ftp.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2006, 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.
 *
 * $Id$
 ***************************************************************************/

#include "setup.h"

#ifndef CURL_DISABLE_FTP
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <ctype.h>
#include <errno.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#if defined(WIN32) && !defined(__GNUC__) || defined(__MINGW32__)

#else /* probably some kind of unix */
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#include <sys/types.h>
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_UTSNAME_H
#include <sys/utsname.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef  VMS
#include <in.h>
#include <inet.h>
#endif
#endif

#if defined(WIN32) && defined(__GNUC__) || defined(__MINGW32__)
#include <errno.h>
#endif

#if (defined(NETWARE) && defined(__NOVELL_LIBC__))
#undef in_addr_t
#define in_addr_t unsigned long
#endif

#include <curl/curl.h>
#include "urldata.h"
#include "sendf.h"

#include "if2ip.h"
#include "hostip.h"
#include "progress.h"
#include "transfer.h"
#include "escape.h"
#include "http.h" /* for HTTP proxy tunnel stuff */
#include "ftp.h"

#ifdef HAVE_KRB4
#include "krb4.h"
#endif

#include "strtoofft.h"
#include "strequal.h"
#include "sslgen.h"
#include "connect.h"
#include "strerror.h"
#include "memory.h"
#include "inet_ntop.h"
#include "select.h"
#include "parsedate.h" /* for the week day and month names */
#include "sockaddr.h" /* required for Curl_sockaddr_storage */

#if defined(HAVE_INET_NTOA_R) && !defined(HAVE_INET_NTOA_R_DECL)
#include "inet_ntoa_r.h"
#endif

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

/* The last #include file should be: */
#ifdef CURLDEBUG
#include "memdebug.h"
#endif

#ifdef HAVE_NI_WITHSCOPEID
#define NIFLAGS NI_NUMERICHOST | NI_NUMERICSERV | NI_WITHSCOPEID
#else
#define NIFLAGS NI_NUMERICHOST | NI_NUMERICSERV
#endif

/* Local API functions */
static CURLcode ftp_sendquote(struct connectdata *conn,
                              struct curl_slist *quote);
static CURLcode ftp_cwd(struct connectdata *conn, char *path);
static CURLcode ftp_mkd(struct connectdata *conn, char *path);
static CURLcode ftp_cwd_and_mkd(struct connectdata *conn, char *path);
static CURLcode ftp_quit(struct connectdata *conn);
static CURLcode ftp_3rdparty_pretransfer(struct connectdata *conn);
static CURLcode ftp_3rdparty_transfer(struct connectdata *conn);
static CURLcode ftp_parse_url_path(struct connectdata *conn);
static CURLcode ftp_cwd_and_create_path(struct connectdata *conn);
static CURLcode ftp_regular_transfer(struct connectdata *conn, bool *done);
static CURLcode ftp_3rdparty(struct connectdata *conn);
static void ftp_pasv_verbose(struct connectdata *conn,
                             Curl_addrinfo *ai,
                             char *newhost, /* ascii version */
                             int port);
static CURLcode ftp_state_post_rest(struct connectdata *conn);
static CURLcode ftp_state_post_cwd(struct connectdata *conn);
static CURLcode ftp_state_quote(struct connectdata *conn,
                                bool init, ftpstate instate);

/* easy-to-use macro: */
#define FTPSENDF(x,y,z) if((result = Curl_ftpsendf(x,y,z))) return result
#define NBFTPSENDF(x,y,z) if((result = Curl_nbftpsendf(x,y,z))) return result

static void freedirs(struct FTP *ftp)
{
  int i;
  if(ftp->dirs) {
    for (i=0; i < ftp->dirdepth; i++){
      if(ftp->dirs[i]) {
        free(ftp->dirs[i]);
        ftp->dirs[i]=NULL;
      }
    }
    free(ftp->dirs);
    ftp->dirs = NULL;
  }
  if(ftp->file) {
    free(ftp->file);
    ftp->file = NULL;
  }
}

