text: /*
   * Copyright (c) 2011, 2012, 2013, 2014 Nicira, Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at:
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #ifndef META_FLOW_H
  #define META_FLOW_H 1
  
  #include <sys/types.h>
  #include <netinet/in.h>
  #include <netinet/ip6.h>
  #include "bitmap.h"
  #include "flow.h"
  #include "ofp-errors.h"
  #include "packets.h"
  #include "util.h"
  
  struct ds;
  struct match;
  
  /* Open vSwitch fields
   * ===================
   *
   * A "field" is a property of a packet.  Most familiarly, "data fields" are
   * fields that can be extracted from a packet.
   *
   * Some data fields are always present as a consequence of the basic networking
   * technology in use.  Ethernet is the assumed base technology for current
   * versions of OpenFlow and Open vSwitch, so Ethernet header fields are always
   * available.
   *
   * Other data fields are not always present.  A packet contains ARP fields, for
   * example, only when its Ethernet header indicates the Ethertype for ARP,
   * 0x0806.  We say that a field is "applicable" when it is it present in a
   * packet, and "inapplicable" when it is not, and refer to the conditions that
   * determine whether a field is applicable as "prerequisites".  Some
   * VLAN-related fields are a special case: these fields are always applicable,
   * but have a designated value or bit that indicates whether a VLAN header is
   * present, with the remaining values or bits indicating the VLAN header's
   * content (if it is present).  See MFF_VLAN_TCI for an example.
   *
   * Conceptually, an inapplicable field does not have a value, not even a
   * nominal ``value'' such as all-zero-bits.  In many circumstances, OpenFlow
   * and Open vSwitch allow references only to applicable fields.  For example,
   * one may match a given field only if the match includes the field's
   * prerequisite, e.g. matching an ARP field is only allowed if one also matches
   * on Ethertype 0x0806.
   *
   * (Practically, however, OVS represents a field's value as some fixed member
   * in its "struct flow", so accessing that member will obtain some value.  Some
   * members are used for more than one purpose, e.g. the "tp_src" member
   * represents the TCP, UDP, and SCTP source port, so the value read may not
   * even make sense.  For this reason, it is important to know whether a field's
   * prerequisites are satisfied before attempting to read it.)
   *
   * Sometimes a packet may contain multiple instances of a header.  For example,
   * a packet may contain multiple VLAN or MPLS headers, and tunnels can cause
   * any data field to recur.  OpenFlow and Open vSwitch do not address these
   * cases uniformly.  For VLAN and MPLS headers, only the outermost header is
   * accessible, so that inner headers may be accessed only by ``popping''
   * (removing) the outer header.  (Open vSwitch supports only a single VLAN
   * header in any case.)  For tunnels, e.g. GRE or VXLAN, the outer header and
   * inner headers are treated as different data fields.
   *
   * OpenFlow and Open vSwitch support some fields other than data fields.
   * "Metadata fields" relate to the origin or treatment of a packet, but they
   * are not extracted from the packet data itself.  One example is the physical
   * port on which a packet arrived at the switch.  "Register fields" act like
   * variables: they give an OpenFlow switch space for temporary storage while
   * processing a packet.  Existing metadata and register fields have no
   * prerequisites.
   *
   * A field's value consists of an integral number of bytes.  Most data fields
   * are copied directly from protocol headers, e.g. at layer 2, MFF_ETH_SRC is
   * copied from the Ethernet source address and MFF_ETH_DST from the destination
   * address.  Other data fields are copied from a packet with padding, usually
   * with zeros and in the most significant positions (see e.g. MFF_MPLS_LABEL)
   * but not always (see e.g. MFF_IP_DSCP).  A final category of data fields is
   * transformed in other ways as they are copied from the packets, to make them
   * more useful for matching, e.g. MFF_IP_FRAG describes whether a packet is a
   * fragment but it is not copied directly from the IP header.
   *
   *
   * Field specifications
   * ====================
   *
   * Each of the enumeration values below represents a field.  The comments
   * preceding each enum must be in a stylized form that is parsed at compile
   * time by the extract-ofp-fields program.  The comment itself consists of a
   * series of paragraphs separate by blank lines.  The paragraphs consist of:
   *
   *     - The first paragraph gives the user-visible name of the field as a
   *       quoted string.  This is the name used for parsing and formatting the
   *       field.
   *
   *       For historical reasons, some fields have an additional name that is
   *       accepted as an alternative in parsing.  This name, when there is one,
   *       is given as a quoted string in parentheses along with "aka".  For
   *       example:
   *
   *           "tun_id" (aka "tunnel_id").
   *
   *       New fields should have only one name.
   *
   *     - Any number of paragraphs of free text that describe the field.  This
   *       is meant for human readers, so extract-ofp-fields ignores it.
   *
   *     - A final paragraph that consists of a series of key-value pairs, one
   *       per line, in the form "key: value." where the period at the end of the
   *       line is a mandatory part of the syntax.
   *
   * Every field must specify the following key-value pairs:
   *
   *   Type:
   *
   *     The format and size of the field's value.  Some possible values are
   *     generic:
   *
   *         u8: A one-byte field.
   *         be16: A two-byte field.
   *         be32: A four-byte field.
   *         be64: An eight-byte field.
   *
   *     The remaining values imply more about the value's semantics, though OVS
   *     does not currently take advantage of this additional information:
   *
   *         MAC: A six-byte field whose value is an Ethernet address.
   *         IPv6: A 16-byte field whose value is an IPv6 address.
   *
   *   Maskable:
   *
   *     Either "bitwise", if OVS supports matching any subset of bits in the
   *     field, or "no", if OVS only supports matching or wildcarding the entire
   *     field.
   *
   *   Formatting:
   *
   *     Explains how a field's value is formatted and parsed for human
   *     consumption.  Some of the options are fairly generally useful:
   *
   *       decimal: Formats the value as a decimal number.  On parsing, accepts
   *         decimal (with no prefix), hexadecimal with 0x prefix, or octal
   *         with 0 prefix.
   *
   *       hexadecimal: Same as decimal except nonzero values are formatted in
   *         hex with 0x prefix.  The default for parsing is *not* hexadecimal:
   *         only with a 0x prefix is the input in hexadecimal.
   *
   *       Ethernet: Formats and accepts the common format xx:xx:xx:xx:xx:xx.
   *         6-byte fields only.
   *
   *       IPv4: Formats and accepts the common format w.x.y.z.  4-byte fields
   *         only.
   *
   *       IPv6: Formats and accepts the common IPv6 formats.  16-byte fields
   *         only.
   *
   *       OpenFlow 1.0 port: Accepts an OpenFlow well-known port name
   *         (e.g. "IN_PORT") in uppercase or lowercase, or a 16-bit port
   *         number in decimal.  Formats ports using their well-known names in
   *         uppercase, or in decimal otherwise.  2-byte fields only.
   *
   *       OpenFlow 1.1+ port: Same syntax as for OpenFlow 1.0 ports but for
   *         4-byte OpenFlow 1.1+ port number fields.
   *
   *     Others are very specific to particular fields:
   *
   *       frag: One of the strings "no", "first", "later", "yes", "not_later"
   *         describing which IPv4/v6 fragments are matched.
   *
   *       tunnel flags: Any number of the strings "df", "csum", "key", or
   *         "oam" separated by "|".
   *
   *       TCP flags: See the description of tcp_flags in ovs-ofctl(8).
   *
   *   Prerequisites:
   *
   *     The field's prerequisites.  The values should be straightfoward.
   *
   *   Access:
   *
   *     Either "read-only", for a field that cannot be changed via OpenFlow, or
   *     "read/write" for a modifiable field.
   *
   *   NXM:
   *
   *     If the field has an NXM field assignment, then this specifies the NXM
   *     name of the field (e.g. "NXM_OF_ETH_SRC"), followed by its nxm_type in
   *     parentheses, followed by "since v<x>.<y>" specifying the version of Open
   *     vSwitch that first supported this field in NXM (e.g. "since v1.1" if it
   *     was introduced in Open vSwitch 1.1).
   *
   *     The NXM name must begin with NXM_OF_ or NXM_NX_.  This allows OVS to
   *     determine the correct NXM class.
   *
   *     If the field does not have an NXM field assignment, specify "none".
   *
   *   OXM:
   *
   *     If the field has an OXM field assignment, then this specifies the OXM
   *     name of the field (e.g. "OXM_OF_ETH_SRC"), followed by its nxm_type in
   *     parentheses, followed by "since OF<a>.<b> v<x>.<y>" specifying the
   *     versions of OpenFlow and Open vSwitch that first supported this field in
   *     OXM (e.g. "since OF1.3 and v1.10" if it was introduced in OpenFlow 1.3
   *     and first supported by Open vSwitch in version 1.10).
   *
   *     Some fields have more than one OXM field assignment.  For example,
   *     actset_output has an experimenter OXM assignment in OpenFlow 1.3 and a
   *     standard OXM assignment in OpenFlow 1.5.  In such a case, specify both,
   *     separated by commas.
   *
   *     OVS uses the start of the OXM field name to determine the correct OXM
   *     class.  To support a new OXM class, edit the mapping table in
   *     build-aux/extract-ofp-fields.
   *
   *     If the field does not have an OXM field assignment, specify "none".
   *
   * The following key-value pairs are optional.  Open vSwitch already supports
   * all the fields to which they apply, so new fields should probably not
   * include these pairs:
   *
   *   OF1.0:
   *
   *     Specify this as "exact match" if OpenFlow 1.0 can match or wildcard the
   *     entire field, or as "CIDR mask" if OpenFlow 1.0 can match any CIDR
   *     prefix of the field.  (OpenFlow 1.0 did not support bitwise matching.)
   *     Omit, if OpenFlow 1.0 did not support this field.
   *
   *   OF1.1:
   *
   *     Specify this as "exact match" if OpenFlow 1.1 can match or wildcard the
   *     entire field, or as "bitwise" if OpenFlow 1.1 can match any subset of
   *     bits in the field.  Omit, if OpenFlow 1.1 did not support this field.
   *
   * The following key-value pair is optional:
   *
   *   Prefix lookup member:
   *
   *     If this field makes sense for use with classifier_set_prefix_fields(),
   *     specify the name of the "struct flow" member that corresponds to the
   *     field.
   *
   * Finally, a few "register" fields have very similar names and purposes,
   * e.g. MFF_REG0 through MFF_REG7.  For these, the comments may be merged
   * together using <N> as a metasyntactic variable for the numeric suffix.
   * Lines in the comment that are specific to one of the particular fields by
   * writing, e.g. <1>, to consider that line only for e.g. MFF_REG1.
   */
  
