url.c

    break;
  case CURLOPT_INFILESIZE_LARGE:
    /*
     * If known, this should inform curl about the file size of the
     * to-be-uploaded file.
     */
    data->set.infilesize = va_arg(param, curl_off_t);
    break;
  case CURLOPT_LOW_SPEED_LIMIT:
    /*
     * The low speed limit that if transfers are below this for
     * CURLOPT_LOW_SPEED_TIME, the transfer is aborted.
     */
    data->set.low_speed_limit=va_arg(param, long);
    break;
  case CURLOPT_LOW_SPEED_TIME:
    /*
     * The low speed time that if transfers are below the set
     * CURLOPT_LOW_SPEED_LIMIT during this time, the transfer is aborted.
     */
    data->set.low_speed_time=va_arg(param, long);
    break;
  case CURLOPT_URL:
    /*
     * The URL to fetch.
     */
    if(data->change.url_alloc) {
      /* the already set URL is allocated, free it first! */
      free(data->change.url);
      data->change.url_alloc=FALSE;
    }
    data->set.set_url = va_arg(param, char *);
    data->change.url = data->set.set_url;
    data->change.url_changed = TRUE;
    break;
  case CURLOPT_PORT:
    /*
     * The port number to use when getting the URL
     */
    data->set.use_port = va_arg(param, long);
    break;
  case CURLOPT_TIMEOUT:
    /*
     * The maximum time you allow curl to use for a single transfer
     * operation.
     */
    data->set.timeout = va_arg(param, long);
    break;
  case CURLOPT_CONNECTTIMEOUT:
    /*
     * The maximum time you allow curl to use to connect.
     */
    data->set.connecttimeout = va_arg(param, long);
    break;

  case CURLOPT_USERPWD:
    /*
     * user:password to use in the operation
     */
    data->set.userpwd = va_arg(param, char *);
    break;
  case CURLOPT_POSTQUOTE:
    /*
     * List of RAW FTP commands to use after a transfer
     */
    data->set.postquote = va_arg(param, struct curl_slist *);
    break;
  case CURLOPT_PREQUOTE:
    /*
     * List of RAW FTP commands to use prior to RETR (Wesley Laxton)
     */
    data->set.prequote = va_arg(param, struct curl_slist *);
    break;
  case CURLOPT_QUOTE:
    /*
     * List of RAW FTP commands to use before a transfer
     */
    data->set.quote = va_arg(param, struct curl_slist *);
    break;
  case CURLOPT_PROGRESSFUNCTION:
    /*
     * Progress callback function
     */
    data->set.fprogress = va_arg(param, curl_progress_callback);
    if(data->set.fprogress)
      data->progress.callback = TRUE; /* no longer internal */
    else
      data->progress.callback = FALSE; /* NULL enforces internal */

