text: /*
   * Copyright (c) 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 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.
   */
  
  #include <config.h>
  
  #include "nx-match.h"
  
  #include <netinet/icmp6.h>
  
  #include "classifier.h"
  #include "colors.h"
  #include "openvswitch/hmap.h"
  #include "openflow/nicira-ext.h"
  #include "openvswitch/dynamic-string.h"
  #include "openvswitch/meta-flow.h"
  #include "openvswitch/ofp-actions.h"
  #include "openvswitch/ofp-errors.h"
  #include "openvswitch/ofp-util.h"
  #include "openvswitch/ofpbuf.h"
  #include "openvswitch/vlog.h"
  #include "packets.h"
  #include "openvswitch/shash.h"
  #include "tun-metadata.h"
  #include "unaligned.h"
  #include "util.h"
  #include "vl-mff-map.h"
  
  VLOG_DEFINE_THIS_MODULE(nx_match);
  
  /* OXM headers.
   *
   *
   * Standard OXM/NXM
   * ================
   *
   * The header is 32 bits long.  It looks like this:
   *
   * |31                              16 15            9| 8 7                0
   * +----------------------------------+---------------+--+------------------+
   * |            oxm_class             |   oxm_field   |hm|    oxm_length    |
   * +----------------------------------+---------------+--+------------------+
   *
   * where hm stands for oxm_hasmask.  It is followed by oxm_length bytes of
   * payload.  When oxm_hasmask is 0, the payload is the value of the field
   * identified by the header; when oxm_hasmask is 1, the payload is a value for
   * the field followed by a mask of equal length.
   *
   * Internally, we represent a standard OXM header as a 64-bit integer with the
   * above information in the most-significant bits.
   *
   *
   * Experimenter OXM
   * ================
   *
   * The header is 64 bits long.  It looks like the diagram above except that a
   * 32-bit experimenter ID, which we call oxm_vendor and which identifies a
   * vendor, is inserted just before the payload.  Experimenter OXMs are
   * identified by an all-1-bits oxm_class (OFPXMC12_EXPERIMENTER).  The
   * oxm_length value *includes* the experimenter ID, so that the real payload is
   * only oxm_length - 4 bytes long.
   *
   * Internally, we represent an experimenter OXM header as a 64-bit integer with
   * the standard header in the upper 32 bits and the experimenter ID in the
   * lower 32 bits.  (It would be more convenient to swap the positions of the
   * two 32-bit words, but this would be more error-prone because experimenter
   * OXMs are very rarely used, so accidentally passing one through a 32-bit type
   * somewhere in the OVS code would be hard to find.)
   */
  
  /*
   * OXM Class IDs.
   * The high order bit differentiate reserved classes from member classes.
   * Classes 0x0000 to 0x7FFF are member classes, allocated by ONF.
   * Classes 0x8000 to 0xFFFE are reserved classes, reserved for standardisation.
   */
  enum ofp12_oxm_class {
      OFPXMC12_NXM_0          = 0x0000, /* Backward compatibility with NXM */
      OFPXMC12_NXM_1          = 0x0001, /* Backward compatibility with NXM */
      OFPXMC12_OPENFLOW_BASIC = 0x8000, /* Basic class for OpenFlow */
      OFPXMC15_PACKET_REGS    = 0x8001, /* Packet registers (pipeline fields). */
      OFPXMC12_EXPERIMENTER   = 0xffff, /* Experimenter class */
  };
  
  /* Functions for extracting raw field values from OXM/NXM headers. */
  static uint32_t nxm_vendor(uint64_t header) { return header; }
  static int nxm_class(uint64_t header) { return header >> 48; }
  static int nxm_field(uint64_t header) { return (header >> 41) & 0x7f; }
  static bool nxm_hasmask(uint64_t header) { return (header >> 40) & 1; }
  static int nxm_length(uint64_t header) { return (header >> 32) & 0xff; }
  static uint64_t nxm_no_len(uint64_t header) { return header & 0xffffff80ffffffffULL; }
  
  static bool
  is_experimenter_oxm(uint64_t header)
  {
      return nxm_class(header) == OFPXMC12_EXPERIMENTER;
  }
  
  /* The OXM header "length" field is somewhat tricky:
   *
   *     - For a standard OXM header, the length is the number of bytes of the
   *       payload, and the payload consists of just the value (and mask, if
   *       present).
   *
   *     - For an experimenter OXM header, the length is the number of bytes in
   *       the payload plus 4 (the length of the experimenter ID).  That is, the
   *       experimenter ID is included in oxm_length.
   *
   * This function returns the length of the experimenter ID field in 'header'.
   * That is, for an experimenter OXM (when an experimenter ID is present), it
   * returns 4, and for a standard OXM (when no experimenter ID is present), it
   * returns 0. */
  static int
  nxm_experimenter_len(uint64_t header)
  {
      return is_experimenter_oxm(header) ? 4 : 0;
  }
  
  /* Returns the number of bytes that follow the header for an NXM/OXM entry
   * with the given 'header'. */
  static int
  nxm_payload_len(uint64_t header)
  {
      return nxm_length(header) - nxm_experimenter_len(header);
  }
  
  /* Returns the number of bytes in the header for an NXM/OXM entry with the
   * given 'header'. */
  static int
  nxm_header_len(uint64_t header)
  {
      return 4 + nxm_experimenter_len(header);
  }
  
  #define NXM_HEADER(VENDOR, CLASS, FIELD, HASMASK, LENGTH)       \
      (((uint64_t) (CLASS) << 48) |                               \
       ((uint64_t) (FIELD) << 41) |                               \
       ((uint64_t) (HASMASK) << 40) |                             \
       ((uint64_t) (LENGTH) << 32) |                              \
       (VENDOR))
  
  #define NXM_HEADER_FMT "%#"PRIx32":%d:%d:%d:%d"
  #define NXM_HEADER_ARGS(HEADER)                                 \
      nxm_vendor(HEADER), nxm_class(HEADER), nxm_field(HEADER),   \
      nxm_hasmask(HEADER), nxm_length(HEADER)
  
  /* Functions for turning the "hasmask" bit on or off.  (This also requires
   * adjusting the length.) */
  static uint64_t
  nxm_make_exact_header(uint64_t header)
  {
      int new_len = nxm_payload_len(header) / 2 + nxm_experimenter_len(header);
      return NXM_HEADER(nxm_vendor(header), nxm_class(header),
                        nxm_field(header), 0, new_len);
  }
  static uint64_t
  nxm_make_wild_header(uint64_t header)
  {
      int new_len = nxm_payload_len(header) * 2 + nxm_experimenter_len(header);
      return NXM_HEADER(nxm_vendor(header), nxm_class(header),
                        nxm_field(header), 1, new_len);
  }
  
  /* Flow cookie.
   *
   * This may be used to gain the OpenFlow 1.1-like ability to restrict
   * certain NXM-based Flow Mod and Flow Stats Request messages to flows
   * with specific cookies.  See the "nx_flow_mod" and "nx_flow_stats_request"
   * structure definitions for more details.  This match is otherwise not
   * allowed. */
  #define NXM_NX_COOKIE     NXM_HEADER  (0, 0x0001, 30, 0, 8)
  #define NXM_NX_COOKIE_W   nxm_make_wild_header(NXM_NX_COOKIE)
  
  struct nxm_field {
      uint64_t header;
      enum ofp_version version;
      const char *name;           /* e.g. "NXM_OF_IN_PORT". */
  
      enum mf_field_id id;
  };
  
  static const struct nxm_field *nxm_field_by_header(uint64_t header);
  static const struct nxm_field *nxm_field_by_name(const char *name, size_t len);
  static const struct nxm_field *nxm_field_by_mf_id(enum mf_field_id,
                                                    enum ofp_version);
  
  static void nx_put_header__(struct ofpbuf *, uint64_t header, bool masked);
  static void nx_put_header_len(struct ofpbuf *, enum mf_field_id field,
                                enum ofp_version version, bool masked,
                                size_t n_bytes);
  
  /* Rate limit for nx_match parse errors.  These always indicate a bug in the
   * peer and so there's not much point in showing a lot of them. */
  static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
  
  static const struct nxm_field *
  mf_parse_subfield_name(const char *name, int name_len, bool *wild);
  
  /* Returns the preferred OXM header to use for field 'id' in OpenFlow version
   * 'version'.  Specify 0 for 'version' if an NXM legacy header should be
   * preferred over any standardized OXM header.  Returns 0 if field 'id' cannot
   * be expressed in NXM or OXM. */
  static uint64_t
  mf_oxm_header(enum mf_field_id id, enum ofp_version version)
  {
      const struct nxm_field *f = nxm_field_by_mf_id(id, version);
      return f ? f->header : 0;
  }
  
  /* Returns the 32-bit OXM or NXM header to use for field 'id', preferring an
   * NXM legacy header over any standardized OXM header.  Returns 0 if field 'id'
   * cannot be expressed with a 32-bit NXM or OXM header.
   *
   * Whenever possible, use nx_pull_header() instead of this function, because
   * this function cannot support 64-bit experimenter OXM headers. */
  uint32_t
  mf_nxm_header(enum mf_field_id id)
  {
      uint64_t oxm = mf_oxm_header(id, 0);
      return is_experimenter_oxm(oxm) ? 0 : oxm >> 32;
  }
  
  /* Returns the 32-bit OXM or NXM header to use for field 'mff'. If 'mff' is
   * a mapped variable length mf_field, update the header with the configured
   * length of 'mff'. Returns 0 if 'mff' cannot be expressed with a 32-bit NXM
   * or OXM header.*/
  uint32_t
  nxm_header_from_mff(const struct mf_field *mff)
  {
      uint64_t oxm = mf_oxm_header(mff->id, 0);
  
      if (mff->mapped) {
          oxm = nxm_no_len(oxm) | ((uint64_t) mff->n_bytes << 32);
      }
  
      return is_experimenter_oxm(oxm) ? 0 : oxm >> 32;
  }
  
  static const struct mf_field *
  mf_from_oxm_header(uint64_t header, const struct vl_mff_map *vl_mff_map)
  {
      const struct nxm_field *f = nxm_field_by_header(header);
  
      if (f) {
          const struct mf_field *mff = mf_from_id(f->id);
          const struct mf_field *vl_mff = mf_get_vl_mff(mff, vl_mff_map);
          return vl_mff ? vl_mff : mff;
      } else {
          return NULL;
      }
  }
  
  /* Returns the "struct mf_field" that corresponds to NXM or OXM header
   * 'header', or NULL if 'header' doesn't correspond to any known field.  */
  const struct mf_field *
  mf_from_nxm_header(uint32_t header, const struct vl_mff_map *vl_mff_map)
  {
      return mf_from_oxm_header((uint64_t) header << 32, vl_mff_map);
  }
  
