其实用代理是可以知道你的ip的
这个是RAILS帮助文档的一段
Determine originating IP address. REMOTE_ADDR is the standard but will fail if the user is behind a proxy. HTTP_CLIENT_IP and/or HTTP_X_FORWARDED_FOR are set by proxies so check for these before falling back to REMOTE_ADDR. HTTP_X_FORWARDED_FOR may be a comma- delimited list in the case of multiple chained proxies; the first is the originating IP.