text: /*
   * Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at:
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include <config.h>
  
  #include "jsonrpc.h"
  
  #include <errno.h>
  
  #include "byteq.h"
  #include "dynamic-string.h"
  #include "fatal-signal.h"
  #include "json.h"
  #include "list.h"
  #include "ofpbuf.h"
  #include "ovs-thread.h"
  #include "poll-loop.h"
  #include "reconnect.h"
  #include "stream.h"
  #include "timeval.h"
  #include "vlog.h"
  
  VLOG_DEFINE_THIS_MODULE(jsonrpc);
  
  struct jsonrpc {
      struct stream *stream;
      char *name;
      int status;
  
      /* Input. */
      struct byteq input;
      uint8_t input_buffer[512];
      struct json_parser *parser;
  
      /* Output. */
      struct list output;         /* Contains "struct ofpbuf"s. */
      size_t output_count;        /* Number of elements in "output". */
      size_t backlog;
  };
  
  /* Rate limit for error messages. */
  static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5);
  
  static struct jsonrpc_msg *jsonrpc_parse_received_message(struct jsonrpc *);
  static void jsonrpc_cleanup(struct jsonrpc *);
  static void jsonrpc_error(struct jsonrpc *, int error);
  
  /* This is just the same as stream_open() except that it uses the default
   * JSONRPC port if none is specified. */
  int
  jsonrpc_stream_open(const char *name, struct stream **streamp, uint8_t dscp)
  {
      return stream_open_with_default_port(name, OVSDB_OLD_PORT,
                                           streamp, dscp);
  }
  
  /* This is just the same as pstream_open() except that it uses the default
   * JSONRPC port if none is specified. */
  int
  jsonrpc_pstream_open(const char *name, struct pstream **pstreamp, uint8_t dscp)
  {
      return pstream_open_with_default_port(name, OVSDB_OLD_PORT,
                                            pstreamp, dscp);
  }
  
  /* Returns a new JSON-RPC stream that uses 'stream' for input and output.  The
   * new jsonrpc object takes ownership of 'stream'. */
  struct jsonrpc *
  jsonrpc_open(struct stream *stream)
  {
      struct jsonrpc *rpc;
  
      ovs_assert(stream != NULL);
  
      rpc = xzalloc(sizeof *rpc);
      rpc->name = xstrdup(stream_get_name(stream));
      rpc->stream = stream;
      byteq_init(&rpc->input, rpc->input_buffer, sizeof rpc->input_buffer);
      list_init(&rpc->output);
  
      return rpc;
  }
  
  /* Destroys 'rpc', closing the stream on which it is based, and frees its
   * memory. */
  void
  jsonrpc_close(struct jsonrpc *rpc)
  {
      if (rpc) {
          jsonrpc_cleanup(rpc);
          free(rpc->name);
          free(rpc);
      }
  }
  
  /* Performs periodic maintenance on 'rpc', such as flushing output buffers. */
  void
  jsonrpc_run(struct jsonrpc *rpc)
  {
      if (rpc->status) {
          return;
      }
  
      stream_run(rpc->stream);
      while (!list_is_empty(&rpc->output)) {
          struct ofpbuf *buf = ofpbuf_from_list(rpc->output.next);
          int retval;
  
          retval = stream_send(rpc->stream, ofpbuf_data(buf), ofpbuf_size(buf));
          if (retval >= 0) {
              rpc->backlog -= retval;
              ofpbuf_pull(buf, retval);
              if (!ofpbuf_size(buf)) {
                  list_remove(&buf->list_node);
                  rpc->output_count--;
                  ofpbuf_delete(buf);
              }
          } else {
              if (retval != -EAGAIN) {
                  VLOG_WARN_RL(&rl, "%s: send error: %s",
                               rpc->name, ovs_strerror(-retval));
                  jsonrpc_error(rpc, -retval);
              }
              break;
          }
      }
  }
  
  /* Arranges for the poll loop to wake up when 'rpc' needs to perform
   * maintenance activities. */
  void
  jsonrpc_wait(struct jsonrpc *rpc)
  {
      if (!rpc->status) {
          stream_run_wait(rpc->stream);
          if (!list_is_empty(&rpc->output)) {
              stream_send_wait(rpc->stream);
          }
      }
  }
  
