url.c

      case 'A': /* ASCII mode */
        data->set.prefer_ascii = TRUE;
        break;
      case 'D': /* directory mode */
        data->set.ftp_list_only = TRUE;
        break;
      case 'I': /* binary mode */
      default:
        /* switch off ASCII */
        data->set.prefer_ascii = FALSE;
        break;
      }
    }
#else /* CURL_DISABLE_FTP */
    failf(data, LIBCURL_NAME
          " was built with FTP disabled, ftp/ftps: not supported!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }

  else if(strequal(conn->protostr, "TELNET")) {
#ifndef CURL_DISABLE_TELNET
    /* telnet testing factory */
    conn->protocol |= PROT_TELNET;

    conn->port = PORT_TELNET;
    conn->remote_port = PORT_TELNET;
    conn->curl_do = Curl_telnet;
    conn->curl_done = Curl_telnet_done;
#else
    failf(data, LIBCURL_NAME
          " was built with TELNET disabled!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }

  else if (strequal(conn->protostr, "DICT")) {
#ifndef CURL_DISABLE_DICT
    conn->protocol |= PROT_DICT;
    conn->port = PORT_DICT;
    conn->remote_port = PORT_DICT;
    conn->curl_do = Curl_dict;
    /* no DICT-specific done */
    conn->curl_done = (Curl_done_func)ZERO_NULL;
#else
    failf(data, LIBCURL_NAME
          " was built with DICT disabled!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }

  else if (strequal(conn->protostr, "LDAP")) {
#ifndef CURL_DISABLE_LDAP
    conn->protocol |= PROT_LDAP;
    conn->port = PORT_LDAP;
    conn->remote_port = PORT_LDAP;
    conn->curl_do = Curl_ldap;
    /* no LDAP-specific done */
    conn->curl_done = (Curl_done_func)ZERO_NULL;
#else
    failf(data, LIBCURL_NAME
          " was built with LDAP disabled!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }

#ifdef HAVE_LDAP_SSL
  else if (strequal(conn->protostr, "LDAPS")) {
#ifndef CURL_DISABLE_LDAP
    conn->protocol |= PROT_LDAP|PROT_SSL;
    conn->port = PORT_LDAPS;
    conn->remote_port = PORT_LDAPS;
    conn->curl_do = Curl_ldap;
    /* no LDAP-specific done */
    conn->curl_done = (Curl_done_func)ZERO_NULL;
#else
    failf(data, LIBCURL_NAME
          " was built with LDAP disabled!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }
#endif /* CURL_LDAP_USE_SSL */

  else if (strequal(conn->protostr, "FILE")) {
#ifndef CURL_DISABLE_FILE
    conn->protocol |= PROT_FILE;

    conn->curl_do = Curl_file;
    conn->curl_done = Curl_file_done;
#else
    failf(data, LIBCURL_NAME
          " was built with FILE disabled!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }

  else if (strequal(conn->protostr, "TFTP")) {
#ifndef CURL_DISABLE_TFTP
    char *type;
    conn->socktype = SOCK_DGRAM; /* UDP datagram based */
    conn->protocol |= PROT_TFTP;
    conn->port = PORT_TFTP;
    conn->remote_port = PORT_TFTP;
    conn->curl_connect = Curl_tftp_connect;
    conn->curl_do = Curl_tftp;
    conn->curl_done = Curl_tftp_done;
    /* TFTP URLs support an extension like ";mode=<typecode>" that
     * we'll try to get now! */
    type=strstr(data->reqdata.path, ";mode=");
    if(!type) {
      type=strstr(conn->host.rawalloc, ";mode=");
    }
    if(type) {
      char command;
      *type=0;                     /* it was in the middle of the hostname */
      command = (char)toupper((int)type[6]);
      switch(command) {
      case 'A': /* ASCII mode */
      case 'N': /* NETASCII mode */
        data->set.prefer_ascii = TRUE;
        break;
      case 'O': /* octet mode */
      case 'I': /* binary mode */
      default:
        /* switch off ASCII */
        data->set.prefer_ascii = FALSE;
        break;
      }
    }
#else
    failf(data, LIBCURL_NAME
          " was built with TFTP disabled!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }

