ppp: honor ip6table for IPv6 PPP interfaces

as we do for IPv4 PPP interfaces. When we create the
dynamic IPv6 interface we should inherit ip6table from
main interface.

Signed-off-by: Ulrich Weber <ulrich.weber@riverbed.com>

package/network/services/ppp/files/lib/netifd/ppp6-up

@@ -22,6 +22,7 @@ if [ -n "$AUTOIPV6" ]; then
 	json_add_string ifname "@$PPP_IPPARAM"
 	json_add_string proto "dhcpv6"
 	[ -n "$EXTENDPREFIX" ] && json_add_string extendprefix 1
+	[ -n "$IP6TABLE" ] && json_add_string ip6table $IP6TABLE
 	json_close_object
 	ubus call network add_dynamic "$(json_dump)"
 fi

package/network/services/ppp/files/ppp.sh

@@ -88,7 +88,7 @@ ppp_generic_setup() {
 	local config="$1"; shift
 	local localip
 
-	json_get_vars ipv6 demand keepalive keepalive_adaptive username password pppd_options pppname unnumbered persist maxfail holdoff
+	json_get_vars ipv6 ip6table demand keepalive keepalive_adaptive username password pppd_options pppname unnumbered persist maxfail holdoff
 	if [ "$ipv6" = 0 ]; then
 		ipv6=""
 	elif [ -z "$ipv6" -o "$ipv6" = auto ]; then
@@ -136,6 +136,7 @@ ppp_generic_setup() {
 		${lcp_failure:+lcp-echo-interval $lcp_interval lcp-echo-failure $lcp_failure $lcp_adaptive} \
 		${ipv6:++ipv6} \
 		${autoipv6:+set AUTOIPV6=1} \
+		${ip6table:+set IP6TABLE=$ip6table} \
 		nodefaultroute \
 		usepeerdns \
 		$demand $persist maxfail $maxfail \