lib/jsonrpc.c

   1 /*
   2  * Copyright (c) 2009, 2010, 2011, 2012 Nicira Networks.
   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 'rpc''s name, that is, the name returned by stream_get_name() for
 182  * the stream underlying 'rpc' when 'rpc' was created. */
 183 const char *
 184 jsonrpc_get_name(const struct jsonrpc *rpc)
 185 {
 186     return rpc->name;
 187 }
 188
 189 static void
 190 jsonrpc_log_msg(const struct jsonrpc *rpc, const char *title,
 191                 const struct jsonrpc_msg *msg)
 192 {
 193     if (VLOG_IS_DBG_ENABLED()) {
 194         struct ds s = DS_EMPTY_INITIALIZER;
 195         if (msg->method) {
 196             ds_put_format(&s, ", method=\"%s\"", msg->method);
 197         }
 198         if (msg->params) {
 199             ds_put_cstr(&s, ", params=");
 200             json_to_ds(msg->params, 0, &s);
 201         }
 202         if (msg->result) {
 203             ds_put_cstr(&s, ", result=");
 204             json_to_ds(msg->result, 0, &s);
 205         }
 206         if (msg->error) {
 207             ds_put_cstr(&s, ", error=");
 208             json_to_ds(msg->error, 0, &s);
 209         }
 210         if (msg->id) {
 211             ds_put_cstr(&s, ", id=");
 212             json_to_ds(msg->id, 0, &s);
 213         }
 214         VLOG_DBG("%s: %s %s%s", rpc->name, title,
 215                  jsonrpc_msg_type_to_string(msg->type), ds_cstr(&s));
 216         ds_destroy(&s);
 217     }
 218 }
 219
 220 /* Schedules 'msg' to be sent on 'rpc' and returns 'rpc''s status (as with
 221  * jsonrpc_get_status()).
 222  *
 223  * If 'msg' cannot be sent immediately, it is appended to a buffer.  The caller
 224  * is responsible for ensuring that the amount of buffered data is somehow
 225  * limited.  (jsonrpc_get_backlog() returns the amount of data currently
 226  * buffered in 'rpc'.)
 227  *
 228  * Always takes ownership of 'msg', regardless of success. */
 229 int
 230 jsonrpc_send(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
 231 {
 232     struct ofpbuf *buf;
 233     struct json *json;
 234     size_t length;
 235     char *s;
 236
 237     if (rpc->status) {
 238         jsonrpc_msg_destroy(msg);
 239         return rpc->status;
 240     }
 241
 242     jsonrpc_log_msg(rpc, "send", msg);
 243
 244     json = jsonrpc_msg_to_json(msg);
 245     s = json_to_string(json, 0);
 246     length = strlen(s);
 247     json_destroy(json);
 248
 249     buf = xmalloc(sizeof *buf);
 250     ofpbuf_use(buf, s, length);
 251     buf->size = length;
 252     list_push_back(&rpc->output, &buf->list_node);
 253     rpc->backlog += length;
 254
 255     if (rpc->backlog == length) {
 256         jsonrpc_run(rpc);
 257     }
 258     return rpc->status;
 259 }
 260
 261 /* Attempts to receive a message from 'rpc'.
 262  *
 263  * If successful, stores the received message in '*msgp' and returns 0.  The
 264  * caller takes ownership of '*msgp' and must eventually destroy it with
 265  * jsonrpc_msg_destroy().
 266  *
 267  * Otherwise, stores NULL in '*msgp' and returns one of the following:
 268  *
 269  *   - EAGAIN: No message has been received.
 270  *
 271  *   - EOF: The remote end closed the connection gracefully.
 272  *
 273  *   - Otherwise an errno value that represents a JSON-RPC protocol violation
 274  *     or another error fatal to the connection.  'rpc' will not send or
 275  *     receive any more messages.
