wpa_supplicant与kernel交互

wpa_supplicant与kernel交互的操作，一般需要先明确驱动接口，以及用户态和kernel态的接口函数，以此来进行调用操作。这里分为4个步骤讨论。

1.首先需要明确指定的驱动接口。因为有较多的驱动接口可以使用，如wext、nl80211等。指定了之后，才能调用相应接口的方法。

2.保存驱动接口

3.接口函数的实现(分为用户态和kernel态)。系统已经定义了，我们只需找到定义的地方，了解有哪些函数。

4.交互

(a)用户态向kernel态发送请求(通过ioctl)

(b)kernel态向用户态发送事件通知(通过netlink)

1.首先需要明确指定的驱动接口

(1)查看init.XX.rc中指定的driver的命令参数；

(2)根据命令参数，在wpa_driver_ops *wpa_drivers[] 中查找对应接口。

wpa_drivers[]的定义是在[-->external/wpa_supplicant_8/src/drivers/drivers.c]

2.保存驱动接口

在wpa_supplicant初始化过程中，在wpa_supplicant_init_iface方法中会调用wpa_supplicant_set_driver方法。该方法中又会调用select_driver方法。

static int select_driver(struct wpa_supplicant *wpa_s, int i)
{    struct wpa_global *global = wpa_s->global;if (wpa_drivers[i]->global_init && global->drv_priv[i] == NULL) { 
    //调用global_init方法，这与driver选择wext调用的流程不同了
        global->drv_priv[i] = wpa_drivers[i]->global_init();        if (global->drv_priv[i] == NULL) {
            wpa_printf(MSG_ERROR, "Failed to initialize driver " 
                   "'%s'", wpa_drivers[i]->name); 
            return -1;
        }
    }  
// 根据name进行匹配，并最后保存到wpa_supplicant->dirver中
    wpa_s->driver = wpa_drivers[i];
    wpa_s->global_drv_priv = global->drv_priv[i];    return 0;
}

