/*  
    VTun - Virtual Tunnel over TCP/IP network. 

    Copyright (C) 1998-2008  Maxim Krasnyansky <max_mk@yahoo.com>

    VTun has been derived from VPPP package by Maxim Krasnyansky. 

    This program 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.

    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.
 */

/*
 * $Id: lfd_shaper.c,v 1.7.2.2 2008/01/07 22:35:36 mtbishop Exp $
 */

#include "config.h"
 
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/time.h>
#include <syslog.h>

#include "vtun.h"
#include "linkfd.h"
#include "lib.h"

/* 
 * Shaper module. 
 */

#ifdef HAVE_SHAPER 

unsigned long bytes, max_speed;
struct timeval curr_time, last_time;

/* 
 * Initialization function.
 */
int shaper_init(struct vtun_host *host)
{
     /* Calculate max speed bytes/sec */
     max_speed = host->spd_out / 8 * 1024;
   
     /* Compensation for delays, nanosleep and so on */ 
     max_speed += 400;

     bytes = 0;
     
     vtun_syslog(LOG_INFO,"Traffic shaping(speed %dK) initialized.", host->spd_out);	
     return 0;
}

/* Shaper counter */
int shaper_counter(int len, char *in, char **out)
{ 
     /* Just count incoming bytes */
     bytes += len;

     *out = in;
     return len;
}

/* Convert tv struct to milisec */
unsigned long inline tv2ms(struct timeval tv)
{
     register unsigned long ms = (tv.tv_sec * 1000)+(tv.tv_usec / 1000); 
     return  ms ? ms : 1;
}

#ifndef timersub
/* Some includes doesn't contain this macro */
#define	timersub(a, b, result)				\
  do {							\
    (result)->tv_sec = (a)->tv_sec - (b)->tv_sec;	\
    (result)->tv_usec = (a)->tv_usec - (b)->tv_usec;	\
    if ((result)->tv_usec < 0) {			\
      --(result)->tv_sec;				\
      (result)->tv_usec += 1000000;			\
    }							\
  } while (0)
#endif

/* 
 * Main shaper function.
 * Compute current speed in bytes/sec and if it is
 * higher than maximal speed stop accepting input 
 * until the speed become lower or equal to maximal.
 */
int shaper_avail(void)
{ 
     static struct timeval tv;
     register unsigned long speed;

     /* Let me know if you have faster and better time source. */
     gettimeofday(&curr_time,NULL);

     timersub(&curr_time,&last_time,&tv);

     /* Calculate current speed bytes/sec. 
      * (tv2ms never returns 0) */ 	
     speed = bytes * 1000 / tv2ms(tv); 
	
     if( speed > max_speed ){
	/* 
	 * Sleep about 1 microsec(actual sleep might be longer). 
	 * This is actually the hack to reduce CPU usage. 
	 * Without this delay we will consume 100% CPU.
         */ 
        static struct timespec ts = {0,1000};
     	nanosleep(&ts,NULL);

	/* Don't accept input */
	return 0;
     }

     if( curr_time.tv_sec > last_time.tv_sec ){
        last_time = curr_time;
        bytes = 0;
     }

     /* Accept input */
     return  1;
}

struct lfd_mod lfd_shaper = {
     "Shaper",
     shaper_init,
     shaper_counter,
     shaper_avail,
     NULL,
     NULL,
     NULL,
     NULL,
     NULL
};

#else  /* HAVE_SHAPER */

int no_shaper(struct vtun_host *host)
{
     vtun_syslog(LOG_INFO, "Traffic shaping is not supported");
     return -1;
}

struct lfd_mod lfd_shaper = {
     "Shaper",
     no_shaper, NULL, NULL, NULL, NULL, NULL, NULL, NULL
};

#endif /* HAVE_SHAPER */