/* Returns non-zero iff the given string contains CR (0x0D) or LF (0x0A), which
   are not allowed within RFC 959 <string>.
 */
static bool isBadFtpString(const char *string)
{
  return strchr(string, 0x0D) != NULL || strchr(string, 0x0A) != NULL;
}

/***********************************************************************
 *
 * AllowServerConnect()
 *
 * When we've issue the PORT command, we have told the server to connect
 * to us. This function will sit and wait here until the server has
 * connected.
 *
 */
static CURLcode AllowServerConnect(struct connectdata *conn)
{
  int timeout_ms;
  struct SessionHandle *data = conn->data;
  curl_socket_t sock = conn->sock[SECONDARYSOCKET];
  struct timeval now = Curl_tvnow();
  long timespent = Curl_tvdiff(Curl_tvnow(), now)/1000;
  long timeout = data->set.connecttimeout?data->set.connecttimeout:
    (data->set.timeout?data->set.timeout: 0);

  if(timeout) {
    timeout -= timespent;
    if(timeout<=0) {
      failf(data, "Timed out before server could connect to us");
      return CURLE_OPERATION_TIMEDOUT;
    }
  }

  /* We allow the server 60 seconds to connect to us, or a custom timeout.
     Note the typecast here. */
  timeout_ms = (timeout?(int)timeout:60) * 1000;

  switch (Curl_select(sock, CURL_SOCKET_BAD, timeout_ms)) {
  case -1: /* error */
    /* let's die here */
    failf(data, "Error while waiting for server connect");
    return CURLE_FTP_PORT_FAILED;
  case 0:  /* timeout */
    /* let's die here */
    failf(data, "Timeout while waiting for server connect");
    return CURLE_FTP_PORT_FAILED;
  default:
    /* we have received data here */
    {
      curl_socket_t s = CURL_SOCKET_BAD;
      socklen_t size = (socklen_t) sizeof(struct sockaddr_in);
      struct sockaddr_in add;

      if(0 == getsockname(sock, (struct sockaddr *) &add, &size))
        s=accept(sock, (struct sockaddr *) &add, &size);

      sclose(sock); /* close the first socket */

      if (CURL_SOCKET_BAD == s) {
        /* DIE! */
        failf(data, "Error accept()ing server connect");
        return CURLE_FTP_PORT_FAILED;
      }
      infof(data, "Connection accepted from server\n");

      conn->sock[SECONDARYSOCKET] = s;
      Curl_nonblock(s, TRUE); /* enable non-blocking */
    }
    break;
  }

  return CURLE_OK;
}

/* initialize stuff to prepare for reading a fresh new response */
static void ftp_respinit(struct connectdata *conn)
{
  struct FTP *ftp = conn->proto.ftp;
  ftp->nread_resp = 0;
  ftp->linestart_resp = conn->data->state.buffer;
}

/* macro to check for the last line in an FTP server response */
#define lastline(line) (isdigit((int)line[0]) && isdigit((int)line[1]) && \
                        isdigit((int)line[2]) && (' ' == line[3]))

static CURLcode ftp_readresp(curl_socket_t sockfd,
                             struct connectdata *conn,
                             int *ftpcode, /* return the ftp-code if done */
                             size_t *size) /* size of the response */
{
  int perline; /* count bytes per line */
  bool keepon=TRUE;
  ssize_t gotbytes;
  char *ptr;
  struct SessionHandle *data = conn->data;
  char *buf = data->state.buffer;
  CURLcode result = CURLE_OK;
  struct FTP *ftp = conn->proto.ftp;
  int code = 0;

  if (ftpcode)
    *ftpcode = 0; /* 0 for errors or not done */

  ptr=buf + ftp->nread_resp;

