@@ -0,0 +1,134 @@
/*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*/
#include <arpa/inet.h>
#include <linux/if_packet.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/ether.h>
#define DEST_MAC0 0x00
#define DEST_MAC1 0x00
#define DEST_MAC2 0x00
#define DEST_MAC3 0x00
#define DEST_MAC4 0x00
#define DEST_MAC5 0x00
#define ETHER_TYPE 0x0800
#define DEFAULT_IF "eth0"
#define BUF_SIZ 1024
int main (int argc , char * argv [])
{
char sender [INET6_ADDRSTRLEN ];
int sockfd , ret , i ;
int sockopt ;
ssize_t numbytes ;
struct ifreq ifopts ; /* set promiscuous mode */
struct ifreq if_ip ; /* get ip addr */
struct sockaddr_storage their_addr ;
uint8_t buf [BUF_SIZ ];
char ifName [IFNAMSIZ ];
/* Get interface name */
if (argc > 1 )
strcpy (ifName , argv [1 ]);
else
strcpy (ifName , DEFAULT_IF );
/* Header structures */
struct ether_header * eh = (struct ether_header * ) buf ;
struct iphdr * iph = (struct iphdr * ) (buf + sizeof (struct ether_header ));
struct udphdr * udph = (struct udphdr * ) (buf + sizeof (struct iphdr ) + sizeof (struct ether_header ));
memset (& if_ip , 0 , sizeof (struct ifreq ));
/* Open PF_PACKET socket, listening for EtherType ETHER_TYPE */
if ((sockfd = socket (PF_PACKET , SOCK_RAW , htons (ETHER_TYPE ))) == -1 ) {
perror ("listener: socket" );
return -1 ;
}
/* Set MUX to promiscuous mode - do we need to do this every time? */
strncpy (ifopts .ifr_name , ifName , IFNAMSIZ - 1 );
ioctl (sockfd , SIOCGIFFLAGS , & ifopts );
ifopts .ifr_flags |= IFF_PROMISC ;
ioctl (sockfd , SIOCSIFFLAGS , & ifopts );
/* Allow the socket to be reused - incase connection is closed prematurely */
if (setsockopt (sockfd , SOL_SOCKET , SO_REUSEADDR , & sockopt , sizeof sockopt ) == -1 ) {
perror ("setsockopt" );
close (sockfd );
exit (EXIT_FAILURE );
}
/* Bind to device */
if (setsockopt (sockfd , SOL_SOCKET , SO_BINDTODEVICE , ifName , IFNAMSIZ - 1 ) == -1 ) {
perror ("SO_BINDTODEVICE" );
close (sockfd );
exit (EXIT_FAILURE );
}
repeat : printf ("listener: Waiting to recvfrom...\n" );
numbytes = recvfrom (sockfd , buf , BUF_SIZ , 0 , NULL , NULL );
printf ("listener: got packet %lu bytes\n" , numbytes );
/* Check the packet is for me */
if (eh -> ether_dhost [0 ] == DEST_MAC0 &&
eh -> ether_dhost [1 ] == DEST_MAC1 &&
eh -> ether_dhost [2 ] == DEST_MAC2 &&
eh -> ether_dhost [3 ] == DEST_MAC3 &&
eh -> ether_dhost [4 ] == DEST_MAC4 &&
eh -> ether_dhost [5 ] == DEST_MAC5 ) {
printf ("Correct destination MAC address\n" );
} else {
printf ("Wrong destination MAC: %x:%x:%x:%x:%x:%x\n" ,
eh -> ether_dhost [0 ],
eh -> ether_dhost [1 ],
eh -> ether_dhost [2 ],
eh -> ether_dhost [3 ],
eh -> ether_dhost [4 ],
eh -> ether_dhost [5 ]);
ret = -1 ;
goto done ;
}
/* Get source IP */
((struct sockaddr_in * )& their_addr )-> sin_addr .s_addr = iph -> saddr ;
inet_ntop (AF_INET , & ((struct sockaddr_in * )& their_addr )-> sin_addr , sender , sizeof sender );
/* Look up my device IP addr if possible */
strncpy (if_ip .ifr_name , ifName , IFNAMSIZ - 1 );
if (ioctl (sockfd , SIOCGIFADDR , & if_ip ) >= 0 ) { /* if we can't check then don't */
printf ("Source IP: %s\n My IP: %s\n" , sender ,
inet_ntoa (((struct sockaddr_in * )& if_ip .ifr_addr )-> sin_addr ));
/* ignore if I sent it */
if (strcmp (sender , inet_ntoa (((struct sockaddr_in * )& if_ip .ifr_addr )-> sin_addr )) == 0 ) {
printf ("but I sent it :(\n" );
ret = -1 ;
goto done ;
}
}
/* UDP payload length */
ret = ntohs (udph -> len ) - sizeof (struct udphdr );
/* Print packet */
printf ("\tData:" );
for (i = 0 ; i < numbytes ; i ++ ) printf ("%02x:" , buf [i ]);
printf ("\n" );
done : goto repeat ;
close (sockfd );
return ret ;
}
austinmarton revised this gist