transfer.c

    302 status code may be used instead, since most user agents react
    to a 302 response as described here for 303.
    */
  case 303: /* See Other */
    /* Disable both types of POSTs, since doing a second POST when
     * following isn't what anyone would want! */
    if(data->set.httpreq != HTTPREQ_GET) {
      data->set.httpreq = HTTPREQ_GET; /* enforce GET request */
      infof(data, "Disables POST, goes with %s\n",
            data->set.opt_no_body?"HEAD":"GET");
    }
    break;
  case 304: /* Not Modified */
    /* 304 means we did a conditional request and it was "Not modified".
     * We shouldn't get any Location: header in this response!
     */
    break;
  case 305: /* Use Proxy */
    /* (quote from RFC2616, section 10.3.6):
     * "The requested resource MUST be accessed through the proxy given
     * by the Location field. The Location field gives the URI of the
     * proxy.  The recipient is expected to repeat this single request
     * via the proxy. 305 responses MUST only be generated by origin
     * servers."
     */
    break;
  }
  Curl_pgrsTime(data, TIMER_REDIRECT);
  Curl_pgrsResetTimes(data);

  return CURLE_OK;
}

static CURLcode
Curl_connect_host(struct SessionHandle *data,
                  struct connectdata **conn)
{
  CURLcode res = CURLE_OK;
  int urlchanged = FALSE;

  do {
    bool async;
    bool protocol_done=TRUE; /* will be TRUE always since this is only used
                                within the easy interface */
    Curl_pgrsTime(data, TIMER_STARTSINGLE);
    data->change.url_changed = FALSE;
    res = Curl_connect(data, conn, &async, &protocol_done);

    if((CURLE_OK == res) && async) {
      /* Now, if async is TRUE here, we need to wait for the name
         to resolve */
      res = Curl_wait_for_resolv(*conn, NULL);
      if(CURLE_OK == res)
        /* Resolved, continue with the connection */
        res = Curl_async_resolved(*conn, &protocol_done);
      else
        /* if we can't resolve, we kill this "connection" now */
        (void)Curl_disconnect(*conn);
    }
    if(res)
      break;

    /* If a callback (or something) has altered the URL we should use within
       the Curl_connect(), we detect it here and act as if we are redirected
       to the new URL */
    urlchanged = data->change.url_changed;
    if ((CURLE_OK == res) && urlchanged) {
      res = Curl_done(conn, res);
      if(CURLE_OK == res) {
        char *gotourl = strdup(data->change.url);
        res = Curl_follow(data, gotourl, FALSE);
        if(res)
          free(gotourl);
      }
    }
  } while (urlchanged && res == CURLE_OK);

  return res;
}

/* Returns TRUE and sets '*url' if a request retry is wanted */
bool Curl_retry_request(struct connectdata *conn,
                        char **url)
{
  bool retry = FALSE;

  if((conn->keep.bytecount+conn->headerbytecount == 0) &&
     conn->bits.reuse) {
    /* We got no data and we attempted to re-use a connection. This might
       happen if the connection was left alive when we were done using it
       before, but that was closed when we wanted to read from it again. Bad
       luck. Retry the same request on a fresh connect! */
    infof(conn->data, "Connection died, retrying a fresh connect\n");
    *url = strdup(conn->data->change.url);

    conn->bits.close = TRUE; /* close this connection */
    conn->bits.retry = TRUE; /* mark this as a connection we're about
                                to retry. Marking it this way should
                                prevent i.e HTTP transfers to return
                                error just because nothing has been
                                transfered! */
    retry = TRUE;
  }

  return retry;
}

/*
 * Curl_perform() is the internal high-level function that gets called by the
 * external curl_easy_perform() function. It inits, performs and cleans up a
 * single file transfer.
 */
CURLcode Curl_perform(struct SessionHandle *data)
{
  CURLcode res;
  CURLcode res2;
  struct connectdata *conn=NULL;
  char *newurl = NULL; /* possibly a new URL to follow to! */
  bool retry = FALSE;

  data->state.used_interface = Curl_if_easy;

  res = Curl_pretransfer(data);
  if(res)
    return res;

  /*
   * It is important that there is NO 'return' from this function at any other
   * place than falling down to the end of the function! This is because we
   * have cleanup stuff that must be done before we get back, and that is only
   * performed after this do-while loop.
   */

  do {
    res = Curl_connect_host(data, &conn);   /* primary connection */

    if(res == CURLE_OK) {
      if (data->set.source_url) /* 3rd party transfer */
        res = Curl_pretransfersec(conn);
      else
        conn->sec_conn = NULL;
    }

    if(res == CURLE_OK) {
      bool do_done;
      res = Curl_do(&conn, &do_done);

