Android 7.1开机之后APN的加载及拨号上网流程分析
Posted 安时光Mrsongs
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1、前言
在前段时间的项目中遇到客户的设备出现APN断开的情况没有自动连接，后来折腾了一段时间解决了这个问题。现在用这篇博客记录一下APN的选择和连接流程。
2、名词解析
- APN：APN指一种网络接入技术，是通过手机上网时必须配置的一个参数，它决定了手机通过哪种接入方式来访问网络。
对于手机用户来说，可以访问的外部网络类型有很多，例如：Internet、WAP网站、集团企业内部网络、行业内部专用网络。而不同的接入点所能访问的范围以及接入的方式是不同的，网络侧如何知道手机激活以后要访问哪个网络从而分配哪个网段的IP呢，这就要靠APN来区分了，即APN决定了用户的手机通过哪种接入方式来访问什么样的网络。
- PDN:Packet data network，分组数据网，即常说的Internet，在GPRS网络中代表外部数据网络的总称
3、android 中APN的存储形式
Android 系统中APN是以apns-conf.xml文件的形式配置的，位于设备中的system/etc目录下。
apn 的配置信息如下：
<apn carrier="ENTEL4G" //运营商
mcc="736" //Mobile Country Code，移动国家码
mnc="02" //Mobile Network Code，移动网络码
apn="4g.entel" //apn名称
user=""
password=""
proxy="" //代理
port="" //端口
authtype="2"
type="default,supl" //apn类型
/>
4、初识TelephonyProvider
4.1 apn文件是怎么被解析的呢，设置中的apn信息怎么保存的呢?
这里就轮到TelephonyProvider 出场了。
TelephonyProvider继承自ContentProvider，在android中的代码路径为：
packages/providers/TelephonyProvider。
它的UML类图如下：
在AndroidManifest.xml中可以看到application 标签中定义了android:process=“com.android.phone” ，这样TelephonyProvider就运行在com.android.phone进程中，也就是packages\\services\\Telephony 目录下的Telephony服务。
4.2 TelephonyProvider 的onCreate()函数
代码如下：
@Override
public boolean onCreate() {
mOpenHelper = new DatabaseHelper(getContext());
// Call getReadableDatabase() to make sure onUpgrade is called
if (VDBG) log("onCreate: calling getReadableDatabase to trigger onUpgrade");
SQLiteDatabase db = mOpenHelper.getReadableDatabase();
// Update APN db on build update
String newBuildId = SystemProperties.get("ro.build.id", null);
if (!TextUtils.isEmpty(newBuildId)) {
// Check if build id has changed
SharedPreferences sp = getContext().getSharedPreferences(BUILD_ID_FILE,
Context.MODE_PRIVATE);
String oldBuildId = sp.getString(RO_BUILD_ID, "");
if (!newBuildId.equals(oldBuildId)) {
if (DBG) log("onCreate: build id changed from " + oldBuildId + " to " + newBuildId);
// Get rid of old preferred apn shared preferences
SubscriptionManager sm = SubscriptionManager.from(getContext());
if (sm != null) {
List<SubscriptionInfo> subInfoList = sm.getAllSubscriptionInfoList();
for (SubscriptionInfo subInfo : subInfoList) {
SharedPreferences spPrefFile = getContext().getSharedPreferences(
PREF_FILE_APN + subInfo.getSubscriptionId(), Context.MODE_PRIVATE);
if (spPrefFile != null) {
SharedPreferences.Editor editor = spPrefFile.edit();
editor.clear();
editor.apply();
}
}
}
// Update APN DB
updateApnDb();
} else {
if (VDBG) log("onCreate: build id did not change: " + oldBuildId);
}
sp.edit().putString(RO_BUILD_ID, newBuildId).apply();
} else {
if (VDBG) log("onCreate: newBuildId is empty");
}
if (VDBG) log("onCreate:- ret true");
return true;
}
从上面的代码，我们知道TelephonyProvider初始化时的主要工作包括：
- new DatabaseHelper 创建出数据库；
- 根据build_id的值，如果跟之前的不同则重新load apn xml文件写入到数据库中，并将之前选中的sharepreference记录选中的 apn清除，并且最后将数据中不在apn xml文件中的数据行全部删除。
4.3 TelephonyProvider 的内部类 DatabaseHelper
DatabaseHelper是 TelephonyProvider 的一个内部类，在TelephonyProvider 的onCreate函数中首先被创建。
4.3.1 DatabaseHelper的构造函数中会传入数据的名字用于创建数据库
这个DATABASE_NAME 就是"telephony.db"，创建路径位于：/data/user_de/0/com.android.providers.telephony/databases/telephony.db
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, getVersion(context));
