WIFI串連流程

Wifi 串連部分

 

當使用者選擇一個AP時會彈出一個AP參數配置對話方塊，此對話方塊會顯示當前選擇的AP訊號強度，若此AP設定了密碼則需要使用者輸入密碼才能登入。WifiSettings中的 onPreferenceTreeClick會被調用          @Override

    public boolean onPreferenceTreeClick(PreferenceScreen screen, Preference preference) {

         //點擊AP響應函數

        if (preference instanceof AccessPoint) {

            mSelected = (AccessPoint) preference;

            showDialog(mSelected, false);

        } else if (preference == mAddNetwork) {

            mSelected = null;

            showDialog(null, true);

        } else if (preference == mNotifyOpenNetworks) {

            Secure.putInt(getContentResolver(),

                    Secure.WIFI_NETWORKS_AVAILABLE_NOTIFICATION_ON,

                    mNotifyOpenNetworks.isChecked() ? 1 : 0);

        } else {

            return super.onPreferenceTreeClick(screen, preference);

        }

        return true;

    }

 

使用者配置好之後點擊連線按鍵，onClick函數會被調用。

public void onClick(DialogInterface dialogInterface, int button) {

          //點擊連線按鍵的響應函數

        if (button == WifiDialog.BUTTON_FORGET && mSelected != null) {

            forget(mSelected.networkId);

        } else if (button == WifiDialog.BUTTON_SUBMIT && mDialog != null) {

            WifiConfiguration config = mDialog.getConfig();

 

            if (config == null) {

                if (mSelected != null && !requireKeyStore(mSelected.getConfig())) {

                    connect(mSelected.networkId);

                }

            } else if (config.networkId != -1) {

                if (mSelected != null) {

                    mWifiManager.updateNetwork(config);

                    saveNetworks();

                }

            } else {

                int networkId = mWifiManager.addNetwork(config);

                if (networkId != -1) {

                    mWifiManager.enableNetwork(networkId, false);

                    config.networkId = networkId;

                    if (mDialog.edit || requireKeyStore(config)) {

                        saveNetworks();

                    } else {

                        connect(networkId);

                    }

                }

            }

        }

 

串連請求部分

一.Settings的connect函數響應串連，更新網路儲存配置，更新設定當前選擇的優先順序最高，並

    儲存。然後通過enableNetwork使得其他網路不可用來進行串連。最後調用WifiManager的

      reconnect函數串連當前選擇的網路。

二.WifiManager的reconnect函數通過AIDL的Binder機制，調用WifiService的reconnect函數

三.然後會調用 WifiStateTracker的reconnectCommand函數，通過JNI（android_net_wifi_Wifi)的             

      android_net_wifi_reconnectCommand 函數向WPA_WPASUPPLICANT發送 RECONNECT命令。

四. android_net_wifi_Wifi通過 doCommand(命令名，響應緩衝，響應緩衝大小)調用wifi.c中的

      wifi_command函數來發送命令。

五.最後通過 wpa_ctrl的wpa_ctrl_request函數向控制通道發送串連命令。

返回請求部分

六.當串連上之後WPA_SUPPLICANT會向控制通道發送串連成功命令。wifi.c的

      wifi_wait_for_event函數阻塞調用並返回這個命令的字串（CONNECTED）.