      /* for non 3rd party transfer only */
      if(res == CURLE_OK && !data->set.source_url) {
        res = Transfer(conn); /* now fetch that URL please */
        if(res == CURLE_OK) {
          retry = Curl_retry_request(conn, &newurl);

          if(!retry)
            /*
             * We must duplicate the new URL here as the connection data may
             * be free()ed in the Curl_done() function.
             */
            newurl = conn->newurl?strdup(conn->newurl):NULL;
        }
        else {
          /* The transfer phase returned error, we mark the connection to get
           * closed to prevent being re-used. This is becasue we can't
           * possibly know if the connection is in a good shape or not now. */
          conn->bits.close = TRUE;

          if(CURL_SOCKET_BAD != conn->sock[SECONDARYSOCKET]) {
            /* if we failed anywhere, we must clean up the secondary socket if
               it was used */
            sclose(conn->sock[SECONDARYSOCKET]);
            conn->sock[SECONDARYSOCKET] = CURL_SOCKET_BAD;
          }
        }

        /* Always run Curl_done(), even if some of the previous calls
           failed, but return the previous (original) error code */
        res2 = Curl_done(&conn, res);

        if(CURLE_OK == res)
          res = res2;
      }
      else
        /* Curl_do() failed, clean up left-overs in the done-call */
        res2 = Curl_done(&conn, res);

      /*
       * Important: 'conn' cannot be used here, since it may have been closed
       * in 'Curl_done' or other functions.
       */

      if((res == CURLE_OK) && newurl) {
        res = Curl_follow(data, newurl, retry);
        if(CURLE_OK == res) {
          newurl = NULL;
          continue;
        }
      }
    }
    break; /* it only reaches here when this shouldn't loop */

  } while(1); /* loop if Location: */

  if(newurl)
    free(newurl);

  /* run post-transfer uncondionally, but don't clobber the return code if
     we already have an error code recorder */
  res2 = Curl_posttransfer(data);
  if(!res && res2)
    res = res2;

  return res;
}

/*
 * Curl_Transfer() is called to setup some basic properties for the upcoming
 * transfer.
 */
CURLcode
Curl_Transfer(struct connectdata *c_conn, /* connection data */
              int sockindex,       /* socket index to read from or -1 */
              curl_off_t size,     /* -1 if unknown at this point */
              bool getheader,      /* TRUE if header parsing is wanted */
              curl_off_t *bytecountp, /* return number of bytes read or NULL */
              int writesockindex,  /* socket index to write to, it may very
                                      well be the same we read from. -1
                                      disables */
              curl_off_t *writecountp /* return number of bytes written or
                                       NULL */
              )
{
  struct connectdata *conn = (struct connectdata *)c_conn;
  if(!conn)
    return CURLE_BAD_FUNCTION_ARGUMENT;

  curlassert((sockindex <= 1) && (sockindex >= -1));

  /* now copy all input parameters */
  conn->sockfd = sockindex==-1?
    CURL_SOCKET_BAD:conn->sock[sockindex];
  conn->size = size;
  conn->bits.getheader = getheader;
  conn->bytecountp = bytecountp;
  conn->writesockfd = writesockindex==-1?
    CURL_SOCKET_BAD:conn->sock[writesockindex];
  conn->writebytecountp = writecountp;

  return CURLE_OK;

}

/*
 * Curl_pretransfersec() prepares the secondary connection (used for 3rd party
 * FTP transfers).
 */
CURLcode Curl_pretransfersec(struct connectdata *conn)
{
  CURLcode status = CURLE_OK;
  struct SessionHandle *data = conn->data;
  struct connectdata *sec_conn = NULL;   /* secondary connection */
  bool backup_reuse_fresh = data->set.reuse_fresh;
  char *backup_userpwd = data->set.userpwd;

  if(data->change.url_alloc)
    free(data->change.url);

  data->change.url_alloc = FALSE;
  data->change.url = data->set.source_url;

  /* We must never actually alter 'data->set' properties, so we restore the
     backed up values afterwards! */

#if 0
  /* if both remote hosts are the same host - create new connection */
  if (strequal(conn->host.dispname, data->set.source_host))
#endif
    data->set.reuse_fresh = TRUE;

  data->set.userpwd = data->set.source_userpwd;

  /* secondary connection */
  status = Curl_connect_host(data, &sec_conn);
  if(CURLE_OK == status) {
    sec_conn->sec_conn = NULL;  /* important if re-using existing connection
                                   to prevent loop */
    sec_conn->data = data;
    conn->sec_conn = sec_conn;
  }

  data->set.reuse_fresh = backup_reuse_fresh;
  data->set.userpwd = backup_userpwd;

  return status;
}