From 094b0f01ab668b573de112dea7a772299d2c8b34 Mon Sep 17 00:00:00 2001
From: Nonoo <nonoo@nonoo.hu>
Date: Sun, 25 Oct 2020 17:54:48 +0100
Subject: [PATCH] Send retransmit requests for missing audio frames

---
 audiostream.go | 54 +++++++++++++++++++++++++++++++++++++++++++-------
 seqbuf.go      | 24 +++++++++++-----------
 2 files changed, 59 insertions(+), 19 deletions(-)

diff --git a/audiostream.go b/audiostream.go
index f3dccc9..9176801 100644
--- a/audiostream.go
+++ b/audiostream.go
@@ -23,6 +23,8 @@ type audioStream struct {
 	timeoutTimer         *time.Timer
 	receivedAudio        bool
 	lastReceivedAudioSeq uint16
+
+	lastSeqBufFrontRxSeq uint16
 	rxSeqBuf             seqBuf
 	rxSeqBufEntryChan    chan seqBufEntry
 
@@ -113,30 +115,68 @@ func (s *audioStream) handleRxSeqBufEntry(e seqBufEntry) {
 	s.audio.play <- e.data
 }
 
-func (s *audioStream) handleAudioPacket(r []byte) {
+func (s *audioStream) requestRetransmitIfNeeded(gotSeq uint16) error {
+	prevExpectedSeq := gotSeq - 1
+	if s.lastSeqBufFrontRxSeq != prevExpectedSeq {
+		var missingPkts int
+		var sr seqNumRange
+		if prevExpectedSeq > s.lastSeqBufFrontRxSeq {
+			sr[0] = s.lastSeqBufFrontRxSeq
+			sr[1] = prevExpectedSeq
+			missingPkts = int(prevExpectedSeq) - int(s.lastSeqBufFrontRxSeq)
+		} else {
+			sr[0] = prevExpectedSeq
+			sr[1] = s.lastSeqBufFrontRxSeq
+			missingPkts = int(prevExpectedSeq) + 65536 - int(s.lastSeqBufFrontRxSeq)
+		}
+		if missingPkts == 1 {
+			log.Debug("request audio pkt #", sr[1], " retransmit")
+			if err := s.sendRetransmitRequest(sr[1]); err != nil {
+				return err
+			}
+		} else if missingPkts < 50 {
+			log.Debug("request audio pkt #", sr[0], "-#", sr[1], " retransmit")
+			if err := s.sendRetransmitRequestForRanges([]seqNumRange{sr}); err != nil {
+				return err
+			}
+		}
+	}
+	s.lastSeqBufFrontRxSeq = gotSeq
+	return nil
+}
+
+func (s *audioStream) handleAudioPacket(r []byte) error {
 	if s.timeoutTimer != nil {
 		s.timeoutTimer.Stop()
 		s.timeoutTimer.Reset(audioTimeoutDuration)
 	}
 
 	gotSeq := binary.LittleEndian.Uint16(r[6:8])
-	err := s.rxSeqBuf.add(seqNum(gotSeq), r[24:])
-	if err != nil {
-		log.Error(err)
+	addedToFront, _ := s.rxSeqBuf.add(seqNum(gotSeq), r[24:])
+
+	// If the packet is not added to the front of the seqbuf, then it means that it was an answer for a
+	// retransmit request (or it was an out of order packet which we don't want start a retransmit).
+	if !addedToFront {
+		return nil
 	}
+
+	return s.requestRetransmitIfNeeded(gotSeq)
 }
 
-func (s *audioStream) handleRead(r []byte) {
+func (s *audioStream) handleRead(r []byte) error {
 	if len(r) >= 580 && (bytes.Equal(r[:6], []byte{0x6c, 0x05, 0x00, 0x00, 0x00, 0x00}) || bytes.Equal(r[:6], []byte{0x44, 0x02, 0x00, 0x00, 0x00, 0x00})) {
-		s.handleAudioPacket(r)
+		return s.handleAudioPacket(r)
 	}
+	return nil
 }
 
 func (s *audioStream) loop() {
 	for {
 		select {
 		case r := <-s.common.readChan:
-			s.handleRead(r)
+			if err := s.handleRead(r); err != nil {
+				reportError(err)
+			}
 		case <-s.timeoutTimer.C:
 			reportError(errors.New("audio stream timeout, try rebooting the radio"))
 		case e := <-s.rxSeqBufEntryChan:
diff --git a/seqbuf.go b/seqbuf.go
index 5d39b54..37b485c 100644
--- a/seqbuf.go
+++ b/seqbuf.go
@@ -73,14 +73,14 @@ func (s *seqBuf) addToBack(seq seqNum, data []byte) {
 	s.notifyWatcher()
 }
 
-func (s *seqBuf) insert(seq seqNum, data []byte, toPos int) {
+func (s *seqBuf) insert(seq seqNum, data []byte, toPos int) (addedToFront bool) {
 	if toPos == 0 {
 		s.addToFront(seq, data)
-		return
+		return true
 	}
 	if toPos >= len(s.entries) {
 		s.addToBack(seq, data)
-		return
+		return false
 	}
 	sliceBefore := s.entries[:toPos]
 	sliceAfter := s.entries[toPos:]
@@ -88,6 +88,7 @@ func (s *seqBuf) insert(seq seqNum, data []byte, toPos int) {
 	s.entries = append(sliceBefore, append([]seqBufEntry{e}, sliceAfter...)...)
 
 	s.notifyWatcher()
+	return false
 }
 
 func (s *seqBuf) getDiff(seq1, seq2 seqNum) seqNum {
@@ -130,7 +131,7 @@ func (s *seqBuf) leftOrRightCloserToSeq(seq, whichSeq seqNum) direction {
 	return left
 }
 
-func (s *seqBuf) add(seq seqNum, data []byte) error {
+func (s *seqBuf) add(seq seqNum, data []byte) (addedToFront bool, err error) {
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
 
@@ -140,22 +141,22 @@ func (s *seqBuf) add(seq seqNum, data []byte) error {
 	// }()
 
 	if seq > s.maxSeqNum {
-		return errors.New("seq out of range")
+		return false, errors.New("seq out of range")
 	}
 
 	if len(s.entries) == 0 {
 		s.addToFront(seq, data)
-		return nil
+		return true, nil
 	}
 
 	if s.entries[0].seq == seq {
-		return errors.New("dropping duplicate seq")
+		return false, errors.New("dropping duplicate seq")
 	}
 
 	// Checking the first entry.
 	if s.leftOrRightCloserToSeq(seq, s.entries[0].seq) == left {
 		s.addToFront(seq, data)
-		return nil
+		return true, nil
 	}
 
 	// Parsing through other entries if there are more than 1.
@@ -164,20 +165,19 @@ func (s *seqBuf) add(seq seqNum, data []byte) error {
 		// It can be a beginning of a new stream for example.
 		if s.entries[i].seq == seq {
 			// s.addToFront(seq, data)
-			return nil
+			return false, nil
 		}
 
 		if s.leftOrRightCloserToSeq(seq, s.entries[i].seq) == left {
 			// log.Debug("left for ", s.entries[i].seq)
-			s.insert(seq, data, i)
-			return nil
+			return s.insert(seq, data, i), nil
 		}
 		// log.Debug("right for ", s.entries[i].seq)
 	}
 
 	// No place found for the item?
 	s.addToBack(seq, data)
-	return nil
+	return false, nil
 }
 
 func (s *seqBuf) getNextDataAvailableRemainingTime() (time.Duration, error) {