lib/jsonrpc.c

   1 /*
   2  * Copyright (c) 2009, 2010, 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 "jsonrpc.h"
  20
  21 #include <assert.h>
  22 #include <errno.h>
  23
  24 #include "byteq.h"
  25 #include "dynamic-string.h"
  26 #include "fatal-signal.h"
  27 #include "json.h"
  28 #include "list.h"
  29 #include "ofpbuf.h"
  30 #include "poll-loop.h"
  31 #include "reconnect.h"
  32 #include "stream.h"
  33 #include "timeval.h"
  34 #include "vlog.h"
  35
  36 VLOG_DEFINE_THIS_MODULE(jsonrpc);
  37 \f
  38 struct jsonrpc {
  39     struct stream *stream;
  40     char *name;
  41     int status;
  42
  43     /* Input. */
  44     struct byteq input;
  45     struct json_parser *parser;
  46     struct jsonrpc_msg *received;
  47
  48     /* Output. */
  49     struct list output;         /* Contains "struct ofpbuf"s. */
  50     size_t backlog;
  51 };
  52
  53 /* Rate limit for error messages. */
  54 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5);
  55
  56 static void jsonrpc_received(struct jsonrpc *);
  57 static void jsonrpc_cleanup(struct jsonrpc *);
  58 static void jsonrpc_error(struct jsonrpc *, int error);
  59
  60 /* This is just the same as stream_open() except that it uses the default
  61  * JSONRPC ports if none is specified. */
  62 int
  63 jsonrpc_stream_open(const char *name, struct stream **streamp, uint8_t dscp)
  64 {
  65     return stream_open_with_default_ports(name, JSONRPC_TCP_PORT,
  66                                           JSONRPC_SSL_PORT, streamp,
  67                                           dscp);
  68 }
  69
  70 /* This is just the same as pstream_open() except that it uses the default
  71  * JSONRPC ports if none is specified. */
  72 int
  73 jsonrpc_pstream_open(const char *name, struct pstream **pstreamp, uint8_t dscp)
  74 {
  75     return pstream_open_with_default_ports(name, JSONRPC_TCP_PORT,
  76                                            JSONRPC_SSL_PORT, pstreamp, dscp);
  77 }
  78
  79 /* Returns a new JSON-RPC stream that uses 'stream' for input and output.  The
  80  * new jsonrpc object takes ownership of 'stream'. */
  81 struct jsonrpc *
  82 jsonrpc_open(struct stream *stream)
  83 {
  84     struct jsonrpc *rpc;
  85
  86     assert(stream != NULL);
  87
  88     rpc = xzalloc(sizeof *rpc);
  89     rpc->name = xstrdup(stream_get_name(stream));
  90     rpc->stream = stream;
  91     byteq_init(&rpc->input);
  92     list_init(&rpc->output);
  93
  94     return rpc;
  95 }
  96
  97 /* Destroys 'rpc', closing the stream on which it is based, and frees its
  98  * memory. */
  99 void
 100 jsonrpc_close(struct jsonrpc *rpc)
 101 {
 102     if (rpc) {
 103         jsonrpc_cleanup(rpc);
 104         free(rpc->name);
 105         free(rpc);
 106     }
 107 }
 108
 109 /* Performs periodic maintenance on 'rpc', such as flushing output buffers. */
 110 void
 111 jsonrpc_run(struct jsonrpc *rpc)
 112 {
 113     if (rpc->status) {
 114         return;
 115     }
 116
 117     stream_run(rpc->stream);
 118     while (!list_is_empty(&rpc->output)) {
 119         struct ofpbuf *buf = ofpbuf_from_list(rpc->output.next);
 120         int retval;
 121
 122         retval = stream_send(rpc->stream, buf->data, buf->size);
 123         if (retval >= 0) {
 124             rpc->backlog -= retval;
 125             ofpbuf_pull(buf, retval);
 126             if (!buf->size) {
 127                 list_remove(&buf->list_node);
 128                 ofpbuf_delete(buf);
 129             }
 130         } else {
 131             if (retval != -EAGAIN) {
 132                 VLOG_WARN_RL(&rl, "%s: send error: %s",
 133                              rpc->name, strerror(-retval));
 134                 jsonrpc_error(rpc, -retval);
 135             }
 136             break;
 137         }
 138     }
 139 }
 140
 141 /* Arranges for the poll loop to wake up when 'rpc' needs to perform
 142  * maintenance activities. */
 143 void
 144 jsonrpc_wait(struct jsonrpc *rpc)
 145 {
 146     if (!rpc->status) {
 147         stream_run_wait(rpc->stream);
 148         if (!list_is_empty(&rpc->output)) {
 149             stream_send_wait(rpc->stream);
 150         }
 151     }
 152 }
 153
 154 /*
 155  * Returns the current status of 'rpc'.  The possible return values are:
 156  * - 0: no error yet
 157  * - >0: errno value
 158  * - EOF: end of file (remote end closed connection; not necessarily an error).
