Wifidog是一个linux下开源的认证网关软件,它主要用于配合认证服务器实现无线路由器的认证放行功能。
wifidog是一个后台的服务程序,可以通过wdctrl命令对wifidog主程序进行控制。
本文解释wifidog在启动阶段所做的初始化主要工作(代码片段1.1)
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初始化配置(先将配置结构体初始化为默认值,在读取配置文件修改配置结构体)
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初始化已连接客户端列表(如果是通过wdctrl重启wifidog,将会读取之前wifidog的已连接客户端列表 代码片段1.2 代码片段1.3)
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如无特殊情况,分离进程,建立守护进程 (代码片段1.1)
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添加多个http请求回调函数(包括404错误回调函数) (见之后章节)
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摧毁删除现有的iptables路由表规则 (见之后章节)
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建立新的iptables路由表规则 (见之后章节)
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启动多个功能线程 (见之后章节)
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循环等待客户端连接 (见之后章节)
代码片段1.1
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int main(int argc, char **argv) {
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s_config *config = config_get_config(); //就是返回全局变量config结构体的地址
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config_init(); //初始化全局变量config结构体为默认值
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parse_commandline(argc, argv); //根据传入参数执行操作(如果参数有-x则会设置restart_orig_pid为已运行的wifidog的pid)
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/* Initialize the config */
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config_read(config->configfile); //根据配置文件设置全局变量config结构体
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config_validate(); //判断GatewayInterface和AuthServer是否为空,空则无效退出程序。
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/* Initializes the linked list of connected clients */
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client_list_init(); //将已连接客户端链表置空。
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/* Init the signals to catch chld/quit/etc */
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init_signals(); //初始化一些信号
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if (restart_orig_pid) { //用于restart,如果有已运行的wifidog,先会kill它
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/*
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* We were restarted and our parent is waiting for us to talk to it over the socket
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*/
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get_clients_from_parent(); //从已运行的wifidog中获取客户端列表,详见 代码片段1.2
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/*
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* At this point the parent will start destroying itself and the firewall. Let it finish it's job before we continue
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*/
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while (kill(restart_orig_pid, 0) != -1) { //kill已运行的wifidog
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debug(LOG_INFO, "Waiting for parent PID %d to die before continuing loading", restart_orig_pid);
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sleep(1);
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}
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debug(LOG_INFO, "Parent PID %d seems to be dead. Continuing loading.");
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}
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if (config->daemon) { //创建为守护进程,config->daemon默认值为-1
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debug(LOG_INFO, "Forking into background");
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switch(safe_fork()) {
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case 0: /* child */
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setsid(); //创建新会话,脱离此终端,实现守护进程
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append_x_restartargv();
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main_loop(); //进入主循环(核心代码在此)。
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break;
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default: /* parent */
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exit(0);
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break;
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}
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}
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else {
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append_x_restartargv();
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main_loop();
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}
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return(0); /* never reached */
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}
代码片段1.2(获取已启动的wifidog的客户端列表):
此段代表描述了新启动的wifidog如何从已启动的wifidog程序中获取已连接的客户端列表。发送端见 代码片段1.3
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void get_clients_from_parent(void) {
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int sock;
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struct sockaddr_un sa_un;
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s_config * config = NULL;
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char linebuffer[MAX_BUF];
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int len = 0;
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char *running1 = NULL;
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char *running2 = NULL;
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char *token1 = NULL;
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char *token2 = NULL;
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char onechar;
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char *command = NULL;
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char *key = NULL;
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char *value = NULL;
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t_client * client = NULL;
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t_client * lastclient = NULL;
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config = config_get_config();
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debug(LOG_INFO, "Connecting to parent to download clients");
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/* 连接socket */
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sock = socket(AF_UNIX, SOCK_STREAM, 0);
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memset(&sa_un, 0, sizeof(sa_un));
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sa_un.sun_family = AF_UNIX;
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strncpy(sa_un.sun_path, config->internal_sock, (sizeof(sa_un.sun_path) - 1)); //config->internal_sock的值为"/tmp/wifidog.sock"
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/* 连接已启动的wifidog */
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if (connect(sock, (struct sockaddr *)&sa_un, strlen(sa_un.sun_path) + sizeof(sa_un.sun_family))) {
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debug(LOG_ERR, "Failed to connect to parent (%s) - client list not downloaded", strerror(errno));
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return;
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}
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debug(LOG_INFO, "Connected to parent. Downloading clients");
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LOCK_CLIENT_LIST();
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command = NULL;
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memset(linebuffer, 0, sizeof(linebuffer));
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len = 0;
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client = NULL;
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/* 接收数据,逐个字符接收 */
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/* 数据包格式为 CLIENT|ip=%s|mac=%s|token=%s|fw_connection_state=%u|fd=%d|counters_incoming=%llu|counters_outgoing=%llu|counters_last_updated=%lu\n */
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while (read(sock, &onechar, 1) == 1) {
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if (onechar == '\n') {
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/* 如果接收到末尾('\n'),则转为'\0' */
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onechar = '\0';
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}
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linebuffer[len++] = onechar;
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if (!onechar) {
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/* 以下将数据转化为t_client结构体添加到客户端列表 */
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debug(LOG_DEBUG, "Received from parent: [%s]", linebuffer);
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running1 = linebuffer;
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while ((token1 = strsep(&running1, "|")) != NULL) {
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if (!command) {
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/* The first token is the command */
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command = token1;
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}
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else {
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/* Token1 has something like "foo=bar" */
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running2 = token1;
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key = value = NULL;
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while ((token2 = strsep(&running2, "=")) != NULL) {
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if (!key) {
