LXR linux/net/netfilter/xt

   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})
  36