获取AP的状态信息（hostapd_cli）

通过hostapd创建了AP热点，但是Linux如何知道都有哪些设备连接到了AP呢？

hostapd是个后台服务程序，我们想知道它的状态可以通过hostapd_cli客户端对hostapd进行访问，进而获取到AP的状态和控制AP相关的功能。

下面是hostapd功能框架

hostapd_cli与hostapd是通过本地socket进行通信的，这个socket是hostapd启动以后根据hostapd.conf文件中的配置进行创建的,默认情况下的配置为:

# Interface for separate control program. If this is specified, hostapd
# will create this directory and a UNIX domain socket for listening to requests
# from external programs (CLI/GUI, etc.) for status information and
# configuration. The socket file will be named based on the interface name, so
# multiple hostapd processes/interfaces can be run at the same time if more
# than one interface is used.
# /var/run/hostapd is the recommended directory for sockets and by default,
# hostapd_cli will use it when trying to connect with hostapd.
ctrl_interface=/var/run/hostapd

默认情况下，hostapd_cli会连接到/var/run/hostapd下面的socket。

如果在hostapd.conf中没有指定ctrl_interface,那么hostapd是不会产生通信的socket共客户端访问，此时输入hostapd_cli会产生如下错误。

hostapd_cli v2.9
Copyright (c) 2004-2019, Jouni Malinen <j@w1.fi> and contributorsThis software may be distributed under the terms of the BSD license.
See README for more details.Could not connect to hostapd - re-trying

当然,ctrl_interface也可以自动定义,那么输入hostapd_cli时也需要指定这个对应的路径，一般不建议这么做。

我模拟AP的网卡是wlan0，当我启动hostapd后，会在/var/run/hostapd目录下创建一个socket，供客户端访问

# pwd
/var/run/hostapd
# ls -l
total 0
srwxrwx---    1 root     root             0 Jun 29 01:37 wlan0
#

hostapd_cli客户端使用

启动hostapd_cli客户端

在命令行中直接输入hostapd_cli命令即可。如果ctrl_interface不是默认参数，则需要输入hostapd_cli -s<dir_path>指定参数。输入命令后，出现交互命令行，则代表hostapd_cli与hostapd通信成功，可以进行其他功能的访问。

#
# hostapd_cli
hostapd_cli v2.9
Copyright (c) 2004-2019, Jouni Malinen <j@w1.fi> and contributorsThis software may be distributed under the terms of the BSD license.
See README for more details.Selected interface 'wlan0'Interactive mode>
>
>
>
>

输入help查看帮助信息

>
>
>
> help
commands:ping = pings hostapdmib = get MIB variables (dot1x, dot11, radius)relog = reload/truncate debug log output filestatus = show interface status infosta <addr> = get MIB variables for one stationall_sta = get MIB variables for all stationslist_sta = list all stationsnew_sta <addr> = add a new stationdeauthenticate <addr> = deauthenticate a stationdisassociate <addr> = disassociate a stationsa_query <addr> = send SA Query to a stationwps_pin <uuid> <pin> [timeout] [addr] = add WPS Enrollee PINwps_check_pin <PIN> = verify PIN checksumwps_pbc = indicate button pushed to initiate PBCwps_cancel = cancel the pending WPS operationwps_nfc_tag_read <hexdump> = report read NFC tag with WPS datawps_nfc_config_token <WPS/NDEF> = build NFC configuration tokenwps_nfc_token <WPS/NDEF/enable/disable> = manager NFC password tokenwps_ap_pin <cmd> [params..] = enable/disable AP PINwps_config <SSID> <auth> <encr> <key> = configure APwps_get_status = show current WPS statusdisassoc_imminent = send Disassociation Imminent notificationess_disassoc = send ESS Dissassociation Imminent notificationbss_tm_req = send BSS Transition Management Requestget_config = show current configurationhelp = show this usage helpinterface [ifname] = show interfaces/select interfaceraw <params..> = send unprocessed commandlevel <debug level> = change debug levellicense = show full hostapd_cli licensequit = exit hostapd_cliset <name> <value> = set runtime variablesget <name> = get runtime infoset_qos_map_set <arg,arg,...> = set QoS Map set elementsend_qos_map_conf <addr> = send QoS Map Configure framechan_switch <cs_count> <freq> [sec_channel_offset=] [center_freq1=][center_freq2=] [bandwidth=] [blocktx] [ht|vht]= initiate channel switch announcemenths20_wnm_notif <addr> <url>= send WNM-Notification Subscription Remediation Requesths20_deauth_req <addr> <code (0/1)> <Re-auth-Delay(sec)> [url]= send WNM-Notification imminent deauthentication indicationvendor <vendor id> <sub command id> [<hex formatted data>]= send vendor driver commandenable = enable hostapd on current interfacereload = reload configuration for current interfacedisable = disable hostapd on current interfaceupdate_beacon = update Beacon frame contentserp_flush = drop all ERP keyslog_level [level] = show/change log verbosity levelpmksa  = show PMKSA cache entriespmksa_flush  = flush PMKSA cacheset_neighbor <addr> <ssid=> <nr=> [lci=] [civic=] [stat]= add AP to neighbor databaseremove_neighbor <addr> <ssid=> = remove AP from neighbor databasereq_lci <addr> = send LCI request to a stationreq_range  = send FTM range requestdriver_flags  = show supported driver flagsaccept_acl =Add/Delete/Show/Clear accept MAC ACLdeny_acl =Add/Delete/Show/Clear deny MAC ACLpoll_sta <addr> = poll a STA to check connectivity with a QoS null framereq_beacon <addr> [req_mode=] <measurement request hexdump>  = send a Beacon report request to a stationreload_wpa_psk = reload wpa_psk_file only
>

