Android下實現(xiàn)非啟動界面Wifi連接

1、.Android下實現(xiàn)非啟動界面Wifi連接Android的網絡功能和一般的linux并無太大的區(qū)別，我原來以為在Android上連接網絡和普通的linux連接網絡沒有很大區(qū)別，事實上區(qū)別還是有一些的。由于工程的需要，我的目的是在Android的界面沒有啟動之前連接wifi，于是本來的期待是直接在init.rc中參加一些腳本調用即可，但研究了一會兒發(fā)現(xiàn)沒有那么簡單。首先要感謝anly_junbaidu貼吧的幾篇博文，從 :/hi.baidu /anly_jun/blog/item/8ecb92d593d144cf50da4b6e.html開場，一共有七篇關于Android Wifi模塊分析，其

2、中有大量博主自己使用UML工具畫的調用講解，對于理解Android Wifi工作機制還是有很用的。其中最重要的是下面這幾幅圖。轉自 :/hi.baidu /anly_jun/blog/item/65e26e117e09ebcda6ef3f56.html在想要對wifi硬件動作之前，需要做兩件事情，一是要load wifi的driver，而是要翻開wpa_supplicant，其實假設是連接沒有加密的wifi，沒有必要翻開wpa_supplicant，但是為了講問題化為熟知的問題，此處還是先按照提示調用wifi_load_driver和wifi_start_supplicant按照上面的提示寫出

3、來的初始化代碼如下：int init_stage     / load the wifi driver: insmod .ko     int ret = wifi_load_driver;     ifret < 0         LOGE"Failed to load Wi-Fi driver. %s",strerrorerrno;       

4、  return -1;         / start wpa_supplicant     ret =  wifi_start_supplicant;     ifret < 0         LOGE"Failed to start supplicant daemon. %s",strerrorerrno;     

5、;    return -1;         return 0; 接下來，便是連接的過程了，經過上面的步驟，wifi的driver已經載入，wpa_supplicant也已經翻開，那咱們就可以開場連接無線了吧。后來證實這是錯誤的，因為anly_jun的這篇Android wifi分析的粒度只在Java層面的函數(shù)級別，因此有一些細節(jié)并沒有提到。在下面我會提到這些細節(jié)。按照一般的linux中連接wifi的步驟，這時候就可以直接調用一個程序來連接某個ssid的無線網絡，然后調用dhcpd來分配ip了，我之前在

6、eeepc上連接wifi就非常簡單，調用iwconfig ssid，再調用dhcpd就可以了。但很遺憾，Android上并沒有iwconfig這樣方便的工具。這下線索似乎就斷了，天無絕人之路，既然在Android的Java code中都可以添加一個無線網絡并且連接，那我們就去Android的Java源代碼中找一找。在Android中，程序員是使用WifiManager這個類來進展Wifi操作的，其中關于添加一個網絡的代碼如下：/* * Add a new network description to the set of configured networks. * The code netw

7、orkId field of the supplied configuration object * is ignored. * <p/> * The new network will be marked DISABLED by default. To enable it, * called link #enableNetwork. * * param config the set of variables that describe the configuration, *         

8、   contained in a link WifiConfiguration object. * return the ID of the newly created network description. This is used in *         other operations to specified the network to be acted upon. *         Returns

9、 code -1 on failure. */ public int addNetworkWifiConfiguration config     if config = null         return -1;         workId = -1;     return addOrUpdateNetworkconfig; /* * Internal method for doing the RP

10、C that creates a new network description * or updates an existing one. * * param config The possibly sparse object containing the variables that *         are to set or updated in the network description. * return the ID of the network on success, code -1 on f

11、ailure. */ private int addOrUpdateNetworkWifiConfiguration config     try         return mService.addOrUpdateNetworkconfig;     catch RemoteException e         return -1;     看其中確實是調用了s

12、ervice的函數(shù)，于是又在frameworks/base/services/java/com/android/server/WifiService.java中找到了有關增加一個網絡配置的相關代碼/* * see link .wifi.WifiManager#addOrUpdateNetworkWifiConfiguration * return the supplicant-assigned identifier for the new or updated * network if the operation succeeds, or code -1 if it fails */ publ

13、ic int addOrUpdateNetworkWifiConfiguration config     enforceChangePermission;     /*      * If the supplied networkId is -1, we create a new empty      * network configuration. Otherwise, the networkId should    &#

14、160; * refer to an existing configuration.      */     int netId = workId;     boolean newNetwork = netId = -1;     boolean doReconfig = false;     / networkId of -1 means we want to create a new network   

15、0; synchronized mWifiStateTracker         if newNetwork             netId = mWifiStateTracker.addNetwork;             if netId < 0    

16、60;            if DBG                     Slog.dTAG, "Failed to add a network!"           

