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 <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Kunpei Sakai <namusyaka@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index de1fb96818331fae1d7969266e2496a7e63fe7ea..88dbfe7c6e7226c7a912522dbf8b203d28a98171 100644 (file)
--- 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
index 23864a4957932d72dd0030bebc76ccf3534fe260..789d52c5d5cb3ad5f9877c7eb498e26e7707d5d5 100644 (file)
--- 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) {