淺析android下如何透過jni監控wifi網路連接、dhcpcd執行和power電源控制
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libs/android_runtime/android_net_wifi_Wifi.cpp
部分jni接口
static JNINativeMethod gWifiMethods[] = {
{ "loadDriver", "()Z", (void *)android_net_wifi_loadDriver },
{ "setPowerModeCommand", "(I)Z", (void*) android_net_wifi_setPowerModeCommand },//電源管理
{ "connectToSupplicant", "()Z", (void *)android_net_wifi_connectToSupplicant },
{ "waitForEvent", "()Ljava/lang/String;", (void*) android_net_wifi_waitForEvent },
{ "disconnectCommand", "()Z", (void *)android_net_wifi_disconnectCommand },
…
};
int register_android_net_wifi_WifiManager(JNIEnv* env)
{
…
return AndroidRuntime::registerNativeMethods(env,
WIFI_PKG_NAME, gWifiMethods, NELEM(gWifiMethods));//登記jni
}
libs/android_runtime/AndroidRuntime.cpp
static const RegJNIRec gRegJNI[] = {
…
REG_JNI(register_android_net_wifi_WifiManager),
…
};
int AndroidRuntime::startReg(JNIEnv* env)
{
…
register_jni_procs(gRegJNI, NELEM(gRegJNI), env);
…
}
AndroidRuntime::start
=>startReg(env)即呼叫方法int AndroidRuntime::startReg(JNIEnv* env)
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wifi_load_driver
wifi_start_supplicant
=>ensure_config_file_exists
//檢查/data/misc/wifi/wpa_supplicant.conf檔案是否存在,如果不存在,那麼從/system/etc/wifi/wpa_supplicant.conf動態拷貝一份
android_net_wifi_connectToSupplicant
=>wifi_connect_to_supplicant
=>
ctrl_conn = wpa_ctrl_open(ifname);
monitor_conn = wpa_ctrl_open(ifname);
wpa_ctrl_attach(monitor_conn);
android_net_wifi_waitForEvent
=>wifi_wait_for_event
=>wpa_ctrl_recv(monitor_conn, buf, &nread);
=>recv(ctrl->s, reply, *reply_len, 0);//阻塞等待wpa_supplicant的netlink資料過來
=>如果接收的buf資料區,buf[0]為'<',那麼說明有level等級資訊,所以將'<'...'>'資料剔除,然後wifi_wait_for_event函數回傳[luther.gliethttp].
java/android/android/net/wifi/WifiMonitor.java
public class WifiMonitor {
…
public void startMonitoring() {
new MonitorThread().start();//啟動java執行緒
}
class MonitorThread extends Thread {
public MonitorThread() {
super("WifiMonitor");
}
public void run() {
for (;;) {
ensureSupplicantConnection();//=>WifiNative.connectToSupplicant呼叫jni函式android_net_wifi_connectToSupplicant
String eventStr = WifiNative.waitForEvent();//=>呼叫jni函式android_net_wifi_waitForEvent
//private static final int CONNECTED = 1;
//private static final int DISCONNECTED = 2;
//private static final String eventPrefix = "CTRL-EVENT-";
//private static final int eventPrefixLen = eventPrefix.length();
//private static final String connectedEvent = "CONNECTED";
//private static final String disconnectedEvent = "DISCONNECTED";
String eventName = eventStr.substring(eventPrefixLen);//移除"CTRL-EVENT-"字串
int nameEnd = eventName.indexOf(' ');//找到隨後的空格位置,這在wpa_supplicant發送時
//#define WPA_EVENT_CONNECTED "CTRL-EVENT-CONNECTED "中,已經內建空格了.
if (nameEnd != -1)
eventName = eventName.substring(0, nameEnd);
int event;
if (eventName.equals(connectedEvent))//偵測netlink過來的字串action類型
event = CONNECTED;
else if (eventName.equals(disconnectedEvent))
event = DISCONNECTED;
…
int ind = eventStr.indexOf(" - ");//CTRL-EVENT-CONNECTED - Connection to ...
