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tailscale/wgengine/bench/trafficgen.go

261 lines
6.6 KiB
Go

// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"encoding/binary"
"fmt"
"log"
"net/netip"
"sync"
"time"
"tailscale.com/net/packet"
"tailscale.com/types/ipproto"
)
type Snapshot struct {
WhenNsec int64 // current time
timeAcc int64 // accumulated time (+NSecPerTx per transmit)
LastSeqTx int64 // last sequence number sent
LastSeqRx int64 // last sequence number received
TotalLost int64 // packets out-of-order or lost so far
TotalOOO int64 // packets out-of-order so far
TotalBytesRx int64 // total bytes received so far
}
type Delta struct {
DurationNsec int64
TxPackets int64
RxPackets int64
LostPackets int64
OOOPackets int64
Bytes int64
}
func (b Snapshot) Sub(a Snapshot) Delta {
return Delta{
DurationNsec: b.WhenNsec - a.WhenNsec,
TxPackets: b.LastSeqTx - a.LastSeqTx,
RxPackets: (b.LastSeqRx - a.LastSeqRx) -
(b.TotalLost - a.TotalLost) +
(b.TotalOOO - a.TotalOOO),
LostPackets: b.TotalLost - a.TotalLost,
OOOPackets: b.TotalOOO - a.TotalOOO,
Bytes: b.TotalBytesRx - a.TotalBytesRx,
}
}
func (d Delta) String() string {
return fmt.Sprintf("tx=%-6d rx=%-4d (%6d = %.1f%% loss) (%d OOO) (%4.1f Mbit/s)",
d.TxPackets, d.RxPackets, d.LostPackets,
float64(d.LostPackets)*100/float64(d.TxPackets),
d.OOOPackets,
float64(d.Bytes)*8*1e9/float64(d.DurationNsec)/1e6)
}
type TrafficGen struct {
mu sync.Mutex
cur, prev Snapshot // snapshots used for rate control
buf []byte // pre-generated packet buffer
done bool // true if the test has completed
onFirstPacket func() // function to call on first received packet
// maxPackets is the max packets to receive (not send) before
// ending the test. If it's zero, the test runs forever.
maxPackets int64
// nsPerPacket is the target average nanoseconds between packets.
// It's initially zero, which means transmit as fast as the
// caller wants to go.
nsPerPacket int64
// ppsHistory is the observed packets-per-second from recent
// samples.
ppsHistory [5]int64
}
// NewTrafficGen creates a new, initially locked, TrafficGen.
// Until Start() is called, Generate() will block forever.
func NewTrafficGen(onFirstPacket func()) *TrafficGen {
t := TrafficGen{
onFirstPacket: onFirstPacket,
}
// initially locked, until first Start()
t.mu.Lock()
return &t
}
// Start starts the traffic generator. It assumes mu is already locked,
// and unlocks it.
func (t *TrafficGen) Start(src, dst netip.Addr, bytesPerPacket int, maxPackets int64) {
h12 := packet.ICMP4Header{
IP4Header: packet.IP4Header{
IPProto: ipproto.ICMPv4,
IPID: 0,
Src: src,
Dst: dst,
},
Type: packet.ICMP4EchoRequest,
Code: packet.ICMP4NoCode,
}
// ensure there's room for ICMP header plus sequence number
if bytesPerPacket < ICMPMinSize+8 {
log.Fatalf("bytesPerPacket must be > 24+8")
}
t.maxPackets = maxPackets
payload := make([]byte, bytesPerPacket-ICMPMinSize)
t.buf = packet.Generate(h12, payload)
t.mu.Unlock()
}
func (t *TrafficGen) Snap() Snapshot {
t.mu.Lock()
defer t.mu.Unlock()
t.cur.WhenNsec = time.Now().UnixNano()
return t.cur
}
func (t *TrafficGen) Running() bool {
t.mu.Lock()
defer t.mu.Unlock()
return !t.done
}
// Generate produces the next packet in the sequence. It sleeps if
// it's too soon for the next packet to be sent.
