Android4.4 RIL短信接收流程分析

最近有客户反馈Android接收不到短信，于是一头扎进RIL里面找原因。最后发现不是RIL的问题，而是BC72上报
短信的格式不对，AT+CNMA=1无作用等几个小问题导致的。尽管问题不在RIL，但总算把RIL短信接收流程搞清楚了。

接收到新信息的log：

D/ATC ( 1269): AT< +CMT:,27
D/ATC ( 1268): AT< 0891683108705505F0040d91683117358313f500009101329154922307ea31da2c36a301
D/RILJ ( 1792): [UNSL]< UNSOL_RESPONSE_NEW_SMS
D/SmsMessage( 1792): SMS SC address: +8613800755500
V/SmsMessage( 1792): SMS originating address: +8613715338315
V/SmsMessage( 1792): SMS TP-PID:0 data coding scheme: 0
D/SmsMessage( 1792): SMS SC timestamp: 1571831129000
V/SmsMessage( 1792): SMS message body (raw): 'jchfbfh'
D/GsmInboundSmsHandler( 1776): Idle state processing message type 1
D/GsmInboundSmsHandler( 1776): acquired wakelock, leaving Idle state
D/GsmInboundSmsHandler( 1776): entering Delivering state
D/GsmInboundSmsHandler( 1776): URI of new row -> content://raw/3
D/RILJ ( 1775): [3706]> SMS_ACKNOWLEDGE true 0
D/RILC ( 1254): onRequest: SMS_ACKNOWLEDGE
D/ATC ( 1254): AT> AT+CNMA=1
D/ATC ( 1254): AT< OK
D/RILJ ( 1775): [3706]< SMS_ACKNOWLEDGE
D/GsmInboundSmsHandler( 1775): Delivering SMS to: com.android.mms com.android.mms.transaction.PrivilegedSmsReceiver
E/GsmInboundSmsHandler( 1775): unexpected BroadcastReceiver action: android.provider.Telephony.SMS_RECEIVED
D/GsmInboundSmsHandler( 1775): successful broadcast, deleting from raw table.
D/SmsMessage( 2124): SMS SC address: +8613800755500
D/GsmInboundSmsHandler( 1775): Deleted 1 rows from raw table.
D/GsmInboundSmsHandler( 1775): ordered broadcast completed in: 276 ms
D/GsmInboundSmsHandler( 1775): leaving Delivering state
D/GsmInboundSmsHandler( 1775): entering Delivering state
D/GsmInboundSmsHandler( 1775): leaving Delivering state
D/GsmInboundSmsHandler( 1775): entering Idle state
V/SmsMessage( 2124): SMS originating address: +8613715338315
V/SmsMessage( 2124): SMS TP-PID:0 data coding scheme: 0
D/SmsMessage( 2124): SMS SC timestamp: 1572253549000
V/SmsMessage( 2124): SMS message body (raw): 'jchfbfh'
D/GsmInboundSmsHandler( 1775): Idle state processing message type 5
D/GsmInboundSmsHandler( 1775): mWakeLock released

一、短信接收

1. vendor ril接收到modem上报的短信息

hardware/ril/reference-ril/reference-ril.c

static void onUnsolicited (const char *s, const char *sms_pdu)
{
    ... ...
    if (strStartsWith(s, "+CMT:")) {
        RIL_onUnsolicitedResponse (
            RIL_UNSOL_RESPONSE_NEW_SMS,                             /* 上报UNSOL_RESPONSE_NEW_SMS消息 */
            sms_pdu, strlen(sms_pdu));
    }
    ... ...
}

2. RILD把短信息发送到RILJ

hardware/ril/libril/ril.cpp

extern "C"
void RIL_onUnsolicitedResponse(int unsolResponse, void *data,
                                size_t datalen)
{
    ... ...
    unsolResponseIndex = unsolResponse - RIL_UNSOL_RESPONSE_BASE;    /* 找出消息在s_unsolResponses[]的索引 */
    ... ...

    switch (s_unsolResponses[unsolResponseIndex].wakeType) {         /* 禁止进入休眠 */
        case WAKE_PARTIAL:
            grabPartialWakeLock();
            shouldScheduleTimeout = true;
        break;
        ... ...
    }
    ... ...
    ret = s_unsolResponses[unsolResponseIndex]                       /* 调用消息处理函数responseString() */
                .responseFunction(p, data, datalen);
    ... ...