 159  *
 160  * When this functions nonzero, 'rpc' is effectively out of commission.  'rpc'
 161  * will not receive any more messages and any further messages that one
 162  * attempts to send with 'rpc' will be discarded.  The caller can keep 'rpc'
 163  * around as long as it wants, but it's not going to provide any more useful
 164  * services.
 165  */
 166 int
 167 jsonrpc_get_status(const struct jsonrpc *rpc)
 168 {
 169     return rpc->status;
 170 }
 171
 172 /* Returns the number of bytes buffered by 'rpc' to be written to the
 173  * underlying stream.  Always returns 0 if 'rpc' has encountered an error or if
 174  * the remote end closed the connection. */
 175 size_t
 176 jsonrpc_get_backlog(const struct jsonrpc *rpc)
 177 {
 178     return rpc->status ? 0 : rpc->backlog;
 179 }
 180
 181 /* Returns the number of bytes that have been received on 'rpc''s underlying
 182  * stream.  (The value wraps around if it exceeds UINT_MAX.) */
 183 unsigned int
 184 jsonrpc_get_received_bytes(const struct jsonrpc *rpc)
 185 {
 186     return rpc->input.head;
 187 }
 188
 189 /* Returns 'rpc''s name, that is, the name returned by stream_get_name() for
 190  * the stream underlying 'rpc' when 'rpc' was created. */
 191 const char *
 192 jsonrpc_get_name(const struct jsonrpc *rpc)
 193 {
 194     return rpc->name;
 195 }
 196
 197 static void
 198 jsonrpc_log_msg(const struct jsonrpc *rpc, const char *title,
 199                 const struct jsonrpc_msg *msg)
 200 {
 201     if (VLOG_IS_DBG_ENABLED()) {
 202         struct ds s = DS_EMPTY_INITIALIZER;
 203         if (msg->method) {
 204             ds_put_format(&s, ", method=\"%s\"", msg->method);
 205         }
 206         if (msg->params) {
 207             ds_put_cstr(&s, ", params=");
 208             json_to_ds(msg->params, 0, &s);
 209         }
 210         if (msg->result) {
 211             ds_put_cstr(&s, ", result=");
 212             json_to_ds(msg->result, 0, &s);
 213         }
 214         if (msg->error) {
 215             ds_put_cstr(&s, ", error=");
 216             json_to_ds(msg->error, 0, &s);
 217         }
 218         if (msg->id) {
 219             ds_put_cstr(&s, ", id=");
 220             json_to_ds(msg->id, 0, &s);
 221         }
 222         VLOG_DBG("%s: %s %s%s", rpc->name, title,
 223                  jsonrpc_msg_type_to_string(msg->type), ds_cstr(&s));
 224         ds_destroy(&s);
 225     }
 226 }
 227
 228 /* Schedules 'msg' to be sent on 'rpc' and returns 'rpc''s status (as with
 229  * jsonrpc_get_status()).
 230  *
 231  * If 'msg' cannot be sent immediately, it is appended to a buffer.  The caller
 232  * is responsible for ensuring that the amount of buffered data is somehow
 233  * limited.  (jsonrpc_get_backlog() returns the amount of data currently
 234  * buffered in 'rpc'.)
 235  *
 236  * Always takes ownership of 'msg', regardless of success. */
 237 int
 238 jsonrpc_send(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
 239 {
 240     struct ofpbuf *buf;
 241     struct json *json;
 242     size_t length;
 243     char *s;
 244
 245     if (rpc->status) {
 246         jsonrpc_msg_destroy(msg);
 247         return rpc->status;
 248     }
 249
 250     jsonrpc_log_msg(rpc, "send", msg);
 251
 252     json = jsonrpc_msg_to_json(msg);
 253     s = json_to_string(json, 0);
 254     length = strlen(s);
 255     json_destroy(json);
 256
 257     buf = xmalloc(sizeof *buf);
 258     ofpbuf_use(buf, s, length);
 259     buf->size = length;
 260     list_push_back(&rpc->output, &buf->list_node);
 261     rpc->backlog += length;
 262
 263     if (rpc->backlog == length) {
 264         jsonrpc_run(rpc);
 265     }
 266     return rpc->status;
 267 }
 268
 269 /* Attempts to receive a message from 'rpc'.
 270  *
 271  * If successful, stores the received message in '*msgp' and returns 0.  The
 272  * caller takes ownership of '*msgp' and must eventually destroy it with
 273  * jsonrpc_msg_destroy().
 274  *
 275  * Otherwise, stores NULL in '*msgp' and returns one of the following:
 276  *
 277  *   - EAGAIN: No message has been received.
