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wifidog 的核心還是依賴於 iptables 防火牆過濾規則來實現的，所以建議對 iptables 有了瞭解後再去閱讀 wifidog 的源碼。
在路由器上啟動 wifidog 之後，wifidog 在啟動時會初始化一堆的防火牆規則，如下：
[cpp] view plaincopy
- /** Initialize the firewall rules
- */
- int iptables_fw_init(void)
- {
- … …
- /*
- *
- * Everything in the NAT table
- *
- */
- /* Create new chains */
- iptables_do_command("-t nat -N " TABLE_WIFIDOG_OUTGOING);
- iptables_do_command("-t nat -N " TABLE_WIFIDOG_WIFI_TO_ROUTER);
- iptables_do_command("-t nat -N " TABLE_WIFIDOG_WIFI_TO_INTERNET);
- iptables_do_command("-t nat -N " TABLE_WIFIDOG_GLOBAL);
- iptables_do_command("-t nat -N " TABLE_WIFIDOG_UNKNOWN);
- iptables_do_command("-t nat -N " TABLE_WIFIDOG_AUTHSERVERS);
- /* Assign links and rules to these new chains */
- iptables_do_command("-t nat -A PREROUTING -i %s -j " TABLE_WIFIDOG_OUTGOING, config->gw_interface);
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_OUTGOING " -d %s -j " TABLE_WIFIDOG_WIFI_TO_ROUTER, config->gw_address);
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_WIFI_TO_ROUTER " -j ACCEPT");
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_OUTGOING " -j " TABLE_WIFIDOG_WIFI_TO_INTERNET);
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j ACCEPT", FW_MARK_KNOWN);
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j ACCEPT", FW_MARK_PROBATION);
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -j " TABLE_WIFIDOG_UNKNOWN);
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_UNKNOWN " -j " TABLE_WIFIDOG_AUTHSERVERS);
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_UNKNOWN " -j " TABLE_WIFIDOG_GLOBAL);
- // 將 80 連接埠的訪問重新導向(REDIRECT)到 (本路由)網關web伺服器的監聽連接埠
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_UNKNOWN " -p tcp --dport 80 -j REDIRECT --to-ports %d", gw_port);
- /*
- *
- * Everything in the FILTER table
- *
- */
- /* Create new chains */
- iptables_do_command("-t filter -N " TABLE_WIFIDOG_WIFI_TO_INTERNET);
- iptables_do_command("-t filter -N " TABLE_WIFIDOG_AUTHSERVERS);
- iptables_do_command("-t filter -N " TABLE_WIFIDOG_LOCKED);
- iptables_do_command("-t filter -N " TABLE_WIFIDOG_GLOBAL);
- iptables_do_command("-t filter -N " TABLE_WIFIDOG_VALIDATE);
- iptables_do_command("-t filter -N " TABLE_WIFIDOG_KNOWN);
- iptables_do_command("-t filter -N " TABLE_WIFIDOG_UNKNOWN);
- /* Assign links and rules to these new chains */
- /* Insert at the beginning */
- iptables_do_command("-t filter -I FORWARD -i %s -j " TABLE_WIFIDOG_WIFI_TO_INTERNET, config->gw_interface);
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m state --state INVALID -j DROP");
-
- /* TCPMSS rule for PPPoE */
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -o %s -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu", ext_interface);
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -j " TABLE_WIFIDOG_AUTHSERVERS);
- iptables_fw_set_authservers();
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j " TABLE_WIFIDOG_LOCKED, FW_MARK_LOCKED);
- iptables_load_ruleset("filter", "locked-users", TABLE_WIFIDOG_LOCKED);
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -j " TABLE_WIFIDOG_GLOBAL);
- iptables_load_ruleset("filter", "global", TABLE_WIFIDOG_GLOBAL);
- iptables_load_ruleset("nat", "global", TABLE_WIFIDOG_GLOBAL);
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j " TABLE_WIFIDOG_VALIDATE, FW_MARK_PROBATION);
- iptables_load_ruleset("filter", "validating-users", TABLE_WIFIDOG_VALIDATE);
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j " TABLE_WIFIDOG_KNOWN, FW_MARK_KNOWN);
- iptables_load_ruleset("filter", "known-users", TABLE_WIFIDOG_KNOWN);
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -j " TABLE_WIFIDOG_UNKNOWN);
- iptables_load_ruleset("filter", "unknown-users", TABLE_WIFIDOG_UNKNOWN);
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_UNKNOWN " -j REJECT --reject-with icmp-port-unreachable");
- UNLOCK_CONFIG();
- return 1;
- }
在該 防火牆規則的初始化過程中，會首先清除掉已有的防火牆規則，重新建立新的過濾鏈，另外，除了通過iptables_do_command("-t nat -A "TABLE_WIFIDOG_UNKNOWN " -p tcp --dport 80 -j REDIRECT --to-ports %d",gw_port); 這個命令將 接入裝置的 80 連接埠（HTTP）的訪問重新導向至網關自身的 HTTP 的連接埠之外，還通過iptables_fw_set_authservers(); 函數設定了 鑒權伺服器(auth-server) 的防火牆規則：
[cpp] view plaincopy
- void iptables_fw_set_authservers(void)
- {
- const s_config *config;
- t_auth_serv *auth_server;
- config = config_get_config();
- for (auth_server = config->auth_servers; auth_server != NULL; auth_server = auth_server->next) {
- if (auth_server->last_ip && strcmp(auth_server->last_ip, "0.0.0.0") != 0) {
- iptables_do_command("-t filter -A " TABLE_WIFIDOG_AUTHSERVERS " -d %s -j ACCEPT", auth_server->last_ip);
- iptables_do_command("-t nat -A " TABLE_WIFIDOG_AUTHSERVERS " -d %s -j ACCEPT", auth_server->last_ip);
- }
- }
- }
首先從上面的代碼可以看出 wifidog 支援多個 鑒權伺服器，並且針對每一個鑒權伺服器 設定了如下兩條規則：
1)在filter表中追加一條[任何訪問鑒權伺服器都被接受]的WiFiDog_$ID$_AuthServers過濾鏈：
iptables -t filter -A WiFiDog_$ID$_AuthServers -d auth-server地址 -j ACCEPT
2)在nat表中追加一條[任何訪問鑒權伺服器都被接受]的WiFiDog_$ID$_AuthServers過濾鏈：
iptables -t nat -A WiFiDog_$ID$_AuthServers -d auth-server地址 -j ACCEPT
這樣確保可以訪問鑒權伺服器，而不是拒絕所有的出口訪問。
