multi.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2013, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

#include "curl_setup.h"

#include <curl/curl.h>

#include "urldata.h"
#include "transfer.h"
#include "url.h"
#include "connect.h"
#include "progress.h"
#include "easyif.h"
#include "multiif.h"
#include "sendf.h"
#include "timeval.h"
#include "http.h"
#include "select.h"
#include "warnless.h"
#include "speedcheck.h"
#include "conncache.h"
#include "bundles.h"
#include "multihandle.h"
#include "pipeline.h"

#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>

#include "curl_memory.h"
/* The last #include file should be: */
#include "memdebug.h"

/*
  CURL_SOCKET_HASH_TABLE_SIZE should be a prime number. Increasing it from 97
  to 911 takes on a 32-bit machine 4 x 804 = 3211 more bytes.  Still, every
  CURL handle takes 45-50 K memory, therefore this 3K are not significant.
*/
#ifndef CURL_SOCKET_HASH_TABLE_SIZE
#define CURL_SOCKET_HASH_TABLE_SIZE 911
#endif

#define CURL_CONNECTION_HASH_SIZE 97

#define CURL_MULTI_HANDLE 0x000bab1e

#define GOOD_MULTI_HANDLE(x) \
  ((x) && (((struct Curl_multi *)(x))->type == CURL_MULTI_HANDLE))
#define GOOD_EASY_HANDLE(x) \
  ((x) && (((struct SessionHandle *)(x))->magic == CURLEASY_MAGIC_NUMBER))

static void singlesocket(struct Curl_multi *multi,
                         struct SessionHandle *data);
static int update_timer(struct Curl_multi *multi);

static bool isHandleAtHead(struct SessionHandle *handle,
                           struct curl_llist *pipeline);
static CURLMcode add_next_timeout(struct timeval now,
                                  struct Curl_multi *multi,
                                  struct SessionHandle *d);
static CURLMcode multi_timeout(struct Curl_multi *multi,
                               long *timeout_ms);

#ifdef DEBUGBUILD
static const char * const statename[]={
  "INIT",
  "CONNECT_PEND",
  "CONNECT",
  "WAITRESOLVE",
  "WAITCONNECT",
  "WAITPROXYCONNECT",
  "PROTOCONNECT",
  "WAITDO",
  "DO",
  "DOING",
  "DO_MORE",
  "DO_DONE",
  "WAITPERFORM",
  "PERFORM",
  "TOOFAST",
  "DONE",
  "COMPLETED",
  "MSGSENT",
};
#endif

static void multi_freetimeout(void *a, void *b);

/* always use this function to change state, to make debugging easier */
static void mstate(struct SessionHandle *data, CURLMstate state
#ifdef DEBUGBUILD
                   , int lineno
#endif
)
{
#ifdef DEBUGBUILD
  long connection_id = -5000;
#endif
  CURLMstate oldstate = data->mstate;

  if(oldstate == state)
    /* don't bother when the new state is the same as the old state */
    return;

  data->mstate = state;

#ifdef DEBUGBUILD
  if(data->mstate >= CURLM_STATE_CONNECT_PEND &&
     data->mstate < CURLM_STATE_COMPLETED) {
    if(data->easy_conn)
      connection_id = data->easy_conn->connection_id;

    infof(data,
          "STATE: %s => %s handle %p; line %d (connection #%ld) \n",
          statename[oldstate], statename[data->mstate],
          (void *)data, lineno, connection_id);
  }
#endif
  if(state == CURLM_STATE_COMPLETED)
    /* changing to COMPLETED means there's one less easy handle 'alive' */
    data->multi->num_alive--;
}

#ifndef DEBUGBUILD
#define multistate(x,y) mstate(x,y)
#else
#define multistate(x,y) mstate(x,y, __LINE__)
#endif

/*
 * We add one of these structs to the sockhash for a particular socket
 */

struct Curl_sh_entry {
  struct SessionHandle *easy;
  time_t timestamp;
  int action;  /* what action READ/WRITE this socket waits for */
  curl_socket_t socket; /* mainly to ease debugging */
  void *socketp; /* settable by users with curl_multi_assign() */
};
/* bits for 'action' having no bits means this socket is not expecting any
   action */
#define SH_READ  1
#define SH_WRITE 2