  /*
   * Returns the current status of 'rpc'.  The possible return values are:
   * - 0: no error yet
   * - >0: errno value
   * - EOF: end of file (remote end closed connection; not necessarily an error).
   *
   * When this functions nonzero, 'rpc' is effectively out of commission.  'rpc'
   * will not receive any more messages and any further messages that one
   * attempts to send with 'rpc' will be discarded.  The caller can keep 'rpc'
   * around as long as it wants, but it's not going to provide any more useful
   * services.
   */
  int
  jsonrpc_get_status(const struct jsonrpc *rpc)
  {
      return rpc->status;
  }
  
  /* Returns the number of bytes buffered by 'rpc' to be written to the
   * underlying stream.  Always returns 0 if 'rpc' has encountered an error or if
   * the remote end closed the connection. */
  size_t
  jsonrpc_get_backlog(const struct jsonrpc *rpc)
  {
      return rpc->status ? 0 : rpc->backlog;
  }
  
  /* Returns the number of bytes that have been received on 'rpc''s underlying
   * stream.  (The value wraps around if it exceeds UINT_MAX.) */
  unsigned int
  jsonrpc_get_received_bytes(const struct jsonrpc *rpc)
  {
      return rpc->input.head;
  }
  
  /* Returns 'rpc''s name, that is, the name returned by stream_get_name() for
   * the stream underlying 'rpc' when 'rpc' was created. */
  const char *
  jsonrpc_get_name(const struct jsonrpc *rpc)
  {
      return rpc->name;
  }
  
  static void
  jsonrpc_log_msg(const struct jsonrpc *rpc, const char *title,
                  const struct jsonrpc_msg *msg)
  {
      if (VLOG_IS_DBG_ENABLED()) {
          struct ds s = DS_EMPTY_INITIALIZER;
          if (msg->method) {
              ds_put_format(&s, ", method=\"%s\"", msg->method);
          }
          if (msg->params) {
              ds_put_cstr(&s, ", params=");
              json_to_ds(msg->params, 0, &s);
          }
          if (msg->result) {
              ds_put_cstr(&s, ", result=");
              json_to_ds(msg->result, 0, &s);
          }
          if (msg->error) {
              ds_put_cstr(&s, ", error=");
              json_to_ds(msg->error, 0, &s);
          }
          if (msg->id) {
              ds_put_cstr(&s, ", id=");
              json_to_ds(msg->id, 0, &s);
          }
          VLOG_DBG("%s: %s %s%s", rpc->name, title,
                   jsonrpc_msg_type_to_string(msg->type), ds_cstr(&s));
          ds_destroy(&s);
      }
  }
  
  /* Schedules 'msg' to be sent on 'rpc' and returns 'rpc''s status (as with
   * jsonrpc_get_status()).
   *
   * If 'msg' cannot be sent immediately, it is appended to a buffer.  The caller
   * is responsible for ensuring that the amount of buffered data is somehow
   * limited.  (jsonrpc_get_backlog() returns the amount of data currently
   * buffered in 'rpc'.)
   *
   * Always takes ownership of 'msg', regardless of success. */
  int
  jsonrpc_send(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
  {
      struct ofpbuf *buf;
      struct json *json;
      size_t length;
      char *s;
  
      if (rpc->status) {
          jsonrpc_msg_destroy(msg);
          return rpc->status;
      }
  
      jsonrpc_log_msg(rpc, "send", msg);
  
      json = jsonrpc_msg_to_json(msg);
      s = json_to_string(json, 0);
      length = strlen(s);
      json_destroy(json);
  
      buf = xmalloc(sizeof *buf);
      ofpbuf_use(buf, s, length);
      ofpbuf_set_size(buf, length);
      list_push_back(&rpc->output, &buf->list_node);
      rpc->output_count++;
      rpc->backlog += length;
  
      if (rpc->output_count >= 50) {
          VLOG_INFO_RL(&rl, "excessive sending backlog, jsonrpc: %s, num of"
                       " msgs: %"PRIuSIZE", backlog: %"PRIuSIZE".", rpc->name,
                       rpc->output_count, rpc->backlog);
      }
  
      if (rpc->backlog == length) {
          jsonrpc_run(rpc);
      }
      return rpc->status;
  }
  
  /* Attempts to receive a message from 'rpc'.
   *
   * If successful, stores the received message in '*msgp' and returns 0.  The
   * caller takes ownership of '*msgp' and must eventually destroy it with
   * jsonrpc_msg_destroy().
   *
   * Otherwise, stores NULL in '*msgp' and returns one of the following:
   *
   *   - EAGAIN: No message has been received.
   *
   *   - EOF: The remote end closed the connection gracefully.
   *
   *   - Otherwise an errno value that represents a JSON-RPC protocol violation
   *     or another error fatal to the connection.  'rpc' will not send or
   *     receive any more messages.
   */
  int
  jsonrpc_recv(struct jsonrpc *rpc, struct jsonrpc_msg **msgp)
  {
      int i;
  