mContext = context;
}
4.3.2 DatabaseHelper 的onCreate函数
@Override
public void onCreate(SQLiteDatabase db) {
if (DBG) log("dbh.onCreate:+ db=" + db);
createSimInfoTable(db);
createCarriersTable(db, CARRIERS_TABLE);
initDatabase(db);
if (DBG) log("dbh.onCreate:- db=" + db);
}
这里可以看到它作了三件事：
- 1、创建SIM卡信息的表
- 2、创建运营商信息的表
- 3、初始化数据库，这里是重点。
4.3.2 DatabaseHelper 的 initDatabase（）初始化作了哪些事
从这个代码中可以看到函数中主要是：
- 1、使用XML 解析apn-conf.xml文件并写入到数据库中。
- 2、将数据库中不是xml中的数据清除掉。
private void initDatabase(SQLiteDatabase db) {
if (VDBG) log("dbh.initDatabase:+ db=" + db);
// Read internal APNS data
Resources r = mContext.getResources();
XmlResourceParser parser = r.getXml(com.android.internal.R.xml.apns);
int publicversion = -1;
try {
XmlUtils.beginDocument(parser, "apns");
publicversion = Integer.parseInt(parser.getAttributeValue(null, "version"));
loadApns(db, parser);
} catch (Exception e) {
loge("Got exception while loading APN database." + e);
} finally {
parser.close();
}
// Read external APNS data (partner-provided)
XmlPullParser confparser = null;
File confFile = getApnConfFile();
FileReader confreader = null;
if (DBG) log("confFile = " + confFile);
try {
confreader = new FileReader(confFile);
confparser = Xml.newPullParser();
confparser.setInput(confreader);
XmlUtils.beginDocument(confparser, "apns");
// Sanity check. Force internal version and confidential versions to agree
int confversion = Integer.parseInt(confparser.getAttributeValue(null, "version"));
if (publicversion != confversion) {
log("initDatabase: throwing exception due to version mismatch");
throw new IllegalStateException("Internal APNS file version doesn't match "
+ confFile.getAbsolutePath());
}
loadApns(db, confparser);
} catch (FileNotFoundException e) {
// It's ok if the file isn't found. It means there isn't a confidential file
// Log.e(TAG, "File not found: '" + confFile.getAbsolutePath() + "'");
} catch (Exception e) {
loge("initDatabase: Exception while parsing '" + confFile.getAbsolutePath() + "'" +
e);
} finally {
// Get rid of user/carrier deleted entries that are not present in apn xml file.
// Those entries have edited value USER_DELETED/CARRIER_DELETED.
if (VDBG) {
log("initDatabase: deleting USER_DELETED and replacing "
+ "DELETED_BUT_PRESENT_IN_XML with DELETED");
}
// Delete USER_DELETED
db.delete(CARRIERS_TABLE, IS_USER_DELETED + " or " + IS_CARRIER_DELETED, null);
// Change USER_DELETED_BUT_PRESENT_IN_XML to USER_DELETED
ContentValues cv = new ContentValues();
cv.put(EDITED, USER_DELETED);
db.update(CARRIERS_TABLE, cv, IS_USER_DELETED_BUT_PRESENT_IN_XML, null);
// Change CARRIER_DELETED_BUT_PRESENT_IN_XML to CARRIER_DELETED
cv = new ContentValues();
cv.put(EDITED, CARRIER_DELETED);
db.update(CARRIERS_TABLE, cv, IS_CARRIER_DELETED_BUT_PRESENT_IN_XML, null);
if (confreader != null) {
try {
confreader.close();
} catch (IOException e) {
// do nothing
}
}
// Update the stored checksum
setApnConfChecksum(getChecksum(confFile));
}
if (VDBG) log("dbh.initDatabase:- db=" + db);
}
apn的xml 有那些呢 ？根据getApnConfFile 函数可以知道有如下这些目录。
private File getApnConfFile() {
// Environment.getRootDirectory() is a fancy way of saying ANDROID_ROOT or "/system".
