lib/learn.c

   1 /*
   2  * Copyright (c) 2011, 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 #include <config.h>
  18
  19 #include "learn.h"
  20
  21 #include "byte-order.h"
  22 #include "dynamic-string.h"
  23 #include "match.h"
  24 #include "meta-flow.h"
  25 #include "nx-match.h"
  26 #include "ofp-actions.h"
  27 #include "ofp-errors.h"
  28 #include "ofp-util.h"
  29 #include "ofpbuf.h"
  30 #include "openflow/openflow.h"
  31 #include "unaligned.h"
  32
  33 static ovs_be16
  34 get_be16(const void **pp)
  35 {
  36     const ovs_be16 *p = *pp;
  37     ovs_be16 value = *p;
  38     *pp = p + 1;
  39     return value;
  40 }
  41
  42 static ovs_be32
  43 get_be32(const void **pp)
  44 {
  45     const ovs_be32 *p = *pp;
  46     ovs_be32 value = get_unaligned_be32(p);
  47     *pp = p + 1;
  48     return value;
  49 }
  50
  51 static void
  52 get_subfield(int n_bits, const void **p, struct mf_subfield *sf)
  53 {
  54     sf->field = mf_from_nxm_header(ntohl(get_be32(p)));
  55     sf->ofs = ntohs(get_be16(p));
  56     sf->n_bits = n_bits;
  57 }
  58
  59 static unsigned int
  60 learn_min_len(uint16_t header)
  61 {
  62     int n_bits = header & NX_LEARN_N_BITS_MASK;
  63     int src_type = header & NX_LEARN_SRC_MASK;
  64     int dst_type = header & NX_LEARN_DST_MASK;
  65     unsigned int min_len;
  66
  67     min_len = 0;
  68     if (src_type == NX_LEARN_SRC_FIELD) {
  69         min_len += sizeof(ovs_be32); /* src_field */
  70         min_len += sizeof(ovs_be16); /* src_ofs */
  71     } else {
  72         min_len += DIV_ROUND_UP(n_bits, 16);
  73     }
  74     if (dst_type == NX_LEARN_DST_MATCH ||
  75         dst_type == NX_LEARN_DST_LOAD) {
  76         min_len += sizeof(ovs_be32); /* dst_field */
  77         min_len += sizeof(ovs_be16); /* dst_ofs */
  78     }
  79     return min_len;
  80 }
  81
  82 /* Converts 'nal' into a "struct ofpact_learn" and appends that struct to
  83  * 'ofpacts'.  Returns 0 if successful, otherwise an OFPERR_*. */
  84 enum ofperr
  85 learn_from_openflow(const struct nx_action_learn *nal, struct ofpbuf *ofpacts)
  86 {
  87     struct ofpact_learn *learn;
  88     const void *p, *end;
  89
  90     if (nal->pad) {
  91         return OFPERR_OFPBAC_BAD_ARGUMENT;
  92     }
  93
  94     learn = ofpact_put_LEARN(ofpacts);
  95
  96     learn->idle_timeout = ntohs(nal->idle_timeout);
  97     learn->hard_timeout = ntohs(nal->hard_timeout);
  98     learn->priority = ntohs(nal->priority);
  99     learn->cookie = ntohll(nal->cookie);
 100     learn->flags = ntohs(nal->flags);
 101     learn->table_id = nal->table_id;
 102     learn->fin_idle_timeout = ntohs(nal->fin_idle_timeout);
 103     learn->fin_hard_timeout = ntohs(nal->fin_hard_timeout);
 104
 105     if (learn->flags & ~OFPFF_SEND_FLOW_REM || learn->table_id == 0xff) {
 106         return OFPERR_OFPBAC_BAD_ARGUMENT;
 107     }
 108
 109     end = (char *) nal + ntohs(nal->len);
 110     for (p = nal + 1; p != end; ) {
 111         struct ofpact_learn_spec *spec;
 112         uint16_t header = ntohs(get_be16(&p));
 113
 114         if (!header) {
