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omit the data length in the last STREAM frame of a retransmission

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This commit is contained in:
Marten Seemann 2018-02-26 21:59:45 +08:00
parent ca7291e8cf
commit a1c9e706b0
2 changed files with 41 additions and 1 deletions
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17
packet_packer.go
View file

@ -157,10 +157,22 @@ func (p *packetPacker) PackRetransmission(packet *ackhandler.Packet) ([]*packedP
frames = append(frames, frame)
controlFrames = controlFrames[1:]
}
// temporarily increase the maxFrameSize by the (minimum) length of the DataLen field
// this leads to a properly sized packet in all cases, since we do all the packet length calculations with StreamFrames that have the DataLen set
// however, for the last STREAM frame in the packet, we can omit the DataLen, thus yielding a packet of exactly the correct size
// for gQUIC STREAM frames, DataLen is always 2 bytes
// for IETF draft style STREAM frames, the length is encoded to either 1 or 2 bytes
if p.version.UsesIETFFrameFormat() {
maxSize++
} else {
maxSize += 2
}
for len(streamFrames) > 0 && payloadLength+protocol.MinStreamFrameSize < maxSize {
// TODO: optimize by setting DataLenPresent = false on all but the last STREAM frame
frame := streamFrames[0]
frameToAdd := frame
sf, err := frame.MaybeSplitOffFrame(maxSize-payloadLength, p.version)
if err != nil {
return nil, err
@ -173,6 +185,9 @@ func (p *packetPacker) PackRetransmission(packet *ackhandler.Packet) ([]*packedP
payloadLength += frameToAdd.Length(p.version)
frames = append(frames, frameToAdd)
}
if sf, ok := frames[len(frames)-1].(*wire.StreamFrame); ok {
sf.DataLenPresent = false
}
raw, err := p.writeAndSealPacket(header, frames, sealer)
if err != nil {
return nil, err
@ -351,7 +366,7 @@ func (p *packetPacker) composeNextPacket(
// temporarily increase the maxFrameSize by the (minimum) length of the DataLen field
// this leads to a properly sized packet in all cases, since we do all the packet length calculations with StreamFrames that have the DataLen set
// however, for the last StreamFrame in the packet, we can omit the DataLen, thus yielding a packet of exactly the correct size
// however, for the last STREAM frame in the packet, we can omit the DataLen, thus yielding a packet of exactly the correct size
// for gQUIC STREAM frames, DataLen is always 2 bytes
// for IETF draft style STREAM frames, the length is encoded to either 1 or 2 bytes
if p.version.UsesIETFFrameFormat() {

25
packet_packer_test.go
View file

@ -809,8 +809,10 @@ var _ = Describe("Packet packer", func() {
sf2 := packets[1].frames[1].(*wire.StreamFrame)
Expect(sf1.StreamID).To(Equal(protocol.StreamID(42)))
Expect(sf1.Offset).To(Equal(protocol.ByteCount(1337)))
Expect(sf1.DataLenPresent).To(BeFalse())
Expect(sf2.StreamID).To(Equal(protocol.StreamID(42)))
Expect(sf2.Offset).To(Equal(protocol.ByteCount(1337) + sf1.DataLen()))
Expect(sf2.DataLenPresent).To(BeFalse())
Expect(sf1.DataLen() + sf2.DataLen()).To(Equal(protocol.MaxPacketSize * 3 / 2))
Expect(packets[0].raw).To(HaveLen(int(protocol.MaxPacketSize)))
})
@ -844,6 +846,29 @@ var _ = Describe("Packet packer", func() {
Expect(len(packets[0].raw) + int(packets[1].frames[1].Length(packer.version))).To(BeNumerically(">", protocol.MaxPacketSize-protocol.MinStreamFrameSize))
})
It("correctly sets the DataLenPresent on STREAM frames", func() {
frames := []wire.Frame{
&wire.StreamFrame{StreamID: 4, Data: []byte("foobar"), DataLenPresent: true},
&wire.StreamFrame{StreamID: 5, Data: []byte("barfoo")},
}
packets, err := packer.PackRetransmission(&ackhandler.Packet{
EncryptionLevel: protocol.EncryptionForwardSecure,
Frames: frames,
})
Expect(err).ToNot(HaveOccurred())
Expect(packets).To(HaveLen(1))
p := packets[0]
Expect(p.frames).To(HaveLen(3))
Expect(p.frames[1]).To(BeAssignableToTypeOf(&wire.StreamFrame{}))
Expect(p.frames[2]).To(BeAssignableToTypeOf(&wire.StreamFrame{}))
sf1 := p.frames[1].(*wire.StreamFrame)
sf2 := p.frames[2].(*wire.StreamFrame)
Expect(sf1.StreamID).To(Equal(protocol.StreamID(4)))
Expect(sf1.DataLenPresent).To(BeTrue())
Expect(sf2.StreamID).To(Equal(protocol.StreamID(5)))
Expect(sf2.DataLenPresent).To(BeFalse())
})
})
Context("packing ACK packets", func() {