  perline= (int)(ptr-ftp->linestart_resp); /* number of bytes in the current
                                              line, so far */
  keepon=TRUE;

  while((ftp->nread_resp<BUFSIZE) && (keepon && !result)) {

    if(ftp->cache) {
      /* we had data in the "cache", copy that instead of doing an actual
       * read
       *
       * ftp->cache_size is cast to int here.  This should be safe,
       * because it would have been populated with something of size
       * int to begin with, even though its datatype may be larger
       * than an int.
       */
      memcpy(ptr, ftp->cache, (int)ftp->cache_size);
      gotbytes = (int)ftp->cache_size;
      free(ftp->cache);    /* free the cache */
      ftp->cache = NULL;   /* clear the pointer */
      ftp->cache_size = 0; /* zero the size just in case */
    }
    else {
      int res = Curl_read(conn, sockfd, ptr, BUFSIZE-ftp->nread_resp,
                          &gotbytes);
      if(res < 0)
        /* EWOULDBLOCK */
        return CURLE_OK; /* return */

      if(CURLE_OK != res)
        keepon = FALSE;
    }

    if(!keepon)
      ;
    else if(gotbytes <= 0) {
      keepon = FALSE;
      result = CURLE_RECV_ERROR;
      failf(data, "FTP response reading failed");
    }
    else {
      /* we got a whole chunk of data, which can be anything from one
       * byte to a set of lines and possible just a piece of the last
       * line */
      int i;

      conn->headerbytecount += gotbytes;

      ftp->nread_resp += gotbytes;
      for(i = 0; i < gotbytes; ptr++, i++) {
        perline++;
        if(*ptr=='\n') {
          /* a newline is CRLF in ftp-talk, so the CR is ignored as
             the line isn't really terminated until the LF comes */

          /* output debug output if that is requested */
          if(data->set.verbose)
            Curl_debug(data, CURLINFO_HEADER_IN,
                       ftp->linestart_resp, perline, conn);

          /*
           * We pass all response-lines to the callback function registered
           * for "headers". The response lines can be seen as a kind of
           * headers.
           */
          result = Curl_client_write(data, CLIENTWRITE_HEADER,
                                     ftp->linestart_resp, perline);
          if(result)
            return result;

          if(perline>3 && lastline(ftp->linestart_resp)) {
            /* This is the end of the last line, copy the last line to the
               start of the buffer and zero terminate, for old times sake (and
               krb4)! */
            char *meow;
            int n;
            for(meow=ftp->linestart_resp, n=0; meow<ptr; meow++, n++)
              buf[n] = *meow;
            *meow=0; /* zero terminate */
            keepon=FALSE;
            ftp->linestart_resp = ptr+1; /* advance pointer */
            i++; /* skip this before getting out */

            *size = ftp->nread_resp; /* size of the response */
            ftp->nread_resp = 0; /* restart */
            break;
          }
          perline=0; /* line starts over here */
          ftp->linestart_resp = ptr+1;
        }
      }
      if(!keepon && (i != gotbytes)) {
        /* We found the end of the response lines, but we didn't parse the
           full chunk of data we have read from the server. We therefore need
           to store the rest of the data to be checked on the next invoke as
           it may actually contain another end of response already! */
        ftp->cache_size = gotbytes - i;
        ftp->cache = (char *)malloc((int)ftp->cache_size);
        if(ftp->cache)
          memcpy(ftp->cache, ftp->linestart_resp, (int)ftp->cache_size);
        else
          return CURLE_OUT_OF_MEMORY; /**BANG**/
      }
    } /* there was data */

  } /* while there's buffer left and loop is requested */

  if(!result)
    code = atoi(buf);

