mirror of
https://github.com/MetaCubeX/mihomo.git
synced 2024-08-26 03:42:32 +00:00
376 lines
16 KiB
Go
376 lines
16 KiB
Go
package congestion
|
|
|
|
import (
|
|
"math"
|
|
"time"
|
|
|
|
"github.com/metacubex/quic-go/congestion"
|
|
)
|
|
|
|
var (
|
|
InfiniteBandwidth = Bandwidth(math.MaxUint64)
|
|
)
|
|
|
|
// SendTimeState is a subset of ConnectionStateOnSentPacket which is returned
|
|
// to the caller when the packet is acked or lost.
|
|
type SendTimeState struct {
|
|
// Whether other states in this object is valid.
|
|
isValid bool
|
|
// Whether the sender is app limited at the time the packet was sent.
|
|
// App limited bandwidth sample might be artificially low because the sender
|
|
// did not have enough data to send in order to saturate the link.
|
|
isAppLimited bool
|
|
// Total number of sent bytes at the time the packet was sent.
|
|
// Includes the packet itself.
|
|
totalBytesSent congestion.ByteCount
|
|
// Total number of acked bytes at the time the packet was sent.
|
|
totalBytesAcked congestion.ByteCount
|
|
// Total number of lost bytes at the time the packet was sent.
|
|
totalBytesLost congestion.ByteCount
|
|
}
|
|
|
|
// ConnectionStateOnSentPacket represents the information about a sent packet
|
|
// and the state of the connection at the moment the packet was sent,
|
|
// specifically the information about the most recently acknowledged packet at
|
|
// that moment.
|
|
type ConnectionStateOnSentPacket struct {
|
|
packetNumber congestion.PacketNumber
|
|
// Time at which the packet is sent.
|
|
sendTime time.Time
|
|
// Size of the packet.
|
|
size congestion.ByteCount
|
|
// The value of |totalBytesSentAtLastAckedPacket| at the time the
|
|
// packet was sent.
|
|
totalBytesSentAtLastAckedPacket congestion.ByteCount
|
|
// The value of |lastAckedPacketSentTime| at the time the packet was
|
|
// sent.
|
|
lastAckedPacketSentTime time.Time
|
|
// The value of |lastAckedPacketAckTime| at the time the packet was
|
|
// sent.
|
|
lastAckedPacketAckTime time.Time
|
|
// Send time states that are returned to the congestion controller when the
|
|
// packet is acked or lost.
|
|
sendTimeState SendTimeState
|
|
}
|
|
|
|
// BandwidthSample
|
|
type BandwidthSample struct {
|
|
// The bandwidth at that particular sample. Zero if no valid bandwidth sample
|
|
// is available.
|
|
bandwidth Bandwidth
|
|
// The RTT measurement at this particular sample. Zero if no RTT sample is
|
|
// available. Does not correct for delayed ack time.
|
|
rtt time.Duration
|
|
// States captured when the packet was sent.
|
|
stateAtSend SendTimeState
|
|
}
|
|
|
|
func NewBandwidthSample() *BandwidthSample {
|
|
return &BandwidthSample{
|
|
// FIXME: the default value of original code is zero.
|
|
rtt: InfiniteRTT,
|
|
}
|
|
}
|
|
|
|
// BandwidthSampler keeps track of sent and acknowledged packets and outputs a
|
|
// bandwidth sample for every packet acknowledged. The samples are taken for
|
|
// individual packets, and are not filtered; the consumer has to filter the
|
|
// bandwidth samples itself. In certain cases, the sampler will locally severely
|
|
// underestimate the bandwidth, hence a maximum filter with a size of at least
|
|
// one RTT is recommended.
|
|
//
|
|
// This class bases its samples on the slope of two curves: the number of bytes
|
|
// sent over time, and the number of bytes acknowledged as received over time.
|
|
// It produces a sample of both slopes for every packet that gets acknowledged,
|
|
// based on a slope between two points on each of the corresponding curves. Note
|
|
// that due to the packet loss, the number of bytes on each curve might get
|
|
// further and further away from each other, meaning that it is not feasible to
|
|
// compare byte values coming from different curves with each other.
