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calculate correct MinLength of an ACK frame with a contiguous NACK range

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fixes #183
This commit is contained in:
Marten Seemann
2016-06-20 14:43:00 +07:00
parent 29029978a0
commit 433920fc15
2 changed files with 29 additions and 13 deletions
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29
frames/ack_frame.go
View File

@@ -58,20 +58,10 @@ func (f *AckFrame) Write(b *bytes.Buffer, version protocol.VersionNumber) error
utils.WriteUint32(b, 0) // First timestamp
if f.HasNACK() {
numRanges := uint64(0)
// calculate the number of NackRanges that are about to be written
// this number is different from len(f.NackRanges) for the case of contiguous NACK ranges
for _, nackRange := range f.NackRanges {
rangeLength := nackRange.Len()
numRanges += rangeLength/0xFF + 1
if rangeLength > 0 && rangeLength%0xFF == 0 {
numRanges--
}
}
numRanges := f.numWrittenNackRanges()
if numRanges > 0xFF {
panic("Too many NACK ranges. Truncating not yet implemented.")
}
b.WriteByte(uint8(numRanges))
rangeCounter := uint8(0)
@@ -120,7 +110,7 @@ func (f *AckFrame) MinLength(version protocol.VersionNumber) (protocol.ByteCount
l += int(protocol.GetPacketNumberLength(f.LargestObserved))
l += (1 + 2) * 0 /* TODO: num_timestamps */
if f.HasNACK() {
l += 1 + (6+1)*len(f.NackRanges)
l += 1 + (6+1)*int(f.numWrittenNackRanges())
l++ // TODO: Remove once we drop support for <32
}
return protocol.ByteCount(l), nil
@@ -288,6 +278,21 @@ func ParseAckFrame(r *bytes.Reader, version protocol.VersionNumber) (*AckFrame,
return frame, nil
}
// numWrittenNackRanges calculates the number of NackRanges that are about to be written
// this number is different from len(f.NackRanges) for the case of contiguous NACK ranges
func (f *AckFrame) numWrittenNackRanges() uint64 {
var numRanges uint64
for _, nackRange := range f.NackRanges {
rangeLength := nackRange.Len()
numRanges += rangeLength/0xFF + 1
if rangeLength > 0 && rangeLength%0xFF == 0 {
numRanges--
}
}
return numRanges
}
func (f *AckFrame) validateNackRanges() bool {
// check the validity of every single NACK range
for _, nackRange := range f.NackRanges {

13
frames/ack_frame_test.go
View File

@@ -512,7 +512,7 @@ var _ = Describe("AckFrame", func() {
Expect(f.MinLength(0)).To(Equal(protocol.ByteCount(b.Len())))
})
It("has proper min length with nack ranges", func() {
It("has proper min length with NACK ranges", func() {
f := &AckFrame{
Entropy: 2,
LargestObserved: 4,
@@ -522,6 +522,17 @@ var _ = Describe("AckFrame", func() {
Expect(err).ToNot(HaveOccurred())
Expect(f.MinLength(0)).To(Equal(protocol.ByteCount(b.Len())))
})
It("has proper min length with a continuous NACK ranges", func() {
f := &AckFrame{
Entropy: 2,
LargestObserved: 3000,
NackRanges: []NackRange{{FirstPacketNumber: 2, LastPacketNumber: 2000}},
}
err := f.Write(b, protocol.Version31)
Expect(err).ToNot(HaveOccurred())
Expect(f.MinLength(0)).To(Equal(protocol.ByteCount(b.Len())))
})
})
})