    ret = sendResponse(p);                                           /* 发送Parcel中的信息内容到服务端RILJ */
}

static UnsolResponseInfo s_unsolResponses[] = {
... ...
/* 消息对应的消息处理函数，新信息到来会唤醒系统 */
{RIL_UNSOL_RESPONSE_NEW_SMS, responseString, WAKE_PARTIAL},
... ...
}；

static int responseString(Parcel &p, void *response, size_t responselen) {
    /* one string only */
    startResponse;
    appendPrintBuf("%s%s", printBuf, (char*)response);
    closeResponse;

    writeStringToParcel(p, (const char *)response);                  /* 把字符串格式的信息存到Parcel容器中 */

    return ;
}

二、解析短信息

1. RILJ获取短信息

frameworks/opt/telephony/src/java/com/android/internal/telephony/RIL.java

private void
processUnsolicited (Parcel p) {
    ... ...
    case RIL_UNSOL_RESPONSE_NEW_SMS: ret =  responseString(p); break;
    ... ...

    switch(response) {
        ... ...
        case RIL_UNSOL_RESPONSE_NEW_SMS: {
            if (RILJ_LOGD) unsljLog(response);                        /* 参考log：[UNSL]< UNSOL_RESPONSE_NEW_SMS */
            // FIXME this should move up a layer
            String a[] = new String[2];

            a[1] = (String)ret;

            SmsMessage sms;

            sms = SmsMessage.newFromCMT(a);                           /* 解析PDU格式的短信息 */
            if (mGsmSmsRegistrant != null) {
                mGsmSmsRegistrant
                    .notifyRegistrant(new AsyncResult(null, sms, null));
            }
            break;
        }
        ... ...
    }
    ... ...
}

private Object
responseString(Parcel p) {
    String response;

    response = p.readString();                                                         /* 信息内容转换成Object */

    return response;
}

2. 解析短信息

SmsMessage.newFromCMT(a);根据import android.telephony.SmsMessage，得知代码路径：

frameworks/opt/telephony/src/java/android/telephony/SmsMessage.java

public static SmsMessage newFromCMT(String[] lines) {
    // received SMS in 3GPP format
    SmsMessageBase wrappedMessage =
            com.android.internal.telephony.gsm.SmsMessage.newFromCMT(lines);       /* 是对另一个newFromCMT的封装，因为有gsm和cdma两种短信，
                                                                                    * 即cdma中也有newFromCMT，根据情况按需选择
                                                                                    */

    return new SmsMessage(wrappedMessage);
}

com.android.internal.telephony.gsm.SmsMessage.newFromCMT(lines)的实现在

frameworks/opt/telephony/src/java/com/android/internal/telephony/gsm/SmsMessage.java

public class SmsMessage extends SmsMessageBase {

    ... ...

    public static SmsMessage newFromCMT(String[] lines) {
        try {
            SmsMessage msg = new SmsMessage();
            msg.parsePdu(IccUtils.hexStringToBytes(lines[1]));               /* 解析PDU短信 */
            return msg;
        } catch (RuntimeException ex) {
            Rlog.e(LOG_TAG, "SMS PDU parsing failed: ", ex);
            return null;
        }
    }

    ... ...
}

IccUtils.hexStringToBytes(lines[1])把十六进制的字符串转换成字节数组msg.parsePdu()解析这个数组的内容，最后获得短信内容
frameworks/opt/telephony/src/java/com/android/internal/telephony/gsm/SmsMessage.java

private void parsePdu(byte[] pdu) {
    ... ...
    mScAddress = p.getSCAddress(); 

    if (mScAddress != null) {
        if (VDBG) Rlog.d(LOG_TAG, "SMS SC address: " + mScAddress);          /* 参考log：SMS SC address: +8613800755500 */
    }

    ... ...
    mMti = firstByte & 0x3;
    switch (mMti) {
        ... ...
          case 3: //GSM 03.40 9.2.3.1: MTI == 3 is Reserved.
                  //This should be processed in the same way as MTI == 0 (Deliver)
              parseSmsDeliver(p, firstByte);                                   /* 对短信类型为Deliver的短信进行解析 */
              break;
           ... ...
      }
    ... ...
}

private void parseSmsDeliver(PduParser p, int firstByte) {
    ... ...
    mOriginatingAddress = p.getAddress();                                                                                                                

    if (mOriginatingAddress != null) {
        if (VDBG) Rlog.v(LOG_TAG, "SMS originating address: "                /* 参考log: SMS originating address: +861371533xxxx */
                + mOriginatingAddress.address);
    }

