android|Android 数据连接分析 android|data部分

把网络接入过程简单分为三个阶段
触发阶段
—-该阶段是由各种不同事件触发的，比如SIM载入完毕、PS域Attach成功、通话结束、APN改变等，该阶段的最终都是要调用setupDataOnConnectableApns()方法；
准备连接阶段
—-该阶段是指，在DcTracker收到建立连接的请求之后，需要进行一系列有效性检测，比如APN是否已经激活、PS是否已经就绪、用户是否打开网络开关等，然后创建/找到核实的DataConnection对象，准备发起连接请求。
发送连接命令阶段
—-该阶段是指，在DataConnection收到DcTracker的请求之后，将请求转交给RILJ的过程，RILJ通过socket将请求发送到了RILD，RILD根据请求类型再将AT指令发送到Modem层，由底层完成信令的发送和接收。简单概括就是如下步骤，此处创建的DcAsyncChannel是双向的。

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1、触发条件

//漫游打开关闭（EVENT_ROAMING_ON/EVENT_ROAMING_OFF事件） static final String REASON_ROAMING_ON = "roamingOn"; static final String REASON_ROAMING_OFF = "roamingOff"; //PS attach（STATE_IN_SERVICE） static final String REASON_DATA_ATTACHED = "dataAttached"; //APN Changed（EVENT_APN_CHANGED） static final String REASON_APN_CHANGED = "apnChanged"; //通话结束 static final String REASON_VOICE_CALL_ENDED = "2GVoiceCallEnded"; //SIM载入完毕（EVENT_RECORDS_LOADED 事件） static final String REASON_SIM_LOADED = "simLoaded"; //网络模式改变（EVENT_DATA_RAT_CHANGED 事件） static final String REASON_NW_TYPE_CHANGED = "nwTypeChanged";

2、有效性及状态检查在触发条件满足后都会调用setupDataOnConnectableApns(String reason)
之后会调用trySetupData,在trySetupData里面会进行有效性检测

private boolean trySetupData(ApnContext apnContext, ArrayList waitingApns) { // Allow SETUP_DATA request for E-APN to be completed during emergency call and MOBILE DATA On/Off cases as well. boolean isEmergencyApn = apnContext.getApnType().equals(PhoneConstants.APN_TYPE_EMERGENCY); final ServiceStateTracker sst = mPhone.getServiceStateTracker(); boolean desiredPowerState = sst.getDesiredPowerState(); boolean checkUserDataEnabled = !(apnContext.getApnType().equals(PhoneConstants.APN_TYPE_IMS)); if (apnContext.isConnectable() && (isEmergencyApn || (isDataAllowed(apnContext) && getAnyDataEnabled(checkUserDataEnabled) && !isEmergency()))) {if (apnContext.getState() == DctConstants.State.FAILED) { apnContext.setState(DctConstants.State.IDLE); } int radioTech = mPhone.getServiceState().getRilDataRadioTechnology(); apnContext.setConcurrentVoiceAndDataAllowed(sst.isConcurrentVoiceAndDataAllowed()); if (apnContext.getState() == DctConstants.State.IDLE) { if (waitingApns == null) { waitingApns = buildWaitingApns(apnContext.getApnType(), radioTech); } if (waitingApns.isEmpty()) { notifyNoData(DcFailCause.MISSING_UNKNOWN_APN, apnContext); notifyOffApnsOfAvailability(apnContext.getReason()); return false; } else { apnContext.setWaitingApns(waitingApns); } } boolean retValue = https://www.it610.com/article/setupData(apnContext, radioTech); notifyOffApnsOfAvailability(apnContext.getReason()); return retValue; } }

条件1：apnContext.isConnectable()

public boolean isConnectable() { return isReady() && ((mState == DctConstants.State.IDLE) || (mState == DctConstants.State.SCANNING) || (mState == DctConstants.State.RETRYING) || (mState == DctConstants.State.FAILED)); }

