85 lines
2.2 KiB
Go
85 lines
2.2 KiB
Go
package quic
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import (
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"time"
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"github.com/lucas-clemente/quic-go/internal/ackhandler"
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"github.com/lucas-clemente/quic-go/internal/protocol"
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"github.com/lucas-clemente/quic-go/internal/utils"
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"github.com/lucas-clemente/quic-go/internal/wire"
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)
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type mtuDiscoverer interface {
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ShouldSendProbe(now time.Time) bool
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NextProbeTime() time.Time
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GetPing() (ping ackhandler.Frame, datagramSize protocol.ByteCount)
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}
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const (
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// At some point, we have to stop searching for a higher MTU.
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// We're happy to send a packet that's 10 bytes smaller than the actual MTU.
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maxMTUDiff = 20
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// send a probe packet every mtuProbeDelay RTTs
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mtuProbeDelay = 5
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)
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type mtuFinder struct {
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lastProbeTime time.Time
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probeInFlight bool
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mtuIncreased func(protocol.ByteCount)
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rttStats *utils.RTTStats
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current protocol.ByteCount
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max protocol.ByteCount // the maximum value, as advertised by the peer (or our maximum size buffer)
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}
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var _ mtuDiscoverer = &mtuFinder{}
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func newMTUDiscoverer(rttStats *utils.RTTStats, start, max protocol.ByteCount, mtuIncreased func(protocol.ByteCount)) mtuDiscoverer {
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return &mtuFinder{
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current: start,
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rttStats: rttStats,
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lastProbeTime: time.Now(), // to make sure the first probe packet is not sent immediately
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mtuIncreased: mtuIncreased,
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max: max,
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}
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}
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func (f *mtuFinder) done() bool {
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return f.max-f.current <= maxMTUDiff+1
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}
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func (f *mtuFinder) ShouldSendProbe(now time.Time) bool {
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if f.probeInFlight || f.done() {
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return false
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}
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return !now.Before(f.NextProbeTime())
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}
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// NextProbeTime returns the time when the next probe packet should be sent.
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// It returns the zero value if no probe packet should be sent.
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func (f *mtuFinder) NextProbeTime() time.Time {
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if f.probeInFlight || f.done() {
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return time.Time{}
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}
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return f.lastProbeTime.Add(mtuProbeDelay * f.rttStats.SmoothedRTT())
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}
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func (f *mtuFinder) GetPing() (ackhandler.Frame, protocol.ByteCount) {
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size := (f.max + f.current) / 2
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f.lastProbeTime = time.Now()
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f.probeInFlight = true
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return ackhandler.Frame{
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Frame: &wire.PingFrame{},
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OnLost: func(wire.Frame) {
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f.probeInFlight = false
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f.max = size
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},
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OnAcked: func(wire.Frame) {
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f.probeInFlight = false
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f.current = size
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f.mtuIncreased(size)
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},
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}, size
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}
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