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// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.21
package quic
import (
"testing"
"time"
)
func TestPacerStartup(t *testing.T) {
p := &pacerTest{
cwnd: 10000,
rtt: 100 * time.Millisecond,
timerGranularity: 1 * time.Millisecond,
}
p.init(t)
t.Logf("# initial burst permits sending ten packets")
for i := 0; i < 10; i++ {
p.sendPacket(1000)
}
t.Logf("# empty bucket allows for one more packet")
p.sendPacket(1000)
t.Logf("# sending 1000 byte packets with 8ms interval:")
t.Logf("# (smoothed_rtt * packet_size / congestion_window) / 1.25")
t.Logf("# (100ms * 1000 / 10000) / 1.25 = 8ms")
p.wantSendDelay(8 * time.Millisecond)
p.advance(8 * time.Millisecond)
p.sendPacket(1000)
p.wantSendDelay(8 * time.Millisecond)
t.Logf("# accumulate enough window for two packets")
p.advance(16 * time.Millisecond)
p.sendPacket(1000)
p.sendPacket(1000)
p.wantSendDelay(8 * time.Millisecond)
t.Logf("# window does not grow to more than burst limit")
p.advance(1 * time.Second)
for i := 0; i < 11; i++ {
p.sendPacket(1000)
}
p.wantSendDelay(8 * time.Millisecond)
}
func TestPacerTimerGranularity(t *testing.T) {
p := &pacerTest{
cwnd: 10000,
rtt: 100 * time.Millisecond,
timerGranularity: 1 * time.Millisecond,
}
p.init(t)
t.Logf("# consume initial burst")
for i := 0; i < 11; i++ {
p.sendPacket(1000)
}
p.wantSendDelay(8 * time.Millisecond)
t.Logf("# small advance in time does not permit sending")
p.advance(4 * time.Millisecond)
p.wantSendDelay(4 * time.Millisecond)
t.Logf("# advancing to within timerGranularity of next send permits send")
p.advance(3 * time.Millisecond)
p.wantSendDelay(0)
t.Logf("# early send adds skipped delay (1ms) to next send (8ms)")
p.sendPacket(1000)
p.wantSendDelay(9 * time.Millisecond)
}
func TestPacerChangingRate(t *testing.T) {
p := &pacerTest{
cwnd: 10000,
rtt: 100 * time.Millisecond,
timerGranularity: 0,
}
p.init(t)
t.Logf("# consume initial burst")
for i := 0; i < 11; i++ {
p.sendPacket(1000)
}
p.wantSendDelay(8 * time.Millisecond)
p.advance(8 * time.Millisecond)
t.Logf("# set congestion window to 20000, 1000 byte interval is 4ms")
p.cwnd = 20000
p.sendPacket(1000)
p.wantSendDelay(4 * time.Millisecond)
p.advance(4 * time.Millisecond)
t.Logf("# set rtt to 200ms, 1000 byte interval is 8ms")
p.rtt = 200 * time.Millisecond
p.sendPacket(1000)
p.wantSendDelay(8 * time.Millisecond)
p.advance(8 * time.Millisecond)
t.Logf("# set congestion window to 40000, 1000 byte interval is 4ms")
p.cwnd = 40000
p.advance(8 * time.Millisecond)
p.sendPacket(1000)
p.sendPacket(1000)
p.sendPacket(1000)
p.wantSendDelay(4 * time.Millisecond)
}
func TestPacerTimeReverses(t *testing.T) {
p := &pacerTest{
cwnd: 10000,
rtt: 100 * time.Millisecond,
timerGranularity: 0,
}
p.init(t)
t.Logf("# consume initial burst")
for i := 0; i < 11; i++ {
p.sendPacket(1000)
}
p.wantSendDelay(8 * time.Millisecond)
t.Logf("# reverse time")
p.advance(-4 * time.Millisecond)
p.sendPacket(1000)
p.wantSendDelay(8 * time.Millisecond)
p.advance(8 * time.Millisecond)
p.sendPacket(1000)
p.wantSendDelay(8 * time.Millisecond)
}
func TestPacerZeroRTT(t *testing.T) {
p := &pacerTest{
cwnd: 10000,
rtt: 0,
timerGranularity: 0,
}
p.init(t)
t.Logf("# with rtt 0, the pacer does not limit sending")
for i := 0; i < 20; i++ {
p.sendPacket(1000)
}
p.advance(1 * time.Second)
for i := 0; i < 20; i++ {
p.sendPacket(1000)
}
}
func TestPacerZeroCongestionWindow(t *testing.T) {
p := &pacerTest{
cwnd: 10000,
rtt: 100 * time.Millisecond,
timerGranularity: 0,
}
p.init(t)
p.cwnd = 0
t.Logf("# with cwnd 0, the pacer does not limit sending")
for i := 0; i < 20; i++ {
p.sendPacket(1000)
}
}
type pacerTest struct {
t *testing.T
p pacerState
timerGranularity time.Duration
cwnd int
rtt time.Duration
now time.Time
}
func newPacerTest(t *testing.T, congestionWindow int, rtt time.Duration) *pacerTest {
p := &pacerTest{
now: time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC),
cwnd: congestionWindow,
rtt: rtt,
}
p.p.init(p.now, congestionWindow, p.timerGranularity)
return p
}
func (p *pacerTest) init(t *testing.T) {
p.t = t
p.now = time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
p.p.init(p.now, p.cwnd, p.timerGranularity)
t.Logf("# initial congestion window: %v", p.cwnd)
t.Logf("# timer granularity: %v", p.timerGranularity)
}
func (p *pacerTest) advance(d time.Duration) {
p.t.Logf("advance time %v", d)
p.now = p.now.Add(d)
p.p.advance(p.now, p.cwnd, p.rtt)
}
func (p *pacerTest) sendPacket(size int) {
if canSend, next := p.p.canSend(p.now); !canSend {
p.t.Fatalf("ERROR: pacer unexpectedly blocked send, delay=%v", next.Sub(p.now))
}
p.t.Logf("send packet of size %v", size)
p.p.packetSent(p.now, size, p.cwnd, p.rtt)
}
func (p *pacerTest) wantSendDelay(want time.Duration) {
wantCanSend := want == 0
gotCanSend, next := p.p.canSend(p.now)
var got time.Duration
if !gotCanSend {
got = next.Sub(p.now)
}
p.t.Logf("# pacer send delay: %v", got)
if got != want || gotCanSend != wantCanSend {
p.t.Fatalf("ERROR: pacer send delay = %v (can send: %v); want %v, %v", got, gotCanSend, want, wantCanSend)
}
}
func (p *pacerTest) sendDelay() time.Duration {
canSend, next := p.p.canSend(p.now)
if canSend {
return 0
}
return next.Sub(p.now)
}
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