 278  *
 279  *   - EOF: The remote end closed the connection gracefully.
 280  *
 281  *   - Otherwise an errno value that represents a JSON-RPC protocol violation
 282  *     or another error fatal to the connection.  'rpc' will not send or
 283  *     receive any more messages.
 284  */
 285 int
 286 jsonrpc_recv(struct jsonrpc *rpc, struct jsonrpc_msg **msgp)
 287 {
 288     int i;
 289
 290     *msgp = NULL;
 291     if (rpc->status) {
 292         return rpc->status;
 293     }
 294
 295     for (i = 0; i < 50; i++) {
 296         if (rpc->received) {
 297             *msgp = rpc->received;
 298             rpc->received = NULL;
 299             return 0;
 300         } else if (byteq_is_empty(&rpc->input)) {
 301             size_t chunk;
 302             int retval;
 303
 304             chunk = byteq_headroom(&rpc->input);
 305             retval = stream_recv(rpc->stream, byteq_head(&rpc->input), chunk);
 306             if (retval < 0) {
 307                 if (retval == -EAGAIN) {
 308                     return EAGAIN;
 309                 } else {
 310                     VLOG_WARN_RL(&rl, "%s: receive error: %s",
 311                                  rpc->name, strerror(-retval));
 312                     jsonrpc_error(rpc, -retval);
 313                     return rpc->status;
 314                 }
 315             } else if (retval == 0) {
 316                 jsonrpc_error(rpc, EOF);
 317                 return EOF;
 318             }
 319             byteq_advance_head(&rpc->input, retval);
 320         } else {
 321             size_t n, used;
 322
 323             if (!rpc->parser) {
 324                 rpc->parser = json_parser_create(0);
 325             }
 326             n = byteq_tailroom(&rpc->input);
 327             used = json_parser_feed(rpc->parser,
 328                                     (char *) byteq_tail(&rpc->input), n);
 329             byteq_advance_tail(&rpc->input, used);
 330             if (json_parser_is_done(rpc->parser)) {
 331                 jsonrpc_received(rpc);
 332                 if (rpc->status) {
 333                     const struct byteq *q = &rpc->input;
 334                     if (q->head <= BYTEQ_SIZE) {
 335                         stream_report_content(q->buffer, q->head,
 336                                               STREAM_JSONRPC,
 337                                               THIS_MODULE, rpc->name);
 338                     }
 339                     return rpc->status;
 340                 }
 341             }
 342         }
 343     }
 344
 345     return EAGAIN;
 346 }
 347
 348 /* Causes the poll loop to wake up when jsonrpc_recv() may return a value other
 349  * than EAGAIN. */
 350 void
 351 jsonrpc_recv_wait(struct jsonrpc *rpc)
 352 {
 353     if (rpc->status || rpc->received || !byteq_is_empty(&rpc->input)) {
 354         (poll_immediate_wake)(rpc->name);
 355     } else {
 356         stream_recv_wait(rpc->stream);
 357     }
 358 }
 359
 360 /* Sends 'msg' on 'rpc' and waits for it to be successfully queued to the
 361  * underlying stream.  Returns 0 if 'msg' was sent successfully, otherwise a
 362  * status value (see jsonrpc_get_status()).
 363  *
 364  * Always takes ownership of 'msg', regardless of success. */
 365 int
 366 jsonrpc_send_block(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
 367 {
 368     int error;
 369
 370     fatal_signal_run();
 371
 372     error = jsonrpc_send(rpc, msg);
 373     if (error) {
 374         return error;
 375     }
 376
 377     for (;;) {
 378         jsonrpc_run(rpc);
 379         if (list_is_empty(&rpc->output) || rpc->status) {
 380             return rpc->status;
 381         }
 382         jsonrpc_wait(rpc);
 383         poll_block();
 384     }
 385 }
 386
 387 /* Waits for a message to be received on 'rpc'.  Same semantics as
 388  * jsonrpc_recv() except that EAGAIN will never be returned. */
 389 int
 390 jsonrpc_recv_block(struct jsonrpc *rpc, struct jsonrpc_msg **msgp)
 391 {
 392     for (;;) {
 393         int error = jsonrpc_recv(rpc, msgp);
 394         if (error != EAGAIN) {
 395             fatal_signal_run();
 396             return error;
 397         }
 398
 399         jsonrpc_run(rpc);
 400         jsonrpc_wait(rpc);
 401         jsonrpc_recv_wait(rpc);
 402         poll_block();
 403     }
 404 }
 405
 406 /* Sends 'request' to 'rpc' then waits for a reply.  The return value is 0 if
 407  * successful, in which case '*replyp' is set to the reply, which the caller
 408  * must eventually free with jsonrpc_msg_destroy().  Otherwise returns a status
 409  * value (see jsonrpc_get_status()).