 115             break;
 116         }
 117
 118         spec = ofpbuf_put_zeros(ofpacts, sizeof *spec);
 119         learn = ofpacts->l2;
 120         learn->n_specs++;
 121
 122         spec->src_type = header & NX_LEARN_SRC_MASK;
 123         spec->dst_type = header & NX_LEARN_DST_MASK;
 124         spec->n_bits = header & NX_LEARN_N_BITS_MASK;
 125
 126         /* Check for valid src and dst type combination. */
 127         if (spec->dst_type == NX_LEARN_DST_MATCH ||
 128             spec->dst_type == NX_LEARN_DST_LOAD ||
 129             (spec->dst_type == NX_LEARN_DST_OUTPUT &&
 130              spec->src_type == NX_LEARN_SRC_FIELD)) {
 131             /* OK. */
 132         } else {
 133             return OFPERR_OFPBAC_BAD_ARGUMENT;
 134         }
 135
 136         /* Check that the arguments don't overrun the end of the action. */
 137         if ((char *) end - (char *) p < learn_min_len(header)) {
 138             return OFPERR_OFPBAC_BAD_LEN;
 139         }
 140
 141         /* Get the source. */
 142         if (spec->src_type == NX_LEARN_SRC_FIELD) {
 143             get_subfield(spec->n_bits, &p, &spec->src);
 144         } else {
 145             int p_bytes = 2 * DIV_ROUND_UP(spec->n_bits, 16);
 146
 147             bitwise_copy(p, p_bytes, 0,
 148                          &spec->src_imm, sizeof spec->src_imm, 0,
 149                          spec->n_bits);
 150             p = (const uint8_t *) p + p_bytes;
 151         }
 152
 153         /* Get the destination. */
 154         if (spec->dst_type == NX_LEARN_DST_MATCH ||
 155             spec->dst_type == NX_LEARN_DST_LOAD) {
 156             get_subfield(spec->n_bits, &p, &spec->dst);
 157         }
 158     }
 159     ofpact_update_len(ofpacts, &learn->ofpact);
 160
 161     if (!is_all_zeros(p, (char *) end - (char *) p)) {
 162         return OFPERR_OFPBAC_BAD_ARGUMENT;
 163     }
 164
 165     return 0;
 166 }
 167
 168 /* Checks that 'learn' is a valid action on 'flow'.  Returns 0 if it is valid,
 169  * otherwise an OFPERR_*. */
 170 enum ofperr
 171 learn_check(const struct ofpact_learn *learn, const struct flow *flow)
 172 {
 173     const struct ofpact_learn_spec *spec;
 174     struct match match;
 175
 176     match_init_catchall(&match);
 177     for (spec = learn->specs; spec < &learn->specs[learn->n_specs]; spec++) {
 178         enum ofperr error;
 179
 180         /* Check the source. */
 181         if (spec->src_type == NX_LEARN_SRC_FIELD) {
 182             error = mf_check_src(&spec->src, flow);
 183             if (error) {
 184                 return error;
 185             }
 186         }
 187
 188         /* Check the destination. */
 189         switch (spec->dst_type) {
 190         case NX_LEARN_DST_MATCH:
 191             error = mf_check_src(&spec->dst, &match.flow);
 192             if (error) {
 193                 return error;
 194             }
 195
 196             mf_write_subfield(&spec->dst, &spec->src_imm, &match);
 197             break;
 198
 199         case NX_LEARN_DST_LOAD:
 200             error = mf_check_dst(&spec->dst, &match.flow);