 276  */
 277 int
 278 jsonrpc_recv(struct jsonrpc *rpc, struct jsonrpc_msg **msgp)
 279 {
 280     *msgp = NULL;
 281     if (rpc->status) {
 282         return rpc->status;
 283     }
 284
 285     while (!rpc->received) {
 286         if (byteq_is_empty(&rpc->input)) {
 287             size_t chunk;
 288             int retval;
 289
 290             chunk = byteq_headroom(&rpc->input);
 291             retval = stream_recv(rpc->stream, byteq_head(&rpc->input), chunk);
 292             if (retval < 0) {
 293                 if (retval == -EAGAIN) {
 294                     return EAGAIN;
 295                 } else {
 296                     VLOG_WARN_RL(&rl, "%s: receive error: %s",
 297                                  rpc->name, strerror(-retval));
 298                     jsonrpc_error(rpc, -retval);
 299                     return rpc->status;
 300                 }
 301             } else if (retval == 0) {
 302                 jsonrpc_error(rpc, EOF);
 303                 return EOF;
 304             }
 305             byteq_advance_head(&rpc->input, retval);
 306         } else {
 307             size_t n, used;
 308
 309             if (!rpc->parser) {
 310                 rpc->parser = json_parser_create(0);
 311             }
 312             n = byteq_tailroom(&rpc->input);
 313             used = json_parser_feed(rpc->parser,
 314                                     (char *) byteq_tail(&rpc->input), n);
 315             byteq_advance_tail(&rpc->input, used);
 316             if (json_parser_is_done(rpc->parser)) {
 317                 jsonrpc_received(rpc);
 318                 if (rpc->status) {
 319                     const struct byteq *q = &rpc->input;
 320                     if (q->head <= BYTEQ_SIZE) {
 321                         stream_report_content(q->buffer, q->head,
 322                                               STREAM_JSONRPC,
 323                                               THIS_MODULE, rpc->name);
 324                     }
 325                     return rpc->status;
 326                 }
 327             }
 328         }
 329     }
 330
 331     *msgp = rpc->received;
 332     rpc->received = NULL;
 333     return 0;
 334 }
 335
 336 /* Causes the poll loop to wake up when jsonrpc_recv() may return a value other
 337  * than EAGAIN. */
 338 void
 339 jsonrpc_recv_wait(struct jsonrpc *rpc)
 340 {
 341     if (rpc->status || rpc->received || !byteq_is_empty(&rpc->input)) {
 342         (poll_immediate_wake)(rpc->name);
 343     } else {
 344         stream_recv_wait(rpc->stream);
 345     }
 346 }
 347
 348 /* Sends 'msg' on 'rpc' and waits for it to be successfully queued to the
 349  * underlying stream.  Returns 0 if 'msg' was sent successfully, otherwise a
 350  * status value (see jsonrpc_get_status()).
 351  *
 352  * Always takes ownership of 'msg', regardless of success. */
 353 int
 354 jsonrpc_send_block(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
 355 {
 356     int error;
 357
 358     fatal_signal_run();
 359
 360     error = jsonrpc_send(rpc, msg);
 361     if (error) {
 362         return error;
 363     }
 364
 365     for (;;) {
 366         jsonrpc_run(rpc);
 367         if (list_is_empty(&rpc->output) || rpc->status) {
 368             return rpc->status;
 369         }
 370         jsonrpc_wait(rpc);
 371         poll_block();
 372     }
 373 }
 374
 375 /* Waits for a message to be received on 'rpc'.  Same semantics as
 376  * jsonrpc_recv() except that EAGAIN will never be returned. */
 377 int
 378 jsonrpc_recv_block(struct jsonrpc *rpc, struct jsonrpc_msg **msgp)
 379 {
 380     for (;;) {
 381         int error = jsonrpc_recv(rpc, msgp);
 382         if (error != EAGAIN) {
 383             fatal_signal_run();
 384             return error;
 385         }
 386
 387         jsonrpc_run(rpc);
 388         jsonrpc_wait(rpc);
 389         jsonrpc_recv_wait(rpc);
 390         poll_block();
 391     }
 392 }
 393
 394 /* Sends 'request' to 'rpc' then waits for a reply.  The return value is 0 if
 395  * successful, in which case '*replyp' is set to the reply, which the caller
 396  * must eventually free with jsonrpc_msg_destroy().  Otherwise returns a status
 397  * value (see jsonrpc_get_status()).
