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fix retransmission logic for path probing packets (#5241)

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To achieve an exponential backoff, the timer should only be reset after
having fired.
This commit is contained in:
Marten Seemann
2025-06-26 13:49:44 +08:00
committed by GitHub
parent b94fc4d2d4
commit 1b9add1bec
2 changed files with 26 additions and 17 deletions
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2
path_manager_outgoing.go
View File

@@ -50,6 +50,7 @@ func (p *Path) Probe(ctx context.Context) error {
p.validated.Store(true)
return nil
case <-timerChan:
nextProbeDur *= 2 // exponential backoff
p.pathManager.enqueueProbe(p)
case <-path.ProbeSent():
case <-p.abandon:
@@ -61,7 +62,6 @@ func (p *Path) Probe(ctx context.Context) error {
}
timer = time.NewTimer(nextProbeDur)
timerChan = timer.C
nextProbeDur *= 2 // exponential backoff
}
}

41
path_manager_outgoing_test.go
View File

@@ -119,7 +119,7 @@ func TestPathManagerOutgoingRetransmissions(t *testing.T) {
require.False(t, ok)
tr1 := &Transport{}
initialRTT := scaleDuration(2 * time.Millisecond)
initialRTT := scaleDuration(5 * time.Millisecond)
p := pm.NewPath(tr1, initialRTT, func() {})
pathChallengeChan := make(chan [8]byte)
@@ -146,31 +146,40 @@ func TestPathManagerOutgoingRetransmissions(t *testing.T) {
go func() { errChan <- p.Probe(context.Background()) }()
start := time.Now()
var pathChallenges [][8]byte
type result struct {
pc *[8]byte
took time.Duration
}
var results []result
for range 4 {
select {
case err := <-errChan:
require.NoError(t, err)
case pc := <-pathChallengeChan:
pathChallenges = append(pathChallenges, pc)
results = append(results, result{pc: &pc, took: time.Since(start)})
case <-time.After(scaleDuration(time.Second)):
t.Fatal("timeout")
}
}
took := time.Since(start)
require.NotContains(t, pathChallenges, [8]byte{})
require.NotEqual(t, pathChallenges[0], pathChallenges[1])
require.NotEqual(t, pathChallenges[0], pathChallenges[2])
require.NotEqual(t, pathChallenges[0], pathChallenges[3])
require.NotEqual(t, pathChallenges[1], pathChallenges[2])
require.NotEqual(t, pathChallenges[2], pathChallenges[3])
require.Greater(t, took, initialRTT*(1+2+4+8))
require.Less(t, took, initialRTT*(1+2+4+8)*3/2)
for i, r1 := range results {
require.NotNil(t, r1.pc)
if i > 0 {
took := r1.took - results[i-1].took
t.Log("took", took)
require.Greater(t, took, initialRTT<<(i-1))
require.Less(t, took, initialRTT<<i)
}
for j, r2 := range results {
if i == j {
continue
}
require.NotEqual(t, r1.pc, r2.pc)
}
}
// receiving a PATH_RESPONSE for any of the PATH_CHALLENGES completes path validation
pm.HandlePathResponseFrame(&wire.PathResponseFrame{Data: pathChallenges[2]})
pm.HandlePathResponseFrame(&wire.PathResponseFrame{Data: *results[2].pc})
select {
case err := <-errChan:
@@ -180,7 +189,7 @@ func TestPathManagerOutgoingRetransmissions(t *testing.T) {
}
// It is valid to probe again
pathChallenges = pathChallenges[:0]
results = results[:0]
ctx, cancel := context.WithCancel(context.Background())
go func() { errChan <- p.Probe(ctx) }()
@@ -189,7 +198,7 @@ func TestPathManagerOutgoingRetransmissions(t *testing.T) {
case err := <-errChan:
require.NoError(t, err)
case pc := <-pathChallengeChan:
pathChallenges = append(pathChallenges, pc)
results = append(results, result{pc: &pc, took: time.Since(start)})
case <-time.After(scaleDuration(time.Second)):
t.Fatal("timeout")
}