wifidog 源码初分析(二)

上一篇分析了接入设备的首次浏览器访问请求如何通过 防火墙过滤规则 重定向到 wifidog 的 HTTP 服务中,本篇主要分析了 wifidog 在接收到 接入设备的 HTTP 访问请求后,如何将此 HTTP 请求重定向到 认证服务器(auth-server) 上。通过上面的防火墙规则,会将通过上面的防火墙规则,会将HTTP请求的外部IP地址和端口通过NAT方式重定向至本地wifidog内嵌HTTP服务器的地址和端口上,并由内嵌HTTP服务器进行服务,而内嵌HTTP服务器的路径和回调处理如下:    if ((webserver = httpdCreate(config->gw_address, config->gw_port)) == NULL) {          debug(LOG_ERR, "Could not create web server: %s", strerror(errno));          exit(1);      }      debug(LOG_DEBUG, "Assigning callbacks to web server");      httpdAddCContent(webserver, "/", "wifidog", 0, NULL, http_callback_wifidog);      httpdAddCContent(webserver, "/wifidog", "", 0, NULL, http_callback_wifidog);      httpdAddCContent(webserver, "/wifidog", "about", 0, NULL, http_callback_about);      httpdAddCContent(webserver, "/wifidog", "status", 0, NULL, http_callback_status);      httpdAddCContent(webserver, "/wifidog", "auth", 0, NULL, http_callback_auth);      httpdAddC404Content(webserver, http_callback_404);客户端首次访问时回调客户端首次访问时回调http_callback_404函数,在该函数中根据获取的客户端信息来配置重定向的URL fragment,如下:    /** The 404 handler is also responsible for redirecting to the auth server */    void http_callback_404(httpd *webserver, request *r)    {        chartmp_url[MAX_BUF],*url;        s_config*config = config_get_config();        t_auth_serv*auth_server = get_auth_server();        memset(tmp_url, 0, sizeof(tmp_url));        /*          * XXX Note the code below assumes that the client's request is a plain        * http request to a standard port. At any rate, this handler is called only        * if the internet/auth server is down so it's not a huge loss, but still.        */        snprintf(tmp_url, (sizeof(tmp_url) - 1), "http://%s%s%s%s",                        r->request.host,                        r->request.path,                        r->request.query[0] ? "?" : "",                        r->request.query);        url = httpdUrlEncode(tmp_url);        if (!is_online()) {            /* The internet connection is down at the moment  - apologize and do not redirect anywhere */            char * buf;            safe_asprintf(&buf,                "

We apologize, but it seems that the internet connection that powers this hotspot is temporarily unavailable.

"                "

If at all possible, please notify the owners of this hotspot that the internet connection is out of service.

"                "

The maintainers of this network are aware of this disruption.  We hope that this situation will be resolved soon.

"                "

In a while pleaseclick hereto try your request again.

", tmp_url);            send_http_page(r, "Uh oh! Internet access unavailable!", buf);            free(buf);            debug(LOG_INFO, "Sent %s an apology since I am not online - no point sending them to auth server", r->clientAddr);        }        else if (!is_auth_online()) {            /* The auth server is down at the moment - apologize and do not redirect anywhere */            char * buf;            safe_asprintf(&buf,                "

We apologize, but it seems that we are currently unable to re-direct you to the login screen.

"                "

The maintainers of this network are aware of this disruption.  We hope that this situation will be resolved soon.

""

In a couple of minutes pleaseclick hereto try your request again.

", tmp_url);            send_http_page(r, "Uh oh! Login screen unavailable!", buf);            free(buf);            debug(LOG_INFO, "Sent %s an apology since auth server not online - no point sending them to auth server", r->clientAddr);        }        else {            /* Re-direct them to auth server */            char *urlFragment;            safe_asprintf(&urlFragment, "%sgw_address=%s&gw_port=%d&gw_id=%s&url=%s",                auth_server->authserv_login_script_path_fragment,            config->gw_address,                config->gw_port,                config->gw_id,                url);            debug(LOG_INFO, "Captured %s requesting [%s] and re-directing them to login page", r->clientAddr, url);            http_send_redirect_to_auth(r, urlFragment, "Redirect to login page");            free(urlFragment);        }        free(url);    }上面代码基本不用解释,具体重定向至auth server的消息在下面的 http_send_redirect_to_auth 函数中实现:    void http_send_redirect_to_auth(request *r, char *urlFragment, char *text)    {        char *protocol = NULL;        int port = 80;        t_auth_serv*auth_server = get_auth_server();        if (auth_server->authserv_use_ssl) {            protocol = "https";            port = auth_server->authserv_ssl_port;        } else {            protocol = "http";            port = auth_server->authserv_http_port;        }            char *url = NULL;        safe_asprintf(&url, "%s://%s:%d%s%s",            protocol,            auth_server->authserv_hostname,            port,            auth_server->authserv_path,            urlFragment        );        http_send_redirect(r, url, text);        free(url);    }具体的重定向URL给个实例:POST /login/?gw_address=192.168.1.1&gw_port=2060&gw_id=default&mac=44:94:fc:ef:28:40&url=http%3A//www.baidu.com/ HTTP/1.1gw_address,路由器的LAN地址gw_port:为wifidog的监听端口gw_id:路由器的标识名mac:客户端设备的MAC地址url:为客户端访问的原URL(以便于重定向)

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