121 lines
3.7 KiB
Go
121 lines
3.7 KiB
Go
package flowcontrol
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import (
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"sync"
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"time"
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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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)
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type baseFlowController struct {
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// for sending data
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bytesSent protocol.ByteCount
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sendWindow protocol.ByteCount
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lastBlockedAt protocol.ByteCount
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// for receiving data
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//nolint:structcheck // The mutex is used both by the stream and the connection flow controller
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mutex sync.Mutex
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bytesRead protocol.ByteCount
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highestReceived protocol.ByteCount
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receiveWindow protocol.ByteCount
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receiveWindowSize protocol.ByteCount
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maxReceiveWindowSize protocol.ByteCount
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epochStartTime time.Time
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epochStartOffset protocol.ByteCount
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rttStats *utils.RTTStats
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logger utils.Logger
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}
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// IsNewlyBlocked says if it is newly blocked by flow control.
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// For every offset, it only returns true once.
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// If it is blocked, the offset is returned.
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func (c *baseFlowController) IsNewlyBlocked() (bool, protocol.ByteCount) {
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if c.sendWindowSize() != 0 || c.sendWindow == c.lastBlockedAt {
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return false, 0
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}
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c.lastBlockedAt = c.sendWindow
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return true, c.sendWindow
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}
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func (c *baseFlowController) AddBytesSent(n protocol.ByteCount) {
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c.bytesSent += n
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}
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// UpdateSendWindow is be called after receiving a MAX_{STREAM_}DATA frame.
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func (c *baseFlowController) UpdateSendWindow(offset protocol.ByteCount) {
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if offset > c.sendWindow {
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c.sendWindow = offset
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}
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}
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func (c *baseFlowController) sendWindowSize() protocol.ByteCount {
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// this only happens during connection establishment, when data is sent before we receive the peer's transport parameters
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if c.bytesSent > c.sendWindow {
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return 0
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}
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return c.sendWindow - c.bytesSent
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}
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// needs to be called with locked mutex
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func (c *baseFlowController) addBytesRead(n protocol.ByteCount) {
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// pretend we sent a WindowUpdate when reading the first byte
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// this way auto-tuning of the window size already works for the first WindowUpdate
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if c.bytesRead == 0 {
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c.startNewAutoTuningEpoch(time.Now())
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}
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c.bytesRead += n
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}
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func (c *baseFlowController) hasWindowUpdate() bool {
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bytesRemaining := c.receiveWindow - c.bytesRead
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// update the window when more than the threshold was consumed
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return bytesRemaining <= protocol.ByteCount(float64(c.receiveWindowSize)*(1-protocol.WindowUpdateThreshold))
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}
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// getWindowUpdate updates the receive window, if necessary
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// it returns the new offset
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func (c *baseFlowController) getWindowUpdate() protocol.ByteCount {
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if !c.hasWindowUpdate() {
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return 0
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}
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c.maybeAdjustWindowSize()
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c.receiveWindow = c.bytesRead + c.receiveWindowSize
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return c.receiveWindow
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}
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// maybeAdjustWindowSize increases the receiveWindowSize if we're sending updates too often.
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// For details about auto-tuning, see https://docs.google.com/document/d/1SExkMmGiz8VYzV3s9E35JQlJ73vhzCekKkDi85F1qCE/edit?usp=sharing.
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func (c *baseFlowController) maybeAdjustWindowSize() {
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bytesReadInEpoch := c.bytesRead - c.epochStartOffset
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// don't do anything if less than half the window has been consumed
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if bytesReadInEpoch <= c.receiveWindowSize/2 {
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return
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}
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rtt := c.rttStats.SmoothedRTT()
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if rtt == 0 {
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return
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}
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fraction := float64(bytesReadInEpoch) / float64(c.receiveWindowSize)
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now := time.Now()
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if now.Sub(c.epochStartTime) < time.Duration(4*fraction*float64(rtt)) {
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// window is consumed too fast, try to increase the window size
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c.receiveWindowSize = utils.MinByteCount(2*c.receiveWindowSize, c.maxReceiveWindowSize)
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}
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c.startNewAutoTuningEpoch(now)
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}
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func (c *baseFlowController) startNewAutoTuningEpoch(now time.Time) {
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c.epochStartTime = now
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c.epochStartOffset = c.bytesRead
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}
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func (c *baseFlowController) checkFlowControlViolation() bool {
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return c.highestReceived > c.receiveWindow
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}
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