/* make sure this socket is present in the hash for this handle */
static struct Curl_sh_entry *sh_addentry(struct curl_hash *sh,
                                         curl_socket_t s,
                                         struct SessionHandle *data)
{
  struct Curl_sh_entry *there =
    Curl_hash_pick(sh, (char *)&s, sizeof(curl_socket_t));
  struct Curl_sh_entry *check;

  if(there)
    /* it is present, return fine */
    return there;

  /* not present, add it */
  check = calloc(1, sizeof(struct Curl_sh_entry));
  if(!check)
    return NULL; /* major failure */
  check->easy = data;
  check->socket = s;

  /* make/add new hash entry */
  if(NULL == Curl_hash_add(sh, (char *)&s, sizeof(curl_socket_t), check)) {
    free(check);
    return NULL; /* major failure */
  }

  return check; /* things are good in sockhash land */
}


/* delete the given socket + handle from the hash */
static void sh_delentry(struct curl_hash *sh, curl_socket_t s)
{
  struct Curl_sh_entry *there =
    Curl_hash_pick(sh, (char *)&s, sizeof(curl_socket_t));

  if(there) {
    /* this socket is in the hash */
    /* We remove the hash entry. (This'll end up in a call to
       sh_freeentry().) */
    Curl_hash_delete(sh, (char *)&s, sizeof(curl_socket_t));
  }
}

/*
 * free a sockhash entry
 */
static void sh_freeentry(void *freethis)
{
  struct Curl_sh_entry *p = (struct Curl_sh_entry *) freethis;

  if(p)
    free(p);
}

static size_t fd_key_compare(void *k1, size_t k1_len, void *k2, size_t k2_len)
{
  (void) k1_len; (void) k2_len;

  return (*((int *) k1)) == (*((int *) k2));
}

static size_t hash_fd(void *key, size_t key_length, size_t slots_num)
{
  int fd = *((int *) key);
  (void) key_length;

  return (fd % (int)slots_num);
}

/*
 * sh_init() creates a new socket hash and returns the handle for it.
 *
 * Quote from README.multi_socket:
 *
 * "Some tests at 7000 and 9000 connections showed that the socket hash lookup
 * is somewhat of a bottle neck. Its current implementation may be a bit too
 * limiting. It simply has a fixed-size array, and on each entry in the array
 * it has a linked list with entries. So the hash only checks which list to
 * scan through. The code I had used so for used a list with merely 7 slots
 * (as that is what the DNS hash uses) but with 7000 connections that would
 * make an average of 1000 nodes in each list to run through. I upped that to
 * 97 slots (I believe a prime is suitable) and noticed a significant speed
 * increase.  I need to reconsider the hash implementation or use a rather
 * large default value like this. At 9000 connections I was still below 10us
 * per call."
 *
 */
static struct curl_hash *sh_init(int hashsize)
{
  return Curl_hash_alloc(hashsize, hash_fd, fd_key_compare,
                         sh_freeentry);
}

/*
 * multi_addmsg()
 *
 * Called when a transfer is completed. Adds the given msg pointer to
 * the list kept in the multi handle.
 */
static CURLMcode multi_addmsg(struct Curl_multi *multi,
                              struct Curl_message *msg)
{
  if(!Curl_llist_insert_next(multi->msglist, multi->msglist->tail, msg))
    return CURLM_OUT_OF_MEMORY;

  return CURLM_OK;
}

/*
 * multi_freeamsg()
 *
 * Callback used by the llist system when a single list entry is destroyed.
 */
static void multi_freeamsg(void *a, void *b)
{
  (void)a;
  (void)b;
}

struct Curl_multi *Curl_multi_handle(int hashsize, /* socket hash */
                                     int chashsize) /* connection hash */
{
  struct Curl_multi *multi = calloc(1, sizeof(struct Curl_multi));

  if(!multi)
    return NULL;

  multi->type = CURL_MULTI_HANDLE;

  multi->hostcache = Curl_mk_dnscache();
  if(!multi->hostcache)
    goto error;

  multi->sockhash = sh_init(hashsize);
  if(!multi->sockhash)
    goto error;

  multi->conn_cache = Curl_conncache_init(chashsize);
  if(!multi->conn_cache)
    goto error;

  multi->msglist = Curl_llist_alloc(multi_freeamsg);
  if(!multi->msglist)
    goto error;

