get_ncm
block_len = get_ncm(&tmp, opts->block_length);
ndp_index = get_ncm(&tmp, opts->ndp_index);
ndp_index = get_ncm(&tmp, opts->next_ndp_index);
index2 = get_ncm(&tmp, opts->dgram_item_len);
dg_len2 = get_ncm(&tmp, opts->dgram_item_len);
index2 = get_ncm(&tmp, opts->dgram_item_len);
dg_len2 = get_ncm(&tmp, opts->dgram_item_len);