 201             if (error) {
 202                 return error;
 203             }
 204             break;
 205
 206         case NX_LEARN_DST_OUTPUT:
 207             /* Nothing to do. */
 208             break;
 209         }
 210     }
 211     return 0;
 212 }
 213
 214 static void
 215 put_be16(struct ofpbuf *b, ovs_be16 x)
 216 {
 217     ofpbuf_put(b, &x, sizeof x);
 218 }
 219
 220 static void
 221 put_be32(struct ofpbuf *b, ovs_be32 x)
 222 {
 223     ofpbuf_put(b, &x, sizeof x);
 224 }
 225
 226 static void
 227 put_u16(struct ofpbuf *b, uint16_t x)
 228 {
 229     put_be16(b, htons(x));
 230 }
 231
 232 static void
 233 put_u32(struct ofpbuf *b, uint32_t x)
 234 {
 235     put_be32(b, htonl(x));
 236 }
 237
 238 /* Converts 'learn' into a "struct nx_action_learn" and appends that action to
 239  * 'ofpacts'. */
 240 void
 241 learn_to_nxast(const struct ofpact_learn *learn, struct ofpbuf *openflow)
 242 {
 243     const struct ofpact_learn_spec *spec;
 244     struct nx_action_learn *nal;
 245     size_t start_ofs;
 246
 247     start_ofs = openflow->size;
 248     nal = ofputil_put_NXAST_LEARN(openflow);
 249     nal->idle_timeout = htons(learn->idle_timeout);
 250     nal->hard_timeout = htons(learn->hard_timeout);
 251     nal->fin_idle_timeout = htons(learn->fin_idle_timeout);
 252     nal->fin_hard_timeout = htons(learn->fin_hard_timeout);
 253     nal->priority = htons(learn->priority);
 254     nal->cookie = htonll(learn->cookie);
 255     nal->flags = htons(learn->flags);
 256     nal->table_id = learn->table_id;
 257
 258     for (spec = learn->specs; spec < &learn->specs[learn->n_specs]; spec++) {
 259         put_u16(openflow, spec->n_bits | spec->dst_type | spec->src_type);
 260
 261         if (spec->src_type == NX_LEARN_SRC_FIELD) {
 262             put_u32(openflow, spec->src.field->nxm_header);
 263             put_u16(openflow, spec->src.ofs);
 264         } else {
 265             size_t n_dst_bytes = 2 * DIV_ROUND_UP(spec->n_bits, 16);
 266             uint8_t *bits = ofpbuf_put_zeros(openflow, n_dst_bytes);
 267             bitwise_copy(&spec->src_imm, sizeof spec->src_imm, 0,
 268                          bits, n_dst_bytes, 0,
 269                          spec->n_bits);
 270         }
 271
 272         if (spec->dst_type == NX_LEARN_DST_MATCH ||
 273             spec->dst_type == NX_LEARN_DST_LOAD) {
 274             put_u32(openflow, spec->dst.field->nxm_header);
 275             put_u16(openflow, spec->dst.ofs);
 276         }
 277     }
 278
 279     if ((openflow->size - start_ofs) % 8) {
 280         ofpbuf_put_zeros(openflow, 8 - (openflow->size - start_ofs) % 8);
 281     }
 282
 283     nal = ofpbuf_at_assert(openflow, start_ofs, sizeof *nal);
 284     nal->len = htons(openflow->size - start_ofs);
 285 }
 286
 287 /* Composes 'fm' so that executing it will implement 'learn' given that the
 288  * packet being processed has 'flow' as its flow.
 289  *
 290  * Uses 'ofpacts' to store the flow mod's actions.  The caller must initialize
 291  * 'ofpacts' and retains ownership of it.  'fm->ofpacts' will point into the
 292  * 'ofpacts' buffer.