  enum OVS_PACKED_ENUM mf_field_id {
  /* ## -------- ## */
  /* ## Metadata ## */
  /* ## -------- ## */
  
      /* "dp_hash".
       *
       * Flow hash computed in the datapath.  Internal use only, not programmable
       * from controller.
       *
       * The OXM code point for this is an attempt to test OXM experimenter
       * support, which is otherwise difficult to test due to the dearth of use
       * out in the wild.  Because controllers can't add flows that match on
       * dp_hash, this doesn't commit OVS to supporting this OXM experimenter
       * code point in the future.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read-only.
       * NXM: NXM_NX_DP_HASH(35) since v2.2.
       * OXM: NXOXM_ET_DP_HASH(0) since OF1.5 and v2.4.
       */
      MFF_DP_HASH,
  
      /* "recirc_id".
       *
       * ID for recirculation.  The value 0 is reserved for initially received
       * packets.  Internal use only, not programmable from controller.
       *
       * Type: be32.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: none.
       * Access: read-only.
       * NXM: NXM_NX_RECIRC_ID(36) since v2.2.
       * OXM: none.
       */
      MFF_RECIRC_ID,
  
      /* "tun_id" (aka "tunnel_id").
       *
       * The "key" or "tunnel ID" or "VNI" in a packet received via a keyed
       * tunnel.  For protocols in which the key is shorter than 64 bits, the key
       * is stored in the low bits and the high bits are zeroed.  For non-keyed
       * tunnels and packets not received via a tunnel, the value is 0.
       *
       * Type: be64.
       * Maskable: bitwise.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_NX_TUN_ID(16) since v1.1.
       * OXM: OXM_OF_TUNNEL_ID(38) since OF1.3 and v1.10.
       * Prefix lookup member: tunnel.tun_id.
       */
      MFF_TUN_ID,
  
      /* "tun_src".
       *
       * The IPv4 source address in the outer IP header of a tunneled packet.
       *
       * For non-tunneled packets, the value is 0.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: IPv4.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_NX_TUN_IPV4_SRC(31) since v2.0.
       * OXM: none.
       * Prefix lookup member: tunnel.ip_src.
       */
      MFF_TUN_SRC,
  
      /* "tun_dst".
       *
       * The IPv4 destination address in the outer IP header of a tunneled
       * packet.
       *
       * For non-tunneled packets, the value is 0.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: IPv4.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_NX_TUN_IPV4_DST(32) since v2.0.
       * OXM: none.
       * Prefix lookup member: tunnel.ip_dst.
       */
      MFF_TUN_DST,
  
