multi.c

      /* check if we have the name resolved by now */
      easy->result = Curl_is_resolved(easy->easy_conn, &dns);

      if(dns) {
        /* Update sockets here. Mainly because the socket(s) may have been
           closed and the application thus needs to be told, even if it is
           likely that the same socket(s) will again be used further down. */
        singlesocket(multi, easy);

        /* Perform the next step in the connection phase, and then move on
           to the WAITCONNECT state */
        easy->result = Curl_async_resolved(easy->easy_conn,
                                           &protocol_connect);

        if(CURLE_OK != easy->result)
          /* if Curl_async_resolved() returns failure, the connection struct
             is already freed and gone */
          easy->easy_conn = NULL;           /* no more connection */
        else {
          /* call again please so that we get the next socket setup */
          result = CURLM_CALL_MULTI_PERFORM;
          if(protocol_connect)
            multistate(easy, multi->pipelining_enabled?
                       CURLM_STATE_WAITDO:CURLM_STATE_DO);
          else {
#ifndef CURL_DISABLE_HTTP
            if(easy->easy_conn->bits.tunnel_connecting)
              multistate(easy, CURLM_STATE_WAITPROXYCONNECT);
            else
#endif
              multistate(easy, CURLM_STATE_WAITCONNECT);
          }
        }
      }

      if(CURLE_OK != easy->result) {
        /* failure detected */
        disconnect_conn = TRUE;
        break;
      }
    }
    break;

#ifndef CURL_DISABLE_HTTP
    case CURLM_STATE_WAITPROXYCONNECT:
      /* this is HTTP-specific, but sending CONNECT to a proxy is HTTP... */
      easy->result = Curl_http_connect(easy->easy_conn, &protocol_connect);

      if(easy->easy_conn->bits.proxy_connect_closed) {
        /* reset the error buffer */
        if(easy->easy_handle->set.errorbuffer)
          easy->easy_handle->set.errorbuffer[0] = '\0';
        easy->easy_handle->state.errorbuf = FALSE;

        easy->result = CURLE_OK;
        result = CURLM_CALL_MULTI_PERFORM;
        multistate(easy, CURLM_STATE_CONNECT);
      }
      else if (CURLE_OK == easy->result) {
        if(!easy->easy_conn->bits.tunnel_connecting)
          multistate(easy, CURLM_STATE_WAITCONNECT);
      }
      break;
#endif

    case CURLM_STATE_WAITCONNECT:
      /* awaiting a completion of an asynch connect */
      easy->result = Curl_is_connected(easy->easy_conn,
                                       FIRSTSOCKET,
                                       &connected);
      if(connected) {
        /* see if we need to do any proxy magic first once we connected */
        easy->result = Curl_connected_proxy(easy->easy_conn);

        if(!easy->result)
          /* if everything is still fine we do the protocol-specific connect
             setup */
          easy->result = Curl_protocol_connect(easy->easy_conn,
                                               &protocol_connect);
      }

      if(CURLE_OK != easy->result) {
        /* failure detected */
        /* Just break, the cleaning up is handled all in one place */
        disconnect_conn = TRUE;
        break;
      }

      if(connected) {
        if(!protocol_connect) {
          /* We have a TCP connection, but 'protocol_connect' may be false
             and then we continue to 'STATE_PROTOCONNECT'. If protocol
             connect is TRUE, we move on to STATE_DO.
             BUT if we are using a proxy we must change to WAITPROXYCONNECT
          */
#ifndef CURL_DISABLE_HTTP
          if(easy->easy_conn->bits.tunnel_connecting)
            multistate(easy, CURLM_STATE_WAITPROXYCONNECT);
          else
#endif
            multistate(easy, CURLM_STATE_PROTOCONNECT);

