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 -;
        }
    }
// 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 ;
}

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 = -;
    dl_list_init(&global->interfaces);
    global->if_add_ifindex = -;

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

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 = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
......
eloop_register_read_sock(netlink->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) < )
    return -;
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。

 /*
  *    With an ioctl, arg may well be a user mode pointer, but we don't know
  *    what to do with it - that's up to the protocol still.
  */

 static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 {
     struct socket *sock;
     struct sock *sk;
     void __user *argp = (void __user *)arg;
     int pid, err;
     struct net *net;

     sock = file->private_data;
     sk = sock->sk;
     net = sock_net(sk);
     if (cmd >= SIOCDEVPRIVATE && cmd <= (SIOCDEVPRIVATE + )) {
         err = dev_ioctl(net, cmd, argp);
     } else
 #ifdef CONFIG_WEXT_CORE
     if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST) {
         err = dev_ioctl(net, cmd, argp);
     } else
 #endif
         switch (cmd) {
         case FIOSETOWN:
         case SIOCSPGRP:
             err = -EFAULT;
             if (get_user(pid, (int __user *)argp))
                 break;
             err = f_setown(sock->file, pid, );
             break;
         case FIOGETOWN:
         case SIOCGPGRP:
             err = put_user(f_getown(sock->file),
                        (int __user *)argp);
             break;
         case SIOCGIFBR:
         case SIOCSIFBR:
         case SIOCBRADDBR:
         case SIOCBRDELBR:
             err = -ENOPKG;
             if (!br_ioctl_hook)
                 request_module("bridge");

             mutex_lock(&br_ioctl_mutex);
             if (br_ioctl_hook)
                 err = br_ioctl_hook(net, cmd, argp);
             mutex_unlock(&br_ioctl_mutex);
             break;
         case SIOCGIFVLAN:
         case SIOCSIFVLAN:
             err = -ENOPKG;
             if (!vlan_ioctl_hook)
                 request_module("8021q");

             mutex_lock(&vlan_ioctl_mutex);
             if (vlan_ioctl_hook)
                 err = vlan_ioctl_hook(net, argp);
             mutex_unlock(&vlan_ioctl_mutex);
             break;
         case SIOCADDDLCI:
         case SIOCDELDLCI:
             err = -ENOPKG;
             if (!dlci_ioctl_hook)
                 request_module("dlci");

             mutex_lock(&dlci_ioctl_mutex);
             if (dlci_ioctl_hook)
                 err = dlci_ioctl_hook(cmd, argp);
             mutex_unlock(&dlci_ioctl_mutex);
             break;
         default:
             err = sock_do_ioctl(net, sock, cmd, arg);
             break;
         }
     return err;
 }

sock_ioctl

 /**
  *    dev_ioctl    -    network device ioctl
  *    @net: the applicable net namespace
  *    @cmd: command to issue
  *    @arg: pointer to a struct ifreq in user space
  *
  *    Issue ioctl functions to devices. This is normally called by the
  *    user space syscall interfaces but can sometimes be useful for
  *    other purposes. The return value is the return from the syscall if
  *    positive or a negative errno code on error.
  */

 int dev_ioctl(struct net *net, unsigned int cmd, void __user *arg)
 {
     struct ifreq ifr;
     int ret;
     char *colon;

     /* One special case: SIOCGIFCONF takes ifconf argument
        and requires shared lock, because it sleeps writing
        to user space.
      */

     if (cmd == SIOCGIFCONF) {
         rtnl_lock();
         ret = dev_ifconf(net, (char __user *) arg);
         rtnl_unlock();
         return ret;
     }
     if (cmd == SIOCGIFNAME)
         return dev_ifname(net, (struct ifreq __user *)arg);

     if (copy_from_user(&ifr, arg, sizeof(struct ifreq)))
         return -EFAULT;

     ifr.ifr_name[IFNAMSIZ-] = ;

     colon = strchr(ifr.ifr_name, ':');
     if (colon)
         *colon = ;