  /* allocate a new easy handle to use when closing cached connections */
  multi->closure_handle = curl_easy_init();
  if(!multi->closure_handle)
    goto error;

  multi->closure_handle->multi = multi;
  multi->closure_handle->state.conn_cache = multi->conn_cache;

  multi->max_pipeline_length = 5;
  return (CURLM *) multi;

  error:

  Curl_hash_destroy(multi->sockhash);
  multi->sockhash = NULL;
  Curl_hash_destroy(multi->hostcache);
  multi->hostcache = NULL;
  Curl_conncache_destroy(multi->conn_cache);
  multi->conn_cache = NULL;
  Curl_close(multi->closure_handle);
  multi->closure_handle = NULL;

  free(multi);
  return NULL;
}

CURLM *curl_multi_init(void)
{
  return Curl_multi_handle(CURL_SOCKET_HASH_TABLE_SIZE,
                           CURL_CONNECTION_HASH_SIZE);
}

CURLMcode curl_multi_add_handle(CURLM *multi_handle,
                                CURL *easy_handle)
{
  struct curl_llist *timeoutlist;
  struct Curl_multi *multi = (struct Curl_multi *)multi_handle;
  struct SessionHandle *data = (struct SessionHandle *)easy_handle;

  /* First, make some basic checks that the CURLM handle is a good handle */
  if(!GOOD_MULTI_HANDLE(multi))
    return CURLM_BAD_HANDLE;

  /* Verify that we got a somewhat good easy handle too */
  if(!GOOD_EASY_HANDLE(easy_handle))
    return CURLM_BAD_EASY_HANDLE;

  /* Prevent users from adding same easy handle more than once and prevent
     adding to more than one multi stack */
  if(data->multi)
    return CURLM_ADDED_ALREADY;

  /* Allocate and initialize timeout list for easy handle */
  timeoutlist = Curl_llist_alloc(multi_freetimeout);
  if(!timeoutlist)
    return CURLM_OUT_OF_MEMORY;

  /*
   * No failure allowed in this function beyond this point. And no
   * modification of easy nor multi handle allowed before this except for
   * potential multi's connection cache growing which won't be undone in this
   * function no matter what.
   */

  /* Make easy handle use timeout list initialized above */
  data->state.timeoutlist = timeoutlist;
  timeoutlist = NULL;

  /* set the easy handle */
  multistate(data, CURLM_STATE_INIT);

  if((data->set.global_dns_cache) &&
     (data->dns.hostcachetype != HCACHE_GLOBAL)) {
    /* global dns cache was requested but still isn't */
    struct curl_hash *global = Curl_global_host_cache_init();
    if(global) {
      /* only do this if the global cache init works */
      data->dns.hostcache = global;
      data->dns.hostcachetype = HCACHE_GLOBAL;
    }
  }
  /* for multi interface connections, we share DNS cache automatically if the
     easy handle's one is currently not set. */
  else if(!data->dns.hostcache ||
     (data->dns.hostcachetype == HCACHE_NONE)) {
    data->dns.hostcache = multi->hostcache;
    data->dns.hostcachetype = HCACHE_MULTI;
  }

  /* Point to the multi's connection cache */
  data->state.conn_cache = multi->conn_cache;

  /* This adds the new entry at the 'end' of the doubly-linked circular
     list of SessionHandle structs to try and maintain a FIFO queue so
     the pipelined requests are in order. */

