void L2LAPDm::receiveSFrameRR(const L2Frame& frame)
{
// Caller should hold mLock.
OBJLOG(INFO) << "state=" << mState << " " << frame;
// GSM 04.06 3.8.5.
// Q.921 3.6.6.
// vISDN datalink.c:lapd_handle_sframe_rr
// Again, since LAPDm allows only one outstanding frame
// (k=1), this is a lot simpler than in LAPD.
switch (mState) {
case ContentionResolution:
mState = LinkEstablished;
// continue to next case...
case LinkEstablished:
// "inquiry response procedure"
// Never actually seen that happen in GSM...
if ((frame.CR()!=mC) && (frame.PF())) {
sendSFrameRR(true);
}
processAck(frame.NR());
break;
default:
// ignore
return;
}
}
void L2LAPDm::receiveUFrameDISC(const L2Frame& frame)
{
// Caller should hold mLock.
OBJLOG(INFO) << "state=" << mState << " " << frame;
mEstablishmentInProgress = false;
switch (mState) {
case AwaitingEstablish:
clearState();
break;
case LinkReleased:
// GSM 04.06 5.4.5
sendUFrameDM(frame.PF());
clearState();
break;
case ContentionResolution:
case LinkEstablished:
// Shut down the link and ack with UA.
// GSM 04.06 5.4.4.2.
sendUFrameUA(frame.PF());
clearState();
break;
case AwaitingRelease:
// We can arrive here if both ends sent DISC at the same time.
// GSM 04.06 5.4.6.1.
sendUFrameUA(frame.PF());
break;
default:
unexpectedMessage();
return;
}
}
void L2LAPDm::writeL1Ack(const L2Frame& frame)
{
// Caller should hold mLock.
// GSM 04.06 5.4.4.2
OBJLOG(DEEPDEBUG) <<"L2LAPDm::writeL1Ack " << frame;
frame.copyTo(mSentFrame);
mSentFrame.primitive(frame.primitive());
writeL1(frame);
mT200.set();
}
void SACCHLogicalChannel::writeToL1(const L2Frame& frame)
{
// The SAP may or may not be present, depending on the channel type.
OBJLOG(DEBUG) << frame;
switch (frame.primitive()) {
case L2_DATA:
mL1->writeHighSide(frame);
break;
default:
OBJLOG(ERR) << "unhandled primitive " << frame.primitive() << " in L2->L1";
devassert(0);
}
}
void L2LAPDm::sendUFrameUA(const L2Frame& frame)
{
// Send UA frame with a echoed payload.
// This is used in the contention resolution procedure.
// GSM 04.06 5.4.1.4.
// The caller need not hold mLock.
OBJLOG(INFO) << "state=" << mState << " " << frame;
L2Address address(mR,mSAPI);
L2Control control(L2Control::UFormat,frame.PF(),0x0C);
L2Length length(frame.L());
L2Header header(address,control,length);
writeL1NoAck(L2Frame(header,frame.L3Part()));
}
void L2LAPDm::receiveUFrameUI(const L2Frame& frame)
{
// The zero-length frame is the idle frame.
if (frame.L()==0) return;
OBJLOG(INFO) << "state=" << mState << " " << frame;
mL3Out.write(new L3Frame(frame,UNIT_DATA));
}
void XCCHL1Encoder::sendFrame(const L2Frame& frame)
{
OBJLOG(DEBUG) << "XCCHL1Encoder " << frame;
// Make sure there's something down there to take the busts.
if (mDownstream==NULL) {
LOG(WARNING) << "XCCHL1Encoder with no downstream";
return;
}
// This comes from GSM 05.03 4.1
// Copy the L2 frame into u[] for processing.
// GSM 05.03 4.1.1.
//assert(mD.size()==headerOffset()+frame.size());
frame.copyToSegment(mU,headerOffset());
// Send to GSMTAP (must send mU = real bits !)
gWriteGSMTAP(ARFCN(),TN(),mNextWriteTime.FN(),
typeAndOffset(),mMapping.repeatLength()>51,false,mU);
// Encode data into bursts
OBJLOG(DEBUG) << "XCCHL1Encoder d[]=" << mD;
mD.LSB8MSB();
OBJLOG(DEBUG) << "XCCHL1Encoder d[]=" << mD;
encode(); // Encode u[] to c[], GSM 05.03 4.1.2 and 4.1.3.
interleave(); // Interleave c[] to i[][], GSM 05.03 4.1.4.
transmit(); // Send the bursts to the radio, GSM 05.03 4.1.5.
