netmap_obj_malloc
#define netmap_if_malloc(n, len) netmap_obj_malloc(&(n)->pools[NETMAP_IF_POOL], len, NULL, NULL)
#define netmap_ring_malloc(n, len) netmap_obj_malloc(&(n)->pools[NETMAP_RING_POOL], len, NULL, NULL)
netmap_obj_malloc(&(n)->pools[NETMAP_BUF_POOL], netmap_mem_bufsize(n), _pos, _index)