wifidog源码分析 - 客户端检测线程

引言

　　当wifidog启动时，会启动一个线程(thread_client_timeout_check)维护客户端列表，具体就是wifidog必须定时检测客户端列表中的每个客户端是否在线，而wifidog是通过两种方式进行检测客户端在线情况，一种是定时通过iptables获取客户端出入总流量更新客户端时间，通过最近更新时间进行判断（有新的出入流量则更新客户端时间，之后使用最新客户端时间与当前时间判断），一种是查询认证服务器，通过认证服务器的返回信息进行判断（将客户端IP和状态请求发送给认证服务器，认证服务器会返回客户端是否在线，这种情况是用于客户端是在认证服务器上正常登出）。

thread_client_timeout_check

　　此线程执行函数用于维护客户端列表，此线程是一个while （1）循环，每隔一个配置文件中的checkinterval时间间隔执行一次fw_sync_with_authserver函数，核心代码处于fw_sync_with_authserver函数中，我们先具体代码

代码片段1.1

 void
 thread_client_timeout_check(const void *arg)
 {
     pthread_cond_t        cond = PTHREAD_COND_INITIALIZER;
     pthread_mutex_t        cond_mutex = PTHREAD_MUTEX_INITIALIZER;
     struct    timespec    timeout;

     while () {
         /* 设置超时时间 */
         timeout.tv_sec = time(NULL) + config_get_config()->checkinterval;
         timeout.tv_nsec = ;

         /* 使用pthread_cond_timedwait必须先上锁 */
         pthread_mutex_lock(&cond_mutex);

         /* 等待超时 */
         pthread_cond_timedwait(&cond, &cond_mutex, &timeout);

         /* 解锁 */
         pthread_mutex_unlock(&cond_mutex);

         debug(LOG_DEBUG, "Running fw_counter()");

         /* 执行核心代码 */
         fw_sync_with_authserver();
     }
 }

fw_sync_with_authserver

　　此函数是此线程的核心函数，维护客户端列表就在此中，其首先会遍历客户端列表，通过iptables获取每个客户端列表的出入流量，之后根据出口流量(入口流量不做判断，详见 代码片段1.3)更新客户端最近更新时间（last_updated），之后使用每个客户端最近更新时间与当前时间比较，如果超过超时间隔则判断为下线，而如果未超时，则还会从认证服务器中获取此客户端状态，确定其是否在线。具体流程如下

• 更新客户端出入口流量，根据出口流量更新每个客户端的最近更新时间
• 客户端超时则从客户端列表中移除并通过iptables禁止其访问网络，并告知认证服务器此客户端下线
• 客户端未超时则从认证服务器获取此客户端信息，判断其是否通过认证服务器下线

代码片段1.2

 void
 fw_sync_with_authserver(void)
 {
     t_authresponse  authresponse;
     char            *token, *ip, *mac;
     t_client        *p1, *p2;
     unsigned long long        incoming, outgoing;
     s_config *config = config_get_config();

     /* 根据iptables流量更新最近更新时间，具体代码见 代码片段1.3 */
     if (- == iptables_fw_counters_update()) {
         debug(LOG_ERR, "Could not get counters from firewall!");
         return;
     }

     LOCK_CLIENT_LIST();

     /* 遍历客户端列表 */
     for (p1 = p2 = client_get_first_client(); NULL != p1; p1 = p2) {
         p2 = p1->next;

         ip = safe_strdup(p1->ip);
         token = safe_strdup(p1->token);
         mac = safe_strdup(p1->mac);
         outgoing = p1->counters.outgoing;
         incoming = p1->counters.incoming;

         UNLOCK_CLIENT_LIST();
         /* ping一下此客户端，不清楚作用 */
         icmp_ping(ip);
         /* 将客户端的出入流量上传至认证服务器，此时如果此客户端在认证服务器上下线会返回告知wifidog */
         if (config->auth_servers != NULL) {
             auth_server_request(&authresponse, REQUEST_TYPE_COUNTERS, ip, mac, token, incoming, outgoing);
         }
         LOCK_CLIENT_LIST();