}
void L2LAPDm::receiveUFrameUA(const L2Frame& frame)
{
// Caller should hold mLock.
// GSM 04.06 3.8.8
// vISDN datalink.c:lapd_socket_handle_uframe_ua
OBJLOG(INFO) << "state=" << mState << " " << frame;
if (!frame.PF()) {
unexpectedMessage();
return;
}
switch (mState) {
case AwaitingEstablish:
// We sent SABM and the peer responded.
clearCounters();
mState = LinkEstablished;
mAckSignal.signal();
mL3Out.write(new L3Frame(ESTABLISH));
break;
case AwaitingRelease:
// We sent DISC and the peer responded.
clearState();
break;
default:
unexpectedMessage();
return;
}
}
bool L2LAPDm::stuckChannel(const L2Frame& frame)
{
// Check for excessive idling.
if (frame.DCCHIdle()) mIdleCount++;
else mIdleCount=0;
return mIdleCount > maxIdle();
}
void SDCCHL1Encoder::sendFrame(const L2Frame& frame)
{
OBJLOG(DEEPDEBUG) << "SDCCHL1Encoder " << frame;
// Make sure there's something down there to take the busts.
LOG(INFO) <<"SDCCHL1Encoder SENDFRAME";
if (mDownstream==NULL) {
LOG(WARN) << "XCCHL1Encoder with no downstream";
return;
}
// This comes from GSM 05.03 4.1
// Copy the L2 frame into u[] for processing.
// GSM 05.03 4.1.1.
//assert(mD.size()==headerOffset()+frame.size());
frame.copyToSegment(mU,headerOffset());
OBJLOG(DEEPDEBUG) << "XCCHL1Encoder d[]=" << mD;
mD.LSB8MSB();
OBJLOG(DEEPDEBUG) << "XCCHL1Encoder d[]=" << mD;
encode(); // Encode u[] to c[], GSM 05.03 4.1.2 and 4.1.3.
LOG(INFO) << "SDCCHL1ENCODER ENCODED";
interleave(); // Interleave c[] to i[][], GSM 05.03 4.1.4.
LOG(INFO) << "SDCCHL1ENCODER INTERLEAVED";
encrypt(); // Encrypt i[][] to e[].
LOG(INFO) << "SDCCHL1ENCODER ENCRYPTED";
transmit(); // Send the bursts to the radio, GSM 05.03 4.1.5.
LOG(INFO) << "SDCCHL1ENCODER TRANSMITTED";
// FIXME: is this FN OK, or do we need to back it up by 4?
gWriteGSMTAP(ARFCN(),mTN,mPrevWriteTime.FN(),frame);
}
void LoopbackSAPMux::writeHighSide(const L2Frame& frame)
{
OBJLOG(DEBUG) << "Loopback " << frame;
// Substitute primitive
L2Frame newFrame(frame);
unsigned SAPI = frame.SAPI();
switch (frame.primitive()) {
case ERROR: SAPI=0; break;
case RELEASE: return;
default: break;
}
// Because this is a test fixture, as assert here.
// If this were not a text fixture, we would print a warning
// and ignore the frame.
assert(mUpstream[SAPI]);
ScopedLock lock(mLock);
mUpstream[SAPI]->writeLowSide(newFrame);
}
void SAPMux::writeLowSide(const L2Frame& frame)
{
OBJLOG(DEBUG) << frame.SAPI() << " " << frame;
unsigned SAPI = frame.SAPI();
bool data = frame.primitive()==DATA;
if (data && (!mUpstream[SAPI])) {
LOG(WARNING) << "received DATA for unsupported SAP " << SAPI;
return;
}
if (data) {
mUpstream[SAPI]->writeLowSide(frame);
} else {
// If this is a non-data primitive, copy it out to every SAP.
for (int i=0; i<4; i++) {
if (mUpstream[i]) mUpstream[i]->writeLowSide(frame);
}
}
}
void L2LAPDm::receiveSFrame(const L2Frame& frame)
{
// Caller should hold mLock.