 398  *
 399  * Discards any message received on 'rpc' that is not a reply to 'request'
 400  * (based on message id).
 401  *
 402  * Always takes ownership of 'request', regardless of success. */
 403 int
 404 jsonrpc_transact_block(struct jsonrpc *rpc, struct jsonrpc_msg *request,
 405                        struct jsonrpc_msg **replyp)
 406 {
 407     struct jsonrpc_msg *reply = NULL;
 408     struct json *id;
 409     int error;
 410
 411     id = json_clone(request->id);
 412     error = jsonrpc_send_block(rpc, request);
 413     if (!error) {
 414         for (;;) {
 415             error = jsonrpc_recv_block(rpc, &reply);
 416             if (error) {
 417                 break;
 418             }
 419             if ((reply->type == JSONRPC_REPLY || reply->type == JSONRPC_ERROR)
 420                 && json_equal(id, reply->id)) {
 421                 break;
 422             }
 423             jsonrpc_msg_destroy(reply);
 424         }
 425     }
 426     *replyp = error ? NULL : reply;
 427     json_destroy(id);
 428     return error;
 429 }
 430
 431 static void
 432 jsonrpc_received(struct jsonrpc *rpc)
 433 {
 434     struct jsonrpc_msg *msg;
 435     struct json *json;
 436     char *error;
 437
 438     json = json_parser_finish(rpc->parser);
 439     rpc->parser = NULL;
 440     if (json->type == JSON_STRING) {
 441         VLOG_WARN_RL(&rl, "%s: error parsing stream: %s",
 442                      rpc->name, json_string(json));
 443         jsonrpc_error(rpc, EPROTO);
 444         json_destroy(json);
 445         return;
 446     }
 447
 448     error = jsonrpc_msg_from_json(json, &msg);
 449     if (error) {
 450         VLOG_WARN_RL(&rl, "%s: received bad JSON-RPC message: %s",
 451                      rpc->name, error);
 452         free(error);
 453         jsonrpc_error(rpc, EPROTO);
 454         return;
 455     }
 456
 457     jsonrpc_log_msg(rpc, "received", msg);
 458     rpc->received = msg;
 459 }
 460
 461 static void
 462 jsonrpc_error(struct jsonrpc *rpc, int error)
 463 {
 464     assert(error);
 465     if (!rpc->status) {
 466         rpc->status = error;
 467         jsonrpc_cleanup(rpc);
 468     }
 469 }
 470
 471 static void
 472 jsonrpc_cleanup(struct jsonrpc *rpc)
 473 {
 474     stream_close(rpc->stream);
 475     rpc->stream = NULL;
 476
 477     json_parser_abort(rpc->parser);
 478     rpc->parser = NULL;
 479
 480     jsonrpc_msg_destroy(rpc->received);
 481     rpc->received = NULL;
 482
 483     ofpbuf_list_delete(&rpc->output);
 484     rpc->backlog = 0;
 485 }
 486 \f
 487 static struct jsonrpc_msg *
 488 jsonrpc_create(enum jsonrpc_msg_type type, const char *method,
 489                 struct json *params, struct json *result, struct json *error,
 490                 struct json *id)
 491 {
 492     struct jsonrpc_msg *msg = xmalloc(sizeof *msg);
 493     msg->type = type;
 494     msg->method = method ? xstrdup(method) : NULL;
 495     msg->params = params;
 496     msg->result = result;
 497     msg->error = error;
 498     msg->id = id;
 499     return msg;
 500 }
 501
 502 static struct json *
 503 jsonrpc_create_id(void)
 504 {
 505     static unsigned int id;
 506     return json_integer_create(id++);
 507 }
 508
 509 struct jsonrpc_msg *
 510 jsonrpc_create_request(const char *method, struct json *params,
 511                        struct json **idp)
 512 {
 513     struct json *id = jsonrpc_create_id();
 514     if (idp) {