if (ind != -1)
eventData = eventStr.substring(ind + 3);
//剔除前導控製字元,將" - "後面的描述字串作為真實資料,繼續處理
…
if (event == STATE_CHANGE) {
handleSupplicantStateChange(eventData);
} else if (event == DRIVER_STATE) {
handleDriverEvent(eventData);
} else {
handleEvent(event, eventData);//對於CONNECTED和DISCONNECTED等netlink事件將執行此操作來處理[luther.gliethttp]
// If supplicant is gone, exit the thread
if (event == TERMINATING) {
break;
}
}
…
void handleEvent(int event, String remainder) {
switch (event) {
case DISCONNECTED:
handleNetworkStateChange(NetworkInfo.DetailedState.DISCONNECTED, remainder);
break;
case CONNECTED:
handleNetworkStateChange(NetworkInfo.DetailedState.CONNECTED, remainder);//控制介面顯示
break;
…
}
public class WifiStateTracker extends NetworkStateTracker {
…
public void startEventLoop() {
mWifiMonitor.startMonitoring();//啟動上面的MonitorThread執行緒
}
…
}
java/services/com/android/server/WifiService.java
public class WifiService extends IWifiManager.Stub {
…
private boolean setWifiEnabledBlocking(boolean enable) {
final int eventualWifiState = enable ? WIFI_STATE_ENABLED : WIFI_STATE_DISABLED;
…
if (enable) {
if (WifiNative.loadDriver()) {
Log.e(TAG, "Failed to load Wi-Fi driver.");
updateWifiState(WIFI_STATE_UNKNOWN);
return false;
}
if (WifiNative.startSupplicant()) {
WifiNative.unloadDriver();
Log.e(TAG, "Failed to start supplicant daemon.");
updateWifiState(WIFI_STATE_UNKNOWN);
return false;
}
mWifiStateTracker.startEventLoop();
//啟動MonitorThread執行緒,等待wpa_supplicant將netlink資料轉送過來,然後根據netlink動作類型,進一步影響介面顯示[luther.gliethttp].
}
…
}
java/android/android/net/wifi/WifiStateTracker.java
電源管理
private void handleConnectedState() {
…
mDhcpTarget.obtainMessage(EVENT_DHCP_START).sendToTarget();//傳遞到下面的handleMessage方法
…
}
public void onChange(boolean selfChange) {
…
handleConnectedState();
…
}
public class WifiStateTracker extends NetworkStateTracker {
…
public void handleMessage(Message msg) {
switch (msg.what) {
case EVENT_SUPPLICANT_CONNECTION:
case EVENT_NETWORK_STATE_CHANGED:
handleConnectedState();//調用
…
private class DhcpHandler extends Handler {
private Handler mTarget;
public DhcpHandler(Looper looper, Handler target) {
super(looper);
mTarget = target;
}
public void handleMessage(Message msg) {
int event;
//private static final int DRIVER_POWER_MODE_AUTO = 0;
//private static final int DRIVER_POWER_MODE_ACTIVE = 1;
switch (msg.what) {
case EVENT_DHCP_START:
synchronized (this) {
WifiNative.setPowerModeCommand(DRIVER_POWER_MODE_ACTIVE);//設定電源模式,呼叫android_net_wifi_setPowerModeCommand
}
Log.d(TAG, "DhcpHandler: DHCP request started");
//libs/android_runtime/android_net_NetUtils.cpp
//static JNINativeMethod gNetworkUtilMethods[] = {
//{ "runDhcp", "(Ljava/lang/String;Landroid/net/DhcpInfo;)Z", (void *)android_net_utils_runDhcp },
// ...
//};
if (NetworkUtils.runDhcp(mInterfaceName, mDhcpInfo)) {//執行dhcp申請ip位址操作
event = EVENT_INTERFACE_CONFIGURATION_SUCCEEDED;
if (LOCAL_LOGD) Log.v(TAG, "DhcpHandler: DHCP request succeeded");
} else {
event = EVENT_INTERFACE_CONFIGURATION_FAILED;
Log.i(TAG, "DhcpHandler: DHCP request failed: " +
NetworkUtils.getDhcpError());
//如果dhcpcd分配ip失敗,那麼Message.obtain(mTarget, event).sendToTarget();將執行
//WifiNative.disconnectCommand();即：static JNINativeMethod gWifiMethods[] = {
//android_net_wifi_disconnectCommand發送"DISCONNECT"字串[luther.gliethttp]
//然後在wpa_supplicant服務端執行wpa_supplicant_ctrl_iface_process
//wpa_supplicant_disassociate
}
synchronized (this) {
WifiNative.setPowerModeCommand(DRIVER_POWER_MODE_AUTO);
}
Message.obtain(mTarget, event).sendToTarget();
break;
}
}
}
…
/**
* Send the tracker a notification that a connection to the supplicant
* daemon 有 been established.
