void Control::AssignmentCompleteHandler(const L3AssignmentComplete *confirm, TCHFACCHLogicalChannel *TCH)
{
	// The assignment complete handler is used to
	// tie together split transactions across a TCH assignment
	// in non-VEA call setup.

	assert(TCH);
	assert(confirm);
	LOG(DEBUG) << *confirm;

	// Check the transaction table to know what to do next.
	TransactionEntry transaction;
	if (!gTransactionTable.find(TCH->transactionID(),transaction)) {
		LOG(WARN) << "Assignment Complete with no transaction record for ID " << TCH->transactionID();
		throw UnexpectedMessage();
	}
	LOG(INFO) << "service="<<transaction.service().type();

	// These "controller" functions don't return until the call is cleared.
	switch (transaction.service().type()) {
		case L3CMServiceType::MobileOriginatedCall:
			MOCController(transaction,TCH);
			break;
		case L3CMServiceType::MobileTerminatedCall:
			MTCController(transaction,TCH);
			break;
		default:
			LOG(WARN) << "unsupported service " << transaction.service();
			throw UnsupportedMessage(transaction.ID());
	}
	// If we got here, the call is cleared.
}

void Control::clearTransactionHistory( TransactionEntry& transaction )
{
	SIP::SIPEngine& engine = transaction.SIP();
	LOG(DEBUG) << engine.callID()<<" "<< transaction.ID();
	gSIPInterface.removeCall(engine.callID());
	gTransactionTable.remove(transaction.ID());
}

/**
	Check GSM signalling.
	Can block for up to 52 GSM L1 frames (240 ms) because LCH::send is blocking.
	@param transaction The call's TransactionEntry.
	@param LCH The call's logical channel (TCH/FACCH or SDCCH).
	@return true If the call was cleared.
*/
bool updateGSMSignalling(TransactionEntry &transaction, LogicalChannel *LCH, unsigned timeout=0)
{
	if (transaction.Q931State()==TransactionEntry::NullState) return true;

	// Any Q.931 timer expired?
	if (transaction.timerExpired()) {
		// Cause 0x66, "recover on timer expiry"
		abortCall(transaction,LCH,L3Cause(0x66));
		return true;
	}

	// Look for a control message from MS side.
	if (L3Frame *l3 = LCH->recv(timeout)) {
		// Check for lower-layer error.
		if (l3->primitive() == ERROR) return true;
		// Parse and dispatch.
		L3Message *l3msg = parseL3(*l3);
		delete l3;
		bool cleared = false;
		if (l3msg) {
			LOG(DEBUG) << "received " << *l3msg;
			cleared = callManagementDispatchGSM(transaction, LCH, l3msg);
			delete l3msg;
		}
		return cleared;
	}

	// If we are here, we have timed out, but assume the call is still running.
	return false;
}

void Pager::addID(const FuzzingL3MobileIdentity& newID, ChannelType chanType,
		TransactionEntry& transaction, unsigned wLife)
{
	transaction.Q931State(TransactionEntry::Paging);
	transaction.T3113().set(wLife);
	gTransactionTable.update(transaction);
	// Add a mobile ID to the paging list for a given lifetime.
	mLock.lock();
	// If this ID is already in the list, just reset its timer.
	// Uhg, another linear time search.
	// This would be faster if the paging list were ordered by ID.
	// But the list should usually be short, so it may not be worth the effort.
	for (PagingEntryList::iterator lp = mPageIDs.begin(); lp != mPageIDs.end(); ++lp) {
		if (lp->FuzzingID()==newID) {
			LOG(DEBUG) << newID << " already in table";
			lp->renew(wLife);
			mPageSignal.signal();
			mLock.unlock();
			return;
		}
	}
	// If this ID is new, put it in the list.
	mPageIDs.push_back(PagingEntry(newID,chanType,transaction.ID(),wLife));
	LOG(INFO) << newID << " added to table";
	mPageSignal.signal();
	mLock.unlock();
}

/**
	This is the standard call manangement loop, regardless of the origination type.
	This function returns when the call is cleared and the channel is released.
	@param transaction The transaction record for this call, will be cleared on exit.
	@param TCH The TCH+FACCH for the call.
*/
void callManagementLoop(TransactionEntry &transaction, TCHFACCHLogicalChannel* TCH)
{
	LOG(INFO) << transaction.subscriber() << " call connected";
	transaction.SIP().FlushRTP();
	// poll everything until the call is cleared
	while (!pollInCall(transaction,TCH)) { }
	clearTransactionHistory(transaction);
}

