- * For a packet received via GRE tunnel including a (32-bit) key, the key is
- * stored in the low 32-bits and the high bits are zeroed. For other packets,
- * the value is 0.
+ * For a packet received via a GRE or VXLAN tunnel including a (32-bit) key, the
+ * key is stored in the low 32-bits and the high bits are zeroed. For other
+ * packets, the value is 0.
+ *
+ * All zero bits, for packets not received via a keyed tunnel.