lib/ofp-msgs.h

   1 /*
   2  * Copyright (c) 2012 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef OFP_MSGS_H
  18 #define OFP_MSGS_H 1
  19
  20 /* OpenFlow message headers abstraction.
  21  *
  22  * OpenFlow headers are unnecessarily complicated:
  23  *
  24  *   - Some messages with the same meaning were renumbered between 1.0 and 1.1.
  25  *
  26  *   - "Statistics" (aka multipart) messages have a different format from other
  27  *     messages.
  28  *
  29  *   - The 1.0 header for statistics messages is an odd number of 32-bit words
  30  *     long, leaving 64-bit quantities in the body misaligned.  The 1.1 header
  31  *     for statistics added a padding word to fix this misalignment, although
  32  *     many statistic message bodies did not change.
  33  *
  34  *   - Vendor-defined messages have an additional header but no standard way to
  35  *     distinguish individual types of message within a given vendor.
  36  *
  37  * This file attempts to abstract out the differences between the various forms
  38  * of headers.
  39  */
  40
  41 #include "openvswitch/types.h"
  42 #include "ofp-errors.h"
  43 #include "util.h"
  44
  45 struct list;
  46 \f
  47 /* Raw identifiers for OpenFlow messages.
  48  *
  49  * Some OpenFlow messages with similar meanings have multiple variants across
  50  * OpenFlow versions or vendor extensions.  Each variant has a different
  51  * OFPRAW_* enumeration constant.  More specifically, if two messages have
  52  * different types, different numbers, or different arguments, then they must
  53  * have different OFPRAW_* values.
  54  *
  55  * The comments here must follow a stylized form because the "extract-ofp-msgs"
  56  * program parses them at build time to generate data tables.  The syntax of
  57  * each comment is:
  58  *
  59  *    type versions (number): arguments.
  60  *
  61  * where the syntax of each part is:
  62  *
  63  *    - type: One of OFPT (standard OpenFlow message), OFPST (standard OpenFlow
  64  *      statistics message), NXT (Nicira extension message), or NXST (Nicira
  65  *      extension statistics message).
  66  *
  67  *      As new vendors implement extensions it will make sense to expand the
  68  *      dictionary of possible types.
  69  *
  70  *    - versions: The OpenFlow version or versions in which this message is
  71  *      supported, e.g. "1.0" or "1.1" or "1.0+".
  72  *
  73  *    - number:
  74  *         For OFPT, the 'type' in struct ofp_header.
  75  *         For OFPST, the 'type' in struct ofp_stats_msg or ofp11_stats_msg.
  76  *         For NXT, the 'subtype' in struct nicira_header.
  77  *         For NXST, the 'subtype' in struct nicira10_stats_msg or
  78  *           nicira11_stats_msg.
  79  *
  80  *    - arguments: The types of data that follow the OpenFlow headers (the
  81  *      message "body").  This can be "void" if the message has no body.
  82  *      Otherwise, it should be a comma-separated sequence of C types.  The
  83  *      last type in the sequence can end with [] if the body ends in a
  84  *      variable-length sequence.
  85  *
  86  *      The arguments are used to validate the lengths of messages when a
  87  *      header is parsed.  Any message whose length isn't valid as a length of
  88  *      the specified types will be rejected with OFPERR_OFPBRC_BAD_LEN.
  89  *
  90  *      A few OpenFlow messages, such as OFPT_PACKET_IN, intentionally end with
  91  *      only part of a structure, up to some specified member.  The syntax "up
  92  *      to <member>" indicates this, e.g. "struct ofp11_packet_in up to data".