 293  *
 294  * The caller has to actually execute 'fm'. */
 295 void
 296 learn_execute(const struct ofpact_learn *learn, const struct flow *flow,
 297               struct ofputil_flow_mod *fm, struct ofpbuf *ofpacts)
 298 {
 299     const struct ofpact_learn_spec *spec;
 300
 301     match_init_catchall(&fm->match);
 302     fm->priority = learn->priority;
 303     fm->cookie = htonll(0);
 304     fm->cookie_mask = htonll(0);
 305     fm->new_cookie = htonll(learn->cookie);
 306     fm->table_id = learn->table_id;
 307     fm->command = OFPFC_MODIFY_STRICT;
 308     fm->idle_timeout = learn->idle_timeout;
 309     fm->hard_timeout = learn->hard_timeout;
 310     fm->buffer_id = UINT32_MAX;
 311     fm->out_port = OFPP_NONE;
 312     fm->flags = learn->flags;
 313     fm->ofpacts = NULL;
 314     fm->ofpacts_len = 0;
 315
 316     if (learn->fin_idle_timeout || learn->fin_hard_timeout) {
 317         struct ofpact_fin_timeout *oft;
 318
 319         oft = ofpact_put_FIN_TIMEOUT(ofpacts);
 320         oft->fin_idle_timeout = learn->fin_idle_timeout;
 321         oft->fin_hard_timeout = learn->fin_hard_timeout;
 322     }
 323
 324     for (spec = learn->specs; spec < &learn->specs[learn->n_specs]; spec++) {
 325         union mf_subvalue value;
 326         int chunk, ofs;
 327
 328         if (spec->src_type == NX_LEARN_SRC_FIELD) {
 329             mf_read_subfield(&spec->src, flow, &value);
 330         } else {
 331             value = spec->src_imm;
 332         }
 333
 334         switch (spec->dst_type) {
 335         case NX_LEARN_DST_MATCH:
 336             mf_write_subfield(&spec->dst, &value, &fm->match);
 337             break;
 338
 339         case NX_LEARN_DST_LOAD:
 340             for (ofs = 0; ofs < spec->n_bits; ofs += chunk) {
 341                 struct ofpact_reg_load *load;
 342
 343                 chunk = MIN(spec->n_bits - ofs, 64);
 344
 345                 load = ofpact_put_REG_LOAD(ofpacts);
 346                 load->dst.field = spec->dst.field;
 347                 load->dst.ofs = spec->dst.ofs + ofs;
 348                 load->dst.n_bits = chunk;
 349                 bitwise_copy(&value, sizeof value, ofs,
 350                              &load->subvalue, sizeof load->subvalue, 0,
 351                              chunk);
 352             }
 353             break;
 354
 355         case NX_LEARN_DST_OUTPUT:
 356             if (spec->n_bits <= 16
 357                 || is_all_zeros(value.u8, sizeof value - 2)) {
 358                 uint16_t port = ntohs(value.be16[7]);
 359
 360                 if (port < OFPP_MAX
 361                     || port == OFPP_IN_PORT
 362                     || port == OFPP_FLOOD
 363                     || port == OFPP_LOCAL
 364                     || port == OFPP_ALL) {
 365                     ofpact_put_OUTPUT(ofpacts)->port = port;
 366                 }
 367             }
 368             break;
 369         }
 370     }
 371     ofpact_pad(ofpacts);
 372
 373     fm->ofpacts = ofpacts->data;
 374     fm->ofpacts_len = ofpacts->size;
 375 }
 376
 377 static void
 378 learn_parse_load_immediate(const char *s, struct ofpact_learn_spec *spec)
 379 {
 380     const char *full_s = s;
 381     const char *arrow = strstr(s, "->");
 382     struct mf_subfield dst;
 383     union mf_subvalue imm;
 384
 385     memset(&imm, 0, sizeof imm);
 386     if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X') && arrow) {
 387         const char *in = arrow - 1;
 388         uint8_t *out = imm.u8 + sizeof imm.u8 - 1;
 389         int n = arrow - (s + 2);
 390         int i;
 391
 392         for (i = 0; i < n; i++) {
 393             int hexit = hexit_value(in[-i]);
 394             if (hexit < 0) {
 395                 ovs_fatal(0, "%s: bad hex digit in value", full_s);
 396             }
 397             out[-(i / 2)] |= i % 2 ? hexit << 4 : hexit;
 398         }
 399         s = arrow;
 400     } else {
 401         imm.be64[1] = htonll(strtoull(s, (char **) &s, 0));