17、                      return -1;                         doReconfig = true;   &#

18、160;             mNeedReconfig = mNeedReconfig | doReconfig;         setVariables:         /*          * Note that if a networkId for a non-

19、existent network          * was supplied, then the first setNetworkVariable          * will fail, so we don't bother to make a separate check          * for the validity of the

20、 ID up front.          */         if config.SSID != null &&                 !mWifiStateTracker.setNetworkVariable     

21、0;               netId,                     WifiConfiguration.ssidVarName,           

22、          config.SSID             if DBG                 Slog.dTAG, "failed to set SSID: "+config.SSID;   

23、;                      break setVariables;                 if config.BSSID != null &&       

24、          !mWifiStateTracker.setNetworkVariable                     netId,               &

25、#160;     WifiConfiguration.bssidVarName,                     config.BSSID             if DBG       

26、          Slog.dTAG, "failed to set BSSID: "+config.BSSID;                         break setVariables;      &#

27、160;  我們來到frameworks/base/wifi/java/android/net/wifi/WifiStateTracker.java中，看看addNetwork和setNetworkVariable函數(shù)都是什么樣的。/* * Add a network * * return network id of the new network */ public synchronized int addNetwork     if mWifiState.get != WIFI_STATE_ENABLED    

28、0;    return -1;         return WifiNative.addNetworkCommand; /* * Set network setting by name * * param netId network id of the network * param name network variable key * param value network variable value * return code true if the operation succeeds, c

29、ode false otherwise */ public synchronized boolean setNetworkVariableint netId, String name, String value     if mWifiState.get != WIFI_STATE_ENABLED         return false;         return WifiNative.setNetworkVariableComm

30、andnetId, name, value; 似乎WifiNative就應該是最終boss了，于是來到frameworks/base/wifi/java/android/net/wifi/WifiNative.java中一看，這兩個函數(shù)都是這么定義的。 public native static int addNetworkCommand; public native static boolean setNetworkVariableCommandint netId, String name, String value;  熟悉Android NDK開發(fā)的朋友都應該知道，這里

31、的函數(shù)都是通過jni鏈接到c/c+代碼中，于是我們略微花了一點時間，找到了這個函數(shù)所對應的frameworks/base/core/jni/android_net_wifi_Wifi.cpp static int doCommandconst char *cmd, char *replybuf, int replybuflen     size_t reply_len = replybuflen - 1;     if :wifi_commandcmd, replybuf, &reply_len != 0  

32、;       return -1;     else         / Strip off trailing newline         if reply_len > 0 && replybufreply_len-1 = 'n'         

33、;    replybufreply_len-1 = 'message'         else             replybufreply_len = 'message'         return 0;     static jint doI

34、ntCommandconst char *cmd     char reply256;     if doCommandcmd, reply, sizeofreply != 0         return jint-1;     else         return jintatoireply;     static jboolean

35、 doBooleanCommandconst char *cmd, const char *expect     char reply256;     if doCommandcmd, reply, sizeofreply != 0         return jbooleanJNI_FALSE;     else         return jbooleanst

36、rcmpreply, expect = 0;     static jint android_net_wifi_addNetworkCommandJNIEnv* env, jobject clazz     return doIntCommand"ADD_NETWORK" static jboolean android_net_wifi_setNetworkVariableCommandJNIEnv* env,         

37、0;                                                  job

38、ject clazz,                                                 

39、           jint netId,                                       

40、;                     jstring name,                            &#

41、160;                               jstring value     char cmdstr256;     jboolean isCopy;     const char