/**
	Force clearing on the SIP side.
	@param transaction The call transaction record.
*/
void forceSIPClearing(TransactionEntry& transaction)
{
	LOG(INFO) << "SIP state " << transaction.SIP().state();
	if (transaction.SIP().state()==SIP::Cleared) return;
	if (transaction.SIP().state()!=SIP::Clearing) {
		// This also changes the SIP state to "clearing".
		transaction.SIP().MODSendBYE();
	} else {
		transaction.SIP().MODResendBYE();
	}
	transaction.SIP().MODWaitForOK();
	gTransactionTable.update(transaction);
}

void TransactionTable::update(const TransactionEntry& value)
{
	// ID==0 is a non-valid special case.
	assert(value.ID());
	mLock.lock();
	if (mTable.find(value.ID())==mTable.end()) {
		mLock.unlock();
		LOG(WARN) << "attempt to update non-existent transaction entry with key " << value.ID();
		return;
	}
	mTable[value.ID()]=value;
	mLock.unlock();
}

void TransactionTable::add(const TransactionEntry& value)
{
	LOG(INFO) << "new transaction " << value;
	mLock.lock();
	mTable[value.ID()]=value;
	mLock.unlock();
}

/**
	Update vocoder data transfers in both directions.
	@param transaction The transaction object for this call.
	@param TCH The traffic channel for this call.
	@return True if anything was transferred.
*/
bool updateCallTraffic(TransactionEntry &transaction, TCHFACCHLogicalChannel *TCH)
{
	bool activity = false;

	SIPEngine& engine = transaction.SIP();


	// Transfer in the downlink direction (RTP->GSM).
	// Blocking call.  On average returns 1 time per 20 ms.
	// Returns non-zero if anything really happened.
	// Make the rxFrame buffer big enough for G.711.
	unsigned char rxFrame[160];
	if (engine.RxFrame(rxFrame)) {
		activity = true;
		TCH->sendTCH(rxFrame);
	}

	// Transfer in the uplink direction (GSM->RTP).
	// Flush FIFO to limit latency.
	unsigned maxQ = gConfig.getNum("GSM.MaxSpeechLatency");
	while (TCH->queueSize()>maxQ) delete[] TCH->recvTCH();
	if (unsigned char *txFrame = TCH->recvTCH()) {
		activity = true;
		// Send on RTP.
		engine.TxFrame(txFrame);
		delete[] txFrame;
	}

	// Return a flag so the caller will know if anything transferred.
	return activity;
}

/**
	Force clearing on the GSM side.
	@param transaction The call transaction record.
	@param LCH The logical channel.
	@param cause The L3 abort cause.
*/
void forceGSMClearing(TransactionEntry& transaction, LogicalChannel *LCH, const L3Cause& cause)
{
	LOG(INFO) << "Q.931 state " << transaction.Q931State();
	if (transaction.Q931State()==TransactionEntry::NullState) return;
	if (!transaction.clearing()) {
		LCH->send(L3Disconnect(1-transaction.TIFlag(),transaction.TIValue(),cause));
	}
	LCH->send(L3ReleaseComplete(1-transaction.TIFlag(),transaction.TIValue()));
	LCH->send(L3ChannelRelease());
	transaction.resetTimers();
	transaction.Q931State(TransactionEntry::NullState);
	LCH->send(RELEASE);
	gTransactionTable.update(transaction);
}

void Control::MOSMSController(const GSM::L3CMServiceRequest *req, GSM::LogicalChannel *LCH)
{
	assert(req);
	assert(req->serviceType().type() == GSM::L3CMServiceType::ShortMessage);
	assert(LCH);
	assert(LCH->type() != GSM::SACCHType);

	LOG(INFO) << "MOSMS, req " << *req;

	// If we got a TMSI, find the IMSI.
	// Note that this is a copy, not a reference.
	GSM::L3MobileIdentity mobileID = req->mobileID();
	resolveIMSI(mobileID,LCH);

	// Create a transaction record.
	TransactionEntry *transaction = new TransactionEntry(gConfig.getStr("SIP.Proxy.SMS").c_str(),mobileID,LCH);
	gTransactionTable.add(transaction);
	LOG(DEBUG) << "MOSMS: transaction: " << *transaction;

	// See GSM 04.11 Arrow Diagram A5 for the transaction
	// Step 1	MS->Network	CP-DATA containing RP-DATA
	// Step 2	Network->MS	CP-ACK
	// Step 3	Network->MS	CP-DATA containing RP-ACK
	// Step 4	MS->Network	CP-ACK

	// LAPDm operation, from GSM 04.11, Annex F:
	// """
	// Case A: Mobile originating short message transfer, no parallel call:
	// The mobile station side will initiate SAPI 3 establishment by a SABM command
	// on the DCCH after the cipher mode has been set. If no hand over occurs, the
	// SAPI 3 link will stay up until the last CP-ACK is received by the MSC, and
	// the clearing procedure is invoked.
	// """

	// FIXME: check provisioning

	if (gConfig.getNum("GSM.Authentication")||gConfig.getNum("GSM.Encryption")) {
		AuthenticationParameters authParams(mobileID);
		registerIMSI(authParams, LCH);
		authenticate(authParams, LCH);
	}

	// Let the phone know we're going ahead with the transaction.
	if (LCH->isDecrypting()) {
		LOG(INFO) << "Decryption ACTIVE for:" << mobileID << " CMServiceAccept NOT sent, because CipherModeCommand implies it.";
	}
	else {
		LOG(INFO) << "Decryption NOT active for: " << mobileID << " Sending CMServiceAccept";
		LCH->send(GSM::L3CMServiceAccept());
	}