 402     }
 403
 404     if (strncmp(s, "->", 2)) {
 405         ovs_fatal(0, "%s: missing `->' following value", full_s);
 406     }
 407     s += 2;
 408
 409     s = mf_parse_subfield(&dst, s);
 410     if (*s != '\0') {
 411         ovs_fatal(0, "%s: trailing garbage following destination", full_s);
 412     }
 413
 414     if (!bitwise_is_all_zeros(&imm, sizeof imm, dst.n_bits,
 415                               (8 * sizeof imm) - dst.n_bits)) {
 416         ovs_fatal(0, "%s: value does not fit into %u bits",
 417                   full_s, dst.n_bits);
 418     }
 419
 420     spec->n_bits = dst.n_bits;
 421     spec->src_type = NX_LEARN_SRC_IMMEDIATE;
 422     spec->src_imm = imm;
 423     spec->dst_type = NX_LEARN_DST_LOAD;
 424     spec->dst = dst;
 425 }
 426
 427 static void
 428 learn_parse_spec(const char *orig, char *name, char *value,
 429                  struct ofpact_learn_spec *spec)
 430 {
 431     if (mf_from_name(name)) {
 432         const struct mf_field *dst = mf_from_name(name);
 433         union mf_value imm;
 434         char *error;
 435
 436         error = mf_parse_value(dst, value, &imm);
 437         if (error) {
 438             ovs_fatal(0, "%s", error);
 439         }
 440
 441         spec->n_bits = dst->n_bits;
 442         spec->src_type = NX_LEARN_SRC_IMMEDIATE;
 443         memset(&spec->src_imm, 0, sizeof spec->src_imm);
 444         memcpy(&spec->src_imm.u8[sizeof spec->src_imm - dst->n_bytes],
 445                &imm, dst->n_bytes);
 446         spec->dst_type = NX_LEARN_DST_MATCH;
 447         spec->dst.field = dst;
 448         spec->dst.ofs = 0;
 449         spec->dst.n_bits = dst->n_bits;
 450     } else if (strchr(name, '[')) {
 451         /* Parse destination and check prerequisites. */
 452         if (mf_parse_subfield(&spec->dst, name)[0] != '\0') {
 453             ovs_fatal(0, "%s: syntax error after NXM field name `%s'",
 454                       orig, name);
 455         }
 456
 457         /* Parse source and check prerequisites. */
 458         if (value[0] != '\0') {
 459             if (mf_parse_subfield(&spec->src, value)[0] != '\0') {
 460                 ovs_fatal(0, "%s: syntax error after NXM field name `%s'",
 461                           orig, value);
 462             }
 463             if (spec->src.n_bits != spec->dst.n_bits) {
 464                 ovs_fatal(0, "%s: bit widths of %s (%u) and %s (%u) differ",
 465                           orig, name, spec->src.n_bits, value,
 466                           spec->dst.n_bits);
 467             }
 468         } else {
 469             spec->src = spec->dst;
 470         }
 471
 472         spec->n_bits = spec->src.n_bits;
 473         spec->src_type = NX_LEARN_SRC_FIELD;
 474         spec->dst_type = NX_LEARN_DST_MATCH;
 475     } else if (!strcmp(name, "load")) {
 476         if (value[strcspn(value, "[-")] == '-') {
 477             learn_parse_load_immediate(value, spec);
 478         } else {
 479             struct ofpact_reg_move move;
 480
 481             nxm_parse_reg_move(&move, value);
 482
 483             spec->n_bits = move.src.n_bits;
 484             spec->src_type = NX_LEARN_SRC_FIELD;
 485             spec->src = move.src;
 486             spec->dst_type = NX_LEARN_DST_LOAD;
 487             spec->dst = move.dst;
 488         }
 489     } else if (!strcmp(name, "output")) {
 490         if (mf_parse_subfield(&spec->src, value)[0] != '\0') {
 491             ovs_fatal(0, "%s: syntax error after NXM field name `%s'",
 492                       orig, name);
 493         }
 494
 495         spec->n_bits = spec->src.n_bits;
 496         spec->src_type = NX_LEARN_SRC_FIELD;
 497         spec->dst_type = NX_LEARN_DST_OUTPUT;
 498     } else {
 499         ovs_fatal(0, "%s: unknown keyword %s", orig, name);
 500     }
 501 }
 502
 503 /* Parses 'arg' as a set of arguments to the "learn" action and appends a
 504  * matching OFPACT_LEARN action to 'ofpacts'.  ovs-ofctl(8) describes the
 505  * format parsed.