     /*
      *    See which interface the caller is talking about.
      */

     switch (cmd) {
     /*
      *    These ioctl calls:
      *    - can be done by all.
      *    - atomic and do not require locking.
      *    - return a value
      */
     case SIOCGIFFLAGS:
     case SIOCGIFMETRIC:
     case SIOCGIFMTU:
     case SIOCGIFHWADDR:
     case SIOCGIFSLAVE:
     case SIOCGIFMAP:
     case SIOCGIFINDEX:
     case SIOCGIFTXQLEN:
         dev_load(net, ifr.ifr_name);
         rcu_read_lock();
         ret = dev_ifsioc_locked(net, &ifr, cmd);
         rcu_read_unlock();
         if (!ret) {
             if (colon)
                 *colon = ':';
             if (copy_to_user(arg, &ifr,
                      sizeof(struct ifreq)))
                 ret = -EFAULT;
         }
         return ret;

     case SIOCETHTOOL:
         dev_load(net, ifr.ifr_name);
         rtnl_lock();
         ret = dev_ethtool(net, &ifr);
         rtnl_unlock();
         if (!ret) {
             if (colon)
                 *colon = ':';
             if (copy_to_user(arg, &ifr,
                      sizeof(struct ifreq)))
                 ret = -EFAULT;
         }
         return ret;

     /*
      *    These ioctl calls:
      *    - require superuser power.
      *    - require strict serialization.
      *    - return a value
      */
     case SIOCGMIIPHY:
     case SIOCGMIIREG:
     case SIOCSIFNAME:
         if (!capable(CAP_NET_ADMIN))
             return -EPERM;
         dev_load(net, ifr.ifr_name);
         rtnl_lock();
         ret = dev_ifsioc(net, &ifr, cmd);
         rtnl_unlock();
         if (!ret) {
             if (colon)
                 *colon = ':';
             if (copy_to_user(arg, &ifr,
                      sizeof(struct ifreq)))
                 ret = -EFAULT;
         }
         return ret;

     /*
      *    These ioctl calls:
      *    - require superuser power.
      *    - require strict serialization.
      *    - do not return a value
      */
     case SIOCSIFFLAGS:
     case SIOCSIFMETRIC:
     case SIOCSIFMTU:
     case SIOCSIFMAP:
     case SIOCSIFHWADDR:
     case SIOCSIFSLAVE:
     case SIOCADDMULTI:
     case SIOCDELMULTI:
     case SIOCSIFHWBROADCAST:
     case SIOCSIFTXQLEN:
     case SIOCSMIIREG:
     case SIOCBONDENSLAVE:
     case SIOCBONDRELEASE:
     case SIOCBONDSETHWADDR:
     case SIOCBONDCHANGEACTIVE:
     case SIOCBRADDIF:
     case SIOCBRDELIF:
     case SIOCSHWTSTAMP:
         if (!capable(CAP_NET_ADMIN))
             return -EPERM;
         /* fall through */
     case SIOCBONDSLAVEINFOQUERY:
     case SIOCBONDINFOQUERY:
         dev_load(net, ifr.ifr_name);
         rtnl_lock();
         ret = dev_ifsioc(net, &ifr, cmd);
         rtnl_unlock();
         return ret;

     case SIOCGIFMEM:
         /* Get the per device memory space. We can add this but
          * currently do not support it */
     case SIOCSIFMEM:
         /* Set the per device memory buffer space.
          * Not applicable in our case */
     case SIOCSIFLINK:
         return -ENOTTY;

     /*
      *    Unknown or private ioctl.
      */
     default:
         if (cmd == SIOCWANDEV ||
             (cmd >= SIOCDEVPRIVATE &&
              cmd <= SIOCDEVPRIVATE + )) {
             dev_load(net, ifr.ifr_name);
             rtnl_lock();
             ret = dev_ifsioc(net, &ifr, cmd);
             rtnl_unlock();
             if (!ret && copy_to_user(arg, &ifr,
                          sizeof(struct ifreq)))
                 ret = -EFAULT;
             return ret;
         }
         /* Take care of Wireless Extensions */
         if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST)
             return wext_handle_ioctl(net, &ifr, cmd, arg);  //执行wext_handle_ioctl方法
         return -ENOTTY;
     }
 }