 410  *
 411  * Discards any message received on 'rpc' that is not a reply to 'request'
 412  * (based on message id).
 413  *
 414  * Always takes ownership of 'request', regardless of success. */
 415 int
 416 jsonrpc_transact_block(struct jsonrpc *rpc, struct jsonrpc_msg *request,
 417                        struct jsonrpc_msg **replyp)
 418 {
 419     struct jsonrpc_msg *reply = NULL;
 420     struct json *id;
 421     int error;
 422
 423     id = json_clone(request->id);
 424     error = jsonrpc_send_block(rpc, request);
 425     if (!error) {
 426         for (;;) {
 427             error = jsonrpc_recv_block(rpc, &reply);
 428             if (error) {
 429                 break;
 430             }
 431             if ((reply->type == JSONRPC_REPLY || reply->type == JSONRPC_ERROR)
 432                 && json_equal(id, reply->id)) {
 433                 break;
 434             }
 435             jsonrpc_msg_destroy(reply);
 436         }
 437     }
 438     *replyp = error ? NULL : reply;
 439     json_destroy(id);
 440     return error;
 441 }
 442
 443 static void
 444 jsonrpc_received(struct jsonrpc *rpc)
 445 {
 446     struct jsonrpc_msg *msg;
 447     struct json *json;
 448     char *error;
 449
 450     json = json_parser_finish(rpc->parser);
 451     rpc->parser = NULL;
 452     if (json->type == JSON_STRING) {
 453         VLOG_WARN_RL(&rl, "%s: error parsing stream: %s",
 454                      rpc->name, json_string(json));
 455         jsonrpc_error(rpc, EPROTO);
 456         json_destroy(json);
 457         return;
 458     }
 459
 460     error = jsonrpc_msg_from_json(json, &msg);
 461     if (error) {
 462         VLOG_WARN_RL(&rl, "%s: received bad JSON-RPC message: %s",
 463                      rpc->name, error);
 464         free(error);
 465         jsonrpc_error(rpc, EPROTO);
 466         return;
 467     }
 468
 469     jsonrpc_log_msg(rpc, "received", msg);
 470     rpc->received = msg;
 471 }
 472
 473 static void
 474 jsonrpc_error(struct jsonrpc *rpc, int error)
 475 {
 476     assert(error);
 477     if (!rpc->status) {
 478         rpc->status = error;
 479         jsonrpc_cleanup(rpc);
 480     }
 481 }
 482
 483 static void
 484 jsonrpc_cleanup(struct jsonrpc *rpc)
 485 {
 486     stream_close(rpc->stream);
 487     rpc->stream = NULL;
 488
 489     json_parser_abort(rpc->parser);
 490     rpc->parser = NULL;
 491
 492     jsonrpc_msg_destroy(rpc->received);
 493     rpc->received = NULL;
 494
 495     ofpbuf_list_delete(&rpc->output);
 496     rpc->backlog = 0;
 497 }
 498 \f
 499 static struct jsonrpc_msg *
 500 jsonrpc_create(enum jsonrpc_msg_type type, const char *method,
 501                 struct json *params, struct json *result, struct json *error,
 502                 struct json *id)
 503 {
 504     struct jsonrpc_msg *msg = xmalloc(sizeof *msg);
 505     msg->type = type;
 506     msg->method = method ? xstrdup(method) : NULL;
 507     msg->params = params;
 508     msg->result = result;
 509     msg->error = error;
 510     msg->id = id;
 511     return msg;
 512 }
 513
 514 static struct json *
 515 jsonrpc_create_id(void)
 516 {
 517     static unsigned int id;
 518     return json_integer_create(id++);
 519 }
 520
 521 struct jsonrpc_msg *
 522 jsonrpc_create_request(const char *method, struct json *params,
 523                        struct json **idp)
 524 {
 525     struct json *id = jsonrpc_create_id();
 526     if (idp) {
 527         *idp = json_clone(id);
 528     }
 529     return jsonrpc_create(JSONRPC_REQUEST, method, params, NULL, NULL, id);
 530 }
 531
 532 struct jsonrpc_msg *
 533 jsonrpc_create_notify(const char *method, struct json *params)
 534 {
 535     return jsonrpc_create(JSONRPC_NOTIFY, method, params, NULL, NULL, NULL);
 536 }
 537
 538 struct jsonrpc_msg *
 539 jsonrpc_create_reply(struct json *result, const struct json *id)
 540 {