  else if (strequal(conn->protostr, "SCP")) {
#ifdef USE_LIBSSH2
    conn->port = PORT_SSH;
    conn->remote_port = PORT_SSH;
    conn->protocol = PROT_SCP;
    conn->curl_connect = Curl_ssh_connect; /* ssh_connect? */
    conn->curl_do = Curl_scp_do;
    conn->curl_done = Curl_scp_done;
    conn->curl_connecting = Curl_ssh_multi_statemach;
    conn->curl_doing = Curl_scp_doing;
    conn->curl_do_more = (Curl_do_more_func)ZERO_NULL;
#else
    failf(data, LIBCURL_NAME
          " was built without LIBSSH2, scp: not supported!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }

  else if (strequal(conn->protostr, "SFTP")) {
#ifdef USE_LIBSSH2
    conn->port = PORT_SSH;
    conn->remote_port = PORT_SSH;
    conn->protocol = PROT_SFTP;
    conn->curl_connect = Curl_ssh_connect; /* ssh_connect? */
    conn->curl_do = Curl_sftp_do;
    conn->curl_done = Curl_sftp_done;
    conn->curl_connecting = Curl_ssh_multi_statemach;
    conn->curl_doing = Curl_sftp_doing;
    conn->curl_do_more = (Curl_do_more_func)ZERO_NULL;
#else
    failf(data, LIBCURL_NAME
          " was built without LIBSSH2, scp: not supported!");
    return CURLE_UNSUPPORTED_PROTOCOL;
#endif
  }

  else {
    /* We fell through all checks and thus we don't support the specified
       protocol */
    failf(data, "Unsupported protocol: %s", conn->protostr);
    return CURLE_UNSUPPORTED_PROTOCOL;
  }
  return CURLE_OK;
}

/****************************************************************
* Detect what (if any) proxy to use. Remember that this selects a host
* name and is not limited to HTTP proxies only.
* The returned pointer must be freed by the caller (unless NULL)
****************************************************************/
static char *detect_proxy(struct connectdata *conn)
{
  char *proxy = NULL;

#ifndef CURL_DISABLE_HTTP
  /* If proxy was not specified, we check for default proxy environment
   * variables, to enable i.e Lynx compliance:
   *
   * http_proxy=http://some.server.dom:port/
   * https_proxy=http://some.server.dom:port/
   * ftp_proxy=http://some.server.dom:port/
   * no_proxy=domain1.dom,host.domain2.dom
   *   (a comma-separated list of hosts which should
   *   not be proxied, or an asterisk to override
   *   all proxy variables)
   * all_proxy=http://some.server.dom:port/
   *   (seems to exist for the CERN www lib. Probably
   *   the first to check for.)
   *
   * For compatibility, the all-uppercase versions of these variables are
   * checked if the lowercase versions don't exist.
   */
  char *no_proxy=NULL;
  char *no_proxy_tok_buf;
  char proxy_env[128];

  no_proxy=curl_getenv("no_proxy");
  if(!no_proxy)
    no_proxy=curl_getenv("NO_PROXY");

  if(!no_proxy || !strequal("*", no_proxy)) {
    /* NO_PROXY wasn't specified or it wasn't just an asterisk */
    char *nope;

    nope=no_proxy?strtok_r(no_proxy, ", ", &no_proxy_tok_buf):NULL;
    while(nope) {
      size_t namelen;
      char *endptr = strchr(conn->host.name, ':');
      if(endptr)
	namelen=endptr-conn->host.name;
      else
	namelen=strlen(conn->host.name);

      if(strlen(nope) <= namelen) {
	char *checkn=
	  conn->host.name + namelen - strlen(nope);
	if(checkprefix(nope, checkn)) {
	  /* no proxy for this host! */
	  break;
	}
      }
      nope=strtok_r(NULL, ", ", &no_proxy_tok_buf);
    }
    if(!nope) {
      /* It was not listed as without proxy */
      char *protop = conn->protostr;
      char *envp = proxy_env;
      char *prox;

      /* Now, build <protocol>_proxy and check for such a one to use */
      while(*protop)
	*envp++ = (char)tolower((int)*protop++);

      /* append _proxy */
      strcpy(envp, "_proxy");

      /* read the protocol proxy: */
      prox=curl_getenv(proxy_env);

