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fd global->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 = 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) < 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。
1 /* 2 * With an ioctl, arg may well be a user mode pointer, but we don't know 3 * what to do with it - that's up to the protocol still. 4 */ 5 6 static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg) 7 { 8 struct socket *sock; 9 struct sock *sk; 10 void __user *argp = (void __user *)arg; 11 int pid, err; 12 struct net *net; 13 14 sock = file->private_data; 15 sk = sock->sk; 16 net = sock_net(sk); 17 if (cmd >= SIOCDEVPRIVATE && cmd <= (SIOCDEVPRIVATE + 15)) { 18 err = dev_ioctl(net, cmd, argp); 19 } else 20 #ifdef CONFIG_WEXT_CORE 21 if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST) { 22 err = dev_ioctl(net, cmd, argp); 23 } else 24 #endif 25 switch (cmd) { 26 case FIOSETOWN: 27 case SIOCSPGRP: 28 err = -EFAULT; 29 if (get_user(pid, (int __user *)argp)) 30 break; 31 err = f_setown(sock->file, pid, 1); 32 break; 33 case FIOGETOWN: 34 case SIOCGPGRP: 35 err = put_user(f_getown(sock->file), 36 (int __user *)argp); 37 break; 38 case SIOCGIFBR: 39 case SIOCSIFBR: 40 case SIOCBRADDBR: 41 case SIOCBRDELBR: 42 err = -ENOPKG; 43 if (!br_ioctl_hook) 44 request_module("bridge"); 45 46 mutex_lock(&br_ioctl_mutex); 47 if (br_ioctl_hook) 48 err = br_ioctl_hook(net, cmd, argp); 49 mutex_unlock(&br_ioctl_mutex); 50 break; 51 case SIOCGIFVLAN: 52 case SIOCSIFVLAN: 53 err = -ENOPKG; 54 if (!vlan_ioctl_hook) 55 request_module("8021q"); 56 57 mutex_lock(&vlan_ioctl_mutex); 58 if (vlan_ioctl_hook) 59 err = vlan_ioctl_hook(net, argp); 60 mutex_unlock(&vlan_ioctl_mutex); 61 break; 62 case SIOCADDDLCI: 63 case SIOCDELDLCI: 64 err = -ENOPKG; 65 if (!dlci_ioctl_hook) 66 request_module("dlci"); 67 68 mutex_lock(&dlci_ioctl_mutex); 69 if (dlci_ioctl_hook) 70 err = dlci_ioctl_hook(cmd, argp); 71 mutex_unlock(&dlci_ioctl_mutex); 72 break; 73 default: 74 err = sock_do_ioctl(net, sock, cmd, arg); 75 break; 76 } 77 return err; 78 }