CTA_LABELS_MASK
[CTA_LABELS_MASK] = { .type = NLA_BINARY,
const void *mask = cda[CTA_LABELS_MASK];
if (nla_len(cda[CTA_LABELS_MASK]) == 0 ||
nla_len(cda[CTA_LABELS_MASK]) != len)
mask = nla_data(cda[CTA_LABELS_MASK]);