Various changes. Add configuration grammar to help text. Change to

[fwd] / forward.c

/* -*-c-*-
 *
 * $Id: forward.c,v 1.1 1999/07/01 08:56:23 mdw Exp $
 *
 * Port forwarding
 *
 * (c) 1999 Mark Wooding
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of the `fw' port forwarder.
 *
 * `fw' is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * `fw' is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with `fw'; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: forward.c,v $
 * Revision 1.1  1999/07/01 08:56:23  mdw
 * Initial revision
 *
 */

/*----- Header files ------------------------------------------------------*/

#include "config.h"

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <mLib/alloc.h>
#include <mLib/conn.h>
#include <mLib/sel.h>

#include "chan.h"
#include "forward.h"
#include "fw.h"

/*----- Data structures ---------------------------------------------------*/

/* --- Port forwarding data --- */

typedef struct fw {
  int fd_a;				/* Client's file descriptor */
  int fd_b;				/* Server's file descriptor */
  unsigned state;			/* Current state of the world */
  conn c;				/* Nonblocking connect to server */
  chan ab;				/* Channel from @a@ to @b@ */
  chan ba;				/* Channel from @b@ to @a@ */
} fw;

#define S_AB 1u				/* Channel from @a@ to @b@ open */
#define S_BA 2u				/* Channel from @b@ to @a@ open */
#define S_NOTCONN 4u			/* Not connected to @b@ yet */
#define S_NOTID 8u			/* Not finished identification */

/*----- Main code ---------------------------------------------------------*/

/* --- @done@ --- *
 *
 * Arguments:	@fw *f@ = pointer to forwarder
 *
 * Returns:	---
 *
 * Use:		Tidies up a forwarder that nobody wants any more.
 */

static void done(fw *f)
{
  close(f->fd_a);
  close(f->fd_b);
  free(f);
}

/* --- @ident@ --- *
 *
 * Arguments:	@void *vp@ = pointer to forwarder
 *
 * Returns:	---
 *
 * Use:		Handles completion of client identification.
 */

static void ident(void *vp)
{
  fw *f = vp;
  f->state &= ~S_NOTID;
  if (!f->state)
    done(f);
}
  
/* --- @closeba@ --- *
 *
 * Arguments:	@void *vp@ = pointer to forwarder
 *
 * Returns:	---
 *
 * Use:		Handles the closing of the %$b \rightarrow a$% channel.
 */

static void closeba(void *vp)
{
  fw *f = vp;
  f->state &= ~S_BA;
  if (!f->state)
    done(f);
}

/* --- @closeab@ --- *
 *
 * Arguments:	@void *vp@ = pointer to forwarder
 *
 * Returns:	---
 *
 * Use:		Handles the closing of the %$a \rightarrow b$% channel.
 */

static void closeab(void *vp)
{
  fw *f = vp;
  f->state &= ~S_AB;
  if (!f->state)
    done(f);
}

/* --- @go@ --- *
 *
 * Arguments:	@int fd@ = newly connected socket
 *		@void *vp@ = pointer to forwarder
 *
 * Returns:	---
 *
 * Use:		Completes the forwarder once the outbound connection is set
 *		up.
 */

static void go(int fd, void *vp)
{
  fw *f = vp;

  /* --- If it all went tits-up, deal with that --- */

  if (fd == -1) {
    chan_close(&f->ab);
    close(f->fd_a);
    free(f);
    return;
  }

  /* --- OK, finish configuring the forwarder --- */

  f->fd_b = fd;
  chan_dest(&f->ab, fd);
  chan_open(&f->ba, fd, f->fd_a, closeba, f);
  f->state |= S_BA;
  f->state &= ~S_NOTCONN;
}

/* --- @forward@ --- *
 *
 * Arguments:	@int fd@ = file descriptor attached to client
 *		@struct sockaddr_in *sin@ = pointer to destination address
 *		@const id_req *q@ = pointer to identification request block
 *
 * Returns:	---
 *
 * Use:		Start a port forwarding job.
 */

void forward(int fd, struct sockaddr_in *sin, const id_req *q)
{
  fw *f;
  int nfd;

  /* --- Set up the new socket --- */

  if ((nfd = socket(PF_INET, SOCK_STREAM, 0)) < 0)
    return;

  {
    int opt = 1;
    setsockopt(fd, SOL_SOCKET, SO_OOBINLINE, &opt, sizeof(opt));
    setsockopt(nfd, SOL_SOCKET, SO_OOBINLINE, &opt, sizeof(opt));
  }

  /* --- Initialize the easy bits --- */

  f = xmalloc(sizeof(*f));
  f->fd_a = fd;
  f->fd_b = -1;
  f->state = S_NOTCONN | S_AB | S_NOTID;

  /* --- Open the %$a \rightarrow b$% channel --- */

  chan_open(&f->ab, fd, -1, closeab, f);
  conn_init(&f->c, sel, nfd, (struct sockaddr *)sin, sizeof(*sin), go, f);
  identify(q, ident, f);
}

/*----- That's all, folks -------------------------------------------------*/