 506  *
 507  * Prints an error on stderr and aborts the program if 'arg' syntax is invalid.
 508  *
 509  * If 'flow' is nonnull, then it should be the flow from a struct match that is
 510  * the matching rule for the learning action.  This helps to better validate
 511  * the action's arguments.
 512  *
 513  * Modifies 'arg'. */
 514 void
 515 learn_parse(char *arg, const struct flow *flow, struct ofpbuf *ofpacts)
 516 {
 517     char *orig = xstrdup(arg);
 518     char *name, *value;
 519
 520     struct ofpact_learn *learn;
 521     struct match match;
 522     enum ofperr error;
 523
 524     learn = ofpact_put_LEARN(ofpacts);
 525     learn->idle_timeout = OFP_FLOW_PERMANENT;
 526     learn->hard_timeout = OFP_FLOW_PERMANENT;
 527     learn->priority = OFP_DEFAULT_PRIORITY;
 528     learn->table_id = 1;
 529
 530     match_init_catchall(&match);
 531     while (ofputil_parse_key_value(&arg, &name, &value)) {
 532         if (!strcmp(name, "table")) {
 533             learn->table_id = atoi(value);
 534             if (learn->table_id == 255) {
 535                 ovs_fatal(0, "%s: table id 255 not valid for `learn' action",
 536                           orig);
 537             }
 538         } else if (!strcmp(name, "priority")) {
 539             learn->priority = atoi(value);
 540         } else if (!strcmp(name, "idle_timeout")) {
 541             learn->idle_timeout = atoi(value);
 542         } else if (!strcmp(name, "hard_timeout")) {
 543             learn->hard_timeout = atoi(value);
 544         } else if (!strcmp(name, "fin_idle_timeout")) {
 545             learn->fin_idle_timeout = atoi(value);
 546         } else if (!strcmp(name, "fin_hard_timeout")) {
 547             learn->fin_hard_timeout = atoi(value);
 548         } else if (!strcmp(name, "cookie")) {
 549             learn->cookie = strtoull(value, NULL, 0);
 550         } else {
 551             struct ofpact_learn_spec *spec;
 552
 553             spec = ofpbuf_put_zeros(ofpacts, sizeof *spec);
 554             learn = ofpacts->l2;
 555             learn->n_specs++;
 556
 557             learn_parse_spec(orig, name, value, spec);
 558
 559             /* Check prerequisites. */
 560             if (spec->src_type == NX_LEARN_SRC_FIELD
 561                 && flow && !mf_are_prereqs_ok(spec->src.field, flow)) {
 562                 ovs_fatal(0, "%s: cannot specify source field %s because "
 563                           "prerequisites are not satisfied",
 564                           orig, spec->src.field->name);
 565             }
 566             if ((spec->dst_type == NX_LEARN_DST_MATCH
 567                  || spec->dst_type == NX_LEARN_DST_LOAD)
 568                 && !mf_are_prereqs_ok(spec->dst.field, &match.flow)) {
 569                 ovs_fatal(0, "%s: cannot specify destination field %s because "
 570                           "prerequisites are not satisfied",
 571                           orig, spec->dst.field->name);
 572             }
 573
 574             /* Update 'match' to allow for satisfying destination
 575              * prerequisites. */
 576             if (spec->src_type == NX_LEARN_SRC_IMMEDIATE
 577                 && spec->dst_type == NX_LEARN_DST_MATCH) {
 578                 mf_write_subfield(&spec->dst, &spec->src_imm, &match);
 579             }
 580         }
 581     }
 582     ofpact_update_len(ofpacts, &learn->ofpact);
 583
 584     /* In theory the above should have caught any errors, but... */
 585     if (flow) {
 586         error = learn_check(learn, flow);
 587         if (error) {