 515         *idp = json_clone(id);
 516     }
 517     return jsonrpc_create(JSONRPC_REQUEST, method, params, NULL, NULL, id);
 518 }
 519
 520 struct jsonrpc_msg *
 521 jsonrpc_create_notify(const char *method, struct json *params)
 522 {
 523     return jsonrpc_create(JSONRPC_NOTIFY, method, params, NULL, NULL, NULL);
 524 }
 525
 526 struct jsonrpc_msg *
 527 jsonrpc_create_reply(struct json *result, const struct json *id)
 528 {
 529     return jsonrpc_create(JSONRPC_REPLY, NULL, NULL, result, NULL,
 530                            json_clone(id));
 531 }
 532
 533 struct jsonrpc_msg *
 534 jsonrpc_create_error(struct json *error, const struct json *id)
 535 {
 536     return jsonrpc_create(JSONRPC_REPLY, NULL, NULL, NULL, error,
 537                            json_clone(id));
 538 }
 539
 540 const char *
 541 jsonrpc_msg_type_to_string(enum jsonrpc_msg_type type)
 542 {
 543     switch (type) {
 544     case JSONRPC_REQUEST:
 545         return "request";
 546
 547     case JSONRPC_NOTIFY:
 548         return "notification";
 549
 550     case JSONRPC_REPLY:
 551         return "reply";
 552
 553     case JSONRPC_ERROR:
 554         return "error";
 555     }
 556     return "(null)";
 557 }
 558
 559 char *
 560 jsonrpc_msg_is_valid(const struct jsonrpc_msg *m)
 561 {
 562     const char *type_name;
 563     unsigned int pattern;
 564
 565     if (m->params && m->params->type != JSON_ARRAY) {
 566         return xstrdup("\"params\" must be JSON array");
 567     }
 568
 569     switch (m->type) {
 570     case JSONRPC_REQUEST:
 571         pattern = 0x11001;
 572         break;
 573
 574     case JSONRPC_NOTIFY:
 575         pattern = 0x11000;
 576         break;
 577
 578     case JSONRPC_REPLY:
 579         pattern = 0x00101;
 580         break;
 581
 582     case JSONRPC_ERROR:
 583         pattern = 0x00011;
 584         break;
 585
 586     default:
 587         return xasprintf("invalid JSON-RPC message type %d", m->type);
 588     }
 589
 590     type_name = jsonrpc_msg_type_to_string(m->type);
 591     if ((m->method != NULL) != ((pattern & 0x10000) != 0)) {
 592         return xasprintf("%s must%s have \"method\"",
 593                          type_name, (pattern & 0x10000) ? "" : " not");
 594
 595     }
 596     if ((m->params != NULL) != ((pattern & 0x1000) != 0)) {
 597         return xasprintf("%s must%s have \"params\"",
 598                          type_name, (pattern & 0x1000) ? "" : " not");
 599
 600     }
 601     if ((m->result != NULL) != ((pattern & 0x100) != 0)) {
 602         return xasprintf("%s must%s have \"result\"",
 603                          type_name, (pattern & 0x100) ? "" : " not");
 604
 605     }
 606     if ((m->error != NULL) != ((pattern & 0x10) != 0)) {
 607         return xasprintf("%s must%s have \"error\"",
 608                          type_name, (pattern & 0x10) ? "" : " not");
 609
 610     }
 611     if ((m->id != NULL) != ((pattern & 0x1) != 0)) {
 612         return xasprintf("%s must%s have \"id\"",
 613                          type_name, (pattern & 0x1) ? "" : " not");
 614
 615     }
 616     return NULL;
 617 }
 618
 619 void
 620 jsonrpc_msg_destroy(struct jsonrpc_msg *m)
 621 {
 622     if (m) {
 623         free(m->method);
 624         json_destroy(m->params);
 625         json_destroy(m->result);
 626         json_destroy(m->error);
 627         json_destroy(m->id);
 628         free(m);
 629     }
 630 }
 631