      /* "tun_flags".
       *
       * Combination of FLOW_TNL_F_* bitmapped flags that indicate properties of
       * a tunneled packet.  Internal use only, not programmable from controller.
       *
       * For non-tunneled packets, the value is 0.
       *
       * Type: be16.
       * Maskable: no.
       * Formatting: tunnel flags.
       * Prerequisites: none.
       * Access: read-only.
       * NXM: none.
       * OXM: none.
       */
      MFF_TUN_FLAGS,
  
      /* "tun_ttl".
       *
       * The TTL in the outer IP header of a tunneled packet.  Internal use only,
       * not programmable from controller.
       *
       * For non-tunneled packets, the value is 0.
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: none.
       * Access: read-only.
       * NXM: none.
       * OXM: none.
       */
      MFF_TUN_TTL,
  
      /* "tun_tos".
       *
       * The ToS value in the outer IP header of a tunneled packet.  Internal use
       * only, not programmable from controller.
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: none.
       * Access: read-only.
       * NXM: none.
       * OXM: none.
       */
      MFF_TUN_TOS,
  
      /* "metadata".
       *
       * A scratch pad value standardized in OpenFlow 1.1+.  Initially zero, at
       * the beginning of the pipeline.
       *
       * Type: be64.
       * Maskable: bitwise.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_METADATA(2) since OF1.2 and v1.8.
       * OF1.1: bitwise mask.
       */
      MFF_METADATA,
  
      /* "in_port".
       *
       * 16-bit (OpenFlow 1.0) view of the physical or virtual port on which the
       * packet was received.
       *
       * Type: be16.
       * Maskable: no.
       * Formatting: OpenFlow 1.0 port.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_OF_IN_PORT(0) since v1.1.
       * OXM: none.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_IN_PORT,
  
      /* "in_port_oxm".
       *
       * 32-bit (OpenFlow 1.1+) view of the physical or virtual port on which the
       * packet was received.
       *
       * Type: be32.
       * Maskable: no.
       * Formatting: OpenFlow 1.1+ port.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_IN_PORT(0) since OF1.2 and v1.7.
       * OF1.1: exact match.
       */
      MFF_IN_PORT_OXM,
  
      /* "actset_output".
       *
       * Type: be32.
       * Maskable: no.
       * Formatting: OpenFlow 1.1+ port.
       * Prerequisites: none.
       * Access: read-only.
       * NXM: none.
       * OXM: ONFOXM_ET_ACTSET_OUTPUT(43) since OF1.3 and v2.4,
       *      OXM_OF_ACTSET_OUTPUT(43) since OF1.5 and v2.4.
       */
      MFF_ACTSET_OUTPUT,
  
      /* "skb_priority".
       *
       * Designates the queue to which output will be directed.  The value in
       * this field is not necessarily the OpenFlow queue number; with the Linux
       * kernel switch, it instead has a pair of subfields designating the
       * "major" and "minor" numbers of a Linux kernel qdisc handle.
       *
       * This field is "semi-internal" in that it can be set with the "set_queue"
       * action but not matched or read or written other ways.
       *
       * Type: be32.
       * Maskable: no.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read-only.
       * NXM: none.
       * OXM: none.
       */
      MFF_SKB_PRIORITY,
  
      /* "pkt_mark".
       *
       * Packet metadata mark.  The mark may be passed into other system
       * components in order to facilitate interaction between subsystems.  On
       * Linux this corresponds to struct sk_buff's "skb_mark" member but the
       * exact implementation is platform-dependent.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_NX_PKT_MARK(33) since v2.0.
       * OXM: none.
       */
      MFF_PKT_MARK,
  
  #if FLOW_N_REGS == 8
      /* "reg<N>".
       *
       * Nicira extension scratch pad register with initial value 0.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_NX_REG0(0) since v1.1.        <0>
       * NXM: NXM_NX_REG1(1) since v1.1.        <1>
       * NXM: NXM_NX_REG2(2) since v1.1.        <2>
       * NXM: NXM_NX_REG3(3) since v1.1.        <3>
       * NXM: NXM_NX_REG4(4) since v1.3.        <4>
       * NXM: NXM_NX_REG5(5) since v1.7.        <5>
       * NXM: NXM_NX_REG6(6) since v1.7.        <6>
       * NXM: NXM_NX_REG7(7) since v1.7.        <7>
       * OXM: none.
       */
      MFF_REG0,
      MFF_REG1,
      MFF_REG2,
      MFF_REG3,
      MFF_REG4,
      MFF_REG5,
      MFF_REG6,
      MFF_REG7,
  #else
  #error "Need to update MFF_REG* to match FLOW_N_REGS"
  #endif
  
  #if FLOW_N_XREGS == 4
      /* "xreg<N>".
       *
       * OpenFlow 1.5 (draft) ``extended register".  Each extended register
       * overlays two of the Nicira extension 32-bit registers: xreg0 overlays
       * reg0 and reg1, with reg0 supplying the most-significant bits of xreg0
       * and reg1 the least-significant.  xreg1 similarly overlays reg2 and reg3,
       * and so on.
       *
       * These registers were introduced in OpenFlow 1.5, but EXT-244 in the ONF
       * JIRA also publishes them as a (draft) OpenFlow extension to OpenFlow
       * 1.3.
       *
       * Type: be64.
       * Maskable: bitwise.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_PKT_REG<N>(<N>) since OF1.3 and v2.4.
       */
      MFF_XREG0,
      MFF_XREG1,
      MFF_XREG2,
      MFF_XREG3,
  #else
  #error "Need to update MFF_REG* to match FLOW_N_XREGS"
  #endif
  
  /* ## -------- ## */
  /* ## Ethernet ## */
  /* ## -------- ## */
  
      /* "eth_src" (aka "dl_src").
       *
       * Source address in Ethernet header.
       *
       * This field was not maskable before Open vSwitch 1.8.
       *
       * Type: MAC.
       * Maskable: bitwise.
       * Formatting: Ethernet.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_OF_ETH_SRC(2) since v1.1.
       * OXM: OXM_OF_ETH_SRC(4) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: bitwise mask.
       */
      MFF_ETH_SRC,
  
      /* "eth_dst" (aka "dl_dst").
       *
       * Destination address in Ethernet header.
       *
       * Before Open vSwitch 1.8, the allowed masks were restricted to
       * 00:00:00:00:00:00, fe:ff:ff:ff:ff:ff, 01:00:00:00:00:00,
       * ff:ff:ff:ff:ff:ff.
       *
       * Type: MAC.
       * Maskable: bitwise.
       * Formatting: Ethernet.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_OF_ETH_DST(1) since v1.1.
       * OXM: OXM_OF_ETH_DST(3) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: bitwise mask.
       */
      MFF_ETH_DST,
  
