Method processHandoverRequest

Peering/Peering.cpp:304–409

(pat) This is BS2 which has received a request from BS1 to transfer the MS from BS1 to BS2. Manufacture a TransactionEntry and SIPEngine from the peering message.

// (pat) This is BS2 which has received a request from BS1 to transfer the MS from BS1 to BS2.
// Manufacture a TransactionEntry and SIPEngine from the peering message.
void PeerInterface::processHandoverRequest(const struct sockaddr_in* peer, const char* message)
{
	// This is "Handover Request" in the ladder diagram; we are "BS2" accepting it.
	assert(message);

	unsigned oldTransID;	// (pat) tran on BS1 that wants to come to BS2.
	if (!sscanf(message,"REQ HANDOVER %u ", &oldTransID)) {
		LOG(ALERT) << "cannot parse peering message " << message;
		return;
	}

	// Break message into space-delimited tokens, stuff into a SimpleKeyValue and then unpack it.
	SimpleKeyValue params;
	params.addItems(message);
	const char* IMSI = params.get("IMSI");
	GSM::L3MobileIdentity mobileID = GSM::L3MobileIdentity(IMSI);

	// find existing transaction record if this is a duplicate REQ HANDOVER
	Control::TranEntry* transaction = gNewTransactionTable.ttFindHandoverOther(mobileID, oldTransID);

	// and the channel that goes with it
	GSM::L2LogicalChannel* chan = NULL;
	unsigned horef;

	// if this is the first REQ HANDOVER
	if (!transaction) {
		WATCH(Utils::timestr() << " Peering recv:"<<message);

		LOG(INFO) << "initial REQ HANDOVER for " << mobileID << " " << oldTransID;

		// Get a channel allocation.
		// For now, we are assuming a full-rate channel.
		// And check gBTS.hold()
		time_t start = time(NULL);
		if (!gBTS.hold()) { chan = gBTS.getTCH(); }	// (pat) Starts T3101.  Better finish before it expires.
		LOG(DEBUG) << "getTCH took " << (time(NULL) - start) << " seconds";

		// FIXME -- Somehow, getting from getTCH above to the test below can take several seconds.
		// FIXME -- #797.

		// If getTCH took so long that there's too little time left in T3101, ignore this REQ and get the next one.
		if (chan && chan->SACCH()->debugGetL1()->decoder()->debug3101remaining() < 1000) {
			LOG(NOTICE) << "handover TCH allocation took too long; risk of T3101 timeout; trying again";
			chan->l2sendp(HARDRELEASE);	// (pat) added 9-6-2013
			return;
		}

		// If there's no channel available, send failure.
		if (!chan) {
			LOG(CRIT) << "congestion, incoming handover request denied";
			char rsp[50];
			// RR Cause 101 "cell allocation not available"
			// GSM 04.08 10.5.2.31
			sprintf(rsp,"RSP HANDOVER %u 101", oldTransID);
			sendMessage(peer,rsp);
			return;
		}