      /*
       * We don't try the uppercase version of HTTP_PROXY because of
       * security reasons:
       *
       * When curl is used in a webserver application
       * environment (cgi or php), this environment variable can
       * be controlled by the web server user by setting the
       * http header 'Proxy:' to some value.
       *
       * This can cause 'internal' http/ftp requests to be
       * arbitrarily redirected by any external attacker.
       */
      if(!prox && !strequal("http_proxy", proxy_env)) {
	/* There was no lowercase variable, try the uppercase version: */
	for(envp = proxy_env; *envp; envp++)
	  *envp = (char)toupper((int)*envp);
	prox=curl_getenv(proxy_env);
      }

      if(prox && *prox) { /* don't count "" strings */
	proxy = prox; /* use this */
      }
      else {
	proxy = curl_getenv("all_proxy"); /* default proxy to use */
	if(!proxy)
	  proxy=curl_getenv("ALL_PROXY");
      }

      if(proxy && *proxy) {
	long bits = conn->protocol & (PROT_HTTPS|PROT_SSL|PROT_MISSING);

	if(conn->proxytype == CURLPROXY_HTTP) {
	  /* force this connection's protocol to become HTTP */
	  conn->protocol = PROT_HTTP | bits;
	  conn->bits.httpproxy = TRUE;
	}
      }
    } /* if (!nope) - it wasn't specified non-proxy */
  } /* NO_PROXY wasn't specified or '*' */
  if(no_proxy)
    free(no_proxy);

#else /* !CURL_DISABLE_HTTP */

  (void)conn;
#endif /* CURL_DISABLE_HTTP */

  return proxy;
}

/* If this is supposed to use a proxy, we need to figure out the proxy
 * host name, so that we can re-use an existing connection
 * that may exist registered to the same proxy host.
 * proxy will be freed before this function returns.
 */
static CURLcode parse_proxy(struct SessionHandle *data,
                            struct connectdata *conn, char *proxy)
{
  char *prox_portno;
  char *endofprot;

  /* We use 'proxyptr' to point to the proxy name from now on... */
  char *proxyptr=proxy;
  char *portptr;
  char *atsign;

  /* We do the proxy host string parsing here. We want the host name and the
   * port name. Accept a protocol:// prefix, even though it should just be
   * ignored.
   */

  /* Skip the protocol part if present */
  endofprot=strstr(proxyptr, "://");
  if(endofprot)
    proxyptr = endofprot+3;

  /* Is there a username and password given in this proxy url? */
  atsign = strchr(proxyptr, '@');
  if(atsign) {
    char proxyuser[MAX_CURL_USER_LENGTH];
    char proxypasswd[MAX_CURL_PASSWORD_LENGTH];
    proxypasswd[0] = 0;

    if(1 <= sscanf(proxyptr,
		   "%" MAX_CURL_USER_LENGTH_TXT"[^:]:"
		   "%" MAX_CURL_PASSWORD_LENGTH_TXT "[^@]",
		   proxyuser, proxypasswd)) {
      CURLcode res = CURLE_OK;

      /* found user and password, rip them out.  note that we are
	 unescaping them, as there is otherwise no way to have a
	 username or password with reserved characters like ':' in
	 them. */
      Curl_safefree(conn->proxyuser);
      conn->proxyuser = curl_easy_unescape(data, proxyuser, 0, NULL);

      if(!conn->proxyuser)
	res = CURLE_OUT_OF_MEMORY;
      else {
	Curl_safefree(conn->proxypasswd);
	conn->proxypasswd = curl_easy_unescape(data, proxypasswd, 0, NULL);

	if(!conn->proxypasswd)
	  res = CURLE_OUT_OF_MEMORY;
      }

      if(CURLE_OK == res) {
	conn->bits.proxy_user_passwd = TRUE; /* enable it */
	atsign = strdup(atsign+1); /* the right side of the @-letter */

	if(atsign) {
	  free(proxy); /* free the former proxy string */
	  proxy = proxyptr = atsign; /* now use this instead */
	}
	else
	  res = CURLE_OUT_OF_MEMORY;
      }

      if(res) {
	free(proxy); /* free the allocated proxy string */
	return res;
      }
    }
  }

  /* start scanning for port number at this point */
  portptr = proxyptr;

  /* detect and extract RFC2732-style IPv6-addresses */
  if(*proxyptr == '[') {
    char *ptr = ++proxyptr; /* advance beyond the initial bracket */
    while(*ptr && (ISXDIGIT(*ptr) || (*ptr == ':')))
      ptr++;
    if(*ptr == ']') {
      /* yeps, it ended nicely with a bracket as well */
      *ptr = 0;
      portptr = ptr+1;
    }
    /* Note that if this didn't end with a bracket, we still advanced the
     * proxyptr first, but I can't see anything wrong with that as no host
     * name nor a numeric can legally start with a bracket.
     */
  }