      *msgp = NULL;
      if (rpc->status) {
          return rpc->status;
      }
  
      for (i = 0; i < 50; i++) {
          size_t n, used;
  
          /* Fill our input buffer if it's empty. */
          if (byteq_is_empty(&rpc->input)) {
              size_t chunk;
              int retval;
  
              chunk = byteq_headroom(&rpc->input);
              retval = stream_recv(rpc->stream, byteq_head(&rpc->input), chunk);
              if (retval < 0) {
                  if (retval == -EAGAIN) {
                      return EAGAIN;
                  } else {
                      VLOG_WARN_RL(&rl, "%s: receive error: %s",
                                   rpc->name, ovs_strerror(-retval));
                      jsonrpc_error(rpc, -retval);
                      return rpc->status;
                  }
              } else if (retval == 0) {
                  jsonrpc_error(rpc, EOF);
                  return EOF;
              }
              byteq_advance_head(&rpc->input, retval);
          }
  
          /* We have some input.  Feed it into the JSON parser. */
          if (!rpc->parser) {
              rpc->parser = json_parser_create(0);
          }
          n = byteq_tailroom(&rpc->input);
          used = json_parser_feed(rpc->parser,
                                  (char *) byteq_tail(&rpc->input), n);
          byteq_advance_tail(&rpc->input, used);
  
          /* If we have complete JSON, attempt to parse it as JSON-RPC. */
          if (json_parser_is_done(rpc->parser)) {
              *msgp = jsonrpc_parse_received_message(rpc);
              if (*msgp) {
                  return 0;
              }
  
              if (rpc->status) {
                  const struct byteq *q = &rpc->input;
                  if (q->head <= q->size) {
                      stream_report_content(q->buffer, q->head, STREAM_JSONRPC,
                                            THIS_MODULE, rpc->name);
                  }
                  return rpc->status;
              }
          }
      }
  
      return EAGAIN;
  }
  
  /* Causes the poll loop to wake up when jsonrpc_recv() may return a value other
   * than EAGAIN. */
  void
  jsonrpc_recv_wait(struct jsonrpc *rpc)
  {
      if (rpc->status || !byteq_is_empty(&rpc->input)) {
          poll_immediate_wake_at(rpc->name);
      } else {
          stream_recv_wait(rpc->stream);
      }
  }
  
  /* Sends 'msg' on 'rpc' and waits for it to be successfully queued to the
   * underlying stream.  Returns 0 if 'msg' was sent successfully, otherwise a
   * status value (see jsonrpc_get_status()).
   *
   * Always takes ownership of 'msg', regardless of success. */
  int
  jsonrpc_send_block(struct jsonrpc *rpc, struct jsonrpc_msg *msg)
  {
      int error;
  
      fatal_signal_run();
  
      error = jsonrpc_send(rpc, msg);
      if (error) {
          return error;
      }
  
      for (;;) {
          jsonrpc_run(rpc);
          if (list_is_empty(&rpc->output) || rpc->status) {
              return rpc->status;
          }
          jsonrpc_wait(rpc);
          poll_block();
      }
  }
  
  /* Waits for a message to be received on 'rpc'.  Same semantics as
   * jsonrpc_recv() except that EAGAIN will never be returned. */
  int
  jsonrpc_recv_block(struct jsonrpc *rpc, struct jsonrpc_msg **msgp)
  {
      for (;;) {
          int error = jsonrpc_recv(rpc, msgp);
          if (error != EAGAIN) {
              fatal_signal_run();
              return error;
          }
  
          jsonrpc_run(rpc);
          jsonrpc_wait(rpc);
          jsonrpc_recv_wait(rpc);
          poll_block();
      }
  }
  