42、*nameStr = env->GetStringUTFCharsname, &isCopy;     const char *valueStr = env->GetStringUTFCharsvalue, &isCopy;     if nameStr = NULL | valueStr = NULL         return JNI_FALSE;     int cmdTooLong = snprin

43、tfcmdstr, sizeofcmdstr, "SET_NETWORK %d %s %s",                  netId, nameStr, valueStr >= intsizeofcmdstr;     env->ReleaseStringUTFCharsname, nameStr;     env->Release

44、StringUTFCharsvalue, valueStr;     return jboolean!cmdTooLong && doBooleanCommandcmdstr, "OK" / - /* * JNI registration. */ static JNINativeMethod gWifiMethods =     /* name, signature, funcPtr */     "loadDriver", "Z"

45、;,  void *android_net_wifi_loadDriver ,     "unloadDriver", "Z",  void *android_net_wifi_unloadDriver ,     "startSupplicant", "Z",  void *android_net_wifi_startSupplicant ,     "stopSupplicant&q

46、uot;, "Z",  void *android_net_wifi_stopSupplicant ,     "connectToSupplicant", "Z",  void *android_net_wifi_connectToSupplicant ,     "closeSupplicantConnection", "V",  void *android_net_wifi_closeSupplica

47、ntConnection ,     "listNetworksCommand", "Ljava/lang/String;",         void* android_net_wifi_listNetworksCommand ,     "addNetworkCommand", "I", void* android_net_wifi_addNetworkCommand ,  

48、;   "setNetworkVariableCommand", "ILjava/lang/String;Ljava/lang/String;Z",         void* android_net_wifi_setNetworkVariableCommand ,     "getNetworkVariableCommand", "ILjava/lang/String;Ljava/lang/String;

49、",         void* android_net_wifi_getNetworkVariableCommand ,  看來這下終于找到干活兒的函數(shù)了，可喜可賀，于是我們得出結論：在Android中，要連上一個無線網絡，首先需要添加一個網絡，然后設置這個網絡的配置，而這些步驟實際上都是通過向wpa_supplicant發(fā)送命令實現(xiàn)的。命令的格式例外的很簡單，比方添加一個網絡配置是ADD_NETWORK，設置一個網絡配置是SET_NETWORK netId varName var。于是根據(jù)Java代碼

50、我寫出了配置環(huán)節(jié)的代碼。int config_stage        / Add a network config to supplicant mode     int networkId = doIntCommand"ADD_NETWORK" / Add a new network id     ifnetworkId < 0         LOGE"Failed

51、to add a network configuration. %s",strerrorerrno;         return -1;         LOGE"Add a network %d",networkId;     / set the ssid of the destination wifi adhoc     char cmdstr256;  

52、60;  snprintfcmdstr, sizeofcmdstr, "SET_NETWORK %d %s %s",networkId, SSID_NAME, SSID;     if!doBooleanCommandcmdstr,"OK"         LOGE"Failed to set network %d configuration ssid. %s", networkId, strerrorerrno;  

53、;       return -1;         return networkId; 添加了一個配置的網絡之后，選擇某個網絡配置的命令是SELECT_NETWORK netId。在SELECT_NETWORK之后，wpa_supplicant就嘗試和該ssid的AP進行associate操作，在associate之后便調用dhcpd獲取ip。SELECT_NETWORK是立即返回的函數(shù)，那么何以得知已經和無線AP連接上了呢？Android的界面里面連接/斷開Wifi都是可

54、以被承受到的事件，在WifiStateTracker中我們看到是由WifiMonitor來監(jiān)聽由wpa_supplicant發(fā)過來的消息的，于是我們來到framework/base/wifi/java/android/net/wifi/WifiMonitor.java，看到其中承受消息的Monitor線程 class MonitorThread extends Thread     public MonitorThread         super"WifiMonitor&

55、quot;         public void run         if connectToSupplicant             / Send a message indicating that it is now possible to send commands       &#

56、160;     / to the supplicant             mWifiStateTracker.notifySupplicantConnection;         else             mWifiStateTracker.notif

57、ySupplicantLost;             return;                 /noinspection InfiniteLoopStatement         for ;       &