#ifdef HAVE_KRB4
  /* handle the security-oriented responses 6xx ***/
  /* FIXME: some errorchecking perhaps... ***/
  switch(code) {
  case 631:
    Curl_sec_read_msg(conn, buf, prot_safe);
    break;
  case 632:
    Curl_sec_read_msg(conn, buf, prot_private);
    break;
  case 633:
    Curl_sec_read_msg(conn, buf, prot_confidential);
    break;
  default:
    /* normal ftp stuff we pass through! */
    break;
  }
#endif

  *ftpcode=code; /* return the initial number like this */


  /* store the latest code for later retrieval */
  conn->data->info.httpcode=code;

  return result;
}

/* --- parse FTP server responses --- */

/*
 * Curl_GetFTPResponse() is supposed to be invoked after each command sent to
 * a remote FTP server. This function will wait and read all lines of the
 * response and extract the relevant return code for the invoking function.
 */

CURLcode Curl_GetFTPResponse(ssize_t *nreadp, /* return number of bytes read */
                             struct connectdata *conn,
                             int *ftpcode) /* return the ftp-code */
{
  /*
   * We cannot read just one byte per read() and then go back to select() as
   * the OpenSSL read() doesn't grok that properly.
   *
   * Alas, read as much as possible, split up into lines, use the ending
   * line in a response or continue reading.  */

  curl_socket_t sockfd = conn->sock[FIRSTSOCKET];
  int perline; /* count bytes per line */
  bool keepon=TRUE;
  ssize_t gotbytes;
  char *ptr;
  long timeout;              /* timeout in seconds */
  int interval_ms;
  struct SessionHandle *data = conn->data;
  char *line_start;
  int code=0; /* default ftp "error code" to return */
  char *buf = data->state.buffer;
  CURLcode result = CURLE_OK;
  struct FTP *ftp = conn->proto.ftp;
  struct timeval now = Curl_tvnow();

  if (ftpcode)
    *ftpcode = 0; /* 0 for errors */

  ptr=buf;
  line_start = buf;

  *nreadp=0;
  perline=0;
  keepon=TRUE;

  while((*nreadp<BUFSIZE) && (keepon && !result)) {
    /* check and reset timeout value every lap */
    if(data->set.ftp_response_timeout )
      /* if CURLOPT_FTP_RESPONSE_TIMEOUT is set, use that to determine
         remaining time.  Also, use "now" as opposed to "conn->now"
         because ftp_response_timeout is only supposed to govern
         the response for any given ftp response, not for the time
         from connect to the given ftp response. */
      timeout = data->set.ftp_response_timeout - /* timeout time */
        Curl_tvdiff(Curl_tvnow(), now)/1000; /* spent time */
    else if(data->set.timeout)
      /* if timeout is requested, find out how much remaining time we have */
      timeout = data->set.timeout - /* timeout time */
        Curl_tvdiff(Curl_tvnow(), conn->now)/1000; /* spent time */
    else
      /* Even without a requested timeout, we only wait response_time
         seconds for the full response to arrive before we bail out */
      timeout = ftp->response_time -
        Curl_tvdiff(Curl_tvnow(), now)/1000; /* spent time */

    if(timeout <=0 ) {
      failf(data, "FTP response timeout");
      return CURLE_OPERATION_TIMEDOUT; /* already too little time */
    }

    if(!ftp->cache) {
      interval_ms = 1 * 1000;  /* use 1 second timeout intervals */

      switch (Curl_select(sockfd, CURL_SOCKET_BAD, interval_ms)) {
      case -1: /* select() error, stop reading */
        result = CURLE_RECV_ERROR;
        failf(data, "FTP response aborted due to select() error: %d", errno);
        break;
      case 0: /* timeout */
        if(Curl_pgrsUpdate(conn))
          return CURLE_ABORTED_BY_CALLBACK;
        continue; /* just continue in our loop for the timeout duration */

