反向代理后获取用户的直实IP

server{
     listen      4081;
     server_name localhost;
     charset  utf-8;
     access_log /usr/local/nginx1140/logs/access4081.log main buffer=32k;

     location / {
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_pass  http://SOCIAL/;
       }
    }
upstream SOCIAL{
     server 10.100.99.231:50002;
}

如果通过了多级反向代理的话，X-Forwarded-For的值并不止一个，而是一串Ｉｐ值，究竟哪个才是真正的用户端的真实IP呢？

答案是取X-Forwarded-For中第一个非unknown的有效IP字符串。如：X-Forwarded-For：192.168.1.110, 192.168.1.120, 192.168.1.130, 192.168.1.100,用户真实IP为： 192.168.1.110