From e4fc732d37be1d8326b4b4b2c759aa283ca22d59 Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Wed, 27 Apr 2016 09:46:13 +0700
Subject: [PATCH] only increase packet number in PacketPacker when actually
 sending a packet

---
 packet_packer.go      | 10 +++++-----
 packet_packer_test.go | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/packet_packer.go b/packet_packer.go
index 2ed308c0..1618f56c 100644
--- a/packet_packer.go
+++ b/packet_packer.go
@@ -39,11 +39,6 @@ func (p *packetPacker) PackPacket(controlFrames []frames.Frame, includeStreamFra
 	p.mutex.Lock()
 	defer p.mutex.Unlock() // TODO: Split up?
 
-	currentPacketNumber := protocol.PacketNumber(atomic.AddUint64(
-		(*uint64)(&p.lastPacketNumber),
-		1,
-	))
-
 	payloadFrames, err := p.composeNextPacket(controlFrames, includeStreamFrames)
 	if err != nil {
 		return nil, err
@@ -53,6 +48,11 @@ func (p *packetPacker) PackPacket(controlFrames []frames.Frame, includeStreamFra
 		return nil, nil
 	}
 
+	currentPacketNumber := protocol.PacketNumber(atomic.AddUint64(
+		(*uint64)(&p.lastPacketNumber),
+		1,
+	))
+
 	payload, err := p.getPayload(payloadFrames, currentPacketNumber)
 	if err != nil {
 		return nil, err
diff --git a/packet_packer_test.go b/packet_packer_test.go
index d4e15dd4..94a0a31e 100644
--- a/packet_packer_test.go
+++ b/packet_packer_test.go
@@ -99,6 +99,27 @@ var _ = Describe("Packet packer", func() {
 	// 	Expect(len(payloadFrames)).To(Equal(counter - maxFramesPerPacket))
 	// })
 
+	It("only increases the packet number when there is an actual packet to send", func() {
+		f := frames.StreamFrame{
+			StreamID: 5,
+			Data:     []byte{0xDE, 0xCA, 0xFB, 0xAD},
+		}
+		packer.AddStreamFrame(f)
+		p, err := packer.PackPacket([]frames.Frame{}, true)
+		Expect(p).ToNot(BeNil())
+		Expect(err).ToNot(HaveOccurred())
+		Expect(packer.lastPacketNumber).To(Equal(protocol.PacketNumber(1)))
+		p, err = packer.PackPacket([]frames.Frame{}, true)
+		Expect(p).To(BeNil())
+		Expect(err).ToNot(HaveOccurred())
+		Expect(packer.lastPacketNumber).To(Equal(protocol.PacketNumber(1)))
+		packer.AddStreamFrame(f)
+		p, err = packer.PackPacket([]frames.Frame{}, true)
+		Expect(p).ToNot(BeNil())
+		Expect(err).ToNot(HaveOccurred())
+		Expect(packer.lastPacketNumber).To(Equal(protocol.PacketNumber(2)))
+	})
+
 	Context("Stream Frame handling", func() {
 		It("does not splits a stream frame with maximum size", func() {
 			maxStreamFrameDataLen := protocol.MaxFrameSize - (1 + 4 + 8 + 2)