www.xxx.com 反向代理到 www.baidu.com，并且反向cookie，遇到header location 也跳转到当前域名下，如果需要替换里面文本，也可以用nginx sub_filter 指令进行内容替换

    server {
        listen              80;
        index               index.html index.htm;
        server_name         www.xxx.com;

        location / {
            proxy_cookie_domain ~\.?baidu.com $host;

            proxy_pass https://www.baidu.com$request_uri;

            proxy_redirect ~^https://www.baidu.com(.*) http://$server_name$1;

            proxy_set_header X-Real-IP $remote_addr;

            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

            proxy_set_header Host www.baidu.com;

            resolver 8.8.8.8;
        }
    }