        }
        else
          /* after the connect has completed, go WAITDO or DO */
          multistate(easy, multi->pipelining_enabled?
                     CURLM_STATE_WAITDO:CURLM_STATE_DO);

        result = CURLM_CALL_MULTI_PERFORM;
      }
      break;

    case CURLM_STATE_PROTOCONNECT:
      /* protocol-specific connect phase */
      easy->result = Curl_protocol_connecting(easy->easy_conn,
                                              &protocol_connect);
      if((easy->result == CURLE_OK) && protocol_connect) {
        /* after the connect has completed, go WAITDO or DO */
        multistate(easy, multi->pipelining_enabled?
                   CURLM_STATE_WAITDO:CURLM_STATE_DO);
        result = CURLM_CALL_MULTI_PERFORM;
      }
      else if(easy->result) {
        /* failure detected */
        Curl_posttransfer(easy->easy_handle);
        Curl_done(&easy->easy_conn, easy->result, FALSE);
        disconnect_conn = TRUE;
      }
      break;

    case CURLM_STATE_WAITDO:
      /* Wait for our turn to DO when we're pipelining requests */
#ifdef DEBUGBUILD
      infof(easy->easy_handle, "Conn %ld send pipe %zu inuse %d athead %d\n",
            easy->easy_conn->connectindex,
            easy->easy_conn->send_pipe->size,
            easy->easy_conn->writechannel_inuse?1:0,
            isHandleAtHead(easy->easy_handle,
                           easy->easy_conn->send_pipe)?1:0);
#endif
      if(!easy->easy_conn->writechannel_inuse &&
         isHandleAtHead(easy->easy_handle,
                        easy->easy_conn->send_pipe)) {
        /* Grab the channel */
        easy->easy_conn->writechannel_inuse = TRUE;
        multistate(easy, CURLM_STATE_DO);
        result = CURLM_CALL_MULTI_PERFORM;
      }
      break;

    case CURLM_STATE_DO:
      if(easy->easy_handle->set.connect_only) {
        /* keep connection open for application to use the socket */
        easy->easy_conn->bits.close = FALSE;
        multistate(easy, CURLM_STATE_DONE);
        easy->result = CURLE_OK;
        result = CURLM_OK;
      }
      else {
        /* Perform the protocol's DO action */
        easy->result = Curl_do(&easy->easy_conn,
                               &dophase_done);

        if(CURLE_OK == easy->result) {
          if(!dophase_done) {
            /* DO was not completed in one function call, we must continue
               DOING... */
            multistate(easy, CURLM_STATE_DOING);
            result = CURLM_OK;
          }

          /* after DO, go DO_DONE... or DO_MORE */
          else if(easy->easy_conn->bits.do_more) {
            /* we're supposed to do more, but we need to sit down, relax
               and wait a little while first */
            multistate(easy, CURLM_STATE_DO_MORE);
            result = CURLM_OK;
          }
          else {
            /* we're done with the DO, now DO_DONE */
            multistate(easy, CURLM_STATE_DO_DONE);
            result = CURLM_CALL_MULTI_PERFORM;
          }
        }
        else if ((CURLE_SEND_ERROR == easy->result) &&
                 easy->easy_conn->bits.reuse) {
          /*
           * In this situation, a connection that we were trying to use
           * may have unexpectedly died.  If possible, send the connection
           * back to the CONNECT phase so we can try again.
           */
          char *newurl = NULL;
          followtype follow=FOLLOW_NONE;
          CURLcode drc;
          bool retry = FALSE;

          drc = Curl_retry_request(easy->easy_conn, &newurl);
          if(drc) {
            /* a failure here pretty much implies an out of memory */
            easy->result = drc;
            disconnect_conn = TRUE;
          }
          else
            retry = (bool)(newurl?TRUE:FALSE);

          Curl_posttransfer(easy->easy_handle);
          drc = Curl_done(&easy->easy_conn, easy->result, FALSE);

          /* When set to retry the connection, we must to go back to
           * the CONNECT state */
          if(retry) {
            if ((drc == CURLE_OK) || (drc == CURLE_SEND_ERROR)) {
              follow = FOLLOW_RETRY;
              drc = Curl_follow(easy->easy_handle, newurl, follow);
              if(drc == CURLE_OK) {
                multistate(easy, CURLM_STATE_CONNECT);
                result = CURLM_CALL_MULTI_PERFORM;
                easy->result = CURLE_OK;
              }
              else {
                /* Follow failed */
                easy->result = drc;
                free(newurl);
              }
            }
            else {
              /* done didn't return OK or SEND_ERROR */
              easy->result = drc;
              free(newurl);
            }
          }
          else {
            /* Have error handler disconnect conn if we can't retry */
            disconnect_conn = TRUE;
          }
        }
        else {
          /* failure detected */
          Curl_posttransfer(easy->easy_handle);
          Curl_done(&easy->easy_conn, easy->result, FALSE);
          disconnect_conn = TRUE;
        }
      }
      break;