  /* Get port number off proxy.server.com:1080 */
  prox_portno = strchr(portptr, ':');
  if (prox_portno) {
    *prox_portno = 0x0; /* cut off number from host name */
    prox_portno ++;
    /* now set the local port number */
    conn->port = atoi(prox_portno);
  }
  else if(data->set.proxyport) {
    /* None given in the proxy string, then get the default one if it is
       given */
    conn->port = data->set.proxyport;
  }

  /* now, clone the cleaned proxy host name */
  conn->proxy.rawalloc = strdup(proxyptr);
  conn->proxy.name = conn->proxy.rawalloc;

  free(proxy);
  if(!conn->proxy.rawalloc)
    return CURLE_OUT_OF_MEMORY;

  return CURLE_OK;
}

/* Extract the user and password from the authentication string */
static CURLcode parse_proxy_auth(struct SessionHandle *data, struct connectdata *conn)
{
  char proxyuser[MAX_CURL_USER_LENGTH]="";
  char proxypasswd[MAX_CURL_PASSWORD_LENGTH]="";

  sscanf(data->set.str[STRING_PROXYUSERPWD],
	 "%" MAX_CURL_USER_LENGTH_TXT "[^:]:"
	 "%" MAX_CURL_PASSWORD_LENGTH_TXT "[^\n]",
	 proxyuser, proxypasswd);

  conn->proxyuser = curl_easy_unescape(data, proxyuser, 0, NULL);
  if(!conn->proxyuser)
    return CURLE_OUT_OF_MEMORY;

  conn->proxypasswd = curl_easy_unescape(data, proxypasswd, 0, NULL);
  if(!conn->proxypasswd)
    return CURLE_OUT_OF_MEMORY;

  return CURLE_OK;
}

/**
 * CreateConnection() sets up a new connectdata struct, or re-uses an already
 * existing one, and resolves host name.
 *
 * if this function returns CURLE_OK and *async is set to TRUE, the resolve
 * response will be coming asynchronously. If *async is FALSE, the name is
 * already resolved.
 *
 * @param data The sessionhandle pointer
 * @param in_connect is set to the next connection data pointer
 * @param addr is set to the new dns entry for this connection. If this
 *        connection is re-used it will be NULL.
 * @param async is set TRUE/FALSE depending on the nature of this lookup
 * @return CURLcode
 * @see SetupConnection()
 *
 * *NOTE* this function assigns the conn->data pointer!
 */

static CURLcode CreateConnection(struct SessionHandle *data,
                                 struct connectdata **in_connect,
                                 struct Curl_dns_entry **addr,
                                 bool *async)
{

  char *tmp;
  CURLcode result=CURLE_OK;
  struct connectdata *conn;
  struct connectdata *conn_temp = NULL;
  size_t urllen;
  struct Curl_dns_entry *hostaddr;
#if defined(HAVE_ALARM) && !defined(USE_ARES)
  unsigned int prev_alarm=0;
#endif
  char endbracket;
  char user[MAX_CURL_USER_LENGTH];
  char passwd[MAX_CURL_PASSWORD_LENGTH];
  int rc;
  bool reuse;
  char *proxy = NULL;

#ifndef USE_ARES
#ifdef SIGALRM
#ifdef HAVE_SIGACTION
  struct sigaction keep_sigact;   /* store the old struct here */
  bool keep_copysig=FALSE;        /* did copy it? */
#else
#ifdef HAVE_SIGNAL
  void (*keep_sigact)(int);       /* store the old handler here */
#endif /* HAVE_SIGNAL */
#endif /* HAVE_SIGACTION */
#endif /* SIGALRM */
#endif /* USE_ARES */

  *addr = NULL; /* nothing yet */
  *async = FALSE;

  /*************************************************************
   * Check input data
   *************************************************************/

  if(!data->change.url)
    return CURLE_URL_MALFORMAT;

  /* First, split up the current URL in parts so that we can use the
     parts for checking against the already present connections. In order
     to not have to modify everything at once, we allocate a temporary
     connection data struct and fill in for comparison purposes. */

  conn = (struct connectdata *)calloc(1, sizeof(struct connectdata));
  if(!conn) {
    *in_connect = NULL; /* clear the pointer */
    return CURLE_OUT_OF_MEMORY;
  }
  /* We must set the return variable as soon as possible, so that our
     parent can cleanup any possible allocs we may have done before
     any failure */
  *in_connect = conn;

