text: /* Copyright (c) 2008, 2009 The Board of Trustees of The Leland Stanford
   * Junior University
   * 
   * We are making the OpenFlow specification and associated documentation
   * (Software) available for public use and benefit with the expectation
   * that others will use, modify and enhance the Software and contribute
   * those enhancements back to the community. However, since we would
   * like to make the Software available for broadest use, with as few
   * restrictions as possible permission is hereby granted, free of
   * charge, to any person obtaining a copy of this Software to deal in
   * the Software under the copyrights without restriction, including
   * without limitation the rights to use, copy, modify, merge, publish,
   * distribute, sublicense, and/or sell copies of the Software, and to
   * permit persons to whom the Software is furnished to do so, subject to
   * the following conditions:
   * 
   * The above copyright notice and this permission notice shall be
   * included in all copies or substantial portions of the Software.
   * 
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
   * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
   * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   * 
   * The name and trademarks of copyright holder(s) may NOT be used in
   * advertising or publicity pertaining to the Software or any
   * derivatives without specific, written prior permission.
   */
  
  #include <config.h>
  #include "vconn-provider.h"
  #include <assert.h>
  #include <errno.h>
  #include <inttypes.h>
  #include <netinet/in.h>
  #include <poll.h>
  #include <stdlib.h>
  #include <string.h>
  #include "dynamic-string.h"
  #include "ofp.h"
  #include "ofpbuf.h"
  #include "openflow/openflow.h"
  #include "poll-loop.h"
  #include "random.h"
  #include "util.h"
  #include "oflib/ofl.h"
  #include "oflib/ofl-messages.h"
  #include "oflib-exp/ofl-exp.h"
  
  #define LOG_MODULE VLM_vconn
  #include "vlog.h"
  
  /* State of an active vconn.*/
  enum vconn_state {
      /* This is the ordinary progression of states. */
      VCS_CONNECTING,             /* Underlying vconn is not connected. */
      VCS_SEND_HELLO,             /* Waiting to send OFPT_HELLO message. */
      VCS_RECV_HELLO,             /* Waiting to receive OFPT_HELLO message. */
      VCS_CONNECTED,              /* Connection established. */
  
      /* These states are entered only when something goes wrong. */
      VCS_SEND_ERROR,             /* Sending OFPT_ERROR message. */
      VCS_DISCONNECTED            /* Connection failed or connection closed. */
  };
  
  static struct ofl_exp_msg ofl_exp_msg =
          {.pack      = ofl_exp_msg_pack,
           .unpack    = ofl_exp_msg_unpack,
           .free      = ofl_exp_msg_free,
           .to_string = ofl_exp_msg_to_string};
  
  static struct ofl_exp_act ofl_exp_act =
          {.pack      = OFDPA_ofl_exp_action_pack,
           .unpack    = OFDPA_ofl_exp_action_unpack,
           .free      = OFDPA_ofl_exp_action_free,
           .ofp_len   = OFDPA_ofl_exp_action_ofp_len,
           .to_string = OFDPA_ofl_exp_action_to_string};
  static struct ofl_exp ofl_exp =
          {.act   = &ofl_exp_act,
           .inst  = NULL,
           .match = NULL,
           .stats = NULL,
           .msg   = &ofl_exp_msg};
  static struct vconn_class *vconn_classes[] = {
      &tcp_vconn_class,
      &unix_vconn_class,
  #ifdef HAVE_NETLINK
      &netlink_vconn_class,
  #endif
  #ifdef HAVE_OPENSSL
      &ssl_vconn_class,
  #endif
  };
  
  static struct pvconn_class *pvconn_classes[] = {
      &ptcp_pvconn_class,
      &punix_pvconn_class,
  #ifdef HAVE_OPENSSL
      &pssl_pvconn_class,
  #endif
  };
  
  /* High rate limit because most of the rate-limiting here is individual
   * OpenFlow messages going over the vconn.  If those are enabled then we
   * really need to see them. */
  static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(600, 600);
  
  static int do_recv(struct vconn *, struct ofpbuf **);
  static int do_send(struct vconn *, struct ofpbuf *);
  