  /* We add this new entry last in the list. */

  data->next = NULL; /* end of the line */
  if(multi->easyp) {
    struct SessionHandle *last = multi->easylp;
    last->next = data;
    data->prev = last;
    multi->easylp = data; /* the new last node */
  }
  else {
    /* first node, make both prev and next be NULL! */
    data->next = NULL;
    data->prev = NULL;
    multi->easylp = multi->easyp = data; /* both first and last */
  }

  /* make the SessionHandle refer back to this multi handle */
  data->multi = multi_handle;

  /* Set the timeout for this handle to expire really soon so that it will
     be taken care of even when this handle is added in the midst of operation
     when only the curl_multi_socket() API is used. During that flow, only
     sockets that time-out or have actions will be dealt with. Since this
     handle has no action yet, we make sure it times out to get things to
     happen. */
  Curl_expire(data, 1);

  /* increase the node-counter */
  multi->num_easy++;

  /* increase the alive-counter */
  multi->num_alive++;

  /* A somewhat crude work-around for a little glitch in update_timer() that
     happens if the lastcall time is set to the same time when the handle is
     removed as when the next handle is added, as then the check in
     update_timer() that prevents calling the application multiple times with
     the same timer infor will not trigger and then the new handle's timeout
     will not be notified to the app.

     The work-around is thus simply to clear the 'lastcall' variable to force
     update_timer() to always trigger a callback to the app when a new easy
     handle is added */
  memset(&multi->timer_lastcall, 0, sizeof(multi->timer_lastcall));

  update_timer(multi);
  return CURLM_OK;
}

#if 0
/* Debug-function, used like this:
 *
 * Curl_hash_print(multi->sockhash, debug_print_sock_hash);
 *
 * Enable the hash print function first by editing hash.c
 */
static void debug_print_sock_hash(void *p)
{
  struct Curl_sh_entry *sh = (struct Curl_sh_entry *)p;

  fprintf(stderr, " [easy %p/magic %x/socket %d]",
          (void *)sh->data, sh->data->magic, (int)sh->socket);
}
#endif

CURLMcode curl_multi_remove_handle(CURLM *multi_handle,
                                   CURL *curl_handle)
{
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;
  struct SessionHandle *easy = curl_handle;
  struct SessionHandle *data = easy;

  /* First, make some basic checks that the CURLM handle is a good handle */
  if(!GOOD_MULTI_HANDLE(multi))
    return CURLM_BAD_HANDLE;

  /* Verify that we got a somewhat good easy handle too */
  if(!GOOD_EASY_HANDLE(curl_handle))
    return CURLM_BAD_EASY_HANDLE;

  /* Prevent users from trying to remove same easy handle more than once */
  if(!data->multi)
    return CURLM_OK; /* it is already removed so let's say it is fine! */

  if(easy) {
    bool premature = (data->mstate < CURLM_STATE_COMPLETED) ? TRUE : FALSE;
    bool easy_owns_conn = (data->easy_conn &&
                           (data->easy_conn->data == easy)) ?
                           TRUE : FALSE;

    /* If the 'state' is not INIT or COMPLETED, we might need to do something
       nice to put the easy_handle in a good known state when this returns. */
    if(premature)
      /* this handle is "alive" so we need to count down the total number of
         alive connections when this is removed */
      multi->num_alive--;

    if(data->easy_conn &&
       (data->easy_conn->send_pipe->size +
        data->easy_conn->recv_pipe->size > 1) &&
       data->mstate > CURLM_STATE_WAITDO &&
       data->mstate < CURLM_STATE_COMPLETED) {
      /* If the handle is in a pipeline and has started sending off its
         request but not received its response yet, we need to close
         connection. */
      data->easy_conn->bits.close = TRUE;
      /* Set connection owner so that Curl_done() closes it.
         We can sefely do this here since connection is killed. */
      data->easy_conn->data = easy;
    }

    /* The timer must be shut down before data->multi is set to NULL,
       else the timenode will remain in the splay tree after
       curl_easy_cleanup is called. */
    Curl_expire(data, 0);

