import json


def collect_tokens(cfg):
    dns = cfg.get('upstream_dns', {})
    servers = dns.get('upstream_servers', [])
    return {
        'DNS_STRICT_ORDER':          'true' if dns.get('strict_order') else 'false',
        'DNS_CACHE_SIZE':            str(dns.get('cache_size', '-')),
        'DNS_UPSTREAM_SERVERS_JSON': json.dumps(servers),
    }