  /* Check the validity of the vconn class structures. */
  static void
  check_vconn_classes(void)
  {
  #ifndef NDEBUG
      size_t i;
  
      for (i = 0; i < ARRAY_SIZE(vconn_classes); i++) {
          struct vconn_class *class = vconn_classes[i];
          assert(class->name != NULL);
          assert(class->open != NULL);
          if (class->close || class->recv || class->send || class->wait) {
              assert(class->close != NULL);
              assert(class->recv != NULL);
              assert(class->send != NULL);
              assert(class->wait != NULL);
          } else {
              /* This class delegates to another one. */
          }
      }
  
      for (i = 0; i < ARRAY_SIZE(pvconn_classes); i++) {
          struct pvconn_class *class = pvconn_classes[i];
          assert(class->name != NULL);
          assert(class->listen != NULL);
          if (class->close || class->accept || class->wait) {
              assert(class->close != NULL);
              assert(class->accept != NULL);
              assert(class->wait != NULL);
          } else {
              /* This class delegates to another one. */
          }
      }
  #endif
  }
  
  /* Prints information on active (if 'active') and passive (if 'passive')
   * connection methods supported by the vconn.  If 'bootstrap' is true, also
   * advertises options to bootstrap the CA certificate. */
  void
  vconn_usage(bool active, bool passive, bool bootstrap UNUSED)
  {
      /* Really this should be implemented via callbacks into the vconn
       * providers, but that seems too heavy-weight to bother with at the
       * moment. */
      
      printf("\n");
      if (active) {
          printf("Active OpenFlow connection methods:\n");
          printf("  tcp:HOST[:PORT]         "
                 "PORT (default: %d) on remote TCP HOST\n", OFP_TCP_PORT);
  #ifdef HAVE_OPENSSL
          printf("  ssl:HOST[:PORT]         "
                 "SSL PORT (default: %d) on remote HOST\n", OFP_SSL_PORT);
  #endif
          printf("  unix:FILE               Unix domain socket named FILE\n");
          printf("  fd:N                    File descriptor N\n");
      }
  
      if (passive) {
          printf("Passive OpenFlow connection methods:\n");
          printf("  ptcp:[PORT]             "
                 "listen to TCP PORT (default: %d)\n",
                 OFP_TCP_PORT);
  #ifdef HAVE_OPENSSL
          printf("  pssl:[PORT]             "
                 "listen for SSL on PORT (default: %d)\n",
                 OFP_SSL_PORT);
  #endif
          printf("  punix:FILE              "
                 "listen on Unix domain socket FILE\n");
      }
  
  #ifdef HAVE_OPENSSL
      printf("PKI configuration (required to use SSL):\n"
             "  -p, --private-key=FILE  file with private key\n"
             "  -c, --certificate=FILE  file with certificate for private key\n"
             "  -C, --ca-cert=FILE      file with peer CA certificate\n");
      if (bootstrap) {
          printf("  --bootstrap-ca-cert=FILE  file with peer CA certificate "
                 "to read or create\n");
      }
  #endif
  }
  
  /* Attempts to connect to an OpenFlow device.  'name' is a connection name in
   * the form "TYPE:ARGS", where TYPE is an active vconn class's name and ARGS
   * are vconn class-specific.
   *
   * The vconn will automatically negotiate an OpenFlow protocol version
   * acceptable to both peers on the connection.  The version negotiated will be
   * no lower than 'min_version' and no higher than OFP_VERSION.
   *
   * Returns 0 if successful, otherwise a positive errno value.  If successful,
   * stores a pointer to the new connection in '*vconnp', otherwise a null
   * pointer.  */
  int
  vconn_open(const char *name, int min_version, struct vconn **vconnp)
  {
      size_t prefix_len;
      size_t i;
  
      check_vconn_classes();
  
      *vconnp = NULL;
      prefix_len = strcspn(name, ":");
      if (prefix_len == strlen(name)) {
          return EAFNOSUPPORT;
      }
      for (i = 0; i < ARRAY_SIZE(vconn_classes); i++) {
          struct vconn_class *class = vconn_classes[i];
          if (strlen(class->name) == prefix_len
              && !memcmp(class->name, name, prefix_len)) {
              struct vconn *vconn;
              char *suffix_copy = xstrdup(name + prefix_len + 1);
              int retval = class->open(name, suffix_copy, &vconn);
              free(suffix_copy);
              if (!retval) {
                  assert(vconn->state != VCS_CONNECTING
                         || vconn->class->connect);
                  vconn->min_version = min_version;
                  *vconnp = vconn;
              }
              return retval;
          }
      }
      return EAFNOSUPPORT;
  }
  
  int
  vconn_open_block(const char *name, int min_version, struct vconn **vconnp)
  {
      struct vconn *vconn;
      int error;
  
      error = vconn_open(name, min_version, &vconn);
      while (error == EAGAIN) {
          vconn_connect_wait(vconn);
          poll_block();
          error = vconn_connect(vconn,NULL,false);
          assert(error != EINPROGRESS);
      }
      if (error) {
          vconn_close(vconn);
          *vconnp = NULL;
      } else {
          *vconnp = vconn;
      }
      return error;
  }
  