  /* Sends 'request' to 'rpc' then waits for a reply.  The return value is 0 if
   * successful, in which case '*replyp' is set to the reply, which the caller
   * must eventually free with jsonrpc_msg_destroy().  Otherwise returns a status
   * value (see jsonrpc_get_status()).
   *
   * Discards any message received on 'rpc' that is not a reply to 'request'
   * (based on message id).
   *
   * Always takes ownership of 'request', regardless of success. */
  int
  jsonrpc_transact_block(struct jsonrpc *rpc, struct jsonrpc_msg *request,
                         struct jsonrpc_msg **replyp)
  {
      struct jsonrpc_msg *reply = NULL;
      struct json *id;
      int error;
  
      id = json_clone(request->id);
      error = jsonrpc_send_block(rpc, request);
      if (!error) {
          for (;;) {
              error = jsonrpc_recv_block(rpc, &reply);
              if (error) {
                  break;
              }
              if ((reply->type == JSONRPC_REPLY || reply->type == JSONRPC_ERROR)
                  && json_equal(id, reply->id)) {
                  break;
              }
              jsonrpc_msg_destroy(reply);
          }
      }
      *replyp = error ? NULL : reply;
      json_destroy(id);
      return error;
  }
  
  /* Attempts to parse the content of 'rpc->parser' (which is complete JSON) as a
   * JSON-RPC message.  If successful, returns the JSON-RPC message.  On failure,
   * signals an error on 'rpc' with jsonrpc_error() and returns NULL. */
  static struct jsonrpc_msg *
  jsonrpc_parse_received_message(struct jsonrpc *rpc)
  {
      struct jsonrpc_msg *msg;
      struct json *json;
      char *error;
  
      json = json_parser_finish(rpc->parser);
      rpc->parser = NULL;
      if (json->type == JSON_STRING) {
          VLOG_WARN_RL(&rl, "%s: error parsing stream: %s",
                       rpc->name, json_string(json));
          jsonrpc_error(rpc, EPROTO);
          json_destroy(json);
          return NULL;
      }
  
      error = jsonrpc_msg_from_json(json, &msg);
      if (error) {
          VLOG_WARN_RL(&rl, "%s: received bad JSON-RPC message: %s",
                       rpc->name, error);
          free(error);
          jsonrpc_error(rpc, EPROTO);
          return NULL;
      }
  
      jsonrpc_log_msg(rpc, "received", msg);
      return msg;
  }
  
  static void
  jsonrpc_error(struct jsonrpc *rpc, int error)
  {
      ovs_assert(error);
      if (!rpc->status) {
          rpc->status = error;
          jsonrpc_cleanup(rpc);
      }
  }
  
  static void
  jsonrpc_cleanup(struct jsonrpc *rpc)
  {
      stream_close(rpc->stream);
      rpc->stream = NULL;
  
      json_parser_abort(rpc->parser);
      rpc->parser = NULL;
  
      ofpbuf_list_delete(&rpc->output);
      rpc->backlog = 0;
      rpc->output_count = 0;
  }
  
  static struct jsonrpc_msg *
  jsonrpc_create(enum jsonrpc_msg_type type, const char *method,
                  struct json *params, struct json *result, struct json *error,
                  struct json *id)
  {
      struct jsonrpc_msg *msg = xmalloc(sizeof *msg);
      msg->type = type;
      msg->method = method ? xstrdup(method) : NULL;
      msg->params = params;
      msg->result = result;
      msg->error = error;
      msg->id = id;
      return msg;
  }
  
  static struct json *
  jsonrpc_create_id(void)
  {
      static atomic_uint next_id = ATOMIC_VAR_INIT(0);
      unsigned int id;
  
      atomic_add(&next_id, 1, &id);
      return json_integer_create(id);
  }
  
  struct jsonrpc_msg *
  jsonrpc_create_request(const char *method, struct json *params,
                         struct json **idp)
  {
      struct json *id = jsonrpc_create_id();
      if (idp) {
          *idp = json_clone(id);
      }
      return jsonrpc_create(JSONRPC_REQUEST, method, params, NULL, NULL, id);
  }
  
  struct jsonrpc_msg *
  jsonrpc_create_notify(const char *method, struct json *params)
  {
      return jsonrpc_create(JSONRPC_NOTIFY, method, params, NULL, NULL, NULL);
  }
  
  struct jsonrpc_msg *
  jsonrpc_create_reply(struct json *result, const struct json *id)
  {
      return jsonrpc_create(JSONRPC_REPLY, NULL, NULL, result, NULL,
                             json_clone(id));
  }
  
  struct jsonrpc_msg *
  jsonrpc_create_error(struct json *error, const struct json *id)
  {
      return jsonrpc_create(JSONRPC_REPLY, NULL, NULL, NULL, error,
                             json_clone(id));
  }
  
  const char *
  jsonrpc_msg_type_to_string(enum jsonrpc_msg_type type)
  {
      switch (type) {
      case JSONRPC_REQUEST:
          return "request";
  