  93  */
  94 enum ofpraw {
  95 /* Standard messages. */
  96
  97     /* OFPT 1.0+ (0): uint8_t[]. */
  98     OFPRAW_OFPT_HELLO,
  99
 100     /* OFPT 1.0+ (1): struct ofp_error_msg, uint8_t[]. */
 101     OFPRAW_OFPT_ERROR,
 102
 103     /* OFPT 1.0+ (2): uint8_t[]. */
 104     OFPRAW_OFPT_ECHO_REQUEST,
 105
 106     /* OFPT 1.0+ (3): uint8_t[]. */
 107     OFPRAW_OFPT_ECHO_REPLY,
 108
 109     /* OFPT 1.0+ (5): void. */
 110     OFPRAW_OFPT_FEATURES_REQUEST,
 111
 112     /* OFPT 1.0 (6): struct ofp_switch_features, struct ofp10_phy_port[]. */
 113     OFPRAW_OFPT10_FEATURES_REPLY,
 114     /* OFPT 1.1+ (6): struct ofp_switch_features, struct ofp11_port[]. */
 115     OFPRAW_OFPT11_FEATURES_REPLY,
 116
 117     /* OFPT 1.0+ (7): void. */
 118     OFPRAW_OFPT_GET_CONFIG_REQUEST,
 119
 120     /* OFPT 1.0+ (8): struct ofp_switch_config. */
 121     OFPRAW_OFPT_GET_CONFIG_REPLY,
 122
 123     /* OFPT 1.0+ (9): struct ofp_switch_config. */
 124     OFPRAW_OFPT_SET_CONFIG,
 125
 126     /* OFPT 1.0 (10): struct ofp_packet_in up to data, uint8_t[]. */
 127     OFPRAW_OFPT10_PACKET_IN,
 128     /* OFPT 1.1 (10): struct ofp11_packet_in up to data, uint8_t[]. */
 129     OFPRAW_OFPT11_PACKET_IN,
 130     /* OFPT 1.2 (10): struct ofp12_packet_in, uint8_t[]. */
 131     OFPRAW_OFPT12_PACKET_IN,
 132     /* NXT 1.0+ (17): struct nx_packet_in, uint8_t[]. */
 133     OFPRAW_NXT_PACKET_IN,
 134
 135     /* OFPT 1.0 (11): struct ofp_flow_removed. */
 136     OFPRAW_OFPT10_FLOW_REMOVED,
 137     /* OFPT 1.1+ (11): struct ofp11_flow_removed, uint8_t[8][]. */
 138     OFPRAW_OFPT11_FLOW_REMOVED,
 139     /* NXT 1.0+ (14): struct nx_flow_removed, uint8_t[8][]. */
 140     OFPRAW_NXT_FLOW_REMOVED,
 141
 142     /* OFPT 1.0 (12): struct ofp_port_status, struct ofp10_phy_port. */
 143     OFPRAW_OFPT10_PORT_STATUS,
 144     /* OFPT 1.1+ (12): struct ofp_port_status, struct ofp11_port. */
 145     OFPRAW_OFPT11_PORT_STATUS,
 146
 147     /* OFPT 1.0 (13): struct ofp_packet_out, uint8_t[]. */
 148     OFPRAW_OFPT10_PACKET_OUT,
 149     /* OFPT 1.1+ (13): struct ofp11_packet_out, uint8_t[]. */
 150     OFPRAW_OFPT11_PACKET_OUT,
 151
 152     /* OFPT 1.0 (14): struct ofp10_flow_mod, struct ofp_action_header[]. */
 153     OFPRAW_OFPT10_FLOW_MOD,
 154     /* OFPT 1.1+ (14): struct ofp11_flow_mod, struct ofp11_instruction[]. */
 155     OFPRAW_OFPT11_FLOW_MOD,
 156     /* NXT 1.0+ (13): struct nx_flow_mod, uint8_t[8][]. */
 157     OFPRAW_NXT_FLOW_MOD,
 158
 159     /* OFPT 1.0 (15): struct ofp10_port_mod. */
 160     OFPRAW_OFPT10_PORT_MOD,
 161     /* OFPT 1.1+ (16): struct ofp11_port_mod. */
 162     OFPRAW_OFPT11_PORT_MOD,
 163
 164     /* OFPT 1.0 (18): void. */
 165     OFPRAW_OFPT10_BARRIER_REQUEST,
 166     /* OFPT 1.1 (20): void. */
 167     OFPRAW_OFPT11_BARRIER_REQUEST,
 168
 169     /* OFPT 1.0 (19): void. */
 170     OFPRAW_OFPT10_BARRIER_REPLY,
 171     /* OFPT 1.1 (21): void. */
 172     OFPRAW_OFPT11_BARRIER_REPLY,
 173
 174 /* Standard statistics. */