3.接口操作函数实现

3.1用户态

代码：/external/wpa_supplicant_8/wpa_supplicant/src/drivers/driver_nl80211.c

const struct wpa_driver_ops wpa_driver_nl80211_ops = {
    .name = "nl80211",
    .desc = "Linux nl80211/cfg80211",
    .get_bssid = wpa_driver_nl80211_get_bssid,
    .get_ssid = wpa_driver_nl80211_get_ssid,
    .set_key = wpa_driver_nl80211_set_key,
    .scan2 = wpa_driver_nl80211_scan,
    .sched_scan = wpa_driver_nl80211_sched_scan,
    .stop_sched_scan = wpa_driver_nl80211_stop_sched_scan,
    .get_scan_results2 = wpa_driver_nl80211_get_scan_results,
    .deauthenticate = wpa_driver_nl80211_deauthenticate,
    .disassociate = wpa_driver_nl80211_disassociate,
    .authenticate = wpa_driver_nl80211_authenticate,
    .associate = wpa_driver_nl80211_associate,
    .global_init = nl80211_global_init,
    .global_deinit = nl80211_global_deinit,
    .init2 = wpa_driver_nl80211_init,
    .deinit = wpa_driver_nl80211_deinit,
    .get_capa = wpa_driver_nl80211_get_capa,
    .set_operstate = wpa_driver_nl80211_set_operstate,
    .set_supp_port = wpa_driver_nl80211_set_supp_port,
    .set_country = wpa_driver_nl80211_set_country,
    .set_ap = wpa_driver_nl80211_set_ap,
    .if_add = wpa_driver_nl80211_if_add,
    .if_remove = wpa_driver_nl80211_if_remove,
    .send_mlme = wpa_driver_nl80211_send_mlme,
    .get_hw_feature_data = wpa_driver_nl80211_get_hw_feature_data,
    .sta_add = wpa_driver_nl80211_sta_add,
    .sta_remove = wpa_driver_nl80211_sta_remove,
    .hapd_send_eapol = wpa_driver_nl80211_hapd_send_eapol,
#ifdef ANDROID_QCOM_PATCH
    .hapd_set_countermeasures = wpa_driver_nl80211_set_countermeasures,#endif
    .sta_set_flags = wpa_driver_nl80211_sta_set_flags,
#ifdef HOSTAPD
    .hapd_init = i802_init,
    .hapd_deinit = i802_deinit,
    .set_wds_sta = i802_set_wds_sta,#endif /* HOSTAPD */#if defined(HOSTAPD) || defined(CONFIG_AP)
    .get_seqnum = i802_get_seqnum,
    .flush = i802_flush,
    .read_sta_data = i802_read_sta_data,
    .get_inact_sec = i802_get_inact_sec,
    .sta_clear_stats = i802_sta_clear_stats,
    .set_rts = i802_set_rts,
    .set_frag = i802_set_frag,
    .set_tx_queue_params = i802_set_tx_queue_params,
    .set_sta_vlan = i802_set_sta_vlan,
    .sta_deauth = i802_sta_deauth,
    .sta_disassoc = i802_sta_disassoc,#endif /* HOSTAPD || CONFIG_AP */
    .set_freq = i802_set_freq,
    .send_action = wpa_driver_nl80211_send_action,
    .send_action_cancel_wait = wpa_driver_nl80211_send_action_cancel_wait,
    .remain_on_channel = wpa_driver_nl80211_remain_on_channel,
    .cancel_remain_on_channel =
    wpa_driver_nl80211_cancel_remain_on_channel,
    .probe_req_report = wpa_driver_nl80211_probe_req_report,
    .deinit_ap = wpa_driver_nl80211_deinit_ap,
    .resume = wpa_driver_nl80211_resume,
    .send_ft_action = nl80211_send_ft_action,
    .signal_monitor = nl80211_signal_monitor,
    .signal_poll = nl80211_signal_poll,
    .send_frame = nl80211_send_frame,
    .shared_freq = wpa_driver_nl80211_shared_freq,
    .set_param = nl80211_set_param,
    .get_radio_name = nl80211_get_radio_name,
    .add_pmkid = nl80211_add_pmkid,
    .remove_pmkid = nl80211_remove_pmkid,
    .flush_pmkid = nl80211_flush_pmkid,
    .set_rekey_info = nl80211_set_rekey_info,
    .poll_client = nl80211_poll_client,
    .set_p2p_powersave = nl80211_set_p2p_powersave,
#ifdef CONFIG_TDLS
    .send_tdls_mgmt = nl80211_send_tdls_mgmt,
    .tdls_oper = nl80211_tdls_oper,#endif /* CONFIG_TDLS */#ifdef ANDROID_P2P
    .set_noa = wpa_driver_set_p2p_noa,#endif#ifdef ANDROID
    .driver_cmd = wpa_driver_nl80211_driver_cmd, //处理DRIVER开头的命令#endif};

ps：driver_cmd用于处理DRIVER的命令，调用流程如下：

wpa_supplicant_ctrl_iface_process-> (根据命令字符串调用对应的函数)
wpa_supplicant_driver_cmd->wpa_drv_driver_cmd->wpa_s->driver->driver_cmd->wpa_driver_nl80211_driver_cmd -> (User)
...
cfg80211...

