/
rtt.go
201 lines (169 loc) · 4.85 KB
/
rtt.go
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package mokumokuren
import (
"encoding/binary"
"fmt"
"log"
"time"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
)
var RTTDataIndex int
func init() {
RTTDataIndex = RegisterDataIndex()
}
type RTTData struct {
// Measured handshake RTT
HandshakeRTT time.Duration
firstReverse *time.Time
secondForward *time.Time
// Minimum running RTT sample
MinimumRTT time.Duration
// Mean running RTT sample
MeanRTT time.Duration
// Number of RTT samples
RTTSampleCount uint
tcpTimestampSeen [2]bool
UsingTCPTimestamps bool
component [2]time.Duration
awaitTime [2]*time.Time
awaitVal [2]uint32
}
func (d *RTTData) String() string {
if d.HandshakeRTT == 0 && d.RTTSampleCount == 0 {
return "(no RTT)"
} else if d.HandshakeRTT != 0 && d.RTTSampleCount == 0 {
return fmt.Sprintf("(hs RTT %.3f ms)",
float64(d.HandshakeRTT)/1000000)
} else if d.HandshakeRTT == 0 && d.RTTSampleCount != 0 {
return fmt.Sprintf("(min/mean RTT %.3f/%.3f ms)",
float64(d.MinimumRTT)/1000000, float64(d.MeanRTT)/1000000)
} else {
return fmt.Sprintf("(hs/min/mean RTT %.3f/%.3f/%.3f ms)",
float64(d.HandshakeRTT)/1000000, float64(d.MinimumRTT)/1000000, float64(d.MeanRTT)/1000000)
}
}
///////////////////////////////////////////////////////////////////////
//
// TCP handshake tracking
//
//////////////////////////////////////////////////////////////////////
func rttInit(fe *FlowEntry, pe *PacketEvent) bool {
fe.Data[RTTDataIndex] = new(RTTData)
return true
}
func extractTimestamp(tcp *layers.TCP) (uint32, uint32, bool) {
for _, opt := range tcp.Options {
if opt.OptionType == layers.TCPOptionKindTimestamps && len(opt.OptionData) >= 8 {
tsval := binary.BigEndian.Uint32(opt.OptionData[0:4])
tsecr := binary.BigEndian.Uint32(opt.OptionData[4:8])
return tsval, tsecr, true
}
}
return 0, 0, false
}
func wrapCompare(a, b uint32) int {
if a == b {
return 0
} else if ((a - b) & 0x80000000) > 0 {
return -1
} else {
return 1
}
}
func sampleRTT(d *RTTData) {
sample := d.component[0] + d.component[1]
if d.RTTSampleCount == 0 {
d.MinimumRTT = sample
d.MeanRTT = sample
} else {
if sample < d.MinimumRTT {
d.MinimumRTT = sample
}
d.MeanRTT = ((d.MeanRTT * time.Duration(d.RTTSampleCount)) + sample) / time.Duration(d.RTTSampleCount+1)
}
d.RTTSampleCount += 1
}
// for checking TCP handshake RTT
func rttTCPPacket(fe *FlowEntry, pe *PacketEvent, layer gopacket.Layer) bool {
tcp := layer.(*layers.TCP)
d := fe.Data[RTTDataIndex].(*RTTData)
// Calculate handshake RTT
if d.firstReverse == nil && pe.Reverse && tcp.SYN && tcp.ACK {
d.firstReverse = pe.Timestamp
} else if d.secondForward == nil && !pe.Reverse && !tcp.SYN {
d.secondForward = pe.Timestamp
d.HandshakeRTT = d.secondForward.Sub(*fe.StartTime)
}
dir := 0
rdir := 1
if pe.Reverse {
dir = 1
rdir = 0
}
// try to get a timestamp
tsval, tsecr, tsok := extractTimestamp(tcp)
// check to see if we'd like to switch to timestamps
if tsok {
d.tcpTimestampSeen[dir] = true
if d.tcpTimestampSeen[0] && d.tcpTimestampSeen[1] && !d.UsingTCPTimestamps {
d.UsingTCPTimestamps = true
d.awaitTime[0] = nil
d.awaitTime[1] = nil
d.awaitVal[0] = 0
d.awaitVal[1] = 0
}
}
// check to see if we're waiting for a value that we have
if d.awaitTime[dir] != nil {
if (d.UsingTCPTimestamps && wrapCompare(tsecr, d.awaitVal[dir]) > 0) ||
(!d.UsingTCPTimestamps && wrapCompare(tcp.Ack, d.awaitVal[dir]) > 0) {
d.component[dir] = pe.Timestamp.Sub(*d.awaitTime[dir])
d.awaitTime[dir] = nil
sampleRTT(d)
}
}
// check to see if we need to grab a new value to wait for
if d.awaitTime[rdir] == nil {
d.awaitTime[rdir] = pe.Timestamp
if d.UsingTCPTimestamps {
d.awaitVal[rdir] = tsval
} else {
d.awaitVal[rdir] = tcp.Seq
}
}
return true
}
// for checking TCP handshake RTT
func rttUDPPacket(fe *FlowEntry, pe *PacketEvent, layer gopacket.Layer) bool {
udp := layer.(*layers.UDP)
d := fe.Data[RTTDataIndex].(*RTTData)
// shortcircuit if we already saw a handshake...
if d.firstReverse != nil && d.secondForward != nil {
return true
}
// try to parse a quic header
var q QUICHeader
if err := q.ExtractFromUDP(udp); err != nil {
if err != NotQUIC {
log.Printf("error parsing quic header: %s", err.Error())
}
return true
}
// now calculate handshake RTT
if d.firstReverse == nil && pe.Reverse && q.PktType == QUICPktTypeServerCleartext {
d.firstReverse = pe.Timestamp
} else if d.secondForward == nil && q.PktType == QUICPktTypeClientCleartext {
d.secondForward = pe.Timestamp
d.HandshakeRTT = d.secondForward.Sub(*fe.StartTime)
}
// FIXME add measurement byte handling
return true
}
func (ft *FlowTable) TrackRoundTripTime() {
ft.AddInitialFunction(rttInit)
ft.AddLayerFunction(rttTCPPacket, layers.LayerTypeTCP)
if QUICPort != 0 {
// Only try to parse UDP when
ft.AddLayerFunction(rttUDPPacket, layers.LayerTypeUDP)
}
}