58、#160;     String eventStr = WifiNative.waitForEvent;             / Skip logging the common but mostly uninteresting scan-results event             if Config.LOGD &&am

59、p; eventStr.indexOfscanResultsEvent = -1                 Log.vTAG, "Event " + eventStr + ""                    

60、0;    if !eventStr.startsWitheventPrefix                 if eventStr.startsWithwpaEventPrefix &&                  

61、60;      0 < eventStr.indexOfpasswordKeyMayBeIncorrectEvent                     handlePasswordKeyMayBeIncorrect;           

62、0;                     continue;                         String eventName = eventStr.substringe

63、ventPrefixLen;             int nameEnd = eventName.indexOf' '             if nameEnd != -1                

64、eventName = eventName.substring0, nameEnd;             if eventName.length = 0                 if Config.LOGD Log.iTAG, "Received wpa_supplicant event with empty eve

65、nt name"   WifiNative.wairForEvent在wifi.c中對應的函數(shù)是wifi_wait_event，用來阻塞的等待wpa_supplicant發(fā)來的消息。當wpa_supplicant連接上之后，便會發(fā)出一個CONTROL-EVENT-CONNECTED的消息，只要截獲這個消息，我們便可以進行dhcp的操作了。基于以上的考慮，我寫了connect階段的代碼。這里我偷了一下懶，沒有仔細的去分析過來的命令，只是匹配到有CONNECTED的命令，就當已經連接上了。#define CONNECTED "CONNECTED"

66、int connect_stageint networkId     char cmdstr256;     / enable the network     snprintfcmdstr, sizeofcmdstr, "SELECT_NETWORK %d",networkId;     if!doBooleanCommandcmdstr,"OK"         L

67、OGE"Failed to select network %d. %s", networkId, strerrorerrno;         return -1;         / wait for connect     char buf256;     while1         int nread = wi

68、fi_wait_for_eventbuf, sizeofbuf;         ifnread > 0             LOGE"receive buf:n %sn",buf;             ifstrstrbuf,CONNECTED > 0  &

69、#160;              break;                         / XXX danger of not going out of the loop!      &#

70、160;          continue;         return 0; 在WifiStateTracer中我還找到了負責dhcp的DhcpHandler，按照其中的函數(shù)寫了dhcp階段的代碼int dhcp_stage     int result;     in_addr_t ipaddr, gateway, mask, dns1, dns2, server;   

71、;  uint32_t lease;     char ifname256;     char mDns1Name256;     char mDns2Name256;     property_get"erface", ifname ,"eth0"     snprintfmDns1Name, sizeofmDns1Name, "net.%s.dns1",if

72、name;     snprintfmDns2Name, sizeofmDns2Name, "net.%s.dns2",ifname;     result = dhcp_do_requestifname, &ipaddr, &gateway, &mask, &dns1, &dns2, &server, &lease;     ifresult != 0       &#

73、160; LOGE"Failed to dhcp on interface %s. %s", ifname, strerrorerrno;         return -1;         struct in_addr dns_struct1, dns_struct2;     dns_struct1.s_addr = dns1;     dns_struct2.s_addr = d

74、ns2;     property_setmDns1Name,inet_ntoadns_struct1;     property_setmDns2Name,inet_ntoadns_struct2;     return 0; 于是我用無線路由器建立了一個最簡單的無線網絡，ssid=TSever，沒有密碼，按照上面步驟進展聯(lián)網。結果在ADD_NETWORK的步驟就出錯了，無法獲得網絡id，這是怎么一回事呢？看到dhcp時的代碼要對特定的Network Interface做操作，突然想起來之前在代碼中似乎

75、看到有對Interface做使能操作的代碼WifiService在調用mWifiStateTracker.enableNetwork之前，還調用了String ifname = mWifiStateTracker.getInterfaceName; NetworkUtils.enableInterfaceifname;這兩句。于是在init階段，加上了下面這段。    char ifname256;     property_get"erface", ifname ,"eth0"

76、     ret = ifc_enableifname;     ifret < 0         LOGE"Failed to enable wifi interface %s. %s", ifname ,strerrorerrno;         return -1;     但是運行起來還是出同樣的錯誤，不過這次busybox if

