/* 
 * BPF receiver
 */

#include <sys/socket.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <net/bpf.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <errno.h>
#include <sys/select.h>

#define MY_ETHERTYPE   0x9999            // Ethertype of my ethernetframe 

/* this filter checks for 0x9999 in the ethernet type field */
 struct bpf_insn my_filter[] =
    {
      BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 12),
      BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, MY_ETHERTYPE, 0, 1),
      BPF_STMT (BPF_RET+BPF_K, (u_int) -1),
      BPF_STMT (BPF_RET+BPF_K, 0),
    };

  struct bpf_program filter =
    {
      sizeof (my_filter) / sizeof (struct bpf_insn),
      my_filter
    };



int main(int argc, char *argv[]) {

  int PktLen, fd, BytesRead;
  int i, ret,select_return;
  const int set=1; 
  struct ifreq ifr;
  char ifname[]="en0";
  fd_set fdset;
  char buf[2048]={};
  
  memset(buf,0,2048);

  if (( fd = open("/dev/bpf0", O_RDONLY, 0)) < 0)
  {
          perror("open");
          exit(EXIT_FAILURE);
  }

 strcpy (ifr.ifr_name, ifname);
 
  printf("device name set to %s\n",ifr.ifr_name);

    /*  BPF buffer . */
  if (ioctl_socket (fd, BIOCSBLEN, &PktLen) < 0)
  {
   perror("ioctl_socket BIOCSBLEN"); // this is all for errror checking 
  }
    /* Set interface. */
  if (ioctl_socket (fd, BIOCSETIF,  &ifr) < 0)
  {
      perror("ioctl_socket BIOCSETIF ");
  }

    /* Read  buffer immediately. */
  if (ioctl_socket (fd, BIOCIMMEDIATE, &set) < 0)
  {
      perror("ioctl_socket  BIOCIMMEDIATE ");
  } 

          /*  filter. */
  if (ioctl_socket (fd, BIOCSETF, (caddr_t) &filter) < 0)
  {
      perror("ioctl_socket BIOCSETF ");
  }


 printf(" the bfd fd is %d",fd);

 /* setting  up the select*/
 FD_ZERO( &fdset);
 FD_SET( fd, &fdset);

 if((select_return = select( (1+fd), &fdset, NULL , NULL , NULL) ))
  {

      perror("Select ");
      printf("\n select return %d\n", select_return);

      /* check if the socket is set */
      if( (FD_ISSET(fd, &fdset) )) 
      {
	  printf("\n reading from bfp device socket is set \n");	
          if ((BytesRead = read(fd, buf, PktLen)) < 0)
          {
                  perror("read");
                  exit(EXIT_FAILURE);
          }
          printf("%d returned from read, errno = %d..\n", BytesRead, errno);
       } 
  }     

  close(fd);

  return EXIT_SUCCESS;
}