+ pg_interface_t *pi = pool_elt_at_index (pg->interfaces, s->pg_if_index);
+ /*
+ * Default the RX interface if unset. It's a bad mistake to
+ * set [VLIB_TX] prior to ip lookup, since the ip lookup code
+ * interprets [VLIB_TX] as a fib index...
+ */
+ s->sw_if_index[VLIB_RX] = pi->sw_if_index;