    /* destroy the timeout list that is held in the easy handle */
    if(data->state.timeoutlist) {
      Curl_llist_destroy(data->state.timeoutlist, NULL);
      data->state.timeoutlist = NULL;
    }

    if(data->dns.hostcachetype == HCACHE_MULTI) {
      /* stop using the multi handle's DNS cache */
      data->dns.hostcache = NULL;
      data->dns.hostcachetype = HCACHE_NONE;
    }

    if(data->easy_conn) {

      /* we must call Curl_done() here (if we still "own it") so that we don't
         leave a half-baked one around */
      if(easy_owns_conn) {

        /* Curl_done() clears the conn->data field to lose the association
           between the easy handle and the connection

           Note that this ignores the return code simply because there's
           nothing really useful to do with it anyway! */
        (void)Curl_done(&data->easy_conn, data->result, premature);
      }
      else
        /* Clear connection pipelines, if Curl_done above was not called */
        Curl_getoff_all_pipelines(data, data->easy_conn);
    }

    /* as this was using a shared connection cache we clear the pointer
       to that since we're not part of that multi handle anymore */
      data->state.conn_cache = NULL;

    /* change state without using multistate(), only to make singlesocket() do
       what we want */
    data->mstate = CURLM_STATE_COMPLETED;
    singlesocket(multi, easy); /* to let the application know what sockets
                                  that vanish with this handle */

    /* Remove the association between the connection and the handle */
    if(data->easy_conn) {
      data->easy_conn->data = NULL;
      data->easy_conn = NULL;
    }

    data->multi = NULL; /* clear the association to this multi handle */

    {
      /* make sure there's no pending message in the queue sent from this easy
         handle */
      struct curl_llist_element *e;

      for(e = multi->msglist->head; e; e = e->next) {
        struct Curl_message *msg = e->ptr;

        if(msg->extmsg.easy_handle == easy) {
          Curl_llist_remove(multi->msglist, e, NULL);
          /* there can only be one from this specific handle */
          break;
        }
      }
    }

    /* make the previous node point to our next */
    if(data->prev)
      data->prev->next = data->next;
    else
      multi->easyp = data->next; /* point to first node */

    /* make our next point to our previous node */
    if(data->next)
      data->next->prev = data->prev;
    else
      multi->easylp = data->prev; /* point to last node */

    /* NOTE NOTE NOTE
       We do not touch the easy handle here! */

    multi->num_easy--; /* one less to care about now */

    update_timer(multi);
    return CURLM_OK;
  }
  else
    return CURLM_BAD_EASY_HANDLE; /* twasn't found */
}

bool Curl_multi_pipeline_enabled(const struct Curl_multi *multi)
{
  return (multi && multi->pipelining_enabled) ? TRUE : FALSE;
}

void Curl_multi_handlePipeBreak(struct SessionHandle *data)
{
  data->easy_conn = NULL;
}

static int waitconnect_getsock(struct connectdata *conn,
                               curl_socket_t *sock,
                               int numsocks)
{
  int i;
  int s=0;
  int rc=0;

  if(!numsocks)
    return GETSOCK_BLANK;

  for(i=0; i<2; i++) {
    if(conn->tempsock[i] != CURL_SOCKET_BAD) {
      sock[s] = conn->tempsock[i];
      rc |= GETSOCK_WRITESOCK(s++);
    }
  }

  /* when we've sent a CONNECT to a proxy, we should rather wait for the
     socket to become readable to be able to get the response headers */
  if(conn->tunnel_state[FIRSTSOCKET] == TUNNEL_CONNECT) {
    sock[0] = conn->sock[FIRSTSOCKET];
    return GETSOCK_READSOCK(0);
  }

  return rc;
}

static int domore_getsock(struct connectdata *conn,
                          curl_socket_t *socks,
                          int numsocks)
{
  if(conn && conn->handler->domore_getsock)
    return conn->handler->domore_getsock(conn, socks, numsocks);
  return GETSOCK_BLANK;
}

