feat(pcap): impl realtime wait() with time offset

io/pcap.go

@@ -19,7 +19,7 @@ var _ PacketIO = (*pcapPacketIO)(nil)
 type pcapPacketIO struct {
 	pcapFile   io.ReadCloser
 	pcap       *pcapgo.Reader
-	lastTime *time.Time
+	timeOffset *time.Duration
 	ioCancel   context.CancelFunc
 	config     PcapPacketIOConfig
 
@@ -45,7 +45,7 @@ func NewPcapPacketIO(config PcapPacketIOConfig) (PacketIO, error) {
 	return &pcapPacketIO{
 		pcapFile:   pcapFile,
 		pcap:       handle,
-		lastTime: nil,
+		timeOffset: nil,
 		ioCancel:   nil,
 		config:     config,
 		dialer:     &net.Dialer{},
@@ -101,20 +101,18 @@ func (p *pcapPacketIO) Close() error {
 
 // Intentionally slow down the replay
 // In realtime mode, this is to match the timestamps in the capture
-func (p *pcapPacketIO) wait(packet gopacket.Packet) error {
+func (p *pcapPacketIO) wait(packet gopacket.Packet) {
 	if !p.config.Realtime {
-		return nil
+		return
 	}
 
-	if p.lastTime == nil {
-		p.lastTime = &packet.Metadata().Timestamp
+	if p.timeOffset == nil {
+		offset := time.Since(packet.Metadata().Timestamp)
+		p.timeOffset = &offset
 	} else {
-		t := packet.Metadata().Timestamp.Sub(*p.lastTime)
+		t := time.Until(packet.Metadata().Timestamp.Add(*p.timeOffset))
 		time.Sleep(t)
-		p.lastTime = &packet.Metadata().Timestamp
 	}
-
-	return nil
 }
 
 var _ Packet = (*pcapPacket)(nil)