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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