/* 
 * 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>

char buf[2048];


#define MY_ETHERTYPE   0x9999            // Ethertype of my ethernetframe 


                                         // Filter to accept my ethernet frame (ethertype = 0x9999)         
struct bpf_insn insns[] = {                       
BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 12),
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, MY_ETHERTYPE, 0, 1),
BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 20),
BPF_STMT(BPF_RET+BPF_K, 0),
};



int main(int argc, char *argv[]) {
  int iPktLen, iHdl, iBytesRead;
  int i, ret;
  const int ciImmediate=1; //To enable BIOCIMMEDIATE mode
  struct ifreq stIfr;
  
  struct bpf_program my_bpf_program;
  my_bpf_program.bf_len = sizeof(insns);
  my_bpf_program.bf_insns = &insns;
  
  
  int iPacketsRead=0;

  memset(buf,0,2048);
  if (snprintf(stIfr.ifr_name, IFNAMSIZ, "en0") != 3)
  {
          perror("snprintf");
          exit(EXIT_FAILURE);
  }

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

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

  printf("bpf /dev/bpf0 opened\n");

  if (ioctl(iHdl, BIOCGBLEN, &iPktLen) < 0)
  {
          perror("ioctl BICGBLEN");
          exit(EXIT_FAILURE);
  }

  if (ioctl(iHdl, BIOCSETIF, &stIfr) < 0)
  {
          perror("ioctl BIOCSETIF");
          exit(EXIT_FAILURE);
  }
  printf("filter bound to network device %s\n",stIfr.ifr_name);

  if( ioctl(iHdl, BIOCIMMEDIATE, &ciImmediate ) == -1 )
  {
          perror("ioctl BIOCIMMEDIATE");
          exit(EXIT_FAILURE);
  }

  printf("Immediate Mode set\n");
  
  if (ioctl(iHdl, BIOCSETF, &my_bpf_program) < 0)                        // Setting filter
  {
          perror("ioctl BIOCSETF");
          exit(EXIT_FAILURE);
  }
  printf("Filter program set\n");

    while (iPacketsRead++<1000) 
  {
  	      printf("\n %d. Reading from bpf device...\n", iPacketsRead);
          if ((iBytesRead = read(iHdl, buf, iPktLen)) < 0)
          {
                  perror("read");
                  exit(EXIT_FAILURE);
          }
          printf("%d returned from read, errno = %d..\n", iBytesRead, errno);
         
     

  }

  printf("Read %d packets",iPacketsRead);
  
  close(iHdl);

  return EXIT_SUCCESS;
}







/****************************************************************************************/

The output when I run bpfreceiver:

$ ./bpfreceiver
device name set to en0
bpf /dev/bpf0 opened
filter bound to network device en0
Immediate Mode set
ioctl BIOCSETF: Invalid argument                       // ERROR
$
$
$