dev_ioctl

int wext_handle_ioctl(struct net *net, struct ifreq *ifr, unsigned int cmd,
              void __user *arg)
{
    struct iw_request_info info = { .cmd = cmd, .flags =  };
    int ret;

    ret = wext_ioctl_dispatch(net, ifr, cmd, &info,
                  ioctl_standard_call,
                  ioctl_private_call); //调用wext_ioctl_dispatch方法
    if (ret >=  &&
        IW_IS_GET(cmd) &&
        copy_to_user(arg, ifr, sizeof(struct iwreq)))  //将执行结果从kernel态copy到用户态
        return -EFAULT;

    return ret;
}

wext_handle_ioctl

 /* entry point from dev ioctl */
 static int wext_ioctl_dispatch(struct net *net, struct ifreq *ifr,
                    unsigned int cmd, struct iw_request_info *info,
                    wext_ioctl_func standard,
                    wext_ioctl_func private)
 {
     int ret = wext_permission_check(cmd);

     if (ret)
         return ret;

     dev_load(net, ifr->ifr_name);
     rtnl_lock();
     ret = wireless_process_ioctl(net, ifr, cmd, info, standard, private); //调用wireless_process_ioctl方法
     rtnl_unlock();

     return ret;
 }

wext_ioctl_dispatch

 /*
  * Main IOCTl dispatcher.
  * Check the type of IOCTL and call the appropriate wrapper...
  */
 static int wireless_process_ioctl(struct net *net, struct ifreq *ifr,
                   unsigned int cmd,
                   struct iw_request_info *info,
                   wext_ioctl_func standard,
                   wext_ioctl_func private)
 {
     struct iwreq *iwr = (struct iwreq *) ifr;
     struct net_device *dev;
     iw_handler    handler;

     /* Permissions are already checked in dev_ioctl() before calling us.
      * The copy_to/from_user() of ifr is also dealt with in there */

     /* Make sure the device exist */
     if ((dev = __dev_get_by_name(net, ifr->ifr_name)) == NULL)
         return -ENODEV;

     /* A bunch of special cases, then the generic case...
      * Note that 'cmd' is already filtered in dev_ioctl() with
      * (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST) */
     if (cmd == SIOCGIWSTATS)
         return standard(dev, iwr, cmd, info,
                 &iw_handler_get_iwstats);

 #ifdef CONFIG_WEXT_PRIV
     if (cmd == SIOCGIWPRIV && dev->wireless_handlers)
         return standard(dev, iwr, cmd, info,
                 iw_handler_get_private);
 #endif

     /* Basic check */
     if (!netif_device_present(dev))
         return -ENODEV;

     /* New driver API : try to find the handler */
     handler = get_handler(dev, cmd);  //调用get_handler
     if (handler) {
         /* Standard and private are not the same */
         if (cmd < SIOCIWFIRSTPRIV)
             return standard(dev, iwr, cmd, info, handler);
         else if (private)
             return private(dev, iwr, cmd, info, handler);
     }
     /* Old driver API : call driver ioctl handler */
     if (dev->netdev_ops->ndo_do_ioctl)
         return dev->netdev_ops->ndo_do_ioctl(dev, ifr, cmd);
     return -EOPNOTSUPP;
 }

wireless_process_ioctl

 /*
  * Wrapper to call a standard Wireless Extension handler.
  * We do various checks and also take care of moving data between
  * user space and kernel space.
  */
 static int ioctl_standard_call(struct net_device *    dev,
                    struct iwreq        *iwr,
                    unsigned int        cmd,
                    struct iw_request_info    *info,
                    iw_handler        handler)
 {
     const struct iw_ioctl_description *    descr;
     int                    ret = -EINVAL;

     /* Get the description of the IOCTL */
     if (IW_IOCTL_IDX(cmd) >= standard_ioctl_num)
         return -EOPNOTSUPP;
     descr = &(standard_ioctl[IW_IOCTL_IDX(cmd)]);

     /* Check if we have a pointer to user space data or not */
     if (descr->header_type != IW_HEADER_TYPE_POINT) {

         /* No extra arguments. Trivial to handle */
         ret = handler(dev, info, &(iwr->u), NULL);