      default:
        break;
      }
    }
    if(CURLE_OK == result) {
      /*
       * This code previously didn't use the kerberos sec_read() code
       * to read, but when we use Curl_read() it may do so. Do confirm
       * that this is still ok and then remove this comment!
       */
      if(ftp->cache) {
        /* we had data in the "cache", copy that instead of doing an actual
         * read
         *
         * Dave Meyer, December 2003:
         * ftp->cache_size is cast to int here.  This should be safe,
         * because it would have been populated with something of size
         * int to begin with, even though its datatype may be larger
         * than an int.
         */
        memcpy(ptr, ftp->cache, (int)ftp->cache_size);
        gotbytes = (int)ftp->cache_size;
        free(ftp->cache);    /* free the cache */
        ftp->cache = NULL;   /* clear the pointer */
        ftp->cache_size = 0; /* zero the size just in case */
      }
      else {
        int res = Curl_read(conn, sockfd, ptr, BUFSIZE-*nreadp, &gotbytes);
        if(res < 0)
          /* EWOULDBLOCK */
          continue; /* go looping again */

        if(CURLE_OK != res)
          keepon = FALSE;
      }

      if(!keepon)
        ;
      else if(gotbytes <= 0) {
        keepon = FALSE;
        result = CURLE_RECV_ERROR;
        failf(data, "FTP response reading failed");
      }
      else {
        /* we got a whole chunk of data, which can be anything from one
         * byte to a set of lines and possible just a piece of the last
         * line */
        int i;

        conn->headerbytecount += gotbytes;

        *nreadp += gotbytes;
        for(i = 0; i < gotbytes; ptr++, i++) {
          perline++;
          if(*ptr=='\n') {
            /* a newline is CRLF in ftp-talk, so the CR is ignored as
               the line isn't really terminated until the LF comes */

            /* output debug output if that is requested */
            if(data->set.verbose)
              Curl_debug(data, CURLINFO_HEADER_IN, line_start, perline, conn);

            /*
             * We pass all response-lines to the callback function registered
             * for "headers". The response lines can be seen as a kind of
             * headers.
             */
            result = Curl_client_write(data, CLIENTWRITE_HEADER,
                                       line_start, perline);
            if(result)
              return result;

            if(perline>3 && lastline(line_start)) {
              /* This is the end of the last line, copy the last
               * line to the start of the buffer and zero terminate,
               * for old times sake (and krb4)! */
              char *meow;
              int n;
              for(meow=line_start, n=0; meow<ptr; meow++, n++)
                buf[n] = *meow;
              *meow=0; /* zero terminate */
              keepon=FALSE;
              line_start = ptr+1; /* advance pointer */
              i++; /* skip this before getting out */
              break;
            }
            perline=0; /* line starts over here */
            line_start = ptr+1;
          }
        }
        if(!keepon && (i != gotbytes)) {
          /* We found the end of the response lines, but we didn't parse the
             full chunk of data we have read from the server. We therefore
             need to store the rest of the data to be checked on the next
             invoke as it may actually contain another end of response
             already!  Cleverly figured out by Eric Lavigne in December
             2001. */
          ftp->cache_size = gotbytes - i;
          ftp->cache = (char *)malloc((int)ftp->cache_size);
          if(ftp->cache)
            memcpy(ftp->cache, line_start, (int)ftp->cache_size);
          else
            return CURLE_OUT_OF_MEMORY; /**BANG**/
        }
      } /* there was data */
    } /* if(no error) */
  } /* while there's buffer left and loop is requested */

  if(!result)
    code = atoi(buf);

