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make Path MTU Discovery resilient to random packet loss (#4545)

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This commit is contained in:
Marten Seemann
2024-06-04 17:10:11 +08:00
committed by GitHub
parent 950de0d8ed
commit 0db354456a
3 changed files with 226 additions and 62 deletions
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148
mtu_discoverer_test.go
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@@ -1,9 +1,11 @@
package quic
import (
"math/rand"
"fmt"
"time"
"golang.org/x/exp/rand"
"github.com/quic-go/quic-go/internal/protocol"
"github.com/quic-go/quic-go/internal/utils"
"github.com/quic-go/quic-go/logging"
@@ -25,6 +27,7 @@ var _ = Describe("MTU Discoverer", func() {
now time.Time
discoveredMTU protocol.ByteCount
)
r := rand.New(rand.NewSource(uint64(GinkgoRandomSeed())))
BeforeEach(func() {
rttStats = &utils.RTTStats{}
@@ -76,6 +79,7 @@ var _ = Describe("MTU Discoverer", func() {
t := now.Add(5 * rtt)
for d.ShouldSendProbe(t) {
ping, size := d.GetPing()
fmt.Println("sending", size)
ping.Handler.OnAcked(ping.Frame)
sizes = append(sizes, size)
t = t.Add(5 * rtt)
@@ -91,53 +95,107 @@ var _ = Describe("MTU Discoverer", func() {
}
})
It("finds the MTU", func() {
const rep = 3000
var maxDiff protocol.ByteCount
for i := 0; i < rep; i++ {
maxMTU := protocol.ByteCount(rand.Intn(int(3000-startMTU))) + startMTU + 1
currentMTU := startMTU
var tracedMTU protocol.ByteCount
var tracerDone bool
d := newMTUDiscoverer(
rttStats,
startMTU,
maxMTU,
func(s protocol.ByteCount) { currentMTU = s },
&logging.ConnectionTracer{
UpdatedMTU: func(mtu logging.ByteCount, done bool) {
tracedMTU = mtu
tracerDone = done
},
It("finds the MTU", MustPassRepeatedly(300), func() {
maxMTU := protocol.ByteCount(r.Intn(int(3000-startMTU))) + startMTU + 1
currentMTU := startMTU
var tracedMTU protocol.ByteCount
var tracerDone bool
d := newMTUDiscoverer(
rttStats,
startMTU,
maxMTU,
func(s protocol.ByteCount) { currentMTU = s },
&logging.ConnectionTracer{
UpdatedMTU: func(mtu logging.ByteCount, done bool) {
tracedMTU = mtu
tracerDone = done
},
)
d.Start()
now := time.Now()
realMTU := protocol.ByteCount(rand.Intn(int(maxMTU-startMTU))) + startMTU
t := now.Add(mtuProbeDelay * rtt)
var count int
for d.ShouldSendProbe(t) {
if count > 25 {
Fail("too many iterations")
}
count++
ping, size := d.GetPing()
if size <= realMTU {
ping.Handler.OnAcked(ping.Frame)
} else {
ping.Handler.OnLost(ping.Frame)
}
t = t.Add(mtuProbeDelay * rtt)
},
)
d.Start()
now := time.Now()
realMTU := protocol.ByteCount(r.Intn(int(maxMTU-startMTU))) + startMTU
fmt.Fprintf(GinkgoWriter, "MTU: %d, max: %d\n", realMTU, maxMTU)
t := now.Add(mtuProbeDelay * rtt)
var probes []protocol.ByteCount
for d.ShouldSendProbe(t) {
if len(probes) > 24 {
Fail(fmt.Sprintf("too many iterations: %v", probes))
}
diff := realMTU - currentMTU
Expect(diff).To(BeNumerically(">=", 0))
maxDiff = max(maxDiff, diff)
if maxMTU > currentMTU+maxMTU {
Expect(tracedMTU).To(Equal(currentMTU))
Expect(tracerDone).To(BeTrue())
ping, size := d.GetPing()
probes = append(probes, size)
if size <= realMTU {
ping.Handler.OnAcked(ping.Frame)
} else {
ping.Handler.OnLost(ping.Frame)
}
t = t.Add(mtuProbeDelay * rtt)
}
Expect(maxDiff).To(BeEquivalentTo(maxMTUDiff))
diff := realMTU - currentMTU
Expect(diff).To(BeNumerically(">=", 0))
if maxMTU > currentMTU+maxMTU {
Expect(tracedMTU).To(Equal(currentMTU))
Expect(tracerDone).To(BeTrue())
}
fmt.Fprintf(GinkgoWriter, "MTU discovered: %d (diff: %d)\n", currentMTU, diff)
fmt.Fprintf(GinkgoWriter, "probes sent (%d): %v\n", len(probes), probes)
Expect(diff).To(BeNumerically("<=", maxMTUDiff))
})
const maxRandomLoss = maxLostMTUProbes - 1
It(fmt.Sprintf("finds the MTU, with up to %d packets lost", maxRandomLoss), MustPassRepeatedly(500), func() {
maxMTU := protocol.ByteCount(r.Intn(int(3000-startMTU))) + startMTU + 1
currentMTU := startMTU
var tracedMTU protocol.ByteCount
var tracerDone bool
d := newMTUDiscoverer(
rttStats,
startMTU,
maxMTU,
func(s protocol.ByteCount) { currentMTU = s },
&logging.ConnectionTracer{
UpdatedMTU: func(mtu logging.ByteCount, done bool) {
tracedMTU = mtu
tracerDone = done
},
},
)
d.Start()
now := time.Now()
realMTU := protocol.ByteCount(r.Intn(int(maxMTU-startMTU))) + startMTU
fmt.Fprintf(GinkgoWriter, "MTU: %d, max: %d\n", realMTU, maxMTU)
t := now.Add(mtuProbeDelay * rtt)
var probes, randomLosses []protocol.ByteCount
for d.ShouldSendProbe(t) {
if len(probes) > 32 {
Fail(fmt.Sprintf("too many iterations: %v", probes))
}
ping, size := d.GetPing()
probes = append(probes, size)
packetFits := size <= realMTU
var acked bool
if packetFits {
randomLoss := r.Intn(maxLostMTUProbes) == 0 && len(randomLosses) < maxRandomLoss
if randomLoss {
randomLosses = append(randomLosses, size)
} else {
ping.Handler.OnAcked(ping.Frame)
acked = true
}
}
if !acked {
ping.Handler.OnLost(ping.Frame)
}
t = t.Add(mtuProbeDelay * rtt)
}
diff := realMTU - currentMTU
Expect(diff).To(BeNumerically(">=", 0))
if maxMTU > currentMTU+maxMTU {
Expect(tracedMTU).To(Equal(currentMTU))
Expect(tracerDone).To(BeTrue())
}
fmt.Fprintf(GinkgoWriter, "MTU discovered with random losses %v: %d (diff: %d)\n", randomLosses, currentMTU, diff)
fmt.Fprintf(GinkgoWriter, "probes sent (%d): %v\n", len(probes), probes)
Expect(diff).To(BeNumerically("<=", maxMTUDiff))
})
})