*/
//在上面的public class WifiMonitor=>ensureSupplicantConnection
//=>
//while (!supplicantConnected) {
// boolean connected;
//synchronized (mWifiStateTracker) {
//connected = WifiNative.connectToSupplicant();//如果沒有連線成功,那麼while循環嘗試,直到嘗試成功,或定義了oneShot,僅一次嘗試
//=>mWifiStateTracker.notifySupplicantConnection();//如果WifiNative.connectToSupplicant()成功,那麼將執行
//mWifiStateTracker.notifySupplicantConnection();的呼叫.
void notifySupplicantConnection() {//傳送message
Message.obtain(this, EVENT_SUPPLICANT_CONNECTION).sendToTarget();
}
void notifyStateChange(SupplicantState newState) {
Message.obtain(this, EVENT_SUPPLICANT_STATE_CHANGED, newState).sendToTarget();
}
…
}
static jboolean android_net_wifi_setPowerModeCommand(JNIEnv* env, jobject clazz, jint mode)
{
char cmdstr[256];
sprintf(cmdstr, "DRIVER POWERMODE %d", mode);
return doBooleanCommand(cmdstr, "OK");
}
android_net_wifi_setPowerModeCommand
=>doBooleanCommand
=>doCommand
=>wifi_command
=>wifi_send_command
=>wpa_ctrl_request
=>send給wpa_supplicant
然後wpa_supplicant將做以下接收操作：
system/extra/wpa_supplicant/main.c
=>wpa_supplicant_add_iface
=>wpa_supplicant_init_iface2
=>wpa_supplicant_ctrl_iface_init
=>註冊ctrl_conn控制埠和monitor_conn監聽埠的處理函數
eloop_register_read_sock(priv->sock, wpa_supplicant_ctrl_iface_receive, wpa_s, priv);//ctrl_conn埠的handler處理函數
wpa_msg_register_cb(wpa_supplicant_ctrl_iface_msg_cb);//monitor_conn端口的回調處理函數,處理netlink資料到所有monitor_conn監聽端口
=>wpa_supplicant_ctrl_iface_receive//對於unix通訊方式
=>wpa_supplicant_ctrl_iface_process
=>如果wpa_cli發送的是wpa_cli driver xxx形式的指令,那麼呼叫這個函數
if (os_strncmp(buf, "DRIVER ", 7) == 0) {//掠過前7個,直接將指令傳過去
reply_len = wpa_supplicant_driver_cmd(wpa_s, buf + 7, reply, reply_size);
=>wpa_supplicant_driver_cmd
=>wpa_drv_driver_cmd
=>自訂DRIVER擴充處理函數,所以對於java傳遞過來的power電源管理指令,wpa_drv_driver_cmd將收到"POWERMODE 0"或"POWERMODE 1"字串[luther.gliethttp]
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jni
=>runDhcp
=>android_net_utils_runDhcp
libs/netutils/dhcp_utils.c
=>dhcp_do_request
=>
static const char DAEMON_NAME[] = "dhcpcd";
static const char DAEMON_PROP_NAME[] = "init.svc.dhcpcd";
static const char DHCP_PROP_NAME_PREFIX[] = "dhcp";
const char *ctrl_prop = "ctl.start";
const char *desired_status = "running";
snprintf(result_prop_name, sizeof(result_prop_name), "%s.%s.result",
DHCP_PROP_NAME_PREFIX,
interface);
property_set(result_prop_name, "");//設定dhcp.eth0.result="";等到成功完成dhcp之後,
property_set(ctrl_prop, DAEMON_NAME);//向名字為dhcpcd的service,發送"ctrl.start"啟動命令字,該service在init.rc中
//init.rc中dhcpcd服務行程指令字
//service dhcpcd /system/bin/dhcpcd eth0
// disabled
// oneshot
wait_for_property(DAEMON_PROP_NAME, desired_status, 10);
//init.c=>init行程
//=>handle_property_set_fd因為是"ctrl.start"命令字,所以呼叫handle_control_message處理控制訊息
//=>handle_control_message
//=>msg_start
//=>
// struct service *svc = service_find_by_name(name);
// service_start(svc);//啟動svc,即執行：/system/bin/dhcpcd eth0
//=>service_start
//=>pid = fork();
// if(pid == 0)execve(svc->args[0], (char**) svc->args, (char**) ENV);子程序執行execve運行/system/bin/dhcpcd,參數為eth0
//=>否則父行程,即init行程將
//=>notify_service_state(svc->name, "running");設定該svc的狀態prop
// snprintf(pname, sizeof(pname), "init.svc.%s", name);
// property_set(pname, state);//所以這樣上面wait_for_property(DAEMON_PROP_NAME, desired_status, 10);也才能夠正常pass[luther.gliethttp].