         /* Generate an event to notify listeners of the change */
         if ((descr->flags & IW_DESCR_FLAG_EVENT) &&
            ((ret == ) || (ret == -EIWCOMMIT)))
             wireless_send_event(dev, cmd, &(iwr->u), NULL);
     } else {
         ret = ioctl_standard_iw_point(&iwr->u.data, cmd, descr,
                           handler, dev, info);
     }

     /* Call commit handler if needed and defined */
     if (ret == -EIWCOMMIT)
         ret = call_commit_handler(dev);

     /* Here, we will generate the appropriate event if needed */

     return ret;
 }

ioctl_standard_call

4.3 用户态和kernel态交互之netlink实现

首先看netlink_init方法

struct netlink_data * netlink_init(struct netlink_config *cfg)
{
    struct netlink_data *netlink;
    struct sockaddr_nl local; 

    netlink = os_zalloc(sizeof(*netlink));
    if (netlink == NULL)
        return NULL;

    netlink->cfg = cfg;

    netlink->sock = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
    if (netlink->sock < ) {
        wpa_printf(MSG_ERROR, "netlink: Failed to open netlink "
               "socket: %s", strerror(errno));
        netlink_deinit(netlink);
        return NULL;
    }

    os_memset(&local, , sizeof(local));
    local.nl_family = AF_NETLINK;
    local.nl_groups = RTMGRP_LINK;
    if (bind(netlink->sock, (struct sockaddr *) &local, sizeof(local)) < )
    {
        wpa_printf(MSG_ERROR, "netlink: Failed to bind netlink "
               "socket: %s", strerror(errno));
        netlink_deinit(netlink);
        return NULL;
    }

    eloop_register_read_sock(netlink->sock, netlink_receive, netlink,
                 NULL);

    return netlink;
}

执行完netlink_init方法后，会通过eloop_register_read_sock方法将其中创建的socket以及callback方法注册到eloop_run方法中的rfds中，循环监听。一旦该socket有消息或事件变化，就执行netlink_receive方法。

static void netlink_receive(int sock, void *eloop_ctx, void *sock_ctx)
{
    struct netlink_data *netlink = eloop_ctx;
    char buf[];
    int left;
    struct sockaddr_nl from;
    socklen_t fromlen;
    struct nlmsghdr *h;
    int max_events = ;

try_again:
    fromlen = sizeof(from);
    left = recvfrom(sock, buf, sizeof(buf), MSG_DONTWAIT,
            (struct sockaddr *) &from, &fromlen); //从netlink读取事件
    if (left < ) {
        if (errno != EINTR && errno != EAGAIN)
            wpa_printf(MSG_INFO, "netlink: recvfrom failed: %s",
                   strerror(errno));
        return;
    }

    h = (struct nlmsghdr *) buf;
    while (NLMSG_OK(h, left)) {
        switch (h->nlmsg_type) {
        case RTM_NEWLINK:
            netlink_receive_link(netlink, netlink->cfg->newlink_cb,
                         h); //a
            break;
        case RTM_DELLINK:
            netlink_receive_link(netlink, netlink->cfg->dellink_cb,
                         h);  //b
            break;
        }

        h = NLMSG_NEXT(h, left);
    }

    if (left > ) {
        wpa_printf(MSG_DEBUG, "netlink: %d extra bytes in the end of "
               "netlink message", left);
    }

    if (--max_events > ) {
        /*
         * Try to receive all events in one eloop call in order to
         * limit race condition on cases where AssocInfo event, Assoc
         * event, and EAPOL frames are received more or less at the
         * same time. We want to process the event messages first
         * before starting EAPOL processing.
         */
        goto try_again;
    }
}

a/b中的方法调用，是在driver_nl80211.c中注册的，如下所示。

cfg->ctx = global;
cfg->newlink_cb = wpa_driver_nl80211_event_rtm_newlink;
cfg->dellink_cb = wpa_driver_nl80211_event_rtm_dellink;

这两个方法都会调用wpa_supplicant_event方法来处理。wpa_supplicant_event方法用来Report a driver event for wpa_supplicant。

所以这就完成了kernel向wpa_supplicant上传事件通知的过程了。

因此，kernel态向用户态发送事件通知(通过netlink)也已经分析完毕了。