#!/usr/sbin/dtrace -qs

fbt:ipf:ipf_hook_out:entry {
   self->watch=1;
   self->token=arg0;
   self->data=arg1;
}

fbt:ipf:ipf_hook_out:return 
/ self->watch == 1 && arg1 != 0 / {
  printf("Problem with data in filter rule from %s %x\n",execname,self->data);
  printf("user stack\n");
  ustack();
  self->watch=0;
}