wait_for_property(result_prop_name, NULL, 15);//等待dhcp.eth0.result=非空
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system/extra/dhcpcd-4.0.0-beta9/dhcpcd.c
dhcpcd
=>main
# define SYSCONFDIR "/system/etc/dhcpcd"
#define PACKAGE "dhcpcd"
# define CONFIG SYSCONFDIR "/" PACKAGE ".conf"
# define LIBEXECDIR "/system/etc/dhcpcd"
# define SCRIPT LIBEXECDIR "/" PACKAGE "-run-hooks"
=>strlcpy(options->script, SCRIPT, sizeof(options->script));//預設的options->script="/system/etc/dhcpcd/dhcpcd-run-hooks"
=>f = fopen(cf ? cf : CONFIG, "r");//如果沒有指定.conf檔,那麼使用預設.conf文件
=>parse_config_line//解析"/system/etc/dhcpcd/dhcpcd.conf"預設設定檔
=>parse_option
=>如果在"/system/etc/dhcpcd/dhcpcd.conf"有"script"這個節
=>那麼執行strlcpy(options->script, oarg, sizeof(options->script));直接拷貝
/*
{"script", required_argument, NULL, 'c'},
{"option", required_argument, NULL, 'o'},
"/system/etc/dhcpcd/dhcpcd.conf"中的部分內容如下：
…
option domain_name_servers, domain_name, domain_search, host_name
…
*/
=>dhcp_run
=>handle_dhcp_packet
=>handle_dhcp
=>bind_dhcp
reason = "TIMEOUT";reason = "BOUND";reason = "REBIND";reason = "RENEW";
system/extra/dhcpcd-4.0.0-beta9/configure.c
=> configure(iface, reason, state->new, state->old, &state->lease, options, 1);
//如果dhcp逾時或dhcp成功,都會呼叫exec_script來執行腳本,
//執行setprop dhcp.${interface}.result "failed"或者
//執行setprop dhcp.${interface}.result "ok"
=>exec_script(options, iface->name, reason, NULL, old);
=>然後configure_env透過環境變數將reason傳遞到腳本中
int exec_script(const struct options *options, const char *iface, const char *reason,
const struct dhcp_message *dhcpn, const struct dhcp_message *dhcpo)
=>pid = fork();
=>if(pid == 0)execve(options->script, argv, env);//子程序執行腳本,預設"/system/etc/dhcpcd/dhcpcd-run-hooks"
//dhcpcd-run-hooks腳本會根據level值,決定是否執行system/etc/dhcpcd/dhcpcd-hook/*目錄下的對應文件
//我們的系統在該system/etc/dhcpcd/dhcpcd-hook/*目錄下有以下3個文件
//95-configured
//20-dns.conf
//01-test
=>父進程回傳while (waitpid(pid, &status, 0) == -1)等待子進程腳本執行完成
system/extra/dhcpcd-4.0.0-beta9/dhcpcd-hooks/20-dns.conf
system/extra/dhcpcd-4.0.0-beta9/dhcpcd-hooks/95-configured
…
setprop dhcp.${interface}.ipaddress "${new_ip_address}"
setprop dhcp.${interface}.result "ok"//設定屬性為ok
setprop dhcp.${interface}.result "failed"
…
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inet_init、tcp_prot
sock->ops->sendmsg(iocb, sock, msg, size);
=>inetsw_array[]
=>inet_stream_ops
=>tcp_sendmsg
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wpa_cli.c
=>main
=>wpa_cli_interactive
=>wpa_cli_recv_pending(monitor_conn, 0, 0);//阻塞等待wpa_supplicant傳送資料過來
=>如果action_monitor為true,那麼將執行一些簡單加工操作,否則將直接將wpa_supplicant發過來的資料印到console上[luther.gliethttp].