         /* 从客户端列表获取IP,MAC对应客户端 */
         if (!(p1 = client_list_find(ip, mac))) {
             debug(LOG_ERR, "Node %s was freed while being re-validated!", ip);
         } else {
             time_t    current_time=time(NULL);
             debug(LOG_INFO, "Checking client %s for timeout:  Last updated %ld (%ld seconds ago), timeout delay %ld seconds, current time %ld, ",
                         p1->ip, p1->counters.last_updated, current_time-p1->counters.last_updated, config->checkinterval * config->clienttimeout, current_time);
             /* 判断是否超时，(最近更新时间 + 超时时间 <= 当前时间) 表明以超过超时时间，下线 */
             if (p1->counters.last_updated +
                 (config->checkinterval * config->clienttimeout)
                 <= current_time) {
                 debug(LOG_INFO, "%s - Inactive for more than %ld seconds, removing client and denying in firewall",
                         p1->ip, config->checkinterval * config->clienttimeout);
                 /* 修改iptables禁止此客户端访问外网 */
                 fw_deny(p1->ip, p1->mac, p1->fw_connection_state);
                 /* 从客户端列表中删除此客户端 */
                 client_list_delete(p1);

                 /* 通知认证服务器此客户端下线 */
                 if (config->auth_servers != NULL) {
                     UNLOCK_CLIENT_LIST();
                     auth_server_request(&authresponse, REQUEST_TYPE_LOGOUT, ip, mac, token, , );
                     LOCK_CLIENT_LIST();
                 }
             } else {
                 /* 未超时处理 */
                 if (config->auth_servers != NULL) {
                     /* 判断认证服务器返回信息 */
                     switch (authresponse.authcode) {
                         /* 认证服务器禁止其访问网络(下线或遭拒绝) */
                         case AUTH_DENIED:
                             debug(LOG_NOTICE, "%s - Denied. Removing client and firewall rules", p1->ip);
                             fw_deny(p1->ip, p1->mac, p1->fw_connection_state);
                             client_list_delete(p1);
                             break;

                         case AUTH_VALIDATION_FAILED:
                             debug(LOG_NOTICE, "%s - Validation timeout, now denied. Removing client and firewall rules", p1->ip);
                             fw_deny(p1->ip, p1->mac, p1->fw_connection_state);
                             client_list_delete(p1);
                             break;

                         /* 认证服务器允许其访问网络(在线) */
                         case AUTH_ALLOWED:
                             if (p1->fw_connection_state != FW_MARK_KNOWN) {
                                 debug(LOG_INFO, "%s - Access has changed to allowed, refreshing firewall and clearing counters", p1->ip);
                                 if (p1->fw_connection_state != FW_MARK_PROBATION) {
                                     p1->counters.incoming = p1->counters.outgoing = ;
                                 }
                                 else {

                                     debug(LOG_INFO, "%s - Skipped clearing counters after all, the user was previously in validation", p1->ip);
                                 }
                                 p1->fw_connection_state = FW_MARK_KNOWN;
                                 fw_allow(p1->ip, p1->mac, p1->fw_connection_state);
                             }
                             break;

                         case AUTH_VALIDATION:
                             debug(LOG_INFO, "%s - User in validation period", p1->ip);
                             break;

                             case AUTH_ERROR:
                                     debug(LOG_WARNING, "Error communicating with auth server - leaving %s as-is for now", p1->ip);
                                     break;

                         default:
                             debug(LOG_ERR, "I do not know about authentication code %d", authresponse.authcode);
                             break;
                     }
                 }
             }
         }

         free(token);
         free(ip);
         free(mac);
     }
     UNLOCK_CLIENT_LIST();
 }

代码片段1.3

 int
 iptables_fw_counters_update(void)
 {
     FILE *output;
     char *script,
          ip[],
          rc;
     unsigned long long int counter;
     t_client *p1;
     struct in_addr tempaddr;

