一. wpa_supplicant配置編譯

將對應的平臺的wpa_supplicant包解壓改名為wpa_supplicant_8替換掉external下的wpa_supplicant_8目錄
執行:
source build/envsetup.sh
lunch qiyang_6dq-user

根據平臺定製所需要的wpa_supplican版本,
修改: BoardConfig.mk指明wpa_supplicant_8;指明所使用的驅動;指明wlan晶片對應的靜態庫
執行:
mmm hardware/Broadcom/wlan/bcmdhd/ wpa_supplicant_8_lib/
mmm external/wpa_supplicant_8
執行完之後把編譯好的wpa_supplican放入目標板並設定許可權為可執行.
結語: 除了修改BoardConfig.mk外, wpa_supplicant也定義了自己的android.config. 嚴格來說, android.cfg應該是唯一的編譯控制檔案. 但由於wlan晶片不同, wpa_supplicant可能還依賴其它模組.
Anadroid系統中, wpa_supplicant啟動是通過 “setprop ctrl.start wpa_supplicant” 來觸發init程序去fork一個子程序來完成的. wpa_supplicant在init配置檔案中定義為一個service.
路徑:qiyang-android442\device\fsl\qiyang_6dq\init.rc

service wpa_supplicant /system/bin/wpa_supplicant \
    -iwlan0 -Dnl80211 -c/data/misc/wifi/wpa_supplicant.conf \

最重要的是通過”-c” 引數指定的wpa_supplicant啟動配置檔案, 該配置檔案路徑名為/data/misc/wifi/wpa_supplicant.conf .
wpa_supplicant原始碼中包含一個啟動配置檔案的模板, 該檔案路徑為:external/wpa_supplicant_8/wpa_supplicant/wpa_supplicant.conf

network=
 
{
    ssid="example"
    proto=RSN
    key_mgmt=WPA-EAP
    pairwise=CCMP TKIP
    group=CCMP TKIP
    eap=TLS
    identity="[email protected]"
    ca_cert="/etc/cert/ca.pem"
    client_cert="/etc/cert/user.pem"
    private_key="/etc/cert/user.prv"
    private_key_passwd="password"
    priority=1
}

其中:
ctrl_interface=/var/run/wpa_supplicant 指明瞭控制介面unix域socket的檔名.

二. main函式分析

Android平臺中, main函式定義於main.c中.

int main(int argc, char *argv[])
{
    int c, i;
    struct wpa_interface *ifaces, *iface;
    int iface_count, exitcode = -1;
    struct wpa_params params;
    struct wpa_global *global;

    /* Android平臺中, 下面這個函式的實現在os_unix.c中. Android對其做了一些修改, 
     * 主要是許可權方面的設定防止某些情況下被破解者利用許可權漏洞以獲得root許可權. */
    if (os_program_init())
        return -1;

    os_memset(&params, 0, sizeof(params));
    params.wpa_debug_level = MSG_INFO;

    iface = ifaces = os_zalloc(sizeof(struct wpa_interface));
    if (ifaces == NULL)
        return -1;
    iface_count = 1;

