net/http: introduce DialerAndTLSConfigSupportsHTTP2 in Transport

Even when a custom TLS config or custom dialer is specified, enables HTTP/2 if DialerAndTLSConfigSupportsHTTP2 is true. By this change, avoid automatically enabling HTTP/2 if DialContext is set. This change also ensures that DefaultTransport still automatically enable HTTP/2 as discussed in #14391. Updates #14391 Fixes #27011 Change-Id: Icc46416810bee61dbd65ebc96468335030b80573 Reviewed-on: https://go-review.googlesource.com/c/go/+/130256 Reviewed-by: Brad Fitzpatrick <[email protected]> Run-TryBot: Brad Fitzpatrick <[email protected]> Run-TryBot: Kunpei Sakai <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>
golang · Apr 16, 2019 · 94e7200 · 94e7200
1 parent 1eed2a5
commit 94e7200
Show file tree

Hide file tree

Showing 2 changed files with 27 additions and 5 deletions.
diff --git a/src/net/http/transport.go b/src/net/http/transport.go
@@ -46,10 +46,11 @@ var DefaultTransport RoundTripper = &Transport{
 		KeepAlive: 30 * time.Second,
 		DualStack: true,
 	}).DialContext,
-	MaxIdleConns:          100,
-	IdleConnTimeout:       90 * time.Second,
-	TLSHandshakeTimeout:   10 * time.Second,
-	ExpectContinueTimeout: 1 * time.Second,
+	DialerAndTLSConfigSupportsHTTP2: true,
+	MaxIdleConns:                    100,
+	IdleConnTimeout:                 90 * time.Second,
+	TLSHandshakeTimeout:             10 * time.Second,
+	ExpectContinueTimeout:           1 * time.Second,
 }
 
 // DefaultMaxIdleConnsPerHost is the default value of Transport's
@@ -257,6 +258,12 @@ type Transport struct {
 	// h2transport (via onceSetNextProtoDefaults)
 	nextProtoOnce sync.Once
 	h2transport   h2Transport // non-nil if http2 wired up
+
+	// DialerAndTLSConfigSupportsHTTP2 controls whether HTTP/2 is enabled when a non-zero
+	// TLSClientConfig or Dial, DialTLS or DialContext func is provided. By default, use of any those fields conservatively
+	// disables HTTP/2. To use a customer dialer or TLS config and still attempt HTTP/2
+	// upgrades, set this to true.
+	DialerAndTLSConfigSupportsHTTP2 bool
 }
 
 // h2Transport is the interface we expect to be able to call from
@@ -296,12 +303,13 @@ func (t *Transport) onceSetNextProtoDefaults() {
 		// Transport.
 		return
 	}
-	if t.TLSClientConfig != nil || t.Dial != nil || t.DialTLS != nil {
+	if !t.DialerAndTLSConfigSupportsHTTP2 && (t.TLSClientConfig != nil || t.Dial != nil || t.DialTLS != nil || t.DialContext != nil) {
 		// Be conservative and don't automatically enable
 		// http2 if they've specified a custom TLS config or
 		// custom dialers. Let them opt-in themselves via
 		// http2.ConfigureTransport so we don't surprise them
 		// by modifying their tls.Config. Issue 14275.
+		// However, if DialerAndTLSConfigSupportsHTTP2 is true, it overrides the above checks.
 		return
 	}
 	t2, err := http2configureTransport(t)

diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
@@ -3593,6 +3593,13 @@ func TestTransportAutomaticHTTP2(t *testing.T) {
 	testTransportAutoHTTP(t, &Transport{}, true)
 }
 
+func TestTransportAutomaticHTTP2_DialerAndTLSConfigSupportsHTTP2AndTLSConfig(t *testing.T) {
+	testTransportAutoHTTP(t, &Transport{
+		DialerAndTLSConfigSupportsHTTP2: true,
+		TLSClientConfig:                 new(tls.Config),
+	}, true)
+}
+
 // golang.org/issue/14391: also check DefaultTransport
 func TestTransportAutomaticHTTP2_DefaultTransport(t *testing.T) {
 	testTransportAutoHTTP(t, DefaultTransport.(*Transport), true)
@@ -3623,6 +3630,13 @@ func TestTransportAutomaticHTTP2_Dial(t *testing.T) {
 	}, false)
 }
 
+func TestTransportAutomaticHTTP2_DialContext(t *testing.T) {
+	var d net.Dialer
+	testTransportAutoHTTP(t, &Transport{
+		DialContext: d.DialContext,
+	}, false)
+}
+
 func TestTransportAutomaticHTTP2_DialTLS(t *testing.T) {
 	testTransportAutoHTTP(t, &Transport{
 		DialTLS: func(network, addr string) (net.Conn, error) {