 541     return jsonrpc_create(JSONRPC_REPLY, NULL, NULL, result, NULL,
 542                            json_clone(id));
 543 }
 544
 545 struct jsonrpc_msg *
 546 jsonrpc_create_error(struct json *error, const struct json *id)
 547 {
 548     return jsonrpc_create(JSONRPC_REPLY, NULL, NULL, NULL, error,
 549                            json_clone(id));
 550 }
 551
 552 const char *
 553 jsonrpc_msg_type_to_string(enum jsonrpc_msg_type type)
 554 {
 555     switch (type) {
 556     case JSONRPC_REQUEST:
 557         return "request";
 558
 559     case JSONRPC_NOTIFY:
 560         return "notification";
 561
 562     case JSONRPC_REPLY:
 563         return "reply";
 564
 565     case JSONRPC_ERROR:
 566         return "error";
 567     }
 568     return "(null)";
 569 }
 570
 571 char *
 572 jsonrpc_msg_is_valid(const struct jsonrpc_msg *m)
 573 {
 574     const char *type_name;
 575     unsigned int pattern;
 576
 577     if (m->params && m->params->type != JSON_ARRAY) {
 578         return xstrdup("\"params\" must be JSON array");
 579     }
 580
 581     switch (m->type) {
 582     case JSONRPC_REQUEST:
 583         pattern = 0x11001;
 584         break;
 585
 586     case JSONRPC_NOTIFY:
 587         pattern = 0x11000;
 588         break;
 589
 590     case JSONRPC_REPLY:
 591         pattern = 0x00101;
 592         break;
 593
 594     case JSONRPC_ERROR:
 595         pattern = 0x00011;
 596         break;
 597
 598     default:
 599         return xasprintf("invalid JSON-RPC message type %d", m->type);
 600     }
 601
 602     type_name = jsonrpc_msg_type_to_string(m->type);
 603     if ((m->method != NULL) != ((pattern & 0x10000) != 0)) {
 604         return xasprintf("%s must%s have \"method\"",
 605                          type_name, (pattern & 0x10000) ? "" : " not");
 606
 607     }
 608     if ((m->params != NULL) != ((pattern & 0x1000) != 0)) {
 609         return xasprintf("%s must%s have \"params\"",
 610                          type_name, (pattern & 0x1000) ? "" : " not");
 611
 612     }
 613     if ((m->result != NULL) != ((pattern & 0x100) != 0)) {
 614         return xasprintf("%s must%s have \"result\"",
 615                          type_name, (pattern & 0x100) ? "" : " not");
 616
 617     }
 618     if ((m->error != NULL) != ((pattern & 0x10) != 0)) {
 619         return xasprintf("%s must%s have \"error\"",
 620                          type_name, (pattern & 0x10) ? "" : " not");
 621
 622     }
 623     if ((m->id != NULL) != ((pattern & 0x1) != 0)) {
 624         return xasprintf("%s must%s have \"id\"",
 625                          type_name, (pattern & 0x1) ? "" : " not");
 626
 627     }
 628     return NULL;
 629 }
 630
 631 void
 632 jsonrpc_msg_destroy(struct jsonrpc_msg *m)
 633 {
 634     if (m) {
 635         free(m->method);
 636         json_destroy(m->params);
 637         json_destroy(m->result);
 638         json_destroy(m->error);
 639         json_destroy(m->id);
 640         free(m);
 641     }
 642 }
 643
 644 static struct json *
 645 null_from_json_null(struct json *json)
 646 {
 647     if (json && json->type == JSON_NULL) {
 648         json_destroy(json);
 649         return NULL;
 650     }
 651     return json;
 652 }
 653
 654 char *
 655 jsonrpc_msg_from_json(struct json *json, struct jsonrpc_msg **msgp)
 656 {
 657     struct json *method = NULL;
 658     struct jsonrpc_msg *msg = NULL;
 659     struct shash *object;
 660     char *error;
 661
 662     if (json->type != JSON_OBJECT) {
 663         error = xstrdup("message is not a JSON object");
 664         goto exit;
 665     }
 666     object = json_object(json);
 667
 668     method = shash_find_and_delete(object, "method");
 669     if (method && method->type != JSON_STRING) {
 670         error = xstrdup("method is not a JSON string");
 671         goto exit;
 672     }
 673
 674     msg = xzalloc(sizeof *msg);