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key = token2;
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}
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else if (!value) {
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value = token2;
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}
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}
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}
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if (strcmp(command, "CLIENT") == 0) {
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/* This line has info about a client in the client list */
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if (!client) {
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/* Create a new client struct */
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client = safe_malloc(sizeof(t_client));
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memset(client, 0, sizeof(t_client));
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}
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}
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if (key && value) {
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if (strcmp(command, "CLIENT") == 0) {
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/* Assign the key into the appropriate slot in the connection structure */
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if (strcmp(key, "ip") == 0) {
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client->ip = safe_strdup(value);
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}
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else if (strcmp(key, "mac") == 0) {
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client->mac = safe_strdup(value);
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}
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else if (strcmp(key, "token") == 0) {
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client->token = safe_strdup(value);
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}
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else if (strcmp(key, "fw_connection_state") == 0) {
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client->fw_connection_state = atoi(value);
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}
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else if (strcmp(key, "fd") == 0) {
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client->fd = atoi(value);
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}
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else if (strcmp(key, "counters_incoming") == 0) {
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client->counters.incoming_history = atoll(value);
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client->counters.incoming = client->counters.incoming_history;
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}
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else if (strcmp(key, "counters_outgoing") == 0) {
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client->counters.outgoing_history = atoll(value);
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client->counters.outgoing = client->counters.outgoing_history;
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}
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else if (strcmp(key, "counters_last_updated") == 0) {
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client->counters.last_updated = atol(value);
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}
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else {
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debug(LOG_NOTICE, "I don't know how to inherit key [%s] value [%s] from parent", key, value);
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}
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}
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}
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}
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/* End of parsing this command */
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if (client) {
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/* Add this client to the client list */
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if (!firstclient) {
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firstclient = client;
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lastclient = firstclient;
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}
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else {
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lastclient->next = client;
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lastclient = client;
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}
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}
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/* Clean up */
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command = NULL;
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memset(linebuffer, 0, sizeof(linebuffer));
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len = 0;
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client = NULL;
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}
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}
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UNLOCK_CLIENT_LIST();
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debug(LOG_INFO, "Client list downloaded successfully from parent");
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close(sock);
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}
代码片段1.3(已启动的wifidog发送客户端列表到新启动的wifidog):
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//thread_wdctl_handler(void *arg)函数是wifidog启动后自动创建的控制线程,主要用于与wdctrl进行socket通信,根据wdctrl命令执行不同的操作。这里我们着重讲解的是wdctrl发送restart后wifidog的执行逻辑。
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static void *
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thread_wdctl_handler(void *arg)
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{
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int fd,
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done,
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i;
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char request[MAX_BUF];
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ssize_t read_bytes,
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len;
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debug(LOG_DEBUG, "Entering thread_wdctl_handler....");
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fd = (int)arg;
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debug(LOG_DEBUG, "Read bytes and stuff from %d", fd);
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/* 初始化变量 */
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read_bytes = 0;
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done = 0;
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memset(request, 0, sizeof(request));
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/* 读取命令 */
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while (!done && read_bytes < (sizeof(request) - 1)) {
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len = read(fd, request + read_bytes,
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sizeof(request) - read_bytes); //读取wdctrl发送的命令
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/* 判断命令正确性 */
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for (i = read_bytes; i < (read_bytes + len); i++) {
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if (request[i] == '\r' || request[i] == '\n') {
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request[i] = '\0';
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done = 1;
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}
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}
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/* Increment position */
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read_bytes += len;
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}
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//判断命令
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if (strncmp(request, "status", 6) == 0) {
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wdctl_status(fd);
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} else if (strncmp(request, "stop", 4) == 0) {
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wdctl_stop(fd);
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} else if (strncmp(request, "reset", 5) == 0) {
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wdctl_reset(fd, (request + 6));
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} else if (strncmp(request, "restart", 7) == 0) {
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wdctl_restart(fd); //执行wdctl_restart(int afd)函数
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}
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if (!done) {
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debug(LOG_ERR, "Invalid wdctl request.");
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//关闭套接字
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shutdown(fd, 2);
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close(fd);
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pthread_exit(NULL);
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}
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debug(LOG_DEBUG, "Request received: [%s]", request);
