wifidog 源碼初分析（2）

上一篇分析了接入設備的首次瀏覽器訪問請求如何通過 防火牆過濾規則 重定向到 wifidog 的 HTTP 服務中，本篇主要分析了 wifidog 在接收到 接入設備的 HTTP 訪問請求後，如何將此 HTTP 請求重定向到 認證服務器(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地址和端口通過NAT方式重定向至本地wifidog內嵌HTTP服務器的地址和端口上，並由內嵌HTTP服務器進行服務，而內嵌HTTP服務器的路徑和回調處理如下：

 

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);

 

客戶端首次訪問時回調客戶端首次訪問時回調http_callback_404函數，在該函數中根據獲取的客戶端信息來配置重定向的URL fragment，如下：

 

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.
     */ /* 用戶需要訪問的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 {
        /* 配置重定向到 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);
        }
        /* 調用該函數將用戶請求重定向到 auth server 的登錄頁面 */
        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，具體重定向至auth server的消息在下面的 http_send_redirect_to_auth 函數中實現：

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); 
}

具體的重定向URL給個實例：

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/1.1

可以看到這裏有這幾個參數信息：

2gw_address，路由器的LAN地址

2gw_port：爲wifidog的監聽端口

2gw_id：路由器的標識名

2mac：客戶端設備的MAC地址

2url：爲客戶端訪問的原URL（以便於重定向）