 175
 176     /* OFPST 1.0+ (0): void. */
 177     OFPRAW_OFPST_DESC_REQUEST,
 178
 179     /* OFPST 1.0+ (0): struct ofp_desc_stats. */
 180     OFPRAW_OFPST_DESC_REPLY,
 181
 182     /* OFPST 1.0 (1): struct ofp10_flow_stats_request. */
 183     OFPRAW_OFPST_FLOW_REQUEST,
 184     /* NXST 1.0 (0): struct nx_flow_stats_request, uint8_t[8][]. */
 185     OFPRAW_NXST_FLOW_REQUEST,
 186
 187     /* OFPST 1.0 (1): uint8_t[]. */
 188     OFPRAW_OFPST_FLOW_REPLY,
 189     /* NXST 1.0 (0): uint8_t[]. */
 190     OFPRAW_NXST_FLOW_REPLY,
 191
 192     /* OFPST 1.0 (2): struct ofp10_flow_stats_request. */
 193     OFPRAW_OFPST_AGGREGATE_REQUEST,
 194     /* NXST 1.0 (1): struct nx_flow_stats_request, uint8_t[8][]. */
 195     OFPRAW_NXST_AGGREGATE_REQUEST,
 196
 197     /* OFPST 1.0 (2): struct ofp_aggregate_stats_reply. */
 198     OFPRAW_OFPST_AGGREGATE_REPLY,
 199     /* NXST 1.0 (1): struct ofp_aggregate_stats_reply. */
 200     OFPRAW_NXST_AGGREGATE_REPLY,
 201
 202     /* OFPST 1.0 (3): void. */
 203     OFPRAW_OFPST_TABLE_REQUEST,
 204
 205     /* OFPST 1.0 (3): struct ofp10_table_stats[]. */
 206     OFPRAW_OFPST_TABLE_REPLY,
 207
 208     /* OFPST 1.0 (4): struct ofp10_port_stats_request. */
 209     OFPRAW_OFPST_PORT_REQUEST,
 210
 211     /* OFPST 1.0 (4): struct ofp10_port_stats[]. */
 212     OFPRAW_OFPST_PORT_REPLY,
 213
 214     /* OFPST 1.0 (5): struct ofp10_queue_stats_request. */
 215     OFPRAW_OFPST_QUEUE_REQUEST,
 216
 217     /* OFPST 1.0 (5): struct ofp10_queue_stats[]. */
 218     OFPRAW_OFPST_QUEUE_REPLY,
 219
 220     /* OFPST 1.0 (13): void. */
 221     OFPRAW_OFPST_PORT_DESC_REQUEST,
 222
 223     /* OFPST 1.0 (13): struct ofp10_phy_port[]. */
 224     OFPRAW_OFPST_PORT_DESC_REPLY,
 225
 226 /* Nicira extension messages.
 227  *
 228  * Nicira extensions that correspond to standard OpenFlow messages are listed
 229  * alongside the standard versions above. */
 230
 231     /* NXT 1.0+ (10): struct nx_role_request. */
 232     OFPRAW_NXT_ROLE_REQUEST,
 233
 234     /* NXT 1.0+ (11): struct nx_role_request. */
 235     OFPRAW_NXT_ROLE_REPLY,
 236
 237     /* NXT 1.0+ (12): struct nx_set_flow_format. */
 238     OFPRAW_NXT_SET_FLOW_FORMAT,
 239
 240     /* NXT 1.0+ (15): struct nx_flow_mod_table_id. */
 241     OFPRAW_NXT_FLOW_MOD_TABLE_ID,
 242
 243     /* NXT 1.0+ (16): struct nx_set_packet_in_format. */
 244     OFPRAW_NXT_SET_PACKET_IN_FORMAT,
 245
 246     /* NXT 1.0+ (18): void. */
 247     OFPRAW_NXT_FLOW_AGE,
 248
 249     /* NXT 1.0+ (19): struct nx_async_config. */
 250     OFPRAW_NXT_SET_ASYNC_CONFIG,
 251
 252     /* NXT 1.0+ (20): struct nx_controller_id. */
 253     OFPRAW_NXT_SET_CONTROLLER_ID,
 254
 255     /* NXT 1.0+ (21): struct nx_flow_monitor_cancel. */
 256     OFPRAW_NXT_FLOW_MONITOR_CANCEL,
 257
 258     /* NXT 1.0+ (22): void. */
 259     OFPRAW_NXT_FLOW_MONITOR_PAUSED,
 260
 261     /* NXT 1.0+ (23): void. */
 262     OFPRAW_NXT_FLOW_MONITOR_RESUMED,
 263
 264 /* Nicira extension statistics.