3.2 kernel态实现

Kernel态实现的操作函数，实现代码见：net/wireless/wext-compat.c

static const iw_handler cfg80211_handlers[] = {
    [IW_IOCTL_IDX(SIOCGIWNAME)] = (iw_handler) cfg80211_wext_giwname,
    [IW_IOCTL_IDX(SIOCSIWFREQ)] = (iw_handler) cfg80211_wext_siwfreq,
    [IW_IOCTL_IDX(SIOCGIWFREQ)] = (iw_handler) cfg80211_wext_giwfreq,
    [IW_IOCTL_IDX(SIOCSIWMODE)] = (iw_handler) cfg80211_wext_siwmode,
    [IW_IOCTL_IDX(SIOCGIWMODE)] = (iw_handler) cfg80211_wext_giwmode,
    [IW_IOCTL_IDX(SIOCGIWRANGE)]    = (iw_handler) cfg80211_wext_giwrange,
    [IW_IOCTL_IDX(SIOCSIWAP)]   = (iw_handler) cfg80211_wext_siwap,
    [IW_IOCTL_IDX(SIOCGIWAP)]   = (iw_handler) cfg80211_wext_giwap,
    [IW_IOCTL_IDX(SIOCSIWMLME)] = (iw_handler) cfg80211_wext_siwmlme,
    [IW_IOCTL_IDX(SIOCSIWSCAN)] = (iw_handler) cfg80211_wext_siwscan,
    [IW_IOCTL_IDX(SIOCGIWSCAN)] = (iw_handler) cfg80211_wext_giwscan,
    [IW_IOCTL_IDX(SIOCSIWESSID)]    = (iw_handler) cfg80211_wext_siwessid,
    [IW_IOCTL_IDX(SIOCGIWESSID)]    = (iw_handler) cfg80211_wext_giwessid,
    [IW_IOCTL_IDX(SIOCSIWRATE)] = (iw_handler) cfg80211_wext_siwrate,
    [IW_IOCTL_IDX(SIOCGIWRATE)] = (iw_handler) cfg80211_wext_giwrate,
    [IW_IOCTL_IDX(SIOCSIWRTS)]  = (iw_handler) cfg80211_wext_siwrts,
    [IW_IOCTL_IDX(SIOCGIWRTS)]  = (iw_handler) cfg80211_wext_giwrts,
    [IW_IOCTL_IDX(SIOCSIWFRAG)] = (iw_handler) cfg80211_wext_siwfrag,
    [IW_IOCTL_IDX(SIOCGIWFRAG)] = (iw_handler) cfg80211_wext_giwfrag,
    [IW_IOCTL_IDX(SIOCSIWTXPOW)]    = (iw_handler) cfg80211_wext_siwtxpower,
    [IW_IOCTL_IDX(SIOCGIWTXPOW)]    = (iw_handler) cfg80211_wext_giwtxpower,
    [IW_IOCTL_IDX(SIOCSIWRETRY)]    = (iw_handler) cfg80211_wext_siwretry,
    [IW_IOCTL_IDX(SIOCGIWRETRY)]    = (iw_handler) cfg80211_wext_giwretry,
    [IW_IOCTL_IDX(SIOCSIWENCODE)]   = (iw_handler) cfg80211_wext_siwencode,
    [IW_IOCTL_IDX(SIOCGIWENCODE)]   = (iw_handler) cfg80211_wext_giwencode,
    [IW_IOCTL_IDX(SIOCSIWPOWER)]    = (iw_handler) cfg80211_wext_siwpower,
    [IW_IOCTL_IDX(SIOCGIWPOWER)]    = (iw_handler) cfg80211_wext_giwpower,
    [IW_IOCTL_IDX(SIOCSIWGENIE)]    = (iw_handler) cfg80211_wext_siwgenie,
    [IW_IOCTL_IDX(SIOCSIWAUTH)] = (iw_handler) cfg80211_wext_siwauth,
    [IW_IOCTL_IDX(SIOCGIWAUTH)] = (iw_handler) cfg80211_wext_giwauth,
    [IW_IOCTL_IDX(SIOCSIWENCODEEXT)]= (iw_handler) cfg80211_wext_siwencodeext,
    [IW_IOCTL_IDX(SIOCSIWPMKSA)]    = (iw_handler) cfg80211_wext_siwpmksa,
};const struct iw_handler_def cfg80211_wext_handler = {
    .num_standard       = ARRAY_SIZE(cfg80211_handlers), 
    .standard       = cfg80211_handlers,
    .get_wireless_stats = cfg80211_wireless_stats,
};

4.用户态和kernel态交互

4.1初始化

首先说明下用户态和kernel态交互的方式，如下所述：

a.用户态向kernel态发送请求时，通过ioctl来实现

b.kernel态向用户态发送事件通知，通过netlink实现

交互的初始化有两部分组成:nl80211_global_init和wpa_driver_nl80211_init方法。以上a/b两点中ioctl和netlink是在nl80211_global_init方法中创建。