七.而後WifiMonitor會被執行來處理這個事件，WifiMonitor 再調用 WifiStateTracker的

     notifyStateChange,WifiStateTracker 則接著會往自身發送 EVENT_DHCP_START 訊息來啟動

    DHCP 去擷取 IP 位址,然後廣播NETWORK_STATE_CHANGED_ACTION訊息，最後由

    WifiSettings類來響應，改變狀態和介面資訊。

關鍵函數功能介紹

一.connect函數功能

  1.updateNetwork：updateNetwork(config)會將當前選擇串連的AP配置資訊

   資訊傳遞進去，配置資訊有（網路ID等）。如果網路ID為-1則重新添加網路設定，然後向

   wpa_supplicant 發送SET_NETWORK命令（即通過這個網路ID設定其他一些相關資訊，設定

   SSID，密碼等）如果網路設定不為－1則直接執行後面步驟即發送SET_NETWORK命令。

  2.saveNetwork:告訴supplicant儲存當前網路設定並更新列表。SaveNetwork會調用WifiService的

     saveConfiguration向wpa_supplicant發送SAVE_CONFIG命令儲存當前網路設定資訊，

    如果返回false，則向wpa_supplicant重新發送RECONFIGURE命令擷取配置資訊，如果擷取信

 

    息成功後，會Intent一個  NETWORK_IDS_CHANGED_ACTION事件WifiSettings會註冊接受

    這個 時間並更新列表。

  3.enableNetwork函數，向系統擷取介面名並使得該介面有效。由於之前傳遞的disableOthers

    為true則向wpa_supplicant發送SELECT_NETWORK（如果傳遞的為false則發送                

     ENABLE_NETWORK命令），

  4.reconnect函數：串連AP

 

二.reconnect函數功能：connect函數會調用WifiManager的reconnect然後通過Binder機制調用

   WifiService的reconnect，再由WifiStateTracke調用WifiNative向wpa_supplicant發送

   RECONNECT命令去串連網路，當串連上wpa_supplicant之後會向控制通道發送串連成功的命  

   令，

   wifi_wait_for_event函數阻塞等待該事件的發生，並返回這個命令的字串（CONNECTED）

  

三.android_net_wifi_Wifi函數的doCommand函數會調用wifi.c的wifi_command函數將上層的命

   令向wpa_supplicant發送。

  

四.wifi_wait_for_event函數以阻塞的方式，等待控制通道傳遞的事件。當有事件傳遞過來的時候

   該函數會通過wpa_ctrl的wpa_ctrl_recv函數讀取該事件，並以字串形式返回該事件名。

   int wifi_wait_for_event(char *buf, size_t buflen)

{

                       .......

    result = wpa_ctrl_recv(monitor_conn, buf, &nread);

    if (result < 0) {

        LOGD("wpa_ctrl_recv failed: %s/n", strerror(errno));

        strncpy(buf, WPA_EVENT_TERMINATING " - recv error", buflen-1);

        buf[buflen-1] = '/0';

        return strlen(buf);

    }

    buf[nread] = '/0';

    /* LOGD("wait_for_event: result=%d nread=%d string=/"%s/"/n", result, nread, buf); */

    /* Check for EOF on the socket */

    if (result == 0 && nread == 0) {

        /* Fabricate an event to pass up */

        LOGD("Received EOF on supplicant socket/n");

        strncpy(buf, WPA_EVENT_TERMINATING " - signal 0 received", buflen-1);

        buf[buflen-1] = '/0';

        return strlen(buf);

    }

    /*

     * Events strings are in the format

     *

     *     <N>CTRL-EVENT-XXX

     *

     * where N is the message level in numerical form (0=VERBOSE, 1=DEBUG,

     * etc.) and XXX is the event name. The level information is not useful

     * to us, so strip it off.

     */

    if (buf[0] == '<') {

        char *match = strchr(buf, '>');

        if (match != NULL) {

            nread -= (match+1-buf);

            memmove(buf, match+1, nread+1);

        }

    }

    return nread;

}

 

五.wpa_ctrl_request，通過socket方式向wpa_supplicant發送命令，以select模式阻塞在

   wpa_supplicant發送和接收。

int wpa_ctrl_request(struct wpa_ctrl *ctrl, const char *cmd, size_t cmd_len，char *reply, size_t *reply_len,void (*msg_cb)(char *msg, size_t len))

{

         .......