      case JSONRPC_NOTIFY:
          return "notification";
  
      case JSONRPC_REPLY:
          return "reply";
  
      case JSONRPC_ERROR:
          return "error";
      }
      return "(null)";
  }
  
  char *
  jsonrpc_msg_is_valid(const struct jsonrpc_msg *m)
  {
      const char *type_name;
      unsigned int pattern;
  
      if (m->params && m->params->type != JSON_ARRAY) {
          return xstrdup("\"params\" must be JSON array");
      }
  
      switch (m->type) {
      case JSONRPC_REQUEST:
          pattern = 0x11001;
          break;
  
      case JSONRPC_NOTIFY:
          pattern = 0x11000;
          break;
  
      case JSONRPC_REPLY:
          pattern = 0x00101;
          break;
  
      case JSONRPC_ERROR:
          pattern = 0x00011;
          break;
  
      default:
          return xasprintf("invalid JSON-RPC message type %d", m->type);
      }
  
      type_name = jsonrpc_msg_type_to_string(m->type);
      if ((m->method != NULL) != ((pattern & 0x10000) != 0)) {
          return xasprintf("%s must%s have \"method\"",
                           type_name, (pattern & 0x10000) ? "" : " not");
  
      }
      if ((m->params != NULL) != ((pattern & 0x1000) != 0)) {
          return xasprintf("%s must%s have \"params\"",
                           type_name, (pattern & 0x1000) ? "" : " not");
  
      }
      if ((m->result != NULL) != ((pattern & 0x100) != 0)) {
          return xasprintf("%s must%s have \"result\"",
                           type_name, (pattern & 0x100) ? "" : " not");
  
      }
      if ((m->error != NULL) != ((pattern & 0x10) != 0)) {
          return xasprintf("%s must%s have \"error\"",
                           type_name, (pattern & 0x10) ? "" : " not");
  
      }
      if ((m->id != NULL) != ((pattern & 0x1) != 0)) {
          return xasprintf("%s must%s have \"id\"",
                           type_name, (pattern & 0x1) ? "" : " not");
  
      }
      return NULL;
  }
  
  void
  jsonrpc_msg_destroy(struct jsonrpc_msg *m)
  {
      if (m) {
          free(m->method);
          json_destroy(m->params);
          json_destroy(m->result);
          json_destroy(m->error);
          json_destroy(m->id);
          free(m);
      }
  }
  
  static struct json *
  null_from_json_null(struct json *json)
  {
      if (json && json->type == JSON_NULL) {
          json_destroy(json);
          return NULL;
      }
      return json;
  }
  
  char *
  jsonrpc_msg_from_json(struct json *json, struct jsonrpc_msg **msgp)
  {
      struct json *method = NULL;
      struct jsonrpc_msg *msg = NULL;
      struct shash *object;
      char *error;
  
      if (json->type != JSON_OBJECT) {
          error = xstrdup("message is not a JSON object");
          goto exit;
      }
      object = json_object(json);
  
      method = shash_find_and_delete(object, "method");
      if (method && method->type != JSON_STRING) {
          error = xstrdup("method is not a JSON string");
          goto exit;
      }
  
      msg = xzalloc(sizeof *msg);
      msg->method = method ? xstrdup(method->u.string) : NULL;
      msg->params = null_from_json_null(shash_find_and_delete(object, "params"));
      msg->result = null_from_json_null(shash_find_and_delete(object, "result"));
      msg->error = null_from_json_null(shash_find_and_delete(object, "error"));
      msg->id = null_from_json_null(shash_find_and_delete(object, "id"));
      msg->type = (msg->result ? JSONRPC_REPLY
                   : msg->error ? JSONRPC_ERROR
                   : msg->id ? JSONRPC_REQUEST
                   : JSONRPC_NOTIFY);
      if (!shash_is_empty(object)) {
          error = xasprintf("message has unexpected member \"%s\"",
                            shash_first(object)->name);
          goto exit;
      }
      error = jsonrpc_msg_is_valid(msg);
      if (error) {
          goto exit;
      }
  
  exit:
      json_destroy(method);
      json_destroy(json);
      if (error) {
          jsonrpc_msg_destroy(msg);
          msg = NULL;
      }
      *msgp = msg;
      return error;
  }
  
  struct json *
  jsonrpc_msg_to_json(struct jsonrpc_msg *m)
  {
      struct json *json = json_object_create();
  
      if (m->method) {
          json_object_put(json, "method", json_string_create_nocopy(m->method));
      }
  