  /* Closes 'vconn'. */
  void
  vconn_close(struct vconn *vconn)
  {
      if (vconn != NULL) {
          char *name = vconn->name;
          (vconn->class->close)(vconn);
          free(name);
      }
  }
  
  /* Returns the name of 'vconn', that is, the string passed to vconn_open(). */
  const char *
  vconn_get_name(const struct vconn *vconn)
  {
      return vconn->name;
  }
  
  /* Returns the IP address of the peer, or 0 if the peer is not connected over
   * an IP-based protocol or if its IP address is not yet known. */
  uint32_t
  vconn_get_ip(const struct vconn *vconn) 
  {
      return vconn->ip;
  }
  
  /* Returns true if, when 'vconn' is closed, it is possible to try to reconnect
   * to it using the name that was originally used.  This is ordinarily the case.
   *
   * Returns false if reconnecting under the same name will never work in the way
   * that you would expect.  This is the case if 'vconn' represents a "fd:N" type
   * vconn; one can never connect to such a vconn more than once, because closing
   * it closes the file descriptor. */
  bool
  vconn_is_reconnectable(const struct vconn *vconn)
  {
      return vconn->reconnectable;
  }
  
  static void
  vcs_connecting(struct vconn *vconn) 
  {
      int retval = (vconn->class->connect)(vconn);
      assert(retval != EINPROGRESS);
      if (!retval) {
          vconn->state = VCS_SEND_HELLO;
      } else if (retval != EAGAIN) {
          vconn->state = VCS_DISCONNECTED;
          vconn->error = retval;
      }
  }
  
  static void
  vcs_send_hello(struct vconn *vconn,struct ofl_hello_elem_versionbitmap *map,bool is_map)
  {
      struct ofpbuf *b;
      int retval;
      make_openflow(sizeof(struct ofp_header), OFPT_HELLO, &b,map,is_map);
      retval = do_send(vconn, b);
      if (!retval) {
          ++vconn->ofps_sent.ofps_total;
          ++vconn->ofps_sent.ofps_hello;
          vconn->state = VCS_RECV_HELLO;
      } else {
          ofpbuf_delete(b);
          if (retval != EAGAIN) {
              vconn->state = VCS_DISCONNECTED;
              vconn->error = retval;
          }
      }
  }
  
  static void
  vcs_recv_hello(struct vconn *vconn)
  {
      struct ofpbuf *b;
      int retval;
  
      retval = do_recv(vconn, &b);
      if (!retval) {
          struct ofp_header *oh = b->data;
  
          if (oh->type == OFPT_HELLO) {
              if (b->size > sizeof *oh) {
                  struct ds msg = DS_EMPTY_INITIALIZER;
                  ds_put_format(&msg, "%s: extra-long hello:\n", vconn->name);
                  ds_put_hex_dump(&msg, b->data, b->size, 0, true);
                  VLOG_WARN_RL(LOG_MODULE, &rl, "%s", ds_cstr(&msg));
                  ds_destroy(&msg);
              }
  
              vconn->version = MIN(OFP_VERSION, oh->version);
              if (vconn->version < vconn->min_version) {
                  VLOG_WARN_RL(LOG_MODULE, &rl, "%s: version negotiation failed: we support "
                               "versions 0x%02x to 0x%02x inclusive but peer "
                               "supports no later than version 0x%02"PRIx8,
                               vconn->name, vconn->min_version, OFP_VERSION,
                               oh->version);
                  vconn->state = VCS_SEND_ERROR;
              } else {
                  VLOG_DBG(LOG_MODULE, "%s: negotiated OpenFlow version 0x%02x "
                           "(we support versions 0x%02x to 0x%02x inclusive, "
                           "peer no later than version 0x%02"PRIx8")",
                           vconn->name, vconn->version, vconn->min_version,
                           OFP_VERSION, oh->version);
                  vconn->state = VCS_CONNECTED;
              }
              ++vconn->ofps_rcvd.ofps_total;
              ++vconn->ofps_rcvd.ofps_hello;
              ofpbuf_delete(b);
              return;
          } else {
              struct ofl_msg_header *msg;
              char *str;
  
