net/http: add HTTP2Config

Add a field to Server and Transport containing HTTP/2 configuration
parameters.

This field will have no effect until golang.org/x/net/http2 is updated
to make use of it, and h2_bundle.go is updated with the new http2
package.

For #67813

Change-Id: I81d7f8e9ddea78f9666383983aec43e3884c13ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/602175
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>

api/next/67813.txt

@@ -0,0 +1,14 @@
+pkg net/http, type HTTP2Config struct #67813
+pkg net/http, type HTTP2Config struct, CountError func(string) #67813
+pkg net/http, type HTTP2Config struct, MaxConcurrentStreams int #67813
+pkg net/http, type HTTP2Config struct, MaxDecoderHeaderTableSize int #67813
+pkg net/http, type HTTP2Config struct, MaxEncoderHeaderTableSize int #67813
+pkg net/http, type HTTP2Config struct, MaxReadFrameSize int #67813
+pkg net/http, type HTTP2Config struct, MaxReceiveBufferPerConnection int #67813
+pkg net/http, type HTTP2Config struct, MaxReceiveBufferPerStream int #67813
+pkg net/http, type HTTP2Config struct, PermitProhibitedCipherSuites bool #67813
+pkg net/http, type HTTP2Config struct, PingTimeout time.Duration #67813
+pkg net/http, type HTTP2Config struct, SendPingTimeout time.Duration #67813
+pkg net/http, type HTTP2Config struct, WriteByteTimeout time.Duration #67813
+pkg net/http, type Server struct, HTTP2 *HTTP2Config #67813
+pkg net/http, type Transport struct, HTTP2 *HTTP2Config #67813

doc/next/6-stdlib/99-minor/net/http/67813.md

@@ -0,0 +1,2 @@
+[Transport] and [Server] now have an HTTP2 field which permits
+configuring HTTP/2 protocol settings.

src/net/http/http.go

@@ -163,3 +163,68 @@ type Pusher interface {
 	// is not supported on the underlying connection.
 	Push(target string, opts *PushOptions) error
 }
+
+// HTTP2Config defines HTTP/2 configuration parameters common to
+// both [Transport] and [Server].
+type HTTP2Config struct {
+	// MaxConcurrentStreams optionally specifies the number of
+	// concurrent streams that a peer may have open at a time.
+	// If zero, MaxConcurrentStreams defaults to at least 100.
+	MaxConcurrentStreams int
+
+	// MaxDecoderHeaderTableSize optionally specifies an upper limit for the
+	// size of the header compression table used for decoding headers sent
+	// by the peer.
+	// A valid value is less than 4MiB.
+	// If zero or invalid, a default value is used.
+	MaxDecoderHeaderTableSize int
+
+	// MaxEncoderHeaderTableSize optionally specifies an upper limit for the
+	// header compression table used for sending headers to the peer.
+	// A valid value is less than 4MiB.
+	// If zero or invalid, a default value is used.
+	MaxEncoderHeaderTableSize int
+
+	// MaxReadFrameSize optionally specifies the largest frame
+	// this endpoint is willing to read.
+	// A valid value is between 16KiB and 16MiB, inclusive.
+	// If zero or invalid, a default value is used.
+	MaxReadFrameSize int
+
+	// MaxReceiveBufferPerConnection is the maximum size of the
+	// flow control window for data received on a connection.
+	// A valid value is at least 64KiB and less than 4MiB.
+	// If invalid, a default value is used.
+	MaxReceiveBufferPerConnection int
+
+	// MaxReceiveBufferPerStream is the maximum size of
+	// the flow control window for data received on a stream (request).
+	// A valid value is less than 4MiB.
+	// If zero or invalid, a default value is used.
+	MaxReceiveBufferPerStream int
+
+	// SendPingTimeout is the timeout after which a health check using a ping
+	// frame will be carried out if no frame is received on a connection.
+	// If zero, no health check is performed.
+	SendPingTimeout time.Duration
+
+	// PingTimeout is the timeout after which a connection will be closed
+	// if a response to a ping is not received.
+	// If zero, a default of 15 seconds is used.
+	PingTimeout time.Duration
+
+	// WriteByteTimeout is the timeout after which a connection will be
+	// closed if no data can be written to it. The timeout begins when data is
+	// available to write, and is extended whenever any bytes are written.
+	WriteByteTimeout time.Duration
+
+	// PermitProhibitedCipherSuites, if true, permits the use of
+	// cipher suites prohibited by the HTTP/2 spec.
+	PermitProhibitedCipherSuites bool
+
+	// CountError, if non-nil, is called on HTTP/2 errors.
+	// It is intended to increment a metric for monitoring.
+	// The errType contains only lowercase letters, digits, and underscores
+	// (a-z, 0-9, _).
+	CountError func(errType string)
+}

src/net/http/server.go

@@ -2973,6 +2973,12 @@ type Server struct {
 	// value.
 	ConnContext func(ctx context.Context, c net.Conn) context.Context
 
+	// HTTP2 configures HTTP/2 connections.
+	//
+	// This field does not yet have any effect.
+	// See https://go.dev/issue/67813.
+	HTTP2 *HTTP2Config
+
 	inShutdown atomic.Bool // true when server is in shutdown
 
 	disableKeepAlives atomic.Bool

src/net/http/transport.go

@@ -293,6 +293,12 @@ type Transport struct {
 	// To use a custom dialer or TLS config and still attempt HTTP/2
 	// upgrades, set this to true.
 	ForceAttemptHTTP2 bool
+
+	// HTTP2 configures HTTP/2 connections.
+	//
+	// This field does not yet have any effect.
+	// See https://go.dev/issue/67813.
+	HTTP2 *HTTP2Config
 }
 
 func (t *Transport) writeBufferSize() int {
@@ -338,6 +344,10 @@ func (t *Transport) Clone() *Transport {
 	if t.TLSClientConfig != nil {
 		t2.TLSClientConfig = t.TLSClientConfig.Clone()
 	}
+	if t.HTTP2 != nil {
+		t2.HTTP2 = &HTTP2Config{}
+		*t2.HTTP2 = *t.HTTP2
+	}
 	if !t.tlsNextProtoWasNil {
 		npm := map[string]func(authority string, c *tls.Conn) RoundTripper{}
 		for k, v := range t.TLSNextProto {

src/net/http/transport_test.go

@@ -6328,6 +6328,7 @@ func TestTransportClone(t *testing.T) {
 		GetProxyConnectHeader:  func(context.Context, *url.URL, string) (Header, error) { return nil, nil },
 		MaxResponseHeaderBytes: 1,
 		ForceAttemptHTTP2:      true,
+		HTTP2:                  &HTTP2Config{MaxConcurrentStreams: 1},
 		TLSNextProto: map[string]func(authority string, c *tls.Conn) RoundTripper{
 			"foo": func(authority string, c *tls.Conn) RoundTripper { panic("") },
 		},