    case CURLM_STATE_DOING:
      /* we continue DOING until the DO phase is complete */
      easy->result = Curl_protocol_doing(easy->easy_conn,
                                         &dophase_done);
      if(CURLE_OK == easy->result) {
        if(dophase_done) {
          /* after DO, go PERFORM... or DO_MORE */
          if(easy->easy_conn->bits.do_more) {
            /* we're supposed to do more, but we need to sit down, relax
               and wait a little while first */
            multistate(easy, CURLM_STATE_DO_MORE);
            result = CURLM_OK;
          }
          else {
            /* we're done with the DO, now DO_DONE */
            multistate(easy, CURLM_STATE_DO_DONE);
            result = CURLM_CALL_MULTI_PERFORM;
          }
        } /* dophase_done */
      }
      else {
        /* failure detected */
        Curl_posttransfer(easy->easy_handle);
        Curl_done(&easy->easy_conn, easy->result, FALSE);
        disconnect_conn = TRUE;
      }
      break;

    case CURLM_STATE_DO_MORE:
      /* Ready to do more? */
      easy->result = Curl_is_connected(easy->easy_conn,
                                       SECONDARYSOCKET,
                                       &connected);
      if(connected) {
        /*
         * When we are connected, DO MORE and then go DO_DONE
         */
        easy->result = Curl_do_more(easy->easy_conn);

        /* No need to remove ourselves from the send pipeline here since that
           is done for us in Curl_done() */

        if(CURLE_OK == easy->result) {
          multistate(easy, CURLM_STATE_DO_DONE);
          result = CURLM_CALL_MULTI_PERFORM;
        }
        else {
          /* failure detected */
          Curl_posttransfer(easy->easy_handle);
          Curl_done(&easy->easy_conn, easy->result, FALSE);
          disconnect_conn = TRUE;
        }
      }
      break;

    case CURLM_STATE_DO_DONE:
      /* Move ourselves from the send to recv pipeline */
      moveHandleFromSendToRecvPipeline(easy->easy_handle, easy->easy_conn);
      /* Check if we can move pending requests to send pipe */
      checkPendPipeline(easy->easy_conn);
      multistate(easy, CURLM_STATE_WAITPERFORM);
      result = CURLM_CALL_MULTI_PERFORM;
      break;

    case CURLM_STATE_WAITPERFORM:
      /* Wait for our turn to PERFORM */
      if(!easy->easy_conn->readchannel_inuse &&
         isHandleAtHead(easy->easy_handle,
                        easy->easy_conn->recv_pipe)) {
        /* Grab the channel */
        easy->easy_conn->readchannel_inuse = TRUE;
        multistate(easy, CURLM_STATE_PERFORM);
        result = CURLM_CALL_MULTI_PERFORM;
      }
#ifdef DEBUGBUILD
      else {
        infof(easy->easy_handle, "Conn %ld recv pipe %zu inuse %d athead %d\n",
              easy->easy_conn->connectindex,
              easy->easy_conn->recv_pipe->size,
              easy->easy_conn->readchannel_inuse?1:0,
              isHandleAtHead(easy->easy_handle,
                             easy->easy_conn->recv_pipe)?1:0);
      }
#endif
      break;

    case CURLM_STATE_TOOFAST: /* limit-rate exceeded in either direction */
      /* if both rates are within spec, resume transfer */
      Curl_pgrsUpdate(easy->easy_conn);
      if( ( ( easy->easy_handle->set.max_send_speed == 0 ) ||
            ( easy->easy_handle->progress.ulspeed <
              easy->easy_handle->set.max_send_speed ) )  &&
          ( ( easy->easy_handle->set.max_recv_speed == 0 ) ||
            ( easy->easy_handle->progress.dlspeed <
              easy->easy_handle->set.max_recv_speed ) )
        )
        multistate(easy, CURLM_STATE_PERFORM);
      break;

    case CURLM_STATE_PERFORM:
      /* check if over speed */
      if( (  ( easy->easy_handle->set.max_send_speed > 0 ) &&
             ( easy->easy_handle->progress.ulspeed >
               easy->easy_handle->set.max_send_speed ) )  ||
          (  ( easy->easy_handle->set.max_recv_speed > 0 ) &&
             ( easy->easy_handle->progress.dlspeed >
               easy->easy_handle->set.max_recv_speed ) )
        ) {
        /* Transfer is over the speed limit. Change state.  TODO: Call
         * Curl_expire() with the time left until we're targeted to be below
         * the speed limit again. */
        multistate(easy, CURLM_STATE_TOOFAST );
        break;
      }