      /* "eth_type" (aka "dl_type").
       *
       * Packet's Ethernet type.
       *
       * For an Ethernet II packet this is taken from the Ethernet header.  For
       * an 802.2 LLC+SNAP header with OUI 00-00-00 this is taken from the SNAP
       * header.  A packet that has neither format has value 0x05ff
       * (OFP_DL_TYPE_NOT_ETH_TYPE).
       *
       * For a packet with an 802.1Q header, this is the type of the encapsulated
       * frame.
       *
       * Type: be16.
       * Maskable: no.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read-only.
       * NXM: NXM_OF_ETH_TYPE(3) since v1.1.
       * OXM: OXM_OF_ETH_TYPE(5) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_ETH_TYPE,
  
  /* ## ---- ## */
  /* ## VLAN ## */
  /* ## ---- ## */
  
  /* It looks odd for vlan_tci, vlan_vid, and vlan_pcp to say that they are
   * supported in OF1.0 and OF1.1, since the detailed semantics of these fields
   * only apply to NXM or OXM.  They are marked as supported for exact matches in
   * OF1.0 and OF1.1 because exact matches on those fields can be successfully
   * translated into the OF1.0 and OF1.1 flow formats. */
  
      /* "vlan_tci".
       *
       * 802.1Q TCI.
       *
       * For a packet with an 802.1Q header, this is the Tag Control Information
       * (TCI) field, with the CFI bit forced to 1.  For a packet with no 802.1Q
       * header, this has value 0.
       *
       * This field can be used in various ways:
       *
       *   - If it is not constrained at all, the nx_match matches packets
       *     without an 802.1Q header or with an 802.1Q header that has any TCI
       *     value.
       *
       *   - Testing for an exact match with 0 matches only packets without an
       *     802.1Q header.
       *
       *   - Testing for an exact match with a TCI value with CFI=1 matches
       *     packets that have an 802.1Q header with a specified VID and PCP.
       *
       *   - Testing for an exact match with a nonzero TCI value with CFI=0 does
       *     not make sense.  The switch may reject this combination.
       *
       *   - Testing with a specific VID and CFI=1, with nxm_mask=0x1fff, matches
       *     packets that have an 802.1Q header with that VID (and any PCP).
       *
       *   - Testing with a specific PCP and CFI=1, with nxm_mask=0xf000, matches
       *     packets that have an 802.1Q header with that PCP (and any VID).
       *
       *   - Testing with nxm_value=0, nxm_mask=0x0fff matches packets with no
       *     802.1Q header or with an 802.1Q header with a VID of 0.
       *
       *   - Testing with nxm_value=0, nxm_mask=0xe000 matches packets with no
       *     802.1Q header or with an 802.1Q header with a PCP of 0.
       *
       *   - Testing with nxm_value=0, nxm_mask=0xefff matches packets with no
       *     802.1Q header or with an 802.1Q header with both VID and PCP of 0.
       *
       * Type: be16.
       * Maskable: bitwise.
       * Formatting: hexadecimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_OF_VLAN_TCI(4) since v1.1.
       * OXM: none.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_VLAN_TCI,
  
      /* "dl_vlan" (OpenFlow 1.0).
       *
       * VLAN ID field.  Zero if no 802.1Q header is present.
       *
       * Type: be16 (low 12 bits).
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: none.
       * OXM: none.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_DL_VLAN,
  
      /* "vlan_vid" (OpenFlow 1.2+).
       *
       * If an 802.1Q header is present, this field's value is 0x1000
       * bitwise-or'd with the VLAN ID.  If no 802.1Q is present, this field's
       * value is 0.
       *
       * Type: be16 (low 12 bits).
       * Maskable: bitwise.
       * Formatting: decimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_VLAN_VID(6) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_VLAN_VID,
  
      /* "dl_vlan_pcp" (OpenFlow 1.0).
       *
       * VLAN priority (PCP) field.  Zero if no 802.1Q header is present.
       *
       * Type: u8 (low 3 bits).
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: none.
       * OXM: none.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_DL_VLAN_PCP,
  
      /* "vlan_pcp" (OpenFlow 1.2+).
       *
       * VLAN priority (PCP) field.  Zero if no 802.1Q header is present.
       *
       * Type: u8 (low 3 bits).
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: VLAN VID.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_VLAN_PCP(7) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_VLAN_PCP,
  
  /* ## ---- ## */
  /* ## MPLS ## */
  /* ## ---- ## */
  
      /* "mpls_label".
       *
       * The outermost MPLS label, or 0 if no MPLS labels are present.
       *
       * Type: be32 (low 20 bits).
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: MPLS.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_MPLS_LABEL(34) since OF1.2 and v1.11.
       * OF1.1: exact match.
       */
      MFF_MPLS_LABEL,
  
      /* "mpls_tc".
       *
       * The outermost MPLS label's traffic control (TC) field, or 0 if no MPLS
       * labels are present.
       *
       * Type: u8 (low 3 bits).
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: MPLS.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_MPLS_TC(35) since OF1.2 and v1.11.
       * OF1.1: exact match.
       */
      MFF_MPLS_TC,
  
      /* "mpls_bos".
       *
       * The outermost MPLS label's bottom of stack (BoS) field, or 0 if no MPLS
       * labels are present.
       *
       * Type: u8 (low 1 bits).
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: MPLS.
       * Access: read-only.
       * NXM: none.
       * OXM: OXM_OF_MPLS_BOS(36) since OF1.3 and v1.11.
       */
      MFF_MPLS_BOS,
  
  /* ## ---- ## */
  /* ## IPv4 ## */
  /* ## ---- ## */
  
  /* Update mf_is_l3_or_higher() if MFF_IPV4_SRC is no longer the first element
   * for a field of layer 3 or higher */
  
      /* "ip_src" (aka "nw_src").
       *
       * The source address in the IPv4 header.
       *
       * Before Open vSwitch 1.8, only CIDR masks were supported.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: IPv4.
       * Prerequisites: IPv4.
       * Access: read/write.
       * NXM: NXM_OF_IP_SRC(7) since v1.1.
       * OXM: OXM_OF_IPV4_SRC(11) since OF1.2 and v1.7.
       * OF1.0: CIDR mask.
       * OF1.1: bitwise mask.
       * Prefix lookup member: nw_src.
       */
      MFF_IPV4_SRC,
  
      /* "ip_dst" (aka "nw_dst").
       *
       * The destination address in the IPv4 header.
       *
       * Before Open vSwitch 1.8, only CIDR masks were supported.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: IPv4.
       * Prerequisites: IPv4.
       * Access: read/write.
       * NXM: NXM_OF_IP_DST(8) since v1.1.
       * OXM: OXM_OF_IPV4_DST(12) since OF1.2 and v1.7.
       * OF1.0: CIDR mask.
       * OF1.1: bitwise mask.
       * Prefix lookup member: nw_dst.
       */
      MFF_IPV4_DST,
  