 632 static struct json *
 633 null_from_json_null(struct json *json)
 634 {
 635     if (json && json->type == JSON_NULL) {
 636         json_destroy(json);
 637         return NULL;
 638     }
 639     return json;
 640 }
 641
 642 char *
 643 jsonrpc_msg_from_json(struct json *json, struct jsonrpc_msg **msgp)
 644 {
 645     struct json *method = NULL;
 646     struct jsonrpc_msg *msg = NULL;
 647     struct shash *object;
 648     char *error;
 649
 650     if (json->type != JSON_OBJECT) {
 651         error = xstrdup("message is not a JSON object");
 652         goto exit;
 653     }
 654     object = json_object(json);
 655
 656     method = shash_find_and_delete(object, "method");
 657     if (method && method->type != JSON_STRING) {
 658         error = xstrdup("method is not a JSON string");
 659         goto exit;
 660     }
 661
 662     msg = xzalloc(sizeof *msg);
 663     msg->method = method ? xstrdup(method->u.string) : NULL;
 664     msg->params = null_from_json_null(shash_find_and_delete(object, "params"));
 665     msg->result = null_from_json_null(shash_find_and_delete(object, "result"));
 666     msg->error = null_from_json_null(shash_find_and_delete(object, "error"));
 667     msg->id = null_from_json_null(shash_find_and_delete(object, "id"));
 668     msg->type = (msg->result ? JSONRPC_REPLY
 669                  : msg->error ? JSONRPC_ERROR
 670                  : msg->id ? JSONRPC_REQUEST
 671                  : JSONRPC_NOTIFY);
 672     if (!shash_is_empty(object)) {
 673         error = xasprintf("message has unexpected member \"%s\"",
 674                           shash_first(object)->name);
 675         goto exit;
 676     }
 677     error = jsonrpc_msg_is_valid(msg);
 678     if (error) {
 679         goto exit;
 680     }
 681
 682 exit:
 683     json_destroy(method);
 684     json_destroy(json);
 685     if (error) {
 686         jsonrpc_msg_destroy(msg);
 687         msg = NULL;
 688     }
 689     *msgp = msg;
 690     return error;
 691 }
 692
 693 struct json *
 694 jsonrpc_msg_to_json(struct jsonrpc_msg *m)
 695 {
 696     struct json *json = json_object_create();
 697
 698     if (m->method) {
 699         json_object_put(json, "method", json_string_create_nocopy(m->method));
 700     }
 701
 702     if (m->params) {
 703         json_object_put(json, "params", m->params);
 704     }
 705
 706     if (m->result) {
 707         json_object_put(json, "result", m->result);
 708     } else if (m->type == JSONRPC_ERROR) {
 709         json_object_put(json, "result", json_null_create());
 710     }
 711
 712     if (m->error) {
 713         json_object_put(json, "error", m->error);
 714     } else if (m->type == JSONRPC_REPLY) {
 715         json_object_put(json, "error", json_null_create());
 716     }
 717
 718     if (m->id) {
 719         json_object_put(json, "id", m->id);
 720     } else if (m->type == JSONRPC_NOTIFY) {
 721         json_object_put(json, "id", json_null_create());
 722     }
 723
 724     free(m);
 725
 726     return json;
 727 }
 728 \f
 729 /* A JSON-RPC session with reconnection. */
 730
 731 struct jsonrpc_session {
 732     struct reconnect *reconnect;
 733     struct jsonrpc *rpc;
 734     struct stream *stream;
 735     struct pstream *pstream;
 736     unsigned int seqno;
 737 };
 738
 739 /* Creates and returns a jsonrpc_session to 'name', which should be a string
 740  * acceptable to stream_open() or pstream_open().