	// Wait for SAP3 to connect.
	// The first read on SAP3 is the ESTABLISH primitive.
	delete getFrameSMS(LCH,GSM::ESTABLISH);

	// Step 1
	// Now get the first message.
	// Should be CP-DATA, containing RP-DATA.
	GSM::L3Frame *CM = getFrameSMS(LCH);
	LOG(DEBUG) << "data from MS " << *CM;
	if (CM->MTI()!=CPMessage::DATA) {
		LOG(NOTICE) << "unexpected SMS CP message with TI=" << CM->MTI();
		delete CM;
		throw UnexpectedMessage();
	}
	unsigned L3TI = CM->TI() | 0x08;
	transaction->L3TI(L3TI);

	// Step 2
	// Respond with CP-ACK.
	// This just means that we got the message.
	LOG(INFO) << "sending CPAck";
	LCH->send(CPAck(L3TI),3);

	// Parse the message in CM and process RP part.
	// This is where we actually parse the message and send it out.
	// FIXME -- We need to set the message ref correctly,
	// even if the parsing fails.
	// The compiler gives a warning here.  Let it.  It will remind someone to fix it.
	unsigned ref;
	bool success = false;
	try {
		CPData data;
		data.parse(*CM);
		LOG(INFO) << "CPData " << data;
		// Transfer out the RPDU -> TPDU -> delivery.
		ref = data.RPDU().reference();
		// This handler invokes higher-layer parsers, too.
		success = handleRPDU(transaction,data.RPDU());
	}
	catch (SMSReadError) {
		LOG(WARNING) << "SMS parsing failed (above L3)";
		// Cause 95, "semantically incorrect message".
		LCH->send(CPData(L3TI,RPError(95,ref)),3);
		delete CM;
		throw UnexpectedMessage();
	}
	catch (GSM::L3ReadError) {
		LOG(WARNING) << "SMS parsing failed (in L3)";
//.........这里部分代码省略.........

void Control::PagingResponseHandler(const L3PagingResponse* resp, LogicalChannel* DCCH)
{
    assert(resp);
    assert(DCCH);
    LOG(INFO) << *resp;

    // If we got a TMSI, find the IMSI.
    L3MobileIdentity mobileID = resp->mobileIdentity();
    if (mobileID.type()==TMSIType) {
        const char *IMSI = gTMSITable.IMSI(mobileID.TMSI());
        if (IMSI) mobileID = L3MobileIdentity(IMSI);
        else {
            // Don't try too hard to resolve.
            // The handset is supposed to respond with the same ID type as in the request.
            LOG(NOTICE) << "Paging Reponse with non-valid TMSI";
            // Cause 0x60 "Invalid mandatory information"
            DCCH->send(L3ChannelRelease(0x60));
            return;
        }
    }

    // Delete the Mobile ID from the paging list to free up CCCH bandwidth.
    // ... if it was not deleted by a timer already ...
    gBTS.pager().removeID(mobileID);

    // Find the transction table entry that was created when the phone was paged.
    // We have to look up by mobile ID since the paging entry may have been
    // erased before this handler was called.  That's too bad.
    // HACK -- We also flush stray transactions until we find what we
    // are looking for.
    TransactionEntry transaction;
    while (true) {
        if (!gTransactionTable.find(mobileID,transaction)) {
            LOG(WARN) << "Paging Reponse with no transaction record for " << mobileID;
            // Cause 0x41 means "call already cleared".
            DCCH->send(L3ChannelRelease(0x41));
            return;
        }
        // We are looking for a mobile-terminated transaction.
        // The transaction controller will take it from here.
        switch (transaction.service().type()) {
        case L3CMServiceType::MobileTerminatedCall:
            MTCStarter(transaction, DCCH, mobileID);
            return;
        case L3CMServiceType::TestCall:
            TestCall(transaction, DCCH);
            return;
        case L3CMServiceType::MobileTerminatedShortMessage:
            MTSMSController(transaction, DCCH);
            return;
        default:
            // Flush stray MOC entries.
            // There should not be any, but...
            LOG(WARN) << "flushing stray " << transaction.service().type() << " transaction entry";
            gTransactionTable.remove(transaction.ID());
            continue;
        }
    }
    // The transaction may or may not be cleared,
    // depending on the assignment type.
}

bool SIPInterface::checkInvite( osip_message_t * msg )
{
	LOG(DEBUG);

	// Is there even a method?
	const char *method = msg->sip_method;
	if (!method) return false;