/* returns bitmapped flags for this handle and its sockets */
static int multi_getsock(struct SessionHandle *data,
                         curl_socket_t *socks, /* points to numsocks number
                                                  of sockets */
                         int numsocks)
{
  /* If the pipe broke, or if there's no connection left for this easy handle,
     then we MUST bail out now with no bitmask set. The no connection case can
     happen when this is called from curl_multi_remove_handle() =>
     singlesocket() => multi_getsock().
  */
  if(data->state.pipe_broke || !data->easy_conn)
    return 0;

  if(data->mstate > CURLM_STATE_CONNECT &&
     data->mstate < CURLM_STATE_COMPLETED) {
    /* Set up ownership correctly */
    data->easy_conn->data = data;
  }

  switch(data->mstate) {
  default:
#if 0 /* switch back on these cases to get the compiler to check for all enums
         to be present */
  case CURLM_STATE_TOOFAST:  /* returns 0, so will not select. */
  case CURLM_STATE_COMPLETED:
  case CURLM_STATE_MSGSENT:
  case CURLM_STATE_INIT:
  case CURLM_STATE_CONNECT:
  case CURLM_STATE_WAITDO:
  case CURLM_STATE_DONE:
  case CURLM_STATE_LAST:
    /* this will get called with CURLM_STATE_COMPLETED when a handle is
       removed */
#endif
    return 0;

  case CURLM_STATE_WAITRESOLVE:
    return Curl_resolver_getsock(data->easy_conn, socks, numsocks);

  case CURLM_STATE_PROTOCONNECT:
    return Curl_protocol_getsock(data->easy_conn, socks, numsocks);

  case CURLM_STATE_DO:
  case CURLM_STATE_DOING:
    return Curl_doing_getsock(data->easy_conn, socks, numsocks);

  case CURLM_STATE_WAITPROXYCONNECT:
  case CURLM_STATE_WAITCONNECT:
    return waitconnect_getsock(data->easy_conn, socks, numsocks);

  case CURLM_STATE_DO_MORE:
    return domore_getsock(data->easy_conn, socks, numsocks);

  case CURLM_STATE_DO_DONE: /* since is set after DO is completed, we switch
                               to waiting for the same as the *PERFORM
                               states */
  case CURLM_STATE_PERFORM:
  case CURLM_STATE_WAITPERFORM:
    return Curl_single_getsock(data->easy_conn, socks, numsocks);
  }

}

CURLMcode curl_multi_fdset(CURLM *multi_handle,
                           fd_set *read_fd_set, fd_set *write_fd_set,
                           fd_set *exc_fd_set, int *max_fd)
{
  /* Scan through all the easy handles to get the file descriptors set.
     Some easy handles may not have connected to the remote host yet,
     and then we must make sure that is done. */
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;
  struct SessionHandle *data;
  int this_max_fd=-1;
  curl_socket_t sockbunch[MAX_SOCKSPEREASYHANDLE];
  int bitmap;
  int i;
  (void)exc_fd_set; /* not used */

  if(!GOOD_MULTI_HANDLE(multi))
    return CURLM_BAD_HANDLE;

  data=multi->easyp;
  while(data) {
    bitmap = multi_getsock(data, sockbunch, MAX_SOCKSPEREASYHANDLE);

    for(i=0; i< MAX_SOCKSPEREASYHANDLE; i++) {
      curl_socket_t s = CURL_SOCKET_BAD;

      if((bitmap & GETSOCK_READSOCK(i)) && VALID_SOCK((sockbunch[i]))) {
        FD_SET(sockbunch[i], read_fd_set);
        s = sockbunch[i];
      }
      if((bitmap & GETSOCK_WRITESOCK(i)) && VALID_SOCK((sockbunch[i]))) {
        FD_SET(sockbunch[i], write_fd_set);
        s = sockbunch[i];
      }
      if(s == CURL_SOCKET_BAD)
        /* this socket is unused, break out of loop */
        break;
      else {
        if((int)s > this_max_fd)
          this_max_fd = (int)s;
      }
    }

    data = data->next; /* check next handle */
  }

  *max_fd = this_max_fd;

  return CURLM_OK;
}

CURLMcode curl_multi_wait(CURLM *multi_handle,
                          struct curl_waitfd extra_fds[],
                          unsigned int extra_nfds,
                          int timeout_ms,
                          int *ret)
{
  struct Curl_multi *multi=(struct Curl_multi *)multi_handle;
  struct SessionHandle *data;
  curl_socket_t sockbunch[MAX_SOCKSPEREASYHANDLE];
  int bitmap;
  unsigned int i;
  unsigned int nfds = 0;
  unsigned int curlfds;
  struct pollfd *ufds = NULL;
  long timeout_internal;

  if(!GOOD_MULTI_HANDLE(multi))
    return CURLM_BAD_HANDLE;