                   res = select(ctrl->s + 1, &rfds, NULL, NULL, &tv);

                   if (FD_ISSET(ctrl->s, &rfds)) {

                            res = recv(ctrl->s, reply, *reply_len, 0);

                            if (res < 0)

                                     return res;

                            if (res > 0 && reply[0] == '<') {

                                     /* This is an unsolicited message from

                                      * wpa_supplicant, not the reply to the

                                      * request. Use msg_cb to report this to the

                                      * caller. */

                                     if (msg_cb) {

                                               /* Make sure the message is nul

                                                * terminated. */

                                               if ((size_t) res == *reply_len)

                                                        res = (*reply_len) - 1;

                                               reply[res] = '/0';

                                               msg_cb(reply, res);

                                     }

                                     continue;

                            }

                            *reply_len = res;

                            break;

                   } else {

                            return -2;

                   }

         }

         return 0;

}

 

六.WifiMonitor 維護一個監視線程分發處理底層返回上來的事件

 void handleEvent(int event, String remainder) {

            switch (event) {

                case DISCONNECTED:

                    handleNetworkStateChange(NetworkInfo.DetailedState.DISCONNECTED, remainder);

                    break;

                case CONNECTED:

                    handleNetworkStateChange(NetworkInfo.DetailedState.CONNECTED, remainder);

                    break;

                case SCAN_RESULTS:

                    mWifiStateTracker.notifyScanResultsAvailable();

                    break;

                case UNKNOWN:

                    break;

            }

        }

此時返回的事件是CONNECTED因此 handleNetworkStateChange會被調用，驗證一下BSSID,重新獲得networkId

,然後調用WifiStateTracke的notifyStateChange通知狀態改變了的訊息（EVENT_NETWORK_STATE_CHANGED）

接著處理這個訊息，會移除可用網路通告，然後通過 configureInterface()的動態擷取IP地址。最後

發送一個NETWORK_STATE_CHANGED_ACTION Intent，WifiSetings註冊了此Intent因此會響應該它。由updateConnectionState函數響應。

七.updateConnectionState 擷取串連資訊，更新列表狀態，設定為Connected,然後設定當前網路為可用狀態

  

   private void updateConnectionState(DetailedState state) {

        /* sticky broadcasts can call this when wifi is disabled */

        if (!mWifiManager.isWifiEnabled()) {

            mScanner.pause();

            return;

        }

 

        if (state == DetailedState.OBTAINING_IPADDR) {

            mScanner.pause();

        } else {

            mScanner.resume();

        }

 

        mLastInfo = mWifiManager.getConnectionInfo();

        if (state != null) {

            mLastState = state;

        }

 

        for (int i = mAccessPoints.getPreferenceCount() - 1; i >= 0; --i) {

            ((AccessPoint) mAccessPoints.getPreference(i)).update(mLastInfo, mLastState);

        }

 

        if (mResetNetworks && (state == DetailedState.CONNECTED ||

                state == DetailedState.DISCONNECTED || state == DetailedState.FAILED)) {

            updateAccessPoints();

            enableNetworks();

        }

    }

 

 

 流程圖對應的原始碼路徑為：

 WifiEnabler,WifiSettings對應的路徑如下：

 froyo/packages/apps/Settings/src/com/android/settings/

 

WifiManager,WifiMonitor,WifiStateTracker,WifiNative.對應的原始碼路徑如下：

froyo/frameworrks/base/wifi/java/android/net/wifi/

 

WifiService 對應代碼的位置

froyo/frameworks/base/services/java/com/android/server/

 

android_net_wifi_Wifi原始碼路徑如下：

froyo/frameworks/base/core/jni/

 

wifi_command,wifi_wait_for_envent原始碼路徑如下：

/hardware/libhardware_legacy/wifi/wifi.c

 

wpa_ctrl_原始碼路徑如下：

/external/wpa_supplicant/wpa_ctrl.c

 

wpa_supplicant原始碼路徑如下：

froyo/external/wpa_supplicant/