dropper.c

来自「rtpfiletransfer 使用udp封装rtp的实现文件传输协议」· C语言 代码 · 共 73 行

/*
 * dropper.c
 * CS 3251 packet dropper
 * Russ Clark
 */ 

//#include <sys/types.h>
#include <winsock.h>
//#include <netinet/in.h>
//#include <arpa/inet.h>
#include <string.h>
#include <stdio.h>
//#include <unistd.h>
#include <stdlib.h>
//#include <sys/time.h>

#include "libcommon.h"
ENABLE_DEBUG()

/* GLOBAL DEFINITIONS
 * All defaults are set to zero
 */

static int DROPPER_loss_percentage = 0;

int set_dropper(int L)
{
   struct timeval current_time;

   if ((L <0) || (L>100)) { 
       /* debug print - see libcommon.h */
       print("set_dropper: Invalid value of loss percentage\n");
       return -1;
   }
  
   DROPPER_loss_percentage = L;

   /* debug print - see libcommon.h */  
   aprint("set_dropper: loss percentage set to %d\n",
              DROPPER_loss_percentage);


   gettimeofday(&current_time,NULL);
   srand(current_time.tv_usec);

   return 1;
} /* set_dropper */

/* dropper version of sendto..accepting the same parameters */
ssize_t sendto_dropper(
      int s, 
      const void *msg, 
      size_t len,
      int flags,
      const struct sockaddr *to,
      int tolen
    ) {
    int randomvalue;
    int nbytes;
     
    randomvalue = rand() % 100;
    
    if (randomvalue < DROPPER_loss_percentage) {  
        /* packet is lost --- do nothing, but make it look like success */
	return(len);
    }
    
    /* default: nothing wrong, call sendto as is.. */
    nbytes = sendto(s,msg,len,flags,to,tolen);
    return(nbytes);

} /* sendto_dropper */