//-------------------------------------------------------------------
//	echotest.cpp
//
//	This program sends ethernet frames of varying lengths which
//	contain our distinctive protocol-identifier and filled with 
//	randomly generated data; it assumes that our 'sendback.cpp'
//	is executing on another station on the local network.  Then
//	statistics are shown on the count of validly echoed frames.  
//
//	programmer: ALLAN CRUSE
//	written on: 01 MAY 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), write() 
#include <string.h>	// for memcpy(), memset()
#include <netdb.h>	// for gethostbyname(), htons()
#include <sys/ioctl.h>	// ioctl()

#define MY_TYPE	0x0635	// our protocol-type identifier
#define N_FRAMES  2048	// total number of frames 

char nicname[] = "/dev/nic";
unsigned char nicaddr[10];

int main( int argc, char **argv )
{
	// open device-file and get hardware-address
	int	nic = open( nicname, O_RDWR );
	if ( nic < 0 ) { perror( nicname ); exit(1); }
	if ( ioctl( nic, 0, &nicaddr ) < 0 ) { perror( "ioctl" ); exit(1); }

	// get this station's IP-address
	char	hostname[64] = {0};
	gethostname( hostname, 64 );
	struct hostent	*hostinfo = gethostbyname( hostname );
	if ( !hostinfo ) { perror( "gethostbyname" ); exit(1); }
	memcpy( nicaddr+6, hostinfo->h_addr_list[0], 4 );

	printf( "\n\tstation-hostname: %s ", hostname );
	printf( "\n\tprotocol-address: " );
	for (int i = 0; i < 4; i++)
		{
		printf( "%d", nicaddr[6+i] );
		if ( i < 3 ) printf( "." ); else printf( " " );	
		}
	printf( "\n\thardware-address: " );
	for (int i = 0; i < 6; i++)
		{
		printf( "%02X", nicaddr[i] );
		if ( i < 5 ) printf( ":" ); else printf( " " );	
		}
	printf( "\n\n" );


	// the echo testing begins here
	unsigned char	query[ 4096 ] = {0}, *q = query; 
	unsigned char	reply[ 4096 ] = {0}, *r = reply;
	int	frames = 0, errors = 0, oktotal = 0;
	for (int i = 0; i < N_FRAMES; i++)
		{
		int	pktlen = rand()%1514;	// random frame-size
		if ( pktlen < 64 ) pktlen = 64;	// cannot be below 64

		// create ethernet packet having our protocol-type
		memset( query+0, 0xFF, 6 );	// dest'n hw-address
		memcpy( query+6, nicaddr, 6 );	// source hw-address
		*(short*)(query+12) = htons( MY_TYPE );	// Type/Len
		// fill remainder of packet with random data-bytes
		for (int j = 16; j < pktlen; j++) 
			query[j] = (unsigned char)rand();		

		// transmit the packet containing our random data
		int	txbytes = write( nic, query, pktlen );
		if ( txbytes < 0 ) { perror( "write" ); exit(1); }
		else	++frames;	// count this transmission

		// receive packets until our protocol is recognized		
		int	rxbytes;	
		for(;;)	{
			rxbytes = read( nic, reply, sizeof( reply ) );
			if ( rxbytes < 0 ) { perror( "read" ); exit(1); }
			if ( *(short*)(reply+12) == htons( MY_TYPE ) ) break;
			}

		// check whether reply-data matches query-data
		int	match = ( txbytes == rxbytes ) ? 0 : -1;
		for (int j = 12; j < txbytes; j++) 
			match |= ( query[j] ^ reply[j] )&0xFF;
		if ( match == 0 ) oktotal += txbytes;
		else	++errors;	// count this error-packet 

		// verbose reporting of individual echo-transaction
		printf( "#%-5d ", i+1 );
		printf( "sent %d bytes  ", txbytes );
		printf( "read %d bytes  ", rxbytes );
		printf( "match=%d  \n", match );	
		}		

	// report the testing statistics
	printf( "\ncorrectly echoed %d bytes \n", oktotal );
	printf( "correctly echoed %d packets \n", frames - errors );
	printf( "incorrectly echoed %d packets \n\n", errors );
}