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安装：

apt install php7.2-dev libleveldb-dev
git clone https://github.com/reeze/php-leveldb.git
cd php-leveldb/
phpize
./configure 
#arm64
#./configure --with-leveldb=/usr/lib/aarch64-linux-gnu/ 
make && make install
echo 'extension=leveldb.so' > /etc/php/7.2/cli/conf.d/40-leveldb.ini

查看是否加载：

php -m|grep leveldb

将所有的ipv6地址设置为private-address，这样unbound转发域名有ipv6结果时不返回给查询的客户端。
如果对单独的域名进行过滤新建一个server实例，然后forward-zone转发特定域名到过滤ipv6的端口。

server:
 port: 5350
 do-ip4: yes
 do-ip6: no 
 private-address: ::/0
 interface: 0.0.0.0
 access-control: 127.0.0.0/8 allow
 access-control: 192.168.0.0/16 allow
 msg-cache-size: 4m
 rrset-cache-size: 4m
 cache-max-ttl: 3600
 cache-min-ttl: 300
 hide-identity: yes
 hide-version: yes
 prefetch: yes
 num-threads: 4
 do-not-query-localhost: no
#minimal-responses: yes
#qname-minimisation: yes
#tcp-upstream: yes
#verbosity: 1
#logfile: "/var/log/unbound.log"

forward-zone:
  name: "."
  forward-addr: 114.114.114.114

prefetch当查询时且缓存离过期时间还有10%时预请求并更新dns缓存，如果期间无查询请求不更新。
参考：
https://lost-and-found-narihiro.blogspot.com/2011/10/unbound-prefetch.html
https://nlnetlabs.nl/pipermail/unbound-users/2018-January/010444.html
https://calomel.org/unbound_dns.html
https://nlnetlabs.nl/documentation/unbound/unbound.conf/
https://www.nlnetlabs.nl/svn/unbound/trunk/doc/example.conf.in

类似于linux下设置ipv4优先，将::ffff:0:0/96的优先级调高即可。
查看优先级顺序：

netsh interface ipv6 show prefixpolicies

修改优先级：

netsh interface ipv6 set prefixpolicy ::ffff:0:0/96 100 4

查看修改后的优先级：

更新：此方法有问题，重启电脑后ipv6优先级不正常，暂不使用。
参考：
http://blog.ilc.edu.tw/blog/index.php?op=printView&articleId=622435&blogId=25793