linux - 为什么我需要两个不同的 wpa_supplicant 连接（wpa_cli - ctrl_conn 和 mon_conn）

Question

我正在编写自己的 C 库来管理 linux 中的 wlan。我基于 wpa_cli 接口，但我不明白，为什么他们使用两个 wpa_ctrl 结构：

static struct wpa_ctrl *ctrl_conn;
static struct wpa_ctrl *mon_conn;

当我仅使用 ctrl_conn 打开和附加时它也有效吗？

Answer 1

wpa_cli有两种工作方式：交互式和非交互式

当您有提示时，您正在wpa_cli交互使用，反之亦然。

这是交互模式：

$ wpa_cli -i wlan0
wpa_cli v2.1
Copyright (c) 2004-2014, Jouni Malinen <j@w1.fi> and contributors

This software may be distributed under the terms of the BSD license.
See README for more details.

Interactive mode

> status
wpa_state=INACTIVE
address=98:fc:11:d1:89:68
uuid=0cb62eb3-776e-55d2-a4f9-983cdd3e48d2

并且是非交互模式：

$ wpa_cli -i wlan0 status
wpa_state=INACTIVE
address=98:fc:11:d1:89:68
uuid=0cb62eb3-776e-55d2-a4f9-983cdd3e48d2

似乎当您使用交互模式时，wpa_cli同时使用ctrl_conn和mon_conn。ctrl_conn仅用于发送命令，mon_conn用于获取事件（即，它是通过 附加的事件wpa_ctrl_attach()）。

而当你使用非交互模式时，wpa_cli只使用ctrl_conn因为没有返回事件。

如果您打算使用这些wpa_supplicant事件（我希望您会这样做），我认为最好使用两个不同的连接，如wpa_ctrl_request() 有关 msg_cb 参数的评论中所述：

/**
 * wpa_ctrl_request - Send a command to wpa_supplicant/hostapd
 * @ctrl: Control interface data from wpa_ctrl_open()
 * @cmd: Command; usually, ASCII text, e.g., "PING"
 * @cmd_len: Length of the cmd in bytes
 * @reply: Buffer for the response
 * @reply_len: Reply buffer length
 * @msg_cb: Callback function for unsolicited messages or %NULL if not used
 * Returns: 0 on success, -1 on error (send or receive failed), -2 on timeout
 *
 * This function is used to send commands to wpa_supplicant/hostapd. Received
 * response will be written to reply and reply_len is set to the actual length
 * of the reply. This function will block for up to two seconds while waiting
 * for the reply. If unsolicited messages are received, the blocking time may
 * be longer.
 *
 * msg_cb can be used to register a callback function that will be called for
 * unsolicited messages received while waiting for the command response. These
 * messages may be received if wpa_ctrl_request() is called at the same time as
 * wpa_supplicant/hostapd is sending such a message. This can happen only if
 * the program has used wpa_ctrl_attach() to register itself as a monitor for
 * event messages. Alternatively to msg_cb, programs can register two control
 * interface connections and use one of them for commands and the other one for
 * receiving event messages, in other words, call wpa_ctrl_attach() only for
 * the control interface connection that will be used for event messages.
 */
int wpa_ctrl_request(struct wpa_ctrl *ctrl, const char *cmd, size_t cmd_len,
             char *reply, size_t *reply_len,
             void (*msg_cb)(char *msg, size_t len));