//-------------------------------------------------------------------
//	bindtoif.cpp
//
//	This program attempts to use the 'SO_BINDTODEVICE' socket
//	option provided by Linux, as well as the SO_BROADCAST and
//	INADDR_BROADCAST socket option and network address, so it
//	can transmit a message to all of the stations on our LAN.   
//	(Evidently root privileges are needed for these options.)
//
//	     to compile:  root# g++ bindtoif.cpp -o bindtoif
//	     to execute:  root# ./bindtoif <interface>
//
//	programmer: ALLAN CRUSE
//	written on: 05 FEB 2009
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for write() 
#include <string.h>	// for strncpy()
#include <netinet/in.h>	// for htons(), 
#include <net/if.h>	// for IFNAMSIZ

int main( int argc, char **argv )
{
	char	ifname[ IFNAMSIZ ] = {0};
	if ( argc == 1 ) strcpy( ifname, "lo" );
	else	strncpy( ifname, argv[ 1 ], IFNAMSIZ-1 );

	int	sock = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
	if ( sock < 0 ) { perror( "socket" ); exit(1); } 

	int	oval = 1;
	int	olen = sizeof( oval );
	if ( setsockopt( sock, SOL_SOCKET, SO_BROADCAST, &oval, olen ) < 0 )
		{ perror( "setsockopt broadcast" ); exit(1); }
		
	if ( setsockopt( sock, SOL_SOCKET, SO_BINDTODEVICE, 
			&ifname, IFNAMSIZ ) < 0 )
		{ perror( "setsockopt bindtodevice" ); exit(1); }

	struct sockaddr_in	saddr;
	socklen_t		salen = sizeof( saddr );
	bzero( &saddr, salen );
	saddr.sin_family = AF_INET;
	saddr.sin_port = htons( 0 );
	saddr.sin_addr.s_addr = htonl( INADDR_BROADCAST );
	if ( connect( sock, (sockaddr*)&saddr, salen ) < 0 )
		{ perror( "connect" ); exit(1); }

	char	msg[ 64 ] = "This is our moment, this is our time... \n";
	int	len = sizeof( msg );
	int	tx = write( sock, msg, len );
	if ( tx < 0 ) { perror( "write" ); exit(1); }

	printf( "wrote %d bytes to interface \'%s\' \n", tx, ifname );
}