chore: update quic congestion pacer

transport/tuic/congestion_v2/pacer.go

@@ -1,7 +1,6 @@
 package congestion
 
 import (
-	"math"
 	"time"
 
 	"github.com/metacubex/quic-go/congestion"
@@ -9,7 +8,8 @@ import (
 )
 
 const (
-	maxBurstPackets = 10
+	maxBurstPackets               = 10
+	maxBurstPacingDelayMultiplier = 4
 )
 
 // Pacer implements a token bucket pacing algorithm.
@@ -52,22 +52,27 @@ func (p *Pacer) Budget(now monotime.Time) congestion.ByteCount {
 
 func (p *Pacer) maxBurstSize() congestion.ByteCount {
 	return Max(
-		congestion.ByteCount((congestion.MinPacingDelay+time.Millisecond).Nanoseconds())*p.getBandwidth()/1e9,
+		congestion.ByteCount((maxBurstPacingDelayMultiplier*congestion.MinPacingDelay).Nanoseconds())*p.getBandwidth()/1e9,
 		maxBurstPackets*p.maxDatagramSize,
 	)
 }
 
 // TimeUntilSend returns when the next packet should be sent.
-// It returns the zero value of monotime.Time if a packet can be sent immediately.
+// It returns the zero value if a packet can be sent immediately.
 func (p *Pacer) TimeUntilSend() monotime.Time {
 	if p.budgetAtLastSent >= p.maxDatagramSize {
-		return monotime.Time(0)
+		return 0
 	}
-	return p.lastSentTime.Add(Max(
-		congestion.MinPacingDelay,
-		time.Duration(math.Ceil(float64(p.maxDatagramSize-p.budgetAtLastSent)*1e9/
-			float64(p.getBandwidth())))*time.Nanosecond,
-	))
+	diff := 1e9 * uint64(p.maxDatagramSize-p.budgetAtLastSent)
+	bw := uint64(p.getBandwidth())
+	// We might need to round up this value.
+	// Otherwise, we might have a budget (slightly) smaller than the datagram size when the timer expires.
+	d := diff / bw
+	// this is effectively a math.Ceil, but using only integer math
+	if diff%bw > 0 {
+		d++
+	}
+	return p.lastSentTime.Add(Max(congestion.MinPacingDelay, time.Duration(d)*time.Nanosecond))
 }
 
 func (p *Pacer) SetMaxDatagramSize(s congestion.ByteCount) {

transport/tuic/congestion_v2/packet_number_indexed_queue.go

@@ -152,7 +152,7 @@ func (p *packetNumberIndexedQueue[T]) EntrySlotsUsed() int {
 	return p.entries.Len()
 }
 
-// LastPacket returns packet number of the first entry in the queue.
+// FirstPacket returns packet number of the first entry in the queue.
 func (p *packetNumberIndexedQueue[T]) FirstPacket() (packetNumber congestion.PacketNumber) {
 	return p.firstPacket
 }