//-------------------------------------------------------------------
//	vwnetdev.cpp
//
//	This application shows the current contents of the kernel's 
//	'struct net_device' object for a specified interface if the
//	interface's name is entered as a command-line argument.  It
//	demonstrates the feasibility of a programming technique for
//	extracting and displaying a data-structure in kernel space.
//
//	     compile using:  $ g++ vwnetdev.cpp -o vwnetdev
//	     execute using:  $ ./vwnetdev <ifname>
//
//	NOTE: The files named 'dram.ko' and 'netdevs.ko' have to be 
//	located in a user's current working directory.
//
//	programmer: ALLAN CRUSE
//	written on: 25 JAN 2008
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), close() 
#include <string.h>	// for strstr(), strchr()

char dramname[] = "/dev/dram";		// name of device-file
char procname[] = "/proc/netdevs";	// name of pseudo-file
char hostname[ 64 ];			// buffer for hostname
char buffer[ 4096 ];			// multiple-use buffer

int main( int argc, char **argv )
{
	// check for required command-line argument
	if ( argc == 1 ) 
		{ fprintf( stderr, "interface was unspecified\n" ); exit(1); }

	// get this station's hostname for use in output message
	gethostname( hostname, sizeof( hostname ) - 1 );

	// install the kernel module that creates our pseudo-file
	system( "/sbin/insmod netdevs.ko" );

	// open that pseudo-file for reading 
	int	proc = open( procname, O_RDONLY );
	if ( proc < 0 ) { perror( procname ); exit(1); }

	// read the contents of the pseudo-file
	int	nbytes = read( proc, buffer, sizeof( buffer ) );
	if ( nbytes < 0 ) { perror( "read" ); exit(1); }

	// close the pseudo-file and remove the kernel-module
	close( proc );
	system( "/sbin/rmmod netdevs" );

	// exhibit the pseudo-file's contents
	printf( "%s", buffer );

	// search file's contents for the specified interface-name 
	char	*ifp = strstr( buffer, argv[1] );
	if ( !ifp ) 
		{ fprintf( stderr, "interface name not found\n" ); exit(1); }

	// search for the size of a 'task_struct' object
	char	*szp = strstr( buffer, "sizeof" );
	szp = strchr( szp, '=' );
	unsigned long	sbytes = strtoul( szp+1, NULL, 10 );
	// printf( " size of \'net_device\' is %u bytes \n", sbytes );

	// split the pseudo-file's contents into lines
	char	*line = strtok( buffer, "\n" );
	while ( !strstr( line, argv[1] ) ) line = strtok( NULL, "\n" );
	// printf( " found: %s\n", line );
	
	// extract the physical-address of the 'net_device' structure
	char	*ifa = strstr( line, "0x" );
	unsigned long	ifaddr = strtoul( ifa+2, NULL, 16 );
	// printf( "physical address of structure is %08lX \n", ifaddr );	

	// read the 'net_device' structure from physical memory
	system( "/sbin/insmod dram.ko" );
	int	dram = open( dramname, O_RDONLY );
	if ( dram < 0 ) { perror( dramname ); exit(1); }
	lseek( dram, ifaddr, SEEK_SET );
	nbytes = read( dram, buffer, sbytes );
	if ( nbytes < 0 ) { perror( "read" ); exit(1); }
	close( dram );
	system( "/sbin/rmmod dram" );

	// display the 'net_device' object in hex and ascii formats
	printf( "\n Contents of the \'%s\' net_device object " );
	printf( "on station \'%s\': \n", hostname );
	unsigned int 	*ip = (unsigned int*)buffer; // <-- changed 1/29/2008
	for (int i = 0; i < sbytes; i+=16)
		{
		printf( "\n 0x%08X (0x%03X): ", ifaddr + i, i );
		for (int j = 0; j < 16; j+=4) 
			{
			if ( i+j < sbytes ) 
				printf( "%08X ", ip[ (i+j)/4 ] );
			else 	printf( "9s", " " );
			}
		for (int j = 0; j < 16; j++)
			{
			unsigned char	ch;
			ch = ( i+j < sbytes ) ? buffer[ i+j ] : ' ';
			if (( ch < 0x20 )||( ch > 0x7E )) ch = '.';
			printf( "%c", ch );
			}
		}
	printf( "\n\n" );
}