 675     msg->method = method ? xstrdup(method->u.string) : NULL;
 676     msg->params = null_from_json_null(shash_find_and_delete(object, "params"));
 677     msg->result = null_from_json_null(shash_find_and_delete(object, "result"));
 678     msg->error = null_from_json_null(shash_find_and_delete(object, "error"));
 679     msg->id = null_from_json_null(shash_find_and_delete(object, "id"));
 680     msg->type = (msg->result ? JSONRPC_REPLY
 681                  : msg->error ? JSONRPC_ERROR
 682                  : msg->id ? JSONRPC_REQUEST
 683                  : JSONRPC_NOTIFY);
 684     if (!shash_is_empty(object)) {
 685         error = xasprintf("message has unexpected member \"%s\"",
 686                           shash_first(object)->name);
 687         goto exit;
 688     }
 689     error = jsonrpc_msg_is_valid(msg);
 690     if (error) {
 691         goto exit;
 692     }
 693
 694 exit:
 695     json_destroy(method);
 696     json_destroy(json);
 697     if (error) {
 698         jsonrpc_msg_destroy(msg);
 699         msg = NULL;
 700     }
 701     *msgp = msg;
 702     return error;
 703 }
 704
 705 struct json *
 706 jsonrpc_msg_to_json(struct jsonrpc_msg *m)
 707 {
 708     struct json *json = json_object_create();
 709
 710     if (m->method) {
 711         json_object_put(json, "method", json_string_create_nocopy(m->method));
 712     }
 713
 714     if (m->params) {
 715         json_object_put(json, "params", m->params);
 716     }
 717
 718     if (m->result) {
 719         json_object_put(json, "result", m->result);
 720     } else if (m->type == JSONRPC_ERROR) {
 721         json_object_put(json, "result", json_null_create());
 722     }
 723
 724     if (m->error) {
 725         json_object_put(json, "error", m->error);
 726     } else if (m->type == JSONRPC_REPLY) {
 727         json_object_put(json, "error", json_null_create());
 728     }
 729
 730     if (m->id) {
 731         json_object_put(json, "id", m->id);
 732     } else if (m->type == JSONRPC_NOTIFY) {
 733         json_object_put(json, "id", json_null_create());
 734     }
 735
 736     free(m);
 737
 738     return json;
 739 }
 740 \f
 741 /* A JSON-RPC session with reconnection. */
 742
 743 struct jsonrpc_session {
 744     struct reconnect *reconnect;
 745     struct jsonrpc *rpc;
 746     struct stream *stream;
 747     struct pstream *pstream;
 748     unsigned int seqno;
 749     uint8_t dscp;
 750 };
 751
 752 /* Creates and returns a jsonrpc_session to 'name', which should be a string
 753  * acceptable to stream_open() or pstream_open().
 754  *
 755  * If 'name' is an active connection method, e.g. "tcp:127.1.2.3", the new
 756  * jsonrpc_session connects and reconnects, with back-off, to 'name'.
 757  *
 758  * If 'name' is a passive connection method, e.g. "ptcp:", the new
 759  * jsonrpc_session listens for connections to 'name'.  It maintains at most one
 760  * connection at any given time.  Any new connection causes the previous one
 761  * (if any) to be dropped. */
 762 struct jsonrpc_session *
 763 jsonrpc_session_open(const char *name)
 764 {
 765     struct jsonrpc_session *s;
 766
 767     s = xmalloc(sizeof *s);
 768     s->reconnect = reconnect_create(time_msec());
 769     reconnect_set_name(s->reconnect, name);
 770     reconnect_enable(s->reconnect, time_msec());
 771     s->rpc = NULL;
 772     s->stream = NULL;
 773     s->pstream = NULL;
 774     s->seqno = 0;
 775     s->dscp = 0;
 776
 777     if (!pstream_verify_name(name)) {
 778         reconnect_set_passive(s->reconnect, true, time_msec());
 779     }
 780
 781     if (!stream_or_pstream_needs_probes(name)) {
 782         reconnect_set_probe_interval(s->reconnect, 0);
 783     }
 784
 785     return s;
 786 }
 787
 788 /* Creates and returns a jsonrpc_session that is initially connected to
 789  * 'jsonrpc'.  If the connection is dropped, it will not be reconnected.