其中isReady()就是检查APN type有没有使能，所以在数据链接之前一定要调用ApnContext的setEnabled()将要打开的数据类型对应的APN使能；然后就是检查APN的状态，这个状态会在DataConnection状态机随着联网状态的变迁而改变。
条件2：isEmergencyApn 是否是紧急APN
条件3：isDataAllowed(apnContext)

private boolean isDataAllowed(ApnContext apnContext) { return apnContext.isReady() && isDataAllowed(); }protected boolean isDataAllowed() { final boolean internalDataEnabled; synchronized (mDataEnabledLock) { internalDataEnabled = mInternalDataEnabled; }boolean attachedState = mAttached.get(); boolean desiredPowerState = mPhone.getServiceStateTracker().getDesiredPowerState(); IccRecords r = mIccRecords.get(); boolean recordsLoaded = false; if (r != null) { recordsLoaded = r.getRecordsLoaded(); }//FIXME always attach boolean psRestricted = mIsPsRestricted; int phoneNum = TelephonyManager.getDefault().getPhoneCount(); if (phoneNum > 1) { attachedState = true; psRestricted = false; } int dataSub = SubscriptionManager.getDefaultDataSubId(); boolean defaultDataSelected = SubscriptionManager.isValidSubscriptionId(dataSub); PhoneConstants.State state = PhoneConstants.State.IDLE; if (mPhone.getCallTracker() != null) { state = mPhone.getCallTracker().getState(); } boolean allowed = (attachedState || mAutoAttachOnCreation) && recordsLoaded && (state == PhoneConstants.State.IDLE || mPhone.getServiceStateTracker().isConcurrentVoiceAndDataAllowed()) && internalDataEnabled && defaultDataSelected && (!mPhone.getServiceState().getDataRoaming() || getDataOnRoamingEnabled()) && //!mIsPsRestricted && !psRestricted && desiredPowerState;

—-判断是否已经ATTACH成功，SIM是否初始化完毕，当前手机服务是否支持，漫游下是否允许上网等
条件4：getAnyDataEnabled(checkUserDataEnabled)
—-该条件主要判断用户是否打开了数据开关
这部分代码很混乱，如果出现问题得一一排查
3、找到可用的APN 其中waitingApns = buildWaitingApns(apnContext.getApnType(), radioTech)便是找到可用的APN
buildWaitingApns中主要的逻辑有两个：
1、如果用户是否设置了Preferred，该值通过以下代码读取的：

usePreferred = ! mPhone.getContext().getResources().getBoolean(com.android. internal.R.bool.config_dontPreferApn);

如果用户设置了Preferred APN，并且mPreferredApn不为空（mPreferredApn来自于数据业务APN参数的创建createAllApnList中保存的，例如用户手动选择了APN TYPE那么这个APN就会被保留下来）因此此时waitingApns就会等于mPreferredApn
2、如果用户没有设置Preferred APN，那么就会在mAllApnSettings（来自于createAllApnList）中去寻找可用的APN，并将所有的可用的APN放在waitingApns中
最终联网采用的是waitingApns0
4、找到/创建DataConnection状态机

private boolean setupData(ApnContext apnContext, int radioTech) { if (dcac == null) { dcac = findFreeDataConnection(); if (dcac == null) { dcac = createDataConnection(); } } apnContext.setDataConnectionAc(dcac); apnContext.setApnSetting(apnSetting); apnContext.setState(DctConstants.State.CONNECTING); mPhone.notifyDataConnection(apnContext.getReason(), apnContext.getApnType()); Message msg = obtainMessage(); msg.what = DctConstants.EVENT_DATA_SETUP_COMPLETE; msg.obj = apnContext; dcac.bringUp(apnContext, getInitialMaxRetry(), profileId, radioTech, mAutoAttachOnCreation,msg); return true;

