-/* NXM_ bit OFPFW_* bit dl_type nw_proto */
-/* ------------ -------------- ----------- ------------- */
-DEFINE_FIELD (OF_IN_PORT, OFPFW_IN_PORT, 0, 0)
-DEFINE_FIELD (OF_ETH_DST, OFPFW_DL_DST, 0, 0)
-DEFINE_FIELD (OF_ETH_SRC, OFPFW_DL_SRC, 0, 0)
-DEFINE_FIELD (OF_ETH_TYPE, OFPFW_DL_TYPE, 0, 0)
-DEFINE_FIELD_M(OF_VLAN_TCI, 0, 0, 0)
-DEFINE_FIELD (OF_IP_TOS, OFPFW_NW_TOS, ETH_TYPE_IP, 0)
-DEFINE_FIELD (OF_IP_PROTO, OFPFW_NW_PROTO, ETH_TYPE_IP, 0)
-DEFINE_FIELD_M(OF_IP_SRC, 0, ETH_TYPE_IP, 0)
-DEFINE_FIELD_M(OF_IP_DST, 0, ETH_TYPE_IP, 0)
-DEFINE_FIELD (OF_TCP_SRC, OFPFW_TP_SRC, ETH_TYPE_IP, IP_TYPE_TCP)
-DEFINE_FIELD (OF_TCP_DST, OFPFW_TP_DST, ETH_TYPE_IP, IP_TYPE_TCP)
-DEFINE_FIELD (OF_UDP_SRC, OFPFW_TP_SRC, ETH_TYPE_IP, IP_TYPE_UDP)
-DEFINE_FIELD (OF_UDP_DST, OFPFW_TP_DST, ETH_TYPE_IP, IP_TYPE_UDP)
-DEFINE_FIELD (OF_ICMP_TYPE, OFPFW_TP_SRC, ETH_TYPE_IP, IP_TYPE_ICMP)
-DEFINE_FIELD (OF_ICMP_CODE, OFPFW_TP_DST, ETH_TYPE_IP, IP_TYPE_ICMP)
-DEFINE_FIELD (OF_ARP_OP, OFPFW_NW_PROTO, ETH_TYPE_ARP, 0)
-DEFINE_FIELD_M(OF_ARP_SPA, 0, ETH_TYPE_ARP, 0)
-DEFINE_FIELD_M(OF_ARP_TPA, 0, ETH_TYPE_ARP, 0)
-DEFINE_FIELD (NX_TUN_ID, NXFW_TUN_ID, 0, 0)
+/* NXM_ suffix MFF_ field ID rw? */
+/* ------------ ------------ ----- */
+DEFINE_FIELD_M(NX_TUN_ID, MFF_TUN_ID, true)
+DEFINE_FIELD (OF_IN_PORT, MFF_IN_PORT, false)
+DEFINE_FIELD_M(OF_ETH_DST, MFF_ETH_DST, true)
+DEFINE_FIELD (OF_ETH_SRC, MFF_ETH_SRC, true)
+DEFINE_FIELD (OF_ETH_TYPE, MFF_ETH_TYPE, false)
+DEFINE_FIELD_M(OF_VLAN_TCI, MFF_VLAN_TCI, true)
+DEFINE_FIELD (OF_IP_TOS, MFF_IP_TOS, true)
+DEFINE_FIELD (OF_IP_PROTO, MFF_IP_PROTO, false)
+DEFINE_FIELD_M(OF_IP_SRC, MFF_IPV4_SRC, true)
+DEFINE_FIELD_M(OF_IP_DST, MFF_IPV4_DST, true)
+DEFINE_FIELD (OF_TCP_SRC, MFF_TCP_SRC, true)
+DEFINE_FIELD (OF_TCP_DST, MFF_TCP_DST, true)
+DEFINE_FIELD (OF_UDP_SRC, MFF_UDP_SRC, true)
+DEFINE_FIELD (OF_UDP_DST, MFF_UDP_DST, true)
+DEFINE_FIELD (OF_ICMP_TYPE, MFF_ICMP_TYPE, false)
+DEFINE_FIELD (OF_ICMP_CODE, MFF_ICMP_CODE, false)
+DEFINE_FIELD (OF_ARP_OP, MFF_ARP_OP, false)
+DEFINE_FIELD_M(OF_ARP_SPA, MFF_ARP_SPA, false)
+DEFINE_FIELD_M(OF_ARP_TPA, MFF_ARP_TPA, false)
+DEFINE_FIELD (NX_ARP_SHA, MFF_ARP_SHA, false)
+DEFINE_FIELD (NX_ARP_THA, MFF_ARP_THA, false)
+DEFINE_FIELD_M(NX_IPV6_SRC, MFF_IPV6_SRC, false)
+DEFINE_FIELD_M(NX_IPV6_DST, MFF_IPV6_DST, false)
+/* XXX should we have MFF_ICMPV4_TYPE and MFF_ICMPV6_TYPE? */
+DEFINE_FIELD (NX_ICMPV6_TYPE,MFF_ICMP_TYPE, false)
+DEFINE_FIELD (NX_ICMPV6_CODE,MFF_ICMP_CODE, false)
+DEFINE_FIELD (NX_ND_TARGET, MFF_ND_TARGET, false)
+DEFINE_FIELD (NX_ND_SLL, MFF_ND_SLL, false)
+DEFINE_FIELD (NX_ND_TLL, MFF_ND_TLL, false)
+
+DEFINE_FIELD_M(NX_REG0, MFF_REG0, true)
+#if FLOW_N_REGS >= 2
+DEFINE_FIELD_M(NX_REG1, MFF_REG1, true)
+#endif
+#if FLOW_N_REGS >= 3
+DEFINE_FIELD_M(NX_REG2, MFF_REG2, true)
+#endif
+#if FLOW_N_REGS >= 4
+DEFINE_FIELD_M(NX_REG3, MFF_REG3, true)
+#endif
+#if FLOW_N_REGS > 4
+#error
+#endif