      /* read/write data if it is ready to do so */
      easy->result = Curl_readwrite(easy->easy_conn, &done);

      k = &easy->easy_handle->req;

      if(!(k->keepon & KEEP_RECV)) {
        /* We're done receiving */
        easy->easy_conn->readchannel_inuse = FALSE;
      }

      if(!(k->keepon & KEEP_SEND)) {
        /* We're done sending */
        easy->easy_conn->writechannel_inuse = FALSE;
      }

      if(easy->result)  {
        /* The transfer phase returned error, we mark the connection to get
         * closed to prevent being re-used. This is because we can't possibly
         * know if the connection is in a good shape or not now.  Unless it is
         * a protocol which uses two "channels" like FTP, as then the error
         * happened in the data connection.
         */
        if(!(easy->easy_conn->protocol & PROT_DUALCHANNEL))
          easy->easy_conn->bits.close = TRUE;

        Curl_posttransfer(easy->easy_handle);
        Curl_done(&easy->easy_conn, easy->result, FALSE);
      }
      else if(TRUE == done) {
        char *newurl = NULL;
        bool retry = FALSE;
        followtype follow=FOLLOW_NONE;

        easy->result = Curl_retry_request(easy->easy_conn, &newurl);
        if(!easy->result)
          retry = (bool)(newurl?TRUE:FALSE);

        /* call this even if the readwrite function returned error */
        Curl_posttransfer(easy->easy_handle);

        /* we're no longer receving */
        moveHandleFromRecvToDonePipeline(easy->easy_handle,
                                         easy->easy_conn);

        /* expire the new receiving pipeline head */
        if(easy->easy_conn->recv_pipe->head)
          Curl_expire(easy->easy_conn->recv_pipe->head->ptr, 1);

        /* Check if we can move pending requests to send pipe */
        checkPendPipeline(easy->easy_conn);

        /* When we follow redirects or is set to retry the connection, we must
           to go back to the CONNECT state */
        if(easy->easy_handle->req.newurl || retry) {
          if(!retry) {
            /* if the URL is a follow-location and not just a retried request
               then figure out the URL here */
            newurl = easy->easy_handle->req.newurl;
            easy->easy_handle->req.newurl = NULL;
            follow = FOLLOW_REDIR;
          }
          else
            follow = FOLLOW_RETRY;
          easy->result = Curl_done(&easy->easy_conn, CURLE_OK, FALSE);
          if(easy->result == CURLE_OK)
            easy->result = Curl_follow(easy->easy_handle, newurl, follow);
          if(CURLE_OK == easy->result) {
            multistate(easy, CURLM_STATE_CONNECT);
            result = CURLM_CALL_MULTI_PERFORM;
          }
          else if(newurl)
            /* Since we "took it", we are in charge of freeing this on
               failure */
            free(newurl);
        }
        else {
          /* after the transfer is done, go DONE */

          /* but first check to see if we got a location info even though we're
             not following redirects */
          if (easy->easy_handle->req.location) {
            newurl = easy->easy_handle->req.location;
            easy->easy_handle->req.location = NULL;
            easy->result = Curl_follow(easy->easy_handle, newurl, FOLLOW_FAKE);
            if (easy->result)
              free(newurl);
          }

          multistate(easy, CURLM_STATE_DONE);
          result = CURLM_CALL_MULTI_PERFORM;
        }
      }

      break;

    case CURLM_STATE_DONE:

      if(easy->easy_conn) {
        /* Remove ourselves from the receive and done pipelines. Handle
           should be on one of these lists, depending upon how we got here. */
        Curl_removeHandleFromPipeline(easy->easy_handle,
                                      easy->easy_conn->recv_pipe);
        Curl_removeHandleFromPipeline(easy->easy_handle,
                                      easy->easy_conn->done_pipe);
        /* Check if we can move pending requests to send pipe */
        checkPendPipeline(easy->easy_conn);

        if(easy->easy_conn->bits.stream_was_rewound) {
          /* This request read past its response boundary so we quickly let
             the other requests consume those bytes since there is no
             guarantee that the socket will become active again */
          result = CURLM_CALL_MULTI_PERFORM;
        }