#ifdef HAVE_KRB4
  /* handle the security-oriented responses 6xx ***/
  /* FIXME: some errorchecking perhaps... ***/
  switch(code) {
  case 631:
    Curl_sec_read_msg(conn, buf, prot_safe);
    break;
  case 632:
    Curl_sec_read_msg(conn, buf, prot_private);
    break;
  case 633:
    Curl_sec_read_msg(conn, buf, prot_confidential);
    break;
  default:
    /* normal ftp stuff we pass through! */
    break;
  }
#endif

  if(ftpcode)
    *ftpcode=code; /* return the initial number like this */

  /* store the latest code for later retrieval */
  conn->data->info.httpcode=code;

  return result;
}

/* This is the ONLY way to change FTP state! */
static void state(struct connectdata *conn,
                  ftpstate state)
{
#ifdef CURLDEBUG
  /* for debug purposes */
  const char *names[]={
    "STOP",
    "WAIT220",
    "AUTH",
    "USER",
    "PASS",
    "ACCT",
    "PBSZ",
    "PROT",
    "PWD",
    "QUOTE",
    "RETR_PREQUOTE",
    "STOR_PREQUOTE",
    "POSTQUOTE",
    "CWD",
    "MKD",
    "MDTM",
    "TYPE",
    "LIST_TYPE",
    "RETR_TYPE",
    "STOR_TYPE",
    "SIZE",
    "RETR_SIZE",
    "STOR_SIZE",
    "REST",
    "RETR_REST",
    "PORT",
    "PASV",
    "LIST",
    "RETR",
    "STOR",
    "QUIT"
  };
#endif
  struct FTP *ftp = conn->proto.ftp;
#ifdef CURLDEBUG
  if(ftp->state != state)
    infof(conn->data, "FTP %p state change from %s to %s\n",
          ftp, names[ftp->state], names[state]);
#endif
  ftp->state = state;
}

static CURLcode ftp_state_user(struct connectdata *conn)
{
  CURLcode result;
  struct FTP *ftp = conn->proto.ftp;
  /* send USER */
  NBFTPSENDF(conn, "USER %s", ftp->user?ftp->user:"");

  state(conn, FTP_USER);

  return CURLE_OK;
}

static CURLcode ftp_state_pwd(struct connectdata *conn)
{
  CURLcode result;

  /* send PWD to discover our entry point */
  NBFTPSENDF(conn, "PWD", NULL);
  state(conn, FTP_PWD);

  return CURLE_OK;
}

/* For the FTP "protocol connect" and "doing" phases only */
CURLcode Curl_ftp_fdset(struct connectdata *conn,
                        fd_set *read_fd_set,
                        fd_set *write_fd_set,
                        int *max_fdp)
{
  struct FTP *ftp = conn->proto.ftp;
  curl_socket_t sockfd = conn->sock[FIRSTSOCKET];

  if(ftp->sendleft) {
    /* write mode */
    FD_SET(sockfd, write_fd_set);
  }
  else {
    /* read mode */
    FD_SET(sockfd, read_fd_set);
  }

  if((int)sockfd > *max_fdp)
    *max_fdp = (int)sockfd;

  return CURLE_OK;
}

/* This is called after the FTP_QUOTE state is passed.

   ftp_state_cwd() sends the range of PWD commands to the server to change to
   the correct directory. It may also need to send MKD commands to create
   missing ones, if that option is enabled.
*/
static CURLcode ftp_state_cwd(struct connectdata *conn)
{
  CURLcode result = CURLE_OK;
  struct FTP *ftp = conn->proto.ftp;

  if(ftp->cwddone)
    /* already done and fine */
    result = ftp_state_post_cwd(conn);
  else {
    ftp->count2 = 0;
    if (conn->bits.reuse && ftp->entrypath) {
      /* This is a re-used connection. Since we change directory to where the
         transfer is taking place, we must first get back to the original dir
         where we ended up after login: */
      ftp->count1 = 0; /* we count this as the first path, then we add one
                          for all upcoming ones in the ftp->dirs[] array */
      NBFTPSENDF(conn, "CWD %s", ftp->entrypath);
      state(conn, FTP_CWD);
    }
    else {
      if(ftp->dirdepth) {
        ftp->count1 = 1;
        /* issue the first CWD, the rest is sent when the CWD responses are
           received... */
        NBFTPSENDF(conn, "CWD %s", ftp->dirs[ftp->count1 -1]);
        state(conn, FTP_CWD);
      }
      else {
        /* No CWD necessary */
        result = ftp_state_post_cwd(conn);
      }
    }
  }
  return result;
}

typedef enum {
  EPRT,
  PORT,
  DONE
} ftpport;

static CURLcode ftp_state_use_port(struct connectdata *conn,
                                   ftpport fcmd) /* start with this */

