//-------------------------------------------------------------------
//	nicasync.cpp
//
//	This demo illustrates the use of asynchronous notification 
//	to process packets received by the RealTek 8139 interface.
//	It relies upon a new version of our RealTek device-driver,
//	named 'nicasync.c', which implements the necessary support
//	for the asynchronous notification capability, as discussed
//	in the "Linux Device Drivers (3rd Ed)" book, in Chapter 6.  
//	You can run our 'trychat.cpp' program from another station
//	on the local network in order to test this demo.
//
//	       compile with: $ g++ nicasync.cpp -o nicasync
//
//	programmer: ALLAN CRUSE
//	written on: 27 APR 2005
//	revised on: 29 APR 2005 -- added transmit for keyboard-input
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), write(), close() 
#include <string.h>	// for strlen()
#include <signal.h>	// for sigaction()
#include <termios.h>	// for tcgetattr(), tcsetattr()
#include <sys/ioctl.h>	// for ioctl()
#include <sys/fcntl.h>	// for fcntl()
#include <sys/wait.h>	// for wait()
#include <sys/poll.h>	// for POLL_IN 
#include <netinet/in.h>	// for htons()

#define CHAT_ID 0x0635	// identifies our packet-protocol

int kbd, nic, done = 0;
unsigned char nicaddr[6];
char devname[] = "/dev/nic";


void my_sigaction( int signo, siginfo_t *info, void *data )
{
	// function prototypes
	void handle_nic_input( int nic );
	void handle_kbd_input( int kbd, int nic );

	if ( signo == SIGINT ) done = 1;  // <CONTROL>-C pressed
	if ( signo != SIGUSR1 ) return;	  // only handle SIGUSR1

	// ignore notifications of network-packet transmissions
	if ( (info->si_band & POLL_IN) == 0 ) return;

	// process input now available on the signaling device
	else if ( info->si_fd == kbd ) handle_kbd_input( kbd, nic );
	else if ( info->si_fd == nic ) handle_nic_input( nic );
}


int main( void )
{
	// open network device-file and get its hardware-address
	nic = open( devname, O_RDWR ); 
	if ( nic < 0 ) { perror( devname ); exit(1); }
	if ( ioctl( nic, 0, &nicaddr ) < 0 ) { perror( "ioctl" ); exit(1); }

	// install our signal-handler
	struct sigaction	oa, sa = {0};
	sigemptyset( &sa.sa_mask );	// no blocked signals
	sa.sa_flags = SA_SIGINFO;	// provide extra info	
	sa.sa_sigaction = my_sigaction;	// our signal-handler
	sigaction( SIGUSR1, &sa, &oa );	// for SIGUSR1 events
	sigaction( SIGINT, &sa, NULL );	// (and for <CTRL>-C)

	// enable noncanonical input-mode at the terminal
	kbd = STDIN_FILENO;
	struct termios	orig_term;
	tcgetattr( kbd, &orig_term );
	struct termios	work_term = orig_term; 
	work_term.c_lflag &= ~( ICANON | ECHO );
	work_term.c_cc[ VMIN ] = 1;
	work_term.c_cc[ VTIME ] = 0;
	tcsetattr( kbd, TCSAFLUSH, &work_term );

	// enable asynchronous notification for the terminal device
	fcntl( kbd, F_SETOWN, getpid() );
	fcntl( kbd, F_SETSIG, SIGUSR1 );
	fcntl( kbd, F_SETFL, fcntl( kbd, F_GETFL )|FASYNC );

	// enable asynchronous notification for the network interface
	fcntl( nic, F_SETOWN, getpid() );
	fcntl( nic, F_SETSIG, SIGUSR1 );
	fcntl( nic, F_SETFL, fcntl( nic, F_GETFL )|FASYNC );

	// main loop to await <CONTROL>-C or <ESCAPE> typed by user
	while ( !done ) pause();

	// restore the original input-mode for the terminal
	tcsetattr( kbd, TCSAFLUSH, &orig_term );

	// restore the original signal-handler for SIGUSR1
	sigaction( SIGUSR1, &oa, NULL );

	// close the device-file and terminate this program
	close( nic );
	printf( "\n" );
	exit( 0 );
}






void handle_nic_input( int nic )
{
	// read the new data from the network device
	unsigned char	msg[ 1536 ] = {0};	
	int 	nbytes = read( nic, msg, sizeof( msg ) );
	if ( nbytes < 0 ) return; 

	// if it's a 'netchat' packet, then display its character
	if ( *(short*)(msg+12) == htons( CHAT_ID ) ) 
		{
		nbytes = *(short*)(msg+14);
		write( STDOUT_FILENO, msg+16, nbytes );
		}
}


void handle_kbd_input( int kbd, int nic )
{
	// read the new data from the keyboard
	unsigned char	inch[ 64 ] = {0};
	int	nbytes = read( kbd, inch, sizeof( inch ) );
	if ( nbytes < 0 ) return;

	// set 'done' for <ESC>-key; otherwise echo input to screen
	if ( *(int*)inch == '\e' ) done = 1;	
	else	write( STDOUT_FILENO, inch, nbytes );
	
	// also transmit the keyboard-input in a protocol frame
	memcpy( inch+16, inch, nbytes );	// keyboard data
	*(short*)(inch+14) = nbytes;		// data's length
	*(short*)(inch+12) = htons( CHAT_ID );	// protocol-type
	memcpy( inch+6, nicaddr, 6 );		// source-address
	memset( inch+0, 0xFF, 6 );		// dest'n-address
	write( nic, inch, sizeof( inch ) );	// xmit the frame
}