              if (!ofl_msg_unpack(b->data, b->size, &msg, NULL/*xid*/, &ofl_exp)) {
                  str = ofl_msg_to_string(msg, &ofl_exp);
                  ofl_msg_free(msg, &ofl_exp);
              } else {
                  struct ds string = DS_EMPTY_INITIALIZER;
                  ds_put_cstr(&string, "\n");
                  ds_put_hex_dump(&string, b->data, MIN(b->size, 1024), 0, false);
                  str = ds_cstr(&string);
              }
              VLOG_WARN_RL(LOG_MODULE, &rl, "%s: received message while expecting hello: %s",
                           vconn->name, str);
  
              free(str);
  
              retval = EPROTO;
              ofpbuf_delete(b);
          }
      }
  
      if (retval != EAGAIN) {
          vconn->state = VCS_DISCONNECTED;
          vconn->error = retval;
      }
  }
  
  static void
  vcs_send_error(struct vconn *vconn)
  {
      struct ofp_error_msg *error;
      struct ofpbuf *b;
      char s[128];
      int retval;
  
      snprintf(s, sizeof s, "We support versions 0x%02x to 0x%02x inclusive but "
               "you support no later than version 0x%02"PRIx8".",
               vconn->min_version, OFP_VERSION, vconn->version);
      error = make_openflow(sizeof *error, OFPT_ERROR, &b,NULL,false);
      error->type = htons(OFPET_HELLO_FAILED);
      error->code = htons(OFPHFC_INCOMPATIBLE);
      ofpbuf_put(b, s, strlen(s));
      update_openflow_length(b);
      retval = do_send(vconn, b);
      if (retval) {
          ++vconn->ofps_sent.ofps_total;
          ++vconn->ofps_sent.ofps_error;
          ++vconn->ofps_sent.ofps_error_type.hello_fail;
          ++vconn->ofps_sent.ofps_error_code.hf_incompat;
          ofpbuf_delete(b);
      }
      if (retval != EAGAIN) {
          vconn->state = VCS_DISCONNECTED;
          vconn->error = retval ? retval : EPROTO;
      }
  }
  
  /* Tries to complete the connection on 'vconn', which must be an active
   * vconn.  If 'vconn''s connection is complete, returns 0 if the connection
   * was successful or a positive errno value if it failed.  If the
   * connection is still in progress, returns EAGAIN. */
  int
  vconn_connect(struct vconn *vconn,struct ofl_hello_elem_versionbitmap *map,bool is_map)
  {
      enum vconn_state last_state;
  
      assert(vconn->min_version >= 0);
      do {
          last_state = vconn->state;
          switch (vconn->state) {
          case VCS_CONNECTING:
              vcs_connecting(vconn);
              break;
  
          case VCS_SEND_HELLO:
              vcs_send_hello(vconn,map,is_map);
              break;
  
          case VCS_RECV_HELLO:
              vcs_recv_hello(vconn);
              break;
  
          case VCS_CONNECTED:
              return 0;
  
          case VCS_SEND_ERROR:
              vcs_send_error(vconn);
              break;
  
          case VCS_DISCONNECTED:
              return vconn->error;
  
          default:
              NOT_REACHED();
          }
      } while (vconn->state != last_state);
  
      return EAGAIN;
  }
  
  /* Tries to receive an OpenFlow message from 'vconn', which must be an active
   * vconn.  If successful, stores the received message into '*msgp' and returns
   * 0.  The caller is responsible for destroying the message with
   * ofpbuf_delete().  On failure, returns a positive errno value and stores a
   * null pointer into '*msgp'.  On normal connection close, returns EOF.
   *
   * vconn_recv will not block waiting for a packet to arrive.  If no packets
   * have been received, it returns EAGAIN immediately. */
  int
  vconn_recv(struct vconn *vconn, struct ofpbuf **msgp)
  {
      int retval = vconn_connect(vconn,NULL,false);
      if (!retval) {
          retval = do_recv(vconn, msgp);
      }
      return retval;
  }
  