  /* Returns the width of the data for a field with the given 'header', in
   * bytes. */
  static int
  nxm_field_bytes(uint64_t header)
  {
      unsigned int length = nxm_payload_len(header);
      return nxm_hasmask(header) ? length / 2 : length;
  }
  
  /* nx_pull_match() and helpers. */
  
  /* Given NXM/OXM value 'value' and mask 'mask' associated with 'header', checks
   * for any 1-bit in the value where there is a 0-bit in the mask.  Returns 0 if
   * none, otherwise an error code. */
  static bool
  is_mask_consistent(uint64_t header, const uint8_t *value, const uint8_t *mask)
  {
      unsigned int width = nxm_field_bytes(header);
      unsigned int i;
  
      for (i = 0; i < width; i++) {
          if (value[i] & ~mask[i]) {
              if (!VLOG_DROP_WARN(&rl)) {
                  VLOG_WARN_RL(&rl, "Rejecting NXM/OXM entry "NXM_HEADER_FMT " "
                               "with 1-bits in value for bits wildcarded by the "
                               "mask.", NXM_HEADER_ARGS(header));
              }
              return false;
          }
      }
      return true;
  }
  
  static bool
  is_cookie_pseudoheader(uint64_t header)
  {
      return header == NXM_NX_COOKIE || header == NXM_NX_COOKIE_W;
  }
  
  static enum ofperr
  nx_pull_header__(struct ofpbuf *b, bool allow_cookie,
                   const struct vl_mff_map *vl_mff_map, uint64_t *header,
                   const struct mf_field **field)
  {
      if (b->size < 4) {
          goto bad_len;
      }
  
      *header = ((uint64_t) ntohl(get_unaligned_be32(b->data))) << 32;
      if (is_experimenter_oxm(*header)) {
          if (b->size < 8) {
              goto bad_len;
          }
          *header = ntohll(get_unaligned_be64(b->data));
      }
      if (nxm_length(*header) < nxm_experimenter_len(*header)) {
          VLOG_WARN_RL(&rl, "OXM header "NXM_HEADER_FMT" has invalid length %d "
                       "(minimum is %d)",
                       NXM_HEADER_ARGS(*header), nxm_length(*header),
                       nxm_header_len(*header));
          goto error;
      }
      ofpbuf_pull(b, nxm_header_len(*header));
  
      if (field) {
          *field = mf_from_oxm_header(*header, vl_mff_map);
          if (!*field && !(allow_cookie && is_cookie_pseudoheader(*header))) {
              VLOG_DBG_RL(&rl, "OXM header "NXM_HEADER_FMT" is unknown",
                          NXM_HEADER_ARGS(*header));
              return OFPERR_OFPBMC_BAD_FIELD;
          } else if (mf_vl_mff_invalid(*field, vl_mff_map)) {
              return OFPERR_NXFMFC_INVALID_TLV_FIELD;
          }
      }
  
      return 0;
  
  bad_len:
      VLOG_DBG_RL(&rl, "encountered partial (%"PRIu32"-byte) OXM entry",
                  b->size);
  error:
      *header = 0;
      if (field) {
          *field = NULL;
      }
      return OFPERR_OFPBMC_BAD_LEN;
  }
  
  static void
  copy_entry_value(const struct mf_field *field, union mf_value *value,
                   const uint8_t *payload, int width)
  {
      int copy_len;
      void *copy_dst;
  
      copy_dst = value;
      copy_len = MIN(width, field ? field->n_bytes : sizeof *value);
  
      if (field && field->variable_len) {
          memset(value, 0, field->n_bytes);
          copy_dst = &value->u8 + field->n_bytes - copy_len;
      }
  
      memcpy(copy_dst, payload, copy_len);
  }
  
  static enum ofperr
  nx_pull_entry__(struct ofpbuf *b, bool allow_cookie,
                  const struct vl_mff_map *vl_mff_map, uint64_t *header,
                  const struct mf_field **field_,
                  union mf_value *value, union mf_value *mask)
  {
      const struct mf_field *field;
      enum ofperr header_error;
      unsigned int payload_len;
      const uint8_t *payload;
      int width;
  
      header_error = nx_pull_header__(b, allow_cookie, vl_mff_map, header,
                                      &field);
      if (header_error && header_error != OFPERR_OFPBMC_BAD_FIELD) {
          return header_error;
      }
  
      payload_len = nxm_payload_len(*header);
      payload = ofpbuf_try_pull(b, payload_len);
      if (!payload) {
          VLOG_DBG_RL(&rl, "OXM header "NXM_HEADER_FMT" calls for %u-byte "
                      "payload but only %"PRIu32" bytes follow OXM header",
                      NXM_HEADER_ARGS(*header), payload_len, b->size);
          return OFPERR_OFPBMC_BAD_LEN;
      }
  
      width = nxm_field_bytes(*header);
      if (nxm_hasmask(*header)
          && !is_mask_consistent(*header, payload, payload + width)) {
          return OFPERR_OFPBMC_BAD_WILDCARDS;
      }
  
      copy_entry_value(field, value, payload, width);
  
      if (mask) {
          if (nxm_hasmask(*header)) {
              copy_entry_value(field, mask, payload + width, width);
          } else {
              memset(mask, 0xff, sizeof *mask);
          }
      } else if (nxm_hasmask(*header)) {
          VLOG_DBG_RL(&rl, "OXM header "NXM_HEADER_FMT" includes mask but "
                      "masked OXMs are not allowed here",
                      NXM_HEADER_ARGS(*header));
          return OFPERR_OFPBMC_BAD_MASK;
      }
  
      if (field_) {
          *field_ = field;
          return header_error;
      }
  
      return 0;
  }
  
  /* Attempts to pull an NXM or OXM header, value, and mask (if present) from the
   * beginning of 'b'.  If successful, stores a pointer to the "struct mf_field"
   * corresponding to the pulled header in '*field', the value into '*value',
   * and the mask into '*mask', and returns 0.  On error, returns an OpenFlow
   * error; in this case, some bytes might have been pulled off 'b' anyhow, and
   * the output parameters might have been modified.
   *
   * If a NULL 'mask' is supplied, masked OXM or NXM entries are treated as
   * errors (with OFPERR_OFPBMC_BAD_MASK).
   */
  enum ofperr
  nx_pull_entry(struct ofpbuf *b, const struct vl_mff_map *vl_mff_map,
                const struct mf_field **field, union mf_value *value,
                union mf_value *mask)
  {
      uint64_t header;
  
      return nx_pull_entry__(b, false, vl_mff_map, &header, field, value, mask);
  }
  
  /* Attempts to pull an NXM or OXM header from the beginning of 'b'.  If
   * successful, stores a pointer to the "struct mf_field" corresponding to the
   * pulled header in '*field', stores the header's hasmask bit in '*masked'
   * (true if hasmask=1, false if hasmask=0), and returns 0.  On error, returns
   * an OpenFlow error; in this case, some bytes might have been pulled off 'b'
   * anyhow, and the output parameters might have been modified.
   *
   * If NULL 'masked' is supplied, masked OXM or NXM headers are treated as
   * errors (with OFPERR_OFPBMC_BAD_MASK).
   */
  enum ofperr
  nx_pull_header(struct ofpbuf *b, const struct vl_mff_map *vl_mff_map,
                 const struct mf_field **field, bool *masked)
  {
      enum ofperr error;
      uint64_t header;
  
      error = nx_pull_header__(b, false, vl_mff_map,  &header, field);
      if (masked) {
          *masked = !error && nxm_hasmask(header);
      } else if (!error && nxm_hasmask(header)) {
          error = OFPERR_OFPBMC_BAD_MASK;
      }
      return error;
  }
  
  static enum ofperr
  nx_pull_match_entry(struct ofpbuf *b, bool allow_cookie,
                      const struct vl_mff_map *vl_mff_map,
                      const struct mf_field **field,
                      union mf_value *value, union mf_value *mask)
  {
      enum ofperr error;
      uint64_t header;
  
      error = nx_pull_entry__(b, allow_cookie, vl_mff_map, &header, field, value,
                              mask);
      if (error) {
          return error;
      }
      if (field && *field) {
          if (!mf_is_mask_valid(*field, mask)) {
              VLOG_DBG_RL(&rl, "bad mask for field %s", (*field)->name);
              return OFPERR_OFPBMC_BAD_MASK;
          }
          if (!mf_is_value_valid(*field, value)) {
              VLOG_DBG_RL(&rl, "bad value for field %s", (*field)->name);
              return OFPERR_OFPBMC_BAD_VALUE;
          }
      }
      return 0;
  }
  
  /* Prerequisites will only be checked when 'strict' is 'true'.  This allows
   * decoding conntrack original direction 5-tuple IP addresses without the
   * ethertype being present, when decoding metadata only. */
  static enum ofperr
  nx_pull_raw(const uint8_t *p, unsigned int match_len, bool strict,
              bool pipeline_fields_only, struct match *match, ovs_be64 *cookie,
              ovs_be64 *cookie_mask, const struct tun_table *tun_table,
              const struct vl_mff_map *vl_mff_map)
  {
      ovs_assert((cookie != NULL) == (cookie_mask != NULL));
  
      match_init_catchall(match);
      match->flow.tunnel.metadata.tab = tun_table;
      if (cookie) {
          *cookie = *cookie_mask = htonll(0);
      }
  
      struct ofpbuf b = ofpbuf_const_initializer(p, match_len);
      while (b.size) {
          const uint8_t *pos = b.data;
          const struct mf_field *field;
          union mf_value value;
          union mf_value mask;
          enum ofperr error;
  
          error = nx_pull_match_entry(&b, cookie != NULL, vl_mff_map, &field,
                                      &value, &mask);
          if (error) {
              if (error == OFPERR_OFPBMC_BAD_FIELD && !strict) {
                  continue;
              }
          } else if (!field) {
              if (!cookie) {
                  error = OFPERR_OFPBMC_BAD_FIELD;
              } else if (*cookie_mask) {
                  error = OFPERR_OFPBMC_DUP_FIELD;
              } else {
                  *cookie = value.be64;
                  *cookie_mask = mask.be64;
              }
          } else if (strict && !mf_are_match_prereqs_ok(field, match)) {
              error = OFPERR_OFPBMC_BAD_PREREQ;
          } else if (!mf_is_all_wild(field, &match->wc)) {
              error = OFPERR_OFPBMC_DUP_FIELD;
          } else if (pipeline_fields_only && !mf_is_pipeline_field(field)) {
              error = OFPERR_OFPBRC_PIPELINE_FIELDS_ONLY;
          } else {
              char *err_str;
  
              mf_set(field, &value, &mask, match, &err_str);
              if (err_str) {
                  VLOG_DBG_RL(&rl, "error parsing OXM at offset %"PRIdPTR" "
                             "within match (%s)", pos - p, err_str);
                  free(err_str);
                  return OFPERR_OFPBMC_BAD_VALUE;
              }
  
              match_add_ethernet_prereq(match, field);
          }
  
          if (error) {
              VLOG_DBG_RL(&rl, "error parsing OXM at offset %"PRIdPTR" "
                          "within match (%s)", pos -
                          p, ofperr_to_string(error));
              return error;
          }
      }
  
      match->flow.tunnel.metadata.tab = NULL;
      return 0;
  }
  
  static enum ofperr
  nx_pull_match__(struct ofpbuf *b, unsigned int match_len, bool strict,
                  bool pipeline_fields_only, struct match *match,
                  ovs_be64 *cookie, ovs_be64 *cookie_mask,
                  const struct tun_table *tun_table,
                  const struct vl_mff_map *vl_mff_map)
  {
      uint8_t *p = NULL;
  
      if (match_len) {
          p = ofpbuf_try_pull(b, ROUND_UP(match_len, 8));
          if (!p) {
              VLOG_DBG_RL(&rl, "nx_match length %u, rounded up to a "
                          "multiple of 8, is longer than space in message (max "
                          "length %"PRIu32")", match_len, b->size);
              return OFPERR_OFPBMC_BAD_LEN;
          }
      }
  
      return nx_pull_raw(p, match_len, strict, pipeline_fields_only, match,
                         cookie, cookie_mask, tun_table, vl_mff_map);
  }
  
