From fe45644335ae9869c23d4b07ffd4dd55ca06a345 Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Sat, 11 Jun 2016 11:14:19 +0700
Subject: [PATCH] don't write private header for QUIC Version >= 34

ref #55
---
 packet_packer.go      | 24 +++++++++++++++++-------
 packet_packer_test.go | 23 +++++++++++++++++++++++
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/packet_packer.go b/packet_packer.go
index 441981e2..69da8164 100644
--- a/packet_packer.go
+++ b/packet_packer.go
@@ -127,12 +127,16 @@ func (p *packetPacker) packPacket(stopWaitingFrame *frames.StopWaitingFrame, con
 		return nil, err
 	}
 
-	entropyBit, err := utils.RandomBit()
-	if err != nil {
-		return nil, err
-	}
-	if entropyBit {
-		payload[0] = 1
+	// set entropy bit in Private Header, for QUIC version < 34
+	var entropyBit bool
+	if p.version < protocol.Version34 {
+		entropyBit, err = utils.RandomBit()
+		if err != nil {
+			return nil, err
+		}
+		if entropyBit {
+			payload[0] = 1
+		}
 	}
 
 	var raw bytes.Buffer
@@ -157,7 +161,13 @@ func (p *packetPacker) packPacket(stopWaitingFrame *frames.StopWaitingFrame, con
 
 func (p *packetPacker) getPayload(frames []frames.Frame, currentPacketNumber protocol.PacketNumber) ([]byte, error) {
 	var payload bytes.Buffer
-	payload.WriteByte(0) // The entropy bit is set in sendPayload
+
+	// reserve 1 byte for the Private Header, for QUIC Version < 34
+	// the entropy bit is set in sendPayload
+	if p.version < protocol.Version34 {
+		payload.WriteByte(0)
+	}
+
 	for _, frame := range frames {
 		frame.Write(&payload, p.version)
 	}
diff --git a/packet_packer_test.go b/packet_packer_test.go
index 05675371..96bde5ce 100644
--- a/packet_packer_test.go
+++ b/packet_packer_test.go
@@ -68,6 +68,29 @@ var _ = Describe("Packet packer", func() {
 		Expect(err).ToNot(HaveOccurred())
 	})
 
+	It("doesn't set a private header for QUIC version >= 34", func() {
+		// This is not trivial to test, since PackPacket() already encrypts the packet
+		// So pack the packet for QUIC 33, then for QUIC 34. The packet for QUIC 33 should be 1 byte longer, since it contains the Private Header
+		f := frames.StreamFrame{
+			StreamID: 5,
+			Data:     []byte("foobar"),
+		}
+		// pack the packet for QUIC version 33
+		packer.version = protocol.Version33
+		packer.AddStreamFrame(f)
+		p33, err := packer.PackPacket(nil, []frames.Frame{})
+		Expect(err).ToNot(HaveOccurred())
+		Expect(p33).ToNot(BeNil())
+		// pack the packet for QUIC version 34
+		packer.version = protocol.Version34
+		packer.AddStreamFrame(f)
+		p34, err := packer.PackPacket(nil, []frames.Frame{})
+		Expect(err).ToNot(HaveOccurred())
+		Expect(p34).ToNot(BeNil())
+		Expect(p34.entropyBit).To(BeFalse())
+		Expect(p34.raw).To(HaveLen(len(p33.raw) - 1))
+	})
+
 	It("packs single packets", func() {
 		f := frames.StreamFrame{
 			StreamID: 5,