{
  CURLcode result = CURLE_OK;
  struct FTP *ftp = conn->proto.ftp;
  struct SessionHandle *data=conn->data;
  curl_socket_t portsock= CURL_SOCKET_BAD;
  char myhost[256] = "";

#ifdef ENABLE_IPV6
  /******************************************************************
   * IPv6-specific section
   */
  struct Curl_sockaddr_storage ss;
  struct addrinfo *res, *ai;
  socklen_t sslen;
  char hbuf[NI_MAXHOST];
  struct sockaddr *sa=(struct sockaddr *)&ss;
  char tmp[1024];
  const char *mode[] = { "EPRT", "PORT", NULL };
  int rc;
  int error;
  char *host=NULL;
  struct Curl_dns_entry *h=NULL;
  unsigned short port;

  /* Step 1, figure out what address that is requested */

  if(data->set.ftpport && (strlen(data->set.ftpport) > 1)) {
    /* attempt to get the address of the given interface name */
    if(!Curl_if2ip(data->set.ftpport, hbuf, sizeof(hbuf)))
      /* not an interface, use the given string as host name instead */
      host = data->set.ftpport;
    else
      host = hbuf; /* use the hbuf for host name */
  } /* data->set.ftpport */

  if(!host) {
    /* not an interface and not a host name, get default by extracting
       the IP from the control connection */

    sslen = sizeof(ss);
    rc = getsockname(conn->sock[FIRSTSOCKET], (struct sockaddr *)&ss, &sslen);
    if(rc < 0) {
      failf(data, "getsockname() returned %d\n", rc);
      return CURLE_FTP_PORT_FAILED;
    }

    rc = getnameinfo((struct sockaddr *)&ss, sslen, hbuf, sizeof(hbuf), NULL,
                     0, NIFLAGS);
    if(rc) {
      failf(data, "getnameinfo() returned %d\n", rc);
      return CURLE_FTP_PORT_FAILED;
    }
    host = hbuf; /* use this host name */
  }

  rc = Curl_resolv(conn, host, 0, &h);
  if(rc == CURLRESOLV_PENDING)
    rc = Curl_wait_for_resolv(conn, &h);
  if(h) {
    res = h->addr;
    /* when we return from this function, we can forget about this entry
       to we can unlock it now already */
    Curl_resolv_unlock(data, h);
  } /* (h) */
  else
    res = NULL; /* failure! */


  /* step 2, create a socket for the requested address */

  portsock = CURL_SOCKET_BAD;
  error = 0;
  for (ai = res; ai; ai = ai->ai_next) {
    /*
     * Workaround for AIX5 getaddrinfo() problem (it doesn't set ai_socktype):
     */
    if (ai->ai_socktype == 0)
      ai->ai_socktype = conn->socktype;

    portsock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    if (portsock == CURL_SOCKET_BAD) {
      error = Curl_ourerrno();
      continue;
    }
    break;
  }
  if(!ai) {
    failf(data, "socket failure: %s", Curl_strerror(conn, error));
    return CURLE_FTP_PORT_FAILED;
  }

  /* step 3, bind to a suitable local address */

  /* Try binding the given address. */
  if (bind(portsock, ai->ai_addr, ai->ai_addrlen) < 0) {

    /* It failed. Bind the address used for the control connection instead */
    sslen = sizeof(ss);

    if (getsockname(conn->sock[FIRSTSOCKET],
                    (struct sockaddr *)sa, &sslen) < 0) {
      failf(data, "getsockname() failed");
      sclose(portsock);
      return CURLE_FTP_PORT_FAILED;
    }