 741  *
 742  * If 'name' is an active connection method, e.g. "tcp:127.1.2.3", the new
 743  * jsonrpc_session connects and reconnects, with back-off, to 'name'.
 744  *
 745  * If 'name' is a passive connection method, e.g. "ptcp:", the new
 746  * jsonrpc_session listens for connections to 'name'.  It maintains at most one
 747  * connection at any given time.  Any new connection causes the previous one
 748  * (if any) to be dropped. */
 749 struct jsonrpc_session *
 750 jsonrpc_session_open(const char *name)
 751 {
 752     struct jsonrpc_session *s;
 753
 754     s = xmalloc(sizeof *s);
 755     s->reconnect = reconnect_create(time_msec());
 756     reconnect_set_name(s->reconnect, name);
 757     reconnect_enable(s->reconnect, time_msec());
 758     s->rpc = NULL;
 759     s->stream = NULL;
 760     s->pstream = NULL;
 761     s->seqno = 0;
 762
 763     if (!pstream_verify_name(name)) {
 764         reconnect_set_passive(s->reconnect, true, time_msec());
 765     }
 766
 767     if (!stream_or_pstream_needs_probes(name)) {
 768         reconnect_set_probe_interval(s->reconnect, 0);
 769     }
 770
 771     return s;
 772 }
 773
 774 /* Creates and returns a jsonrpc_session that is initially connected to
 775  * 'jsonrpc'.  If the connection is dropped, it will not be reconnected.
 776  *
 777  * On the assumption that such connections are likely to be short-lived
 778  * (e.g. from ovs-vsctl), informational logging for them is suppressed. */
 779 struct jsonrpc_session *
 780 jsonrpc_session_open_unreliably(struct jsonrpc *jsonrpc)
 781 {
 782     struct jsonrpc_session *s;
 783
 784     s = xmalloc(sizeof *s);
 785     s->reconnect = reconnect_create(time_msec());
 786     reconnect_set_quiet(s->reconnect, true);
 787     reconnect_set_name(s->reconnect, jsonrpc_get_name(jsonrpc));
 788     reconnect_set_max_tries(s->reconnect, 0);
 789     reconnect_connected(s->reconnect, time_msec());
 790     s->rpc = jsonrpc;
 791     s->stream = NULL;
 792     s->pstream = NULL;
 793     s->seqno = 0;
 794
 795     return s;
 796 }
 797
 798 void
 799 jsonrpc_session_close(struct jsonrpc_session *s)
 800 {
 801     if (s) {
 802         jsonrpc_close(s->rpc);
 803         reconnect_destroy(s->reconnect);
 804         stream_close(s->stream);
 805         pstream_close(s->pstream);
 806         free(s);
 807     }
 808 }
 809
 810 static void
 811 jsonrpc_session_disconnect(struct jsonrpc_session *s)
 812 {
 813     if (s->rpc) {
 814         jsonrpc_error(s->rpc, EOF);
 815         jsonrpc_close(s->rpc);
 816         s->rpc = NULL;
 817         s->seqno++;
 818     } else if (s->stream) {
 819         stream_close(s->stream);
 820         s->stream = NULL;
 821         s->seqno++;
 822     }
 823 }
 824
 825 static void
 826 jsonrpc_session_connect(struct jsonrpc_session *s)
 827 {
 828     const char *name = reconnect_get_name(s->reconnect);
 829     int error;
 830
 831     jsonrpc_session_disconnect(s);
 832     if (!reconnect_is_passive(s->reconnect)) {
 833         error = jsonrpc_stream_open(name, &s->stream,
 834                                     reconnect_get_dscp(s->reconnect));
 835         if (!error) {
 836             reconnect_connecting(s->reconnect, time_msec());
 837         }
 838     } else {
 839         error = s->pstream ? 0 : jsonrpc_pstream_open(name, &s->pstream,
