//-------------------------------------------------------------------
//	arpquery.cpp
//
//	This application opens the '/dev/nic' device-file in order
//	to transmit an ARP request-packet and receive any replies.
//	It expects our 'rxplustx.c' device-driver to be installed. 
//
//	programmer: ALLAN CRUSE
//	written on: 20 APR 2005
//-------------------------------------------------------------------

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

#define GET_HWADDR	0
#define BUF_SIZE	64

char devname[] = "/dev/nic";	// name of the device special file

int done = 0;
void upon_signal( int sugnum ) { done = 1; }

int main( int argc, char **argv )
{
	// open the device-file
	int	fd = open( devname, O_RDWR );
	if ( fd < 0 ) { perror( devname ); exit(1); }

	// get the network controller's hardware address
	unsigned char	netaddr[ 10 ];
	if ( ioctl( fd, GET_HWADDR, netaddr ) ) { perror( "ioctl" ); exit(1); }
	// get the workstation's hostname and IP-address
	char	hostname[ 64 ] = {0}, hostaddr[ 16 ] = {0};
	gethostname( hostname, 64 );
	struct hostent 	*hostinfo = gethostbyname( hostname );
	if ( !hostinfo ) { perror( "gethostbyname" ); exit(1); }
	// append station's IP-address to its hardware address 
	memcpy( netaddr+6, hostinfo->h_addr_list[0], 4 );

	// show the station's hostname and network addresses	
	printf( "\n\tstation-hostname: %s ", hostname );
	printf( "\n\tprotocol-address: " );
	for (int i = 0; i < 4; i++)
		{
		char	ch = ( i < 3 ) ? '.' : ' ';
		printf( "%d%c", netaddr[ 6+i ], ch );
		}
	printf( "\n\thardware-address: " );
	for (int i = 0; i < 6; i++)
		{
		char	ch = ( i < 5 ) ? ':' : ' ';
		printf( "%02X%c", netaddr[ i ], ch );
		}
	printf( "\n\n" );
	fflush( stdout );

	// fork a child-process to transmit ARP requests
	int	pid = fork();
	if ( pid == 0 )
		{
		char	message[ BUF_SIZE ] = {0};
		char	typelen[2] = { 0x08, 0x06 };
		char	htype[2] = { 0x00, 0x01 };
		char	ptype[2] = { 0x08, 0x00 };
		char	hlen[1] = { 0x06 }, plen[1] = { 0x04 };
		char	arpq[2] = { 0x00, 0x01 };
		char	askaddr[ 10 ] = { 0 };

		// initialize the 'askaddr[]' array
		memcpy( askaddr+6, netaddr+6, 4 );

		// setup the ethernet packet-header
		memset( message+0, 0xFF, 6 );		// dest'n-address
		memcpy( message+6, netaddr, 6 );	// source-address
		memcpy( message+12, typelen, 2 );	// type/length
	
		// setup the ARP packet-contents
		memcpy( message+14, htype, 2 );		// hardware-type
		memcpy( message+16, ptype, 2 );		// protocol-type
		memcpy( message+18, hlen, 1 );		// hw address-len
		memcpy( message+19, plen, 1 );		// IP address-len
		memcpy( message+20, arpq, 2 );		// ARP-request
		memcpy( message+22, netaddr, 10 );	// source net-addr
		memcpy( message+32, askaddr, 10 );	// dest'n IP-addr

		for (int n = 1; n < 255; n++)
			{
			message[41] = n;	// adjust IP-dest'n

			// transmit the ARP request
			int	nbytes = write( fd, message, BUF_SIZE );
			if ( nbytes < 0 ) { perror( "write" ); exit(1); }

		
			for (int i = 0; i < 42; i++) 
				{
				if ( ( i % 14 ) == 0 ) printf( "\n" );
				printf( "%02X ", (unsigned char)message[i] );
				}
			printf( "\n" );
			fflush( stdout );
			}		
		sleep( 1 );
		kill( getppid(), SIGINT );
		exit( 0 );		
		}

	// parent-process receives the ARP responses
	char	reply[ BUF_SIZE ] = {0};
	signal( SIGINT, upon_signal );
	while ( !done )
		{
		int	nbytes = read( fd, reply, BUF_SIZE );
		if ( nbytes < 0 ) { perror( "read" ); exit(1); }

		unsigned short	*wp = (unsigned short*)reply;
		if (( wp[6] == 0x0608 )&&( wp[10] == 0x0200 )
			&&( memcmp( reply+38, netaddr+6, 4 ) == 0 ))
			{
			for (int i = 0; i < 42; i++) 
				{
				if ( ( i % 14 ) == 0 ) printf( "\n\t" );
				printf( "%02X ", (unsigned char)reply[i] );
				}
			printf( "\n\n" );
			fflush( stdout );
			}
		}
	printf( "\nFinished\n\n" );
}