	// Check for INVITE or MESSAGE methods.
	GSM::ChannelType requiredChannel;
	bool channelAvailable = false;
	bool shouldPage = true;
	GSM::L3CMServiceType serviceType;
	if (strcmp(method,"INVITE") == 0) {
		// INVITE is for MTC.
		// Set the required channel type to match the assignment style.
		if (gConfig.defines("GSM.VEA")) {
			// Very early assignment.
			requiredChannel = GSM::TCHFType;
			channelAvailable = gBTS.TCHAvailable();
		} else {
			// Early assignment
			requiredChannel = GSM::SDCCHType;
			channelAvailable = gBTS.SDCCHAvailable() && gBTS.TCHAvailable();
		}
		serviceType = L3CMServiceType::MobileTerminatedCall;
	}
	else if (strcmp(method,"MESSAGE") == 0) {
		// MESSAGE is for MTSMS or USSD
      if (  strcmp(gConfig.getStr("USSD.SIP.user"), msg->from->url->username)==0
         && strcmp(gConfig.getStr("USSD.SIP.domain"), msg->from->url->host)==0)
      {
         LOG(INFO) << "received MESSAGE is USSD from: "
                   << msg->from->url->username << "@" << msg->from->url->host;
         requiredChannel = GSM::SDCCHType;
			// TODO:: Understand how to behave when we need to page?
         channelAvailable = true; //gBTS.SDCCHAvailable();
         serviceType = L3CMServiceType::SupplementaryService;
      }
      else
      {
         LOG(INFO) << "received MESSAGE is SMS from: "
                   << msg->from->url->username << "@" << msg->from->url->host;
         requiredChannel = GSM::SDCCHType;
         channelAvailable = gBTS.SDCCHAvailable();
         serviceType = L3CMServiceType::MobileTerminatedShortMessage;
      }
	}
	else {
		// We must not handle this method.
		LOG(DEBUG) << "non-initiating SIP method " << method;
		return false;
	}

	// Check gBTS for channel availability.
	if (!channelAvailable) {
		// FIXME -- Send 503 "Service Unavailable" response on SIP interface.
		LOG(NOTICE) << "MTC CONGESTION, no " << requiredChannel << " availble for assignment";
		return false;
	}
	LOG(INFO) << "set up MTC paging for channel=" << requiredChannel;

	// Get call_id from invite message.
	if (!msg->call_id) {
		// FIXME -- Send appropriate error on SIP interface.
		LOG(WARN) << "Incoming INVITE/MESSAGE with no call ID";
		return false;
	}

	// Don't free call_id_num.  It points into msg->call_id.
	const char * call_id_num = osip_call_id_get_number(msg->call_id);	

	// Get request username (IMSI) from invite. 
	// Form of the name is IMSI<digits>, and it should always be 19 char.
	const char * IMSI = msg->req_uri->username;
	LOG(INFO) << msg->sip_method << " to "<< IMSI;
	// IMSIs are 14 or 15 char + "IMSI" prefix
	unsigned namelen = strlen(IMSI);
	if ((namelen>19)||(namelen<18)) {
		LOG(WARN) << "INVITE/MESSAGE with malformed username \"" << IMSI << "\"";
		return false;
	}
	// Skip first 4 char "IMSI".
	IMSI+=4;
	// Make the mobile id we need for transaction and paging entries.
	L3MobileIdentity mobile_id(IMSI);

	// Check SIP map.  Repeated entry?  Page again.
	// Skip this for USSD.
	if (  mSIPMap.map().readNoBlock(call_id_num) != NULL) {
		TransactionEntry transaction;
		if (!gTransactionTable.find(mobile_id,transaction)) {
			// FIXME -- Send "call leg non-existent" response on SIP interface.
			LOG(WARN) << "repeated INVITE/MESSAGE with no transaction record";
			// Delete the bogus FIFO.
			mSIPMap.remove(call_id_num);
			return false;
		}
		LOG(INFO) << "repeated SIP INVITE/MESSAGE, repaging for transaction " << transaction; 
		gBTS.pager().addID(mobile_id,requiredChannel,transaction);	
//.........这里部分代码省略.........

/**
	This function starts MOC on the SDCCH to the point of TCH assignment.
	@param req The CM Service Request that started all of this.
	@param LCH The logical used to initiate call setup.
*/
void Control::MOCStarter(const GSM::L3CMServiceRequest* req, GSM::LogicalChannel *LCH)
{
    assert(LCH);
    assert(req);
    LOG(INFO) << *req;

    // Determine if very early assignment already happened.
    bool veryEarly = (LCH->type()==GSM::FACCHType);

    // If we got a TMSI, find the IMSI.
    // Note that this is a copy, not a reference.
    GSM::L3MobileIdentity mobileID = req->mobileID();
    resolveIMSI(mobileID,LCH);


    // FIXME -- At this point, verify the that subscriber has access to this service.
    // If the subscriber isn't authorized, send a CM Service Reject with
    // cause code, 0x41, "requested service option not subscribed",
    // followed by a Channel Release with cause code 0x6f, "unspecified".
    // Otherwise, proceed to the next section of code.
    // For now, we are assuming that the phone won't make a call if it didn't
    // get registered.