77、config之后可以發(fā)現(xiàn)eth0的端口了 ，至少沒有做無用功。倒回去看在WifiMonitor的MonitorThread中有connectToSupplicant的調用，本以為此調用不是非常關鍵，然后去hardware/libhardware_legacy/wifi/wifi.c文件里面看到全局有一個static struct wpa_ctrl *ctrl_conn;并且在wifi_command中需要用到這個ctrl_conn，那么假設這個ctrl_conn是NULL的話，所有的wifi_command命令自然都無法完成了，于是又加上了ret = wifi_connect_to_suppl

78、icant;     ifret < 0         LOGE"Failed to connect supplicant daemon. %s",strerrorerrno;         return -1;     這樣編譯完運行之后，果然順利的分配到id了。運行一下程序，還是出現(xiàn)了錯誤，輸出的log如下。I/wpa_supplicant  618:

79、CTRL-EVENT-SCAN-RESULTS  ReadyI/wpa_supplicant  618: Trying to associate with 00:24:b2:c1:16:b6 SSID='TServer' freq=2462 MHzI/wpa_supplicant  618: CTRL-EVENT-STATE-CHANGE id=-1 state=3E/          612: Finished init stage.E/  &#

80、160;       612: Add a network 2E/          612: Finished config stage.I/wpa_supplicant  618: CTRL-EVENT-STATE-CHANGE id=1 state=0E/          612: receive buf:E/     

81、     612:  CTRL-EVENT-STATE-CHANGE id=1 state=0I/wpa_supplicant  618: CTRL-EVENT-STATE-CHANGE id=-1 state=2E/          612: receive buf:E/          612:  CTRL-EVENT-STATE-CHANGE id=-1 state=

82、2I/wpa_supplicant  618: CTRL-EVENT-SCAN-RESULTS  ReadyE/          612: receive buf:E/          612:  CTRL-EVENT-SCAN-RESULTS  ReadyI/wpa_supplicant  618: CTRL-EVENT-STATE-CHANGE id=-1 state=4E/&#

83、160;         612: receive buf:E/          612:  CTRL-EVENT-STATE-CHANGE id=-1 state=4I/wpa_supplicant  618: Associated with 00:24:b2:c1:16:b6E/          612: receive buf:E/

84、60;         612:  Associated with 00:24:b2:c1:16:b6I/wpa_supplicant  618: CTRL-EVENT-SCAN-RESULTS  ReadyE/          612: receive buf:E/          612:  CTRL-EVENT-SCA

85、N-RESULTS  ReadyD/NetworkLocationProvider  127: onCellLocationChanged 4517,30785I/wpa_supplicant  618: Authentication with 00:24:b2:c1:16:b6 timed out.E/          612: receive buf:E/          612:  Au

86、thentication with 00:24:b2:c1:16:b6 timed out. 注意到紅色的那句log，我的wifi并沒有設置密碼，為什么還需要Authentication呢？想一想是不是wpa_supplicant的限制，于是去網上搜了到了這篇wpa_supplicant 工具使用，發(fā)現(xiàn)沒有密碼的情況下應該是這樣的配置# 明文連接方式不使用WPA和IEEE802.1Xnetwork= ssid="plaintext-test" key_mgmt=NONE于是在config階段加上了對key_mgmt的設置，這下就連上了Wifi了，正確的log如下b

87、ash-4.1# wificonnectI/wpa_supplicant  871: CTRL-EVENT-SCAN-RESULTS  ReadyI/wpa_supplicant  871: Trying to associate with 00:24:b2:c1:16:b6 SSID='TServer' freq=2462 MHzI/wpa_supplicant  871: CTRL-EVENT-STATE-CHANGE id=-1 state=3E/       

88、  865: Finished init stage.E/          865: Add a network 2E/          865: Finished config stage.I/wpa_supplicant  871: CTRL-EVENT-STATE-CHANGE id=1 state=0E/          865: receive buf:E/          865:  CTRL-EVENT-STATE-CHANGE id=1 state=0I/wpa_supplicant  871: CTRL-EVENT-STATE-CHANGE id=-1 state=2E/     &#