//
// The generated packet is placed into buf at offset ofs, for compatibility
// with the wireguard-go conventions.
//
// The return value is the number of bytes generated in the packet, or 0
// if the test has finished running.
func (t *TrafficGen) Generate(b []byte, ofs int) int {
t.mu.Lock()
now := time.Now().UnixNano()
if t.nsPerPacket == 0 || t.cur.timeAcc == 0 {
t.cur.timeAcc = now - 1
}
if t.cur.timeAcc >= now {
// too soon
t.mu.Unlock()
time.Sleep(time.Duration(t.cur.timeAcc-now) * time.Nanosecond)
t.mu.Lock()
now = t.cur.timeAcc
}
if t.done {
t.mu.Unlock()
return 0
}
t.cur.timeAcc += t.nsPerPacket
t.cur.LastSeqTx += 1
t.cur.WhenNsec = now
seq := t.cur.LastSeqTx
t.mu.Unlock()
copy(b[ofs:], t.buf)
binary.BigEndian.PutUint64(
b[ofs+ICMPMinSize:ofs+ICMPMinSize+8],
uint64(seq))
return len(t.buf)
}
// GotPacket processes a packet that came back on the receive side.
func (t *TrafficGen) GotPacket(b []byte, ofs int) {
t.mu.Lock()
defer t.mu.Unlock()
s := &t.cur
seq := int64(binary.BigEndian.Uint64(
b[ofs+ICMPMinSize : ofs+ICMPMinSize+8]))
if seq > s.LastSeqRx {
if s.LastSeqRx > 0 {
// only count lost packets after the very first
// successful one.
s.TotalLost += seq - s.LastSeqRx - 1
}
s.LastSeqRx = seq
} else {
s.TotalOOO += 1
}
// +1 packet since we only start counting after the first one
if t.maxPackets > 0 && s.LastSeqRx >= t.maxPackets+1 {
t.done = true
}
s.TotalBytesRx += int64(len(b) - ofs)
f := t.onFirstPacket
t.onFirstPacket = nil
if f != nil {
f()
}
}
// Adjust tunes the transmit rate based on the received packets.
// The goal is to converge on the fastest transmit rate that still has
// minimal packet loss. Returns the new target rate in packets/sec.
//
// We need to play this guessing game in order to balance out tx and rx
// rates when there's a lossy network between them. Otherwise we can end
// up using 99% of the CPU to blast out transmitted packets and leaving only
// 1% to receive them, leading to a misleading throughput calculation.
//
// Call this function multiple times per second.
func (t *TrafficGen) Adjust() (pps int64) {
t.mu.Lock()
defer t.mu.Unlock()
d := t.cur.Sub(t.prev)
// don't adjust rate until the first full period *after* receiving
// the first packet. This skips any handshake time in the underlying
// transport.
if t.prev.LastSeqRx == 0 || d.DurationNsec == 0 {
t.prev = t.cur
return 0 // no estimate yet, continue at max speed
}
pps = int64(d.RxPackets) * 1e9 / int64(d.DurationNsec)
// We use a rate selection algorithm based loosely on TCP BBR.
// Basically, we set the transmit rate to be a bit higher than
// the best observed transmit rate in the last several time
// periods. This guarantees some packet loss, but should converge
// quickly on a rate near the sustainable maximum.
bestPPS := pps
for _, p := range t.ppsHistory {
if p > bestPPS {
bestPPS = p
}
}
if pps > 0 && t.prev.WhenNsec > 0 {
copy(t.ppsHistory[1:], t.ppsHistory[0:len(t.ppsHistory)-1])
t.ppsHistory[0] = pps
}
if bestPPS > 0 {
pps = bestPPS * 103 / 100
t.nsPerPacket = int64(1e9 / pps)
}
t.prev = t.cur
return pps
}