|
|
//
|
|
// The obvious points for measuring slope sample are the ones corresponding to
|
|
// the packet that was just acknowledged. Let us denote them as S_1 (point at
|
|
// which the current packet was sent) and A_1 (point at which the current packet
|
|
// was acknowledged). However, taking a slope requires two points on each line,
|
|
// so estimating bandwidth requires picking a packet in the past with respect to
|
|
// which the slope is measured.
|
|
//
|
|
// For that purpose, BandwidthSampler always keeps track of the most recently
|
|
// acknowledged packet, and records it together with every outgoing packet.
|
|
// When a packet gets acknowledged (A_1), it has not only information about when
|
|
// it itself was sent (S_1), but also the information about the latest
|
|
// acknowledged packet right before it was sent (S_0 and A_0).
|
|
//
|
|
// Based on that data, send and ack rate are estimated as:
|
|
//
|
|
// send_rate = (bytes(S_1) - bytes(S_0)) / (time(S_1) - time(S_0))
|
|
// ack_rate = (bytes(A_1) - bytes(A_0)) / (time(A_1) - time(A_0))
|
|
//
|
|
// Here, the ack rate is intuitively the rate we want to treat as bandwidth.
|
|
// However, in certain cases (e.g. ack compression) the ack rate at a point may
|
|
// end up higher than the rate at which the data was originally sent, which is
|
|
// not indicative of the real bandwidth. Hence, we use the send rate as an upper
|
|
// bound, and the sample value is
|
|
//
|
|
// rate_sample = min(send_rate, ack_rate)
|
|
//
|
|
// An important edge case handled by the sampler is tracking the app-limited
|
|
// samples. There are multiple meaning of "app-limited" used interchangeably,
|
|
// hence it is important to understand and to be able to distinguish between
|
|
// them.
|
|
//
|
|
// Meaning 1: connection state. The connection is said to be app-limited when
|
|
// there is no outstanding data to send. This means that certain bandwidth
|
|
// samples in the future would not be an accurate indication of the link
|
|
// capacity, and it is important to inform consumer about that. Whenever
|
|
// connection becomes app-limited, the sampler is notified via OnAppLimited()
|
|
// method.
|
|
//
|
|
// Meaning 2: a phase in the bandwidth sampler. As soon as the bandwidth
|
|
// sampler becomes notified about the connection being app-limited, it enters
|
|
// app-limited phase. In that phase, all *sent* packets are marked as
|
|
// app-limited. Note that the connection itself does not have to be
|
|
// app-limited during the app-limited phase, and in fact it will not be
|
|
// (otherwise how would it send packets?). The boolean flag below indicates
|
|
// whether the sampler is in that phase.
|
|
//
|
|
// Meaning 3: a flag on the sent packet and on the sample. If a sent packet is
|
|
// sent during the app-limited phase, the resulting sample related to the
|
|
// packet will be marked as app-limited.
|
|
//
|
|
// With the terminology issue out of the way, let us consider the question of
|
|
// what kind of situation it addresses.
|
|
//
|
|
// Consider a scenario where we first send packets 1 to 20 at a regular
|
|
// bandwidth, and then immediately run out of data. After a few seconds, we send
|
|
// packets 21 to 60, and only receive ack for 21 between sending packets 40 and
|
|
// 41. In this case, when we sample bandwidth for packets 21 to 40, the S_0/A_0
|
|
// we use to compute the slope is going to be packet 20, a few seconds apart
|
|
// from the current packet, hence the resulting estimate would be extremely low
|
|
// and not indicative of anything. Only at packet 41 the S_0/A_0 will become 21,
|
|
// meaning that the bandwidth sample would exclude the quiescence.
|
|
//
|
|
// Based on the analysis of that scenario, we implement the following rule: once
|
|
// OnAppLimited() is called, all sent packets will produce app-limited samples
|
|
// up until an ack for a packet that was sent after OnAppLimited() was called.