    // Allocate a TCH for the call, if we don't have it already.
    GSM::TCHFACCHLogicalChannel *TCH = NULL;
    if (!veryEarly) {
        TCH = allocateTCH(dynamic_cast<GSM::LogicalChannel*>(LCH));
        // It's OK to just return on failure; allocateTCH cleaned up already,
        // and the SIP side and transaction record don't exist yet.
        if (TCH==NULL) return;
    }

    // Let the phone know we're going ahead with the transaction.
    LOG(INFO) << "sending CMServiceAccept";
    LCH->send(GSM::L3CMServiceAccept());

    // Get the Setup message.
    // GSM 04.08 5.2.1.2
    GSM::L3Message* msg_setup = getMessage(LCH);
    const GSM::L3Setup *setup = dynamic_cast<const GSM::L3Setup*>(msg_setup);
    if (!setup) {
        if (msg_setup) {
            LOG(WARNING) << "Unexpected message " << *msg_setup;
            delete msg_setup;
        }
        throw UnexpectedMessage();
    }
    LOG(INFO) << *setup;
    // Pull out the L3 short transaction information now.
    // See GSM 04.07 11.2.3.1.3.
    // Set the high bit, since this TI came from the MS.
    unsigned L3TI = setup->TI() | 0x08;
    if (!setup->haveCalledPartyBCDNumber()) {
        // FIXME -- This is quick-and-dirty, not following GSM 04.08 5.
        LOG(WARNING) << "MOC setup with no number";
        // Cause 0x60 "Invalid mandatory information"
        LCH->send(GSM::L3ReleaseComplete(L3TI,0x60));
        LCH->send(GSM::L3ChannelRelease());
        // The SIP side and transaction record don't exist yet.
        // So we're done.
        delete msg_setup;
        return;
    }

    LOG(DEBUG) << "SIP start engine";
    // Get the users sip_uri by pulling out the IMSI.
    //const char *IMSI = mobileID.digits();
    // Pull out Number user is trying to call and use as the sip_uri.
    const char *bcdDigits = setup->calledPartyBCDNumber().digits();

    // Create a transaction table entry so the TCH controller knows what to do later.
    // The transaction on the TCH will be a continuation of this one.
    TransactionEntry *transaction = new TransactionEntry(
        gConfig.getStr("SIP.Proxy.Speech").c_str(),
        mobileID,
        LCH,
        req->serviceType(),
        L3TI,
        setup->calledPartyBCDNumber());
    LOG(DEBUG) << "transaction: " << *transaction;
    gTransactionTable.add(transaction);

    // At this point, we have enough information start the SIP call setup.
    // We also have a SIP side and a transaction that will need to be
    // cleaned up on abort or clearing.

    // Now start a call by contacting asterisk.
    // Engine methods will return their current state.
    // The remote party will start ringing soon.
    LOG(DEBUG) << "starting SIP (INVITE) Calling "<<bcdDigits;
    unsigned basePort = allocateRTPPorts();
    transaction->MOCSendINVITE(bcdDigits,gConfig.getStr("SIP.Local.IP").c_str(),basePort,SIP::RTPGSM610);
    LOG(DEBUG) << "transaction: " << *transaction;

    // Once we can start SIP call setup, send Call Proceeding.
//.........这里部分代码省略.........

void Control::MTCController(TransactionEntry& transaction, TCHFACCHLogicalChannel* TCH)
{
	// Early Assignment Mobile Terminated Call. 
	// Transaction table in 04.08 7.3.3 figure 7.10a

	LOG(DEBUG) << "transaction: " << transaction;
	unsigned L3TI = transaction.TIValue();
	assert(transaction.TIFlag()==1);
	assert(TCH);

	// Get the alerting message.
	LOG(INFO) << "waiting for GSM Alerting and Connect";
	while (transaction.Q931State()!=TransactionEntry::Active) {
		if (updateGSMSignalling(transaction,TCH,1000)) return;
		if (transaction.Q931State()==TransactionEntry::Active) break;
		if (transaction.Q931State()==TransactionEntry::CallReceived) {
			LOG(DEBUG) << "sending SIP Ringing";
			transaction.SIP().MTCSendRinging();
		}
		// Check for SIP cancel, too.
		if (transaction.SIP().MTCWaitForACK()==SIP::Fail) {
			return abortCall(transaction,TCH,L3Cause(0x7F));
		}
	}
	gTransactionTable.update(transaction);

	LOG(INFO) << "allocating port and sending SIP OKAY";
	unsigned RTPPorts = allocateRTPPorts();
	SIPState state = transaction.SIP().MTCSendOK(RTPPorts,SIP::RTPGSM610);
	while (state!=SIP::Active) {
		LOG(DEBUG) << "wait for SIP OKAY-ACK";
		if (updateGSMSignalling(transaction,TCH)) return;
		state = transaction.SIP().MTCWaitForACK();
		LOG(DEBUG) << "SIP call state "<< state;
		switch (state) {
			case SIP::Active:
				break;
			case SIP::Fail:
				return abortCall(transaction,TCH,L3Cause(0x7F));
			case SIP::Timeout:
				state = transaction.SIP().MTCSendOK(RTPPorts,SIP::RTPGSM610);
				break;
			case SIP::Connecting:
				break;
			default:
				LOG(NOTICE) << "SIP unexpected state " << state;
				break;
		}
	}
	transaction.SIP().MTCInitRTP();
	gTransactionTable.update(transaction);

