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[fwd] / listener.c

/* -*-c-*-
 *
 * $Id: listener.c,v 1.1 1999/07/01 08:56:23 mdw Exp $
 *
 * A port forwarding listener
 *
 * (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: listener.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 <unistd.h>
#include <fcntl.h>

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

#include <mLib/alloc.h>
#include <mLib/dstr.h>
#include <mLib/report.h>
#include <mLib/sel.h>
#include <mLib/sub.h>

#include "acl.h"
#include "forward.h"
#include "fw.h"
#include "identify.h"
#include "listener.h"

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

/* --- @doclose@ --- *
 *
 * Arguments:	@void *vp@ = pointer to file descriptor to close
 *
 * Returns:	---
 *
 * Use:		Closes a file descriptor once it's no longer useful.
 */

static void doclose(void *vp)
{
  int *fd = vp;
  close(*fd);
  DESTROY(fd);
}

/* --- @newconn@ --- *
 *
 * Arguments:	@int fd@ = file descriptor which is ready
 *		@unsigned state@ = state in which file descriptor is
 *		@void *vp@ = pointer to listener block
 *
 * Returns:	---
 *
 * Use:		Responds to a new connection.
 */

static void newconn(int fd, unsigned state, void *vp)
{
  int nfd;
  id_req q;
  int lsinsz = sizeof(q.lsin), rsinsz = sizeof(q.rsin);
  int f;
  listener *l = vp;

  /* --- Accept the new connection --- */

  if ((nfd = accept(fd, (struct sockaddr *)&q.rsin, &rsinsz)) < 0)
    return;
  if (getsockname(nfd, (struct sockaddr *)&q.lsin, &lsinsz)) {
    close(nfd);
    return;
  }
  q.desc = l->desc;

  /* --- Find out whether this connection is allowed --- */

  if (!acl_check(l->acl, q.rsin.sin_addr)) {
    int *fdp = CREATE(int);
    *fdp = nfd;
    q.act = "refused";
    identify(&q, doclose, fdp);
    return;
  }

  /* --- Set the socket nonblocking --- */

  if ((f = fcntl(nfd, F_GETFL)) >= 0)
    fcntl(nfd, F_SETFL, f | O_NONBLOCK);

  /* --- Open a new forwarding context for the connection --- */

  q.act = "accepted";
  forward(nfd, &l->sin, &q);
}

/* --- @listener_dump@ --- *
 *
 * Arguments:	@listener *l@ = pointer to listener block
 *		@FILE *fp@ = stream to dump on
 *
 * Returns:	---
 *
 * Use:		Dumps a listener to an output stream.
 */

void listener_dump(listener *l, FILE *fp)
{
  struct sockaddr_in sin;
  int sinsz = sizeof(sin);

  getsockname(l->rd.fd, (struct sockaddr *)&sin, &sinsz);
  fprintf(fp, "forward port %u to ", ntohs(sin.sin_port));
  fputs(inet_ntoa(l->sin.sin_addr), fp);
  fprintf(fp, ":%u; acl:\n", ntohs(l->sin.sin_port));
  if (l->acl)
    acl_dump(l->acl, fp);
}

/* --- @listener_add@ --- *
 *
 * Arguments:	@int fd@ = created listening socket
 *		@unsigned sp@ = source port number
 *		@struct sockaddr_in *sin@ = pointer to destination address
 *
 * Returns:	The address of the new listener.
 *
 * Use:		Adds a forwarding listener.
 */

listener *listener_add(int fd, unsigned sp, struct sockaddr_in *sin)
{
  int f;
  listener *l = CREATE(listener);
  dstr d = DSTR_INIT;

  l->sin = *sin;
  l->acl = 0;
  f = fcntl(fd, F_GETFL);
  if (f != -1)
    fcntl(fd, F_SETFL, f | O_NONBLOCK);
  sel_initfile(sel, &l->rd, fd, SEL_READ, newconn, l);
  sel_addfile(&l->rd);
  dstr_putf(&d, "fw %u -> %s:%u",
	    ntohs(sp), inet_ntoa(sin->sin_addr), ntohs(sin->sin_port));
  l->desc = xstrdup(d.buf);
  dstr_destroy(&d);
  return (l);
}

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