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::receiveSFrameREJ(const L2Frame& frame)
{
// Caller should hold mLock.
OBJLOG(INFO) << "state=" << mState << " " << frame;
// GSM 04.06 3.8.6, 5.5.4
// Q.921 3.7.6, 5.6.4.
// vISDN datalink.c:lapd_handle_s_frame_rej.
switch (mState) {
case ContentionResolution:
mState = LinkEstablished;
// continue to next case...
case LinkEstablished:
// FIXME -- The spec says to do this but it breaks multiframe transmission.
//mVS = mVA = frame.NR();
processAck(frame.NR());
if (frame.PF()) {
if (frame.CR()!=mC) sendSFrameRR(true);
else {
unexpectedMessage();
return;
}
}
// Since k=1, there's really nothing to retransmit,
// other than what was just rejected, so kust stop sending it.
sendIdle();
break;
default:
// ignore
break;
}
// Send an idle frame to clear any repeating junk on the channel.
sendIdle();
}
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;
}
}