PF_PT_COUNTER
snl_add_msg_attr_ip6(nw, PF_PT_COUNTER, &pool->counter.v6);
{ .type = PF_PT_COUNTER, .off = _OUT(counter), .cb = snl_attr_get_in6_addr },
{ .type = PF_PT_COUNTER, .off = _OUT(counter), .cb = nlattr_get_in6_addr },
nlattr_add_in6_addr(nw, PF_PT_COUNTER, (const struct in6_addr *)&pool->counter);