  /* Parses the nx_match formatted match description in 'b' with length
   * 'match_len'.  Stores the results in 'match'.  If 'cookie' and 'cookie_mask'
   * are valid pointers, then stores the cookie and mask in them if 'b' contains
   * a "NXM_NX_COOKIE*" match.  Otherwise, stores 0 in both.
   * If 'pipeline_fields_only' is true, this function returns
   * OFPERR_OFPBRC_PIPELINE_FIELDS_ONLY if there is any non pipeline fields
   * in 'b'.
   *
   * 'vl_mff_map" is an optional parameter that is used to validate the length
   * of variable length mf_fields in 'match'. If it is not provided, the
   * default mf_fields with maximum length will be used.
   *
   * Fails with an error upon encountering an unknown NXM header.
   *
   * Returns 0 if successful, otherwise an OpenFlow error code. */
  enum ofperr
  nx_pull_match(struct ofpbuf *b, unsigned int match_len, struct match *match,
                ovs_be64 *cookie, ovs_be64 *cookie_mask,
                bool pipeline_fields_only, const struct tun_table *tun_table,
                const struct vl_mff_map *vl_mff_map)
  {
      return nx_pull_match__(b, match_len, true, pipeline_fields_only, match,
                             cookie, cookie_mask, tun_table, vl_mff_map);
  }
  
  /* Behaves the same as nx_pull_match(), but skips over unknown NXM headers,
   * instead of failing with an error, and does not check for field
   * prerequisites. */
  enum ofperr
  nx_pull_match_loose(struct ofpbuf *b, unsigned int match_len,
                      struct match *match, ovs_be64 *cookie,
                      ovs_be64 *cookie_mask, bool pipeline_fields_only,
                      const struct tun_table *tun_table)
  {
      return nx_pull_match__(b, match_len, false, pipeline_fields_only, match,
                             cookie, cookie_mask, tun_table, NULL);
  }
  
  static enum ofperr
  oxm_pull_match__(struct ofpbuf *b, bool strict, bool pipeline_fields_only,
                   const struct tun_table *tun_table,
                   const struct vl_mff_map *vl_mff_map, struct match *match)
  {
      struct ofp11_match_header *omh = b->data;
      uint8_t *p;
      uint16_t match_len;
  
      if (b->size < sizeof *omh) {
          return OFPERR_OFPBMC_BAD_LEN;
      }
  
      match_len = ntohs(omh->length);
      if (match_len < sizeof *omh) {
          return OFPERR_OFPBMC_BAD_LEN;
      }
  
      if (omh->type != htons(OFPMT_OXM)) {
          return OFPERR_OFPBMC_BAD_TYPE;
      }
  
      p = ofpbuf_try_pull(b, ROUND_UP(match_len, 8));
      if (!p) {
          VLOG_DBG_RL(&rl, "oxm length %u, rounded up to a "
                      "multiple of 8, is longer than space in message (max "
                      "length %"PRIu32")", match_len, b->size);
          return OFPERR_OFPBMC_BAD_LEN;
      }
  
      return nx_pull_raw(p + sizeof *omh, match_len - sizeof *omh,
                         strict, pipeline_fields_only, match, NULL, NULL,
                         tun_table, vl_mff_map);
  }
  
  /* Parses the oxm formatted match description preceded by a struct
   * ofp11_match_header in 'b'.  Stores the result in 'match'.
   * If 'pipeline_fields_only' is true, this function returns
   * OFPERR_OFPBRC_PIPELINE_FIELDS_ONLY if there is any non pipeline fields
   * in 'b'.
   *
   * 'vl_mff_map' is an optional parameter that is used to validate the length
   * of variable length mf_fields in 'match'. If it is not provided, the
   * default mf_fields with maximum length will be used.
   *
   * Fails with an error when encountering unknown OXM headers.
   *
   * Returns 0 if successful, otherwise an OpenFlow error code. */
  enum ofperr
  oxm_pull_match(struct ofpbuf *b, bool pipeline_fields_only,
                 const struct tun_table *tun_table,
                 const struct vl_mff_map *vl_mff_map, struct match *match)
  {
      return oxm_pull_match__(b, true, pipeline_fields_only, tun_table,
                              vl_mff_map, match);
  }
  
  /* Behaves the same as oxm_pull_match() with two exceptions.  Skips over
   * unknown OXM headers instead of failing with an error when they are
   * encountered, and does not check for field prerequisites. */
  enum ofperr
  oxm_pull_match_loose(struct ofpbuf *b, bool pipeline_fields_only,
                       const struct tun_table *tun_table, struct match *match)
  {
      return oxm_pull_match__(b, false, pipeline_fields_only, tun_table, NULL,
                              match);
  }
  
  /* Parses the OXM match description in the 'oxm_len' bytes in 'oxm'.  Stores
   * the result in 'match'.
   *
   * Returns 0 if successful, otherwise an OpenFlow error code.
   *
   * If 'loose' is true, encountering unknown OXM headers or missing field
   * prerequisites are not considered as error conditions.
   */
  enum ofperr
  oxm_decode_match(const void *oxm, size_t oxm_len, bool loose,
                   const struct tun_table *tun_table,
                   const struct vl_mff_map *vl_mff_map, struct match *match)
  {
      return nx_pull_raw(oxm, oxm_len, !loose, false, match, NULL, NULL,
                         tun_table, vl_mff_map);
  }
  
  /* Verify an array of OXM TLVs treating value of each TLV as a mask,
   * disallowing masks in each TLV and ignoring pre-requisites. */
  enum ofperr
  oxm_pull_field_array(const void *fields_data, size_t fields_len,
                       struct field_array *fa)
  {
      struct ofpbuf b = ofpbuf_const_initializer(fields_data, fields_len);
      while (b.size) {
          const uint8_t *pos = b.data;
          const struct mf_field *field;
          union mf_value value;
          enum ofperr error;
          uint64_t header;
  
          error = nx_pull_entry__(&b, false, NULL, &header, &field, &value,
                                  NULL);
          if (error) {
              VLOG_DBG_RL(&rl, "error pulling field array field");
              return error;
          } else if (!field) {
              VLOG_DBG_RL(&rl, "unknown field array field");
              error = OFPERR_OFPBMC_BAD_FIELD;
          } else if (bitmap_is_set(fa->used.bm, field->id)) {
              VLOG_DBG_RL(&rl, "duplicate field array field '%s'", field->name);
              error = OFPERR_OFPBMC_DUP_FIELD;
          } else if (!mf_is_mask_valid(field, &value)) {
              VLOG_DBG_RL(&rl, "bad mask in field array field '%s'", field->name);
              return OFPERR_OFPBMC_BAD_MASK;
          } else {
              field_array_set(field->id, &value, fa);
          }
  
          if (error) {
              const uint8_t *start = fields_data;
  
              VLOG_DBG_RL(&rl, "error parsing OXM at offset %"PRIdPTR" "
                          "within field array (%s)", pos - start,
                          ofperr_to_string(error));
              return error;
          }
      }
  
      return 0;
  }
  
  /* nx_put_match() and helpers.
   *
   * 'put' functions whose names end in 'w' add a wildcarded field.
   * 'put' functions whose names end in 'm' add a field that might be wildcarded.
   * Other 'put' functions add exact-match fields.
   */
  
  struct nxm_put_ctx {
      struct ofpbuf *output;
      bool implied_ethernet;
  };
  
  void
  nxm_put_entry_raw(struct ofpbuf *b,
                    enum mf_field_id field, enum ofp_version version,
                    const void *value, const void *mask, size_t n_bytes)
  {
      nx_put_header_len(b, field, version, !!mask, n_bytes);
      ofpbuf_put(b, value, n_bytes);
      if (mask) {
          ofpbuf_put(b, mask, n_bytes);
      }
  }
  
  static void
  nxm_put__(struct nxm_put_ctx *ctx,
            enum mf_field_id field, enum ofp_version version,
            const void *value, const void *mask, size_t n_bytes)
  {
      nxm_put_entry_raw(ctx->output, field, version, value, mask, n_bytes);
      if (!ctx->implied_ethernet && mf_from_id(field)->prereqs != MFP_NONE) {
          ctx->implied_ethernet = true;
      }
  }
  
  static void
  nxm_put(struct nxm_put_ctx *ctx,
          enum mf_field_id field, enum ofp_version version,
          const void *value, const void *mask, size_t n_bytes)
  {
      if (!is_all_zeros(mask, n_bytes)) {
          bool masked = !is_all_ones(mask, n_bytes);
          nxm_put__(ctx, field, version, value, masked ? mask : NULL, n_bytes);
      }
  }
  
  static void
  nxm_put_8m(struct nxm_put_ctx *ctx,
             enum mf_field_id field, enum ofp_version version,
             uint8_t value, uint8_t mask)
  {
      nxm_put(ctx, field, version, &value, &mask, sizeof value);
  }
  
  static void
  nxm_put_8(struct nxm_put_ctx *ctx,
            enum mf_field_id field, enum ofp_version version, uint8_t value)
  {
      nxm_put__(ctx, field, version, &value, NULL, sizeof value);
  }
  
  static void
  nxm_put_16m(struct nxm_put_ctx *ctx,
              enum mf_field_id field, enum ofp_version version,
              ovs_be16 value, ovs_be16 mask)
  {
      nxm_put(ctx, field, version, &value, &mask, sizeof value);
  }
  
  static void
  nxm_put_16(struct nxm_put_ctx *ctx,
             enum mf_field_id field, enum ofp_version version, ovs_be16 value)
  {
      nxm_put__(ctx, field, version, &value, NULL, sizeof value);
  }
  
