-/* Netlink and OpenFlow both contain 64-bit values that are only guaranteed to
- * be aligned on 32-bit boundaries. These types help.
+/* These types help with a few funny situations:
+ *
+ * - The Ethernet header is 14 bytes long, which misaligns everything after
+ * that. One can put 2 "shim" bytes before the Ethernet header, but this
+ * helps only if there is exactly one Ethernet header. If there are two,
+ * as with GRE and VXLAN (and if the inner header doesn't use this
+ * trick--GRE and VXLAN don't) then you have the choice of aligning the
+ * inner data or the outer data. So it seems better to treat 32-bit fields
+ * in protocol headers as aligned only on 16-bit boundaries.
+ *
+ * - ARP headers contain misaligned 32-bit fields.
+ *
+ * - Netlink and OpenFlow contain 64-bit values that are only guaranteed to
+ * be aligned on 32-bit boundaries.