Fix Xmittime

Author: chenchun

class_linux.go

@@ -43,12 +43,12 @@ func NewHtbClass(attrs ClassAttrs, cattrs HtbClassAttrs) *HtbClass {
 	if buffer == 0 {
 		buffer = uint32(float64(rate)/Hz() + float64(mtu))
 	}
-	buffer = uint32(Xmittime(rate, buffer))
+	buffer = Xmittime(rate, buffer)
 
 	if cbuffer == 0 {
 		cbuffer = uint32(float64(ceil)/Hz() + float64(mtu))
 	}
-	cbuffer = uint32(Xmittime(ceil, cbuffer))
+	cbuffer = Xmittime(ceil, cbuffer)
 
 	return &HtbClass{
 		ClassAttrs: attrs,

filter_linux.go

@@ -89,7 +89,7 @@ func NewFw(attrs FilterAttrs, fattrs FilterFwAttrs) (*Fw, error) {
 		if CalcRtable(&police.Rate, rtab[:], rcellLog, fattrs.Mtu, linklayer) < 0 {
 			return nil, errors.New("TBF: failed to calculate rate table")
 		}
-		police.Burst = uint32(Xmittime(uint64(police.Rate.Rate), uint32(buffer)))
+		police.Burst = Xmittime(uint64(police.Rate.Rate), uint32(buffer))
 	}
 	police.Mtu = fattrs.Mtu
 	if police.PeakRate.Rate != 0 {
@@ -783,7 +783,7 @@ func CalcRtable(rate *nl.TcRateSpec, rtab []uint32, cellLog int, mtu uint32, lin
 	}
 	for i := 0; i < 256; i++ {
 		sz = AdjustSize(uint((i+1)<<uint32(cellLog)), uint(mpu), linklayer)
-		rtab[i] = uint32(Xmittime(uint64(bps), uint32(sz)))
+		rtab[i] = Xmittime(uint64(bps), uint32(sz))
 	}
 	rate.CellAlign = -1
 	rate.CellLog = uint8(cellLog)

qdisc_linux.go

@@ -668,6 +668,7 @@ func latency(rate uint64, limit, buffer uint32) float64 {
 	return TIME_UNITS_PER_SEC*(float64(limit)/float64(rate)) - float64(tick2Time(buffer))
 }
 
-func Xmittime(rate uint64, size uint32) float64 {
-	return TickInUsec() * TIME_UNITS_PER_SEC * (float64(size) / float64(rate))
+func Xmittime(rate uint64, size uint32) uint32 {
+	// https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/tree/tc/tc_core.c#n62
+	return time2Tick(uint32(TIME_UNITS_PER_SEC * (float64(size) / float64(rate))))
 }