     /* 通过iptables获取其出口流量 */
     safe_asprintf(&script, "%s %s", "iptables", "-v -n -x -t mangle -L " TABLE_WIFIDOG_OUTGOING);
     iptables_insert_gateway_id(&script);
     output = popen(script, "r");
     free(script);
     if (!output) {
         debug(LOG_ERR, "popen(): %s", strerror(errno));
         return -;
     }

     /* iptables返回信息处理 */
     while (('\n' != fgetc(output)) && !feof(output))
         ;
     while (('\n' != fgetc(output)) && !feof(output))
         ;
     while (output && !(feof(output))) {
         rc = fscanf(output, "%*s %llu %*s %*s %*s %*s %*s %15[0-9.] %*s %*s %*s %*s %*s %*s", &counter, ip);
         //rc = fscanf(output, "%*s %llu %*s %*s %*s %*s %*s %15[0-9.] %*s %*s %*s %*s %*s 0x%*u", &counter, ip);
         if ( == rc && EOF != rc) {
             if (!inet_aton(ip, &tempaddr)) {
                 debug(LOG_WARNING, "I was supposed to read an IP address but instead got [%s] - ignoring it", ip);
                 continue;
             }
             debug(LOG_DEBUG, "Read outgoing traffic for %s: Bytes=%llu", ip, counter);
             LOCK_CLIENT_LIST();
             /* 通过ip获取客户端信息结构 */
             if ((p1 = client_list_find_by_ip(ip))) {
                 /* (上一次出口总流量(outgoing) + wifidog启动时的出口总流量(outgoing_history) < iptables返回的出口总流量) 表示此客户端有新的出口流量 */
                 if ((p1->counters.outgoing - p1->counters.outgoing_history) < counter) {
                     /* 更新上一次出口总流量(outgoing)为wifidog启动时的出口总流量(outgoing_history) + iptables返回总流量(counter) */
                     p1->counters.outgoing = p1->counters.outgoing_history + counter;
                     /* 更新最近更新时间为当前时间 */
                     p1->counters.last_updated = time(NULL);
                     debug(LOG_DEBUG, "%s - Updated counter.outgoing to %llu bytes.  Updated last_updated to %d", ip, counter, p1->counters.last_updated);
                 }
             } else {
                 debug(LOG_ERR, "Could not find %s in client list", ip);
             }
             UNLOCK_CLIENT_LIST();
         }
     }
     pclose(output);

     /* 通过iptables获取其入口流量，入口流量不做更新最近更新时间参考，只用于更新后上传至认证服务器，其原理同上，后面的代码不做详细分析 */
     safe_asprintf(&script, "%s %s", "iptables", "-v -n -x -t mangle -L " TABLE_WIFIDOG_INCOMING);
     iptables_insert_gateway_id(&script);
     output = popen(script, "r");
     free(script);
     if (!output) {
         debug(LOG_ERR, "popen(): %s", strerror(errno));
         return -;
     }

     while (('\n' != fgetc(output)) && !feof(output))
         ;
     while (('\n' != fgetc(output)) && !feof(output))
         ;
     while (output && !(feof(output))) {
         rc = fscanf(output, "%*s %llu %*s %*s %*s %*s %*s %*s %15[0-9.]", &counter, ip);
         if ( == rc && EOF != rc) {

             if (!inet_aton(ip, &tempaddr)) {
                 debug(LOG_WARNING, "I was supposed to read an IP address but instead got [%s] - ignoring it", ip);
                 continue;
             }
             debug(LOG_DEBUG, "Read incoming traffic for %s: Bytes=%llu", ip, counter);
             LOCK_CLIENT_LIST();
             if ((p1 = client_list_find_by_ip(ip))) {
                 if ((p1->counters.incoming - p1->counters.incoming_history) < counter) {
                     p1->counters.incoming = p1->counters.incoming_history + counter;
                     debug(LOG_DEBUG, "%s - Updated counter.incoming to %llu bytes", ip, counter);
                 }
             } else {
                 debug(LOG_ERR, "Could not find %s in client list", ip);
             }
             UNLOCK_CLIENT_LIST();
         }
     }
     pclose(output);

     return ;
 }