(1) nl80211_global_init方法

因为在”2.保存驱动接口”，select_driver方法中调用了global_init方法(会根据用户态的结构体wpa_driver_nl80211_ops中查找对应方法，即nl80211_global_init)。

static void * nl80211_global_init(void)
{    struct nl80211_global *global;    struct netlink_config *cfg;    global = os_zalloc(sizeof(*global));    if (global == NULL)        return NULL;    global->ioctl_sock = -1;
    dl_list_init(&global->interfaces);    global->if_add_ifindex = -1;

    cfg = os_zalloc(sizeof(*cfg)); 
    if (cfg == NULL)        goto err;

    cfg->ctx = global;
    cfg->newlink_cb = wpa_driver_nl80211_event_rtm_newlink;
    cfg->dellink_cb = wpa_driver_nl80211_event_rtm_dellink;    global->netlink = netlink_init(cfg); //初始化netlink,并注册事件接收函数 
    if (global->netlink == NULL) {     
        os_free(cfg);        goto err;
    }  

    if (wpa_driver_nl80211_init_nl_global(global) < 0)                                                                                                                   
        goto err;// 此global->ioctl_sock用作为ioctl命令的fd
    global->ioctl_sock = socket(PF_INET, SOCK_DGRAM, 0);    if (global->ioctl_sock < 0) {      
        perror("socket(PF_INET,SOCK_DGRAM)");        goto err;
    }  

    return global;

err:
    nl80211_global_deinit(global);    return NULL;
}

在nl80211_global_init方法中，有两条关键语句：

(a)// 初始化netlink,并注册事件接收函数 global->netlink = netlink_init(cfg); 

(b)// 此global->ioctl_sock用作为ioctl命令的fdglobal->ioctl_sock = socket(PF_INET, SOCK_DGRAM, 0);

分析以上两句：

(a)netlink_init方法中创建了一个socket，并添加到eloop_run方法中的rfds中。用于从kernel态发送事件给用户态

netlink->sock =->sock, netlink_receive, netlink,NULL);

(b)该socket用于从用户态发送请求给kernel态

(2)wpa_driver_nl80211_init方法

在wpa_supplicant_init_iface方法中有语句：

if (wpa_supplicant_set_driver(wpa_s, driver) < 0)    
 return -1; 
wpa_s->drv_priv = wpa_drv_init(wpa_s, wpa_s->ifname);

在设置完驱动后，会调用wpa_drv_init方法，其方法体中会调用init2方法，即wpa_driver_nl80211_init。该方法用来Initialize nl80211 driver interface.

4.2 用户态和kernel态交互之ioctl实现

在用户态可简单执行一个ioctl(fd,cmd,...)命令即可。

先看下socket.c文件

/*
 *  Socket files have a set of 'special' operations as well as the generic file ones. These don't appear in the operation structures but are done directly via the socketcall() multiplexor. */static const struct file_operations socket_file_ops = {
    .owner =    THIS_MODULE,
    .llseek =   no_llseek,
    .aio_read = sock_aio_read,
    .aio_write =    sock_aio_write,
    .poll =     sock_poll,
    .unlocked_ioctl = sock_ioctl, // 这个就是被执行的ioctl #ifdef CONFIG_COMPAT
    .compat_ioctl = compat_sock_ioctl,#endif
    .mmap =     sock_mmap,
    .open =     sock_no_open,   /* special open code to disallow open via /proc */
    .release =  sock_close,
    .fasync =   sock_fasync,
    .sendpage = sock_sendpage,
    .splice_write = generic_splice_sendpage,
    .splice_read =  sock_splice_read,
};

从用户态调用sock_ioctl到kernel态调用iw_handler的执行流程如下：

sock_ioctl-> (kernel/net/socket.c)
  dev_ioctl-> (kernel/net/core/dev.c)
    下面的方法都在/net/wireless/wext-core.c中
    wext_handle_ioctl-> (把执行结果从kernel态copy到用户态)
      wext_ioctl_dispatch->(参数包括cmd/ioctl_standard_call/ioctl_private_call)
        wireless_process_ioctl->
          get_handler->  (根据cmd来判断调用standard或是private，即ioctl_standard_call或是ioctl_private_call方法)
      ioctl_standard_call (执行cmd指定的iw_handler<cfg80211_handlers中定义的>，并返回结果)

这样就完成了”通过ioctl，用户态向kernel态发送请求”。

这个流程的代码稍后贴出。

sock_ioctl