  /* and we setup a few fields in case we end up actually using this struct */

  conn->data = data; /* Setup the association between this connection
                        and the SessionHandle */

  conn->sock[FIRSTSOCKET] = CURL_SOCKET_BAD;     /* no file descriptor */
  conn->sock[SECONDARYSOCKET] = CURL_SOCKET_BAD; /* no file descriptor */
  conn->connectindex = -1;    /* no index */

  conn->proxytype = data->set.proxytype; /* type */
  conn->bits.proxy = (bool)(data->set.str[STRING_PROXY] &&
                            *data->set.str[STRING_PROXY]);
  conn->bits.httpproxy = (bool)(conn->bits.proxy
                                && (conn->proxytype == CURLPROXY_HTTP));


  /* Default protocol-independent behavior doesn't support persistent
     connections, so we set this to force-close. Protocols that support
     this need to set this to FALSE in their "curl_do" functions. */
  conn->bits.close = TRUE;

  conn->readchannel_inuse = FALSE;
  conn->writechannel_inuse = FALSE;

  conn->read_pos = 0;
  conn->buf_len = 0;

  /* Store creation time to help future close decision making */
  conn->created = Curl_tvnow();

  conn->bits.user_passwd = (bool)(NULL != data->set.str[STRING_USERPWD]);
  conn->bits.proxy_user_passwd = (bool)(NULL != data->set.str[STRING_PROXYUSERPWD]);
  conn->bits.no_body = data->set.opt_no_body;
  conn->bits.tunnel_proxy = data->set.tunnel_thru_httpproxy;
  conn->bits.ftp_use_epsv = data->set.ftp_use_epsv;
  conn->bits.ftp_use_eprt = data->set.ftp_use_eprt;

  if (data->multi && Curl_multi_canPipeline(data->multi) &&
      !conn->master_buffer) {
    /* Allocate master_buffer to be used for pipelining */
    conn->master_buffer = calloc(BUFSIZE, sizeof (char));
    if (!conn->master_buffer)
      return CURLE_OUT_OF_MEMORY;
  }

  /* Initialize the pipeline lists */
  conn->send_pipe = Curl_llist_alloc((curl_llist_dtor) llist_dtor);
  conn->recv_pipe = Curl_llist_alloc((curl_llist_dtor) llist_dtor);
  if (!conn->send_pipe || !conn->recv_pipe)
    return CURLE_OUT_OF_MEMORY;

  /* This initing continues below, see the comment "Continue connectdata
   * initialization here" */

  /***********************************************************
   * We need to allocate memory to store the path in. We get the size of the
   * full URL to be sure, and we need to make it at least 256 bytes since
   * other parts of the code will rely on this fact
   ***********************************************************/
#define LEAST_PATH_ALLOC 256
  urllen=strlen(data->change.url);
  if(urllen < LEAST_PATH_ALLOC)
    urllen=LEAST_PATH_ALLOC;

  /* Free the old buffer */
  Curl_safefree(data->reqdata.pathbuffer);

  /*
   * We malloc() the buffers below urllen+2 to make room for to possibilities:
   * 1 - an extra terminating zero
   * 2 - an extra slash (in case a syntax like "www.host.com?moo" is used)
   */

  data->reqdata.pathbuffer=(char *)malloc(urllen+2);
  if(NULL == data->reqdata.pathbuffer)
    return CURLE_OUT_OF_MEMORY; /* really bad error */
  data->reqdata.path = data->reqdata.pathbuffer;

  conn->host.rawalloc=(char *)malloc(urllen+2);
  if(NULL == conn->host.rawalloc)
    return CURLE_OUT_OF_MEMORY;

  conn->host.name = conn->host.rawalloc;
  conn->host.name[0] = 0;

  result = ParseURLAndFillConnection(data, conn);
  if (result != CURLE_OK) {
      return result;
  }

  /*************************************************************
   * Take care of proxy authentication stuff
   *************************************************************/
  if(conn->bits.proxy_user_passwd) {
    result = parse_proxy_auth(data, conn);
    if (result != CURLE_OK)
    	return result;
  }