|
|
// Note that while the scenario above is not the only scenario when the
|
|
// connection is app-limited, the approach works in other cases too.
|
|
type BandwidthSampler struct {
|
|
// The total number of congestion controlled bytes sent during the connection.
|
|
totalBytesSent congestion.ByteCount
|
|
// The total number of congestion controlled bytes which were acknowledged.
|
|
totalBytesAcked congestion.ByteCount
|
|
// The total number of congestion controlled bytes which were lost.
|
|
totalBytesLost congestion.ByteCount
|
|
// The value of |totalBytesSent| at the time the last acknowledged packet
|
|
// was sent. Valid only when |lastAckedPacketSentTime| is valid.
|
|
totalBytesSentAtLastAckedPacket congestion.ByteCount
|
|
// The time at which the last acknowledged packet was sent. Set to
|
|
// QuicTime::Zero() if no valid timestamp is available.
|
|
lastAckedPacketSentTime time.Time
|
|
// The time at which the most recent packet was acknowledged.
|
|
lastAckedPacketAckTime time.Time
|
|
// The most recently sent packet.
|
|
lastSendPacket congestion.PacketNumber
|
|
// Indicates whether the bandwidth sampler is currently in an app-limited
|
|
// phase.
|
|
isAppLimited bool
|
|
// The packet that will be acknowledged after this one will cause the sampler
|
|
// to exit the app-limited phase.
|
|
endOfAppLimitedPhase congestion.PacketNumber
|
|
// Record of the connection state at the point where each packet in flight was
|
|
// sent, indexed by the packet number.
|
|
connectionStats *ConnectionStates
|
|
}
|
|
|
|
func NewBandwidthSampler() *BandwidthSampler {
|
|
return &BandwidthSampler{
|
|
connectionStats: &ConnectionStates{
|
|
stats: make(map[congestion.PacketNumber]*ConnectionStateOnSentPacket),
|
|
},
|
|
}
|
|
}
|
|
|
|
// OnPacketSent Inputs the sent packet information into the sampler. Assumes that all
|
|
// packets are sent in order. The information about the packet will not be
|
|
// released from the sampler until it the packet is either acknowledged or
|
|
// declared lost.
|
|
func (s *BandwidthSampler) OnPacketSent(sentTime time.Time, lastSentPacket congestion.PacketNumber, sentBytes, bytesInFlight congestion.ByteCount, hasRetransmittableData bool) {
|
|
s.lastSendPacket = lastSentPacket
|
|
|
|
if !hasRetransmittableData {
|
|
return
|
|
}
|
|
|
|
s.totalBytesSent += sentBytes
|
|
|
|
// If there are no packets in flight, the time at which the new transmission
|
|
// opens can be treated as the A_0 point for the purpose of bandwidth
|
|
// sampling. This underestimates bandwidth to some extent, and produces some
|
|
// artificially low samples for most packets in flight, but it provides with
|
|
// samples at important points where we would not have them otherwise, most
|
|
// importantly at the beginning of the connection.
|
|
if bytesInFlight == 0 {
|
|
s.lastAckedPacketAckTime = sentTime
|
|
s.totalBytesSentAtLastAckedPacket = s.totalBytesSent
|
|
|
|
// In this situation ack compression is not a concern, set send rate to
|
|
// effectively infinite.
|
|
s.lastAckedPacketSentTime = sentTime
|
|
}
|
|
|
|
s.connectionStats.Insert(lastSentPacket, sentTime, sentBytes, s)
|
|
}
|
|
|
|
// OnPacketAcked Notifies the sampler that the |lastAckedPacket| is acknowledged. Returns a
|
|
// bandwidth sample. If no bandwidth sample is available,
|
|
// QuicBandwidth::Zero() is returned.