File confFile = new File(Environment.getRootDirectory(), PARTNER_APNS_PATH);
File oemConfFile = new File(Environment.getOemDirectory(), OEM_APNS_PATH);
File updatedConfFile = new File(Environment.getDataDirectory(), OTA_UPDATED_APNS_PATH);
confFile = getNewerFile(confFile, oemConfFile);
confFile = getNewerFile(confFile, updatedConfFile);
return confFile;
}
private static final String PARTNER_APNS_PATH = "etc/apns-conf.xml";
private static final String OEM_APNS_PATH = "telephony/apns-conf.xml";
private static final String OTA_UPDATED_APNS_PATH = "misc/apns-conf.xml";
private static final String OLD_APNS_PATH = "etc/old-apns-conf.xml";
到这里TelephonyProvider的业务就很清晰了，他就要就是开机的时候会根据build id来判断是否试正常开机还是升级之后的不同版本，如果不同，则重新创建telephony.db数据库，并重新解析加载apn.xml文件写入到数库中。
5、开机之后APN界面是怎么自动选择APN连接的呢 ？
刚开始我以为设置界面开机之后会默认选择一个已连接的APN的逻辑是在设置里面做的，看了一下设置ApnSettings.java相关的代码发现并没有如何选择apn去拨号的操作。
代码路径：packages\\apps\\Settings\\src\\com\\android\\settings\\ApnSettings.java
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
final Activity activity = getActivity();
final int subId = activity.getIntent().getIntExtra(SUB_ID,
SubscriptionManager.INVALID_SUBSCRIPTION_ID);
mMobileStateFilter = new IntentFilter(
TelephonyIntents.ACTION_ANY_DATA_CONNECTION_STATE_CHANGED);
setIfOnlyAvailableForAdmins(true);
mSubscriptionInfo = SubscriptionManager.from(activity).getActiveSubscriptionInfo(subId);
mUiccController = UiccController.getInstance();
CarrierConfigManager configManager = (CarrierConfigManager)
getSystemService(Context.CARRIER_CONFIG_SERVICE);
PersistableBundle b = configManager.getConfig();
mHideImsApn = b.getBoolean(CarrierConfigManager.KEY_HIDE_IMS_APN_BOOL);
mAllowAddingApns = b.getBoolean(CarrierConfigManager.KEY_ALLOW_ADDING_APNS_BOOL);
mUserManager = UserManager.get(activity);
}
如果不是上层应用自动拨号的，那就是底层自动选择的了 ？带着疑问我看了一下开机后的log打印流程发现了端倪：在DCTracker的log中发现DcTracker对象被创建后会注册监听RILD上报事件，当上报EVENT_DATA_CONNECTION_ATTACHED 就会创建apn列表并且获取preference apn 进行拨号，当然第一次没有设置是没有preference apn 的，这里就从 apn 列表中选择apn 进行拨号，按着这条线索继续看一下DCTracker 的代码逻辑吧。
6、DCTracker 登场
这里先放一张DCTracker 的相关类图，它是Telephony架构中监听SIM状态的状态变化和拨号的结果，类似于WifiTrakcker或者NetworkMonitor这样的角色。它是跟随着com.android.phone进程启动的时候创建的，不同类型phone 对应着一种DcTracker。
6.1 DcTracker的构造函数
代码路径：frameworks/opt/telephony/src/java/com/android/internal/telephony/dataconnection/DcTracker.java
构造函数很长，但是总结一下就主要干了这几件事：
- 1、初始化mUiccController 并注册监听SIM状态。
- 2、registerForAllEvents() 注册监听事件。
- 3、监听数据库变化以及其他的一些初始化工作。
这里看看registerForAllEvents 监听事件。
//***** Constructor
public DcTracker(Phone phone) {
super();
mPhone = phone;
if (DBG) log("DCT.constructor");
mResolver = mPhone.getContext().getContentResolver();
mUiccController = UiccController.getInstance();
mUiccController.registerForIccChanged(this, DctConstants.EVENT_ICC_CHANGED, null);
mAlarmManager =
(AlarmManager) mPhone.getContext().getSystemService(Context.ALARM_SERVICE);
mCm = (ConnectivityManager) mPhone.getContext().getSystemService(
Context.CONNECTIVITY_SERVICE);
IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_SCREEN_ON);
filter.addAction(Intent.ACTION_SCREEN_OFF);
filter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
filter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
filter.addAction(INTENT_DATA_STALL_ALARM);
filter.addAction(INTENT_PROVISIONING_APN_ALARM);
// TODO - redundent with update call below?