  /*************************************************************
   * Detect what (if any) proxy to use
   *************************************************************/
  if (data->set.str[STRING_PROXY]) {
    proxy = strdup(data->set.str[STRING_PROXY]);
    /* if global proxy is set, this is it */
    if(NULL == proxy) {
      failf(data, "memory shortage");
      return CURLE_OUT_OF_MEMORY;
    }
  }

  if (!proxy)
    proxy = detect_proxy(conn);
  if (proxy && !*proxy) {
    free(proxy);  /* Don't bother with an empty proxy string */
    proxy = NULL;
  }
  /* proxy must be freed later unless NULL */

  /*************************************************************
   * No protocol part in URL was used, add it!
   *************************************************************/
  if(conn->protocol&PROT_MISSING) {
    /* We're guessing prefixes here and if we're told to use a proxy or if
       we're gonna follow a Location: later or... then we need the protocol
       part added so that we have a valid URL. */
    char *reurl;

    reurl = aprintf("%s://%s", conn->protostr, data->change.url);

    if(!reurl) {
      Curl_safefree(proxy);
      return CURLE_OUT_OF_MEMORY;
    }

    data->change.url = reurl;
    data->change.url_alloc = TRUE; /* free this later */
    conn->protocol &= ~PROT_MISSING; /* switch that one off again */
  }

  /*************************************************************
   * Setup internals depending on protocol
   *************************************************************/
  result = setup_connection_internals(data, conn);
  if (result != CURLE_OK) {
    Curl_safefree(proxy);
    return result;
  }


  /***********************************************************************
   * If this is supposed to use a proxy, we need to figure out the proxy
   * host name, so that we can re-use an existing connection
   * that may exist registered to the same proxy host.
   ***********************************************************************/
  if (proxy) {
    result = parse_proxy(data, conn, proxy);
    /* parse_proxy has freed the proxy string, so don't try to use it again */
    proxy = NULL;
    if (result != CURLE_OK)
      return result;
  }


  /***********************************************************************
   * file: is a special case in that it doesn't need a network connection
   ***********************************************************************/
#ifndef CURL_DISABLE_FILE
  if (strequal(conn->protostr, "FILE")) {
    /* this is supposed to be the connect function so we better at least check
       that the file is present here! */
    result = Curl_file_connect(conn);

    /* Setup a "faked" transfer that'll do nothing */
    if(CURLE_OK == result) {
      conn->data = data;
      conn->bits.tcpconnect = TRUE; /* we are "connected */

      ConnectionStore(data, conn);

      result = setup_range(data);
      if(result) {
        Curl_file_done(conn, result, FALSE);
        return result;
      }

      result = Curl_setup_transfer(conn, -1, -1, FALSE,
                                   NULL, /* no download */
                                   -1, NULL); /* no upload */
    }

    return result;
  }
#endif

  /*************************************************************
   * If the protocol is using SSL and HTTP proxy is used, we set
   * the tunnel_proxy bit.
   *************************************************************/
  if((conn->protocol&PROT_SSL) && conn->bits.httpproxy)
    conn->bits.tunnel_proxy = TRUE;

  /*************************************************************
   * Take care of user and password authentication stuff
   *************************************************************/

  /*
   * Inputs: data->set.userpwd   (CURLOPT_USERPWD)
   *         data->set.fpasswd   (CURLOPT_PASSWDFUNCTION)
   *         data->set.use_netrc (CURLOPT_NETRC)
   *         conn->host.name
   *         netrc file
   *         hard-coded defaults
   *
   * Outputs: (almost :- all currently undefined)
   *          conn->bits.user_passwd  - non-zero if non-default passwords exist
   *          conn->user              - non-zero length if defined
   *          conn->passwd            -   ditto
   *          conn->host.name          - remove user name and password
   */

  /* At this point, we're hoping all the other special cases have
   * been taken care of, so conn->host.name is at most
   *    [user[:password]]@]hostname
   *
   * We need somewhere to put the embedded details, so do that first.
   */

  user[0] =0;   /* to make everything well-defined */
  passwd[0]=0;

  if (conn->protocol & (PROT_FTP|PROT_HTTP|PROT_SCP|PROT_SFTP)) {
    /* This is a FTP, HTTP, SCP or SFTP URL, we will now try to extract the
     * possible user+password pair in a string like:
     * ftp://user:password@ftp.my.site:8021/README */
    char *ptr=strchr(conn->host.name, '@');
    char *userpass = conn->host.name;
    if(ptr != NULL) {
      /* there's a user+password given here, to the left of the @ */

      conn->host.name = ++ptr;