这个方法内部主要完成了两个任务：
1、更新当前APN参数的状态并把状态发送到系统中(还是通过notifyDataConnection()来完成)
2、通过DcAsyncChannel的bringUp()方法发起连接请求
这里显示通过findFreeDataConnection()方法搜索可用的DcAsyncChannel，找不到的话就通过createDataConnection()创建，如果没有找到，就需要创建新的DcAsyncChannel
/* Return the DC AsyncChannel for the new data connection /
private DcAsyncChannel createDataConnection() {

int id = mUniqueIdGenerator.getAndIncrement(); DataConnection conn = DataConnection.makeDataConnection(mPhone, id,this, mDcTesterFailBringUpAll, mDcc); mDataConnections.put(id, conn); DcAsyncChannel dcac = new DcAsyncChannel(conn, LOG_TAG); int status = dcac.fullyConnectSync(mPhone.getContext(), this, conn.getHandler()); if (status == AsyncChannel.STATUS_SUCCESSFUL) { mDataConnectionAcHashMap.put(dcac.getDataConnectionIdSync(), dcac); //将创建好的DcAsyncChannel保存起来，以便下一次链接的时候可以找到可用的DcAsyncChannel } return dcac; }

创建DcAsyncChannel通道，是链接DcTracker和DataConnection的通道，但是他们不在同一个线程中，在DcTrackerBase的构造中new了一个新的HandlerThread，并将looper给了DcController和DataConnection。
为什么要闯将DcAsyncChannel通道，而不直接将DcTracker消息传到DataConnection中去呢？
因为在DcTracker中有需要同步获取DataConnection中的情况，比如在findFreeDataConnection中调用了

dcac.isInactiveSync() private DcAsyncChannel findFreeDataConnection() { for (DcAsyncChannel dcac : mDataConnectionAcHashMap.values()) { if (dcac.isInactiveSync() && dataConnectionNotInUse(dcac)) { return dcac; } } return null; }public boolean isInactiveSync() { boolean value; if (isCallerOnDifferentThread()) { Message response = sendMessageSynchronously(REQ_IS_INACTIVE); if ((response != null) && (response.what == RSP_IS_INACTIVE)) { value = https://www.it610.com/article/rspIsInactive(response); } else { value = false; } } else { value = mDc.getIsInactive(); } return value; }

其中的sendMessageSynchronously(REQ_IS_INACTIVE); 即需要获取DataConnection中的是否处于INACTIVE状态，这不能是异步的。
5、通过DcAsyncChannel将消息传入状态机将apnContext通过dcac传入DataConnection状态机进行数据连接

dcac.bringUp(apnContext, getInitialMaxRetry(), profileId, radioTech, mAutoAttachOnCreation,msg);

6、状态机状态轮转 【android|Android 数据连接分析】 DataConnection默认状态是DcInactiveState,首先会在DcInactiveState调用onConnect去调用setupDataCall

private void onConnect(ConnectionParams cp) { // msg.obj will be returned in AsyncResult.userObj; Message msg = obtainMessage(EVENT_SETUP_DATA_CONNECTION_DONE, cp); msg.obj = cp; int authType = mApnSetting.authType; if (authType == -1) { authType = TextUtils.isEmpty(mApnSetting.user) ? RILConstants.SETUP_DATA_AUTH_NONE : RILConstants.SETUP_DATA_AUTH_PAP_CHAP; }String protocol; if (mPhone.getServiceState().getDataRoaming()) { protocol = mApnSetting.roamingProtocol; } else { protocol = mApnSetting.protocol; }mPhone.mCi.setupDataCall( Integer.toString(cp.mRilRat + 2), Integer.toString(cp.mProfileId), mApnSetting.apn, mApnSetting.user, mApnSetting.password, Integer.toString(authType), protocol, msg); }

在onConnect会包装一个EVENT_SETUP_DATA_CONNECTION_DONE消息在msg中，这个消息会一并发往RILJ->RILD，当RILD返回响应时会携带这消息并发出来，DataConnection状态机的DcActivatingState会扑捉到此消息进行状态机轮状，然后这里面全是状态机轮状来维护网络的链接状态：