    wpa_supplicant_fd_workaround(1);/*輸入輸出重定向到/dev/null裝置*/

    for (;;) {/*引數解析*/
        c = getopt(argc, argv,
               "b:Bc:C:D:de:f:g:G:hi:I:KLNo:O:p:P:qsTtuvW");
        if (c < 0)
            break;
        switch (c) {
        case 'b':
            iface->bridge_ifname = optarg;
            break;
        case 'B':
            params.daemonize++;
            break;
        case 'c':
            iface->confname = optarg;/*指定配置檔名.該引數賦值給了wpa_interface中的變數*/
            break;
        case 'C':
            iface->ctrl_interface = optarg;
            break;
        case 'D':
            iface->driver = optarg;/*指定driver名稱.該引數賦值給了wpa_interface中的變數*/
            break;
        case 'd':
    #ifdef CONFIG_NO_STDOUT_DEBUG
            printf("Debugging disabled with "
                   "CONFIG_NO_STDOUT_DEBUG=y build time "
                   "option.\n");
            goto out;
    #else /* CONFIG_NO_STDOUT_DEBUG */
            params.wpa_debug_level--;
            break;
    #endif /* CONFIG_NO_STDOUT_DEBUG */
        case 'e':
            params.entropy_file = optarg;/*指定初始隨機數檔案,用於後續隨機數的生成*/
            break;
    #ifdef CONFIG_DEBUG_FILE
        case 'f':
            params.wpa_debug_file_path = optarg;
            break;
    #endif /* CONFIG_DEBUG_FILE */
        case 'g':
            params.ctrl_interface = optarg;
            break;
        case 'G':
            params.ctrl_interface_group = optarg;
            break;
        case 'h':
            usage();
            exitcode = 0;
            goto out;
        case 'i':
            iface->ifname = optarg;/*指定網路裝置介面名, 本例是"wlan0"*/
            break;
        case 'I':
            iface->confanother = optarg;
            break;
        case 'K':
            params.wpa_debug_show_keys++;
            break;
        case 'L':
            license();
            exitcode = 0;
            goto out;
        case 'o':
            params.override_driver = optarg;
            break;
        case 'O':
            params.override_ctrl_interface = optarg;
            break;
        case 'p':
            iface->driver_param = optarg;
            break;
        case 'P':
            os_free(params.pid_file);
            params.pid_file = os_rel2abs_path(optarg);
            break;
        case 'q':
            params.wpa_debug_level++;
            break;
    #ifdef CONFIG_DEBUG_SYSLOG
        case 's':
            params.wpa_debug_syslog++;
            break;
    #endif /* CONFIG_DEBUG_SYSLOG */
    #ifdef CONFIG_DEBUG_LINUX_TRACING
        case 'T':
            params.wpa_debug_tracing++;
            break;
    #endif /*   CONFIG_DEBUG_LINUX_TRACING */
        case 't':
            params.wpa_debug_timestamp++;
            break;
    #ifdef CONFIG_DBUS
        case 'u':
            params.dbus_ctrl_interface = 1;
            break;
    #endif /* CONFIG_DBUS */
        case 'v':
            printf("%s\n", wpa_supplicant_version);
            exitcode = 0;
            goto out;
        case 'W':
            params.wait_for_monitor++;
            break;
        case 'N':
            iface_count++;
            iface = os_realloc_array(ifaces, iface_count,
                         sizeof(struct wpa_interface));
            if (iface == NULL)
                goto out;
            ifaces = iface;
            iface = &ifaces[iface_count - 1]; 
            os_memset(iface, 0, sizeof(*iface));
            break;
        default:
            usage();
            exitcode = 0;
            goto out;
        }
    }

    exitcode = 0;
    /*關鍵函式1:根據傳入的引數,建立並初始化一個wpa_global物件*/
    global = wpa_supplicant_init(&params);
    if (global == NULL) {
        wpa_printf(MSG_ERROR, "Failed to initialize wpa_supplicant");
        exitcode = -1;
        goto out;
    } else {
        wpa_printf(MSG_INFO, "Successfully initialized "
               "wpa_supplicant");
    }

    for (i = 0; exitcode == 0 && i < iface_count; i++) {
        struct wpa_supplicant *wpa_s;

        if ((ifaces[i].confname == NULL &&
             ifaces[i].ctrl_interface == NULL) ||
            ifaces[i].ifname == NULL) {
            if (iface_count == 1 && (params.ctrl_interface ||
                         params.dbus_ctrl_interface))
                break;
            usage();
            exitcode = -1;
            break;
        }
        /* 關鍵函式2:wpa_supplicant支援操作多個無線網路裝置,此處將它們一一新增到
         * wpa_supplicant中, wpa_supplicant內部將初始化這些裝置*/
        wpa_s = wpa_supplicant_add_iface(global, &ifaces[i]);
        if (wpa_s == NULL) {
            exitcode = -1;
            break;
        }
    #ifdef CONFIG_P2P
        if (wpa_s->global->p2p == NULL &&
            (wpa_s->drv_flags &
             WPA_DRIVER_FLAGS_DEDICATED_P2P_DEVICE) &&
            wpas_p2p_add_p2pdev_interface(wpa_s) < 0)
            exitcode = -1;
    #endif /* CONFIG_P2P */
    }

    /*Android平臺中, wpa_supplicant通過select或epoll方式實現多路I/O複用*/
    if (exitcode == 0)
        exitcode = wpa_supplicant_run(global);

    wpa_supplicant_deinit(global);

out:
    wpa_supplicant_fd_workaround(0);
    os_free(ifaces);
    os_free(params.pid_file);

os_program_deinit();

return exitcode;
}   

三. wpa_supplicant_init函式分析

路徑:external/wpa_supplicant_8/wpa_supplicant/wpa_supplicant.c

struct wpa_global * wpa_supplicant_init(struct wpa_params *params)
{
    struct wpa_global *global;
    int ret, i;

    if (params == NULL)
        return NULL;

#ifdef CONFIG_DRIVER_NDIS
    {
        void driver_ndis_init_ops(void);
        driver_ndis_init_ops();
    }
#endif /* CONFIG_DRIVER_NDIS */