 840                                         reconnect_get_dscp(s->reconnect));
 841         if (!error) {
 842             reconnect_listening(s->reconnect, time_msec());
 843         }
 844     }
 845
 846     if (error) {
 847         reconnect_connect_failed(s->reconnect, time_msec(), error);
 848     }
 849     s->seqno++;
 850 }
 851
 852 void
 853 jsonrpc_session_run(struct jsonrpc_session *s)
 854 {
 855     if (s->pstream) {
 856         struct stream *stream;
 857         int error;
 858
 859         error = pstream_accept(s->pstream, &stream);
 860         if (!error) {
 861             if (s->rpc || s->stream) {
 862                 VLOG_INFO_RL(&rl,
 863                              "%s: new connection replacing active connection",
 864                              reconnect_get_name(s->reconnect));
 865                 jsonrpc_session_disconnect(s);
 866             }
 867             reconnect_connected(s->reconnect, time_msec());
 868             s->rpc = jsonrpc_open(stream);
 869         } else if (error != EAGAIN) {
 870             reconnect_listen_error(s->reconnect, time_msec(), error);
 871             pstream_close(s->pstream);
 872             s->pstream = NULL;
 873         }
 874     }
 875
 876     if (s->rpc) {
 877         int error;
 878
 879         jsonrpc_run(s->rpc);
 880         error = jsonrpc_get_status(s->rpc);
 881         if (error) {
 882             reconnect_disconnected(s->reconnect, time_msec(), error);
 883             jsonrpc_session_disconnect(s);
 884         }
 885     } else if (s->stream) {
 886         int error;
 887
 888         stream_run(s->stream);
 889         error = stream_connect(s->stream);
 890         if (!error) {
 891             reconnect_connected(s->reconnect, time_msec());
 892             s->rpc = jsonrpc_open(s->stream);
 893             s->stream = NULL;
 894         } else if (error != EAGAIN) {
 895             reconnect_connect_failed(s->reconnect, time_msec(), error);
 896             stream_close(s->stream);
 897             s->stream = NULL;
 898         }
 899     }
 900
 901     switch (reconnect_run(s->reconnect, time_msec())) {
 902     case RECONNECT_CONNECT:
 903         jsonrpc_session_connect(s);
 904         break;
 905
 906     case RECONNECT_DISCONNECT:
 907         reconnect_disconnected(s->reconnect, time_msec(), 0);
 908         jsonrpc_session_disconnect(s);
 909         break;
 910
 911     case RECONNECT_PROBE:
 912         if (s->rpc) {
 913             struct json *params;
 914             struct jsonrpc_msg *request;
 915
 916             params = json_array_create_empty();
 917             request = jsonrpc_create_request("echo", params, NULL);
 918             json_destroy(request->id);
 919             request->id = json_string_create("echo");
 920             jsonrpc_send(s->rpc, request);
 921         }
 922         break;
 923     }
 924 }
 925
 926 void
 927 jsonrpc_session_wait(struct jsonrpc_session *s)
 928 {
 929     if (s->rpc) {
 930         jsonrpc_wait(s->rpc);
 931     } else if (s->stream) {
 932         stream_run_wait(s->stream);
 933         stream_connect_wait(s->stream);
 934     }
 935     if (s->pstream) {
 936         pstream_wait(s->pstream);
 937     }
 938     reconnect_wait(s->reconnect, time_msec());
 939 }
 940
 941 size_t
 942 jsonrpc_session_get_backlog(const struct jsonrpc_session *s)
 943 {
 944     return s->rpc ? jsonrpc_get_backlog(s->rpc) : 0;