      /* So the hostname is sane.  Only bother interpreting the
       * results if we could care.  It could still be wasted
       * work because it might be overtaken by the programmatically
       * set user/passwd, but doing that first adds more cases here :-(
       */

      if (data->set.use_netrc != CURL_NETRC_REQUIRED) {
        /* We could use the one in the URL */

        conn->bits.user_passwd = 1; /* enable user+password */

        if(*userpass != ':') {
          /* the name is given, get user+password */
          sscanf(userpass, "%" MAX_CURL_USER_LENGTH_TXT "[^:@]:"
                 "%" MAX_CURL_PASSWORD_LENGTH_TXT "[^@]",
                 user, passwd);
        }
        else
          /* no name given, get the password only */
          sscanf(userpass, ":%" MAX_CURL_PASSWORD_LENGTH_TXT "[^@]", passwd);

        if(user[0]) {
          char *newname=curl_easy_unescape(data, user, 0, NULL);
          if(!newname)
            return CURLE_OUT_OF_MEMORY;
          if(strlen(newname) < sizeof(user))
            strcpy(user, newname);

          /* if the new name is longer than accepted, then just use
             the unconverted name, it'll be wrong but what the heck */
          free(newname);
        }
        if (passwd[0]) {
          /* we have a password found in the URL, decode it! */
          char *newpasswd=curl_easy_unescape(data, passwd, 0, NULL);
          if(!newpasswd)
            return CURLE_OUT_OF_MEMORY;
          if(strlen(newpasswd) < sizeof(passwd))
            strcpy(passwd, newpasswd);

          free(newpasswd);
        }
      }
    }
  }

  /*************************************************************
   * Figure out the remote port number
   *
   * No matter if we use a proxy or not, we have to figure out the remote
   * port number of various reasons.
   *
   * To be able to detect port number flawlessly, we must not confuse them
   * IPv6-specified addresses in the [0::1] style. (RFC2732)
   *
   * The conn->host.name is currently [user:passwd@]host[:port] where host
   * could be a hostname, IPv4 address or IPv6 address.
   *************************************************************/
  if((1 == sscanf(conn->host.name, "[%*39[0-9a-fA-F:.]%c", &endbracket)) &&
     (']' == endbracket)) {
    /* this is a RFC2732-style specified IP-address */
    conn->bits.ipv6_ip = TRUE;

    conn->host.name++; /* pass the starting bracket */
    tmp = strchr(conn->host.name, ']');
    *tmp = 0; /* zero terminate */
    tmp++; /* pass the ending bracket */
    if(':' != *tmp)
      tmp = NULL; /* no port number available */
  }
  else
    tmp = strrchr(conn->host.name, ':');

  if(data->set.use_port && data->state.allow_port) {
    /* if set, we use this and ignore the port possibly given in the URL */
    conn->remote_port = (unsigned short)data->set.use_port;
    if(tmp)
      *tmp = '\0'; /* cut off the name there anyway - if there was a port
                      number - since the port number is to be ignored! */
    if(conn->bits.httpproxy) {
      /* we need to create new URL with the new port number */
      char *url;

      url = aprintf("%s://%s:%d%s", conn->protostr, conn->host.name,
                    conn->remote_port, data->reqdata.path);
      if(!url)
        return CURLE_OUT_OF_MEMORY;

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

      data->change.url = url;
      data->change.url_alloc = TRUE;
    }
  }
  else if (tmp) {
    /* no CURLOPT_PORT given, extract the one from the URL */

    char *rest;
    unsigned long port;

    port=strtoul(tmp+1, &rest, 10);  /* Port number must be decimal */

    if (rest != (tmp+1) && *rest == '\0') {
      /* The colon really did have only digits after it,
       * so it is either a port number or a mistake */

      if (port > 0xffff) {   /* Single unix standard says port numbers are
                              * 16 bits long */
        failf(data, "Port number too large: %lu", port);
        return CURLE_URL_MALFORMAT;
      }

      *tmp = '\0'; /* cut off the name there */
      conn->remote_port = (unsigned short)port;
    }
  }