      if (m->params) {
          json_object_put(json, "params", m->params);
      }
  
      if (m->result) {
          json_object_put(json, "result", m->result);
      } else if (m->type == JSONRPC_ERROR) {
          json_object_put(json, "result", json_null_create());
      }
  
      if (m->error) {
          json_object_put(json, "error", m->error);
      } else if (m->type == JSONRPC_REPLY) {
          json_object_put(json, "error", json_null_create());
      }
  
      if (m->id) {
          json_object_put(json, "id", m->id);
      } else if (m->type == JSONRPC_NOTIFY) {
          json_object_put(json, "id", json_null_create());
      }
  
      free(m);
  
      return json;
  }
  
  /* A JSON-RPC session with reconnection. */
  
  struct jsonrpc_session {
      struct reconnect *reconnect;
      struct jsonrpc *rpc;
      struct stream *stream;
      struct pstream *pstream;
      int last_error;
      unsigned int seqno;
      uint8_t dscp;
  };
  
  /* Creates and returns a jsonrpc_session to 'name', which should be a string
   * acceptable to stream_open() or pstream_open().
   *
   * If 'name' is an active connection method, e.g. "tcp:127.1.2.3", the new
   * jsonrpc_session connects to 'name'.  If 'retry' is true, then the new
   * session connects and reconnects to 'name', with backoff.  If 'retry' is
   * false, the new session will only try to connect once and after a connection
   * failure or a disconnection jsonrpc_session_is_alive() will return false for
   * the new session.
   *
   * If 'name' is a passive connection method, e.g. "ptcp:", the new
   * jsonrpc_session listens for connections to 'name'.  It maintains at most one
   * connection at any given time.  Any new connection causes the previous one
   * (if any) to be dropped. */
  struct jsonrpc_session *
  jsonrpc_session_open(const char *name, bool retry)
  {
      struct jsonrpc_session *s;
  
      s = xmalloc(sizeof *s);
      s->reconnect = reconnect_create(time_msec());
      reconnect_set_name(s->reconnect, name);
      reconnect_enable(s->reconnect, time_msec());
      s->rpc = NULL;
      s->stream = NULL;
      s->pstream = NULL;
      s->seqno = 0;
      s->dscp = 0;
      s->last_error = 0;
  
      if (!pstream_verify_name(name)) {
          reconnect_set_passive(s->reconnect, true, time_msec());
      } else if (!retry) {
          reconnect_set_max_tries(s->reconnect, 1);
          reconnect_set_backoff(s->reconnect, INT_MAX, INT_MAX);
      }
  
      if (!stream_or_pstream_needs_probes(name)) {
          reconnect_set_probe_interval(s->reconnect, 0);
      }
  
      return s;
  }
  
  /* Creates and returns a jsonrpc_session that is initially connected to
   * 'jsonrpc'.  If the connection is dropped, it will not be reconnected.
   *
   * On the assumption that such connections are likely to be short-lived
   * (e.g. from ovs-vsctl), informational logging for them is suppressed. */
  struct jsonrpc_session *
  jsonrpc_session_open_unreliably(struct jsonrpc *jsonrpc, uint8_t dscp)
  {
      struct jsonrpc_session *s;
  
      s = xmalloc(sizeof *s);
      s->reconnect = reconnect_create(time_msec());
      reconnect_set_quiet(s->reconnect, true);
      reconnect_set_name(s->reconnect, jsonrpc_get_name(jsonrpc));
      reconnect_set_max_tries(s->reconnect, 0);
      reconnect_connected(s->reconnect, time_msec());
      s->dscp = dscp;
      s->rpc = jsonrpc;
      s->stream = NULL;
      s->pstream = NULL;
      s->seqno = 0;
  
      return s;
  }
  
  void
  jsonrpc_session_close(struct jsonrpc_session *s)
  {
      if (s) {
          jsonrpc_close(s->rpc);
          reconnect_destroy(s->reconnect);
          stream_close(s->stream);
          pstream_close(s->pstream);
          free(s);
      }
  }
  
  static void
  jsonrpc_session_disconnect(struct jsonrpc_session *s)
  {
      if (s->rpc) {
          jsonrpc_error(s->rpc, EOF);
          jsonrpc_close(s->rpc);
          s->rpc = NULL;
          s->seqno++;
      } else if (s->stream) {
          stream_close(s->stream);
          s->stream = NULL;
          s->seqno++;
      }
  }
  