#ifndef CONFIG_NO_WPA_MSG
    wpa_msg_register_ifname_cb(wpa_supplicant_msg_ifname_cb);/*設定全域性回撥函式*/
#endif /* CONFIG_NO_WPA_MSG */

    wpa_debug_open_file(params->wpa_debug_file_path);/*輸出日誌檔案設定*/
    if (params->wpa_debug_syslog)
        wpa_debug_open_syslog();
    if (params->wpa_debug_tracing) {
        ret = wpa_debug_open_linux_tracing();
        if (ret) {
            wpa_printf(MSG_ERROR,
                   "Failed to enable trace logging");
            return NULL;
        }
    }

    ret = eap_register_methods();/*1. 註冊EAP方法*/
    if (ret) {
        wpa_printf(MSG_ERROR, "Failed to register EAP methods");
        if (ret == -2)
            wpa_printf(MSG_ERROR, "Two or more EAP methods used "
                   "the same EAP type.");
        return NULL;
    }

    global = os_zalloc(sizeof(*global));/*建立一個wpa_global物件*/
    if (global == NULL)
        return NULL;

    /*初始化global中的其它引數*/
    dl_list_init(&global->p2p_srv_bonjour);
    dl_list_init(&global->p2p_srv_upnp);
    global->params.daemonize = params->daemonize;
    global->params.wait_for_monitor = params->wait_for_monitor;
    global->params.dbus_ctrl_interface = params->dbus_ctrl_interface;
    if (params->pid_file)
        global->params.pid_file = os_strdup(params->pid_file);
    if (params->ctrl_interface)
        global->params.ctrl_interface =
            os_strdup(params->ctrl_interface);
    if (params->ctrl_interface_group)
        global->params.ctrl_interface_group =
            os_strdup(params->ctrl_interface_group);
    if (params->override_driver)
        global->params.override_driver =
            os_strdup(params->override_driver);
    if (params->override_ctrl_interface)
        global->params.override_ctrl_interface =
            os_strdup(params->override_ctrl_interface);
    wpa_debug_level = global->params.wpa_debug_level =
        params->wpa_debug_level;
    wpa_debug_show_keys = global->params.wpa_debug_show_keys =
        params->wpa_debug_show_keys;
    wpa_debug_timestamp = global->params.wpa_debug_timestamp =
        params->wpa_debug_timestamp;

    wpa_printf(MSG_DEBUG, "wpa_supplicant v" VERSION_STR);
    /*2. 初始化事件迴圈機制*/
    if (eloop_init()) {
        wpa_printf(MSG_ERROR, "Failed to initialize event loop");
        wpa_supplicant_deinit(global);
        return NULL;
    }

    /*初始化隨機數相關資源, 用於提升後續隨機數生成的隨機性*/
    random_init(params->entropy_file);

    /*初始化全域性控制介面物件. */
    global->ctrl_iface = wpa_supplicant_global_ctrl_iface_init(global);
    if (global->ctrl_iface == NULL) {
        wpa_supplicant_deinit(global);
        return NULL;
    }

    /*初始化通知機制相關資源, 它和dbus有關.*/
    if (wpas_notify_supplicant_initialized(global)) {
        wpa_supplicant_deinit(global);
        return NULL;
    }

    /*wpa_drivers是全域性變數*/
    for (i = 0; wpa_drivers[i]; i++)
        global->drv_count++;
    if (global->drv_count == 0) {
        wpa_printf(MSG_ERROR, "No drivers enabled");
        wpa_supplicant_deinit(global);
        return NULL;
    }

    /*分配全域性driver wrapper上下文資訊陣列*/
    global->drv_priv = os_zalloc(global->drv_count * sizeof(void *));
    if (global->drv_priv == NULL) {
        wpa_supplicant_deinit(global);
        return NULL;
    }

#ifdef CONFIG_WIFI_DISPLAY
    if (wifi_display_init(global) < 0) {
        wpa_printf(MSG_ERROR, "Failed to initialize Wi-Fi Display");
        wpa_supplicant_deinit(global);
        return NULL;
    }
#endif /* CONFIG_WIFI_DISPLAY */

    return global;
}

wpa_supplicant_init函式的主要功能是初始化wpa_global以及一些與整個程式相關的資源, 包括隨機數資源, eloop事件迴圈機制以及設定訊息全域性回撥函式.這裡的回撥函式有兩個.:
wpa_msg_get_ifname_func: 某些輸出資訊中需要打印出網絡卡介面名. 該回調函式用於獲取網絡卡介面名.
wpa_msg_cb_func:特殊處理, 把輸出資訊發給客戶端進行處理.

1. wpa_debug.c分析

void wpa_msg_register_cb(wpa_msg_cb_func func)
{
    wpa_msg_cb = func;/*wpa_msg_cb的實現函式是wpa_supplicant_ctrl_ifname_msg_cb, 他將輸出資訊傳送給客戶端*/
}


static wpa_msg_get_ifname_func wpa_msg_ifname_cb = NULL;/*wpa_msg_ifname_cb用於獲取無線網絡卡介面;wpa_supplicant的實現函式為wpa_supplicant_msg_ifname_cb*/

void wpa_msg_register_ifname_cb(wpa_msg_get_ifname_func func)
{
    wpa_msg_ifname_cb = func;
}

後面再來看wpa_supplicant_init中列出的三個關鍵點.