// See GSM 04.06 5.4.1.4.
mEstablishmentInProgress = false;
switch (frame.SFrameType()) {
case L2Control::RRFrame: receiveSFrameRR(frame); break;
case L2Control::REJFrame: receiveSFrameREJ(frame); break;
default: unexpectedMessage(); return;
}
}
void L2LAPDm::receiveIFrame(const L2Frame& frame)
{
// Caller should hold mLock.
// See GSM 04.06 5.4.1.4.
mEstablishmentInProgress = false;
OBJLOG(INFO) << "state=" << mState << " NS=" << frame.NS() << " NR=" << frame.NR() << " " << frame;
// vISDN datalink.c:lapd_handle_iframe
// GSM 04.06 5.5.2, 5.7.1
// Q.921 5.6.2, 5.8.1
switch (mState) {
case ContentionResolution:
mState=LinkEstablished;
// continue to next case...
case LinkEstablished:
processAck(frame.NR());
if (frame.NS()==mVR) {
mVR = (mVR+1)%8;
bufferIFrameData(frame);
sendSFrameRR(frame.PF());
} else {
// GSM 04.06 5.7.1.
// Q.921 5.8.1.
sendSFrameREJ(frame.PF());
}
case LinkReleased:
// GSM 04.06 5.4.5
break;
default:
// ignore
break;
}
}
void L2LAPDm::bufferIFrameData(const L2Frame& frame)
{
// Concatenate I-frames to form the L3 frame.
/*
GSM 04.06 5.5.2 states:
When a data link layer entity is not in an own receiver busy condition
and receives a valid I frame whose send sequence number is equal to the
current receive state variable V(R), the data link layer entity shall:
- if the M bit is set to "0", concatenate it with previously
received frames with the M bit set to "1", if any, and pass the complete
layer 3 message unit to the layer 3 entity using the primitive
DL-DATA-INDICATION;
- if the M bit is set to "1", store the information field of the frame and
concatenate it with previously received frames with the M bit set to "1",
if any (Note: no information is passed to the layer 3 entity);
*/
OBJLOG(DEBUG) << frame;
if (!frame.M()) {
// The last or only frame.
if (mRecvBuffer.size()==0) {
// The only frame -- just send it up.
OBJLOG(DEBUG) << "single frame message";
mL3Out.write(new L3Frame(frame));
return;
}
// The last of several -- concat and send it up.
OBJLOG(DEBUG) << "last frame of message";
mL3Out.write(new L3Frame(mRecvBuffer,frame.L3Part()));
mRecvBuffer.clear();
return;
}
// One segment of many -- concat.
// This is inefficient but simple.
mRecvBuffer = L3Frame(mRecvBuffer,frame.L3Part());
OBJLOG(DEBUG) <<"buffering recvBuffer=" << mRecvBuffer;
}
void XCCHL1Encoder::writeHighSide(const L2Frame& frame)
{
switch (frame.primitive()) {
case DATA:
// Encode and send data.
if (!active()) { LOG(INFO) << "XCCHL1Encoder::writeHighSide sending on non-active channel"; }
resync();
sendFrame(frame);
break;
case ESTABLISH:
// Open both sides of the link.
// The phone is waiting to see the idle pattern.
open();
if (sibling()) sibling()->open();
return;
case RELEASE:
// Normally, we get here after a DISC-DM handshake in L2.
// Close both sides of the link, knowing that the phone will do the same.
close();
if (sibling()) sibling()->close();
break;
case HARDRELEASE:
// This means that a higher layer released the link,
// with certainty that is has been cleared of activity.
close();
if (sibling()) sibling()->close(true);
break;
case ERROR:
// If we got here, it means the link failed in L2 after several ack timeouts.
// Close the tx side and just let the receiver L1 time out on its own.
// Otherwise, we risk recycling the channel while the phone's still active.
close();
break;
default:
LOG(ERR) << "unhandled primitive " << frame.primitive() << " in L2->L1";
assert(0);
}
}
void L2LAPDm::receiveUFrame(const L2Frame& frame)
{
// Also see vISDN datalink.c:lapd_socket_handle_uframe
OBJLOG(DEBUG) << frame;
switch (frame.UFrameType()) {
case L2Control::SABMFrame: receiveUFrameSABM(frame); break;
case L2Control::DMFrame: receiveUFrameDM(frame); break;
case L2Control::UIFrame: receiveUFrameUI(frame); break;
case L2Control::DISCFrame: receiveUFrameDISC(frame); break;
case L2Control::UAFrame: receiveUFrameUA(frame); break;
default:
OBJLOG(NOTICE) << " could not parse U-Bits " << frame;
unexpectedMessage();
return;
}
}
void L2LAPDm::receiveUFrameDM(const L2Frame& frame)
{
// Caller should hold mLock.
