74 lines
1.9 KiB
Go
74 lines
1.9 KiB
Go
package congestion
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import (
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"math"
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"time"
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"github.com/metacubex/quic-go/congestion"
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)
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const (
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maxBurstPackets = 10
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)
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// Pacer implements a token bucket pacing algorithm.
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type Pacer struct {
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budgetAtLastSent congestion.ByteCount
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maxDatagramSize congestion.ByteCount
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lastSentTime time.Time
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getBandwidth func() congestion.ByteCount // in bytes/s
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}
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func NewPacer(getBandwidth func() congestion.ByteCount) *Pacer {
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p := &Pacer{
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budgetAtLastSent: maxBurstPackets * congestion.InitialPacketSizeIPv4,
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maxDatagramSize: congestion.InitialPacketSizeIPv4,
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getBandwidth: getBandwidth,
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}
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return p
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}
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func (p *Pacer) SentPacket(sendTime time.Time, size congestion.ByteCount) {
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budget := p.Budget(sendTime)
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if size > budget {
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p.budgetAtLastSent = 0
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} else {
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p.budgetAtLastSent = budget - size
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}
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p.lastSentTime = sendTime
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}
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func (p *Pacer) Budget(now time.Time) congestion.ByteCount {
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if p.lastSentTime.IsZero() {
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return p.maxBurstSize()
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}
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budget := p.budgetAtLastSent + (p.getBandwidth()*congestion.ByteCount(now.Sub(p.lastSentTime).Nanoseconds()))/1e9
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if budget < 0 { // protect against overflows
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budget = congestion.ByteCount(1<<62 - 1)
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}
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return Min(p.maxBurstSize(), budget)
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}
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func (p *Pacer) maxBurstSize() congestion.ByteCount {
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return Max(
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congestion.ByteCount((congestion.MinPacingDelay+time.Millisecond).Nanoseconds())*p.getBandwidth()/1e9,
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maxBurstPackets*p.maxDatagramSize,
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)
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}
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// TimeUntilSend returns when the next packet should be sent.
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// It returns the zero value of time.Time if a packet can be sent immediately.
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func (p *Pacer) TimeUntilSend() time.Time {
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if p.budgetAtLastSent >= p.maxDatagramSize {
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return time.Time{}
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}
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return p.lastSentTime.Add(Max(
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congestion.MinPacingDelay,
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time.Duration(math.Ceil(float64(p.maxDatagramSize-p.budgetAtLastSent)*1e9/
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float64(p.getBandwidth())))*time.Nanosecond,
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))
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}
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func (p *Pacer) SetMaxDatagramSize(s congestion.ByteCount) {
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p.maxDatagramSize = s
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}
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