afclient(1)

NAME
afclient - active port forwarder client

SYNOPSIS
afclient [ options ] -n servername -p portnum

DESCRIPTION
Afclient is a port forwarding program designed to be efficient and easy to use. It connects to afserver to listenport (default listenport is 50126) and after a successful authorization afclient redirects all the data to the specified destination host:port.

EXAMPLES
afclient -n servername -p 22
  program connects to servername:50126 and redirects data to local port 22 (becomes a daemon) afclient -n servername -p 22 -v
  the same as above, but verbose mode is enabled (program won't enter daemon mode) afclient -n servername -r
  program connects to servername:50126 in remote administration mode

OPTIONS
Basic options -n, --servername NAME
  name of the host, where afserver is running (required) -m, --manageport PORT
  manage port number - server must be listening on it (default: 50126) -d, --hostname NAME
  the name of this host/remote host - the final destination of the packets (default: the name returned by hostname function) -p, --portnum PORT
  the port we are forwarding connection to (required) -h, --help
  prints help screen Authorization -i, --id STRING
  sends the id string to afserver

--pass PASSWORD
  set the password used for client identification (default: no password) Configuration -k, --keyfile FILE
  the name of the file with RSA key (default: client.rsa)

-D, --dateformat FORMAT
  format of the date printed in logs (see 'man strftime' for details) (default: %d.%m.%Y %H:%M:%S) Modes -u, --udpmode
  udp mode - client will use udp protocol to communicate with the hostname:portnum (-p) -U, --reverseudp
  reverse udp forwarding. Udp packets will be forwarded from hostname:portnum (-p) to the server name:portnum (-m)

-r, --remoteadmin
  remote administration mode. (using '-p PORT' will force afclient to use port rather then stdin-stdout) Logging -O, --heavylog
  logging everything to a logfile -o, --lightlog
  logging some data to a logfile -S, --heavysocklog
  logging everything to a localport -s, --lightsocklog
  logging some data to a localport -v, --verbose
  to be verbose - program won't enter the daemon mode (use several times for greater effect) IP family -4, --ipv4
  use ipv4 only -6, --ipv6
  use ipv6 only Modules -l, --load
  load a module for user's packets filtering -L, --Load
  load a module for service's packets filtering

REMOTE ADMINISTRATION
Remote administration mode is enabled by '-r, --remoteadmin' option. Required options: '-n, --servername NAME' After successful authorization stdin/stdout are used to communicate with user. All the commands parsing is done by afserver. Commands guaranteed to be available: help
  display help lcmd
  lists available commands quit
  quit connection For list of all available commands take a look at afserver(1). When '-p, --portnum PORT' is used, afclient listens for connection from user at NAME:PORT. NAME is set by '-d, --hostname' option or hostname() function, when the option is missing. When user quits (close the connection or send 'quit' command), afclient exits.

MODULES
Afclient can use external modules for user's packets filtering ('-l, --load') and service's packets filtering ('-L, --Load'). Module file has to declare three functions: char* info(void);

  info() return values:
  - info about module
  Example:
  char*
  info(void)
  {
    return "Module tester v0.1";
  }

int allow(char* host, char* port);

  allow() return values:
  0 - allow to connect
  !0 - drop the connection

  Example:

  int
  allow(char* host, char* port)
  {
    return 0; /* allow to connect */
  }

int filter(char* host, unsigned char* message, int* length);
  filter() return values:
  0 - allow to transfer
  1 - drop the packet
  2 - drop the connection
  3 - release the module
  4 - drop the packet and release the module
  5 - drop the connection and release the module
  Example:
  int
  filter(char* host, unsigned char* message, int* length)
  {
    int i;
    for (i = 1; i < *length; ++i) {
      if (message[i-1] == 'M') {
        if (message[i] == '1') {
          return 1; /* ignored */
        }
        if (message[i] == '2') {
          return 2; /* dropped */
        }
        if (message[i] == '3') {
          return 3; /* release */
        }
        if (message[i] == '4') {
          return 4; /* ignored + release */
        }
        if (message[i] == '5') {
          return 5; /* dropped + release */
        }
      }
    }
    return 0; /* allow to transfer */
  } Modules have to be compiled with -fPIC -shared options.

SEE ALSO
afserver(1), afserver.conf(5)

BUGS
Afclient is still under development. There are no known open bugs at the moment.

REPORTING BUGS
Please report bugs to <jeremian [at] poczta.fm>

AUTHOR
Jeremian <jeremian [at] poczta.fm>

CONTRIBUTIONS
Alex Dyatlov <alex [at] gray-world.net>, Simon <scastro [at] entreelibre.com>, Ilia Perevezentsev <iliaper [at] mail.ru> and Marco Solari <marco.solari [at] koinesistemi.it>

LICENSE
Active Port Forwarder is distributed under the terms of the GNU General Public License v2.0 and is copyright (C) 2003,2004,2005 jeremian <jeremian [at] poczta.fm>. See the file COPYING for details.