OBJLOG(INFO) << "state=" << mState << " " << frame;
// GSM 04.06 5.4.5
if (mState==LinkReleased) return;
// GSM 04.06 5.4.6.3
if (!frame.PF()) return;
// Because we do not support multiple TEIs in LAPDm,
// and because we should never get DM in response to SABM,
// this procedure is much simpler that in vISDN LAPD.
// Unlike LAPD, there's also no reason for LAPDm to not be
// able to establish ABM, so if we get this message
// we know the channel is screwed up.
clearState();
}
void L2LogicalChannel::writeLowSide(const L2Frame& frame)
{
// If this is the first good frame of a new transaction,
// stop T3101 and tell L2 we're alive down here.
if (mT3101.active()) {
mT3101.reset();
// Inform L3 that we are alive down here.
// This does not block; goes to a InterthreadQueue L2LAPdm::mL1In
sapWriteFromL1(L2Frame(PH_CONNECT));
}
switch (frame.primitive()) {
case HANDOVER_ACCESS: // Only send this on SAPI 0.
writeToL3(new L3Frame(SAPI0,HANDOVER_ACCESS));
break;
default:
sapWriteFromL1(frame);
break;
}
}
void L2LAPDm::receiveUFrameSABM(const L2Frame& frame)
{
// Caller should hold mLock.
// Process the incoming SABM command.
// GSM 04.06 3.8.2, 5.4.1
// Q.921 5.5.1.2.
// Also borrows from vISDN datalink.c:lapd_socket_handle_uframe_sabm.
OBJLOG(INFO) << "state=" << mState << " " << frame;
// Ignore frame if P!=1.
// See GSM 04.06 5.4.1.2.
if (!frame.PF()) return;
// Dispatch according to current state.
// BTW, LAPDm can always enter multiframe mode when requested,
// so that's another big simplification over ISDN/LAPD.
switch (mState) {
case LinkReleased:
// GSM 04.06 5.4.5, 5.4.1.2, 5.4.1.4
clearCounters();
mEstablishmentInProgress = true;
// Tell L3 what happened.
mL3Out.write(new L3Frame(ESTABLISH));
if (frame.L()) {
// Presence of an L3 payload indicates contention resolution.
// GSM 04.06 5.4.1.4.
mState=ContentionResolution;
mContentionCheck = frame.sum();
mL3Out.write(new L3Frame(frame.L3Part(),DATA));
// Echo back payload.
sendUFrameUA(frame);
} else {
mState=LinkEstablished;
sendUFrameUA(frame.PF());
}
break;
case ContentionResolution:
// GSM 04.06 5.4.1.4
// This guards against the remote possibility that two handsets
// are sending on the same channel at the same time.
// vISDN's LAPD doesn't need/do this since peers are hard-wired
if (frame.sum()!=mContentionCheck) break;
mState=LinkEstablished;
sendUFrameUA(frame);
break;
case AwaitingEstablish:
// Huh? This would mean both sides sent SABM at the same time/
// That should not happen in GSM.
sendUFrameUA(frame.PF());
OBJLOG(WARN) << "simulatenous SABM attempts";
break;
case AwaitingRelease:
// If we are awaiting release, we will not enter ABM.
// So we send DM to indicate that.
sendUFrameDM(frame.PF());
break;
case LinkEstablished:
// Latency in contention resolution, GSM 04.06 5.4.2.1.
if (mEstablishmentInProgress) {
if (frame.L()) sendUFrameUA(frame);
else sendUFrameUA(frame.PF());
break;
}
if (frame.L()) {
abnormalRelease();
break;
}
// Re-establishment procedure, GSM 04.06 5.6.3.
// This basically resets the ack engine.
// We should not actually see this, as of rev 2.4.
OBJLOG(WARN) << "reestablishment not really supported";
sendUFrameUA(frame.PF());
clearCounters();
break;
default:
unexpectedMessage();
return;
}
}