 265  *
 266  * Nicira extension statistics that correspond to standard OpenFlow statistics
 267  * are listed alongside the standard versions above. */
 268
 269     /* NXST 1.0 (2): uint8_t[8][]. */
 270     OFPRAW_NXST_FLOW_MONITOR_REQUEST,
 271
 272     /* NXST 1.0 (2): uint8_t[8][]. */
 273     OFPRAW_NXST_FLOW_MONITOR_REPLY,
 274 };
 275
 276 /* Decoding messages into OFPRAW_* values. */
 277 enum ofperr ofpraw_decode(enum ofpraw *, const struct ofp_header *);
 278 enum ofperr ofpraw_pull(enum ofpraw *, struct ofpbuf *);
 279 enum ofpraw ofpraw_pull_assert(struct ofpbuf *);
 280
 281 enum ofperr ofpraw_decode_partial(enum ofpraw *,
 282                                   const struct ofp_header *, size_t length);
 283
 284 /* Encoding messages using OFPRAW_* values. */
 285 struct ofpbuf *ofpraw_alloc(enum ofpraw, uint8_t ofp_version,
 286                             size_t extra_tailroom);
 287 struct ofpbuf *ofpraw_alloc_xid(enum ofpraw, uint8_t ofp_version,
 288                                 ovs_be32 xid, size_t extra_tailroom);
 289 struct ofpbuf *ofpraw_alloc_reply(enum ofpraw,
 290                                   const struct ofp_header *request,
 291                                   size_t extra_tailroom);
 292 struct ofpbuf *ofpraw_alloc_stats_reply(const struct ofp_header *request,
 293                                         size_t extra_tailroom);
 294
 295 void ofpraw_put(enum ofpraw, uint8_t ofp_version, struct ofpbuf *);
 296 void ofpraw_put_xid(enum ofpraw, uint8_t ofp_version, ovs_be32 xid,
 297                     struct ofpbuf *);
 298 void ofpraw_put_reply(enum ofpraw, const struct ofp_header *request,
 299                       struct ofpbuf *);
 300 void ofpraw_put_stats_reply(const struct ofp_header *request, struct ofpbuf *);
 301
 302 /* Information about OFPRAW_* values. */
 303 const char *ofpraw_get_name(enum ofpraw);
 304 enum ofpraw ofpraw_stats_request_to_reply(enum ofpraw, uint8_t version);
 305 \f
 306 /* Semantic identifiers for OpenFlow messages.
 307  *
 308  * Each OFPTYPE_* enumeration constant represents one or more concrete format
 309  * of OpenFlow message.  When two variants of a message have essentially the
 310  * same meaning, they are assigned a single OFPTYPE_* value.
 311  *
 312  * The comments here must follow a stylized form because the "extract-ofp-msgs"
 313  * program parses them at build time to generate data tables.  The format is
 314  * simply to list each OFPRAW_* enumeration constant for a given OFPTYPE_*,
 315  * each followed by a period. */
 316 enum ofptype {
 317     /* Immutable messages. */
 318     OFPTYPE_HELLO,               /* OFPRAW_OFPT_HELLO. */
 319     OFPTYPE_ERROR,               /* OFPRAW_OFPT_ERROR. */
 320     OFPTYPE_ECHO_REQUEST,        /* OFPRAW_OFPT_ECHO_REQUEST. */
 321     OFPTYPE_ECHO_REPLY,          /* OFPRAW_OFPT_ECHO_REPLY. */
 322
 323     /* Switch configuration messages. */
 324     OFPTYPE_FEATURES_REQUEST,    /* OFPRAW_OFPT_FEATURES_REQUEST. */
 325     OFPTYPE_FEATURES_REPLY,      /* OFPRAW_OFPT10_FEATURES_REPLY.
 326                                   * OFPRAW_OFPT11_FEATURES_REPLY. */
 327     OFPTYPE_GET_CONFIG_REQUEST,  /* OFPRAW_OFPT_GET_CONFIG_REQUEST. */
 328     OFPTYPE_GET_CONFIG_REPLY,    /* OFPRAW_OFPT_GET_CONFIG_REPLY. */
 329     OFPTYPE_SET_CONFIG,          /* OFPRAW_OFPT_SET_CONFIG. */
 330
 331     /* Asynchronous messages. */
 332     OFPTYPE_PACKET_IN,           /* OFPRAW_OFPT10_PACKET_IN.
 333                                   * OFPRAW_OFPT11_PACKET_IN.