 790  *
 791  * On the assumption that such connections are likely to be short-lived
 792  * (e.g. from ovs-vsctl), informational logging for them is suppressed. */
 793 struct jsonrpc_session *
 794 jsonrpc_session_open_unreliably(struct jsonrpc *jsonrpc)
 795 {
 796     struct jsonrpc_session *s;
 797
 798     s = xmalloc(sizeof *s);
 799     s->reconnect = reconnect_create(time_msec());
 800     reconnect_set_quiet(s->reconnect, true);
 801     reconnect_set_name(s->reconnect, jsonrpc_get_name(jsonrpc));
 802     reconnect_set_max_tries(s->reconnect, 0);
 803     reconnect_connected(s->reconnect, time_msec());
 804     s->dscp = 0;
 805     s->rpc = jsonrpc;
 806     s->stream = NULL;
 807     s->pstream = NULL;
 808     s->seqno = 0;
 809
 810     return s;
 811 }
 812
 813 void
 814 jsonrpc_session_close(struct jsonrpc_session *s)
 815 {
 816     if (s) {
 817         jsonrpc_close(s->rpc);
 818         reconnect_destroy(s->reconnect);
 819         stream_close(s->stream);
 820         pstream_close(s->pstream);
 821         free(s);
 822     }
 823 }
 824
 825 static void
 826 jsonrpc_session_disconnect(struct jsonrpc_session *s)
 827 {
 828     if (s->rpc) {
 829         jsonrpc_error(s->rpc, EOF);
 830         jsonrpc_close(s->rpc);
 831         s->rpc = NULL;
 832         s->seqno++;
 833     } else if (s->stream) {
 834         stream_close(s->stream);
 835         s->stream = NULL;
 836         s->seqno++;
 837     }
 838 }
 839
 840 static void
 841 jsonrpc_session_connect(struct jsonrpc_session *s)
 842 {
 843     const char *name = reconnect_get_name(s->reconnect);
 844     int error;
 845
 846     jsonrpc_session_disconnect(s);
 847     if (!reconnect_is_passive(s->reconnect)) {
 848         error = jsonrpc_stream_open(name, &s->stream, s->dscp);
 849         if (!error) {
 850             reconnect_connecting(s->reconnect, time_msec());
 851         }
 852     } else {
 853         error = s->pstream ? 0 : jsonrpc_pstream_open(name, &s->pstream,
 854                                                       s->dscp);
 855         if (!error) {
 856             reconnect_listening(s->reconnect, time_msec());
 857         }
 858     }
 859
 860     if (error) {
 861         reconnect_connect_failed(s->reconnect, time_msec(), error);
 862     }
 863     s->seqno++;
 864 }
 865
 866 void
 867 jsonrpc_session_run(struct jsonrpc_session *s)
 868 {
 869     if (s->pstream) {
 870         struct stream *stream;
 871         int error;
 872
 873         error = pstream_accept(s->pstream, &stream);
 874         if (!error) {
 875             if (s->rpc || s->stream) {
 876                 VLOG_INFO_RL(&rl,
 877                              "%s: new connection replacing active connection",
 878                              reconnect_get_name(s->reconnect));
 879                 jsonrpc_session_disconnect(s);
 880             }
 881             reconnect_connected(s->reconnect, time_msec());
 882             s->rpc = jsonrpc_open(stream);
 883         } else if (error != EAGAIN) {
 884             reconnect_listen_error(s->reconnect, time_msec(), error);
 885             pstream_close(s->pstream);
 886             s->pstream = NULL;
 887         }
 888     }
 889
 890     if (s->rpc) {
 891         size_t backlog;
 892         int error;
 893
 894         backlog = jsonrpc_get_backlog(s->rpc);
 895         jsonrpc_run(s->rpc);
 896         if (jsonrpc_get_backlog(s->rpc) < backlog) {
 897             /* Data previously caught in a queue was successfully sent (or
 898              * there's an error, which we'll catch below.)
 899              *
 900              * We don't count data that is successfully sent immediately as
 901              * activity, because there's a lot of queuing downstream from us,
 902              * which means that we can push a lot of data into a connection
 903              * that has stalled and won't ever recover.
 904              */
 905             reconnect_activity(s->reconnect, time_msec());
 906         }
 907
 908         error = jsonrpc_get_status(s->rpc);
 909         if (error) {
 910             reconnect_disconnected(s->reconnect, time_msec(), error);
 911             jsonrpc_session_disconnect(s);
 912         }
 913     } else if (s->stream) {
 914         int error;
 915
 916         stream_run(s->stream);
 917         error = stream_connect(s->stream);
 918         if (!error) {
 919             reconnect_connected(s->reconnect, time_msec());
 920             s->rpc = jsonrpc_open(s->stream);
 921             s->stream = NULL;
 922         } else if (error != EAGAIN) {
 923             reconnect_connect_failed(s->reconnect, time_msec(), error);
 924             stream_close(s->stream);
 925             s->stream = NULL;
 926         }
 927     }
 928
 929     switch (reconnect_run(s->reconnect, time_msec())) {
 930     case RECONNECT_CONNECT:
 931         jsonrpc_session_connect(s);
 932         break;
 933
 934     case RECONNECT_DISCONNECT:
 935         reconnect_disconnected(s->reconnect, time_msec(), 0);