	// Send Connect Ack to make it all official.
	LOG(DEBUG) << "MTC send GSM Connect Acknowledge";
	TCH->send(L3ConnectAcknowledge(0,L3TI));

	// At this point, everything is ready to run for the call.
	// The radio link should have been cleared with the call.
	gTransactionTable.update(transaction);
	callManagementLoop(transaction,TCH);
}

void Control::MTCStarter(TransactionEntry& transaction, LogicalChannel *LCH)
{
	assert(LCH);
	LOG(INFO) << "MTC on " << LCH->type() << " transaction: "<< transaction;

	// Determine if very early assigment already happened.
	bool veryEarly = false;
	if (LCH->type()==FACCHType) veryEarly=true;

	// Allocate a TCH for the call.
	TCHFACCHLogicalChannel *TCH = NULL;
	if (!veryEarly) {
		TCH = allocateTCH(dynamic_cast<SDCCHLogicalChannel*>(LCH));
		// It's OK to just return on failure; allocateTCH cleaned up already.
		// The orphaned transaction will be cleared automatically later.
		if (TCH==NULL) return;
	}


	// Get transaction identifiers.
	// This transaction was created by the SIPInterface when it
	// processed the INVITE that started this call.
	if (!veryEarly) TCH->transactionID(transaction.ID());	
	LCH->transactionID(transaction.ID());	
	unsigned L3TI = transaction.TIValue();
	assert(transaction.TIFlag()==1);

	// GSM 04.08 5.2.2.1
	LOG(INFO) << "sending GSM Setup to call " << transaction.calling();
	LCH->send(L3Setup(0,L3TI,L3CallingPartyBCDNumber(transaction.calling())));
	transaction.T303().set();
	transaction.Q931State(TransactionEntry::CallPresent);
	gTransactionTable.update(transaction);

	// Wait for Call Confirmed message.
	LOG(DEBUG) << "wait for GSM Call Confirmed";
	while (transaction.Q931State()!=TransactionEntry::MTCConfirmed) {
		if (transaction.SIP().MTCSendTrying()==SIP::Fail) {
			LOG(NOTICE) << "call failed on SIP side";
			LCH->send(RELEASE);
			// Cause 0x03 is "no route to destination"
			return abortCall(transaction,LCH,L3Cause(0x03));
		}
		// FIXME -- What's the proper timeout here?
		// It's the SIP TRYING timeout, whatever that is.
		if (updateGSMSignalling(transaction,LCH,1000)) {
			LOG(INFO) << "Release from GSM side";
			LCH->send(RELEASE);
			return;
		}
		// Check for SIP cancel, too.
		if (transaction.SIP().MTCWaitForACK()==SIP::Fail) {
			LOG(NOTICE) << "call failed on SIP side";
			LCH->send(RELEASE);
			// Cause 0x10 is "normal clearing"
			return abortCall(transaction,LCH,L3Cause(0x10));
		}
	}

	// The transaction is moving to the MTCController.
	// Once this update happens, don't change the transaction object again in this function.
	gTransactionTable.update(transaction);
	LOG(DEBUG) << "transaction: " << transaction;
	if (veryEarly) {
		// For very early assignment, we need a mode change.
		static const L3ChannelMode mode(L3ChannelMode::SpeechV1);
		LCH->send(L3ChannelModeModify(LCH->channelDescription(),mode));
		L3Message* msg_ack = getMessage(LCH);
		const L3ChannelModeModifyAcknowledge *ack =
			dynamic_cast<L3ChannelModeModifyAcknowledge*>(msg_ack);
		if (!ack) {
			if (msg_ack) {
				LOG(WARN) << "Unexpected message " << *msg_ack;
				delete msg_ack;
			}
			throw UnexpectedMessage(transaction.ID());
		}
		// Cause 0x06 is "channel unacceptable"
		bool modeOK = (ack->mode()==mode);
		delete msg_ack;
		if (!modeOK) return abortCall(transaction,LCH,L3Cause(0x06));
		MTCController(transaction,dynamic_cast<TCHFACCHLogicalChannel*>(LCH));
	}
	else {
		// For late assignment, send the TCH assignment now.
		// This dispatcher on the next channel will continue the transaction.
		assignTCHF(transaction,dynamic_cast<SDCCHLogicalChannel*>(LCH),TCH);
	}
}

void Control::MTSMSController(TransactionEntry& transaction, 
						LogicalChannel *LCH)
{
	assert(LCH);

	// HACK: At this point if the message starts with "RRLP" then we don't do SMS at all,
	// but instead to an RRLP transaction over the already allocated LogicalChannel.
	const char* m = transaction.message(); // NOTE - not very nice, my way of checking.
	if ((strlen(m) > 4) && (std::string("RRLP") == std::string(m, m+4))) {
		const char *transaction_hex = transaction.message() + 4;
		BitVector rrlp_position_request(strlen(transaction_hex)*4);
		rrlp_position_request.unhex(transaction_hex);
		LOG(INFO) << "MTSMS: Sending RRLP";
		// TODO - how to get mobID here?
		L3MobileIdentity mobID = L3MobileIdentity("000000000000000");
		RRLP::PositionResult pr = GSM::RRLP::doRRLPQuery(mobID, LCH, rrlp_position_request);
		if (pr.mValid) // in this case we only want to log the results which contain lat/lon
			logMSInfo(LCH, pr, mobID);
		LOG(INFO) << "MTSMS: Closing channel after RRLP";
		LCH->send(L3ChannelRelease());
		clearTransactionHistory(transaction);
		return;
	}