  /* If the internally desired timeout is actually shorter than requested from
     the outside, then use the shorter time! But only if the internal timer
     is actually larger than -1! */
  (void)multi_timeout(multi, &timeout_internal);
  if((timeout_internal >= 0) && (timeout_internal < (long)timeout_ms))
    timeout_ms = (int)timeout_internal;

  /* Count up how many fds we have from the multi handle */
  data=multi->easyp;
  while(data) {
    bitmap = multi_getsock(data, sockbunch, MAX_SOCKSPEREASYHANDLE);

    for(i=0; i< MAX_SOCKSPEREASYHANDLE; i++) {
      curl_socket_t s = CURL_SOCKET_BAD;

      if(bitmap & GETSOCK_READSOCK(i)) {
        ++nfds;
        s = sockbunch[i];
      }
      if(bitmap & GETSOCK_WRITESOCK(i)) {
        ++nfds;
        s = sockbunch[i];
      }
      if(s == CURL_SOCKET_BAD) {
        break;
      }
    }

    data = data->next; /* check next handle */
  }

  curlfds = nfds; /* number of internal file descriptors */
  nfds += extra_nfds; /* add the externally provided ones */

  if(nfds) {
    ufds = malloc(nfds * sizeof(struct pollfd));
    if(!ufds)
      return CURLM_OUT_OF_MEMORY;
  }
  nfds = 0;

  /* only do the second loop if we found descriptors in the first stage run
     above */

  if(curlfds) {
    /* Add the curl handles to our pollfds first */
    data=multi->easyp;
    while(data) {
      bitmap = multi_getsock(data, sockbunch, MAX_SOCKSPEREASYHANDLE);

      for(i=0; i< MAX_SOCKSPEREASYHANDLE; i++) {
        curl_socket_t s = CURL_SOCKET_BAD;

        if(bitmap & GETSOCK_READSOCK(i)) {
          ufds[nfds].fd = sockbunch[i];
          ufds[nfds].events = POLLIN;
          ++nfds;
          s = sockbunch[i];
        }
        if(bitmap & GETSOCK_WRITESOCK(i)) {
          ufds[nfds].fd = sockbunch[i];
          ufds[nfds].events = POLLOUT;
          ++nfds;
          s = sockbunch[i];
        }
        if(s == CURL_SOCKET_BAD) {
          break;
        }
      }

      data = data->next; /* check next handle */
    }
  }

  /* Add external file descriptions from poll-like struct curl_waitfd */
  for(i = 0; i < extra_nfds; i++) {
    ufds[nfds].fd = extra_fds[i].fd;
    ufds[nfds].events = 0;
    if(extra_fds[i].events & CURL_WAIT_POLLIN)
      ufds[nfds].events |= POLLIN;
    if(extra_fds[i].events & CURL_WAIT_POLLPRI)
      ufds[nfds].events |= POLLPRI;
    if(extra_fds[i].events & CURL_WAIT_POLLOUT)
      ufds[nfds].events |= POLLOUT;
    ++nfds;
  }

  if(nfds) {
    /* wait... */
    infof(data, "Curl_poll(%d ds, %d ms)\n", nfds, timeout_ms);
    i = Curl_poll(ufds, nfds, timeout_ms);

    if(i) {
      unsigned int j;
      /* copy revents results from the poll to the curl_multi_wait poll
         struct, the bit values of the actual underlying poll() implementation
         may not be the same as the ones in the public libcurl API! */
      for(j = 0; j < extra_nfds; j++) {
        unsigned short mask = 0;
        unsigned r = ufds[curlfds + j].revents;

        if(r & POLLIN)
          mask |= CURL_WAIT_POLLIN;
        if(r & POLLOUT)
          mask |= CURL_WAIT_POLLOUT;
        if(r & POLLPRI)
          mask |= CURL_WAIT_POLLPRI;

        extra_fds[j].revents = mask;
      }
    }
  }
  else
    i = 0;

