From 0b0cb7c06f2fc534395ca3067b6c2d9aca38baa1 Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Mon, 21 Dec 2020 11:16:41 +0700
Subject: [PATCH] add a http3.Server.EnableDatagram option

---
 http3/server.go      | 22 ++++++++++++++++++----
 http3/server_test.go | 11 +++++++++++
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/http3/server.go b/http3/server.go
index 4a745d770..bd30b2dc1 100644
--- a/http3/server.go
+++ b/http3/server.go
@@ -89,6 +89,11 @@ type Server struct {
 	// If nil, it uses reasonable default values.
 	QuicConfig *quic.Config
 
+	// Enable support for HTTP/3 datagrams.
+	// If set to true, QuicConfig.EnableDatagram will be set.
+	// See https://www.ietf.org/archive/id/draft-schinazi-masque-h3-datagram-02.html.
+	EnableDatagrams bool
+
 	port uint32 // used atomically
 
 	mutex     sync.Mutex
@@ -173,10 +178,19 @@ func (s *Server) serveImpl(tlsConf *tls.Config, conn net.PacketConn) error {
 
 	var ln quic.EarlyListener
 	var err error
-	if conn == nil {
-		ln, err = quicListenAddr(s.Addr, baseConf, s.QuicConfig)
+	quicConf := s.QuicConfig
+	if quicConf == nil {
+		quicConf = &quic.Config{}
 	} else {
-		ln, err = quicListen(conn, baseConf, s.QuicConfig)
+		quicConf = s.QuicConfig.Clone()
+	}
+	if s.EnableDatagrams {
+		quicConf.EnableDatagrams = true
+	}
+	if conn == nil {
+		ln, err = quicListenAddr(s.Addr, baseConf, quicConf)
+	} else {
+		ln, err = quicListen(conn, baseConf, quicConf)
 	}
 	if err != nil {
 		return err
@@ -223,7 +237,7 @@ func (s *Server) handleConn(sess quic.EarlySession) {
 	}
 	buf := &bytes.Buffer{}
 	utils.WriteVarInt(buf, streamTypeControlStream) // stream type
-	(&settingsFrame{}).Write(buf)
+	(&settingsFrame{Datagram: s.EnableDatagrams}).Write(buf)
 	str.Write(buf.Bytes())
 
 	go s.handleUnidirectionalStreams(sess)
diff --git a/http3/server_test.go b/http3/server_test.go
index 0e0983ffa..89fe0ecb8 100644
--- a/http3/server_test.go
+++ b/http3/server_test.go
@@ -775,4 +775,15 @@ var _ = Describe("Server", func() {
 		fullpem, privkey := testdata.GetCertificatePaths()
 		Expect(ListenAndServeQUIC("", fullpem, privkey, nil)).To(MatchError(testErr))
 	})
+
+	It("supports H3_DATAGRAM", func() {
+		s.EnableDatagrams = true
+		var receivedConf *quic.Config
+		quicListenAddr = func(addr string, _ *tls.Config, config *quic.Config) (quic.EarlyListener, error) {
+			receivedConf = config
+			return nil, errors.New("listen err")
+		}
+		Expect(s.ListenAndServe()).To(HaveOccurred())
+		Expect(receivedConf.EnableDatagrams).To(BeTrue())
+	})
 })