From fc3087fab3017172437c1d29530f9dd5795159d2 Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Sun, 29 Oct 2017 16:44:03 +0700
Subject: [PATCH] handle IETF draft style Version Negotiation Packets

---
 client.go      | 29 ++++++++++++++++-------------
 client_test.go |  1 +
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/client.go b/client.go
index ca56ce43..d3b21dc2 100644
--- a/client.go
+++ b/client.go
@@ -286,26 +286,29 @@ func (c *client) handlePacket(remoteAddr net.Addr, packet []byte) {
 		return
 	}
 
-	// ignore delayed / duplicated version negotiation packets
-	if (c.receivedVersionNegotiationPacket || c.versionNegotiated) && hdr.VersionFlag {
-		return
-	}
+	isVersionNegotiationPacket := hdr.VersionFlag /* gQUIC Version Negotiation Packet */ || hdr.Type == protocol.PacketTypeVersionNegotiation /* IETF draft style Version Negotiation Packet */
 
-	// this is the first packet after the client sent a packet with the VersionFlag set
-	// if the server doesn't send a version negotiation packet, it supports the suggested version
-	if !hdr.VersionFlag && !c.versionNegotiated {
-		c.versionNegotiated = true
-		close(c.versionNegotiationChan)
-	}
+	// handle Version Negotiation Packets
+	if isVersionNegotiationPacket {
+		// ignore delayed / duplicated version negotiation packets
+		if c.receivedVersionNegotiationPacket || c.versionNegotiated {
+			return
+		}
 
-	if hdr.VersionFlag {
 		// version negotiation packets have no payload
-		if err := c.handlePacketWithVersionFlag(hdr); err != nil {
+		if err := c.handleVersionNegotiationPacket(hdr); err != nil {
 			c.session.Close(err)
 		}
 		return
 	}
 
+	// this is the first packet we are receiving
+	// since it is not a Version Negotiation Packet, this means the server supports the suggested version
+	if !c.versionNegotiated {
+		c.versionNegotiated = true
+		close(c.versionNegotiationChan)
+	}
+
 	c.session.handlePacket(&receivedPacket{
 		remoteAddr: remoteAddr,
 		header:     hdr,
@@ -314,7 +317,7 @@ func (c *client) handlePacket(remoteAddr net.Addr, packet []byte) {
 	})
 }
 
-func (c *client) handlePacketWithVersionFlag(hdr *wire.Header) error {
+func (c *client) handleVersionNegotiationPacket(hdr *wire.Header) error {
 	for _, v := range hdr.SupportedVersions {
 		if v == c.version {
 			// the version negotiation packet contains the version that we offered
diff --git a/client_test.go b/client_test.go
index 1d8e1aa5..0f438f8d 100644
--- a/client_test.go
+++ b/client_test.go
@@ -246,6 +246,7 @@ var _ = Describe("Client", func() {
 			testErr := errors.New("late handshake error")
 			packetConn.dataToRead = acceptClientVersionPacket(cl.connectionID)
 			go func() {
+				defer GinkgoRecover()
 				_, dialErr := Dial(packetConn, addr, "quic.clemente.io:1337", nil, config)
 				Expect(dialErr).To(MatchError(testErr))
 				close(done)