    break;
  case CURLOPT_PROGRESSDATA:
    /*
     * Custom client data to pass to the progress callback
     */
    data->set.progress_client = va_arg(param, void *);
    break;
  case CURLOPT_PROXYUSERPWD:
    /*
     * user:password needed to use the proxy
     */
    data->set.proxyuserpwd = va_arg(param, char *);
    break;
  case CURLOPT_RANGE:
    /*
     * What range of the file you want to transfer
     */
    data->set.set_range = va_arg(param, char *);
    break;
  case CURLOPT_RESUME_FROM:
    /*
     * Resume transfer at the give file position
     */
    data->set.set_resume_from = va_arg(param, long);
    break;
  case CURLOPT_RESUME_FROM_LARGE:
    /*
     * Resume transfer at the give file position
     */
    data->set.set_resume_from = va_arg(param, curl_off_t);
    break;
  case CURLOPT_DEBUGFUNCTION:
    /*
     * stderr write callback.
     */
    data->set.fdebug = va_arg(param, curl_debug_callback);
    /*
     * if the callback provided is NULL, it'll use the default callback
     */
    break;
  case CURLOPT_DEBUGDATA:
    /*
     * Set to a void * that should receive all error writes. This
     * defaults to CURLOPT_STDERR for normal operations.
     */
    data->set.debugdata = va_arg(param, void *);
    break;
  case CURLOPT_STDERR:
    /*
     * Set to a FILE * that should receive all error writes. This
     * defaults to stderr for normal operations.
     */
    data->set.err = va_arg(param, FILE *);
    if(!data->set.err)
      data->set.err = stderr;
    break;
  case CURLOPT_HEADERFUNCTION:
    /*
     * Set header write callback
     */
    data->set.fwrite_header = va_arg(param, curl_write_callback);
    break;
  case CURLOPT_WRITEFUNCTION:
    /*
     * Set data write callback
     */
    data->set.fwrite = va_arg(param, curl_write_callback);
    if(!data->set.fwrite)
      /* When set to NULL, reset to our internal default function */
      data->set.fwrite = (curl_write_callback)fwrite;
    break;
  case CURLOPT_READFUNCTION:
    /*
     * Read data callback
     */
    data->set.fread = va_arg(param, curl_read_callback);
    if(!data->set.fread)
      /* When set to NULL, reset to our internal default function */
      data->set.fread = (curl_read_callback)fread;
    break;
  case CURLOPT_IOCTLFUNCTION:
    /*
     * I/O control callback. Might be NULL.
     */
    data->set.ioctl = va_arg(param, curl_ioctl_callback);
    break;
  case CURLOPT_IOCTLDATA:
    /*
     * I/O control data pointer. Might be NULL.
     */
    data->set.ioctl_client = va_arg(param, void *);
    break;
  case CURLOPT_SSLCERT:
    /*
     * String that holds file name of the SSL certificate to use
     */
    data->set.cert = va_arg(param, char *);
    break;
  case CURLOPT_SSLCERTTYPE:
    /*
     * String that holds file type of the SSL certificate to use
     */
    data->set.cert_type = va_arg(param, char *);
    break;
  case CURLOPT_SSLKEY:
    /*
     * String that holds file name of the SSL certificate to use
     */
    data->set.key = va_arg(param, char *);
    break;
  case CURLOPT_SSLKEYTYPE:
    /*
     * String that holds file type of the SSL certificate to use
     */
    data->set.key_type = va_arg(param, char *);
    break;
  case CURLOPT_SSLKEYPASSWD:
    /*
     * String that holds the SSL private key password.
     */
    data->set.key_passwd = va_arg(param, char *);
    break;
  case CURLOPT_SSLENGINE:
    /*
     * String that holds the SSL crypto engine.
     */
    argptr = va_arg(param, char *);
    if (argptr && argptr[0])
       result = Curl_ssl_set_engine(data, argptr);
    break;

  case CURLOPT_SSLENGINE_DEFAULT:
    /*
     * flag to set engine as default.
     */
    result = Curl_ssl_set_engine_default(data);
    break;
  case CURLOPT_CRLF:
    /*
     * Kludgy option to enable CRLF conversions. Subject for removal.
     */
    data->set.crlf = va_arg(param, long)?TRUE:FALSE;
    break;