  /* ## ---- ## */
  /* ## IPv6 ## */
  /* ## ---- ## */
  
      /* "ipv6_src".
       *
       * The source address in the IPv6 header.
       *
       * Type: IPv6.
       * Maskable: bitwise.
       * Formatting: IPv6.
       * Prerequisites: IPv6.
       * Access: read/write.
       * NXM: NXM_NX_IPV6_SRC(19) since v1.1.
       * OXM: OXM_OF_IPV6_SRC(26) since OF1.2 and v1.1.
       * Prefix lookup member: ipv6_src.
       */
      MFF_IPV6_SRC,
  
      /* "ipv6_dst".
       *
       * The destination address in the IPv6 header.
       *
       * Type: IPv6.
       * Maskable: bitwise.
       * Formatting: IPv6.
       * Prerequisites: IPv6.
       * Access: read/write.
       * NXM: NXM_NX_IPV6_DST(20) since v1.1.
       * OXM: OXM_OF_IPV6_DST(27) since OF1.2 and v1.1.
       * Prefix lookup member: ipv6_dst.
       */
      MFF_IPV6_DST,
  
      /* "ipv6_label".
       *
       * The flow label in the IPv6 header.
       *
       * Type: be32 (low 20 bits).
       * Maskable: bitwise.
       * Formatting: hexadecimal.
       * Prerequisites: IPv6.
       * Access: read-only.
       * NXM: NXM_NX_IPV6_LABEL(27) since v1.4.
       * OXM: OXM_OF_IPV6_FLABEL(28) since OF1.2 and v1.7.
       */
      MFF_IPV6_LABEL,
  
  /* ## ----------------------- ## */
  /* ## IPv4/IPv6 common fields ## */
  /* ## ----------------------- ## */
  
      /* "nw_proto" (aka "ip_proto").
       *
       * The "protocol" byte in the IPv4 or IPv6 header.
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: IPv4/IPv6.
       * Access: read-only.
       * NXM: NXM_OF_IP_PROTO(6) since v1.1.
       * OXM: OXM_OF_IP_PROTO(10) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_IP_PROTO,
  
  /* Both views of the DSCP below are marked as supported in all of the versions
   * of OpenFlow because a match on either view can be successfully translated
   * into every OpenFlow flow format. */
  
      /* "nw_tos" (OpenFlow 1.0/1.1).
       *
       * The DSCP byte in the IPv4 header or the traffic class byte from the IPv6
       * header, with the ECN bits forced to 0.  (That is, bits 2-7 contain the
       * type of service and bits 0-1 are zero.)
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: IPv4/IPv6.
       * Access: read/write.
       * NXM: NXM_OF_IP_TOS(5) since v1.1.
       * OXM: none.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_IP_DSCP,
  
      /* "ip_dscp" (OpenFlow 1.2+).
       *
       * The DSCP byte in the IPv4 header or the traffic class byte from the IPv6
       * header, shifted right 2 bits.  (That is, bits 0-5 contain the type of
       * service and bits 6-7 are zero.)
       *
       * Type: u8 (low 6 bits).
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: IPv4/IPv6.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_IP_DSCP(8) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_IP_DSCP_SHIFTED,
  
      /* "nw_ecn" (aka "ip_ecn").
       *
       * The ECN bits in the IPv4 or IPv6 header.
       *
       * Type: u8 (low 2 bits).
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: IPv4/IPv6.
       * Access: read/write.
       * NXM: NXM_NX_IP_ECN(28) since v1.4.
       * OXM: OXM_OF_IP_ECN(9) since OF1.2 and v1.7.
       */
      MFF_IP_ECN,
  
      /* "nw_ttl".
       *
       * The time-to-live (TTL) in the IPv4 header or hop limit in the IPv6
       * header.
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: IPv4/IPv6.
       * Access: read/write.
       * NXM: NXM_NX_IP_TTL(29) since v1.4.
       * OXM: none.
       */
      MFF_IP_TTL,
  
      /* "ip_frag".
       *
       * IP fragment information.
       *
       * This field has three possible values:
       *
       *   - A packet that is not an IP fragment has value 0.
       *
       *   - A packet that is an IP fragment with offset 0 (the first fragment)
       *     has bit 0 set and thus value 1.
       *
       *   - A packet that is an IP fragment with nonzero offset has bits 0 and 1
       *     set and thus value 3.
       *
       * NX_IP_FRAG_ANY and NX_IP_FRAG_LATER are declared to symbolically
       * represent the meanings of bits 0 and 1.
       *
       * The switch may reject matches against values that can never appear.
       *
       * It is important to understand how this field interacts with the OpenFlow
       * IP fragment handling mode:
       *
       *   - In OFPC_FRAG_DROP mode, the OpenFlow switch drops all IP fragments
       *     before they reach the flow table, so every packet that is available
       *     for matching will have value 0 in this field.
       *
       *   - Open vSwitch does not implement OFPC_FRAG_REASM mode, but if it did
       *     then IP fragments would be reassembled before they reached the flow
       *     table and again every packet available for matching would always
       *     have value 0.
       *
       *   - In OFPC_FRAG_NORMAL mode, all three values are possible, but
       *     OpenFlow 1.0 says that fragments' transport ports are always 0, even
       *     for the first fragment, so this does not provide much extra
       *     information.
       *
       *   - In OFPC_FRAG_NX_MATCH mode, all three values are possible.  For
       *     fragments with offset 0, Open vSwitch makes L4 header information
       *     available.
       *
       * Type: u8 (low 2 bits).
       * Maskable: bitwise.
       * Formatting: frag.
       * Prerequisites: IPv4/IPv6.
       * Access: read-only.
       * NXM: NXM_NX_IP_FRAG(26) since v1.3.
       * OXM: none.
       */
      MFF_IP_FRAG,
  
  /* ## --- ## */
  /* ## ARP ## */
  /* ## --- ## */
  
      /* "arp_op".
       *
       * ARP opcode.
       *
       * For an Ethernet+IP ARP packet, the opcode in the ARP header.  Always 0
       * otherwise.  Only ARP opcodes between 1 and 255 should be specified for
       * matching.
       *
       * Type: be16.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: ARP.
       * Access: read/write.
       * NXM: NXM_OF_ARP_OP(15) since v1.1.
       * OXM: OXM_OF_ARP_OP(21) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_ARP_OP,
  