  static void
  nxm_put_32m(struct nxm_put_ctx *ctx,
              enum mf_field_id field, enum ofp_version version,
              ovs_be32 value, ovs_be32 mask)
  {
      nxm_put(ctx, field, version, &value, &mask, sizeof value);
  }
  
  static void
  nxm_put_32(struct nxm_put_ctx *ctx,
             enum mf_field_id field, enum ofp_version version, ovs_be32 value)
  {
      nxm_put__(ctx, field, version, &value, NULL, sizeof value);
  }
  
  static void
  nxm_put_64m(struct nxm_put_ctx *ctx,
              enum mf_field_id field, enum ofp_version version,
              ovs_be64 value, ovs_be64 mask)
  {
      nxm_put(ctx, field, version, &value, &mask, sizeof value);
  }
  
  static void
  nxm_put_128m(struct nxm_put_ctx *ctx,
               enum mf_field_id field, enum ofp_version version,
               const ovs_be128 value, const ovs_be128 mask)
  {
      nxm_put(ctx, field, version, &value, &mask, sizeof(value));
  }
  
  static void
  nxm_put_eth_masked(struct nxm_put_ctx *ctx,
                     enum mf_field_id field, enum ofp_version version,
                     const struct eth_addr value, const struct eth_addr mask)
  {
      nxm_put(ctx, field, version, value.ea, mask.ea, ETH_ADDR_LEN);
  }
  
  static void
  nxm_put_ipv6(struct nxm_put_ctx *ctx,
               enum mf_field_id field, enum ofp_version version,
               const struct in6_addr *value, const struct in6_addr *mask)
  {
      nxm_put(ctx, field, version, value->s6_addr, mask->s6_addr,
              sizeof value->s6_addr);
  }
  
  static void
  nxm_put_frag(struct nxm_put_ctx *ctx, const struct match *match,
               enum ofp_version version)
  {
      uint8_t nw_frag = match->flow.nw_frag & FLOW_NW_FRAG_MASK;
      uint8_t nw_frag_mask = match->wc.masks.nw_frag & FLOW_NW_FRAG_MASK;
  
      nxm_put_8m(ctx, MFF_IP_FRAG, version, nw_frag,
                 nw_frag_mask == FLOW_NW_FRAG_MASK ? UINT8_MAX : nw_frag_mask);
  }
  
  /* Appends to 'b' a set of OXM or NXM matches for the IPv4 or IPv6 fields in
   * 'match'.  */
  static void
  nxm_put_ip(struct nxm_put_ctx *ctx,
             const struct match *match, enum ofp_version oxm)
  {
      const struct flow *flow = &match->flow;
      ovs_be16 dl_type = get_dl_type(flow);
  
      if (dl_type == htons(ETH_TYPE_IP)) {
          nxm_put_32m(ctx, MFF_IPV4_SRC, oxm,
                      flow->nw_src, match->wc.masks.nw_src);
          nxm_put_32m(ctx, MFF_IPV4_DST, oxm,
                      flow->nw_dst, match->wc.masks.nw_dst);
      } else {
          nxm_put_ipv6(ctx, MFF_IPV6_SRC, oxm,
                       &flow->ipv6_src, &match->wc.masks.ipv6_src);
          nxm_put_ipv6(ctx, MFF_IPV6_DST, oxm,
                       &flow->ipv6_dst, &match->wc.masks.ipv6_dst);
      }
  
      nxm_put_frag(ctx, match, oxm);
  
      if (match->wc.masks.nw_tos & IP_DSCP_MASK) {
          if (oxm) {
              nxm_put_8(ctx, MFF_IP_DSCP_SHIFTED, oxm,
                        flow->nw_tos >> 2);
          } else {
              nxm_put_8(ctx, MFF_IP_DSCP, oxm,
                        flow->nw_tos & IP_DSCP_MASK);
          }
      }
  
      if (match->wc.masks.nw_tos & IP_ECN_MASK) {
          nxm_put_8(ctx, MFF_IP_ECN, oxm,
                    flow->nw_tos & IP_ECN_MASK);
      }
  
      if (match->wc.masks.nw_ttl) {
          nxm_put_8(ctx, MFF_IP_TTL, oxm, flow->nw_ttl);
      }
  
      nxm_put_32m(ctx, MFF_IPV6_LABEL, oxm,
                  flow->ipv6_label, match->wc.masks.ipv6_label);
  
      if (match->wc.masks.nw_proto) {
          nxm_put_8(ctx, MFF_IP_PROTO, oxm, flow->nw_proto);
  
          if (flow->nw_proto == IPPROTO_TCP) {
              nxm_put_16m(ctx, MFF_TCP_SRC, oxm,
                          flow->tp_src, match->wc.masks.tp_src);
              nxm_put_16m(ctx, MFF_TCP_DST, oxm,
                          flow->tp_dst, match->wc.masks.tp_dst);
              nxm_put_16m(ctx, MFF_TCP_FLAGS, oxm,
                          flow->tcp_flags, match->wc.masks.tcp_flags);
          } else if (flow->nw_proto == IPPROTO_UDP) {
              nxm_put_16m(ctx, MFF_UDP_SRC, oxm,
                          flow->tp_src, match->wc.masks.tp_src);
              nxm_put_16m(ctx, MFF_UDP_DST, oxm,
                          flow->tp_dst, match->wc.masks.tp_dst);
          } else if (flow->nw_proto == IPPROTO_SCTP) {
              nxm_put_16m(ctx, MFF_SCTP_SRC, oxm, flow->tp_src,
                          match->wc.masks.tp_src);
              nxm_put_16m(ctx, MFF_SCTP_DST, oxm, flow->tp_dst,
                          match->wc.masks.tp_dst);
          } else if (is_icmpv4(flow, NULL)) {
              if (match->wc.masks.tp_src) {
                  nxm_put_8(ctx, MFF_ICMPV4_TYPE, oxm,
                            ntohs(flow->tp_src));
              }
              if (match->wc.masks.tp_dst) {
                  nxm_put_8(ctx, MFF_ICMPV4_CODE, oxm,
                            ntohs(flow->tp_dst));
              }
          } else if (is_icmpv6(flow, NULL)) {
              if (match->wc.masks.tp_src) {
                  nxm_put_8(ctx, MFF_ICMPV6_TYPE, oxm,
                            ntohs(flow->tp_src));
              }
              if (match->wc.masks.tp_dst) {
                  nxm_put_8(ctx, MFF_ICMPV6_CODE, oxm,
                            ntohs(flow->tp_dst));
              }
              if (is_nd(flow, NULL)) {
                  nxm_put_ipv6(ctx, MFF_ND_TARGET, oxm,
                               &flow->nd_target, &match->wc.masks.nd_target);
                  if (flow->tp_src == htons(ND_NEIGHBOR_SOLICIT)) {
                      nxm_put_eth_masked(ctx, MFF_ND_SLL, oxm,
                                         flow->arp_sha, match->wc.masks.arp_sha);
                  }
                  if (flow->tp_src == htons(ND_NEIGHBOR_ADVERT)) {
                      nxm_put_eth_masked(ctx, MFF_ND_TLL, oxm,
                                         flow->arp_tha, match->wc.masks.arp_tha);
                  }
              }
          }
      }
  }
  
  /* Appends to 'b' the nx_match format that expresses 'match'.  For Flow Mod and
   * Flow Stats Requests messages, a 'cookie' and 'cookie_mask' may be supplied.
   * Otherwise, 'cookie_mask' should be zero.
   *
   * Specify 'oxm' as 0 to express the match in NXM format; otherwise, specify
   * 'oxm' as the OpenFlow version number for the OXM format to use.
   *
   * This function can cause 'b''s data to be reallocated.
   *
   * Returns the number of bytes appended to 'b', excluding padding.
   *
   * If 'match' is a catch-all rule that matches every packet, then this function
   * appends nothing to 'b' and returns 0. */
  static int
  nx_put_raw(struct ofpbuf *b, enum ofp_version oxm, const struct match *match,
             ovs_be64 cookie, ovs_be64 cookie_mask)
  {
      const struct flow *flow = &match->flow;
      const size_t start_len = b->size;
      ovs_be16 dl_type = get_dl_type(flow);
      int match_len;
      int i;
  
      BUILD_ASSERT_DECL(FLOW_WC_SEQ == 40);
  
      struct nxm_put_ctx ctx = { .output = b, .implied_ethernet = false };
  
      /* OpenFlow Packet Type. Must be first. */
      if (match->wc.masks.packet_type && !match_has_default_packet_type(match)) {
          nxm_put_32m(&ctx, MFF_PACKET_TYPE, oxm, flow->packet_type,
                      match->wc.masks.packet_type);
      }
  
      /* Metadata. */
      if (match->wc.masks.dp_hash) {
          nxm_put_32m(&ctx, MFF_DP_HASH, oxm,
                      htonl(flow->dp_hash), htonl(match->wc.masks.dp_hash));
      }
  
      if (match->wc.masks.recirc_id) {
          nxm_put_32(&ctx, MFF_RECIRC_ID, oxm, htonl(flow->recirc_id));
      }
  
      if (match->wc.masks.conj_id) {
          nxm_put_32(&ctx, MFF_CONJ_ID, oxm, htonl(flow->conj_id));
      }
  
      if (match->wc.masks.in_port.ofp_port) {
          ofp_port_t in_port = flow->in_port.ofp_port;
          if (oxm) {
              nxm_put_32(&ctx, MFF_IN_PORT_OXM, oxm,
                         ofputil_port_to_ofp11(in_port));
          } else {
              nxm_put_16(&ctx, MFF_IN_PORT, oxm,
                         htons(ofp_to_u16(in_port)));
          }
      }
      if (match->wc.masks.actset_output) {
          nxm_put_32(&ctx, MFF_ACTSET_OUTPUT, oxm,
                     ofputil_port_to_ofp11(flow->actset_output));
      }
  
      /* Ethernet. */
      nxm_put_eth_masked(&ctx, MFF_ETH_SRC, oxm,
                         flow->dl_src, match->wc.masks.dl_src);
      nxm_put_eth_masked(&ctx, MFF_ETH_DST, oxm,
                         flow->dl_dst, match->wc.masks.dl_dst);
      nxm_put_16m(&ctx, MFF_ETH_TYPE, oxm,
                  ofputil_dl_type_to_openflow(flow->dl_type),
                  match->wc.masks.dl_type);
  