  static void
  jsonrpc_session_connect(struct jsonrpc_session *s)
  {
      const char *name = reconnect_get_name(s->reconnect);
      int error;
  
      jsonrpc_session_disconnect(s);
      if (!reconnect_is_passive(s->reconnect)) {
          error = jsonrpc_stream_open(name, &s->stream, s->dscp);
          if (!error) {
              reconnect_connecting(s->reconnect, time_msec());
          } else {
              s->last_error = error;
          }
      } else {
          error = s->pstream ? 0 : jsonrpc_pstream_open(name, &s->pstream,
                                                        s->dscp);
          if (!error) {
              reconnect_listening(s->reconnect, time_msec());
          }
      }
  
      if (error) {
          reconnect_connect_failed(s->reconnect, time_msec(), error);
      }
      s->seqno++;
  }
  
  void
  jsonrpc_session_run(struct jsonrpc_session *s)
  {
      if (s->pstream) {
          struct stream *stream;
          int error;
  
          error = pstream_accept(s->pstream, &stream);
          if (!error) {
              if (s->rpc || s->stream) {
                  VLOG_INFO_RL(&rl,
                               "%s: new connection replacing active connection",
                               reconnect_get_name(s->reconnect));
                  jsonrpc_session_disconnect(s);
              }
              reconnect_connected(s->reconnect, time_msec());
              s->rpc = jsonrpc_open(stream);
          } else if (error != EAGAIN) {
              reconnect_listen_error(s->reconnect, time_msec(), error);
              pstream_close(s->pstream);
              s->pstream = NULL;
          }
      }
  
      if (s->rpc) {
          size_t backlog;
          int error;
  
          backlog = jsonrpc_get_backlog(s->rpc);
          jsonrpc_run(s->rpc);
          if (jsonrpc_get_backlog(s->rpc) < backlog) {
              /* Data previously caught in a queue was successfully sent (or
               * there's an error, which we'll catch below.)
               *
               * We don't count data that is successfully sent immediately as
               * activity, because there's a lot of queuing downstream from us,
               * which means that we can push a lot of data into a connection
               * that has stalled and won't ever recover.
               */
              reconnect_activity(s->reconnect, time_msec());
          }
  
          error = jsonrpc_get_status(s->rpc);
          if (error) {
              reconnect_disconnected(s->reconnect, time_msec(), error);
              jsonrpc_session_disconnect(s);
              s->last_error = error;
          }
      } else if (s->stream) {
          int error;
  
          stream_run(s->stream);
          error = stream_connect(s->stream);
          if (!error) {
              reconnect_connected(s->reconnect, time_msec());
              s->rpc = jsonrpc_open(s->stream);
              s->stream = NULL;
          } else if (error != EAGAIN) {
              reconnect_connect_failed(s->reconnect, time_msec(), error);
              stream_close(s->stream);
              s->stream = NULL;
          }
      }
  
      switch (reconnect_run(s->reconnect, time_msec())) {
      case RECONNECT_CONNECT:
          jsonrpc_session_connect(s);
          break;
  
      case RECONNECT_DISCONNECT:
          reconnect_disconnected(s->reconnect, time_msec(), 0);
          jsonrpc_session_disconnect(s);
          break;
  
      case RECONNECT_PROBE:
          if (s->rpc) {
              struct json *params;
              struct jsonrpc_msg *request;
  
              params = json_array_create_empty();
              request = jsonrpc_create_request("echo", params, NULL);
              json_destroy(request->id);
              request->id = json_string_create("echo");
              jsonrpc_send(s->rpc, request);
          }
          break;
      }
  }
  
  void
  jsonrpc_session_wait(struct jsonrpc_session *s)
  {
      if (s->rpc) {
          jsonrpc_wait(s->rpc);
      } else if (s->stream) {
          stream_run_wait(s->stream);
          stream_connect_wait(s->stream);
      }
      if (s->pstream) {
          pstream_wait(s->pstream);
      }
      reconnect_wait(s->reconnect, time_msec());
  }
  
  size_t
  jsonrpc_session_get_backlog(const struct jsonrpc_session *s)
  {
      return s->rpc ? jsonrpc_get_backlog(s->rpc) : 0;
  }
  
  /* Always returns a pointer to a valid C string, assuming 's' was initialized
   * correctly. */
  const char *
  jsonrpc_session_get_name(const struct jsonrpc_session *s)
  {
      return reconnect_get_name(s->reconnect);
  }
  
