-/* Returns 1 if 'packet' is an IP fragment, 0 otherwise.
- * 'tun_id' is in network byte order, while 'in_port' is in host byte order.
- * These byte orders are the same as they are in struct odp_flow_key. */
+/* 'tun_id' is in network byte order, while 'in_port' is in host byte order.
+ * These byte orders are the same as they are in struct odp_flow_key.
+ *
+ * Initializes packet header pointers as follows:
+ *
+ * - packet->l2 to the start of the Ethernet header.
+ *
+ * - packet->l3 to just past the Ethernet header, or just past the
+ * vlan_header if one is present, to the first byte of the payload of the
+ * Ethernet frame.
+ *
+ * - packet->l4 to just past the IPv4 header, if one is present and has a
+ * correct length, and otherwise NULL.
+ *
+ * - packet->l7 to just past the TCP or UDP or ICMP header, if one is
+ * present and has a correct length, and otherwise NULL.
+ */