      /* 802.1Q. */
      if (oxm) {
          ovs_be16 VID_CFI_MASK = htons(VLAN_VID_MASK | VLAN_CFI);
          ovs_be16 vid = flow->vlans[0].tci & VID_CFI_MASK;
          ovs_be16 mask = match->wc.masks.vlans[0].tci & VID_CFI_MASK;
  
          if (mask == htons(VLAN_VID_MASK | VLAN_CFI)) {
              nxm_put_16(&ctx, MFF_VLAN_VID, oxm, vid);
          } else if (mask) {
              nxm_put_16m(&ctx, MFF_VLAN_VID, oxm, vid, mask);
          }
  
          if (vid && vlan_tci_to_pcp(match->wc.masks.vlans[0].tci)) {
              nxm_put_8(&ctx, MFF_VLAN_PCP, oxm,
                        vlan_tci_to_pcp(flow->vlans[0].tci));
          }
  
      } else {
          nxm_put_16m(&ctx, MFF_VLAN_TCI, oxm, flow->vlans[0].tci,
                      match->wc.masks.vlans[0].tci);
      }
  
      /* MPLS. */
      if (eth_type_mpls(dl_type)) {
          if (match->wc.masks.mpls_lse[0] & htonl(MPLS_TC_MASK)) {
              nxm_put_8(&ctx, MFF_MPLS_TC, oxm,
                        mpls_lse_to_tc(flow->mpls_lse[0]));
          }
  
          if (match->wc.masks.mpls_lse[0] & htonl(MPLS_BOS_MASK)) {
              nxm_put_8(&ctx, MFF_MPLS_BOS, oxm,
                        mpls_lse_to_bos(flow->mpls_lse[0]));
          }
  
          if (match->wc.masks.mpls_lse[0] & htonl(MPLS_LABEL_MASK)) {
              nxm_put_32(&ctx, MFF_MPLS_LABEL, oxm,
                         htonl(mpls_lse_to_label(flow->mpls_lse[0])));
          }
      }
  
      /* L3. */
      if (is_ip_any(flow)) {
          nxm_put_ip(&ctx, match, oxm);
      } else if (dl_type == htons(ETH_TYPE_ARP) ||
                 dl_type == htons(ETH_TYPE_RARP)) {
          /* ARP. */
          if (match->wc.masks.nw_proto) {
              nxm_put_16(&ctx, MFF_ARP_OP, oxm,
                         htons(flow->nw_proto));
          }
          nxm_put_32m(&ctx, MFF_ARP_SPA, oxm,
                      flow->nw_src, match->wc.masks.nw_src);
          nxm_put_32m(&ctx, MFF_ARP_TPA, oxm,
                      flow->nw_dst, match->wc.masks.nw_dst);
          nxm_put_eth_masked(&ctx, MFF_ARP_SHA, oxm,
                             flow->arp_sha, match->wc.masks.arp_sha);
          nxm_put_eth_masked(&ctx, MFF_ARP_THA, oxm,
                             flow->arp_tha, match->wc.masks.arp_tha);
      }
  
      /* Tunnel ID. */
      nxm_put_64m(&ctx, MFF_TUN_ID, oxm,
                  flow->tunnel.tun_id, match->wc.masks.tunnel.tun_id);
  
      /* Other tunnel metadata. */
      nxm_put_16m(&ctx, MFF_TUN_FLAGS, oxm,
                  htons(flow->tunnel.flags), htons(match->wc.masks.tunnel.flags));
      nxm_put_32m(&ctx, MFF_TUN_SRC, oxm,
                  flow->tunnel.ip_src, match->wc.masks.tunnel.ip_src);
      nxm_put_32m(&ctx, MFF_TUN_DST, oxm,
                  flow->tunnel.ip_dst, match->wc.masks.tunnel.ip_dst);
      nxm_put_ipv6(&ctx, MFF_TUN_IPV6_SRC, oxm,
                   &flow->tunnel.ipv6_src, &match->wc.masks.tunnel.ipv6_src);
      nxm_put_ipv6(&ctx, MFF_TUN_IPV6_DST, oxm,
                   &flow->tunnel.ipv6_dst, &match->wc.masks.tunnel.ipv6_dst);
      nxm_put_16m(&ctx, MFF_TUN_GBP_ID, oxm,
                  flow->tunnel.gbp_id, match->wc.masks.tunnel.gbp_id);
      nxm_put_8m(&ctx, MFF_TUN_GBP_FLAGS, oxm,
                 flow->tunnel.gbp_flags, match->wc.masks.tunnel.gbp_flags);
      tun_metadata_to_nx_match(b, oxm, match);
  
      /* Network Service Header */
      nxm_put_8m(&ctx, MFF_NSH_FLAGS, oxm, flow->nsh.flags,
              match->wc.masks.nsh.flags);
      nxm_put_8m(&ctx, MFF_NSH_MDTYPE, oxm, flow->nsh.mdtype,
              match->wc.masks.nsh.mdtype);
      nxm_put_8m(&ctx, MFF_NSH_NP, oxm, flow->nsh.np,
              match->wc.masks.nsh.np);
      nxm_put_32m(&ctx, MFF_NSH_SPI, oxm, flow->nsh.spi,
                  match->wc.masks.nsh.spi);
      nxm_put_8m(&ctx, MFF_NSH_SI, oxm, flow->nsh.si, match->wc.masks.nsh.si);
      for (int i = 0; i < 4; i++) {
          nxm_put_32m(&ctx, MFF_NSH_C1 + i, oxm, flow->nsh.c[i],
                      match->wc.masks.nsh.c[i]);
      }
  
      /* Registers. */
      if (oxm < OFP15_VERSION) {
          for (i = 0; i < FLOW_N_REGS; i++) {
              nxm_put_32m(&ctx, MFF_REG0 + i, oxm,
                          htonl(flow->regs[i]), htonl(match->wc.masks.regs[i]));
          }
      } else {
          for (i = 0; i < FLOW_N_XREGS; i++) {
              nxm_put_64m(&ctx, MFF_XREG0 + i, oxm,
                          htonll(flow_get_xreg(flow, i)),
                          htonll(flow_get_xreg(&match->wc.masks, i)));
          }
      }
  
      /* Packet mark. */
      nxm_put_32m(&ctx, MFF_PKT_MARK, oxm, htonl(flow->pkt_mark),
                  htonl(match->wc.masks.pkt_mark));
  
      /* Connection tracking. */
      nxm_put_32m(&ctx, MFF_CT_STATE, oxm, htonl(flow->ct_state),
                  htonl(match->wc.masks.ct_state));
      nxm_put_16m(&ctx, MFF_CT_ZONE, oxm, htons(flow->ct_zone),
                  htons(match->wc.masks.ct_zone));
      nxm_put_32m(&ctx, MFF_CT_MARK, oxm, htonl(flow->ct_mark),
                  htonl(match->wc.masks.ct_mark));
      nxm_put_128m(&ctx, MFF_CT_LABEL, oxm, hton128(flow->ct_label),
                   hton128(match->wc.masks.ct_label));
      nxm_put_32m(&ctx, MFF_CT_NW_SRC, oxm,
                  flow->ct_nw_src, match->wc.masks.ct_nw_src);
      nxm_put_ipv6(&ctx, MFF_CT_IPV6_SRC, oxm,
                   &flow->ct_ipv6_src, &match->wc.masks.ct_ipv6_src);
      nxm_put_32m(&ctx, MFF_CT_NW_DST, oxm,
                  flow->ct_nw_dst, match->wc.masks.ct_nw_dst);
      nxm_put_ipv6(&ctx, MFF_CT_IPV6_DST, oxm,
                   &flow->ct_ipv6_dst, &match->wc.masks.ct_ipv6_dst);
      if (flow->ct_nw_proto) {
          nxm_put_8m(&ctx, MFF_CT_NW_PROTO, oxm, flow->ct_nw_proto,
                     match->wc.masks.ct_nw_proto);
          nxm_put_16m(&ctx, MFF_CT_TP_SRC, oxm,
                      flow->ct_tp_src, match->wc.masks.ct_tp_src);
          nxm_put_16m(&ctx, MFF_CT_TP_DST, oxm,
                      flow->ct_tp_dst, match->wc.masks.ct_tp_dst);
      }
      /* OpenFlow 1.1+ Metadata. */
      nxm_put_64m(&ctx, MFF_METADATA, oxm,
                  flow->metadata, match->wc.masks.metadata);
  
      /* Cookie. */
      if (cookie_mask) {
          bool masked = cookie_mask != OVS_BE64_MAX;
  
          cookie &= cookie_mask;
          nx_put_header__(b, NXM_NX_COOKIE, masked);
          ofpbuf_put(b, &cookie, sizeof cookie);
          if (masked) {
              ofpbuf_put(b, &cookie_mask, sizeof cookie_mask);
          }
      }
  
      if (match_has_default_packet_type(match) && !ctx.implied_ethernet) {
          uint64_t pt_stub[16 / 8];
          struct ofpbuf pt;
          ofpbuf_use_stack(&pt, pt_stub, sizeof pt_stub);
          nxm_put_entry_raw(&pt, MFF_PACKET_TYPE, oxm, &flow->packet_type,
                            NULL, sizeof flow->packet_type);
  
          ofpbuf_insert(b, start_len, pt.data, pt.size);
      }
  
      match_len = b->size - start_len;
      return match_len;
  }
  
  /* Appends to 'b' the nx_match format that expresses 'match', plus enough zero
   * bytes to pad the nx_match out to a multiple of 8.  For Flow Mod and Flow
   * Stats Requests messages, a 'cookie' and 'cookie_mask' may be supplied.
   * Otherwise, 'cookie_mask' should be zero.
   *
   * This function can cause 'b''s data to be reallocated.
   *
   * Returns the number of bytes appended to 'b', excluding padding.  The return
   * value can be zero if it appended nothing at all to 'b' (which happens if
   * 'cr' is a catch-all rule that matches every packet). */
  int
  nx_put_match(struct ofpbuf *b, const struct match *match,
               ovs_be64 cookie, ovs_be64 cookie_mask)
  {
      int match_len = nx_put_raw(b, 0, match, cookie, cookie_mask);
  
      ofpbuf_put_zeros(b, PAD_SIZE(match_len, 8));
      return match_len;
  }
  
  /* Appends to 'b' an struct ofp11_match_header followed by the OXM format that
   * expresses 'match', plus enough zero bytes to pad the data appended out to a
   * multiple of 8.
   *
   * OXM differs slightly among versions of OpenFlow.  Specify the OpenFlow
   * version in use as 'version'.
   *
   * This function can cause 'b''s data to be reallocated.
   *
   * Returns the number of bytes appended to 'b', excluding the padding.  Never
   * returns zero. */
  int
  oxm_put_match(struct ofpbuf *b, const struct match *match,
                enum ofp_version version)
  {
      int match_len;
      struct ofp11_match_header *omh;
      size_t start_len = b->size;
      ovs_be64 cookie = htonll(0), cookie_mask = htonll(0);
  
      ofpbuf_put_uninit(b, sizeof *omh);
      match_len = (nx_put_raw(b, version, match, cookie, cookie_mask)
                   + sizeof *omh);
      ofpbuf_put_zeros(b, PAD_SIZE(match_len, 8));
  
      omh = ofpbuf_at(b, start_len, sizeof *omh);
      omh->type = htons(OFPMT_OXM);
      omh->length = htons(match_len);
  
      return match_len;
  }
  
  /* Appends to 'b' the OXM formats that expresses 'match', without header or
   * padding.
   *
   * OXM differs slightly among versions of OpenFlow.  Specify the OpenFlow
   * version in use as 'version'.
   *
   * This function can cause 'b''s data to be reallocated. */
  void
  oxm_put_raw(struct ofpbuf *b, const struct match *match,
              enum ofp_version version)
  {
      nx_put_raw(b, version, match, 0, 0);
  }
  