    /* set port number to zero to make bind() pick "any" */
    if(((struct sockaddr *)sa)->sa_family == AF_INET)
      ((struct sockaddr_in *)sa)->sin_port=0;
    else
      ((struct sockaddr_in6 *)sa)->sin6_port =0;

    if(bind(portsock, (struct sockaddr *)sa, sslen) < 0) {
      failf(data, "bind failed: %s", Curl_strerror(conn, Curl_ourerrno()));
      sclose(portsock);
      return CURLE_FTP_PORT_FAILED;
    }
  }

  /* get the name again after the bind() so that we can extract the
     port number it uses now */
  sslen = sizeof(ss);
  if(getsockname(portsock, (struct sockaddr *)sa, &sslen)<0) {
    failf(data, "getsockname() failed: %s",
          Curl_strerror(conn, Curl_ourerrno()) );
    return CURLE_FTP_PORT_FAILED;
  }

  /* step 4, listen on the socket */

  if (listen(portsock, 1) < 0) {
    error = Curl_ourerrno();
    sclose(portsock);
    failf(data, "socket failure: %s", Curl_strerror(conn, error));
    return CURLE_FTP_PORT_FAILED;
  }

  /* step 5, send the proper FTP command */

  /* get a plain printable version of the numerical address to work with
     below */
  Curl_printable_address(ai, myhost, sizeof(myhost));

#ifdef PF_INET6
  if(!conn->bits.ftp_use_eprt && conn->bits.ipv6)
    /* EPRT is disabled but we are connected to a IPv6 host, so we ignore the
       request and enable EPRT again! */
    conn->bits.ftp_use_eprt = TRUE;
#endif

  for (; fcmd != DONE; fcmd++) {

    if(!conn->bits.ftp_use_eprt && (EPRT == fcmd))
      /* if disabled, goto next */
      continue;

    switch (sa->sa_family) {
    case AF_INET:
      port = ntohs(((struct sockaddr_in *)sa)->sin_port);
      break;
    case AF_INET6:
      port = ntohs(((struct sockaddr_in6 *)sa)->sin6_port);
      break;
    default:
      break;
    }

    if (EPRT == fcmd) {
      /*
       * Two fine examples from RFC2428;
       *
       * EPRT |1|132.235.1.2|6275|
       *
       * EPRT |2|1080::8:800:200C:417A|5282|
       */

      result = Curl_nbftpsendf(conn, "%s |%d|%s|%d|", mode[fcmd],
                               ai->ai_family == AF_INET?1:2,
                               myhost, port);
      if(result)
        return result;
      break;
    }
    else if (PORT == fcmd) {
      char *source = myhost;
      char *dest = tmp;

      if ((PORT == fcmd) && ai->ai_family != AF_INET)
        continue;

      /* translate x.x.x.x to x,x,x,x */
      while(source && *source) {
        if(*source == '.')
          *dest=',';
        else
          *dest = *source;
        dest++;
        source++;
      }
      *dest = 0;
      snprintf(dest, 20, ",%d,%d", port>>8, port&0xff);

      result = Curl_nbftpsendf(conn, "%s %s", mode[fcmd], tmp);
      if(result)
        return result;
      break;
    }
  }

  /* store which command was sent */
  ftp->count1 = fcmd;

  /* we set the secondary socket variable to this for now, it is only so that
     the cleanup function will close it in case we fail before the true
     secondary stuff is made */
  if(CURL_SOCKET_BAD != conn->sock[SECONDARYSOCKET])
    sclose(conn->sock[SECONDARYSOCKET]);
  conn->sock[SECONDARYSOCKET] = portsock;

#else
  /******************************************************************
   * IPv4-specific section
   */
  struct sockaddr_in sa;
  unsigned short porttouse;
  bool sa_filled_in = FALSE;