|
|
func (s *BandwidthSampler) OnPacketAcked(ackTime time.Time, lastAckedPacket congestion.PacketNumber) *BandwidthSample {
|
|
sentPacketState := s.connectionStats.Get(lastAckedPacket)
|
|
if sentPacketState == nil {
|
|
return NewBandwidthSample()
|
|
}
|
|
|
|
sample := s.onPacketAckedInner(ackTime, lastAckedPacket, sentPacketState)
|
|
s.connectionStats.Remove(lastAckedPacket)
|
|
|
|
return sample
|
|
}
|
|
|
|
// onPacketAckedInner Handles the actual bandwidth calculations, whereas the outer method handles
|
|
// retrieving and removing |sentPacket|.
|
|
func (s *BandwidthSampler) onPacketAckedInner(ackTime time.Time, lastAckedPacket congestion.PacketNumber, sentPacket *ConnectionStateOnSentPacket) *BandwidthSample {
|
|
s.totalBytesAcked += sentPacket.size
|
|
|
|
s.totalBytesSentAtLastAckedPacket = sentPacket.sendTimeState.totalBytesSent
|
|
s.lastAckedPacketSentTime = sentPacket.sendTime
|
|
s.lastAckedPacketAckTime = ackTime
|
|
|
|
// Exit app-limited phase once a packet that was sent while the connection is
|
|
// not app-limited is acknowledged.
|
|
if s.isAppLimited && lastAckedPacket > s.endOfAppLimitedPhase {
|
|
s.isAppLimited = false
|
|
}
|
|
|
|
// There might have been no packets acknowledged at the moment when the
|
|
// current packet was sent. In that case, there is no bandwidth sample to
|
|
// make.
|
|
if sentPacket.lastAckedPacketSentTime.IsZero() {
|
|
return NewBandwidthSample()
|
|
}
|
|
|
|
// Infinite rate indicates that the sampler is supposed to discard the
|
|
// current send rate sample and use only the ack rate.
|
|
sendRate := InfiniteBandwidth
|
|
if sentPacket.sendTime.After(sentPacket.lastAckedPacketSentTime) {
|
|
sendRate = BandwidthFromDelta(sentPacket.sendTimeState.totalBytesSent-sentPacket.totalBytesSentAtLastAckedPacket, sentPacket.sendTime.Sub(sentPacket.lastAckedPacketSentTime))
|
|
}
|
|
|
|
// During the slope calculation, ensure that ack time of the current packet is
|
|
// always larger than the time of the previous packet, otherwise division by
|
|
// zero or integer underflow can occur.
|
|
if !ackTime.After(sentPacket.lastAckedPacketAckTime) {
|
|
// TODO(wub): Compare this code count before and after fixing clock jitter
|
|
// issue.
|
|
// if sentPacket.lastAckedPacketAckTime.Equal(sentPacket.sendTime) {
|
|
// This is the 1st packet after quiescense.
|
|
// QUIC_CODE_COUNT_N(quic_prev_ack_time_larger_than_current_ack_time, 1, 2);
|
|
// } else {
|
|
// QUIC_CODE_COUNT_N(quic_prev_ack_time_larger_than_current_ack_time, 2, 2);
|
|
// }
|
|
|
|
return NewBandwidthSample()
|
|
}
|
|
|
|
ackRate := BandwidthFromDelta(s.totalBytesAcked-sentPacket.sendTimeState.totalBytesAcked,
|
|
ackTime.Sub(sentPacket.lastAckedPacketAckTime))
|
|
|
|
// Note: this sample does not account for delayed acknowledgement time. This
|
|
// means that the RTT measurements here can be artificially high, especially
|
|
// on low bandwidth connections.
|
|
sample := &BandwidthSample{
|
|
bandwidth: minBandwidth(sendRate, ackRate),
|
|
rtt: ackTime.Sub(sentPacket.sendTime),
|
|
}
|
|
|
|
SentPacketToSendTimeState(sentPacket, &sample.stateAtSend)
|
|
return sample
|
|
}
|
|
|
|
// OnPacketLost Informs the sampler that a packet is considered lost and it should no
|
|
// longer keep track of it.