 334                                   * OFPRAW_OFPT12_PACKET_IN.
 335                                   * OFPRAW_NXT_PACKET_IN. */
 336     OFPTYPE_FLOW_REMOVED,        /* OFPRAW_OFPT10_FLOW_REMOVED.
 337                                   * OFPRAW_OFPT11_FLOW_REMOVED.
 338                                   * OFPRAW_NXT_FLOW_REMOVED. */
 339     OFPTYPE_PORT_STATUS,         /* OFPRAW_OFPT10_PORT_STATUS.
 340                                   * OFPRAW_OFPT11_PORT_STATUS. */
 341
 342     /* Controller command messages. */
 343     OFPTYPE_PACKET_OUT,          /* OFPRAW_OFPT10_PACKET_OUT.
 344                                   * OFPRAW_OFPT11_PACKET_OUT. */
 345     OFPTYPE_FLOW_MOD,            /* OFPRAW_OFPT10_FLOW_MOD.
 346                                   * OFPRAW_OFPT11_FLOW_MOD.
 347                                   * OFPRAW_NXT_FLOW_MOD. */
 348     OFPTYPE_PORT_MOD,            /* OFPRAW_OFPT10_PORT_MOD.
 349                                   * OFPRAW_OFPT11_PORT_MOD. */
 350
 351     /* Barrier messages. */
 352     OFPTYPE_BARRIER_REQUEST,     /* OFPRAW_OFPT10_BARRIER_REQUEST.
 353                                   * OFPRAW_OFPT11_BARRIER_REQUEST. */
 354     OFPTYPE_BARRIER_REPLY,       /* OFPRAW_OFPT10_BARRIER_REPLY.
 355                                   * OFPRAW_OFPT11_BARRIER_REPLY. */
 356
 357     /* Statistics. */
 358     OFPTYPE_DESC_STATS_REQUEST,      /* OFPRAW_OFPST_DESC_REQUEST. */
 359     OFPTYPE_DESC_STATS_REPLY,        /* OFPRAW_OFPST_DESC_REPLY. */
 360     OFPTYPE_FLOW_STATS_REQUEST,      /* OFPRAW_OFPST_FLOW_REQUEST.
 361                                       * OFPRAW_NXST_FLOW_REQUEST. */
 362     OFPTYPE_FLOW_STATS_REPLY,        /* OFPRAW_OFPST_FLOW_REPLY.
 363                                       * OFPRAW_NXST_FLOW_REPLY. */
 364     OFPTYPE_AGGREGATE_STATS_REQUEST, /* OFPRAW_OFPST_AGGREGATE_REQUEST.
 365                                       * OFPRAW_NXST_AGGREGATE_REQUEST. */
 366     OFPTYPE_AGGREGATE_STATS_REPLY,   /* OFPRAW_OFPST_AGGREGATE_REPLY.
 367                                       * OFPRAW_NXST_AGGREGATE_REPLY. */
 368     OFPTYPE_TABLE_STATS_REQUEST,     /* OFPRAW_OFPST_TABLE_REQUEST. */
 369     OFPTYPE_TABLE_STATS_REPLY,       /* OFPRAW_OFPST_TABLE_REPLY. */
 370     OFPTYPE_PORT_STATS_REQUEST,      /* OFPRAW_OFPST_PORT_REQUEST. */
 371     OFPTYPE_PORT_STATS_REPLY,        /* OFPRAW_OFPST_PORT_REPLY. */
 372     OFPTYPE_QUEUE_STATS_REQUEST,     /* OFPRAW_OFPST_QUEUE_REQUEST. */
 373     OFPTYPE_QUEUE_STATS_REPLY,       /* OFPRAW_OFPST_QUEUE_REPLY. */
 374     OFPTYPE_PORT_DESC_STATS_REQUEST, /* OFPRAW_OFPST_PORT_DESC_REQUEST. */
 375     OFPTYPE_PORT_DESC_STATS_REPLY,   /* OFPRAW_OFPST_PORT_DESC_REPLY. */
 376
 377     /* Nicira extensions. */
 378     OFPTYPE_ROLE_REQUEST,         /* OFPRAW_NXT_ROLE_REQUEST. */
 379     OFPTYPE_ROLE_REPLY,           /* OFPRAW_NXT_ROLE_REPLY. */
 380     OFPTYPE_SET_FLOW_FORMAT,      /* OFPRAW_NXT_SET_FLOW_FORMAT. */
 381     OFPTYPE_FLOW_MOD_TABLE_ID,    /* OFPRAW_NXT_FLOW_MOD_TABLE_ID. */