    ... ...

    mProtocolIdentifier = p.getByte();

    // TP-Data-Coding-Scheme
    // see TS 23.038
    mDataCodingScheme = p.getByte();

    if (VDBG) {
        Rlog.v(LOG_TAG, "SMS TP-PID:" + mProtocolIdentifier
                + " data coding scheme: " + mDataCodingScheme);               /* 参考log: SMS TP-PID:0 data coding scheme: 0 */
    }

    mScTimeMillis = p.getSCTimestampMillis();

    if (VDBG) Rlog.d(LOG_TAG, "SMS SC timestamp: " + mScTimeMillis);          /* 参考log：SMS SC timestamp: 1571831129000 */

    boolean hasUserDataHeader = (firstByte & 0x40) == 0x40;

    parseUserData(p, hasUserDataHeader);                                      /* 解析信息有效内容 */

    ... ...
}     

private void parseUserData(PduParser p, boolean hasUserDataHeader) {
    ... ...
    if (VDBG) Rlog.v(LOG_TAG, "SMS message body (raw): '" + mMessageBody + "'");    /* 短信内容，参考log: SMS message body (raw): 'jchfbfh' */
    ... ...
} 

三、处理短信息

对用户有效的短信内容，最终保存在类型为String的mMessageBody变量中，该变量属于SmsMessageBase抽象类，而
SmsMessage继承于SmsMessageBase。
        回到前面frameworks/opt/telephony/src/java/com/android/internal/telephony/RIL.java中processUnsolicited(),
sms = SmsMessage.newFromCMT(a);解析完短信息后，返回一个SmsMessage并通知上层应用。

frameworks/opt/telephony/src/java/com/android/internal/telephony/RIL.java

mGsmSmsRegistrant
    .notifyRegistrant(new AsyncResult(null, sms, null));                             /* 把sms转成Object类型 */

frameworks/base/core/java/android/os/AsyncResult.java

public class AsyncResult
{
    ... ...
    /** please note, this sets m.obj to be this */
    public
    AsyncResult (Object uo, Object r, Throwable ex)
    {
        userObj = uo;
        result = r;
        exception = ex;
    }
    ... ...
}

根据mGsmSmsRegistrant.notifyRegistrant(new AsyncResult(null, sms, null));找到mGsmSmsRegistrant注册的代码：

frameworks/opt/telephony/src/java/com/android/internal/telephony/BaseCommands.java

public abstract class BaseCommands implements CommandsInterface {
    ... ...

    @Override
    public void setOnNewGsmSms(Handler h, int what, Object obj) {     /* mGsmSmsRegistrant.notifyRegistrant(new AsyncResult(null, sms, null))中的mGsmSmsRegistrant是在这里创建的 */
        mGsmSmsRegistrant = new Registrant (h, what, obj);
    }

    ... ...
}

封装消息EVENT_NEW_SMS消息

frameworks/base/core/java/android/os/Registrant.java

public class Registrant
{
    public
    Registrant(Handler h, int what, Object obj)                       /* 传入需要处理消息为what的事件处理Handler h，obj为事件内容，参考phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null); */
    {
        refH = new WeakReference(h);
        this.what = what;
        userObj = obj;
    } 

    ... ...

    /**
     * This makes a copy of @param ar
     */
    public void
    notifyRegistrant(AsyncResult ar)                                  /* 参考mGsmSmsRegistrant.notifyRegistrant(new AsyncResult(null, sms, null)) */
    {
        internalNotifyRegistrant (ar.result, ar.exception);           /* ar.result为sms */
    }

    /*package*/ void
    internalNotifyRegistrant (Object result, Throwable exception)     /* internalNotifyRegistrant (sms, Throwable exception) */
    {
        Handler h = getHandler();

        if (h == null) {
            clear();
        } else {
            Message msg = Message.obtain();                           /* 创建一个消息 */

            msg.what = what;                                          /* 消息类型EVENT_NEW_SMS */

            msg.obj = new AsyncResult(userObj, result, exception);    /* 消息内容sms */

            h.sendMessage(msg);                                       /* 发送消息到注册了这个消息的Handler，参考phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null);的getHandler() */
        }
    }