  case CURLOPT_INTERFACE:
    /*
     * Set what interface or address/hostname to bind the socket to when
     * performing an operation and thus what from-IP your connection will use.
     */
    data->set.device = va_arg(param, char *);
    break;
  case CURLOPT_LOCALPORT:
    /*
     * Set what local port to bind the socket to when performing an operation.
     */
    data->set.localport = (unsigned short) va_arg(param, long);
    break;
  case CURLOPT_LOCALPORTRANGE:
    /*
     * Set number of local ports to try, starting with CURLOPT_LOCALPORT.
     */
    data->set.localportrange = (int) va_arg(param, long);
    break;
  case CURLOPT_KRB4LEVEL:
    /*
     * A string that defines the krb4 security level.
     */
    data->set.krb4_level = va_arg(param, char *);
    data->set.krb4=data->set.krb4_level?TRUE:FALSE;
    break;
  case CURLOPT_SSL_VERIFYPEER:
    /*
     * Enable peer SSL verifying.
     */
    data->set.ssl.verifypeer = va_arg(param, long);
    break;
  case CURLOPT_SSL_VERIFYHOST:
    /*
     * Enable verification of the CN contained in the peer certificate
     */
    data->set.ssl.verifyhost = va_arg(param, long);
    break;
  case CURLOPT_SSL_CTX_FUNCTION:
    /*
     * Set a SSL_CTX callback
     */
    data->set.ssl.fsslctx = va_arg(param, curl_ssl_ctx_callback);
    break;
  case CURLOPT_SSL_CTX_DATA:
    /*
     * Set a SSL_CTX callback parameter pointer
     */
    data->set.ssl.fsslctxp = va_arg(param, void *);
    break;
  case CURLOPT_CAINFO:
    /*
     * Set CA info for SSL connection. Specify file name of the CA certificate
     */
    data->set.ssl.CAfile = va_arg(param, char *);
    break;
  case CURLOPT_CAPATH:
    /*
     * Set CA path info for SSL connection. Specify directory name of the CA
     * certificates which have been prepared using openssl c_rehash utility.
     */
    /* This does not work on windows. */
    data->set.ssl.CApath = va_arg(param, char *);
    break;
  case CURLOPT_TELNETOPTIONS:
    /*
     * Set a linked list of telnet options
     */
    data->set.telnet_options = va_arg(param, struct curl_slist *);
    break;

  case CURLOPT_BUFFERSIZE:
    /*
     * The application kindly asks for a differently sized receive buffer.
     * If it seems reasonable, we'll use it.
     */
    data->set.buffer_size = va_arg(param, long);

    if((data->set.buffer_size> (BUFSIZE -1 )) ||
       (data->set.buffer_size < 1))
      data->set.buffer_size = 0; /* huge internal default */

    break;

  case CURLOPT_NOSIGNAL:
    /*
     * The application asks not to set any signal() or alarm() handlers,
     * even when using a timeout.
     */
    data->set.no_signal = va_arg(param, long) ? TRUE : FALSE;
    break;

  case CURLOPT_SHARE:
    {
      struct Curl_share *set;
      set = va_arg(param, struct Curl_share *);

      /* disconnect from old share, if any */
      if(data->share) {
        Curl_share_lock(data, CURL_LOCK_DATA_SHARE, CURL_LOCK_ACCESS_SINGLE);

        if(data->share->hostcache == data->hostcache)
          data->hostcache = NULL;

        if(data->share->cookies == data->cookies)
          data->cookies = NULL;

        data->share->dirty--;

        Curl_share_unlock(data, CURL_LOCK_DATA_SHARE);
        data->share = NULL;
      }

      /* use new share if it set */
      data->share = set;
      if(data->share) {

        Curl_share_lock(data, CURL_LOCK_DATA_SHARE, CURL_LOCK_ACCESS_SINGLE);

        data->share->dirty++;

        if(data->share->hostcache) {
          /* use shared host cache, first free own one if any */
          if(data->hostcache)
            Curl_hash_destroy(data->hostcache);

          data->hostcache = data->share->hostcache;
        }
#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_COOKIES)
        if(data->share->cookies) {
          /* use shared cookie list, first free own one if any */
          if (data->cookies)
            Curl_cookie_cleanup(data->cookies);
          data->cookies = data->share->cookies;
        }
#endif   /* CURL_DISABLE_HTTP */
        Curl_share_unlock(data, CURL_LOCK_DATA_SHARE);