      /* "arp_spa".
       *
       * For an Ethernet+IP ARP packet, the source protocol (IPv4) address in the
       * ARP header.  Always 0 otherwise.
       *
       * Before Open vSwitch 1.8, only CIDR masks were supported.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: IPv4.
       * Prerequisites: ARP.
       * Access: read/write.
       * NXM: NXM_OF_ARP_SPA(16) since v1.1.
       * OXM: OXM_OF_ARP_SPA(22) since OF1.2 and v1.7.
       * OF1.0: CIDR mask.
       * OF1.1: bitwise mask.
       */
      MFF_ARP_SPA,
  
      /* "arp_tpa".
       *
       * For an Ethernet+IP ARP packet, the target protocol (IPv4) address in the
       * ARP header.  Always 0 otherwise.
       *
       * Before Open vSwitch 1.8, only CIDR masks were supported.
       *
       * Type: be32.
       * Maskable: bitwise.
       * Formatting: IPv4.
       * Prerequisites: ARP.
       * Access: read/write.
       * NXM: NXM_OF_ARP_TPA(17) since v1.1.
       * OXM: OXM_OF_ARP_TPA(23) since OF1.2 and v1.7.
       * OF1.0: CIDR mask.
       * OF1.1: bitwise mask.
       */
      MFF_ARP_TPA,
  
      /* "arp_sha".
       *
       * For an Ethernet+IP ARP packet, the source hardware (Ethernet) address in
       * the ARP header.  Always 0 otherwise.
       *
       * Type: MAC.
       * Maskable: bitwise.
       * Formatting: Ethernet.
       * Prerequisites: ARP.
       * Access: read/write.
       * NXM: NXM_NX_ARP_SHA(17) since v1.1.
       * OXM: OXM_OF_ARP_SHA(24) since OF1.2 and v1.7.
       */
      MFF_ARP_SHA,
  
      /* "arp_tha".
       *
       * For an Ethernet+IP ARP packet, the target hardware (Ethernet) address in
       * the ARP header.  Always 0 otherwise.
       *
       * Type: MAC.
       * Maskable: bitwise.
       * Formatting: Ethernet.
       * Prerequisites: ARP.
       * Access: read/write.
       * NXM: NXM_NX_ARP_THA(18) since v1.1.
       * OXM: OXM_OF_ARP_THA(25) since OF1.2 and v1.7.
       */
      MFF_ARP_THA,
  
  /* ## --- ## */
  /* ## TCP ## */
  /* ## --- ## */
  
      /* "tcp_src" (aka "tp_src").
       *
       * TCP source port.
       *
       * Type: be16.
       * Maskable: bitwise.
       * Formatting: decimal.
       * Prerequisites: TCP.
       * Access: read/write.
       * NXM: NXM_OF_TCP_SRC(9) since v1.1.
       * OXM: OXM_OF_TCP_SRC(13) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_TCP_SRC,
  
      /* "tcp_dst" (aka "tp_dst").
       *
       * TCP destination port.
       *
       * Type: be16.
       * Maskable: bitwise.
       * Formatting: decimal.
       * Prerequisites: TCP.
       * Access: read/write.
       * NXM: NXM_OF_TCP_DST(10) since v1.1.
       * OXM: OXM_OF_TCP_DST(14) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_TCP_DST,
  
      /* "tcp_flags".
       *
       * Flags in the TCP header.
       *
       * TCP currently defines 9 flag bits, and additional 3 bits are reserved
       * (must be transmitted as zero).  See RFCs 793, 3168, and 3540.
       *
       * Type: be16 (low 12 bits).
       * Maskable: bitwise.
       * Formatting: TCP flags.
       * Prerequisites: TCP.
       * Access: read-only.
       * NXM: NXM_NX_TCP_FLAGS(34) since v2.1.
       * OXM: ONFOXM_ET_TCP_FLAGS(42) since OF1.3 and v2.4,
       *      OXM_OF_TCP_FLAGS(42) since OF1.5 and v2.3.
       */
      MFF_TCP_FLAGS,
  
  /* ## --- ## */
  /* ## UDP ## */
  /* ## --- ## */
  
      /* "udp_src".
       *
       * UDP source port.
       *
       * Type: be16.
       * Maskable: bitwise.
       * Formatting: decimal.
       * Prerequisites: UDP.
       * Access: read/write.
       * NXM: NXM_OF_UDP_SRC(11) since v1.1.
       * OXM: OXM_OF_UDP_SRC(15) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_UDP_SRC,
  
      /* "udp_dst".
       *
       * UDP destination port
       *
       * Type: be16.
       * Maskable: bitwise.
       * Formatting: decimal.
       * Prerequisites: UDP.
       * Access: read/write.
       * NXM: NXM_OF_UDP_DST(12) since v1.1.
       * OXM: OXM_OF_UDP_DST(16) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_UDP_DST,
  
  /* ## ---- ## */
  /* ## SCTP ## */
  /* ## ---- ## */
  
      /* "sctp_src".
       *
       * SCTP source port.
       *
       * Type: be16.
       * Maskable: bitwise.
       * Formatting: decimal.
       * Prerequisites: SCTP.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_SCTP_SRC(17) since OF1.2 and v2.0.
       * OF1.1: exact match.
       */
      MFF_SCTP_SRC,
  
      /* "sctp_dst".
       *
       * SCTP destination port.
       *
       * Type: be16.
       * Maskable: bitwise.
       * Formatting: decimal.
       * Prerequisites: SCTP.
       * Access: read/write.
       * NXM: none.
       * OXM: OXM_OF_SCTP_DST(18) since OF1.2 and v2.0.
       * OF1.1: exact match.
       */
      MFF_SCTP_DST,
  
  /* ## ---- ## */
  /* ## ICMP ## */
  /* ## ---- ## */
  
      /* "icmp_type".
       *
       * ICMPv4 type.
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: ICMPv4.
       * Access: read-only.
       * NXM: NXM_OF_ICMP_TYPE(13) since v1.1.
       * OXM: OXM_OF_ICMPV4_TYPE(19) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_ICMPV4_TYPE,
  
      /* "icmp_code".
       *
       * ICMPv4 code.
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: ICMPv4.
       * Access: read-only.
       * NXM: NXM_OF_ICMP_CODE(14) since v1.1.
       * OXM: OXM_OF_ICMPV4_CODE(20) since OF1.2 and v1.7.
       * OF1.0: exact match.
       * OF1.1: exact match.
       */
      MFF_ICMPV4_CODE,
  
      /* "icmpv6_type".
       *
       * ICMPv6 type.
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: ICMPv6.
       * Access: read-only.
       * NXM: NXM_NX_ICMPV6_TYPE(21) since v1.1.
       * OXM: OXM_OF_ICMPV6_TYPE(29) since OF1.2 and v1.7.
       */
      MFF_ICMPV6_TYPE,
  