  static int
  do_recv(struct vconn *vconn, struct ofpbuf **msgp)
  {
      int retval;
  
  again:
      retval = (vconn->class->recv)(vconn, msgp);
      if (!retval) {
          struct ofp_header *oh;
  
          if (VLOG_IS_DBG_ENABLED(LOG_MODULE)) {
              struct ofl_msg_header *msg;
              char *str;
  
              if (!ofl_msg_unpack((*msgp)->data, (*msgp)->size, &msg, NULL/*xid*/, &ofl_exp)) {
                  str = ofl_msg_to_string(msg, &ofl_exp);
                  ofl_msg_free(msg, &ofl_exp);
              } else {
                  struct ds string = DS_EMPTY_INITIALIZER;
                  ds_put_cstr(&string, "\n");
                  ds_put_hex_dump(&string, (*msgp)->data, MIN((*msgp)->size, 1024), 0, false);
                  str = ds_cstr(&string);
              }
              VLOG_DBG_RL(LOG_MODULE, &rl, "%s: received: %s", vconn->name, str);
  
              free(str);
          }
  
          oh = ofpbuf_at_assert(*msgp, 0, sizeof *oh);
          if (oh->version != vconn->version
              && oh->type != OFPT_HELLO
              && oh->type != OFPT_ERROR
              && oh->type != OFPT_ECHO_REQUEST
              && oh->type != OFPT_ECHO_REPLY
              && oh->type != OFPT_EXPERIMENTER)
          {
              if (vconn->version < 0) {
                  if (oh->type == OFPT_PACKET_IN
                      || oh->type == OFPT_FLOW_REMOVED
                      || oh->type == OFPT_PORT_STATUS) {
                      /* The kernel datapath is stateless and doesn't really
                       * support version negotiation, so it can end up sending
                       * these asynchronous message before version negotiation
                       * is complete.  Just ignore them.
                       *
                       * (After we move OFPT_PORT_STATUS messages from the kernel
                       * into secchan, we won't get those here, since secchan
                       * does proper version negotiation.) */
                      ofpbuf_delete(*msgp);
                      goto again;
                  }
                  VLOG_ERR_RL(LOG_MODULE, &rl, "%s: received OpenFlow message type %"PRIu8" "
                              "before version negotiation complete",
                              vconn->name, oh->type);
              } else {
                  VLOG_ERR_RL(LOG_MODULE, &rl, "%s: received OpenFlow version 0x%02"PRIx8" "
                              "!= expected %02x",
                              vconn->name, oh->version, vconn->version);
              }
              ofpbuf_delete(*msgp);
              retval = EPROTO;
          }
      }
      if (retval) {
          *msgp = NULL;
      }
      return retval;
  }
  
  /* Tries to queue 'msg' for transmission on 'vconn', which must be an active
   * vconn.  If successful, returns 0, in which case ownership of 'msg' is
   * transferred to the vconn.  Success does not guarantee that 'msg' has been or
   * ever will be delivered to the peer, only that it has been queued for
   * transmission.
   *
   * Returns a positive errno value on failure, in which case the caller
   * retains ownership of 'msg'.
   *
   * vconn_send will not block.  If 'msg' cannot be immediately accepted for
   * transmission, it returns EAGAIN immediately. */
  int
  vconn_send(struct vconn *vconn, struct ofpbuf *msg,struct ofl_hello_elem_versionbitmap *map,bool is_map)
  {
      int retval = vconn_connect(vconn,map,is_map);
      if (!retval) {
          retval = do_send(vconn, msg);
      }
      return retval;
  }
  
  static int
  do_send(struct vconn *vconn, struct ofpbuf *buf)
  {
      int retval;
  
      assert(buf->size >= sizeof(struct ofp_header));
  //    assert(((struct ofp_header *) buf->data)->length == htons(buf->size));
      if (!VLOG_IS_DBG_ENABLED(LOG_MODULE)) {
          retval = (vconn->class->send)(vconn, buf);
      } else {
          struct ofl_msg_header *msg;
          char *str;
  
          if (!ofl_msg_unpack(buf->data, buf->size, &msg, NULL/*xid*/, &ofl_exp)) {
              str = ofl_msg_to_string(msg, &ofl_exp);
              ofl_msg_free(msg, &ofl_exp);
          } else {
              struct ds string = DS_EMPTY_INITIALIZER;
              ds_put_cstr(&string, "\n");
              ds_put_hex_dump(&string, buf->data, MIN(buf->size, 1024), 0, false);
              str = ds_cstr(&string);
          }
  