    ... ...
}  

然而BaseCommands是一个抽象类，实现了CommandsInterface中的setOnNewGsmSms接口，这个接口由GsmInboundSmsHandler调用
（phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null)），也就是说GsmInboundSmsHandler的getHandler()是EVENT_NEW_SMS
的监听者，也就是说frameworks/opt/telephony/src/java/com/android/internal/telephony/RIL.java中mGsmSmsRegistrant.notifyRegistrant(new AsyncResult(null, sms, null))
调用之后，会触发GsmInboundSmsHandler中getHandler()的Handler对EVENT_NEW_SMS消息进行解析。这个Handler肯定是GsmInboundSmsHandler
实例化的对象中的，这个对象在什么时候，在哪里创建的，暂且不管。我们只管EVENT_NEW_SMS这个消息从哪里来，然后到哪里去
就行了。

./frameworks/opt/telephony/src/java/com/android/internal/telephony/ImsSMSDispatcher.java

public final class ImsSMSDispatcher extends SMSDispatcher {
    ... ...
    mGsmInboundSmsHandler = GsmInboundSmsHandler.makeInboundSmsHandler(phone.getContext(),         /* 获取mGsmInboundSmsHandler，并启动状态机 */
            storageMonitor, phone);
    ... ...
}

./frameworks/opt/telephony/src/java/com/android/internal/telephony/gsm/GsmInboundSmsHandler.java

public class GsmInboundSmsHandler extends InboundSmsHandler {
    ... ...
    /**
     * Create a new GSM inbound SMS handler.
     */
    private GsmInboundSmsHandler(Context context, SmsStorageMonitor storageMonitor,
            PhoneBase phone) {
        super("GsmInboundSmsHandler", context, storageMonitor, phone,                              /* 构造GsmInboundSmsHandler时，通过super()调用InboundSmsHandler的构造函数 */
                GsmCellBroadcastHandler.makeGsmCellBroadcastHandler(context, phone));
        phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null);                               /* 注册EVENT_NEW_SMS消息 */
        mDataDownloadHandler = new UsimDataDownloadHandler(phone.mCi);
    }

    ... ...

    /**
     * Wait for state machine to enter startup state. We can't send any messages until then.
     */
    public static GsmInboundSmsHandler makeInboundSmsHandler(Context context,
            SmsStorageMonitor storageMonitor, PhoneBase phone) {
        GsmInboundSmsHandler handler = new GsmInboundSmsHandler(context, storageMonitor, phone);   /* 实例化GsmInboundSmsHandler */
        handler.start();                                                                           /* 抽象类InboundSmsHandler继承与StateMachine，而GsmInboundSmsHandler继承于InboundSmsHandler，
                                                                                                    * GsmInboundSmsHandler调用启动状态机方法start()
                                                                                                    */
        return handler;
    }

    ... ...
}

./frameworks/opt/telephony/src/java/com/android/internal/telephony/InboundSmsHandler.java

public abstract class InboundSmsHandler extends StateMachine {
    ... ...
    protected InboundSmsHandler(String name, Context context, SmsStorageMonitor storageMonitor,
            PhoneBase phone, CellBroadcastHandler cellBroadcastHandler) {
        ... ...

        addState(mDefaultState);                                                                   /* 构造InboundSmsHandler时，添加状态机的状态 */
        addState(mStartupState, mDefaultState);
        addState(mIdleState, mDefaultState);
        addState(mDeliveringState, mDefaultState);
        addState(mWaitingState, mDeliveringState);

        setInitialState(mStartupState);                                                            /* 初始化状态机 */
        if (DBG) log("created InboundSmsHandler");
    }

    ... ...    

    class IdleState extends State {
        @Override
        public void enter() {
            if (DBG) log("entering Idle state");
            sendMessageDelayed(EVENT_RELEASE_WAKELOCK, WAKELOCK_TIMEOUT);
        }

        @Override
        public void exit() {
            mWakeLock.acquire();
            if (DBG) log("acquired wakelock, leaving Idle state");
        }

        @Override
        public boolean processMessage(Message msg) {
            if (DBG) log("Idle state processing message type " + msg.what);
            switch (msg.what) {
                case EVENT_NEW_SMS:                                                                /* 空闲时，接收到短信 */
                case EVENT_BROADCAST_SMS:
                    deferMessage(msg);
                    transitionTo(mDeliveringState);                                                /* 转到mDeliveringState */
                    return HANDLED;

                ... ...
            }
        }
    }
        ... ...

