Revert "migration: go 1.21"

This reverts commit 33d41338ef.

transport/tuic/congestion/cubic.go

@@ -186,7 +186,7 @@ func (c *Cubic) CongestionWindowAfterAck(
 		targetCongestionWindow = c.originPointCongestionWindow - deltaCongestionWindow
 	}
 	// Limit the CWND increase to half the acked bytes.
-	targetCongestionWindow = min(targetCongestionWindow, currentCongestionWindow+c.ackedBytesCount/2)
+	targetCongestionWindow = Min(targetCongestionWindow, currentCongestionWindow+c.ackedBytesCount/2)
 
 	// Increase the window by approximately Alpha * 1 MSS of bytes every
 	// time we ack an estimated tcp window of bytes.  For small

transport/tuic/congestion/cubic_sender.go

@@ -177,7 +177,7 @@ func (c *cubicSender) OnPacketAcked(
 	priorInFlight congestion.ByteCount,
 	eventTime time.Time,
 ) {
-	c.largestAckedPacketNumber = max(ackedPacketNumber, c.largestAckedPacketNumber)
+	c.largestAckedPacketNumber = Max(ackedPacketNumber, c.largestAckedPacketNumber)
 	if c.InRecovery() {
 		return
 	}
@@ -245,7 +245,7 @@ func (c *cubicSender) maybeIncreaseCwnd(
 			c.numAckedPackets = 0
 		}
 	} else {
-		c.congestionWindow = min(c.maxCongestionWindow(), c.cubic.CongestionWindowAfterAck(ackedBytes, c.congestionWindow, c.rttStats.MinRTT(), eventTime))
+		c.congestionWindow = Min(c.maxCongestionWindow(), c.cubic.CongestionWindowAfterAck(ackedBytes, c.congestionWindow, c.rttStats.MinRTT(), eventTime))
 	}
 }
 

transport/tuic/congestion/hybrid_slow_start.go

@@ -74,8 +74,8 @@ func (s *HybridSlowStart) ShouldExitSlowStart(latestRTT time.Duration, minRTT ti
 		// Divide minRTT by 8 to get a rtt increase threshold for exiting.
 		minRTTincreaseThresholdUs := int64(minRTT / time.Microsecond >> hybridStartDelayFactorExp)
 		// Ensure the rtt threshold is never less than 2ms or more than 16ms.
-		minRTTincreaseThresholdUs = min(minRTTincreaseThresholdUs, hybridStartDelayMaxThresholdUs)
-		minRTTincreaseThreshold := time.Duration(max(minRTTincreaseThresholdUs, hybridStartDelayMinThresholdUs)) * time.Microsecond
+		minRTTincreaseThresholdUs = Min(minRTTincreaseThresholdUs, hybridStartDelayMaxThresholdUs)
+		minRTTincreaseThreshold := time.Duration(Max(minRTTincreaseThresholdUs, hybridStartDelayMinThresholdUs)) * time.Microsecond
 
 		if s.currentMinRTT > (minRTT + minRTTincreaseThreshold) {
 			s.hystartFound = true

transport/tuic/congestion/minmax.go

@@ -16,7 +16,7 @@ func MinNonZeroDuration(a, b time.Duration) time.Duration {
 	if b == 0 {
 		return a
 	}
-	return min(a, b)
+	return Min(a, b)
 }
 
 // AbsDuration returns the absolute value of a time duration

transport/tuic/congestion/minmax_go120.go

@@ -0,0 +1,19 @@
+//go:build !go1.21
+
+package congestion
+
+import "golang.org/x/exp/constraints"
+
+func Max[T constraints.Ordered](a, b T) T {
+	if a < b {
+		return b
+	}
+	return a
+}
+
+func Min[T constraints.Ordered](a, b T) T {
+	if a < b {
+		return a
+	}
+	return b
+}

transport/tuic/congestion/minmax_go121.go

@@ -0,0 +1,13 @@
+//go:build go1.21
+
+package congestion
+
+import "cmp"
+
+func Max[T cmp.Ordered](a, b T) T {
+	return max(a, b)
+}
+
+func Min[T cmp.Ordered](a, b T) T {
+	return min(a, b)
+}

transport/tuic/congestion/pacer.go

@@ -52,11 +52,11 @@ func (p *pacer) Budget(now time.Time) congestion.ByteCount {
 		return p.maxBurstSize()
 	}
 	budget := p.budgetAtLastSent + (congestion.ByteCount(p.getAdjustedBandwidth())*congestion.ByteCount(now.Sub(p.lastSentTime).Nanoseconds()))/1e9
-	return min(p.maxBurstSize(), budget)
+	return Min(p.maxBurstSize(), budget)
 }
 
 func (p *pacer) maxBurstSize() congestion.ByteCount {
-	return max(
+	return Max(
 		congestion.ByteCount(uint64((MinPacingDelay+TimerGranularity).Nanoseconds())*p.getAdjustedBandwidth())/1e9,
 		maxBurstSizePackets*p.maxDatagramSize,
 	)
@@ -68,7 +68,7 @@ func (p *pacer) TimeUntilSend() time.Time {
 	if p.budgetAtLastSent >= p.maxDatagramSize {
 		return time.Time{}
 	}
-	return p.lastSentTime.Add(max(
+	return p.lastSentTime.Add(Max(
 		MinPacingDelay,
 		time.Duration(math.Ceil(float64(p.maxDatagramSize-p.budgetAtLastSent)*1e9/float64(p.getAdjustedBandwidth())))*time.Nanosecond,
 	))