请问怎么在sequence使用prefer_ipv4

[basicallynewbie]

为了用clash透明代理把ipv6关了，所以mosdns不可以回复ipv6地址给任何主机。wiki我看过了，完全看不懂。请问prefer_ipv4是在sequence只需要使用一次，然后forward返回的就是ipv4了吗，还是要在每个forward后都要用一次。
麻烦看下东拼西凑加上自己修改过的设置，我自己看怎么都有点别扭，请各位各位大佬赐教。

log:
  level: info
  file: "/etc/mosdns/log"
  production: true

api:
  http: "127.0.0.1:8080"

plugins:
  - tag: host
    type: hosts
    args:
      files:
        - "/etc/mosdns/rule/hosts.txt"

  - tag: blocklist
    type: domain_set
    args:
      files:
        - "/etc/mosdns/rule/blocklist.txt"

  - tag: whitelist
    type: domain_set
    args:
      files:
        - "/etc/mosdns/rule/whitelist.txt"

  - tag: greylist
    type: domain_set
    args:
      files:
        - "/etc/mosdns/rule/greylist.txt"

  - tag: cn_domain
    type: domain_set
    args:
      files:
        - "/etc/mosdns/geo/geosite_cn.txt"

  - tag: cn_ip
    type: ip_set
    args:
      files:
        - "/etc/mosdns/geo/geoip_cn.txt"

  - tag: outsite_domain
    type: domain_set
    args:
      files:
        - "/etc/mosdns/geo/geolocation-no-cn.txt"

  - tag: gfw_domain
    type: domain_set
    args:
      files:
        - "/etc/mosdns/rule/gfw.txt"

  - tag: dx_dns
    type: forward
    args:
      concurrent: 2
      upstreams:
        - tag: dx1
          addr: "udp://218.85.157.99"
        - tag: dx2
          addr: "udp://218.85.152.99"

  - tag: cn_dns
    type: forward
    args:
      concurrent: 2
      upstreams:
        - tag: ali
          addr: "udp://223.5.5.5"
        - tag: dnspod
          addr: "udp://119.29.29.29"

  - tag: resolve_cn
    type: sequence
    args:
      - exec: $dx_dns
      - matches: has_resp
        exec: accept
      - exec: $cn_dns
      - matches: has_resp
        exec: accept

  - tag: cn_4_udp_server
    type: udp_server
    args:
      entry: resolve_cn
      listen: :3453

  - tag: cn_4_tcp_server
    type: tcp_server
    args:
      entry: resolve_cn
      listen: :3453

  - tag: doh_dns
    type: forward
    args:
      concurrent: 2
      upstreams:
        - tag: cloudflare
          addr: "https://dns.cloudflare.com/dns-query"
          dial_addr: "1.1.1.1"
        - tag: controld
          addr: "https://freedns.controld.com/p2"
          dial_addr: "76.76.2.2"

  - tag: lazy_cache
    type: cache
    args:
      size: 20000
      lazy_cache_ttl: 3600

  - tag: resolve_doh
    type: sequence
    args:
      - exec: $lazy_cache
      - matches: has_resp
        exec: accept
      - exec: $doh_dns
      - matches: has_resp
        exec: accept

  - tag: doh_4_udp_server
    type: udp_server
    args:
      entry: resolve_doh
      listen: :4453

  - tag: doh_4_tcp_server
    type: tcp_server
    args:
      entry: resolve_doh
      listen: :4453

  - tag: openclash
    type: forward
    args:
      concurrent: 1
      upstreams:
        - tag: clash
          addr: "udp://192.168.0.3"

  - tag: resolve_gfw
    type: sequence
    args:
      - exec: $openclash
      - matches: has_resp
        exec: accept

  - tag: gfw_udp_server
    type: udp_server
    args:
      entry: resolve_gfw
      listen: :5553

  - tag: gfw_tcp_server
    type: tcp_server
    args:
      entry: resolve_gfw
      listen: :5553

  - tag: main_sequence
    type: sequence
    args:
      - exec: $host
      - matches: has_resp
        exec: accept

      - matches: 
        - qname $blocklist
        exec: reject 3

      - matches: 
        - qname $whitelist
        exec: $resolve_cn
      - exec: prefer_ipv4
      - matches: has_wanted_ans
        exec: accept

      - matches: qname $greylist
        exec: $resolve_doh
      - exec: prefer_ipv4
      - matches: has_wanted_ans
        exec: accept

      - matches: 
        - qname $cn_domain
        exec: $resolve_cn
      - exec: prefer_ipv4
      - matches: has_wanted_ans
        exec: accept

      - matches: 
        - resp_ip $cn_ip
        exec: $resolve_cn
      - exec: prefer_ipv4
      - matches: has_wanted_ans
        exec: accept

      - matches: 
        - qname $gfw_domain
        exec: $resolve_gfw
      - matches: has_resp
        exec: accept

      - matches: 
        - qname $outsite_domain
        exec: $resolve_gfw
      - matches: has_resp
        exec: accept

      - exec: $resolve_cn
      - exec: prefer_ipv4
      - matches: has_wanted_ans
        exec: accept

      - exec: $resolve_doh
      - exec: prefer_ipv4
      - matches: has_wanted_ans
        exec: accept

      - exec: $resolve_gfw

  - tag: udp_server
    type: udp_server
    args:
      entry: main_sequence
      listen: :53

  - tag: tcp_server
    type: tcp_server
    args:
      entry: main_sequence
      listen: :53