添加一个文件cf.conf，里面记录的是允许访问的ip

# https://www.cloudflare.com/ips
# IPv4

allow 173.245.48.0/20;
allow 103.21.244.0/22;
allow 103.22.200.0/22;
allow 103.31.4.0/22;
allow 141.101.64.0/18;
allow 108.162.192.0/18;
allow 190.93.240.0/20;
allow 188.114.96.0/20;
allow 197.234.240.0/22;
allow 198.41.128.0/17;
allow 162.158.0.0/15;
allow 104.16.0.0/12;
allow 172.64.0.0/13;
allow 131.0.72.0/22;

 # IPv6
allow 2400:cb00::/32;
allow 2606:4700::/32;
allow 2803:f800::/32;
allow 2405:b500::/32;
allow 2405:8100::/32;
allow 2a06:98c0::/29;
allow 2c0f:f248::/32;

修改 /etc/nginx/sites-available/default中的内容，添加include cf.conf和deny all

        location / {
                include /etc/nginx/cf.conf;
                deny all;

                # First attempt to serve request as file, then
                # as directory, then fall back to displaying a 404.
                try_files $uri $uri/ =404;
        }