 382     OFPTYPE_SET_PACKET_IN_FORMAT, /* OFPRAW_NXT_SET_PACKET_IN_FORMAT. */
 383     OFPTYPE_FLOW_AGE,             /* OFPRAW_NXT_FLOW_AGE. */
 384     OFPTYPE_SET_ASYNC_CONFIG,     /* OFPRAW_NXT_SET_ASYNC_CONFIG. */
 385     OFPTYPE_SET_CONTROLLER_ID,    /* OFPRAW_NXT_SET_CONTROLLER_ID. */
 386
 387     /* Flow monitor extension. */
 388     OFPTYPE_FLOW_MONITOR_STATS_REQUEST, /* OFPRAW_NXST_FLOW_MONITOR_REQUEST. */
 389     OFPTYPE_FLOW_MONITOR_STATS_REPLY,   /* OFPRAW_NXST_FLOW_MONITOR_REPLY. */
 390     OFPTYPE_FLOW_MONITOR_CANCEL,        /* OFPRAW_NXT_FLOW_MONITOR_CANCEL. */
 391     OFPTYPE_FLOW_MONITOR_PAUSED,        /* OFPRAW_NXT_FLOW_MONITOR_PAUSED. */
 392     OFPTYPE_FLOW_MONITOR_RESUMED,       /* OFPRAW_NXT_FLOW_MONITOR_RESUMED. */
 393 };
 394
 395 /* Decoding messages into OFPTYPE_* values. */
 396 enum ofperr ofptype_decode(enum ofptype *, const struct ofp_header *);
 397 enum ofperr ofptype_pull(enum ofptype *, struct ofpbuf *);
 398 enum ofptype ofptype_from_ofpraw(enum ofpraw);
 399 \f
 400 /* OpenFlow message properties. */
 401 void ofpmsg_update_length(struct ofpbuf *);
 402 const void *ofpmsg_body(const struct ofp_header *);
 403 \f
 404 /* Multipart messages (aka "statistics").
 405  *
 406  * Individual OpenFlow messages are limited to 64 kB in size, but some messages
 407  * need to be longer.  Therefore, multipart messages allow a longer message to
 408  * be divided into multiple parts at some convenient boundary.  For example,
 409  * limiting the response to a "flow dump" request to 64 kB would unreasonably
 410  * limit the maximum number of flows in an OpenFlow switch, so a "flow dump" is
 411  * expressed as a multipart request/reply pair, with the reply broken into
 412  * pieces between flows.
 413  *
 414  * Multipart messages always consist of a request/reply pair.
 415  *
 416  * In OpenFlow 1.0, 1.1, and 1.2, requests must always fit in a single message,
 417  * that is, only a multipart reply may have more than one part.  OpenFlow 1.3
 418  * adds one multipart request.  This code does not yet support multipart
 419  * requests. */
 420
 421 /* Encoding multipart replies.
 422  *
 423  * These functions are useful for multipart replies that might really require
 424  * more than one message.  A multipart message that is known in advance to fit
 425  * within 64 kB doesn't need any special treatment, so you might as well use
 426  * the ofpraw_alloc_*() functions.
 427  *
 428  * These functions work with a "struct list" of "struct ofpbuf"s, each of
 429  * which represents one part of a multipart message. */
 430 void ofpmp_init(struct list *, const struct ofp_header *request);
 431 struct ofpbuf *ofpmp_reserve(struct list *, size_t len);
 432 void *ofpmp_append(struct list *, size_t len);
 433 void ofpmp_postappend(struct list *, size_t start_ofs);
 434
 435 /* Decoding multipart replies. */
 436 uint16_t ofpmp_flags(const struct ofp_header *);
 437 bool ofpmp_more(const struct ofp_header *);
 438
 439 #endif /* ofp-msgs.h */