|
|
func (s *BandwidthSampler) OnPacketLost(packetNumber congestion.PacketNumber) SendTimeState {
|
|
ok, sentPacket := s.connectionStats.Remove(packetNumber)
|
|
sendTimeState := SendTimeState{
|
|
isValid: ok,
|
|
}
|
|
if sentPacket != nil {
|
|
s.totalBytesLost += sentPacket.size
|
|
SentPacketToSendTimeState(sentPacket, &sendTimeState)
|
|
}
|
|
|
|
return sendTimeState
|
|
}
|
|
|
|
// OnAppLimited Informs the sampler that the connection is currently app-limited, causing
|
|
// the sampler to enter the app-limited phase. The phase will expire by
|
|
// itself.
|
|
func (s *BandwidthSampler) OnAppLimited() {
|
|
s.isAppLimited = true
|
|
s.endOfAppLimitedPhase = s.lastSendPacket
|
|
}
|
|
|
|
// SentPacketToSendTimeState Copy a subset of the (private) ConnectionStateOnSentPacket to the (public)
|
|
// SendTimeState. Always set send_time_state->is_valid to true.
|
|
func SentPacketToSendTimeState(sentPacket *ConnectionStateOnSentPacket, sendTimeState *SendTimeState) {
|
|
sendTimeState.isAppLimited = sentPacket.sendTimeState.isAppLimited
|
|
sendTimeState.totalBytesSent = sentPacket.sendTimeState.totalBytesSent
|
|
sendTimeState.totalBytesAcked = sentPacket.sendTimeState.totalBytesAcked
|
|
sendTimeState.totalBytesLost = sentPacket.sendTimeState.totalBytesLost
|
|
sendTimeState.isValid = true
|
|
}
|
|
|
|
// ConnectionStates Record of the connection state at the point where each packet in flight was
|
|
// sent, indexed by the packet number.
|
|
// FIXME: using LinkedList replace map to fast remove all the packets lower than the specified packet number.
|
|
type ConnectionStates struct {
|
|
stats map[congestion.PacketNumber]*ConnectionStateOnSentPacket
|
|
}
|
|
|
|
func (s *ConnectionStates) Insert(packetNumber congestion.PacketNumber, sentTime time.Time, bytes congestion.ByteCount, sampler *BandwidthSampler) bool {
|
|
if _, ok := s.stats[packetNumber]; ok {
|
|
return false
|
|
}
|
|
|
|
s.stats[packetNumber] = NewConnectionStateOnSentPacket(packetNumber, sentTime, bytes, sampler)
|
|
return true
|
|
}
|
|
|
|
func (s *ConnectionStates) Get(packetNumber congestion.PacketNumber) *ConnectionStateOnSentPacket {
|
|
return s.stats[packetNumber]
|
|
}
|
|
|
|
func (s *ConnectionStates) Remove(packetNumber congestion.PacketNumber) (bool, *ConnectionStateOnSentPacket) {
|
|
state, ok := s.stats[packetNumber]
|
|
if ok {
|
|
delete(s.stats, packetNumber)
|
|
}
|
|
return ok, state
|
|
}
|
|
|
|
func NewConnectionStateOnSentPacket(packetNumber congestion.PacketNumber, sentTime time.Time, bytes congestion.ByteCount, sampler *BandwidthSampler) *ConnectionStateOnSentPacket {
|
|
return &ConnectionStateOnSentPacket{
|
|
packetNumber: packetNumber,
|
|
sendTime: sentTime,
|
|
size: bytes,
|
|
lastAckedPacketSentTime: sampler.lastAckedPacketSentTime,
|
|
lastAckedPacketAckTime: sampler.lastAckedPacketAckTime,
|
|
totalBytesSentAtLastAckedPacket: sampler.totalBytesSentAtLastAckedPacket,
|
|
sendTimeState: SendTimeState{
|
|
isValid: true,
|
|
isAppLimited: sampler.isAppLimited,
|
|
totalBytesSent: sampler.totalBytesSent,
|
|
totalBytesAcked: sampler.totalBytesAcked,
|
|
totalBytesLost: sampler.totalBytesLost,
|
|
},
|
|
}
|
|
}
|