+/* Upper bound on the length of a nlattr-formatted flow key. The longest
+ * nlattr-formatted flow key would be:
+ *
+ * struct pad nl hdr total
+ * ------ --- ------ -----
+ * OVS_KEY_ATTR_PRIORITY 4 -- 4 8
+ * OVS_KEY_ATTR_TUN_ID 8 -- 4 12
+ * OVS_KEY_ATTR_IPV4_TUNNEL 24 -- 4 28
+ * OVS_KEY_ATTR_IN_PORT 4 -- 4 8
+ * OVS_KEY_ATTR_ETHERNET 12 -- 4 16
+ * OVS_KEY_ATTR_ETHERTYPE 2 2 4 8 (outer VLAN ethertype)
+ * OVS_KEY_ATTR_8021Q 4 -- 4 8
+ * OVS_KEY_ATTR_ENCAP 0 -- 4 4 (VLAN encapsulation)
+ * OVS_KEY_ATTR_ETHERTYPE 2 2 4 8 (inner VLAN ethertype)
+ * OVS_KEY_ATTR_IPV6 40 -- 4 44
+ * OVS_KEY_ATTR_ICMPV6 2 2 4 8
+ * OVS_KEY_ATTR_ND 28 -- 4 32
+ * -------------------------------------------------
+ * total 184
+ */
+#define FLOW_BUFSIZE 184