	// See GSM 04.11 Arrow Diagram A5 for the transaction
	// Step 1	Network->MS	CP-DATA containing RP-DATA
	// Step 2	MS->Network	CP-ACK
	// Step 3	MS->Network	CP-DATA containing RP-ACK
	// Step 4	Network->MS	CP-ACK

	// LAPDm operation, from GSM 04.11, Annex F:
	// """
	// Case B: Mobile terminating short message transfer, no parallel call:
	// The network side, i.e. the BSS will initiate SAPI3 establishment by a
	// SABM command on the SDCCH when the first CP-Data message is received
	// from the MSC. If no hand over occurs, the link will stay up until the
	// MSC has given the last CP-ack and invokes the clearing procedure. 
	// """

	LOG(INFO) << "MTSMS: transaction: "<< transaction;
	LCH->transactionID(transaction.ID());	
	SIPEngine& engine = transaction.SIP();

	// Update transaction state.
	transaction.Q931State(TransactionEntry::SMSDelivering);
	gTransactionTable.update(transaction);

	try {
		bool success = deliverSMSToMS(transaction.calling().digits(),transaction.message(),random()%7,LCH);

		// Close the Dm channel.
		LOG(INFO) << "MTSMS: closing";
		LCH->send(L3ChannelRelease());

		// Ack in SIP domain and update transaction state.
		if (success) {
			engine.MTSMSSendOK();
			clearTransactionHistory(transaction);
		}
	}
	catch (UnexpectedMessage) {
		// TODO -- MUST SEND PERMANENT ERROR HERE!!!!!!!!!
		engine.MTSMSSendOK();
		LCH->send(L3ChannelRelease());
		clearTransactionHistory(transaction);
	}
	catch (UnsupportedMessage) {
		// TODO -- MUST SEND PERMANENT ERROR HERE!!!!!!!!!
		engine.MTSMSSendOK();
		LCH->send(L3ChannelRelease());
		clearTransactionHistory(transaction);
	}
}

bool SIPInterface::checkInvite( osip_message_t * msg)
{
	LOG(DEBUG);

	// This code dispatches new transactions coming from the network-side SIP interface.
	// All transactions originating here are going to be mobile-terminated.
	// Yes, this method is too long and needs to be broken up into smaller steps.

	// Is there even a method?
	const char *method = msg->sip_method;
	if (!method) return false;

	// Check for INVITE or MESSAGE methods.
	// Check channel availability now, too.
	GSM::ChannelType requiredChannel;
	bool channelAvailable = false;
	GSM::L3CMServiceType serviceType;
	// pretty sure strings are garbage collected
	string proxy = get_return_address(msg);
	if (strcmp(method,"INVITE") == 0) {
		// INVITE is for MTC.
		// Set the required channel type to match the assignment style.
		if (gConfig.defines("Control.VEA")) {
			// Very early assignment.
			requiredChannel = GSM::TCHFType;
			channelAvailable = gBTS.TCHAvailable();
		} else {
			// Early assignment
			requiredChannel = GSM::SDCCHType;
			channelAvailable = gBTS.SDCCHAvailable() && gBTS.TCHAvailable();
		}
		serviceType = L3CMServiceType::MobileTerminatedCall;
	}
	else if (strcmp(method,"MESSAGE") == 0) {
		// MESSAGE is for MTSMS.
		requiredChannel = GSM::SDCCHType;
		channelAvailable = gBTS.SDCCHAvailable();
		serviceType = L3CMServiceType::MobileTerminatedShortMessage;
	}
	else {
		// Not a method handled here.
		LOG(DEBUG) << "non-initiating SIP method " << method;
		return false;
	}

	// Get request username (IMSI) from invite. 
	const char* IMSI = extractIMSI(msg);
	if (!IMSI) {
		// FIXME -- Send appropriate error (404) on SIP interface.
		LOG(WARNING) << "Incoming INVITE/MESSAGE with no IMSI";
		return false;
	}
	L3MobileIdentity mobileID(IMSI);

	// Get the SIP call ID.
	const char * callIDNum = extractCallID(msg);	
	if (!callIDNum) {
		// FIXME -- Send appropriate error on SIP interface.
		LOG(WARNING) << "Incoming INVITE/MESSAGE with no call ID";
		return false;
	}


	// Find any active transaction for this IMSI with an assigned TCH or SDCCH.
	GSM::LogicalChannel *chan = gTransactionTable.findChannel(mobileID);
	if (chan) {
		// If the type is TCH and the service is SMS, get the SACCH.
		// Otherwise, for now, just say chan=NULL.
		if (serviceType==L3CMServiceType::MobileTerminatedShortMessage && chan->type()==FACCHType) {
			chan = chan->SACCH();
		} else {
			// FIXME -- This will change to support multiple transactions.
			chan = NULL;
		}
	}