        /* post-transfer command */
        easy->result = Curl_done(&easy->easy_conn, CURLE_OK, FALSE);
        /*
         * If there are other handles on the pipeline, Curl_done won't set
         * easy_conn to NULL.  In such a case, curl_multi_remove_handle() can
         * access free'd data, if the connection is free'd and the handle
         * removed before we perform the processing in CURLM_STATE_COMPLETED
         */
        if (easy->easy_conn)
          easy->easy_conn = NULL;
      }

      /* after we have DONE what we're supposed to do, go COMPLETED, and
         it doesn't matter what the Curl_done() returned! */
      multistate(easy, CURLM_STATE_COMPLETED);

      break;

    case CURLM_STATE_COMPLETED:
      /* this is a completed transfer, it is likely to still be connected */

      /* This node should be delinked from the list now and we should post
         an information message that we are complete. */

      /* Important: reset the conn pointer so that we don't point to memory
         that could be freed anytime */
      easy->easy_conn = NULL;
      break;

    default:
      return CURLM_INTERNAL_ERROR;
    }

    if(CURLM_STATE_COMPLETED != easy->state) {
      if(CURLE_OK != easy->result) {
        /*
         * If an error was returned, and we aren't in completed state now,
         * then we go to completed and consider this transfer aborted.
         */

        /* NOTE: no attempt to disconnect connections must be made
           in the case blocks above - cleanup happens only here */

        easy->easy_handle->state.pipe_broke = FALSE;

        if(easy->easy_conn) {
          /* if this has a connection, unsubscribe from the pipelines */
          easy->easy_conn->writechannel_inuse = FALSE;
          easy->easy_conn->readchannel_inuse = FALSE;
          Curl_removeHandleFromPipeline(easy->easy_handle,
                                        easy->easy_conn->send_pipe);
          Curl_removeHandleFromPipeline(easy->easy_handle,
                                        easy->easy_conn->recv_pipe);
          Curl_removeHandleFromPipeline(easy->easy_handle,
                                        easy->easy_conn->done_pipe);
          /* Check if we can move pending requests to send pipe */
          checkPendPipeline(easy->easy_conn);
        }

        if(disconnect_conn) {
          Curl_disconnect(easy->easy_conn); /* disconnect properly */

          /* This is where we make sure that the easy_conn pointer is reset.
             We don't have to do this in every case block above where a
             failure is detected */
          easy->easy_conn = NULL;
        }

        multistate(easy, CURLM_STATE_COMPLETED);
      }
    }
  } while(0);
  if((CURLM_STATE_COMPLETED == easy->state) && !easy->msg) {
    if(easy->easy_handle->dns.hostcachetype == HCACHE_MULTI) {
      /* clear out the usage of the shared DNS cache */
      easy->easy_handle->dns.hostcache = NULL;
      easy->easy_handle->dns.hostcachetype = HCACHE_NONE;
    }

    /* now add a node to the Curl_message linked list with this info */
    msg = malloc(sizeof(struct Curl_message));

    if(!msg)
      return CURLM_OUT_OF_MEMORY;

    msg->extmsg.msg = CURLMSG_DONE;
    msg->extmsg.easy_handle = easy->easy_handle;
    msg->extmsg.data.result = easy->result;
    msg->next = NULL;

    easy->msg = msg;
    easy->msg_num = 1; /* there is one unread message here */

    multi->num_msgs++; /* increase message counter */
  }

  return result;
}


CURLMcode curl_multi_perform(CURLM *multi_handle, int *running_handles)
{
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;
  struct Curl_one_easy *easy;
  CURLMcode returncode=CURLM_OK;
  struct Curl_tree *t;

  if(!GOOD_MULTI_HANDLE(multi))
    return CURLM_BAD_HANDLE;

  easy=multi->easy.next;
  while(easy != &multi->easy) {
    CURLMcode result;

    do
      result = multi_runsingle(multi, easy);
    while (CURLM_CALL_MULTI_PERFORM == result);

    if(result)
      returncode = result;

    easy = easy->next; /* operate on next handle */
  }

  /*
   * Simply remove all expired timers from the splay since handles are dealt
   * with unconditionally by this function and curl_multi_timeout() requires
   * that already passed/handled expire times are removed from the splay.
   */
  do {
    struct timeval now = Curl_tvnow();

    multi->timetree = Curl_splaygetbest(now, multi->timetree, &t);
    if(t) {
      struct SessionHandle *d = t->payload;
      struct timeval* tv = &d->state.expiretime;