      }
#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_COOKIES)
      /* check cookie list is set */
      if(!data->cookies)
        data->cookies = Curl_cookie_init(data, NULL, NULL, TRUE );
#endif   /* CURL_DISABLE_HTTP */
      /* check for host cache not needed,
       * it will be done by curl_easy_perform */
    }
    break;

  case CURLOPT_PROXYTYPE:
    /*
     * Set proxy type. HTTP/SOCKS4/SOCKS5
     */
    data->set.proxytype = (curl_proxytype)va_arg(param, long);
    break;

  case CURLOPT_PRIVATE:
    /*
     * Set private data pointer.
     */
    data->set.private_data = va_arg(param, char *);
    break;

  case CURLOPT_MAXFILESIZE:
    /*
     * Set the maximum size of a file to download.
     */
    data->set.max_filesize = va_arg(param, long);
    break;

  case CURLOPT_FTP_SSL:
    /*
     * Make FTP transfers attempt to use SSL/TLS.
     */
    data->set.ftp_ssl = (curl_ftpssl)va_arg(param, long);
    break;

  case CURLOPT_FTPSSLAUTH:
    /*
     * Set a specific auth for FTP-SSL transfers.
     */
    data->set.ftpsslauth = (curl_ftpauth)va_arg(param, long);
    break;

  case CURLOPT_IPRESOLVE:
    data->set.ip_version = va_arg(param, long);
    break;

  case CURLOPT_MAXFILESIZE_LARGE:
    /*
     * Set the maximum size of a file to download.
     */
    data->set.max_filesize = va_arg(param, curl_off_t);
    break;

  case CURLOPT_TCP_NODELAY:
    /*
     * Enable or disable TCP_NODELAY, which will disable/enable the Nagle
     * algorithm
     */
    data->set.tcp_nodelay = (bool)va_arg(param, long);
    break;

  /*********** 3rd party transfer options ***********/
  case CURLOPT_SOURCE_URL:
    /*
     * SOURCE URL
     */
    data->set.source_url = va_arg(param, char *);
    data->set.printhost = (data->set.source_url != NULL);
    break;

  case CURLOPT_SOURCE_USERPWD:
    /*
     * Use SOURCE USER[:PASSWORD]
     */
    data->set.source_userpwd = va_arg(param, char *);
    break;

  case CURLOPT_SOURCE_QUOTE:
    /*
     * List of RAW FTP commands to use after a connect
     */
    data->set.source_quote = va_arg(param, struct curl_slist *);
    break;

  case CURLOPT_SOURCE_PREQUOTE:
    /*
     * List of RAW FTP commands to use before a transfer on the source host
     */
    data->set.source_prequote = va_arg(param, struct curl_slist *);
    break;

  case CURLOPT_SOURCE_POSTQUOTE:
    /*
     * List of RAW FTP commands to use after a transfer on the source host
     */
    data->set.source_postquote = va_arg(param, struct curl_slist *);
    break;

  case CURLOPT_FTP_ACCOUNT:
    data->set.ftp_account = va_arg(param, char *);
    break;

  case CURLOPT_IGNORE_CONTENT_LENGTH:
    data->set.ignorecl = va_arg(param, long)?TRUE:FALSE;
    break;

  case CURLOPT_CONNECT_ONLY:
    /*
     * No data transfer, set up connection and let application use the socket
     */
    data->set.connect_only = va_arg(param, long)?TRUE:FALSE;
    break;

  default:
    /* unknown tag and its companion, just ignore: */
    result = CURLE_FAILED_INIT; /* correct this */
    break;
  }

  return result;
}

CURLcode Curl_disconnect(struct connectdata *conn)
{
  struct SessionHandle *data;
  if(!conn)
    return CURLE_OK; /* this is closed and fine already */

  data = conn->data;

#if defined(CURLDEBUG) && defined(AGGRESIVE_TEST)
  /* scan for DNS cache entries still marked as in use */
  Curl_hash_apply(data->hostcache,
                  NULL, Curl_scan_cache_used);
#endif