mDataEnabledSettings.setUserDataEnabled(getDataEnabled());
mPhone.getContext().registerReceiver(mIntentReceiver, filter, null, mPhone);
SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(mPhone.getContext());
mAutoAttachOnCreation.set(sp.getBoolean(Phone.DATA_DISABLED_ON_BOOT_KEY, false));
mSubscriptionManager = SubscriptionManager.from(mPhone.getContext());
mSubscriptionManager.addOnSubscriptionsChangedListener(mOnSubscriptionsChangedListener);
HandlerThread dcHandlerThread = new HandlerThread("DcHandlerThread");
dcHandlerThread.start();
Handler dcHandler = new Handler(dcHandlerThread.getLooper());
mDcc = DcController.makeDcc(mPhone, this, dcHandler);
mDcTesterFailBringUpAll = new DcTesterFailBringUpAll(mPhone, dcHandler);
mDataConnectionTracker = this;
registerForAllEvents();
update();
mApnObserver = new ApnChangeObserver();
phone.getContext().getContentResolver().registerContentObserver(
Telephony.Carriers.CONTENT_URI, true, mApnObserver);
initApnContexts();
for (ApnContext apnContext : mApnContexts.values()) {
// Register the reconnect and restart actions.
filter = new IntentFilter();
filter.addAction(INTENT_RECONNECT_ALARM + '.' + apnContext.getApnType());
mPhone.getContext().registerReceiver(mIntentReceiver, filter, null, mPhone);
}
// Add Emergency APN to APN setting list by default to support EPDN in sim absent cases
initEmergencyApnSetting();
addEmergencyApnSetting();
mProvisionActionName = "com.android.internal.telephony.PROVISION" + phone.getPhoneId();
mSettingsObserver = new SettingsObserver(mPhone.getContext(), this);
registerSettingsObserver();
//[FEATURE]-Add-BEGIN by (songzhihao@paxsz.com) 2021/03/30 for network occour problem.
SystemProperties.set(paxRestRadio, "120000");
//[FEATURE]-Add-END by (songzhihao@paxsz.com) 2021/03/30 for network occour problem.
}
6.2 registerForAllEvents监听事件
这里最重要的还是EVENT_DATA_CONNECTION_ATTACHED 表示modem 注网完成接下来进行拨号的状态。
private void registerForAllEvents() {
mPhone.mCi.registerForAvailable(this, DctConstants.EVENT_RADIO_AVAILABLE, null);
mPhone.mCi.registerForOffOrNotAvailable(this,
DctConstants.EVENT_RADIO_OFF_OR_NOT_AVAILABLE, null);
mPhone.mCi.registerForDataNetworkStateChanged(this,
DctConstants.EVENT_DATA_STATE_CHANGED, null);
// Note, this is fragile - the Phone is now presenting a merged picture
// of PS (volte) & CS and by diving into its internals you're just seeing
// the CS data. This works well for the purposes this is currently used for
// but that may not always be the case. Should probably be redesigned to
// accurately reflect what we're really interested in (registerForCSVoiceCallEnded).
mPhone.getCallTracker().registerForVoiceCallEnded(this,
DctConstants.EVENT_VOICE_CALL_ENDED, null);
mPhone.getCallTracker().registerForVoiceCallStarted(this,
DctConstants.EVENT_VOICE_CALL_STARTED, null);
registerServiceStateTrackerEvents();
// SubscriptionManager.registerForDdsSwitch(this,
// DctConstants.EVENT_CLEAN_UP_ALL_CONNECTIONS, null);
mPhone.mCi.registerForPcoData(this, DctConstants.EVENT_PCO_DATA_RECEIVED, null);
}
public void registerServiceStateTrackerEvents() {
mPhone.getServiceStateTracker().registerForDataConnectionAttached(this,
DctConstants.EVENT_DATA_CONNECTION_ATTACHED, null);
mPhone.getServiceStateTracker().registerForDataConnectionDetached(this,
DctConstants.EVENT_DATA_CONNECTION_DETACHED, null);
mPhone.getServiceStateTracker().registerForDataRoamingOn(this,
DctConstants.EVENT_ROAMING_ON, null);
mPhone.getServiceStateTracker().registerForDataRoamingOff(this,
DctConstants.EVENT_ROAMING_OFF, null);
mPhone.getServiceStateTracker().registerForPsRestrictedEnabled(this,
DctConstants.EVENT_PS_RESTRICT_ENABLED, null);
mPhone.getServiceStateTracker().registerForPsRestrictedDisabled(this,
DctConstants.EVENT_PS_RESTRICT_DISABLED, null);
mPhone.getServiceStateTracker().registerForDataRegStateOrRatChanged(this,
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