snapshot of https://github.com/livekit/livekit.git @ 08c5433449c106943231037d0b892895f6e92d3b (2026-09-15)

pkg/sfu/bwe/sendsidebwe/packet_tracker.go

@@ -0,0 +1,168 @@
+// Copyright 2023 LiveKit, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sendsidebwe
+
+import (
+	"math/rand"
+	"sync"
+
+	"github.com/livekit/livekit-server/pkg/sfu/ccutils"
+	"github.com/livekit/protocol/logger"
+	"github.com/livekit/protocol/utils/mono"
+)
+
+// -------------------------------------------------------------------------------
+
+type packetTrackerParams struct {
+	Logger logger.Logger
+}
+
+type packetTracker struct {
+	params packetTrackerParams
+
+	lock sync.Mutex
+
+	sequenceNumber uint64
+
+	baseSendTime int64
+	packetInfos  [2048]packetInfo
+
+	baseRecvTime int64
+	piLastRecv   *packetInfo
+
+	probeClusterId         ccutils.ProbeClusterId
+	probeMaxSequenceNumber uint64
+}
+
+func newPacketTracker(params packetTrackerParams) *packetTracker {
+	return &packetTracker{
+		params:         params,
+		sequenceNumber: uint64(rand.Intn(1<<14)) + uint64(1<<15), // a random number in third quartile of sequence number space
+	}
+}
+
+func (p *packetTracker) RecordPacketSendAndGetSequenceNumber(
+	atMicro int64,
+	size int,
+	isRTX bool,
+	probeClusterId ccutils.ProbeClusterId,
+	isProbe bool,
+) uint16 {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	if p.baseSendTime == 0 {
+		p.baseSendTime = atMicro
+	}
+
+	pi := p.getPacketInfo(uint16(p.sequenceNumber))
+	*pi = packetInfo{
+		sequenceNumber: p.sequenceNumber,
+		sendTime:       atMicro - p.baseSendTime,
+		size:           uint16(size),
+		isRTX:          isRTX,
+		probeClusterId: probeClusterId,
+		isProbe:        isProbe,
+	}
+
+	p.sequenceNumber++
+
+	// extreme case of wrap around before receiving any feedback
+	if pi == p.piLastRecv {
+		p.piLastRecv = nil
+	}
+
+	if p.probeClusterId != ccutils.ProbeClusterIdInvalid && p.probeClusterId == pi.probeClusterId && pi.sequenceNumber > p.probeMaxSequenceNumber {
+		p.probeMaxSequenceNumber = pi.sequenceNumber
+	}
+
+	return uint16(pi.sequenceNumber)
+}
+
+func (p *packetTracker) BaseSendTimeThreshold(threshold int64) (int64, bool) {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	if p.baseSendTime == 0 {
+		return 0, false
+	}
+
+	return mono.UnixMicro() - p.baseSendTime - threshold, true
+}
+
+func (p *packetTracker) RecordPacketIndicationFromRemote(sn uint16, recvTime int64) (piRecv packetInfo, sendDelta, recvDelta int64) {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	pi := p.getPacketInfoExisting(sn)
+	if pi == nil {
+		return
+	}
+
+	if recvTime == 0 {
+		// maybe lost OR already received but reported lost in a later report
+		piRecv = *pi
+		return
+	}
+
+	if p.baseRecvTime == 0 {
+		p.baseRecvTime = recvTime
+		p.piLastRecv = pi
+	}
+
+	pi.recvTime = recvTime - p.baseRecvTime
+	piRecv = *pi
+	if p.piLastRecv != nil {
+		sendDelta, recvDelta = pi.sendTime-p.piLastRecv.sendTime, pi.recvTime-p.piLastRecv.recvTime
+	}
+	p.piLastRecv = pi
+	return
+}
+
+func (p *packetTracker) getPacketInfo(sn uint16) *packetInfo {
+	return &p.packetInfos[int(sn)%len(p.packetInfos)]
+}
+
+func (p *packetTracker) getPacketInfoExisting(sn uint16) *packetInfo {
+	pi := &p.packetInfos[int(sn)%len(p.packetInfos)]
+	if uint16(pi.sequenceNumber) == sn {
+		return pi
+	}
+
+	return nil
+}
+
+func (p *packetTracker) ProbeClusterStarting(probeClusterId ccutils.ProbeClusterId) {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	p.probeClusterId = probeClusterId
+}
+
+func (p *packetTracker) ProbeClusterDone(probeClusterId ccutils.ProbeClusterId) {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	if p.probeClusterId == probeClusterId {
+		p.probeClusterId = ccutils.ProbeClusterIdInvalid
+	}
+}
+
+func (p *packetTracker) ProbeMaxSequenceNumber() uint64 {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	return p.probeMaxSequenceNumber
+}