  /* Appends to 'b' the nx_match format that expresses the tlv corresponding
   * to 'id'. If mask is not all-ones then it is also formated as the value
   * of the tlv. */
  static void
  nx_format_mask_tlv(struct ds *ds, enum mf_field_id id,
                     const union mf_value *mask)
  {
      const struct mf_field *mf = mf_from_id(id);
  
      ds_put_format(ds, "%s", mf->name);
  
      if (!is_all_ones(mask, mf->n_bytes)) {
          ds_put_char(ds, '=');
          mf_format(mf, mask, NULL, NULL, ds);
      }
  
      ds_put_char(ds, ',');
  }
  
  /* Appends a string representation of 'fa_' to 'ds'.
   * The TLVS value of 'fa_' is treated as a mask and
   * only the name of fields is formated if it is all ones. */
  void
  oxm_format_field_array(struct ds *ds, const struct field_array *fa)
  {
      size_t start_len = ds->length;
      size_t i, offset = 0;
  
      BITMAP_FOR_EACH_1 (i, MFF_N_IDS, fa->used.bm) {
          const struct mf_field *mf = mf_from_id(i);
          union mf_value value;
  
          memcpy(&value, fa->values + offset, mf->n_bytes);
          nx_format_mask_tlv(ds, i, &value);
          offset += mf->n_bytes;
      }
  
      if (ds->length > start_len) {
          ds_chomp(ds, ',');
      }
  }
  
  /* Appends to 'b' a series of OXM TLVs corresponding to the series
   * of enum mf_field_id and value tuples in 'fa_'.
   *
   * OXM differs slightly among versions of OpenFlow.  Specify the OpenFlow
   * version in use as 'version'.
   *
   * This function can cause 'b''s data to be reallocated.
   *
   * Returns the number of bytes appended to 'b'.  May return zero. */
  int
  oxm_put_field_array(struct ofpbuf *b, const struct field_array *fa,
                      enum ofp_version version)
  {
      size_t start_len = b->size;
  
      /* Field arrays are only used with the group selection method
       * property and group properties are only available in OpenFlow 1.5+.
       * So the following assertion should never fail.
       *
       * If support for older OpenFlow versions is desired then some care
       * will need to be taken of different TLVs that handle the same
       * flow fields. In particular:
       * - VLAN_TCI, VLAN_VID and MFF_VLAN_PCP
       * - IP_DSCP_MASK and DSCP_SHIFTED
       * - REGS and XREGS
       */
      ovs_assert(version >= OFP15_VERSION);
  
      size_t i, offset = 0;
  
      BITMAP_FOR_EACH_1 (i, MFF_N_IDS, fa->used.bm) {
          const struct mf_field *mf = mf_from_id(i);
          union mf_value value;
  
          memcpy(&value, fa->values + offset, mf->n_bytes);
  
          int len = mf_field_len(mf, &value, NULL, NULL);
          nxm_put_entry_raw(b, i, version,
                            &value + mf->n_bytes - len, NULL, len);
          offset += mf->n_bytes;
      }
  
      return b->size - start_len;
  }
  
  static void
  nx_put_header__(struct ofpbuf *b, uint64_t header, bool masked)
  {
      uint64_t masked_header = masked ? nxm_make_wild_header(header) : header;
      ovs_be64 network_header = htonll(masked_header);
  
      ofpbuf_put(b, &network_header, nxm_header_len(header));
  }
  
  void
  nx_put_header(struct ofpbuf *b, enum mf_field_id field,
                enum ofp_version version, bool masked)
  {
      nx_put_header__(b, mf_oxm_header(field, version), masked);
  }
  
  void nx_put_mff_header(struct ofpbuf *b, const struct mf_field *mff,
                         enum ofp_version version, bool masked)
  {
      if (mff->mapped) {
          nx_put_header_len(b, mff->id, version, masked, mff->n_bytes);
      } else {
          nx_put_header(b, mff->id, version, masked);
      }
  }
  
  static void
  nx_put_header_len(struct ofpbuf *b, enum mf_field_id field,
                    enum ofp_version version, bool masked, size_t n_bytes)
  {
      uint64_t header = mf_oxm_header(field, version);
  
      header = NXM_HEADER(nxm_vendor(header), nxm_class(header),
                          nxm_field(header), false,
                          nxm_experimenter_len(header) + n_bytes);
  
      nx_put_header__(b, header, masked);
  }
  
  void
  nx_put_entry(struct ofpbuf *b, const struct mf_field *mff,
               enum ofp_version version, const union mf_value *value,
               const union mf_value *mask)
  {
      bool masked;
      int len, offset;
  
      len = mf_field_len(mff, value, mask, &masked);
      offset = mff->n_bytes - len;
  
      nxm_put_entry_raw(b, mff->id, version,
                        &value->u8 + offset, masked ? &mask->u8 + offset : NULL,
                        len);
  }
  
  /* nx_match_to_string() and helpers. */
  
  static void format_nxm_field_name(struct ds *, uint64_t header);
  
  char *
  nx_match_to_string(const uint8_t *p, unsigned int match_len)
  {
      if (!match_len) {
          return xstrdup("<any>");
      }
  
      struct ofpbuf b = ofpbuf_const_initializer(p, match_len);
      struct ds s = DS_EMPTY_INITIALIZER;
      while (b.size) {
          union mf_value value;
          union mf_value mask;
          enum ofperr error;
          uint64_t header;
          int value_len;
  
          error = nx_pull_entry__(&b, true, NULL, &header, NULL, &value, &mask);
          if (error) {
              break;
          }
          value_len = MIN(sizeof value, nxm_field_bytes(header));
  
          if (s.length) {
              ds_put_cstr(&s, ", ");
          }
  
          format_nxm_field_name(&s, header);
          ds_put_char(&s, '(');
  
          for (int i = 0; i < value_len; i++) {
              ds_put_format(&s, "%02x", ((const uint8_t *) &value)[i]);
          }
          if (nxm_hasmask(header)) {
              ds_put_char(&s, '/');
              for (int i = 0; i < value_len; i++) {
                  ds_put_format(&s, "%02x", ((const uint8_t *) &mask)[i]);
              }
          }
          ds_put_char(&s, ')');
      }
  
      if (b.size) {
          if (s.length) {
              ds_put_cstr(&s, ", ");
          }
  
          ds_put_format(&s, "<%u invalid bytes>", b.size);
      }
  
      return ds_steal_cstr(&s);
  }
  
  char *
  oxm_match_to_string(const struct ofpbuf *p, unsigned int match_len)
  {
      const struct ofp11_match_header *omh = p->data;
      uint16_t match_len_;
      struct ds s;
  
      ds_init(&s);
  
      if (match_len < sizeof *omh) {
          ds_put_format(&s, "<match too short: %u>", match_len);
          goto err;
      }
  
      if (omh->type != htons(OFPMT_OXM)) {
          ds_put_format(&s, "<bad match type field: %u>", ntohs(omh->type));
          goto err;
      }
  
      match_len_ = ntohs(omh->length);
      if (match_len_ < sizeof *omh) {
          ds_put_format(&s, "<match length field too short: %u>", match_len_);
          goto err;
      }
  
      if (match_len_ != match_len) {
          ds_put_format(&s, "<match length field incorrect: %u != %u>",
                        match_len_, match_len);
          goto err;
      }
  
      return nx_match_to_string(ofpbuf_at(p, sizeof *omh, 0),
                                match_len - sizeof *omh);
  
  err:
      return ds_steal_cstr(&s);
  }
  
  void
  nx_format_field_name(enum mf_field_id id, enum ofp_version version,
                       struct ds *s)
  {
      format_nxm_field_name(s, mf_oxm_header(id, version));
  }
  
  static void
  format_nxm_field_name(struct ds *s, uint64_t header)
  {
      const struct nxm_field *f = nxm_field_by_header(header);
      if (f) {
          ds_put_cstr(s, f->name);
          if (nxm_hasmask(header)) {
              ds_put_cstr(s, "_W");
          }
      } else if (header == NXM_NX_COOKIE) {
          ds_put_cstr(s, "NXM_NX_COOKIE");
      } else if (header == NXM_NX_COOKIE_W) {
          ds_put_cstr(s, "NXM_NX_COOKIE_W");
      } else {
          ds_put_format(s, "%d:%d", nxm_class(header), nxm_field(header));
      }
  }
  
  static bool
  streq_len(const char *a, size_t a_len, const char *b)
  {
      return strlen(b) == a_len && !memcmp(a, b, a_len);
  }
  
  static uint64_t
  parse_nxm_field_name(const char *name, int name_len)
  {
      const struct nxm_field *f;
      bool wild;
  
      f = mf_parse_subfield_name(name, name_len, &wild);
      if (f) {
          if (!wild) {
              return f->header;
          } else if (mf_from_id(f->id)->maskable != MFM_NONE) {
              return nxm_make_wild_header(f->header);
          }
      }
  
      if (streq_len(name, name_len, "NXM_NX_COOKIE")) {
          return NXM_NX_COOKIE;
      } else if (streq_len(name, name_len, "NXM_NX_COOKIE_W")) {
          return NXM_NX_COOKIE_W;
      }
  