  Curl_hostcache_prune(data); /* kill old DNS cache entries */

  /*
   * The range string is usually freed in curl_done(), but we might
   * get here *instead* if we fail prematurely. Thus we need to be able
   * to free this resource here as well.
   */
  if(conn->bits.rangestringalloc) {
    free(conn->range);
    conn->bits.rangestringalloc = FALSE;
  }

  if((conn->ntlm.state != NTLMSTATE_NONE) ||
     (conn->proxyntlm.state != NTLMSTATE_NONE)) {
    /* Authentication data is a mix of connection-related and sessionhandle-
       related stuff. NTLM is connection-related so when we close the shop
       we shall forget. */
    data->state.authhost.done = FALSE;
    data->state.authhost.picked =
      data->state.authhost.want;

    data->state.authproxy.done = FALSE;
    data->state.authproxy.picked =
      data->state.authproxy.want;

    data->state.authproblem = FALSE;

    Curl_ntlm_cleanup(conn);
  }

  if(conn->curl_disconnect)
    /* This is set if protocol-specific cleanups should be made */
    conn->curl_disconnect(conn);

  if(-1 != conn->connectindex) {
    /* unlink ourselves! */
    infof(data, "Closing connection #%ld\n", conn->connectindex);
    data->state.connects[conn->connectindex] = NULL;
  }

  Curl_safefree(conn->proto.generic);
  Curl_safefree(conn->newurl);
  Curl_safefree(conn->pathbuffer); /* the URL path buffer */

  Curl_safefree(conn->host.rawalloc); /* host name buffer */
  Curl_safefree(conn->proxy.rawalloc); /* proxy name buffer */
#ifdef USE_LIBIDN
  if(conn->host.encalloc)
    idn_free(conn->host.encalloc); /* encoded host name buffer, must be freed
                                      with idn_free() since this was allocated
                                      by libidn */
  if(conn->proxy.encalloc)
    idn_free(conn->proxy.encalloc); /* encoded proxy name buffer, must be
                                       freed with idn_free() since this was
                                       allocated by libidn */
#endif
  Curl_ssl_close(conn);

  /* close possibly still open sockets */
  if(CURL_SOCKET_BAD != conn->sock[SECONDARYSOCKET])
    sclose(conn->sock[SECONDARYSOCKET]);
  if(CURL_SOCKET_BAD != conn->sock[FIRSTSOCKET])
    sclose(conn->sock[FIRSTSOCKET]);

  Curl_safefree(conn->user);
  Curl_safefree(conn->passwd);
  Curl_safefree(conn->proxyuser);
  Curl_safefree(conn->proxypasswd);
  Curl_safefree(conn->allocptr.proxyuserpwd);
  Curl_safefree(conn->allocptr.uagent);
  Curl_safefree(conn->allocptr.userpwd);
  Curl_safefree(conn->allocptr.accept_encoding);
  Curl_safefree(conn->allocptr.rangeline);
  Curl_safefree(conn->allocptr.ref);
  Curl_safefree(conn->allocptr.host);
  Curl_safefree(conn->allocptr.cookiehost);
  Curl_safefree(conn->ip_addr_str);
  Curl_safefree(conn->trailer);

  /* possible left-overs from the async name resolvers */
#if defined(USE_ARES)
  Curl_safefree(conn->async.hostname);
  Curl_safefree(conn->async.os_specific);
#elif defined(CURLRES_THREADED)
  Curl_destroy_thread_data(&conn->async);
#endif