          retval = (vconn->class->send)(vconn, buf);
          if (retval != EAGAIN) {
              VLOG_DBG_RL(LOG_MODULE, &rl, "%s: sent (%s): %s",
                          vconn->name, strerror(retval), str);
          }
  
          free(str);
      }
      return retval;
  }
  
  /* Same as vconn_send, except that it waits until 'msg' can be transmitted. */
  int
  vconn_send_block(struct vconn *vconn, struct ofpbuf *msg , struct ofl_hello_elem_versionbitmap *map ,bool is_map)
  {
      int retval;
      while ((retval = vconn_send(vconn, msg,map,is_map)) == EAGAIN) {
          vconn_send_wait(vconn);
          poll_block();
      }
      return retval;
  }
  
  /* Same as vconn_recv, except that it waits until a message is received. */
  int
  vconn_recv_block(struct vconn *vconn, struct ofpbuf **msgp)
  {
      int retval;
      while ((retval = vconn_recv(vconn, msgp)) == EAGAIN) {
          vconn_recv_wait(vconn);
          poll_block();
      }
      return retval;
  }
  
  /* Waits until a message with a transaction ID matching 'xid' is recived on
   * 'vconn'.  Returns 0 if successful, in which case the reply is stored in
   * '*replyp' for the caller to examine and free.  Otherwise returns a positive
   * errno value, or EOF, and sets '*replyp' to null.
   *
   * 'request' is always destroyed, regardless of the return value. */
  int
  vconn_recv_xid(struct vconn *vconn, uint32_t xid, struct ofpbuf **replyp)
  {
      for (;;) {
          uint32_t recv_xid;
          uint16_t reply_flag;
          uint8_t type;
          struct ofpbuf *reply;
          int error;
  
          error = vconn_recv_block(vconn, &reply);
          if (error) {
              *replyp = NULL;
              return error;
          }
          /* Multipart messages 
             TODO: It's only getting the last message.
             Should return an array of multiparted
             messages*/
          type = ((struct ofp_header*) reply->data)->type;
          if (type == OFPT_MULTIPART_REPLY || type == OFPT_MULTIPART_REQUEST){
              reply_flag = ((struct ofp_multipart_reply *) reply->data)->flags;
              
              while(ntohs(reply_flag) == OFPMPF_REPLY_MORE){
                 error = vconn_recv_block(vconn, &reply);
                 reply_flag = ((struct ofp_multipart_reply *) reply->data)->flags;
              }
          }    
          recv_xid = ((struct ofp_header *) reply->data)->xid;
          if (xid == recv_xid) {
              *replyp = reply;
              return 0;
          }
  
          VLOG_DBG_RL(LOG_MODULE, &rl, "%s: received reply with xid %08"PRIx32" != expected "
                      "%08"PRIx32, vconn->name, recv_xid, xid);
          ofpbuf_delete(reply);
      }
  }
  
  /* Sends 'request' to 'vconn' and blocks until it receives a reply with a
   * matching transaction ID.  Returns 0 if successful, in which case the reply
   * is stored in '*replyp' for the caller to examine and free.  Otherwise
   * returns a positive errno value, or EOF, and sets '*replyp' to null.
   *
   * 'request' is always destroyed, regardless of the return value. */
  int
  vconn_transact(struct vconn *vconn, struct ofpbuf *request,
                 struct ofpbuf **replyp ,struct ofl_hello_elem_versionbitmap *map,bool is_map)
  {
      uint32_t send_xid = ((struct ofp_header *) request->data)->xid;
      int error;
  