      /* clear the expire times within the handles that we remove from the
         splay tree */
      tv->tv_sec = 0;
      tv->tv_usec = 0;
    }

  } while(t);

  *running_handles = multi->num_alive;

  if( CURLM_OK >= returncode )
    update_timer(multi);

  return returncode;
}

/* This is called when an easy handle is cleanup'ed that is part of a multi
   handle */
void Curl_multi_rmeasy(void *multi_handle, CURL *easy_handle)
{
  curl_multi_remove_handle(multi_handle, easy_handle);
}


CURLMcode curl_multi_cleanup(CURLM *multi_handle)
{
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;
  struct Curl_one_easy *easy;
  struct Curl_one_easy *nexteasy;
  int i;
  struct closure *cl;
  struct closure *n;

  if(GOOD_MULTI_HANDLE(multi)) {
    multi->type = 0; /* not good anymore */
    Curl_hash_destroy(multi->hostcache);
    Curl_hash_destroy(multi->sockhash);
    multi->hostcache = NULL;
    multi->sockhash = NULL;

    /* go over all connections that have close actions */
    for(i=0; i< multi->connc->num; i++) {
      if(multi->connc->connects[i] &&
         multi->connc->connects[i]->protocol & PROT_CLOSEACTION) {
        Curl_disconnect(multi->connc->connects[i]);
        multi->connc->connects[i] = NULL;
      }
    }
    /* now walk through the list of handles we kept around only to be
       able to close connections "properly" */
    cl = multi->closure;
    while(cl) {
      cl->easy_handle->state.shared_conn = NULL; /* no more shared */
      if(cl->easy_handle->state.closed)
        /* close handle only if curl_easy_cleanup() already has been called
           for this easy handle */
        Curl_close(cl->easy_handle);
      n = cl->next;
      free(cl);
      cl= n;
    }

    Curl_rm_connc(multi->connc);

    /* remove all easy handles */
    easy = multi->easy.next;
    while(easy != &multi->easy) {
      nexteasy=easy->next;
      if(easy->easy_handle->dns.hostcachetype == HCACHE_MULTI) {
        /* clear out the usage of the shared DNS cache */
        easy->easy_handle->dns.hostcache = NULL;
        easy->easy_handle->dns.hostcachetype = HCACHE_NONE;
      }

      /* Clear the pointer to the connection cache */
      easy->easy_handle->state.connc = NULL;

      Curl_easy_addmulti(easy->easy_handle, NULL); /* clear the association */

      if(easy->msg)
        free(easy->msg);
      free(easy);
      easy = nexteasy;
    }

    free(multi);

    return CURLM_OK;
  }
  else
    return CURLM_BAD_HANDLE;
}

CURLMsg *curl_multi_info_read(CURLM *multi_handle, int *msgs_in_queue)
{
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;

  *msgs_in_queue = 0; /* default to none */

  if(GOOD_MULTI_HANDLE(multi)) {
    struct Curl_one_easy *easy;

    if(!multi->num_msgs)
      return NULL; /* no messages left to return */

    easy=multi->easy.next;
    while(easy != &multi->easy) {
      if(easy->msg_num) {
        easy->msg_num--;
        break;
      }
      easy = easy->next;
    }
    if(!easy)
      return NULL; /* this means internal count confusion really */

    multi->num_msgs--;
    *msgs_in_queue = multi->num_msgs;

    return &easy->msg->extmsg;
  }
  else
    return NULL;
}

/*
 * singlesocket() checks what sockets we deal with and their "action state"
 * and if we have a different state in any of those sockets from last time we
 * call the callback accordingly.
 */
static void singlesocket(struct Curl_multi *multi,
                         struct Curl_one_easy *easy)
{
  curl_socket_t socks[MAX_SOCKSPEREASYHANDLE];
  int i;
  struct Curl_sh_entry *entry;
  curl_socket_t s;
  int num;
  unsigned int curraction;
  struct Curl_one_easy *easy_by_hash;
  bool remove_sock_from_hash;

  for(i=0; i< MAX_SOCKSPEREASYHANDLE; i++)
    socks[i] = CURL_SOCKET_BAD;