查看所有已连接设备的信息

这样我们可以看到已连接设备的mac地址，连接时间等信息

> all_sta
ba:ba:3f:a9:cd:d4
flags=[AUTH][ASSOC][AUTHORIZED]
aid=0
capability=0x0
listen_interval=0
supported_rates=0c 18 30
timeout_next=NULLFUNC POLL
dot11RSNAStatsSTAAddress=ba:ba:3f:a9:cd:d4
dot11RSNAStatsVersion=1
dot11RSNAStatsSelectedPairwiseCipher=00-0f-ac-4
dot11RSNAStatsTKIPLocalMICFailures=0
dot11RSNAStatsTKIPRemoteMICFailures=0
wpa=2
AKMSuiteSelector=00-0f-ac-2
hostapdWPAPTKState=11
hostapdWPAPTKGroupState=0
rx_packets=0
tx_packets=0
rx_bytes=0
tx_bytes=0
inactive_msec=4000
signal=0
rx_rate_info=0
tx_rate_info=0
connected_time=1415
>

取消一个设备的接入认证

这样sta设备就会断开连接，但是如果sta选择的是自动连接，那么ap强制断开sta后，sta还会自动连接到AP。

> deauthenticate ba:ba:3f:a9:cd:d4
[ 5040.294654] [dhd-wlan0] wl_cfg80211_del_station : Disconnect STA ba:ba:3f:a9:cd:d4 scb_val.val 3
<3>AP-STA-DISCONNECTED ba:ba:3f:a9:cd:d4
[ 5040.306529] [dhd-wlan0] wl_cfg80211_del_station : Disconnect STA ba:ba:3f:a9:cd:d4 scb_val.val 3
OK
> [ 5040.749799] [dhd-wlan0] wl_ext_iapsta_event : [0 times] [A] disconnected device ba:ba:3f:a9:cd:d4, WLC_E_DEAUTH(5), reason=3
[ 5040.761421] [dhd-wlan0] wl_notify_connect_status_ap : [0 times] event WLC_E_DEAUTH(5) status 0 reason 3
[ 5040.771145] [dhd-wlan0] wl_notify_connect_status_ap : [0 times] deauthenticated device ba:ba:3f:a9:cd:d4
[ 5040.782470] [dhd-wlan0] wl_cfg80211_del_station : Disconnect STA ba:ba:3f:a9:cd:d4 scb_val.val 3
[ 5041.042141] [dhd-wlan0] wl_ext_iapsta_event : [A] connected device ba:ba:3f:a9:cd:d4
[ 5041.050166] [dhd-wlan0] wl_notify_connect_status_ap : connected device ba:ba:3f:a9:cd:d4
[ 5041.058726] [dhd] CFG80211-ERROR) wl_cfg80211_change_station : WLC_SCB_AUTHORIZE sta_flags_mask not set
<3>AP-STA-CONNECTED ba:ba:3f:a9:cd:d4>
>

还可以取消设备的关联等，这里不再一一列举。

这是命令行对hostapd通过交互的方式对hostapd进行访问，那如果要是c语言应用程序，如何访问hostapd状态呢？后面文章继续介绍。

参考链接：

http://w1.fi/wpa_supplicant/devel/

https://forum.huawei.com/enterprise/zh/thread-232281.html

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