      *replyp = NULL;
      error = vconn_send_block(vconn, request ,map,is_map);
      if (error) {
          ofpbuf_delete(request);
      }
      return error ? error : vconn_recv_xid(vconn, send_xid, replyp);
  }
  
  void
  vconn_wait(struct vconn *vconn, enum vconn_wait_type wait)
  {
      assert(wait == WAIT_CONNECT || wait == WAIT_RECV || wait == WAIT_SEND);
  
      switch (vconn->state) {
      case VCS_CONNECTING:
          wait = WAIT_CONNECT;
          break;
  
      case VCS_SEND_HELLO:
      case VCS_SEND_ERROR:
          wait = WAIT_SEND;
          break;
  
      case VCS_RECV_HELLO:
          wait = WAIT_RECV;
          break;
  
      case VCS_CONNECTED:
          break;
  
      case VCS_DISCONNECTED:
          poll_immediate_wake();
          return;
      }
      (vconn->class->wait)(vconn, wait);
  }
  
  void
  vconn_connect_wait(struct vconn *vconn)
  {
      vconn_wait(vconn, WAIT_CONNECT);
  }
  
  void
  vconn_recv_wait(struct vconn *vconn)
  {
      vconn_wait(vconn, WAIT_RECV);
  }
  
  void
  vconn_send_wait(struct vconn *vconn)
  {
      vconn_wait(vconn, WAIT_SEND);
  }
  
  /* Attempts to start listening for OpenFlow connections.  'name' is a
   * connection name in the form "TYPE:ARGS", where TYPE is an passive vconn
   * class's name and ARGS are vconn class-specific.
   *
   * Returns 0 if successful, otherwise a positive errno value.  If successful,
   * stores a pointer to the new connection in '*pvconnp', otherwise a null
   * pointer.  */
  int
  pvconn_open(const char *name, struct pvconn **pvconnp)
  {
      size_t prefix_len;
      size_t i;
  
      check_vconn_classes();
  
      *pvconnp = NULL;
      prefix_len = strcspn(name, ":");
      if (prefix_len == strlen(name)) {
          return EAFNOSUPPORT;
      }
      for (i = 0; i < ARRAY_SIZE(pvconn_classes); i++) {
          struct pvconn_class *class = pvconn_classes[i];
          if (strlen(class->name) == prefix_len
              && !memcmp(class->name, name, prefix_len)) {
              char *suffix_copy = xstrdup(name + prefix_len + 1);
              int retval = class->listen(name, suffix_copy, pvconnp);
              free(suffix_copy);
              if (retval) {
                  *pvconnp = NULL;
              }
              return retval;
          }
      }
      return EAFNOSUPPORT;
  }
  
  /* Closes 'pvconn'. */
  void
  pvconn_close(struct pvconn *pvconn)
  {
      if (pvconn != NULL) {
          char *name = pvconn->name;
          (pvconn->class->close)(pvconn);
          free(name);
      }
  }
  
  /* Tries to accept a new connection on 'pvconn'.  If successful, stores the new
   * connection in '*new_vconn' and returns 0.  Otherwise, returns a positive
   * errno value.
   *
   * The new vconn will automatically negotiate an OpenFlow protocol version
   * acceptable to both peers on the connection.  The version negotiated will be
   * no lower than 'min_version' and no higher than OFP_VERSION.
   *
   * pvconn_accept() will not block waiting for a connection.  If no connection
   * is ready to be accepted, it returns EAGAIN immediately. */
  int
  pvconn_accept(struct pvconn *pvconn, int min_version, struct vconn **new_vconn)
  {
      int retval = (pvconn->class->accept)(pvconn, new_vconn);
      if (retval) {
          *new_vconn = NULL;
      } else {
          assert((*new_vconn)->state != VCS_CONNECTING
                 || (*new_vconn)->class->connect);
          (*new_vconn)->min_version = min_version;
      }
      return retval;
  }
  
  void
  pvconn_wait(struct pvconn *pvconn)
  {
      (pvconn->class->wait)(pvconn);
  }
  
  void
  vconn_init(struct vconn *vconn, struct vconn_class *class, int connect_status,
             uint32_t ip, const char *name, bool reconnectable)
  {
      vconn->class = class;
      vconn->state = (connect_status == EAGAIN ? VCS_CONNECTING
                      : !connect_status ? VCS_SEND_HELLO
                      : VCS_DISCONNECTED);
      vconn->error = connect_status;
      vconn->version = -1;
      vconn->min_version = -1;
      vconn->ip = ip;
      vconn->name = xstrdup(name);
      vconn->reconnectable = reconnectable;
      memset(&vconn->ofps_rcvd, 0, sizeof(vconn->ofps_rcvd));
      memset(&vconn->ofps_sent, 0, sizeof(vconn->ofps_sent));
  }
  
  void
  pvconn_init(struct pvconn *pvconn, struct pvconn_class *class,
              const char *name)
  {
      pvconn->class = class;
      pvconn->name = xstrdup(name);
  }
  