  /* Fill in the 'current' struct with the state as it is now: what sockets to
     supervise and for what actions */
  curraction = multi_getsock(easy, socks, MAX_SOCKSPEREASYHANDLE);

  /* We have 0 .. N sockets already and we get to know about the 0 .. M
     sockets we should have from now on. Detect the differences, remove no
     longer supervised ones and add new ones */

  /* walk over the sockets we got right now */
  for(i=0; (i< MAX_SOCKSPEREASYHANDLE) &&
        (curraction & (GETSOCK_READSOCK(i) | GETSOCK_WRITESOCK(i)));
      i++) {
    int action = CURL_POLL_NONE;

    s = socks[i];

    /* get it from the hash */
    entry = Curl_hash_pick(multi->sockhash, (char *)&s, sizeof(s));

    if(curraction & GETSOCK_READSOCK(i))
      action |= CURL_POLL_IN;
    if(curraction & GETSOCK_WRITESOCK(i))
      action |= CURL_POLL_OUT;

    if(entry) {
      /* yeps, already present so check if it has the same action set */
      if(entry->action == action)
        /* same, continue */
        continue;
    }
    else {
      /* this is a socket we didn't have before, add it! */
      entry = sh_addentry(multi->sockhash, s, easy->easy_handle);
      if(!entry)
        /* fatal */
        return;
    }

    multi->socket_cb(easy->easy_handle,
                     s,
                     action,
                     multi->socket_userp,
                     entry ? entry->socketp : NULL);

    entry->action = action; /* store the current action state */
  }

  num = i; /* number of sockets */

  /* when we've walked over all the sockets we should have right now, we must
     make sure to detect sockets that are removed */
  for(i=0; i< easy->numsocks; i++) {
    int j;
    s = easy->sockets[i];
    for(j=0; j<num; j++) {
      if(s == socks[j]) {
        /* this is still supervised */
        s = CURL_SOCKET_BAD;
        break;
      }
    }
    if(s != CURL_SOCKET_BAD) {

      /* this socket has been removed. Tell the app to remove it */
      remove_sock_from_hash = TRUE;

      entry = Curl_hash_pick(multi->sockhash, (char *)&s, sizeof(s));
      if(entry) {
        /* check if the socket to be removed serves a connection which has
           other easy-s in a pipeline. In this case the socket should not be
           removed. */
        struct connectdata *easy_conn;

        easy_by_hash = entry->easy->multi_pos;
        easy_conn = easy_by_hash->easy_conn;
        if(easy_conn) {
          if (easy_conn->recv_pipe && easy_conn->recv_pipe->size > 1) {
            /* the handle should not be removed from the pipe yet */
            remove_sock_from_hash = FALSE;

            /* Update the sockhash entry to instead point to the next in line
               for the recv_pipe, or the first (in case this particular easy
               isn't already) */
            if (entry->easy == easy->easy_handle) {
              if (isHandleAtHead(easy->easy_handle, easy_conn->recv_pipe))
                entry->easy = easy_conn->recv_pipe->head->next->ptr;
              else
                entry->easy = easy_conn->recv_pipe->head->ptr;
            }
          }
          if (easy_conn->send_pipe  && easy_conn->send_pipe->size > 1) {
            /* the handle should not be removed from the pipe yet */
            remove_sock_from_hash = FALSE;

            /* Update the sockhash entry to instead point to the next in line
               for the send_pipe, or the first (in case this particular easy
               isn't already) */
            if (entry->easy == easy->easy_handle) {
              if (isHandleAtHead(easy->easy_handle, easy_conn->send_pipe))
                entry->easy = easy_conn->send_pipe->head->next->ptr;
              else
                entry->easy = easy_conn->send_pipe->head->ptr;
            }
          }
          /* Don't worry about overwriting recv_pipe head with send_pipe_head,
             when action will be asked on the socket (see multi_socket()), the
             head of the correct pipe will be taken according to the
             action. */
        }
      }
      else
        /* just a precaution, this socket really SHOULD be in the hash already
           but in case it isn't, we don't have to tell the app to remove it
           either since it never got to know about it */
        remove_sock_from_hash = FALSE;

      if (remove_sock_from_hash) {
        multi->socket_cb(easy->easy_handle,
                         s,
                         CURL_POLL_REMOVE,
                         multi->socket_userp,
                         entry ? entry->socketp : NULL);
        sh_delentry(multi->sockhash, s);
      }

