
@@ -19,10 +36,10 @@ PARAMS=$(set | sed -E '
 
 case "$PHASE" in
 pre-up)
-	${MOCK} eval ip tunnel add $IFACE $PARAMS
+	${MOCK} eval ip $FAMILY $COMMAND add $IFACE $PARAMS
 	;;
 post-down)
-	${MOCK} ip tunnel del $IFACE
+	${MOCK} ip $FAMILY $COMMAND del $IFACE
 	;;
 depend)
 	echo "$IF_TUNNEL_DEV"