  Curl_free_ssl_config(&conn->ssl_config);

  free(conn); /* free all the connection oriented data */

  return CURLE_OK;
}

/*
 * This function should return TRUE if the socket is to be assumed to
 * be dead. Most commonly this happens when the server has closed the
 * connection due to inactivity.
 */
static bool SocketIsDead(curl_socket_t sock)
{
  int sval;
  bool ret_val = TRUE;

  sval = Curl_select(sock, CURL_SOCKET_BAD, 0);
  if(sval == 0)
    /* timeout */
    ret_val = FALSE;

  return ret_val;
}

/*
 * Given one filled in connection struct (named needle), this function should
 * detect if there already is one that have all the significant details
 * exactly the same and thus should be used instead.
 */
static bool
ConnectionExists(struct SessionHandle *data,
                 struct connectdata *needle,
                 struct connectdata **usethis)
{
  long i;
  struct connectdata *check;

  for(i=0; i< data->state.numconnects; i++) {
    bool match = FALSE;
    /*
     * Note that if we use a HTTP proxy, we check connections to that
     * proxy and not to the actual remote server.
     */
    check = data->state.connects[i];
    if(!check)
      /* NULL pointer means not filled-in entry */
      continue;

    if((needle->protocol&PROT_SSL) != (check->protocol&PROT_SSL))
      /* don't do mixed SSL and non-SSL connections */
      continue;

    if(!needle->bits.httpproxy || needle->protocol&PROT_SSL) {
      /* The requested connection does not use a HTTP proxy or it
         uses SSL. */

      if(!(needle->protocol&PROT_SSL) && check->bits.httpproxy)
        /* we don't do SSL but the cached connection has a proxy,
           then don't match this */
        continue;

      if(strequal(needle->protostr, check->protostr) &&
         strequal(needle->host.name, check->host.name) &&
         (needle->remote_port == check->remote_port) ) {
        if(needle->protocol & PROT_SSL) {
          /* This is SSL, verify that we're using the same
             ssl options as well */
          if(!Curl_ssl_config_matches(&needle->ssl_config,
                                      &check->ssl_config)) {
            continue;
          }
        }
        if((needle->protocol & PROT_FTP) ||
           ((needle->protocol & PROT_HTTP) &&
            (needle->data->state.authhost.want==CURLAUTH_NTLM))) {
          /* This is FTP or HTTP+NTLM, verify that we're using the same name
             and password as well */
          if(!strequal(needle->user, check->user) ||
             !strequal(needle->passwd, check->passwd)) {
            /* one of them was different */
            continue;
          }
        }
        match = TRUE;
      }
    }
    else { /* The requested needle connection is using a proxy,
              is the checked one using the same? */
      if(check->bits.httpproxy &&
         strequal(needle->proxy.name, check->proxy.name) &&
         needle->port == check->port) {
        /* This is the same proxy connection, use it! */
        match = TRUE;
      }
    }

    if(match) {
      bool dead = SocketIsDead(check->sock[FIRSTSOCKET]);
      if(dead) {
        /*
         */
        infof(data, "Connection %d seems to be dead!\n", i);
        Curl_disconnect(check); /* disconnect resources */
        data->state.connects[i]=NULL; /* nothing here */

        /* There's no need to continue searching, because we only store
           one connection for each unique set of identifiers */
        return FALSE;
      }

      *usethis = check;
      return TRUE; /* yes, we found one to use! */
    }
  }
  return FALSE; /* no matching connecting exists */
}

/*
 * This function frees/closes a connection in the connection cache. This
 * should take the previously set policy into account when deciding which
 * of the connections to kill.
 */
static long
ConnectionKillOne(struct SessionHandle *data)
{
  long i;
  struct connectdata *conn;
  long highscore=-1;
  long connindex=-1;
  long score;
  struct timeval now;

  now = Curl_tvnow();

  for(i=0; i< data->state.numconnects; i++) {
    conn = data->state.connects[i];

    if(!conn)
      continue;

    /*
     * By using the set policy, we score each connection.
     */
    switch(data->set.closepolicy) {
    case CURLCLOSEPOLICY_LEAST_RECENTLY_USED:
    default:
      /*
       * Set higher score for the age passed since the connection
       * was used.
       */
      score = Curl_tvdiff(now, conn->now);
      break;
    case CURLCLOSEPOLICY_OLDEST:
      /*
       * Set higher score for the age passed since the connection
       * was created.
       */
      score = Curl_tvdiff(now, conn->created);
      break;
    }

    if(score > highscore) {
      highscore = score;
      connindex = i;
    }
  }
  if(connindex >= 0) {