 945 }
 946
 947 /* Always returns a pointer to a valid C string, assuming 's' was initialized
 948  * correctly. */
 949 const char *
 950 jsonrpc_session_get_name(const struct jsonrpc_session *s)
 951 {
 952     return reconnect_get_name(s->reconnect);
 953 }
 954
 955 /* Always takes ownership of 'msg', regardless of success. */
 956 int
 957 jsonrpc_session_send(struct jsonrpc_session *s, struct jsonrpc_msg *msg)
 958 {
 959     if (s->rpc) {
 960         return jsonrpc_send(s->rpc, msg);
 961     } else {
 962         jsonrpc_msg_destroy(msg);
 963         return ENOTCONN;
 964     }
 965 }
 966
 967 struct jsonrpc_msg *
 968 jsonrpc_session_recv(struct jsonrpc_session *s)
 969 {
 970     if (s->rpc) {
 971         struct jsonrpc_msg *msg;
 972         jsonrpc_recv(s->rpc, &msg);
 973         if (msg) {
 974             reconnect_received(s->reconnect, time_msec());
 975             if (msg->type == JSONRPC_REQUEST && !strcmp(msg->method, "echo")) {
 976                 /* Echo request.  Send reply. */
 977                 struct jsonrpc_msg *reply;
 978
 979                 reply = jsonrpc_create_reply(json_clone(msg->params), msg->id);
 980                 jsonrpc_session_send(s, reply);
 981             } else if (msg->type == JSONRPC_REPLY
 982                        && msg->id && msg->id->type == JSON_STRING
 983                        && !strcmp(msg->id->u.string, "echo")) {
 984                 /* It's a reply to our echo request.  Suppress it. */
 985             } else {
 986                 return msg;
 987             }
 988             jsonrpc_msg_destroy(msg);
 989         }
 990     }
 991     return NULL;
 992 }
 993
 994 void
 995 jsonrpc_session_recv_wait(struct jsonrpc_session *s)
 996 {
 997     if (s->rpc) {
 998         jsonrpc_recv_wait(s->rpc);
 999     }
1000 }
1001
1002 bool
1003 jsonrpc_session_is_alive(const struct jsonrpc_session *s)
1004 {
1005     return s->rpc || s->stream || reconnect_get_max_tries(s->reconnect);
1006 }
1007
1008 bool
1009 jsonrpc_session_is_connected(const struct jsonrpc_session *s)
1010 {
1011     return s->rpc != NULL;
1012 }
1013
1014 unsigned int
1015 jsonrpc_session_get_seqno(const struct jsonrpc_session *s)
1016 {
1017     return s->seqno;
1018 }
1019
1020 int
1021 jsonrpc_session_get_status(const struct jsonrpc_session *s)
1022 {
1023     return s && s->rpc ? jsonrpc_get_status(s->rpc) : 0;
1024 }
1025
1026 void
1027 jsonrpc_session_get_reconnect_stats(const struct jsonrpc_session *s,
1028                                     struct reconnect_stats *stats)
1029 {
1030     reconnect_get_stats(s->reconnect, time_msec(), stats);
1031 }
1032
1033 void
1034 jsonrpc_session_force_reconnect(struct jsonrpc_session *s)
1035 {
1036     reconnect_force_reconnect(s->reconnect, time_msec());
1037 }
1038
1039 void
1040 jsonrpc_session_set_max_backoff(struct jsonrpc_session *s, int max_backoff)
1041 {
1042     reconnect_set_backoff(s->reconnect, 0, max_backoff);
1043 }
1044
1045 void
1046 jsonrpc_session_set_probe_interval(struct jsonrpc_session *s,
1047                                    int probe_interval)
1048 {
1049     reconnect_set_probe_interval(s->reconnect, probe_interval);
1050 }
1051
1052 void
1053 jsonrpc_session_set_dscp(struct jsonrpc_session *s,
1054                          uint8_t dscp)
1055 {
1056     reconnect_set_dscp(s->reconnect, dscp);
1057 }