      /* "icmpv6_code".
       *
       * ICMPv6 code.
       *
       * Type: u8.
       * Maskable: no.
       * Formatting: decimal.
       * Prerequisites: ICMPv6.
       * Access: read-only.
       * NXM: NXM_NX_ICMPV6_CODE(22) since v1.1.
       * OXM: OXM_OF_ICMPV6_CODE(30) since OF1.2 and v1.7.
       */
      MFF_ICMPV6_CODE,
  
  /* ## ------------------------- ## */
  /* ## ICMPv6 Neighbor Discovery ## */
  /* ## ------------------------- ## */
  
      /* "nd_target".
       *
       * The target address in an IPv6 Neighbor Discovery message.
       *
       * Before Open vSwitch 1.8, only CIDR masks were supported.
       *
       * Type: IPv6.
       * Maskable: bitwise.
       * Formatting: IPv6.
       * Prerequisites: ND.
       * Access: read-only.
       * NXM: NXM_NX_ND_TARGET(23) since v1.1.
       * OXM: OXM_OF_IPV6_ND_TARGET(31) since OF1.2 and v1.7.
       */
      MFF_ND_TARGET,
  
      /* "nd_sll".
       *
       * The source link layer address in an IPv6 Neighbor Discovery message.
       *
       * Type: MAC.
       * Maskable: bitwise.
       * Formatting: Ethernet.
       * Prerequisites: ND solicit.
       * Access: read-only.
       * NXM: NXM_NX_ND_SLL(24) since v1.1.
       * OXM: OXM_OF_IPV6_ND_SLL(32) since OF1.2 and v1.7.
       */
      MFF_ND_SLL,
  
      /* "nd_tll".
       *
       * The target link layer address in an IPv6 Neighbor Discovery message.
       *
       * Type: MAC.
       * Maskable: bitwise.
       * Formatting: Ethernet.
       * Prerequisites: ND advert.
       * Access: read-only.
       * NXM: NXM_NX_ND_TLL(25) since v1.1.
       * OXM: OXM_OF_IPV6_ND_TLL(33) since OF1.2 and v1.7.
       */
      MFF_ND_TLL,
  
      /*
       * "tun_metadata".
       *
       * Encap metadata for tunnels.
       *
       * Each NXM can carry upto 255 bytes of encap metadata when not masked or
       * upto 127 bytes of encap metadata followed by equal length mask when
       * masked.
       *
       * Type: bytestring.
       * Maskable: bitwise.
       * Formatting: tun_metadata.
       * Prerequisites: none.
       * Access: read/write.
       * NXM: NXM_NX_TUN_METADATA(37) since v2.0.
       * OXM: none.
       * Prefix lookup member: tunnel.metadata.
       *
       */
      MFF_TUN_METADATA,
  
      MFF_N_IDS
  };
  
  /* A set of mf_field_ids. */
  struct mf_bitmap {
      unsigned long bm[BITMAP_N_LONGS(MFF_N_IDS)];
  };
  #define MF_BITMAP_INITIALIZER { { [0] = 0 } }
  
  /* Use this macro as CASE_MFF_REGS: in a switch statement to choose all of the
   * MFF_REGn cases. */
  #if FLOW_N_REGS == 8
  #define CASE_MFF_REGS                                           \
      case MFF_REG0: case MFF_REG1: case MFF_REG2: case MFF_REG3: \
      case MFF_REG4: case MFF_REG5: case MFF_REG6: case MFF_REG7
  #else
  #error "Need to update CASE_MFF_REGS to match FLOW_N_REGS"
  #endif
  
  /* Use this macro as CASE_MFF_XREGS: in a switch statement to choose all of the
   * MFF_REGn cases. */
  #if FLOW_N_XREGS == 4
  #define CASE_MFF_XREGS                                              \
      case MFF_XREG0: case MFF_XREG1: case MFF_XREG2: case MFF_XREG3
  #else
  #error "Need to update CASE_MFF_XREGS to match FLOW_N_XREGS"
  #endif
  
  /* Prerequisites for matching a field.
   *
   * A field may only be matched if the correct lower-level protocols are also
   * matched.  For example, the TCP port may be matched only if the Ethernet type
   * matches ETH_TYPE_IP and the IP protocol matches IPPROTO_TCP. */
  enum OVS_PACKED_ENUM mf_prereqs {
      MFP_NONE,
  
      /* L2 requirements. */
      MFP_ARP,
      MFP_VLAN_VID,
      MFP_IPV4,
      MFP_IPV6,
      MFP_IP_ANY,
  
      /* L2.5 requirements. */
      MFP_MPLS,
  
      /* L2+L3 requirements. */
      MFP_TCP,                    /* On IPv4 or IPv6. */
      MFP_UDP,                    /* On IPv4 or IPv6. */
      MFP_SCTP,                   /* On IPv4 or IPv6. */
      MFP_ICMPV4,
      MFP_ICMPV6,
  
      /* L2+L3+L4 requirements. */
      MFP_ND,
      MFP_ND_SOLICIT,
      MFP_ND_ADVERT
  };
  
  /* Forms of partial-field masking allowed for a field.
   *
   * Every field may be masked as a whole. */
  enum OVS_PACKED_ENUM mf_maskable {
      MFM_NONE,                   /* No sub-field masking. */
      MFM_FULLY,                  /* Every bit is individually maskable. */
  };
  
  /* How to format or parse a field's value. */
  enum OVS_PACKED_ENUM mf_string {
      /* Integer formats.
       *
       * The particular MFS_* constant sets the output format.  On input, either
       * decimal or hexadecimal (prefixed with 0x) is accepted. */
      MFS_DECIMAL,
      MFS_HEXADECIMAL,
  
      /* Other formats. */
      MFS_ETHERNET,
      MFS_IPV4,
      MFS_IPV6,
      MFS_OFP_PORT,               /* 16-bit OpenFlow 1.0 port number or name. */
      MFS_OFP_PORT_OXM,           /* 32-bit OpenFlow 1.1+ port number or name. */
      MFS_FRAG,                   /* no, yes, first, later, not_later */
      MFS_TNL_FLAGS,              /* FLOW_TNL_F_* flags */
      MFS_TCP_FLAGS,              /* TCP_* flags */
      MFS_TUN_METADATA,           /* tunnel metadata upto 255 bytes */
  };
  
  struct mf_field {
      /* Identification. */
      enum mf_field_id id;        /* MFF_*. */
      const char *name;           /* Name of this field, e.g. "eth_type". */
      const char *extra_name;     /* Alternate name, e.g. "dl_type", or NULL. */
  