  /* Programmatically set password:
   *   - always applies, if available
   *   - takes precedence over the values we just set above
   * so scribble it over the top.
   * User-supplied passwords are assumed not to need unescaping.
   *
   * user_password is set in "inherit initial knowledge' above,
   * so it doesn't have to be set in this block
   */
  if (data->set.str[STRING_USERPWD] != NULL) {
    /* the name is given, get user+password */
    sscanf(data->set.str[STRING_USERPWD],
           "%" MAX_CURL_USER_LENGTH_TXT "[^:]:"
           "%" MAX_CURL_PASSWORD_LENGTH_TXT "[^\n]",
           user, passwd);
  }

  conn->bits.netrc = FALSE;
  if (data->set.use_netrc != CURL_NETRC_IGNORED) {
    if(Curl_parsenetrc(conn->host.name,
                       user, passwd,
                       data->set.str[STRING_NETRC_FILE])) {
      infof(data, "Couldn't find host %s in the " DOT_CHAR
            "netrc file, using defaults\n",
            conn->host.name);
    }
    else {
      /* set bits.netrc TRUE to remember that we got the name from a .netrc
         file, so that it is safe to use even if we followed a Location: to a
         different host or similar. */
      conn->bits.netrc = TRUE;

      conn->bits.user_passwd = 1; /* enable user+password */
    }
  }

  /* If our protocol needs a password and we have none, use the defaults */
  if ( (conn->protocol & PROT_FTP) &&
       !conn->bits.user_passwd) {

    conn->user = strdup(CURL_DEFAULT_USER);
    conn->passwd = strdup(CURL_DEFAULT_PASSWORD);
    /* This is the default password, so DON'T set conn->bits.user_passwd */
  }
  else {
    /* store user + password, zero-length if not set */
    conn->user = strdup(user);
    conn->passwd = strdup(passwd);
  }
  if(!conn->user || !conn->passwd)
    return CURLE_OUT_OF_MEMORY;

  /*************************************************************
   * Check the current list of connections to see if we can
   * re-use an already existing one or if we have to create a
   * new one.
   *************************************************************/

  /* Get a cloned copy of the SSL config situation stored in the
     connection struct. But to get this going nicely, we must first make
     sure that the strings in the master copy are pointing to the correct
     strings in the session handle strings array!

     Keep in mind that the pointers in the master copy are pointing to strings
     that will be freed as part of the SessionHandle struct, but all cloned
     copies will be separately allocated.
  */
  data->set.ssl.CApath = data->set.str[STRING_SSL_CAPATH];
  data->set.ssl.CAfile = data->set.str[STRING_SSL_CAFILE];
  data->set.ssl.random_file = data->set.str[STRING_SSL_RANDOM_FILE];
  data->set.ssl.egdsocket = data->set.str[STRING_SSL_EGDSOCKET];
  data->set.ssl.cipher_list = data->set.str[STRING_SSL_CIPHER_LIST];

  if(!Curl_clone_ssl_config(&data->set.ssl, &conn->ssl_config))
    return CURLE_OUT_OF_MEMORY;

  /* reuse_fresh is TRUE if we are told to use a new connection by force, but
     we only acknowledge this option if this is not a re-used connection
     already (which happens due to follow-location or during a HTTP
     authentication phase). */
  if(data->set.reuse_fresh && !data->state.this_is_a_follow)
    reuse = FALSE;
  else
    reuse = ConnectionExists(data, conn, &conn_temp);

  if(reuse) {
    /*
     * We already have a connection for this, we got the former connection
     * in the conn_temp variable and thus we need to cleanup the one we
     * just allocated before we can move along and use the previously
     * existing one.
     */
    struct connectdata *old_conn = conn;

    if(old_conn->proxy.rawalloc)
      free(old_conn->proxy.rawalloc);

    /* free the SSL config struct from this connection struct as this was
       allocated in vain and is targeted for destruction */
    Curl_free_ssl_config(&conn->ssl_config);

    conn = conn_temp;        /* use this connection from now on */

    conn->data = old_conn->data;

    /* get the user+password information from the old_conn struct since it may
     * be new for this request even when we re-use an existing connection */
    conn->bits.user_passwd = old_conn->bits.user_passwd;
    if (conn->bits.user_passwd) {
      /* use the new user namd and password though */
      Curl_safefree(conn->user);
      Curl_safefree(conn->passwd);
      conn->user = old_conn->user;
      conn->passwd = old_conn->passwd;
      old_conn->user = NULL;