 936         jsonrpc_session_disconnect(s);
 937         break;
 938
 939     case RECONNECT_PROBE:
 940         if (s->rpc) {
 941             struct json *params;
 942             struct jsonrpc_msg *request;
 943
 944             params = json_array_create_empty();
 945             request = jsonrpc_create_request("echo", params, NULL);
 946             json_destroy(request->id);
 947             request->id = json_string_create("echo");
 948             jsonrpc_send(s->rpc, request);
 949         }
 950         break;
 951     }
 952 }
 953
 954 void
 955 jsonrpc_session_wait(struct jsonrpc_session *s)
 956 {
 957     if (s->rpc) {
 958         jsonrpc_wait(s->rpc);
 959     } else if (s->stream) {
 960         stream_run_wait(s->stream);
 961         stream_connect_wait(s->stream);
 962     }
 963     if (s->pstream) {
 964         pstream_wait(s->pstream);
 965     }
 966     reconnect_wait(s->reconnect, time_msec());
 967 }
 968
 969 size_t
 970 jsonrpc_session_get_backlog(const struct jsonrpc_session *s)
 971 {
 972     return s->rpc ? jsonrpc_get_backlog(s->rpc) : 0;
 973 }
 974
 975 /* Always returns a pointer to a valid C string, assuming 's' was initialized
 976  * correctly. */
 977 const char *
 978 jsonrpc_session_get_name(const struct jsonrpc_session *s)
 979 {
 980     return reconnect_get_name(s->reconnect);
 981 }
 982
 983 /* Always takes ownership of 'msg', regardless of success. */
 984 int
 985 jsonrpc_session_send(struct jsonrpc_session *s, struct jsonrpc_msg *msg)
 986 {
 987     if (s->rpc) {
 988         return jsonrpc_send(s->rpc, msg);
 989     } else {
 990         jsonrpc_msg_destroy(msg);
 991         return ENOTCONN;
 992     }
 993 }
 994
 995 struct jsonrpc_msg *
 996 jsonrpc_session_recv(struct jsonrpc_session *s)
 997 {
 998     if (s->rpc) {
 999         unsigned int received_bytes;
1000         struct jsonrpc_msg *msg;
1001
1002         received_bytes = jsonrpc_get_received_bytes(s->rpc);
1003         jsonrpc_recv(s->rpc, &msg);
1004         if (received_bytes != jsonrpc_get_received_bytes(s->rpc)) {
1005             /* Data was successfully received.
1006              *
1007              * Previously we only counted receiving a full message as activity,
1008              * but with large messages or a slow connection that policy could
1009              * time out the session mid-message. */
1010             reconnect_activity(s->reconnect, time_msec());
1011         }
1012
1013         if (msg) {
1014             if (msg->type == JSONRPC_REQUEST && !strcmp(msg->method, "echo")) {
1015                 /* Echo request.  Send reply. */
1016                 struct jsonrpc_msg *reply;
1017
1018                 reply = jsonrpc_create_reply(json_clone(msg->params), msg->id);
1019                 jsonrpc_session_send(s, reply);
1020             } else if (msg->type == JSONRPC_REPLY
1021                        && msg->id && msg->id->type == JSON_STRING
1022                        && !strcmp(msg->id->u.string, "echo")) {
1023                 /* It's a reply to our echo request.  Suppress it. */
1024             } else {
1025                 return msg;
1026             }
1027             jsonrpc_msg_destroy(msg);
1028         }
1029     }
1030     return NULL;
1031 }
1032
1033 void
1034 jsonrpc_session_recv_wait(struct jsonrpc_session *s)
1035 {
1036     if (s->rpc) {
1037         jsonrpc_recv_wait(s->rpc);
1038     }
1039 }
1040
1041 bool
1042 jsonrpc_session_is_alive(const struct jsonrpc_session *s)
1043 {
1044     return s->rpc || s->stream || reconnect_get_max_tries(s->reconnect);
1045 }
1046
1047 bool
1048 jsonrpc_session_is_connected(const struct jsonrpc_session *s)
1049 {
1050     return s->rpc != NULL;
1051 }
1052
1053 unsigned int
1054 jsonrpc_session_get_seqno(const struct jsonrpc_session *s)
1055 {
1056     return s->seqno;
1057 }
1058
1059 int
1060 jsonrpc_session_get_status(const struct jsonrpc_session *s)
1061 {
1062     return s && s->rpc ? jsonrpc_get_status(s->rpc) : 0;
1063 }
1064
1065 void
1066 jsonrpc_session_get_reconnect_stats(const struct jsonrpc_session *s,
1067                                     struct reconnect_stats *stats)
1068 {
1069     reconnect_get_stats(s->reconnect, time_msec(), stats);
1070 }
1071
1072 void
1073 jsonrpc_session_force_reconnect(struct jsonrpc_session *s)
1074 {
1075     reconnect_force_reconnect(s->reconnect, time_msec());
1076 }
1077
1078 void
1079 jsonrpc_session_set_max_backoff(struct jsonrpc_session *s, int max_backoff)
1080 {
1081     reconnect_set_backoff(s->reconnect, 0, max_backoff);
1082 }
1083
1084 void
1085 jsonrpc_session_set_probe_interval(struct jsonrpc_session *s,
1086                                    int probe_interval)
1087 {
1088     reconnect_set_probe_interval(s->reconnect, probe_interval);
1089 }
1090
1091 void
1092 jsonrpc_session_set_dscp(struct jsonrpc_session *s,
1093                          uint8_t dscp)
1094 {
1095     if (s->dscp != dscp) {
1096         s->dscp = dscp;
1097         jsonrpc_session_force_reconnect(s);
1098     }
1099 }