  Curl_safefree(ufds);
  if(ret)
    *ret = i;
  return CURLM_OK;
}

static CURLMcode multi_runsingle(struct Curl_multi *multi,
                                 struct timeval now,
                                 struct SessionHandle *data)
{
  struct Curl_message *msg = NULL;
  bool connected;
  bool async;
  bool protocol_connect = FALSE;
  bool dophase_done = FALSE;
  bool done = FALSE;
  CURLMcode result = CURLM_OK;
  struct SingleRequest *k;
  long timeout_ms;
  int control;

  if(!GOOD_EASY_HANDLE(data))
    return CURLM_BAD_EASY_HANDLE;

  do {
    /* this is a single-iteration do-while loop just to allow a
       break to skip to the end of it */
    bool disconnect_conn = FALSE;

    /* Handle the case when the pipe breaks, i.e., the connection
       we're using gets cleaned up and we're left with nothing. */
    if(data->state.pipe_broke) {
      infof(data, "Pipe broke: handle 0x%p, url = %s\n",
            (void *)data, data->state.path);

      if(data->mstate < CURLM_STATE_COMPLETED) {
        /* Head back to the CONNECT state */
        multistate(data, CURLM_STATE_CONNECT);
        result = CURLM_CALL_MULTI_PERFORM;
        data->result = CURLE_OK;
      }

      data->state.pipe_broke = FALSE;
      data->easy_conn = NULL;
      break;
    }

    if(!data->easy_conn &&
       data->mstate > CURLM_STATE_CONNECT &&
       data->mstate < CURLM_STATE_DONE) {
      /* In all these states, the code will blindly access 'data->easy_conn'
         so this is precaution that it isn't NULL. And it silences static
         analyzers. */
      failf(data, "In state %d with no easy_conn, bail out!\n", data->mstate);
      return CURLM_INTERNAL_ERROR;
    }

    if(data->easy_conn && data->mstate > CURLM_STATE_CONNECT &&
       data->mstate < CURLM_STATE_COMPLETED)
      /* Make sure we set the connection's current owner */
      data->easy_conn->data = data;

    if(data->easy_conn &&
       (data->mstate >= CURLM_STATE_CONNECT) &&
       (data->mstate < CURLM_STATE_COMPLETED)) {
      /* we need to wait for the connect state as only then is the start time
         stored, but we must not check already completed handles */

      timeout_ms = Curl_timeleft(data, &now,
                                 (data->mstate <= CURLM_STATE_WAITDO)?
                                 TRUE:FALSE);

      if(timeout_ms < 0) {
        /* Handle timed out */
        if(data->mstate == CURLM_STATE_WAITRESOLVE)
          failf(data, "Resolving timed out after %ld milliseconds",
                Curl_tvdiff(now, data->progress.t_startsingle));
        else if(data->mstate == CURLM_STATE_WAITCONNECT)
          failf(data, "Connection timed out after %ld milliseconds",
                Curl_tvdiff(now, data->progress.t_startsingle));
        else {
          k = &data->req;
          failf(data, "Operation timed out after %ld milliseconds with %"
                FORMAT_OFF_T " out of %" FORMAT_OFF_T " bytes received",
                Curl_tvdiff(now, data->progress.t_startsingle), k->bytecount,
                k->size);
        }

        /* Force the connection closed because the server could continue to
           send us stuff at any time. (The disconnect_conn logic used below
           doesn't work at this point). */
        data->easy_conn->bits.close = TRUE;
        data->result = CURLE_OPERATION_TIMEDOUT;
        multistate(data, CURLM_STATE_COMPLETED);
        break;
      }