    /* the winner gets the honour of being disconnected */
    (void) Curl_disconnect(data->state.connects[connindex]);

    /* clean the array entry */
    data->state.connects[connindex] = NULL;
  }

  return connindex; /* return the available index or -1 */
}

/*
 * The given input connection struct pointer is to be stored. If the "cache"
 * is already full, we must clean out the most suitable using the previously
 * set policy.
 *
 * The given connection should be unique. That must've been checked prior to
 * this call.
 */
static long
ConnectionStore(struct SessionHandle *data,
                struct connectdata *conn)
{
  long i;
  for(i=0; i< data->state.numconnects; i++) {
    if(!data->state.connects[i])
      break;
  }
  if(i == data->state.numconnects) {
    /* there was no room available, kill one */
    i = ConnectionKillOne(data);
    infof(data, "Connection (#%d) was killed to make room\n", i);
  }

  if(-1 != i) {
    /* only do this if a true index was returned, if -1 was returned there
       is no room in the cache for an unknown reason and we cannot store
       this there. */
    data->state.connects[i] = conn; /* fill in this */
    conn->connectindex = i; /* make the child know where the pointer to this
                               particular data is stored */
  }
  return i;
}

/*
* This function logs in to a SOCKS4 proxy and sends the specifics to the final
* destination server.
*
* Reference :
*   http://socks.permeo.com/protocol/socks4.protocol
*
* Note :
*   Nonsupport "SOCKS 4A (Simple Extension to SOCKS 4 Protocol)"
*   Nonsupport "Identification Protocol (RFC1413)"
*/
static int handleSock4Proxy(const char *proxy_name, struct connectdata *conn)
{
  unsigned char socksreq[262]; /* room for SOCKS4 request incl. user id */
  int result;
  CURLcode code;
  curl_socket_t sock = conn->sock[FIRSTSOCKET];
  struct SessionHandle *data = conn->data;

  Curl_nonblock(sock, FALSE);

  /*
  * Compose socks4 request
  *
  * Request format
  *
  *     +----+----+----+----+----+----+----+----+----+----+....+----+
  *     | VN | CD | DSTPORT |      DSTIP        | USERID       |NULL|
  *     +----+----+----+----+----+----+----+----+----+----+....+----+
  * # of bytes:  1    1      2              4           variable       1
  */

  socksreq[0] = 4; /* version (SOCKS4) */
  socksreq[1] = 1; /* connect */
  *((unsigned short*)&socksreq[2]) = htons(conn->remote_port);

  /* DNS resolve */
  {
    struct Curl_dns_entry *dns;
    Curl_addrinfo *hp=NULL;
    int rc;

    rc = Curl_resolv(conn, conn->host.name, (int)conn->remote_port, &dns);

    if(rc == CURLRESOLV_ERROR)
      return 1;

    if(rc == CURLRESOLV_PENDING)
      /* this requires that we're in "wait for resolve" state */
      rc = Curl_wait_for_resolv(conn, &dns);

    /*
    * We cannot use 'hostent' as a struct that Curl_resolv() returns.  It
    * returns a Curl_addrinfo pointer that may not always look the same.
    */
    if(dns)
      hp=dns->addr;
    if (hp) {
      char buf[64];
      unsigned short ip[4];
      Curl_printable_address(hp, buf, sizeof(buf));

      if(4 == sscanf( buf, "%hu.%hu.%hu.%hu",
        &ip[0], &ip[1], &ip[2], &ip[3])) {
          /* Set DSTIP */
          socksreq[4] = (unsigned char)ip[0];
          socksreq[5] = (unsigned char)ip[1];
          socksreq[6] = (unsigned char)ip[2];
          socksreq[7] = (unsigned char)ip[3];
        }
      else
        hp = NULL; /* fail! */