  /* Always takes ownership of 'msg', regardless of success. */
  int
  jsonrpc_session_send(struct jsonrpc_session *s, struct jsonrpc_msg *msg)
  {
      if (s->rpc) {
          return jsonrpc_send(s->rpc, msg);
      } else {
          jsonrpc_msg_destroy(msg);
          return ENOTCONN;
      }
  }
  
  struct jsonrpc_msg *
  jsonrpc_session_recv(struct jsonrpc_session *s)
  {
      if (s->rpc) {
          unsigned int received_bytes;
          struct jsonrpc_msg *msg;
  
          received_bytes = jsonrpc_get_received_bytes(s->rpc);
          jsonrpc_recv(s->rpc, &msg);
          if (received_bytes != jsonrpc_get_received_bytes(s->rpc)) {
              /* Data was successfully received.
               *
               * Previously we only counted receiving a full message as activity,
               * but with large messages or a slow connection that policy could
               * time out the session mid-message. */
              reconnect_activity(s->reconnect, time_msec());
          }
  
          if (msg) {
              if (msg->type == JSONRPC_REQUEST && !strcmp(msg->method, "echo")) {
                  /* Echo request.  Send reply. */
                  struct jsonrpc_msg *reply;
  
                  reply = jsonrpc_create_reply(json_clone(msg->params), msg->id);
                  jsonrpc_session_send(s, reply);
              } else if (msg->type == JSONRPC_REPLY
                         && msg->id && msg->id->type == JSON_STRING
                         && !strcmp(msg->id->u.string, "echo")) {
                  /* It's a reply to our echo request.  Suppress it. */
              } else {
                  return msg;
              }
              jsonrpc_msg_destroy(msg);
          }
      }
      return NULL;
  }
  
  void
  jsonrpc_session_recv_wait(struct jsonrpc_session *s)
  {
      if (s->rpc) {
          jsonrpc_recv_wait(s->rpc);
      }
  }
  
  bool
  jsonrpc_session_is_alive(const struct jsonrpc_session *s)
  {
      return s->rpc || s->stream || reconnect_get_max_tries(s->reconnect);
  }
  
  bool
  jsonrpc_session_is_connected(const struct jsonrpc_session *s)
  {
      return s->rpc != NULL;
  }
  
  unsigned int
  jsonrpc_session_get_seqno(const struct jsonrpc_session *s)
  {
      return s->seqno;
  }
  
  int
  jsonrpc_session_get_status(const struct jsonrpc_session *s)
  {
      return s && s->rpc ? jsonrpc_get_status(s->rpc) : 0;
  }
  
  int
  jsonrpc_session_get_last_error(const struct jsonrpc_session *s)
  {
      return s->last_error;
  }
  
  void
  jsonrpc_session_get_reconnect_stats(const struct jsonrpc_session *s,
                                      struct reconnect_stats *stats)
  {
      reconnect_get_stats(s->reconnect, time_msec(), stats);
  }
  
  void
  jsonrpc_session_enable_reconnect(struct jsonrpc_session *s)
  {
      reconnect_set_max_tries(s->reconnect, UINT_MAX);
      reconnect_set_backoff(s->reconnect, RECONNECT_DEFAULT_MIN_BACKOFF,
                            RECONNECT_DEFAULT_MAX_BACKOFF);
  }
  
  void
  jsonrpc_session_force_reconnect(struct jsonrpc_session *s)
  {
      reconnect_force_reconnect(s->reconnect, time_msec());
  }
  
  void
  jsonrpc_session_set_max_backoff(struct jsonrpc_session *s, int max_backoff)
  {
      reconnect_set_backoff(s->reconnect, 0, max_backoff);
  }
  
  void
  jsonrpc_session_set_probe_interval(struct jsonrpc_session *s,
                                     int probe_interval)
  {
      reconnect_set_probe_interval(s->reconnect, probe_interval);
  }
  
  void
  jsonrpc_session_set_dscp(struct jsonrpc_session *s,
                           uint8_t dscp)
  {
      if (s->dscp != dscp) {
          if (s->pstream) {
              int error;
  
              error = pstream_set_dscp(s->pstream, dscp);
              if (error) {
                  VLOG_ERR("%s: failed set_dscp %s",
                           reconnect_get_name(s->reconnect),
                           ovs_strerror(error));
              }
              /*
               * XXX race window between setting dscp to listening socket
               * and accepting socket. accepted socket may have old dscp value.
               * Ignore this race window for now.
               */
          }
          s->dscp = dscp;
          jsonrpc_session_force_reconnect(s);
      }
  }
  