docker-compose.yml 里加入这一条:

extra_hosts:
  - "host.docker.internal:host-gateway"


变成:
services:
  app:
    image: ...
    container_name: ...
    ...
    extra_hosts:
      - "host.docker.internal:host-gateway"


与此同时, MySQL 需要监听在 docker 的网卡上:


# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq state UP group default qlen 1000
    link/ether 00:0c:ff:cc:af:af brd ff:ff:ff:ff:ff:ff
    altname enp0s18
    altname ens18
    inet 172.16.212.135/24 brd 172.16.212.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80:20c:29ff:3::bca/64 scope global
       valid_lft forever preferred_lft forever
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
    link/ether 76:1f:8c:eb:62:f8 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
       valid_lft forever preferred_lft forever
25: br-c5516318dfee: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
    link/ether 7e:e9:0e:61:6e:cb brd ff:ff:ff:ff:ff:ff
    inet 172.18.0.1/16 brd 172.18.255.255 scope global br-c5516318dfee
       valid_lft forever preferred_lft forever
    inet6 fe80::7ce9:eff:fe61:6ecb/64 scope link
       valid_lft forever preferred_lft forever


这里可以看到 docker0 网卡的地址是 172.17.0.1, 也就是容器内 host.docker.internal 会解析到的地址


打开 MySQL 配置文件, 位于:
/etc/mysql/mysql.conf.d/mysqld.cnf


将
bind-address            = 127.0.0.1
改为
bind-address            = 127.0.0.1,172.17.0.1
重启 MySQL:
systemctl restart mysql
即可完成配置