      /* Check whether it's a field header value as hex.
       * (This isn't ordinarily useful except for testing error behavior.) */
      if (name_len == 8) {
          uint64_t header;
          bool ok;
  
          header = hexits_value(name, name_len, &ok) << 32;
          if (ok) {
              return header;
          }
      } else if (name_len == 16) {
          uint64_t header;
          bool ok;
  
          header = hexits_value(name, name_len, &ok);
          if (ok && is_experimenter_oxm(header)) {
              return header;
          }
      }
  
      return 0;
  }
  
  /* nx_match_from_string(). */
  
  static int
  nx_match_from_string_raw(const char *s, struct ofpbuf *b)
  {
      const char *full_s = s;
      const size_t start_len = b->size;
  
      if (!strcmp(s, "<any>")) {
          /* Ensure that 'b->data' isn't actually null. */
          ofpbuf_prealloc_tailroom(b, 1);
          return 0;
      }
  
      for (s += strspn(s, ", "); *s; s += strspn(s, ", ")) {
          const char *name;
          uint64_t header;
          ovs_be64 nw_header;
          int name_len;
          size_t n;
  
          name = s;
          name_len = strcspn(s, "(");
          if (s[name_len] != '(') {
              ovs_fatal(0, "%s: missing ( at end of nx_match", full_s);
          }
  
          header = parse_nxm_field_name(name, name_len);
          if (!header) {
              ovs_fatal(0, "%s: unknown field `%.*s'", full_s, name_len, s);
          }
  
          s += name_len + 1;
  
          b->header = ofpbuf_put_uninit(b, nxm_header_len(header));
          s = ofpbuf_put_hex(b, s, &n);
          if (n != nxm_field_bytes(header)) {
              const struct mf_field *field = mf_from_oxm_header(header, NULL);
  
              if (field && field->variable_len) {
                  if (n <= field->n_bytes) {
                      int len = (nxm_hasmask(header) ? n * 2 : n) +
                                nxm_experimenter_len(header);
  
                      header = NXM_HEADER(nxm_vendor(header), nxm_class(header),
                                          nxm_field(header),
                                          nxm_hasmask(header) ? 1 : 0, len);
                  } else {
                      ovs_fatal(0, "expected to read at most %d bytes but got "
                                "%"PRIuSIZE, field->n_bytes, n);
                  }
              } else {
                  ovs_fatal(0, "expected to read %d bytes but got %"PRIuSIZE,
                            nxm_field_bytes(header), n);
              }
          }
          nw_header = htonll(header);
          memcpy(b->header, &nw_header, nxm_header_len(header));
  
          if (nxm_hasmask(header)) {
              s += strspn(s, " ");
              if (*s != '/') {
                  ovs_fatal(0, "%s: missing / in masked field %.*s",
                            full_s, name_len, name);
              }
              s = ofpbuf_put_hex(b, s + 1, &n);
              if (n != nxm_field_bytes(header)) {
                  ovs_fatal(0, "%.2s: hex digits expected", s);
              }
          }
  
          s += strspn(s, " ");
          if (*s != ')') {
              ovs_fatal(0, "%s: missing ) following field %.*s",
                        full_s, name_len, name);
          }
          s++;
      }
  
      return b->size - start_len;
  }
  
  int
  nx_match_from_string(const char *s, struct ofpbuf *b)
  {
      int match_len = nx_match_from_string_raw(s, b);
      ofpbuf_put_zeros(b, PAD_SIZE(match_len, 8));
      return match_len;
  }
  
  int
  oxm_match_from_string(const char *s, struct ofpbuf *b)
  {
      int match_len;
      struct ofp11_match_header *omh;
      size_t start_len = b->size;
  
      ofpbuf_put_uninit(b, sizeof *omh);
      match_len = nx_match_from_string_raw(s, b) + sizeof *omh;
      ofpbuf_put_zeros(b, PAD_SIZE(match_len, 8));
  
      omh = ofpbuf_at(b, start_len, sizeof *omh);
      omh->type = htons(OFPMT_OXM);
      omh->length = htons(match_len);
  
      return match_len;
  }
  
  /* Parses 's' as a "move" action, in the form described in ovs-ofctl(8), into
   * '*move'.
   *
   * Returns NULL if successful, otherwise a malloc()'d string describing the
   * error.  The caller is responsible for freeing the returned string. */
  char * OVS_WARN_UNUSED_RESULT
  nxm_parse_reg_move(struct ofpact_reg_move *move, const char *s)
  {
      const char *full_s = s;
      char *error;
  
      error = mf_parse_subfield__(&move->src, &s);
      if (error) {
          return error;
      }
      if (strncmp(s, "->", 2)) {
          return xasprintf("%s: missing `->' following source", full_s);
      }
      s += 2;
      error = mf_parse_subfield(&move->dst, s);
      if (error) {
          return error;
      }
  
      if (move->src.n_bits != move->dst.n_bits) {
          return xasprintf("%s: source field is %d bits wide but destination is "
                           "%d bits wide", full_s,
                           move->src.n_bits, move->dst.n_bits);
      }
      return NULL;
  }
  
  /* nxm_format_reg_move(). */
  
  void
  nxm_format_reg_move(const struct ofpact_reg_move *move, struct ds *s)
  {
      ds_put_format(s, "%smove:%s", colors.special, colors.end);
      mf_format_subfield(&move->src, s);
      ds_put_format(s, "%s->%s", colors.special, colors.end);
      mf_format_subfield(&move->dst, s);
  }
  
  
  enum ofperr
  nxm_reg_move_check(const struct ofpact_reg_move *move,
                     const struct match *match)
  {
      enum ofperr error;
  
      error = mf_check_src(&move->src, match);
      if (error) {
          return error;
      }
  
      return mf_check_dst(&move->dst, match);
  }
  
  /* nxm_execute_reg_move(). */
  
  void
  nxm_reg_load(const struct mf_subfield *dst, uint64_t src_data,
               struct flow *flow, struct flow_wildcards *wc)
  {
      union mf_subvalue src_subvalue;
      union mf_subvalue mask_value;
      ovs_be64 src_data_be = htonll(src_data);
  
      memset(&mask_value, 0xff, sizeof mask_value);
      mf_write_subfield_flow(dst, &mask_value, &wc->masks);
  
      bitwise_copy(&src_data_be, sizeof src_data_be, 0,
                   &src_subvalue, sizeof src_subvalue, 0,
                   sizeof src_data_be * 8);
      mf_write_subfield_flow(dst, &src_subvalue, flow);
  }
  
  /* nxm_parse_stack_action, works for both push() and pop(). */
  
  /* Parses 's' as a "push" or "pop" action, in the form described in
   * ovs-ofctl(8), into '*stack_action'.
   *
   * Returns NULL if successful, otherwise a malloc()'d string describing the
   * error.  The caller is responsible for freeing the returned string. */
  char * OVS_WARN_UNUSED_RESULT
  nxm_parse_stack_action(struct ofpact_stack *stack_action, const char *s)
  {
      char *error;
  
      error = mf_parse_subfield__(&stack_action->subfield, &s);
      if (error) {
          return error;
      }
  
      if (*s != '\0') {
          return xasprintf("%s: trailing garbage following push or pop", s);
      }
  
      return NULL;
  }
  
  void
  nxm_format_stack_push(const struct ofpact_stack *push, struct ds *s)
  {
      ds_put_format(s, "%spush:%s", colors.param, colors.end);
      mf_format_subfield(&push->subfield, s);
  }
  
  void
  nxm_format_stack_pop(const struct ofpact_stack *pop, struct ds *s)
  {
      ds_put_format(s, "%spop:%s", colors.param, colors.end);
      mf_format_subfield(&pop->subfield, s);
  }
  
  enum ofperr
  nxm_stack_push_check(const struct ofpact_stack *push,
                       const struct match *match)
  {
      return mf_check_src(&push->subfield, match);
  }
  
  enum ofperr
  nxm_stack_pop_check(const struct ofpact_stack *pop,
                      const struct match *match)
  {
      return mf_check_dst(&pop->subfield, match);
  }
  
  /* nxm_execute_stack_push(), nxm_execute_stack_pop().
   *
   * A stack is an ofpbuf with 'data' pointing to the bottom of the stack and
   * 'size' indexing the top of the stack.  Each value of some byte length is
   * stored to the stack immediately followed by the length of the value as an
   * unsigned byte.  This way a POP operation can first read the length byte, and
   * then the appropriate number of bytes from the stack.  This also means that
   * it is only possible to traverse the stack from top to bottom.  It is
   * possible, however, to push values also to the bottom of the stack, which is
   * useful when a stack has been serialized to a wire format in reverse order
   * (topmost value first).
   */
  
  /* Push value 'v' of length 'bytes' to the top of 'stack'. */
  void
  nx_stack_push(struct ofpbuf *stack, const void *v, uint8_t bytes)
  {
      ofpbuf_put(stack, v, bytes);
      ofpbuf_put(stack, &bytes, sizeof bytes);
  }
  
  /* Push value 'v' of length 'bytes' to the bottom of 'stack'. */
  void
  nx_stack_push_bottom(struct ofpbuf *stack, const void *v, uint8_t bytes)
  {
      ofpbuf_push(stack, &bytes, sizeof bytes);
      ofpbuf_push(stack, v, bytes);
  }
  
  /* Pop the topmost value from 'stack', returning a pointer to the value in the
   * stack and the length of the value in '*bytes'.  In case of underflow a NULL
   * is returned and length is returned as zero via '*bytes'. */
  void *
  nx_stack_pop(struct ofpbuf *stack, uint8_t *bytes)
  {
      if (!stack->size) {
          *bytes = 0;
          return NULL;
      }
  
      stack->size -= sizeof *bytes;
      memcpy(bytes, ofpbuf_tail(stack), sizeof *bytes);
  
      ovs_assert(stack->size >= *bytes);
      stack->size -= *bytes;
      return ofpbuf_tail(stack);
  }
  
  void
  nxm_execute_stack_push(const struct ofpact_stack *push,
                         const struct flow *flow, struct flow_wildcards *wc,
                         struct ofpbuf *stack)
  {
      union mf_subvalue dst_value;
  
      mf_write_subfield_flow(&push->subfield,
                             (union mf_subvalue *)&exact_match_mask,
                             &wc->masks);
  
      mf_read_subfield(&push->subfield, flow, &dst_value);
      uint8_t bytes = DIV_ROUND_UP(push->subfield.n_bits, 8);
      nx_stack_push(stack, &dst_value.u8[sizeof dst_value - bytes], bytes);
  }
  
  bool
  nxm_execute_stack_pop(const struct ofpact_stack *pop,
                        struct flow *flow, struct flow_wildcards *wc,
                        struct ofpbuf *stack)
  {
      uint8_t src_bytes;
      const void *src = nx_stack_pop(stack, &src_bytes);
      if (src) {
          union mf_subvalue src_value;
          uint8_t dst_bytes = DIV_ROUND_UP(pop->subfield.n_bits, 8);
  
          if (src_bytes < dst_bytes) {
              memset(&src_value.u8[sizeof src_value - dst_bytes], 0,
                     dst_bytes - src_bytes);
          }
          memcpy(&src_value.u8[sizeof src_value - src_bytes], src, src_bytes);
          mf_write_subfield_flow(&pop->subfield,
                                 (union mf_subvalue *)&exact_match_mask,
                                 &wc->masks);
          mf_write_subfield_flow(&pop->subfield, &src_value, flow);
          return true;
      } else {
          /* Attempted to pop from an empty stack. */
          return false;
      }
  }
  
