nginx防止域名恶意解析，就是要关闭默认站点：
server{
listen 80 default_server;
listen 443 ssl default_server；
listen [::]:80 default_server;
listen [::]:443 ssl default_server;
server_name _;
ssl_certificate /usr/share/nginx/a.pem;
ssl_certificate_key /usr/share/nginx/a.key;
return 444;
}