    class DeliveringState extends State {                                                          /* 转到mDeliveringState状态 */
        @Override
        public void enter() {
            if (DBG) log("entering Delivering state");
        }

        @Override
        public void exit() {
            if (DBG) log("leaving Delivering state");
        }

        @Override
        public boolean processMessage(Message msg) {
            switch (msg.what) {
                case EVENT_NEW_SMS:
                    // handle new SMS from RIL
                    handleNewSms((AsyncResult) msg.obj);                                           /* 处理新SMS */
                    sendMessage(EVENT_RETURN_TO_IDLE);                                             /* 处理完回到空闲状态 */
                    return HANDLED;

                ... ...
            }
        }
            ... ...
    }
}

void handleNewSms(AsyncResult ar) {
    ... ...
    SmsMessage sms = (SmsMessage) ar.result;
    result = dispatchMessage(sms.mWrappedSmsMessage);
    ... ...
}

public int dispatchMessage(SmsMessageBase smsb) {
    ... ...
    return dispatchMessageRadioSpecific(smsb);
    ... ...
}

通过以上流程可以了解到，当状态机接收到SMS后，对消息进行分发，针对type zero, SMS-PP data download,
和3GPP/CPHS MWI type SMS判断，如果是Normal SMS messages，则调用dispatchNormalMessage(smsb)，然后创建
一个InboundSmsTracker对象，把信息保存到raw table，然后在通过sendMessage(EVENT_BROADCAST_SMS, tracker)
把消息广播出去。

./frameworks/opt/telephony/src/java/com/android/internal/telephony/InboundSmsHandler.java

class DeliveringState extends State {
    ... ...
    public boolean processMessage(Message msg) {
        switch (msg.what) {
            ... ...
            case EVENT_BROADCAST_SMS:                                                         /* 接收到EVENT_BROADCAST_SMS消息并处理 */
                // if any broadcasts were sent, transition to waiting state
                if (processMessagePart((InboundSmsTracker) msg.obj)) {
                    transitionTo(mWaitingState);
                }
                return HANDLED;
            ... ...
        }
    }
    ... ...

}

boolean processMessagePart(InboundSmsTracker tracker) {
    ... ...
    BroadcastReceiver resultReceiver = new SmsBroadcastReceiver(tracker);                    /* 创建一个广播接收者，用来处理短信广播的结果 */
    ... ...
    intent = new Intent(Intents.SMS_DELIVER_ACTION);                                         /* 设置当前intent的action为SMS_DELIVER_ACTION */

    // Direct the intent to only the default SMS app. If we can't find a default SMS app
    // then sent it to all broadcast receivers.
    ComponentName componentName = SmsApplication.getDefaultSmsApplication(mContext, true);   /* 这个action只会发送给carrier app，而且carrier app可以通过set result为RESULT_CANCELED来终止这个广播 */
    if (componentName != null) {
        // Deliver SMS message only to this receiver
        intent.setComponent(componentName);
        log("Delivering SMS to: " + componentName.getPackageName() +
                " " + componentName.getClassName());
    }
    ... ...
    dispatchIntent(intent, android.Manifest.permission.RECEIVE_SMS,                          /* 广播intent */
                AppOpsManager.OP_RECEIVE_SMS, resultReceiver);
    ... ...
}

private final class SmsBroadcastReceiver extends BroadcastReceiver {
    ... ...
    public void onReceive(Context context, Intent intent) {
        ... ...
        // Now that the intents have been deleted we can clean up the PDU data.
        if (!Intents.DATA_SMS_RECEIVED_ACTION.equals(action)
                && !Intents.DATA_SMS_RECEIVED_ACTION.equals(action)
                && !Intents.WAP_PUSH_RECEIVED_ACTION.equals(action)) {
            loge("unexpected BroadcastReceiver action: " + action);
        }

        int rc = getResultCode();
        if ((rc != Activity.RESULT_OK) && (rc != Intents.RESULT_SMS_HANDLED)) {
            loge("a broadcast receiver set the result code to " + rc
                    + ", deleting from raw table anyway!");
        } else if (DBG) {
            log("successful broadcast, deleting from raw table.");
        }

        deleteFromRawTable(mDeleteWhere, mDeleteWhereArgs);
        sendMessage(EVENT_BROADCAST_COMPLETE);                                               /* 成功广播 */

        ... ...
    }
    ... ...
}

到这里，在应用层注册具有Intents.SMS_RECEIVED_ACTION这样action的广播，就可以获取到短信了。