  /* Formats 'sf' into 's' in a format normally acceptable to
   * mf_parse_subfield().  (It won't be acceptable if sf->field is NULL or if
   * sf->field has no NXM name.) */
  void
  mf_format_subfield(const struct mf_subfield *sf, struct ds *s)
  {
      if (!sf->field) {
          ds_put_cstr(s, "<unknown>");
      } else {
          const struct nxm_field *f = nxm_field_by_mf_id(sf->field->id, 0);
          ds_put_cstr(s, f ? f->name : sf->field->name);
      }
  
      if (sf->field && sf->ofs == 0 && sf->n_bits == sf->field->n_bits) {
          ds_put_cstr(s, "[]");
      } else if (sf->n_bits == 1) {
          ds_put_format(s, "[%d]", sf->ofs);
      } else {
          ds_put_format(s, "[%d..%d]", sf->ofs, sf->ofs + sf->n_bits - 1);
      }
  }
  
  static const struct nxm_field *
  mf_parse_subfield_name(const char *name, int name_len, bool *wild)
  {
      *wild = name_len > 2 && !memcmp(&name[name_len - 2], "_W", 2);
      if (*wild) {
          name_len -= 2;
      }
  
      return nxm_field_by_name(name, name_len);
  }
  
  /* Parses a subfield from the beginning of '*sp' into 'sf'.  If successful,
   * returns NULL and advances '*sp' to the first byte following the parsed
   * string.  On failure, returns a malloc()'d error message, does not modify
   * '*sp', and does not properly initialize 'sf'.
   *
   * The syntax parsed from '*sp' takes the form "header[start..end]" where
   * 'header' is the name of an NXM field and 'start' and 'end' are (inclusive)
   * bit indexes.  "..end" may be omitted to indicate a single bit.  "start..end"
   * may both be omitted (the [] are still required) to indicate an entire
   * field. */
  char * OVS_WARN_UNUSED_RESULT
  mf_parse_subfield__(struct mf_subfield *sf, const char **sp)
  {
      const struct mf_field *field = NULL;
      const struct nxm_field *f;
      const char *name;
      int start, end;
      const char *s;
      int name_len;
      bool wild;
  
      s = *sp;
      name = s;
      name_len = strcspn(s, "[-");
  
      f = mf_parse_subfield_name(name, name_len, &wild);
      field = f ? mf_from_id(f->id) : mf_from_name_len(name, name_len);
      if (!field) {
          return xasprintf("%s: unknown field `%.*s'", *sp, name_len, s);
      }
  
      s += name_len;
      /* Assume full field. */
      start = 0;
      end = field->n_bits - 1;
      if (*s == '[') {
          if (!strncmp(s, "[]", 2)) {
              /* Nothing to do. */
          } else if (ovs_scan(s, "[%d..%d]", &start, &end)) {
              /* Nothing to do. */
          } else if (ovs_scan(s, "[%d]", &start)) {
              end = start;
          } else {
              return xasprintf("%s: syntax error expecting [] or [<bit>] or "
                               "[<start>..<end>]", *sp);
          }
          s = strchr(s, ']') + 1;
      }
  
      if (start > end) {
          return xasprintf("%s: starting bit %d is after ending bit %d",
                           *sp, start, end);
      } else if (start >= field->n_bits) {
          return xasprintf("%s: starting bit %d is not valid because field is "
                           "only %d bits wide", *sp, start, field->n_bits);
      } else if (end >= field->n_bits){
          return xasprintf("%s: ending bit %d is not valid because field is "
                           "only %d bits wide", *sp, end, field->n_bits);
      }
  
      sf->field = field;
      sf->ofs = start;
      sf->n_bits = end - start + 1;
  
      *sp = s;
      return NULL;
  }
  
  /* Parses a subfield from the entirety of 's' into 'sf'.  Returns NULL if
   * successful, otherwise a malloc()'d string describing the error.  The caller
   * is responsible for freeing the returned string.
   *
   * The syntax parsed from 's' takes the form "header[start..end]" where
   * 'header' is the name of an NXM field and 'start' and 'end' are (inclusive)
   * bit indexes.  "..end" may be omitted to indicate a single bit.  "start..end"
   * may both be omitted (the [] are still required) to indicate an entire
   * field.  */
  char * OVS_WARN_UNUSED_RESULT
  mf_parse_subfield(struct mf_subfield *sf, const char *s)
  {
      char *error = mf_parse_subfield__(sf, &s);
      if (!error && s[0]) {
          error = xstrdup("unexpected input following field syntax");
      }
      return error;
  }
  
  /* Returns an bitmap in which each bit corresponds to the like-numbered field
   * in the OFPXMC12_OPENFLOW_BASIC OXM class, in which the bit values are taken
   * from the 'fields' bitmap.  Only fields defined in OpenFlow 'version' are
   * considered.
   *
   * This is useful for encoding OpenFlow 1.2 table stats messages. */
  ovs_be64
  oxm_bitmap_from_mf_bitmap(const struct mf_bitmap *fields,
                            enum ofp_version version)
  {
      uint64_t oxm_bitmap = 0;
      int i;
  
      BITMAP_FOR_EACH_1 (i, MFF_N_IDS, fields->bm) {
          uint64_t oxm = mf_oxm_header(i, version);
          uint32_t class = nxm_class(oxm);
          int field = nxm_field(oxm);
  
          if (class == OFPXMC12_OPENFLOW_BASIC && field < 64) {
              oxm_bitmap |= UINT64_C(1) << field;
          }
      }
      return htonll(oxm_bitmap);
  }
  
  /* Opposite conversion from oxm_bitmap_from_mf_bitmap().
   *
   * This is useful for decoding OpenFlow 1.2 table stats messages. */
  struct mf_bitmap
  oxm_bitmap_to_mf_bitmap(ovs_be64 oxm_bitmap, enum ofp_version version)
  {
      struct mf_bitmap fields = MF_BITMAP_INITIALIZER;
  
      for (enum mf_field_id id = 0; id < MFF_N_IDS; id++) {
          uint64_t oxm = mf_oxm_header(id, version);
          if (oxm && version >= nxm_field_by_header(oxm)->version) {
              uint32_t class = nxm_class(oxm);
              int field = nxm_field(oxm);
  
              if (class == OFPXMC12_OPENFLOW_BASIC
                  && field < 64
                  && oxm_bitmap & htonll(UINT64_C(1) << field)) {
                  bitmap_set1(fields.bm, id);
              }
          }
      }
      return fields;
  }
  
  /* Returns a bitmap of fields that can be encoded in OXM and that can be
   * modified with a "set_field" action.  */
  struct mf_bitmap
  oxm_writable_fields(void)
  {
      struct mf_bitmap b = MF_BITMAP_INITIALIZER;
      int i;
  
      for (i = 0; i < MFF_N_IDS; i++) {
          if (mf_oxm_header(i, 0) && mf_from_id(i)->writable) {
              bitmap_set1(b.bm, i);
          }
      }
      return b;
  }
  
  /* Returns a bitmap of fields that can be encoded in OXM and that can be
   * matched in a flow table.  */
  struct mf_bitmap
  oxm_matchable_fields(void)
  {
      struct mf_bitmap b = MF_BITMAP_INITIALIZER;
      int i;
  
      for (i = 0; i < MFF_N_IDS; i++) {
          if (mf_oxm_header(i, 0)) {
              bitmap_set1(b.bm, i);
          }
      }
      return b;
  }
  
  /* Returns a bitmap of fields that can be encoded in OXM and that can be
   * matched in a flow table with an arbitrary bitmask.  */
  struct mf_bitmap
  oxm_maskable_fields(void)
  {
      struct mf_bitmap b = MF_BITMAP_INITIALIZER;
      int i;
  
      for (i = 0; i < MFF_N_IDS; i++) {
          if (mf_oxm_header(i, 0) && mf_from_id(i)->maskable == MFM_FULLY) {
              bitmap_set1(b.bm, i);
          }
      }
      return b;
  }
  
  struct nxm_field_index {
      struct hmap_node header_node; /* In nxm_header_map. */
      struct hmap_node name_node;   /* In nxm_name_map. */
      struct ovs_list mf_node;      /* In mf_mf_map[nf.id]. */
      const struct nxm_field nf;
  };
  
  #include "nx-match.inc"
  
  static struct hmap nxm_header_map;
  static struct hmap nxm_name_map;
  static struct ovs_list nxm_mf_map[MFF_N_IDS];
  
  static void
  nxm_init(void)
  {
      static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
      if (ovsthread_once_start(&once)) {
          hmap_init(&nxm_header_map);
          hmap_init(&nxm_name_map);
          for (int i = 0; i < MFF_N_IDS; i++) {
              ovs_list_init(&nxm_mf_map[i]);
          }
          for (struct nxm_field_index *nfi = all_nxm_fields;
               nfi < &all_nxm_fields[ARRAY_SIZE(all_nxm_fields)]; nfi++) {
              hmap_insert(&nxm_header_map, &nfi->header_node,
                          hash_uint64(nxm_no_len(nfi->nf.header)));
              hmap_insert(&nxm_name_map, &nfi->name_node,
                          hash_string(nfi->nf.name, 0));
              ovs_list_push_back(&nxm_mf_map[nfi->nf.id], &nfi->mf_node);
          }
          ovsthread_once_done(&once);
      }
  }
  
  static const struct nxm_field *
  nxm_field_by_header(uint64_t header)
  {
      const struct nxm_field_index *nfi;
      uint64_t header_no_len;
  
      nxm_init();
      if (nxm_hasmask(header)) {
          header = nxm_make_exact_header(header);
      }
  
      header_no_len = nxm_no_len(header);
  
      HMAP_FOR_EACH_IN_BUCKET (nfi, header_node, hash_uint64(header_no_len),
                               &nxm_header_map) {
          if (header_no_len == nxm_no_len(nfi->nf.header)) {
              if (nxm_length(header) == nxm_length(nfi->nf.header) ||
                  mf_from_id(nfi->nf.id)->variable_len) {
                  return &nfi->nf;
              } else {
                  return NULL;
              }
          }
      }
      return NULL;
  }
  
  static const struct nxm_field *
  nxm_field_by_name(const char *name, size_t len)
  {
      const struct nxm_field_index *nfi;
  
      nxm_init();
      HMAP_FOR_EACH_WITH_HASH (nfi, name_node, hash_bytes(name, len, 0),
                               &nxm_name_map) {
          if (strlen(nfi->nf.name) == len && !memcmp(nfi->nf.name, name, len)) {
              return &nfi->nf;
          }
      }
      return NULL;
  }
  
  static const struct nxm_field *
  nxm_field_by_mf_id(enum mf_field_id id, enum ofp_version version)
  {
      const struct nxm_field_index *nfi;
      const struct nxm_field *f;
  
      nxm_init();
  
      f = NULL;
      LIST_FOR_EACH (nfi, mf_node, &nxm_mf_map[id]) {
          if (!f || version >= nfi->nf.version) {
              f = &nfi->nf;
          }
      }
      return f;
  }
  