 588             ovs_fatal(0, "%s: %s", orig, ofperr_to_string(error));
 589         }
 590     }
 591     free(orig);
 592 }
 593
 594 /* Appends a description of 'learn' to 's', in the format that ovs-ofctl(8)
 595  * describes. */
 596 void
 597 learn_format(const struct ofpact_learn *learn, struct ds *s)
 598 {
 599     const struct ofpact_learn_spec *spec;
 600     struct match match;
 601
 602     match_init_catchall(&match);
 603
 604     ds_put_format(s, "learn(table=%"PRIu8, learn->table_id);
 605     if (learn->idle_timeout != OFP_FLOW_PERMANENT) {
 606         ds_put_format(s, ",idle_timeout=%"PRIu16, learn->idle_timeout);
 607     }
 608     if (learn->hard_timeout != OFP_FLOW_PERMANENT) {
 609         ds_put_format(s, ",hard_timeout=%"PRIu16, learn->hard_timeout);
 610     }
 611     if (learn->fin_idle_timeout) {
 612         ds_put_format(s, ",fin_idle_timeout=%"PRIu16, learn->fin_idle_timeout);
 613     }
 614     if (learn->fin_hard_timeout) {
 615         ds_put_format(s, ",fin_hard_timeout=%"PRIu16, learn->fin_hard_timeout);
 616     }
 617     if (learn->priority != OFP_DEFAULT_PRIORITY) {
 618         ds_put_format(s, ",priority=%"PRIu16, learn->priority);
 619     }
 620     if (learn->flags & OFPFF_SEND_FLOW_REM) {
 621         ds_put_cstr(s, ",OFPFF_SEND_FLOW_REM");
 622     }
 623     if (learn->cookie != 0) {
 624         ds_put_format(s, ",cookie=%#"PRIx64, learn->cookie);
 625     }
 626
 627     for (spec = learn->specs; spec < &learn->specs[learn->n_specs]; spec++) {
 628         ds_put_char(s, ',');
 629
 630         switch (spec->src_type | spec->dst_type) {
 631         case NX_LEARN_SRC_IMMEDIATE | NX_LEARN_DST_MATCH:
 632             if (spec->dst.ofs == 0
 633                 && spec->dst.n_bits == spec->dst.field->n_bits) {
 634                 union mf_value value;
 635
 636                 memset(&value, 0, sizeof value);
 637                 bitwise_copy(&spec->src_imm, sizeof spec->src_imm, 0,
 638                              &value, spec->dst.field->n_bytes, 0,
 639                              spec->dst.field->n_bits);
 640                 ds_put_format(s, "%s=", spec->dst.field->name);
 641                 mf_format(spec->dst.field, &value, NULL, s);
 642             } else {
 643                 mf_format_subfield(&spec->dst, s);
 644                 ds_put_char(s, '=');
 645                 mf_format_subvalue(&spec->src_imm, s);
 646             }
 647             break;
 648
 649         case NX_LEARN_SRC_FIELD | NX_LEARN_DST_MATCH:
 650             mf_format_subfield(&spec->dst, s);
 651             if (spec->src.field != spec->dst.field ||
 652                 spec->src.ofs != spec->dst.ofs) {
 653                 ds_put_char(s, '=');
 654                 mf_format_subfield(&spec->src, s);
 655             }
 656             break;
 657
 658         case NX_LEARN_SRC_IMMEDIATE | NX_LEARN_DST_LOAD:
 659             ds_put_format(s, "load:");
 660             mf_format_subvalue(&spec->src_imm, s);
 661             ds_put_cstr(s, "->");
 662             mf_format_subfield(&spec->dst, s);
 663             break;
 664
 665         case NX_LEARN_SRC_FIELD | NX_LEARN_DST_LOAD:
 666             ds_put_cstr(s, "load:");
 667             mf_format_subfield(&spec->src, s);
 668             ds_put_cstr(s, "->");
 669             mf_format_subfield(&spec->dst, s);
 670             break;
 671
 672         case NX_LEARN_SRC_FIELD | NX_LEARN_DST_OUTPUT:
 673             ds_put_cstr(s, "output:");
 674             mf_format_subfield(&spec->src, s);
 675             break;
 676         }
 677     }
 678     ds_put_char(s, ')');
 679 }