      Curl_resolv_unlock(conn->data, dns); /* not used anymore from now on */

    }
    if(!hp) {
      failf(conn->data, "Failed to resolve \"%s\" for SOCKS4 connect.",
        conn->host.name);
      return 1;
    }
  }

  /*
   * This is currently not supporting "Identification Protocol (RFC1413)".
   */
  socksreq[8] = 0; /* ensure empty userid is NUL-terminated */
  if (proxy_name)
    strlcat((char*)socksreq + 8, proxy_name, sizeof(socksreq) - 8);

  /*
   * Make connection
   */
  {
    ssize_t actualread;
    ssize_t written;
    int packetsize = 9 + strlen((char*)socksreq + 8); /* size including NUL */

    /* Send request */
    code = Curl_write(conn, sock, (char *)socksreq, packetsize, &written);
    if ((code != CURLE_OK) || (written != packetsize)) {
      failf(conn->data, "Failed to send SOCKS4 connect request.");
      return 1;
    }

    packetsize = 8; /* receive data size */

    /* Receive response */
    result = Curl_read(conn, sock, (char *)socksreq, packetsize, &actualread);
    if ((result != CURLE_OK) || (actualread != packetsize)) {
      failf(conn->data, "Failed to receive SOCKS4 connect request ack.");
      return 1;
    }

    /*
    * Response format
    *
    *     +----+----+----+----+----+----+----+----+
    *     | VN | CD | DSTPORT |      DSTIP        |
    *     +----+----+----+----+----+----+----+----+
    * # of bytes:  1    1      2              4
    *
    * VN is the version of the reply code and should be 0. CD is the result
    * code with one of the following values:
    *
    * 90: request granted
    * 91: request rejected or failed
    * 92: request rejected because SOCKS server cannot connect to
    *     identd on the client
    * 93: request rejected because the client program and identd
    *     report different user-ids
    */

    /* wrong version ? */
    if (socksreq[0] != 0) {
      failf(conn->data,
        "SOCKS4 reply has wrong version, version should be 4.");
      return 1;
    }

    /* Result */
    switch(socksreq[1])
    {
      case 90:
        infof(data, "SOCKS4 request granted.\n");
        break;
      case 91:
        failf(conn->data,
          "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
          ", request rejected or failed.",
          (unsigned char)socksreq[4], (unsigned char)socksreq[5],
          (unsigned char)socksreq[6], (unsigned char)socksreq[7],
          (unsigned int)ntohs(*(unsigned short*)(&socksreq[8])),
          socksreq[1]);
        return 1;
      case 92:
        failf(conn->data,
          "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
          ", request rejected because SOCKS server cannot connect to "
          "identd on the client.",
          (unsigned char)socksreq[4], (unsigned char)socksreq[5],
          (unsigned char)socksreq[6], (unsigned char)socksreq[7],
          (unsigned int)ntohs(*(unsigned short*)(&socksreq[8])),
          socksreq[1]);
        return 1;
      case 93:
        failf(conn->data,
          "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
          ", request rejected because the client program and identd "
          "report different user-ids.",
          (unsigned char)socksreq[4], (unsigned char)socksreq[5],
          (unsigned char)socksreq[6], (unsigned char)socksreq[7],
          (unsigned int)ntohs(*(unsigned short*)(&socksreq[8])),
          socksreq[1]);
        return 1;
      default :
        failf(conn->data,
          "Can't complete SOCKS4 connection to %d.%d.%d.%d:%d. (%d)"
          ", Unknown.",
          (unsigned char)socksreq[4], (unsigned char)socksreq[5],
          (unsigned char)socksreq[6], (unsigned char)socksreq[7],
          (unsigned int)ntohs(*(unsigned short*)(&socksreq[8])),
          socksreq[1]);
        return 1;
    }
  }

  Curl_nonblock(sock, TRUE);