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congestion: fix overflow when calculating the pacing budget (#3796)

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This commit is contained in:
Marten Seemann
2023-05-01 14:32:20 +02:00
committed by GitHub
parent c0b94ee4b0
commit 94829edf35
2 changed files with 21 additions and 8 deletions
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19
internal/congestion/pacer.go
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@@ -12,16 +12,16 @@ const maxBurstSizePackets = 10
// The pacer implements a token bucket pacing algorithm.
type pacer struct {
budgetAtLastSent protocol.ByteCount
maxDatagramSize protocol.ByteCount
lastSentTime time.Time
getAdjustedBandwidth func() uint64 // in bytes/s
budgetAtLastSent protocol.ByteCount
maxDatagramSize protocol.ByteCount
lastSentTime time.Time
adjustedBandwidth func() uint64 // in bytes/s
}
func newPacer(getBandwidth func() Bandwidth) *pacer {
p := &pacer{
maxDatagramSize: initialMaxDatagramSize,
getAdjustedBandwidth: func() uint64 {
adjustedBandwidth: func() uint64 {
// Bandwidth is in bits/s. We need the value in bytes/s.
bw := uint64(getBandwidth() / BytesPerSecond)
// Use a slightly higher value than the actual measured bandwidth.
@@ -49,13 +49,16 @@ func (p *pacer) Budget(now time.Time) protocol.ByteCount {
if p.lastSentTime.IsZero() {
return p.maxBurstSize()
}
budget := p.budgetAtLastSent + (protocol.ByteCount(p.getAdjustedBandwidth())*protocol.ByteCount(now.Sub(p.lastSentTime).Nanoseconds()))/1e9
budget := p.budgetAtLastSent + (protocol.ByteCount(p.adjustedBandwidth())*protocol.ByteCount(now.Sub(p.lastSentTime).Nanoseconds()))/1e9
if budget < 0 { // protect against overflows
budget = protocol.MaxByteCount
}
return utils.Min(p.maxBurstSize(), budget)
}
func (p *pacer) maxBurstSize() protocol.ByteCount {
return utils.Max(
protocol.ByteCount(uint64((protocol.MinPacingDelay+protocol.TimerGranularity).Nanoseconds())*p.getAdjustedBandwidth())/1e9,
protocol.ByteCount(uint64((protocol.MinPacingDelay+protocol.TimerGranularity).Nanoseconds())*p.adjustedBandwidth())/1e9,
maxBurstSizePackets*p.maxDatagramSize,
)
}
@@ -68,7 +71,7 @@ func (p *pacer) TimeUntilSend() time.Time {
}
return p.lastSentTime.Add(utils.Max(
protocol.MinPacingDelay,
time.Duration(math.Ceil(float64(p.maxDatagramSize-p.budgetAtLastSent)*1e9/float64(p.getAdjustedBandwidth())))*time.Nanosecond,
time.Duration(math.Ceil(float64(p.maxDatagramSize-p.budgetAtLastSent)*1e9/float64(p.adjustedBandwidth())))*time.Nanosecond,
))
}