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：

[cpp] view plaincopy

1. if ((webserver = httpdCreate(config->gw_address, config->gw_port)) == NULL) {  
2. debug(LOG_ERR, "Could not create web server: %s", strerror(errno));  
3. exit(1);  
4. }  
5. debug(LOG_DEBUG, "Assigning callbacks to web server");  
6. httpdAddCContent(webserver, "/", "wifidog", 0, NULL, http_callback_wifidog);  
7. httpdAddCContent(webserver, "/wifidog", "", 0, NULL, http_callback_wifidog);  
8. httpdAddCContent(webserver, "/wifidog", "about", 0, NULL, http_callback_about);  
9. httpdAddCContent(webserver, "/wifidog", "status", 0, NULL, http_callback_status);  
10. httpdAddCContent(webserver, "/wifidog", "auth", 0, NULL, http_callback_auth);  
12. 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：

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1. void
2. http_callback_404(httpd *webserver, request *r)  
3. {  
4. char tmp_url[MAX_BUF],  
5. *url,  
6. *mac;  
7. s_config    *config = config_get_config();  
8. t_auth_serv *auth_server = get_auth_server();  
9. memset(tmp_url, 0, sizeof(tmp_url));  
10. /*
11. * XXX Note the code below assumes that the client's request is a plain
12. * http request to a standard port. At any rate, this handler is called only
13. * if the internet/auth server is down so it's not a huge loss, but still.
14. */ /* 用户需要访问的URL */
15. snprintf(tmp_url, (sizeof(tmp_url) - 1), "http://%s%s%s%s",  
16. r->request.host,  
17. r->request.path,  
18. r->request.query[0] ? "?" : "",  
19. r->request.query);  
20. url = httpdUrlEncode(tmp_url);  
21. if (!is_online()) {  
22. /* 路由器都接入不到 internet */
23. char * buf;  
24. send_http_page(r, "Uh oh! Internet access unavailable!", buf);  
25. free(buf);  
26. }  
27. else if (!is_auth_online()) {  
28. /* auth server 挂起 */
29. char * buf;  
30. send_http_page(r, "Uh oh! Login screen unavailable!", buf);  
31. free(buf);  
32. }  
33. else {  
34. /* 配置重定向到 auth server 的 url 参数 */
35. char *urlFragment;  
36. if (!(mac = arp_get(r->clientAddr))) {  
37. /* We could not get their MAC address */
38. debug(LOG_INFO, "Failed to retrieve MAC address for ip %s, so not putting in the login request", r->clientAddr);  
39. safe_asprintf(&urlFragment, "%sgw_address=%s&gw_port=%d&gw_id=%s&url=%s",  
40. auth_server->authserv_login_script_path_fragment,  
41. config->gw_address,  
42. config->gw_port,  
43. config->gw_id,  
44. url);  
45. } else {            
46. debug(LOG_INFO, "Got client MAC address for ip %s: %s", r->clientAddr, mac);  
47. safe_asprintf(&urlFragment, "%sgw_address=%s&gw_port=%d&gw_id=%s&mac=%s&url=%s",  
48. auth_server->authserv_login_script_path_fragment,  
49. config->gw_address,  
50. config->gw_port,  
51. config->gw_id,  
52. mac,  
53. url);  
54. }  
55. /* 调用该函数将用户请求重定向到 auth server 的登录页面 */
56. http_send_redirect_to_auth(r, urlFragment, "Redirect to login page");  
57. free(urlFragment);  
58. }  
59. free(url);  
60. }

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：

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1. void http_send_redirect_to_auth(request *r, char *urlFragment, char *text)  
2. {  
3. char *protocol = NULL;  
4. int port = 80;  
5. t_auth_serv *auth_server = get_auth_server();  
6. if (auth_server->authserv_use_ssl) {  
7. protocol = "https";  
8. port = auth_server->authserv_ssl_port;  
9. } else {  
10. protocol = "http";  
11. port = auth_server->authserv_http_port;  
12. }  
14. char *url = NULL;  
15. safe_asprintf(&url, "%s://%s:%d%s%s",  
16. protocol,  
17. auth_server->authserv_hostname,  
18. port,  
19. auth_server->authserv_path,  
20. urlFragment  
21. );  
22. http_send_redirect(r, url, text);  
23. free(url);  
24. }

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/1.1

可以看到这里有这几个参数信息：

2gw_address，路由器的LAN地址

2gw_port：为wifidog的监听端口

2gw_id：路由器的标识名

2mac：客户端设备的MAC地址

2url：为客户端访问的原URL（以便于重定向）