	// Check SIP map.  Repeated entry?  Page again.
	if (mSIPMap.map().readNoBlock(callIDNum) != NULL) { 
		TransactionEntry* transaction= gTransactionTable.find(mobileID,callIDNum);
		// There's a FIFO but no trasnaction record?
		if (!transaction) {
			LOG(WARNING) << "repeated INVITE/MESSAGE with no transaction record";
			// Delete the bogus FIFO.
			mSIPMap.remove(callIDNum);
			return false;
		}
		// There is transaction already.  Send trying, if appropriate.
		if (serviceType!=L3CMServiceType::MobileTerminatedShortMessage) transaction->MTCSendTrying();
		// And if no channel is established yet, page again.
		if (!chan) {
			LOG(INFO) << "repeated SIP INVITE/MESSAGE, repaging for transaction " << *transaction; 
			gBTS.pager().addID(mobileID,requiredChannel,*transaction);
		}
		return false;
	}

	// So we will need a new channel.
	// Check gBTS for channel availability.
	if (!chan && !channelAvailable) {
		// FIXME -- Send 503 "Service Unavailable" response on SIP interface.
//.........这里部分代码省略.........

/**
	Process a message received from the phone during a call.
	This function processes all deviations from the "call connected" state.
	For now, we handle call clearing and politely reject everything else.
	@param transaction The transaction record for this call.
	@param LCH The logical channel for the transaction.
	@param message A pointer to the receiver message.
	@return true If the call has been cleared and the channel released.
*/
bool callManagementDispatchGSM(TransactionEntry& transaction, LogicalChannel* LCH, const L3Message *message)
{
	LOG(DEBUG) << "from " << transaction.subscriber() << " message " << *message;

	// FIXME -- This dispatch section should be something more efficient with PD and MTI swtiches.

	// Actually check state before taking action.
	//if (transaction.SIP().state()==SIP::Cleared) return true;
	//if (transaction.Q931State()==TransactionEntry::NullState) return true;

	// Call connection steps.

	// Connect Acknowledge
	if (dynamic_cast<const L3ConnectAcknowledge*>(message)) {
		LOG(INFO) << "GSM Connect Acknowledge " << transaction.subscriber();
		transaction.resetTimers();
		transaction.Q931State(TransactionEntry::Active);
		gTransactionTable.update(transaction);
		return false;
	}

	// Connect
	// GSM 04.08 5.2.2.5 and 5.2.2.6
	if (dynamic_cast<const L3Connect*>(message)) {
		LOG(INFO) << "GSM Connect " << transaction.subscriber();
		transaction.resetTimers();
		transaction.Q931State(TransactionEntry::Active);
		gTransactionTable.update(transaction);
		return false;
	}

	// Call Confirmed
	// GSM 04.08 5.2.2.3.2
	// "Call Confirmed" is the GSM MTC counterpart to "Call Proceeding"
	if (dynamic_cast<const L3CallConfirmed*>(message)) {
		LOG(INFO) << "GSM Call Confirmed " << transaction.subscriber();
		transaction.T303().reset();
		transaction.T310().set();
		transaction.Q931State(TransactionEntry::MTCConfirmed);
		gTransactionTable.update(transaction);
		return false;
	}

	// Alerting
	// GSM 04.08 5.2.2.3.2
	if (dynamic_cast<const L3Alerting*>(message)) {
		LOG(INFO) << "GSM Alerting " << transaction.subscriber();
		transaction.T310().reset();
		transaction.T301().set();
		transaction.Q931State(TransactionEntry::CallReceived);
		gTransactionTable.update(transaction);
		return false;
	}

	// Call clearing steps.
	// Good diagrams in GSM 04.08 7.3.4

	// FIXME -- We should be checking TI values against the transaction object.

	// Disconnect (1st step of MOD)
	// GSM 04.08 5.4.3.2
	if (dynamic_cast<const L3Disconnect*>(message)) {
		LOG(INFO) << "GSM Disconnect " << transaction.subscriber();
		transaction.resetTimers();
		LCH->send(L3Release(1-transaction.TIFlag(),transaction.TIValue()));
		transaction.T308().set();
		transaction.Q931State(TransactionEntry::ReleaseRequest);
		transaction.SIP().MODSendBYE();
		gTransactionTable.update(transaction);
		return false;
	}

	// Release (2nd step of MTD)
	if (dynamic_cast<const L3Release*>(message)) {
		LOG(INFO) << "GSM Release " << transaction.subscriber();
		transaction.resetTimers();
		LCH->send(L3ReleaseComplete(1-transaction.TIFlag(),transaction.TIValue()));
		LCH->send(L3ChannelRelease());
		transaction.Q931State(TransactionEntry::NullState);
		transaction.SIP().MTDSendOK();
		gTransactionTable.update(transaction);
		return true;
	}

	// Release