/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program 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 this program (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef SHAPER_H
#define SHAPER_H

/*#define SHAPER_DEBUG*/

#ifdef HAVE_GETTIMEOFDAY

#include "basic.h"
#include "integer.h"
#include "misc.h"
#include "error.h"
#include "interval.h"

/*
 * A simple traffic shaper for
 * the output direction.
 */

#define SHAPER_MIN 100          /* bytes per second */
#define SHAPER_MAX 100000000

#define SHAPER_MAX_TIMEOUT 10   /* seconds */

#define SHAPER_USE_FP

struct shaper 
{
  int bytes_per_second;
  struct timeval wakeup;

#ifdef SHAPER_USE_FP
  double factor;
#else
  int factor;
#endif
};

void shaper_msg (struct shaper *s);
void shaper_reset_wakeup (struct shaper *s);

/*
 * We want to wake up in delay microseconds.  If timeval is larger
 * than delay, set timeval to delay.
 */
bool shaper_soonest_event (struct timeval *tv, int delay);

/*
 * inline functions
 */

static inline void
shaper_reset (struct shaper *s, int bytes_per_second)
{
  s->bytes_per_second = bytes_per_second ? constrain_int (bytes_per_second, SHAPER_MIN, SHAPER_MAX) : 0;

#ifdef SHAPER_USE_FP
  s->factor = 1000000.0 / (double)s->bytes_per_second;
#else
  s->factor = 1000000 / s->bytes_per_second;
#endif
}

static inline void
shaper_init (struct shaper *s, int bytes_per_second)
{
  shaper_reset (s, bytes_per_second);
  shaper_reset_wakeup (s);
}

static inline int
shaper_current_bandwidth (struct shaper *s)
{
  return s->bytes_per_second;
}

/*
 * Returns traffic shaping delay in microseconds relative to current
 * time, or 0 if no delay.
 */
static inline int
shaper_delay (struct shaper* s)
{
  struct timeval tv;
  int delay = 0;

  if (tv_defined (&s->wakeup))
    {
      ASSERT (!openvpn_gettimeofday (&tv, NULL));
      delay = tv_subtract (&s->wakeup, &tv, SHAPER_MAX_TIMEOUT);
#ifdef SHAPER_DEBUG
      dmsg (D_SHAPER_DEBUG, "SHAPER shaper_delay delay=%d", delay);
#endif
    }

  return delay > 0 ? delay : 0;
}


/*
 * We are about to send a datagram of nbytes bytes.
 *
 * Compute when we can send another datagram,
 * based on target throughput (s->bytes_per_second).
 */
static inline void
shaper_wrote_bytes (struct shaper* s, int nbytes)
{
  struct timeval tv;

  /* compute delay in microseconds */
  tv.tv_sec = 0;
#ifdef SHAPER_USE_FP
  tv.tv_usec = min_int ((int)((double)max_int (nbytes, 100) * s->factor), (SHAPER_MAX_TIMEOUT*1000000));
#else
  tv.tv_usec = s->bytes_per_second
    ? min_int (max_int (nbytes, 100) * s->factor, (SHAPER_MAX_TIMEOUT*1000000))
    : 0;
#endif

  if (tv.tv_usec)
    {
      ASSERT (!openvpn_gettimeofday (&s->wakeup, NULL));
      tv_add (&s->wakeup, &tv);

#ifdef SHAPER_DEBUG
      dmsg (D_SHAPER_DEBUG, "SHAPER shaper_wrote_bytes bytes=%d delay=%d sec=%d usec=%d",
	   nbytes,
	   (int)tv.tv_usec,
	   (int)s->wakeup.tv_sec,
	   (int)s->wakeup.tv_usec);
#endif
    }
}

#if 0
/*
 * Increase/Decrease bandwidth by a percentage.
 *
 * Return true if bandwidth changed.
 */
static inline bool
shaper_change_pct (struct shaper *s, int pct)
{
  const int orig_bandwidth = s->bytes_per_second;
  const int new_bandwidth = orig_bandwidth + (orig_bandwidth * pct / 100);
  ASSERT (s->bytes_per_second);
  shaper_reset (s, new_bandwidth);
  return s->bytes_per_second != orig_bandwidth;
}
#endif

#endif /* HAVE_GETTIMEOFDAY */

#endif
