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上一篇分析了接入裝置的首次瀏覽器訪問請求如何通過 防火牆過濾規則 重新導向到 wifidog 的 HTTP 服務中，本篇主要分析了 wifidog 在接收到 接入裝置的 HTTP 訪問請求後，如何將此 HTTP 要求重新導向到 證明伺服器(auth-server) 上。
通過上面的防火牆規則，會將通過上面的防火牆規則，會將HTTP請求的外部IP地址和連接埠通過NAT方式重新導向至本地wifidog內嵌HTTP伺服器的地址和連接埠上，並由內嵌HTTP伺服器進行服務，而內嵌HTTP伺服器的路徑和回調處理如下：
[cpp] view plaincopy
- 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);
用戶端首次訪問時回調用戶端首次訪問時回調http_callback_404函數，在該函數中根據擷取的用戶端資訊來配置重新導向的URL fragment，如下：
[cpp] view plaincopy
- void
- http_callback_404(httpd *webserver, request *r)
- {
- char tmp_url[MAX_BUF],
- *url,
- *mac;
- 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.
- */ /* 使用者需要訪問的URL */
- 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()) {
- /* 路由器都接入不到 internet */
- char * buf;
- send_http_page(r, "Uh oh! Internet access unavailable!", buf);
- free(buf);
- }
- else if (!is_auth_online()) {
- /* auth server 掛起 */
- char * buf;
- send_http_page(r, "Uh oh! Login screen unavailable!", buf);
- free(buf);
- }
- else {
- /* 配置重新導向到 auth server 的 url 參數 */
- char *urlFragment;
- if (!(mac = arp_get(r->clientAddr))) {
- /* We could not get their MAC address */
- debug(LOG_INFO, "Failed to retrieve MAC address for ip %s, so not putting in the login request", r->clientAddr);
- 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);
- } else {
- debug(LOG_INFO, "Got client MAC address for ip %s: %s", r->clientAddr, mac);
- safe_asprintf(&urlFragment, "%sgw_address=%s&gw_port=%d&gw_id=%s&mac=%s&url=%s",
- auth_server->authserv_login_script_path_fragment,
- config->gw_address,
- config->gw_port,
- config->gw_id,
- mac,
- url);
- }
- /* 調用該函數將使用者請求重新導向到 auth server 的登入頁面 */
- http_send_redirect_to_auth(r, urlFragment, "Redirect to login page");
- free(urlFragment);
- }
- free(url);
- }
上面代碼基本不用解釋，具體重新導向至auth server的訊息在下面的 http_send_redirect_to_auth 函數中實現：
[cpp] view plaincopy
- 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);
- }
具體的重新導向URL給個執行個體：
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/1.1
可以看到這裡有這幾個參數資訊：
2gw_address，路由器的LAN地址
2gw_port：為wifidog的監聽連接埠
2gw_id：路由器的標識名
2mac：用戶端裝置的MAC地址
2url：為用戶端訪問的原URL（以便於重新導向）
