net/netfilter/xt_repldata.h

   1 /*
   2  * Today's hack: quantum tunneling in structs
   3  *
   4  * 'entries' and 'term' are never anywhere referenced by word in code. In fact,
   5  * they serve as the hanging-off data accessed through repl.data[].
   6  */
   7
   8 #define xt_alloc_initial_table(type, typ2) ({ \
   9         unsigned int hook_mask = info->valid_hooks; \
  10         unsigned int nhooks = hweight32(hook_mask); \
  11         unsigned int bytes = 0, hooknum = 0, i = 0; \
  12         struct { \
  13                 struct type##_replace repl; \
  14                 struct type##_standard entries[nhooks]; \
  15                 struct type##_error term; \
  16         } *tbl = kzalloc(sizeof(*tbl), GFP_KERNEL); \
  17         if (tbl == NULL) \
  18                 return NULL; \
  19         strncpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \
  20         tbl->term = (struct type##_error)typ2##_ERROR_INIT;  \
  21         tbl->repl.valid_hooks = hook_mask; \
  22         tbl->repl.num_entries = nhooks + 1; \
  23         tbl->repl.size = nhooks * sizeof(struct type##_standard) + \
  24                          sizeof(struct type##_error); \
  25         for (; hook_mask != 0; hook_mask >>= 1, ++hooknum) { \
  26                 if (!(hook_mask & 1)) \
  27                         continue; \
  28                 tbl->repl.hook_entry[hooknum] = bytes; \
  29                 tbl->repl.underflow[hooknum]  = bytes; \
  30                 tbl->entries[i++] = (struct type##_standard) \
  31                         typ2##_STANDARD_INIT(NF_ACCEPT); \
  32                 bytes += sizeof(struct type##_standard); \
  33         } \
  34         tbl; \
  35 })