      /* Size.
       *
       * Most fields have n_bytes * 8 == n_bits.  There are a few exceptions:
       *
       *     - "dl_vlan" is 2 bytes but only 12 bits.
       *     - "dl_vlan_pcp" is 1 byte but only 3 bits.
       *     - "is_frag" is 1 byte but only 2 bits.
       *     - "ipv6_label" is 4 bytes but only 20 bits.
       *     - "mpls_label" is 4 bytes but only 20 bits.
       *     - "mpls_tc"    is 1 byte but only 3 bits.
       *     - "mpls_bos"   is 1 byte but only 1 bit.
       */
      unsigned int n_bytes;       /* Width of the field in bytes. */
      unsigned int n_bits;        /* Number of significant bits in field. */
  
      /* Properties. */
      enum mf_maskable maskable;
      enum mf_string string;
      enum mf_prereqs prereqs;
      bool writable;              /* May be written by actions? */
  
      /* Usable protocols.
       *
       * NXM and OXM are extensible, allowing later extensions to be sent in
       * earlier protocol versions, so this does not necessarily correspond to
       * the OpenFlow protocol version the field was introduced in.
       * Also, some field types are tranparently mapped to each other via the
       * struct flow (like vlan and dscp/tos fields), so each variant supports
       * all protocols.
       *
       * These are combinations of OFPUTIL_P_*.  (They are not declared as type
       * enum ofputil_protocol because that would give meta-flow.h and ofp-util.h
       * a circular dependency.) */
      uint32_t usable_protocols_exact;   /* Matching or setting whole field. */
      uint32_t usable_protocols_cidr;    /* Matching a CIDR mask in field. */
      uint32_t usable_protocols_bitwise; /* Matching arbitrary bits in field. */
  
      int flow_be32ofs;  /* Field's be32 offset in "struct flow", if prefix tree
                          * lookup is supported for the field, or -1. */
  };
  
  /* The representation of a field's value. */
  union mf_value {
      struct in6_addr ipv6;
      uint8_t mac[ETH_ADDR_LEN];
      ovs_be64 be64;
      ovs_be32 be32;
      ovs_be16 be16;
      uint8_t u8;
      uint8_t tun_metadata[TUN_METADATA_LEN];
  };
  BUILD_ASSERT_DECL(sizeof(union mf_value) == TUN_METADATA_LEN);
  BUILD_ASSERT_DECL(TUN_METADATA_LEN >= 16);
  
  /* Part of a field. */
  struct mf_subfield {
      const struct mf_field *field;
      unsigned int ofs;           /* Bit offset. */
      unsigned int n_bits;        /* Number of bits. */
  };
  
  /* Data for some part of an mf_field.
   *
   * The data is stored "right-justified".  For example, if "union mf_subvalue
   * value" contains NXM_OF_VLAN_TCI[0..11], then one could access the
   * corresponding data in value.be16[7] as the bits in the mask htons(0xfff). */
  union mf_subvalue {
      uint8_t u8[TUN_METADATA_LEN];
      ovs_be16 be16[TUN_METADATA_LEN >> 1];
      ovs_be32 be32[TUN_METADATA_LEN >> 2];
      ovs_be64 be64[TUN_METADATA_LEN >> 3];
  };
  BUILD_ASSERT_DECL(sizeof(union mf_value) == sizeof (union mf_subvalue));
  BUILD_ASSERT_DECL(TUN_METADATA_LEN % 8 == 0);
  
  /* Finding mf_fields. */
  const struct mf_field *mf_from_name(const char *name);
  
  static inline const struct mf_field *
  mf_from_id(enum mf_field_id id)
  {
      extern const struct mf_field mf_fields[MFF_N_IDS];
      ovs_assert((unsigned int) id < MFF_N_IDS);
      return &mf_fields[id];
  }
  
  /* Inspecting wildcarded bits. */
  bool mf_is_all_wild(const struct mf_field *, const struct flow_wildcards *);
  
  bool mf_is_mask_valid(const struct mf_field *, const union mf_value *mask);
  void mf_get_mask(const struct mf_field *, const struct flow_wildcards *,
                   union mf_value *mask);
  
  /* Prerequisites. */
  bool mf_are_prereqs_ok(const struct mf_field *, const struct flow *);
  void mf_mask_field_and_prereqs(const struct mf_field *, struct flow *mask);
  
  static inline bool
  mf_is_l3_or_higher(const struct mf_field *mf)
  {
      return mf->id >= MFF_IPV4_SRC;
  }
  
  /* Field values. */
  bool mf_is_value_valid(const struct mf_field *, const union mf_value *value);
  
  void mf_get_value(const struct mf_field *, const struct flow *,
                    union mf_value *value);
  void mf_set_value(const struct mf_field *, const union mf_value *value,
                    struct match *, int);
  void mf_set_flow_value(const struct mf_field *, const union mf_value *value,
                         struct flow *);
  void mf_set_flow_value_masked(const struct mf_field *,
                                const union mf_value *value,
                                const union mf_value *mask,
                                struct flow *);
  bool mf_is_zero(const struct mf_field *, const struct flow *);
  void mf_mask_field(const struct mf_field *, struct flow *);
  
  void mf_get(const struct mf_field *, const struct match *,
              union mf_value *value, union mf_value *mask);
  
  /* Returns the set of usable protocols. */
  enum ofputil_protocol mf_set(const struct mf_field *,
                               const union mf_value *value,
                               const union mf_value *mask,
                               struct match *, int);
  
  void mf_set_wild(const struct mf_field *, const union mf_value *value,
                   struct match *, int);
  
  /* Subfields. */
  void mf_write_subfield_flow(const struct mf_subfield *,
                              const union mf_subvalue *, struct flow *);
  void mf_write_subfield(const struct mf_subfield *, const union mf_subvalue *,
                         struct match *);
  
  void mf_read_subfield(const struct mf_subfield *, const struct flow *,
                        union mf_subvalue *);
  uint64_t mf_get_subfield(const struct mf_subfield *, const struct flow *);
  
  
  enum ofperr mf_check_src(const struct mf_subfield *, const struct flow *);
  enum ofperr mf_check_dst(const struct mf_subfield *, const struct flow *);
  
  /* Parsing and formatting. */
  char *mf_parse(const struct mf_field *, const char *,
                 union mf_value *value, union mf_value *mask, int *);
  char *mf_parse_value(const struct mf_field *, const char *, union mf_value *,
                       int *);
  void mf_format(const struct mf_field *,
                 const union mf_value *value, const union mf_value *mask,
                 struct ds *);
  void mf_format_subvalue(const union mf_subvalue *subvalue, struct ds *s);
  
  #endif /* meta-flow.h */
  