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，
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 (1) {
/* 设置超时时间 */
timeout.tv_sec = time(NULL) + config_get_config()->checkinterval;
timeout.tv_nsec = 0;
/* 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 (-1 == 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, 0, 0);
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 = 0;
}
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[16],
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 -1;
}
/* 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 (2 == 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 -1;
}
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 (2 == 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 1;
}
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