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//关闭套接字
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shutdown(fd, 2);
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close(fd);
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debug(LOG_DEBUG, "Exiting thread_wdctl_handler....");
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return NULL;
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}
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//wdctl_restart(int afd)函数详解
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static void
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wdctl_restart(int afd)
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{
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int sock,
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fd;
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char *sock_name;
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struct sockaddr_un sa_un;
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s_config * conf = NULL;
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t_client * client = NULL;
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char * tempstring = NULL;
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pid_t pid;
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ssize_t written;
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socklen_t len;
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conf = config_get_config();
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debug(LOG_NOTICE, "Will restart myself");
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/*
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* 准备内部连接socket
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*/
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memset(&sa_un, 0, sizeof(sa_un));
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sock_name = conf->internal_sock; //conf->internal_sock值为"/tmp/wifidog.sock"
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debug(LOG_DEBUG, "Socket name: %s", sock_name);
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if (strlen(sock_name) > (sizeof(sa_un.sun_path) - 1)) {
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debug(LOG_ERR, "INTERNAL socket name too long");
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return;
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}
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debug(LOG_DEBUG, "Creating socket");
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sock = socket(PF_UNIX, SOCK_STREAM, 0); //建立内部socket套接字
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debug(LOG_DEBUG, "Got internal socket %d", sock);
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/* 如果sock_name文件存在,则删除*/
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unlink(sock_name);
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debug(LOG_DEBUG, "Filling sockaddr_un");
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strcpy(sa_un.sun_path, sock_name);
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sa_un.sun_family = AF_UNIX;
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debug(LOG_DEBUG, "Binding socket (%s) (%d)", sa_un.sun_path, strlen(sock_name));
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if (bind(sock, (struct sockaddr *)&sa_un, strlen(sock_name) + sizeof(sa_un.sun_family))) {
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debug(LOG_ERR, "Could not bind internal socket: %s", strerror(errno));
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return;
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}
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if (listen(sock, 5)) {
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debug(LOG_ERR, "Could not listen on internal socket: %s", strerror(errno));
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return;
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}
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/*
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* socket建立完成,创建子进程
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*/
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debug(LOG_DEBUG, "Forking in preparation for exec()...");
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pid = safe_fork();
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if (pid > 0) {
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/* 父进程 */
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/* 等待子进程连接此socket :*/
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debug(LOG_DEBUG, "Waiting for child to connect on internal socket");
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len = sizeof(sa_un);
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if ((fd = accept(sock, (struct sockaddr *)&sa_un, &len)) == -1){ //接受连接
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debug(LOG_ERR, "Accept failed on internal socket: %s", strerror(errno));
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close(sock);
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return;
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}
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close(sock);
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debug(LOG_DEBUG, "Received connection from child. Sending them all existing clients");
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/*子进程已经完成连接,发送客户端列表 */
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LOCK_CLIENT_LIST();
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client = client_get_first_client(); //获取第一个客户端
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while (client) {
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/* Send this client */
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safe_asprintf(&tempstring, "CLIENT|ip=%s|mac=%s|token=%s|fw_connection_state=%u|fd=%d|counters_incoming=%llu|counters_outgoing=%llu|counters_last_updated=%lu\n", client->ip, client->mac, client->token, client->fw_connection_state, client->fd, client->counters.incoming, client->counters.outgoing, client->counters.last_updated);
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debug(LOG_DEBUG, "Sending to child client data: %s", tempstring);
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len = 0;
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while (len != strlen(tempstring)) {
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written = write(fd, (tempstring + len), strlen(tempstring) - len); //发送给子进程
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if (written == -1) {
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debug(LOG_ERR, "Failed to write client data to child: %s", strerror(errno));
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free(tempstring);
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break;
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}
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else {
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len += written;
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}
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}
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free(tempstring);
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client = client->next;
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}
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UNLOCK_CLIENT_LIST();
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close(fd);
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debug(LOG_INFO, "Sent all existing clients to child. Committing suicide!");
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shutdown(afd, 2);
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close(afd);
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wdctl_stop(afd);
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}
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else {
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/* 子进程,先关闭资源 */
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close(wdctl_socket_server);
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close(icmp_fd);
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close(sock);
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shutdown(afd, 2);
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close(afd);
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debug(LOG_NOTICE, "Re-executing myself (%s)", restartargv[0]);
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setsid();
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execvp(restartargv[0], restartargv); //执行外部命令,这里重新启动wifidog
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debug(LOG_ERR, "I failed to re-execute myself: %s", strerror(errno));
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debug(LOG_ERR, "Exiting without cleanup");
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exit(1);
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}
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}
小结
客户端列表只有在restart命令中才会执行,实际上流程就是
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父wifidog准备socket
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父wifidog启动子wifidog
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子wifidog连接父wifidog
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客户端列表传递
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子wifidog终止父wifidog
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