    }
  }

  memcpy(easy->sockets, socks, num*sizeof(curl_socket_t));
  easy->numsocks = num;
}

static CURLMcode multi_socket(struct Curl_multi *multi,
                              bool checkall,
                              curl_socket_t s,
                              int ev_bitmask,
                              int *running_handles)
{
  CURLMcode result = CURLM_OK;
  struct SessionHandle *data = NULL;
  struct Curl_tree *t;

  if(checkall) {
    struct Curl_one_easy *easyp;
    /* *perform() deals with running_handles on its own */
    result = curl_multi_perform(multi, running_handles);

    /* walk through each easy handle and do the socket state change magic
       and callbacks */
    easyp=multi->easy.next;
    while(easyp != &multi->easy) {
      singlesocket(multi, easyp);
      easyp = easyp->next;
    }

    /* or should we fall-through and do the timer-based stuff? */
    return result;
  }
  else if(s != CURL_SOCKET_TIMEOUT) {

    struct Curl_sh_entry *entry =
      Curl_hash_pick(multi->sockhash, (char *)&s, sizeof(s));

    if(!entry)
      /* Unmatched socket, we can't act on it but we ignore this fact.  In
         real-world tests it has been proved that libevent can in fact give
         the application actions even though the socket was just previously
         asked to get removed, so thus we better survive stray socket actions
         and just move on. */
      ;
    else {
      data = entry->easy;

      if(data->magic != CURLEASY_MAGIC_NUMBER)
        /* bad bad bad bad bad bad bad */
        return CURLM_INTERNAL_ERROR;

      /* If the pipeline is enabled, take the handle which is in the head of
         the pipeline. If we should write into the socket, take the send_pipe
         head.  If we should read from the socket, take the recv_pipe head. */
      if(data->set.one_easy->easy_conn) {
        if ((ev_bitmask & CURL_POLL_OUT) &&
            data->set.one_easy->easy_conn->send_pipe &&
            data->set.one_easy->easy_conn->send_pipe->head)
          data = data->set.one_easy->easy_conn->send_pipe->head->ptr;
        else if ((ev_bitmask & CURL_POLL_IN) &&
                 data->set.one_easy->easy_conn->recv_pipe &&
                 data->set.one_easy->easy_conn->recv_pipe->head)
          data = data->set.one_easy->easy_conn->recv_pipe->head->ptr;
      }

      if(data->set.one_easy->easy_conn)  /* set socket event bitmask */
        data->set.one_easy->easy_conn->cselect_bits = ev_bitmask;

      do
        result = multi_runsingle(multi, data->set.one_easy);
      while (CURLM_CALL_MULTI_PERFORM == result);

      if(data->set.one_easy->easy_conn)
        data->set.one_easy->easy_conn->cselect_bits = 0;

      if(CURLM_OK >= result)
        /* get the socket(s) and check if the state has been changed since
           last */
        singlesocket(multi, data->set.one_easy);

      /* Now we fall-through and do the timer-based stuff, since we don't want
         to force the user to have to deal with timeouts as long as at least
         one connection in fact has traffic. */

      data = NULL; /* set data to NULL again to avoid calling
                      multi_runsingle() in case there's no need to */
    }
  }

  /*
   * The loop following here will go on as long as there are expire-times left
   * to process in the splay and 'data' will be re-assigned for every expired
   * handle we deal with.
   */
  do {
    struct timeval now;

    /* the first loop lap 'data' can be NULL */
    if(data) {
      do
        result = multi_runsingle(multi, data->set.one_easy);
      while (CURLM_CALL_MULTI_PERFORM == result);

      if(CURLM_OK >= result)
        /* get the socket(s) and check if the state has been changed since
           last */
        singlesocket(multi, data->set.one_easy);
    }

    /* Check if there's one (more) expired timer to deal with! This function
       extracts a matching node if there is one */

    now = Curl_tvnow();
    now.tv_usec += 1000; /* to compensate for the truncating of 999us to 0ms,
                            we always add time here to make the comparison
                            below better */

    multi->timetree = Curl_splaygetbest(now, multi->timetree, &t);